@article{perez_mullen_canter_ley_may_2020, title={Phenotypic diversity in an emerging mycoplasmal disease}, volume={138}, ISSN={["0882-4010"]}, DOI={10.1016/j.micpath.2019.103798}, abstractNote={The avian pathogen Mycoplasma gallisepticum (MG) is a known pathogen of poultry, and newly emerged pathogen of house finches wherein it is associated with lethal conjunctivitis. Factors present in MG that are known to mediate virulence include cytadherence, sialidase activity, peroxide production, and biofilm formation. We have quantitatively assessed these factors for MG isolates from house finches from a temporal and geographic distribution across the continental United States that show differing capacity for virulence in vivo. Statistically significant (P < 0.05) differences were observed across strains for sialidase activity, cytadherence, and hydrogen peroxide production. Sialidase activity increased over time in geographically static populations, but did not correlate with time overall. All strains were able to bind α-2,6-linked sialic acid. No strains were found to bind α-2,3-linked sialic acid. All strains produced biofilms in vitro; however, no significant differences were observed in the density of biofilms across strains. Quantitative variance in virulence-associated traits is consistent with within-host evolutionary adaptation in response to a change in ecological niche by a parasitic pathogen.}, journal={MICROBIAL PATHOGENESIS}, author={Perez, Kailey and Mullen, Nathan and Canter, Jessica A. and Ley, David H. and May, Meghan}, year={2020}, month={Jan} }
 @article{rogers_ley_woods_2019, title={Mycoplasmosis of House Finches (Haemorhous mexicanus) and California Scrub-Jays (Aphelocoma californica) in a Wildlife Rehabilitation Facility with Probable Nosocomial Transmission}, volume={55}, ISSN={["1943-3700"]}, DOI={10.7589/2018-06-162}, abstractNote={Abstract: We describe an investigation of an outbreak of conjunctivitis in juvenile House Finches (Haemorhous mexicanus) and California Scrub-jays (Aphelocoma californica) at a central California, US wildlife rehabilitation facility. In late May 2015, the facility began admitting juvenile finches, the majority with normal eyes at intake. In June, with juvenile finches already present, the facility admitted juvenile scrub-jays, all with normal eyes at intake. In July, after conjunctivitis was observed in increasing numbers of juvenile finches and scrub-jays, carcasses were submitted for postmortem examination. Histopathology of five finches and three scrub-jays identified lymphocytic infiltrates in the ocular tissues. Conjunctival swabs from 87% (13/15) finches and 33% (4/12) scrub-jays were PCR-positive for Mycoplasma gallisepticum. One finch and two scrub-jays were PCR-positive for Mycoplasma synoviae. Additionally, gene sequencing (16S ribosomal RNA and 16S-23S intergenic spacer region) identified Mycoplasma sturni from 33% (3/9) scrub-jays. This outbreak of conjunctivitis suggested that M. gallisepticum-infected juvenile finches admitted to and maintained in a multispecies nursery likely resulted in transmission within the facility to healthy juvenile finches and scrub-jays. Evidence of other Mycoplasma spp. in finches and scrub-jays indicates that these species are susceptible to infection and may act as carriers. This outbreak highlighted the need for effective triage and biosecurity measures within wildlife rehabilitation facilities.}, number={2}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Rogers, Krysta H. and Ley, David H. and Woods, Leslie W.}, year={2019}, month={Apr}, pages={494–498} }
 @article{ghanem_wang_zhang_edwards_lu_ley_el-gazzar_2018, title={Core Genome Multilocus Sequence Typing: a Standardized Approach for Molecular Typing of Mycoplasma gallisepticum}, volume={56}, ISSN={["1098-660X"]}, DOI={10.1128/jcm.01145-17}, abstractNote={ABSTRACT}, number={1}, journal={JOURNAL OF CLINICAL MICROBIOLOGY}, author={Ghanem, Mostafa and Wang, Leyi and Zhang, Yan and Edwards, Scott and Lu, Amanda and Ley, David and El-Gazzar, Mohamed}, year={2018}, month={Jan} }
 @article{allen_mara_tulman_ley_geary_2018, title={House Finch (Haemorhous mexicanus)-Associated Mycoplasma gallisepticum Identified in Lesser Goldfinch (Spinus psaltria) and Western Scrub Jay (Aphelocoma californica) using Strain-Specific Quantitative PCR}, volume={54}, ISSN={["1943-3700"]}, DOI={10.7589/2017-04-079}, abstractNote={ABSTRACT:  In 1994 Mycoplasma gallisepticum was found to be the etiologic agent of House Finch (Haemorhous mexicanus) conjunctivitis, a rapidly expanding epidemic caused by a genetically discrete, House Finch–associated strain of M. gallisepticum (HFMG). While most prominent in House Finches, HFMG has been reported in other members of the family Fringillidae, including American Goldfinches (Spinus tristis), Purple Finches (Haemorhous purpureus), Pine Grosbeaks (Pinicola enucleator), and Evening Grosbeaks (Coccothraustes vespertinus). Herein we report two new potential host species of HFMG strain, the Lesser Goldfinch (Spinus psaltria), belonging to the Fringillidae family, and the Western (California) Scrub Jay (Aphelocoma californica), belonging to the Corvidae family. The latter is one of only two reports of HFMG being found outside the Fringillidae family, and of these is the only one reported outside of captivity. Furthermore, non-HFMG M. gallisepticum was identified in an American Crow (Corvus brachyrhynchos), indicating presence of additional strains in wild birds. Strain typing of M. gallisepticum isolates was done via HFMG-specific quantitative PCR analysis and validated using random amplified polymorphic DNA analysis. Our results suggested an expanded host range of HFMG strain, and further suggested that the host range of HFMG was not limited to members of the family Fringillidae.}, number={1}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Allen, Catherine R. and Mara, Arlind and Tulman, Edan R. and Ley, David H. and Geary, Steven J.}, year={2018}, month={Jan}, pages={180–185} }
 @article{fleming-davies_williams_dhondt_dobson_hochachka_leon_ley_osnas_hawley_2018, title={Incomplete host immunity favors the evolution of virulence in an emergent pathogen}, volume={359}, ISSN={["1095-9203"]}, DOI={10.1126/science.aao2140}, abstractNote={Ratcheting up wild virulence}, number={6379}, journal={SCIENCE}, author={Fleming-Davies, Arietta E. and Williams, Paul D. and Dhondt, Andre A. and Dobson, Andrew P. and Hochachka, Wesley M. and Leon, Ariel E. and Ley, David H. and Osnas, Erik E. and Hawley, Dana M.}, year={2018}, month={Mar}, pages={1030-+} }
 @article{pflaum_tulman_beaudet_liao_dhondt_dhondt_hawley_ley_kerr_geary_2017, title={Attenuated Phenotype of a Recent House Finch-Associated Mycoplasma gallisepticum Isolate in Domestic Poultry}, volume={85}, ISSN={["1098-5522"]}, DOI={10.1128/iai.00185-17}, abstractNote={ABSTRACT}, number={6}, journal={INFECTION AND IMMUNITY}, author={Pflaum, K. and Tulman, E. R. and Beaudet, J. and Liao, X. and Dhondt, K. V. and Dhondt, A. A. and Hawley, D. M. and Ley, D. H. and Kerr, K. M. and Geary, S. J.}, year={2017}, month={Jun} }
 @article{dhondt_dhondt_hochachka_ley_hawley_2017, title={Response of House Finches Recovered from Mycoplasma gallisepticum to Reinfection with a Heterologous Strain}, volume={61}, ISSN={["1938-4351"]}, DOI={10.1637/11571-122016-reg.1}, abstractNote={SUMMARY After recovery, house finches (Haemorhous mexicanus) reinfected with the same Mycoplasma gallisepticum strain remain partially resistant to reinfection for at least 14 mo in that they recover from reinfection much more rapidly than do Mycoplasma gallisepticum-naïve birds. To test the response of birds to reinfection with a heterologous strain we performed two experiments. In a first experiment we exposed birds to one of three strains that differed in virulence. After they had recovered all were reinfected with the most virulent-strain available at the time of the experiment. In a second experiment we infected and later reinfected house finches with one of two Mycoplasma gallisepticum strains whereby we switched the order of the strain used. In both experiments, disease in birds reinfected with a more-virulent strain caused more-severe disease. Our data suggest that the observed increase in Mycoplasma gallisepticum virulence, once the disease has become endemic in free-ranging house finches is—in part—driven by increased resistance of recovered birds to strains of equal or lower virulence.}, number={4}, journal={AVIAN DISEASES}, author={Dhondt, Andre A. and Dhondt, Keila V. and Hochachka, Wesley M. and Ley, David H. and Hawley, Dana M.}, year={2017}, month={Dec}, pages={437–441} }
 @article{ley_hawley_geary_dhondt_2016, title={House Finch (Haemorhous mexicanus) Conjunctivitis, and Mycoplasma spp. Isolated from North American Wild Birds, 1994-2015}, volume={52}, ISSN={["1943-3700"]}, DOI={10.7589/2015-09-244}, abstractNote={Abstract Sampling wild birds for mycoplasma culture has been key to the study of House Finch (Haemorhous mexicanus) conjunctivitis, yielding isolates of Mycoplasma gallisepticum spanning the temporal and geographic ranges of disease from emergence to endemicity. Faced with the challenges and costs of sample collection over time and from remote locations for submission to our laboratory for mycoplasma culture, protocols evolved to achieve a practical optimum. Herein we report making M. gallisepticum isolates from House Finches almost every year since the disease emerged in 1994, and we now have 227 isolates from 17 states. Our wild bird host range for M. gallisepticum isolates includes Blue Jay (Cyanocitta cristata), American Goldfinch (Spinus tristis), Lesser Goldfinch (Spinus psaltria), Purple Finch (Haemorhous purpureus), Evening Grosbeak (Coccothraustes vespertinus), and herein first reports for Western Scrub-jay (Aphelocoma californica), and American Crow (Corvus brachyrhynchos). By collecting and identifying isolates from birds with clinical signs similar to those of House Finch conjunctivitis, we also expanded the known host range of Mycoplasma sturni and obtained isolates from additional wild bird species. Accumulating evidence shows that a diverse range of wild bird species may carry or have been exposed to M. gallisepticum in the US, as in Europe and Asia. Therefore, the emergence of a pathogenic M. gallisepticum strain in House Finches may actually be the exception that has allowed us to identify the broader epidemiologic picture.}, number={3}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Ley, David H. and Hawley, Dana M. and Geary, Steven J. and Dhondt, Andre A.}, year={2016}, month={Jul}, pages={669–673} }
 @article{dhondt_decoste_ley_hochachka_2014, title={Diverse Wild Bird Host Range of Mycoplasma gallisepticum in Eastern North America}, volume={9}, ISSN={["1932-6203"]}, DOI={10.1371/journal.pone.0103553}, abstractNote={Emerging infectious diseases often result from pathogens jumping to novel hosts. Identifying possibilities and constraints on host transfer is therefore an important facet of research in disease ecology. Host transfers can be studied for the bacterium Mycoplasma gallisepticum, predominantly a pathogen of poultry until its 1994 appearance and subsequent epidemic spread in a wild songbird, the house finch Haemorhous mexicanus and some other wild birds. We screened a broad range of potential host species for evidence of infection by M. gallisepticum in order to answer 3 questions: (1) is there a host phylogenetic constraint on the likelihood of host infection (house finches compared to other bird species); (2) does opportunity for close proximity (visiting bird feeders) increase the likelihood of a potential host being infected; and (3) is there seasonal variation in opportunity for host jumping (winter resident versus summer resident species). We tested for pathogen exposure both by using PCR to test for the presence of M. gallisepticum DNA and by rapid plate agglutination to test for the presence of antibodies. We examined 1,941 individual birds of 53 species from 19 avian families. In 27 species (15 families) there was evidence for exposure with M. gallisepticum although conjunctivitis was very rare in non-finches. There was no difference in detection rate between summer and winter residents, nor between feeder birds and species that do not come to feeders. Evidence of M. gallisepticum infection was found in all species for which at least 20 individuals had been sampled. Combining the present results with those of previous studies shows that a diverse range of wild bird species may carry or have been exposed to M. gallisepticum in the USA as well as in Europe and Asia.}, number={7}, journal={PLOS ONE}, author={Dhondt, Andre A. and DeCoste, Jonathan C. and Ley, David H. and Hochachka, Wesley M.}, year={2014}, month={Jul} }
 @article{grodio_ley_schat_hawley_2013, title={Chronic Mycoplasma conjunctivitis in house finches: Host antibody response and M. gallisepticum VlhA expression}, volume={154}, ISSN={["1873-2534"]}, DOI={10.1016/j.vetimm.2013.05.010}, abstractNote={Previous studies have shown that house finch field isolates of Mycoplasma gallisepticum (MG) vary in virulence and ability to induce an antibody response. After experimental inoculation, MG causes persistent, severe disease in a subset of individuals. In this study, we further characterized MG infection using five field isolates, with an emphasis on chronically diseased birds. After experimental inoculation of house finches, MG load was measured by quantitative PCR and anti-MG antibody responses were measured by ELISAs. Birds with chronic disease had significantly higher pathogen loads and antibody responses than did birds without chronic disease. Using a monoclonal antibody (MAb86) specific for a variant of the MG VlhA adhesin and immunodominant surface protein, we show that VlhA expression differs among MG isolates in this study, and that in vivo VlhA changes occur in house finches infected with MG. Overall, our results suggest that chronic MG disease has a strong pathogen-mediated component.}, number={3-4}, journal={VETERINARY IMMUNOLOGY AND IMMUNOPATHOLOGY}, author={Grodio, Jessica L. and Ley, David H. and Schat, Karel A. and Hawley, Dana M.}, year={2013}, month={Aug}, pages={129–137} }
 @article{hochachka_dhondt_dobson_hawley_ley_lovette_2013, title={Multiple host transfers, but only one successful lineage in a continent-spanning emergent pathogen}, volume={280}, ISSN={["0962-8452"]}, DOI={10.1098/rspb.2013.1068}, abstractNote={
            Emergence of a new disease in a novel host is thought to be a rare outcome following frequent pathogen transfers between host species. However, few opportunities exist to examine whether disease emergence stems from a single successful pathogen transfer, and whether this successful lineage represents only one of several pathogen transfers between hosts. We examined the successful host transfer and subsequent evolution of the bacterial pathogen
            Mycoplasma gallisepticum
            , an emergent pathogen of house finches (
            Haemorhous
            (formerly
            Carpodacus
            )
            mexicanus
            ). Our principal goals were to assess whether host transfer has been a repeated event between the original poultry hosts and house finches, whether only a single host transfer was ultimately responsible for the emergence of
            M. gallisepticum
            in these finches, and whether the spread of the pathogen from east to west across North America has resulted in spatial structuring in the pathogen. Using a phylogeny of
            M. gallisepticum
            based on 107 isolates from domestic poultry, house finches and other songbirds, we infer that the bacterium has repeatedly jumped between these two groups of hosts but with only a single lineage of
            M. gallisepticum
            persisting and evolving in house finches; bacterial evolution has produced monophyletic eastern and western North American subclades.
          }, number={1766}, journal={PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES}, author={Hochachka, Wesley M. and Dhondt, Andre A. and Dobson, Andrew and Hawley, Dana M. and Ley, David H. and Lovette, Irby J.}, year={2013}, month={Sep} }
 @article{van wettere_ley_scott_buckanoff_degernes_2013, title={Mycoplasma Corogypsi-Associated Polyarthritis and Tenosynovitis in Black Vultures (Coragyps atratus)}, volume={50}, ISSN={["1544-2217"]}, DOI={10.1177/0300985812457791}, abstractNote={ Three wild American black vultures ( Coragyps atratus) were presented to rehabilitation centers with swelling of multiple joints, including elbows, stifles, hocks, and carpal joints, and of the gastrocnemius tendons. Cytological examination of the joint fluid exudate indicated heterophilic arthritis. Radiographic examination in 2 vultures demonstrated periarticular soft tissue swelling in both birds and irregular articular surfaces with subchondral bone erosion in both elbows in 1 bird. Prolonged antibiotic therapy administered in 2 birds did not improve the clinical signs. Necropsy and histological examination demonstrated a chronic lymphoplasmacytic arthritis involving multiple joints and gastrocnemius tenosynovitis. Articular lesions varied in severity and ranged from moderate synovitis and cartilage erosion and fibrillation to severe synovitis, diffuse cartilage ulceration, subchondral bone loss and/or sclerosis, pannus, synovial cysts, and epiphyseal osteomyelitis. No walled bacteria were observed or isolated from the joints. However, mycoplasmas polymerase chain reactions were positive in at least 1 affected joint from each bird. Mycoplasmas were isolated from joints of 1 vulture that did not receive antibiotic therapy. Sequencing of 16S rRNA gene amplicons from joint samples and the mycoplasma isolate identified Mycoplasma corogypsi in 2 vultures and was suggestive in the third vulture. Mycoplasma corogypsi identification was confirmed by sequencing the 16S-23S intergenic spacer region of mycoplasma isolates. This report provides further evidence that M. corogypsi is a likely cause of arthritis and tenosynovitis in American black vultures. Cases of arthritis and tenosynovitis in New World vultures should be investigated for presence of Mycoplasma spp, especially M. corogypsi. }, number={2}, journal={VETERINARY PATHOLOGY}, author={Van Wettere, A. J. and Ley, D. H. and Scott, D. E. and Buckanoff, H. D. and Degernes, L. A.}, year={2013}, month={Mar}, pages={291–298} }
 @article{hawley_osnas_dobson_hochachka_ley_dhondt_2013, title={Parallel Patterns of Increased Virulence in a Recently Emerged Wildlife Pathogen}, volume={11}, ISSN={["1545-7885"]}, DOI={10.1371/journal.pbio.1001570}, abstractNote={A bacterial pathogen of wild songbirds evolved higher virulence following its emergence in two separate regions of the host range.}, number={5}, journal={PLOS BIOLOGY}, author={Hawley, Dana M. and Osnas, Erik E. and Dobson, Andrew P. and Hochachka, Wesley M. and Ley, David H. and Dhondt, Andre A.}, year={2013}, month={May} }
 @article{ley_moresco_frasca_2012, title={Conjunctivitis, rhinitis, and sinusitis in cliff swallows (Petrochelidon pyrrhonota) found in association with Mycoplasma sturni infection and cryptosporidiosis}, volume={41}, ISSN={["0307-9457"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84867852211&partnerID=MN8TOARS}, DOI={10.1080/03079457.2012.697624}, abstractNote={Fledgling cliff swallows were cared for at a rehabilitation facility when clinical signs of ocular disease, characterized by conjunctivitis, epiphora, and hyperaemia of palpebrae and nictitans, were recognized. Treatment consisted of topical and oral antibiotic therapy and one topical steroid administration. However, one cliff swallow died and three were killed due to poor therapeutic response. Conjunctival swabs were obtained ante-mortem from the three cliff swallows and were submitted for mycoplasma culture and molecular diagnostics. Heads of the three birds were fixed in 10% neutral buffered formalin and submitted for histopathologic examination of oculonasal tissues. Mycoplasma cultures and molecular evaluation of isolates identified Mycoplasma sturni, but not Mycoplasma gallisepticum, from each specimen. Histopathologic examination revealed lymphoplasmacytic conjunctivitis, rhinitis and infraorbital sinusitis with follicular lymphoid hyperplasia, epithelial hyperplasia, and protozoal stages compatible with Cryptosporidium spp. arranged in and along the apical surfaces of epithelial cells. Identification of concurrent M. sturni and Cryptosporidium spp. infections in these cliff swallows demonstrates an alternative infectious condition that can produce gross and microscopic lesions comparable with those commonly observed in M. gallisepticum infections of house finches and other passerine species. Conjunctivitis associated with M. sturni and Cryptosporidium spp. in cliff swallows may represent an emerging disease risk to a naïve, high-density and colonial species such as colony-nesting cliff swallows.}, number={4}, journal={AVIAN PATHOLOGY}, author={Ley, David H. and Moresco, Anneke and Frasca, Salvatore, Jr.}, year={2012}, pages={395–401} }
 @article{tulman_liao_szczepanek_ley_kutish_geary_2012, title={Extensive variation in surface lipoprotein gene content and genomic changes associated with virulence during evolution of a novel North American house finch epizootic strain of Mycoplasma gallisepticum}, volume={158}, ISSN={["1465-2080"]}, DOI={10.1099/mic.0.058560-0}, abstractNote={Mycoplasma gallisepticum, a significant respiratory and reproductive pathogen of domestic poultry, has since 1994 been recognized as an emergent pathogen of the American house finch (Carpodacus mexicanus). Epizootic spread and pathognomonic characteristics of house finch-associated Mycoplasma gallisepticum (HFMG) have been studied as a model of an emergent to endemic pathogen in a novel host. Here we present comparative analysis of eight HFMG genomes, including one from an index isolate and seven isolates separated spatially and temporally (1994-2008) across the epizootic, and notably having differences in virulence. HFMG represented a monophyletic clade relative to sequenced poultry isolates, with genomic changes indicating a novel M. gallisepticum lineage and including unique deletions of coding sequence. Though most of the HFMG genome was highly conserved among isolates, genetic distances correlated with temporal-spatial distance from the index. The most dramatic genomic differences among HFMG involved phase-variable and immunodominant VlhA lipoprotein genes, including those variable in presence and genomic location. Other genomic differences included tandem copy number variation of a 5 kbp repeat, changes in and adjacent to the clustered regularly interspaced short palindromic repeats, and small-scale changes affecting coding potential and association of genes with virulence. Divergence of monophyletic isolates from similar time/space in the epizootic indicated local diversification of distinct HFMG sublineages. Overall, these data identify candidate virulence genes and reveal the importance of phase-variable lipoproteins during the evolution of M. gallisepticum during its emergence and dissemination in a novel host in nature, likely mediating an important role at the interface between pathogen virulence and host immunity.}, journal={MICROBIOLOGY-SGM}, author={Tulman, E. R. and Liao, X. and Szczepanek, S. M. and Ley, D. H. and Kutish, G. F. and Geary, S. J.}, year={2012}, month={Aug}, pages={2073–2088} }
 @article{grodio_hawley_osnas_ley_dhondt_dhondt_schat_2012, title={Pathogenicity and immunogenicity of three Mycoplasma gallisepticum isolates in house finches (Carpodacus mexicanus)}, volume={155}, ISSN={["0378-1135"]}, DOI={10.1016/j.vetmic.2011.08.003}, abstractNote={Mycoplasma gallisepticum (MG) has become a common cause of conjunctivitis in free-living house finches (Carpodacus mexicanus) since its emergence in the early 1990s. To date, temporal and spatial genotypic variation in MG has been documented, but phenotypic variation in pathogenicity and immunogenicity has not been examined. House finches were inoculated with MG isolates Virginia (VA)1994, California (CA)2006, or North Carolina (NC)2006, which were cultured from free-living house finches with conjunctivitis in 1994, 2006, and 2006, respectively. Infection with NC2006 resulted in the most severe eye lesions, highest pathogen loads, and highest levels of pathogen-specific lachrymal and serum antibodies. Infection with CA2006 caused the least severe eye lesions, lowest pathogen load, and lowest levels of antibodies. A small number of birds in each group developed protracted, severe disease in spite of robust antibody responses, suggesting that immunopathology may contribute to the lesions. Immunoblot analyses indicated that isolates are antigenically similar; thus, there may be partial cross-protection if a house finch encounters two or more strains of MG throughout the course of its lifetime. This study provides evidence that MG strains or strain variants circulating in house finch populations vary in their ability to cause disease, induce antibody responses, and persist in the host.}, number={1}, journal={VETERINARY MICROBIOLOGY}, author={Grodio, Jessica L. and Hawley, Dana M. and Osnas, Erik E. and Ley, David H. and Dhondt, Keila V. and Dhondt, Andre A. and Schat, Karel A.}, year={2012}, month={Feb}, pages={53–61} }
 @article{hawley_grodio_frasca_kirkpatrick_ley_2011, title={Experimental infection of domestic canaries (Serinus canaria domestica) with Mycoplasma gallisepticum: a new model system for a wildlife disease}, volume={40}, ISSN={["0307-9457"]}, DOI={10.1080/03079457.2011.571660}, abstractNote={The ethical and logistical challenges inherent in experimental infections of wild-caught animals present a key limitation to the study of wildlife diseases. Here we characterize a potentially useful domestic model for a wildlife disease that has been of particular interest in recent decades; that is, infection of North American house finches (Carpodacus mexicanus) with Mycoplasma gallisepticum, more commonly known as a worldwide poultry pathogen. Seven domestic canaries (Serinus canaria domestica) were infected experimentally with M. gallisepticum alongside two wild-caught house finches (C. mexicanus) and the resulting clinical disease, pathogen load, serology and pathology were compared. Although rates of morbidity were higher in domestic canaries in response to M. gallisepticum infection, no significant differences were detected between the two species in the four measures of infection and disease studied. Our results support previous field and experimental studies that have documented universal susceptibility to M. gallisepticum infection in the avian family Fringillidae, which includes domestic canaries. Our results also indicate that domestic canaries may serve as a potentially useful model system for the experimental study of M. gallisepticum infection in songbirds.}, number={3}, journal={AVIAN PATHOLOGY}, author={Hawley, Dana M. and Grodio, Jessica and Frasca, Salvatore, Jr. and Kirkpatrick, Laila and Ley, David H.}, year={2011}, pages={321–327} }
 @article{hawley_dhondt_dobson_grodio_hochachka_ley_osnas_schat_dhondt_2010, title={Common garden experiment reveals pathogen isolate but no host genetic diversity effect on the dynamics of an emerging wildlife disease}, volume={23}, ISSN={["1010-061X"]}, DOI={10.1111/j.1420-9101.2010.02035.x}, abstractNote={Abstract}, number={8}, journal={JOURNAL OF EVOLUTIONARY BIOLOGY}, author={Hawley, D. M. and Dhondt, K. V. and Dobson, A. P. and Grodio, J. L. and Hochachka, W. M. and Ley, D. H. and Osnas, E. E. and Schat, K. A. and Dhondt, A. A.}, year={2010}, month={Aug}, pages={1680–1688} }
 @article{ley_marusak_vivas_barnes_fletcher_2010, title={Mycoplasma iowae associated with chondrodystrophy in commercial turkeys}, volume={39}, ISSN={["0307-9457"]}, DOI={10.1080/03079451003599276}, abstractNote={Opportunistic observations of and necropsies from selected commercial (meat) turkey flocks revealed skeletal lesions consistent with chondrodystrophy, characterized by leg and vertebral deformities, occurring at very low incidences in turkeys from two primary breeds and various multiplier breeder flocks. Mycoplasma organisms were cultured and identified as Mycoplasma iowae by immunofluorescence and polymerase chain reaction from some of the vertebral lesions but not from leg joints. This is the first detailed description of the gross and microscopic lesions of vertebral chondrodystrophy associated with M. iowae, which should now be considered in the differential diagnosis of turkeys with these lesions.}, number={2}, journal={AVIAN PATHOLOGY}, author={Ley, David H. and Marusak, Rosemary A. and Vivas, Eduardo J. and Barnes, H. John and Fletcher, Oscar J.}, year={2010}, pages={87–93} }
 @article{ley_anderson_dhondt_dhondt_2010, title={Mycoplasma sturni from a California House Finch with Conjunctivitis Did Not Cause Disease in Experimentally Infected House Finches}, volume={46}, ISSN={["1943-3700"]}, DOI={10.7589/0090-3558-46.3.994}, abstractNote={Mycoplasma gallisepticum conjunctivitis emerged in 1994 as a disease of free-ranging House Finches (Carpodacus mexicanus) in North America and has also been isolated from other songbirds with conjunctivitis. A key feature for the successful study of natural and experimental disease has been the apparent, very-high correlation between characteristic eye lesions and M. gallisepticum. Mycoplasma sturni was originally isolated from an adult European Starling (Sturnus vulgaris) with bilateral conjunctivitis and has since been reported in a relatively small number of other avian species, but not in House Finches. We identified as M. sturni a mycoplasma isolate from a California House Finch with conjunctivitis. However, experimental infection of House Finches with the M. sturni isolate failed to reproduce the disease. Therefore, M. gallisepticum remains the primary known cause of conjunctivitis in House Finches.}, number={3}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Ley, David H. and Anderson, Nancy and Dhondt, Keila V. and Dhondt, Andre A.}, year={2010}, month={Jul}, pages={994–999} }
 @article{dhondt_dhondt_ley_2007, title={Effects of route of inoculation on Mycoplasma gallisepticum infection in captive house finches}, volume={36}, ISSN={["1465-3338"]}, DOI={10.1080/03079450701642016}, abstractNote={The routes by which Mycoplasma gallisepticum initiates infection during outbreaks of conjunctivitis in house finches remain uncertain. As M. gallisepticum recovered from the cloaca of chickens remains viable for up to 3 days in chicken faeces, the possibility of spread via faecal contamination has been suggested. To test the hypothesis that food or water contaminated with M. gallisepticum may initiate infection, 20 house finches were experimentally inoculated by the oral or the conjunctival route. Clinical and immunological responses were compared. All inoculated birds seroconverted, thus demonstrating infection. Only two of the birds inoculated via the oral route developed very mild unilateral conjunctivitis while all 10 of those infected by eye-drop inoculation developed severe bilateral conjunctivitis. The orally inoculated birds had reduced levels of activity for only a few days, while those infected by conjunctival inoculation had reduced activity for several weeks. M. gallisepticum DNA was detected in conjunctival swabs by polymerase chain reaction in only three orally inoculated birds but in all birds in the conjunctivally inoculated group. Antibodies developed more slowly after oral inoculation than after conjunctival inoculation. We showed that oral exposure to M. gallisepticum can initiate infection, disease, and a serological response, which suggests that food or water contaminated with secretions or excretions may be a route of transmission between house finches.}, number={6}, journal={AVIAN PATHOLOGY}, author={Dhondt, Keila V. and Dhondt, Andre A. and Ley, David H.}, year={2007}, pages={475–479} }
 @article{sanei_barnes_vaillancourt_ley_2007, title={Experimental infection of chickens and turkeys with Mycoplasma gallisepticum reference strain S6 and North Carolina field isolate RAPD type B}, volume={51}, ISSN={["0005-2086"]}, DOI={10.1637/0005-2086(2007)051[0106:EIOCAT]2.0.CO;2}, abstractNote={Abstract During an epidemic of mycoplasmosis in chicken and turkey flocks in North Carolina between 1999 and 2001, isolates of Mycoplasma gallisepticum (MG) from affected flocks were characterized by random amplification of polymorphic DNA (RAPD), and eight distinct RAPD types were identified. MG RAPD type B accounted for more than 90% of the isolates and was associated with moderate-to-severe clinical signs and mortality. The virulence of MG RAPD type B for chickens and turkeys was compared with sham-inoculated negative controls and MG S6 (a virulent strain)-inoculated positive controls. Clinical signs occurred in chickens and turkeys inoculated with either MG RAPD type B or MG S6. However, they were not as frequent or severe as those seen in naturally affected flocks, and there was no mortality in the experimental groups. Based on gross and microscopic findings, MG RAPD type B was equal to or more virulent than MG S6. All MG-inoculated birds were culture and PCR positive at 7 and 14 days postinoculation (PI). Among serological tests, the serum plate agglutination test was positive for the majority of chickens and turkeys (58%–100%) infected with either strain of MG at both 7 and 14 days PI. The hemagglutination inhibition test was negative for all birds at 7 days PI and positive for a few chickens (8%–17%) and several turkey sera (40%–60%) at 14 days PI. Only a single serum was positive by enzyme-linked immunosorbent assay (an MG S6-infected turkey) at 14 days PI.}, number={1}, journal={AVIAN DISEASES}, author={Sanei, B. and Barnes, H. J. and Vaillancourt, J. P. and Ley, D. H.}, year={2007}, month={Mar}, pages={106–111} }
 @article{osorio_fletcher_abdul-aziz_gonder_tilley_ley_2007, title={Pneumonia of Turkey Breeder Hens Associated with Mycoplasma synoviae}, volume={51}, ISSN={["0005-2086"]}, DOI={10.1637/0005-2086(2007)51[791:POTBHA]2.0.CO;2}, abstractNote={Abstract Turkey breeder hens showed an increase in mortality beginning at 38 wk of age with no other clinical signs or changes in egg production. While no respiratory signs were observed in live turkeys, those that died consistently had gross lesions of pneumonia. Histopathology of lungs revealed serofibrinous bronchopneumonia, lymphofollicular reaction, and other features suggesting a bacterial etiology. However, except for incidental findings, bacteria were not visualized in the sections examined, and none were isolated in meaningful numbers on routine bacteriologic media. At 42 wk of age the flock showed serologic evidence of infection with Mycoplasma synoviae (MS), and MS was identified by both mycoplasma culture and polymerase chain reaction (PCR) procedures in samples from choanal clefts and tracheas. Results of lung histopathology and PCR tests were consistent with a diagnosis of pneumonia caused by MS.}, number={3}, journal={AVIAN DISEASES}, author={Osorio, Claudia and Fletcher, Oscar J. and Abdul-Aziz, Tahseen and Gonder, Eric and Tilley, Becky and Ley, David H.}, year={2007}, month={Sep}, pages={791–796} }
 @article{ley_sheaffer_dhondt_2006, title={Further western spread of Mycoplasma gallisepticum infection of house finches}, volume={42}, ISSN={["0090-3558"]}, DOI={10.7589/0090-3558-42.2.429}, abstractNote={Mycoplasma gallisepticum, an important pathogen of poultry, especially chickens and turkeys, emerged in 1994 as the cause of conjunctivitis in house finches (Carpodacus mexicanus) in their eastern range of North America. The resulting epidemic of M. gallisepticum conjunctivitis severely decreased house finch abundance and the continuing endemic disease in the eastern range has been associated with repeating seasonal peaks of conjunctivitis and limitation of host populations. Mycoplasma gallisepticum conjunctivitis was first confirmed in the western native range of house finches in 2002 in a Missoula, Montana, population. Herein, we report further western expansion of M. gallisepticum conjunctivitis in the native range of house finches based on positive polymerase chain reaction results with samples from birds captured in 2004 and 2005 near Portland, Oregon.}, number={2}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Ley, David H. and Sheaffer, Deborah S. and Dhondt, Andre A.}, year={2006}, month={Apr}, pages={429–431} }
 @article{cherry_ley_altizer_2006, title={Genotypic analyses of Mycoplasma gallisepticum isolates from songbirds by random amplification of polymorphic DNA and amplified-fragment length polymorphism}, volume={42}, ISSN={["0090-3558"]}, DOI={10.7589/0090-3558-42.2.421}, abstractNote={Mycoplasma gallisepticum (MG) conjunctivitis emerged in 1994 as a disease of free-ranging house finches (Carpodacus mexicanus) in North America and has also been isolated from other songbirds with conjunctivitis. Random amplification of polymorphic DNA (RAPD) of house finch and other songbird isolates has suggested that a single ‘strain’ initiated this outbreak. To explore the possibility of genomic variability among house finch isolates of MG and to evaluate the utility of a second technique for MG genotyping, we selected samples from our archive of reference strains and wild songbird isolates to analyze using both RAPD and amplified-fragment length polymorphism (AFLP); this is a newer technique that has been successfully used to explore the genomic variability of several Mycoplasma species. Both RAPD and AFLP results confirmed previous observations that during the initial stages of the MG epidemic in songbirds, isolates from different geographic locations and songbird species had genotypes that appeared to be highly similar, further supporting a single point source of origin. One 2001 isolate from New York was clearly different from the other songbird samples and clustered together with the vaccine and reference strains, indicating that substantial molecular evolution or a separate introduction has occurred.}, number={2}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Cherry, John J. and Ley, David H. and Altizer, Sonia}, year={2006}, month={Apr}, pages={421–428} }
 @article{hong_garcia_levisohn_savelkoul_leiting_lysnyansky_ley_kleven_2005, title={Differentiation of Mycoplasma gallisepticum strains using amplified fragment length polymorphism and other DNA-based typing methods}, volume={49}, ISSN={["0005-2086"]}, DOI={10.1637/7254-080504R}, abstractNote={Abstract Amplified fragment length polymorphism (AFLP) was used to type 34 strains of Mycoplasma gallisepticum (MG) including vaccine strains ts-11, 6/85, and F. Using AFLP, a total of 10 groups, with 30 distinguishable AFLP typing profiles, were generated in the analysis. The AFLP method was able to identify and differentiate both MG field strains from recent outbreaks and those that were epidemiologically related. The AFLP procedure will provide assistance in identifying the sources of mycoplasma infections. Vaccine strains were also differentiated from other field strains, which will be useful in the evaluation of vaccination programs. The AFLP discrimination potential was compared to other molecular typing techniques such as gene-targeted typing by DNA sequence analysis of the MG cytadhesin-like protein encoding gene, mgc2, and random amplified polymorphic DNA assay on the same MG isolates. The three assays correlated well with one another, with AFLP analysis having a much higher discriminatory power and reproducibility.}, number={1}, journal={AVIAN DISEASES}, author={Hong, Y and Garcia, M and Levisohn, S and Savelkoul, P and Leiting, V and Lysnyansky, I and Ley, DH and Kleven, SH}, year={2005}, month={Mar}, pages={43–49} }
 @article{dhondt_altizer_cooch_davis_dobson_driscoll_hartup_hawley_hochachka_hosseini_et al._2005, title={Dynamics of a novel pathogen in an avian host: Mycoplasmal conjunctivitis in house finches}, volume={94}, ISSN={["1873-6254"]}, DOI={10.1016/j.actatropica.2005.01.009}, abstractNote={In early 1994, a novel strain of Mycoplasma gallisepticum (MG)--a poultry pathogen with a world-wide distribution--emerged in wild house finches and within 3 years had reached epidemic proportions across their eastern North American range. The ensuing epizootic resulted in a rapid decline of the host population coupled with considerable seasonal fluctuations in prevalence. To understand the dynamics of this disease system, a multi-disciplinary team composed of biologists, veterinarians, microbiologists and mathematical modelers set forth to determine factors driving and influenced by this host-pathogen system. On a broad geographic scale, volunteer observers ("citizen scientists") collected and reported data used for calculating both host abundance and disease prevalence. The scale at which this monitoring initiative was conducted is unprecedented and it has been an invaluable source of data for researchers at the Cornell Laboratory of Ornithology to track the spread and magnitude of disease both spatially and temporally. At a finer scale, localized and intensive field studies provided data used to quantify the effects of disease on host demographic parameters via capture-mark-recapture modeling, effects of host behavior on disease and vice-versa, and the biological and genetic profiles of birds with known phenotypic characteristics. To balance the field-based component of the study, experiments were conducted with finches held in captivity to describe and quantify the effects of experimental infections on hosts in both individual and social settings. The confluence of these various elements of the investigation provided the foundation for construction of a general compartmentalized epidemiological model of the dynamics of the house finch-MG system. This paper serves several purposes including (i) a basic review of the pathogen, host, and epidemic cycle; (ii) an explanation of our research strategy; (iii) a basic review of results from the diverse multi-disciplinary approaches employed; and (iv) pertinent questions relevant to this and other wildlife disease studies that require further investigation.}, number={1}, journal={ACTA TROPICA}, author={Dhondt, AA and Altizer, S and Cooch, EG and Davis, AK and Dobson, A and Driscoll, MJL and Hartup, BK and Hawley, DM and Hochachka, WM and Hosseini, PR and et al.}, year={2005}, month={Apr}, pages={77–93} }
 @article{sydenstricker_dhondt_ley_kollias_2005, title={Re-exposure of captive house finches that recovered from Mycoplasma gallisepticum infection}, volume={41}, ISSN={["1943-3700"]}, DOI={10.7589/0090-3558-41.2.326}, abstractNote={Fourteen house finches were reinoculated (re-exposed) with 0.05 ml (3.24×105 colony forming units/ml) of Mycoplasma gallisepticum (MG) in the conjunctival sac of each eye. All birds used in this reinoculation study had recovered from previous infection between 27 and 83 days after inoculation. Recovery was based on the absence of clinical signs of conjunctivitis and/or the inability to detect MG in conjunctival or choanal samples. Birds were maintained in individual cages under controlled environmental conditions at temperature 21–24 C, relative humidity 70%, and a light cycle adjusted to ambient values. They were divided into three groups, (A, B, and C). Five birds each were reinoculated 219 days (7.3 mo, group A) and 314 days (10.47 mo, group B) after the original infection. The final group of four birds was reinoculated at 425 days after experimental infection (14.17 mo, group C). Although the birds were randomly assigned to the three groups, the duration of the disease state (number of days until clinical signs last observed) during initial infection differed: group A mean = 37.0±SE 4.549, group B mean=63.6±SE 6.306, group C mean=42.75±SE 2.750; analysis of variance F2,11=8.17, P = 0.007. Within 24 hr after reinoculation six of the 14 experimental birds had developed some clinical signs of MG-induced conjunctivitis. At 3 days after reinoculation, 12 of the 14 birds had unilateral or bilateral conjunctivitis. The duration of clinical signs in the reinoculated individuals was significantly shorter than with their previous infection. These results suggest that the birds were able to mount a rapid and strong immune response following re-exposure. However, they were susceptible to reinfection and developed disease, suggesting that reinfection or perhaps even recurrence of infection and disease could occur in the free-ranging population. This may represent an important component in the epidemiology of this disease in house finches.}, number={2}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Sydenstricker, KV and Dhondt, AA and Ley, DH and Kollias, GV}, year={2005}, month={Apr}, pages={326–333} }
 @article{kollias_sydenstricker_kollias_ley_hosseini_connolly_dhondt_2004, title={Experimental infection of house finches with Mycoplasma gallisepticum}, volume={40}, ISSN={["1943-3700"]}, DOI={10.7589/0090-3558-40.1.79}, abstractNote={Mycoplasma gallisepticum (MG) has caused an endemic upper respiratory and ocular infection in the eastern house finch (Carpodacus mexicanus) after the epidemic first described in 1994. The disease has been studied by a number of investigators at a population level and reports describe experimental infection in group-housed MG-free house finches. Because detailed observation and evaluation of individual birds in group housed passerines is problematic, we studied individually housed house finches that were experimentally inoculated with the finch strain of MG in a controlled environment. To accomplish this, a study was conducted spanning the period of November 2001–April 2002 with 20 MG-free (confirmed by the rapid plate agglutination assay and polymerase chain reaction [PCR] assay) eastern house finches captured in the Cayuga Basin area of central New York (USA) in the summer of 2001. After a period of acclimatization and observation (12 wk), 20 finches were inoculated with a 0.05-ml aliquot of MG (3.24×105 colony-forming units/ml) via bilateral conjunctival sac instillations. Two additional finches acted as controls and were inoculated in the same manner with preservative-free sterile saline solution. After inoculation, all finches except the controls exhibited clinical signs of conjunctivitis within 2–6 days. The progression of the disease was evaluated by several methods, including PCR, behavioral observations, and physical examination including eye scoring, body weight, and body condition index. Over a period of 21 wk, MG-infected finches developed signs of disease and recovered (80%), developed signs of disease and progressed to become chronically infected (15%), or died (5%). We hypothesize that the high survival rate and recovery of these finches after infection was associated with the use of controlled environmental conditions, acclimatization, a high plane of nutrition, and low stocking (housing) density, all of which are factors documented to be important in the outcome of MG infections in domestic poultry and other species.}, number={1}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Kollias, GV and Sydenstricker, KV and Kollias, HW and Ley, DH and Hosseini, PR and Connolly, V and Dhondt, AA}, year={2004}, month={Jan}, pages={79–86} }
 @article{hartup_stott-messick_guzy_ley_2004, title={Health survey of house finches (Carpodacus mexicanus) from Wisconsin}, volume={48}, ISSN={["0005-2086"]}, DOI={10.1637/7067}, abstractNote={Abstract We conducted a health survey of house finches (Carpodacus mexicanus) without evidence of Mycoplasma gallisepticum infection in order to establish baseline population health measures and estimate prevalence of potential pathogens likely to influence host susceptibility to mycoplasmosis. Seasonal changes in several physiologic parameters were observed. Weights were greater in winter compared with the breeding season (P < 0.01), fat scores were greater in winter than during fall migration (P < 0.01) or the breeding season (P < 0.01), and packed cell volume and total plasma protein measures during fall migration (P < 0.05) and winter (P < 0.01) were greater than during the breeding season. Culture of voided fecal material yielded 13 bacterial isolates likely representative of normal gastrointestinal flora. Avian pox lesions and blood and gastrointestinal parasite infections were at low prevalence (≤4%) compared with Proctophyllodes spp. feather mite infestations (32%) in the population. All parasites occurred at generally low levels in individual hosts. A logistic regression analysis of our data suggests that greater fat scores, tarsal length, and being male are potential risk factors for mite infestation in house finches.}, number={1}, journal={AVIAN DISEASES}, author={Hartup, BK and Stott-Messick, B and Guzy, M and Ley, DH}, year={2004}, pages={84–90} }
 @article{kleven_fulton_garcia_ikuta_leiting_liu_ley_opengart_rowland_wallner-pendleton_2004, title={Molecular characterization of Mycoplasma gallisepticum isolates from Turkeys}, volume={48}, ISSN={["0005-2086"]}, DOI={10.1637/7148}, abstractNote={Abstract Mycoplasma gallisepticum was isolated from several turkey flocks at different locations in the United States that were clinically affected with respiratory disease. Five of these isolates from four series of outbreaks had patterns similar to the 6/85 vaccine strain of M. gallisepticum by random amplified polymorphic DNA (RAPD) analysis using three different primer sets, whereas with a fourth primer set (OPA13 and OPA14), only two of the isolates were similar to 6/85. Results obtained by sequencing portions of the pvpA, gapA, and mgc2 genes and an uncharacterized surface lipoprotein gene indicated that the field isolates had DNA sequences that ranged from 97.6% to 100%, similar to the 6/85 results. In some of the outbreaks there was an indirect association with the presence of commercial layers in the area that had been vaccinated with this vaccine strain, but there was no known close association with vaccinated birds in any of the outbreaks. Turkeys were challenged with two of the field isolates and with 6/85 vaccine strain. Turkeys challenged with the field isolates developed respiratory disease with airsacculitis and a typical M. gallisepticum antibody response, whereas birds challenged with 6/85 developed no respiratory signs or lesions and developed only a weak antibody response. Although these isolates were very similar to the 6/85 vaccine strain, it was not possible to prove that they originated from the vaccine strain—it is possible that they could be naturally occurring field isolates.}, number={3}, journal={AVIAN DISEASES}, author={Kleven, SH and Fulton, RM and Garcia, M and Ikuta, VN and Leiting, VA and Liu, T and Ley, DH and Opengart, KN and Rowland, GN and Wallner-Pendleton, E}, year={2004}, month={Sep}, pages={562–569} }
 @article{pakpinyo_ley_barnes_vaillancourt_guy_2003, title={Enhancement of enteropathogenic Escherichia coli pathogenicity in young turkeys by concurrent turkey coronavirus infection}, volume={47}, ISSN={["0005-2086"]}, DOI={10.1637/0005-2086(2003)047[0396:EOEECP]2.0.CO;2}, abstractNote={Abstract In a previous study, turkey coronavirus (TCV) and enteropathogenic Escherichia coli (EPEC) were shown to synergistically interact in young turkeys coinfected with these agents. In that study, inapparent or mild disease was observed in turkeys inoculated with only TCV or EPEC, whereas severe growth depression and high mortality were observed in dually inoculated turkeys. The purpose of the present study was to further evaluate the pathogenesis of combined TCV/EPEC infection in young turkeys and determine the role of these agents in the observed synergistic interaction. Experiments were conducted to determine 1) effect of EPEC dose, with and without concurrent TCV infection, and 2) effect of TCV exposure, before and after EPEC exposure, on development of clinical disease. Additionally, the effect of combined infection on TCV and EPEC shedding was determined. No clinical sign of disease and no attaching and effacing (AE) lesions characteristic of EPEC were observed in turkeys inoculated with only EPEC isolate R98/5, even when turkeys were inoculated with 1010 colony forming units (CFU) EPEC (high dose exposure). Only mild growth depression was observed in turkeys inoculated with only TCV; however, turkeys inoculated with both TCV and 104 CFU EPEC (low dose exposure) developed severe disease characterized by high mortality, marked growth depression, and AE lesions. Inoculation of turkeys with TCV 7 days prior to EPEC inoculation produced more severe disease (numerically greater mortality, significantly lower survival probability [P < 0.05], increased frequency of AE lesions) than that observed in turkeys inoculated with EPEC prior to TCV or simultaneously inoculated with these agents. Coinfection of turkeys with TCV and EPEC resulted in significantly increased (P < 0.05) shedding of EPEC, but not TCV, in intestinal contents of turkeys. These findings indicate that TCV infection predisposes young turkeys to secondary EPEC infection and potentiates the expression of EPEC pathogenicity in young turkeys.}, number={2}, journal={AVIAN DISEASES}, author={Pakpinyo, S and Ley, DH and Barnes, HJ and Vaillancourt, JP and Guy, JS}, year={2003}, pages={396–405} }
 @article{pillai_mays_ley_luttrell_panangala_farmer_roberts_2003, title={Molecular variability of house finch Mycoplasma gallisepticum isolates as revealed by sequencing and restriction fragment length polymorphism analysis of the pvpA gene}, volume={47}, ISSN={["1938-4351"]}, DOI={10.1637/6095}, abstractNote={Abstract Mycoplasma gallisepticum, a major pathogen of chickens and turkeys, has caused significant declines in house finch (Carpodacus mexicanus) populations in the eastern United States since it was first observed in this species in 1994. There is evidence that M. gallisepticum infection is now endemic among eastern house finches, although disease prevalence has declined, suggesting an evolving host–parasite relationship. Studies based on randomly amplified polymorphic DNA (RAPD) have documented the presence of a single, unique RAPD profile in house finch M. gallisepticum isolates, suggesting a single point source of origin, which agrees with the known epidemiologic observations. In the present study, we evaluated the molecular variability of 55 house finch isolates as well as 11 chicken and turkey isolates including reference strains of M. gallisepticum. Molecular variability was evaluated by polymerase chain reaction (PCR)–restriction fragment length polymorphism (RFLP) analysis and nucleotide sequencing of the pvpA gene, which encodes for the putative cytadhesin protein PvpA. Three different RFLP groups and 16 genotypes were evident from the 55 house finch isolates evaluated. Sequence analysis of pvpA gene PCR products showed that although most house finch M. gallisepticum isolates clustered more closely to each other, others clustered more closely to either turkey or chicken field isolates. These findings suggest that house finch isolates are more polymorphic than previously recognized by RAPD studies. This feature may allow us to learn more about the molecular evolution and epidemiology of this emerging disease host–parasite relationship.}, number={3}, journal={AVIAN DISEASES}, author={Pillai, SR and Mays, HL and Ley, DH and Luttrell, P and Panangala, VS and Farmer, KL and Roberts, SR}, year={2003}, pages={640–648} }
 @article{pakpinyo_ley_barnes_vaillancourt_guy_2002, title={Prevalence of Enteropathogenic Escherichia coli in Naturally Occurring Cases of Poult Enteritis–Mortality Syndrome}, volume={46}, ISSN={0005-2086 1938-4351}, url={http://dx.doi.org/10.1637/0005-2086(2002)046[0360:poeeci]2.0.co;2}, DOI={10.1637/0005-2086(2002)046[0360:POEECI]2.0.CO;2}, abstractNote={SUMMARY. Enteropathogenic Escherichia coli (EPEC) previously were identified in poult enteritis–mortality syndrome (PEMS)-affected turkeys and associated as a cause of this disease. In the present study, the prevalence of EPEC in PEMS-affected turkeys was examined retrospectively with archived tissues and intestinal contents collected from 12 PEMS-affected turkey flocks in 1998. Formalin-fixed intestinal tissues were examined by light and electron microscopy for attaching and effacing (AE) lesions characteristic of EPEC, and frozen (−75 C) intestinal contents were examined for presence of EPEC. Escherichia coli isolates were characterized on the basis of epithelial cell attachment, fluorescent actin staining (FAS) test, and presence of E. coli attaching/effacing (EAE), shigalike toxin (SLT) type I, SLT II, and bundle-forming pilus (BFP) genes by polymerase chain reaction procedures. EPEC isolates were examined for pathogenicity and ability to induce AE lesions in experimentally inoculated young turkeys. AE lesions were identified by light microscopy in Giemsa-stained intestines from 7 of 12 PEMS-affected turkey flocks. Lesions consisted of bacterial microcolonies attached to epithelial surfaces with epithelial degeneration at sites of attachment and inflammatory infiltration of the lamina propria. Electron microscopy confirmed the identity of AE lesions in six of seven flocks determined to have AE lesions by light microscopy. EPEC were identified in 4 of 12 flocks on the basis of the presence of EAE genes and absence of SLT I and SLT II genes; all isolates lacked BFP genes. EPEC isolates produced AE lesions and variable mortality in turkeys coinfected with turkey coronavirus. In total, EPEC were associated with 10 of 12 (83%) naturally occurring PEMS cases on the basis of identification of AE lesions and/or EPEC isolates. These findings provide additional evidence suggesting a possible role for EPEC in the pathogenesis of PEMS.}, number={2}, journal={Avian Diseases}, publisher={American Association of Avian Pathologists (AAAP)}, author={Pakpinyo, S. and Ley, D. H. and Barnes, H. J. and Vaillancourt, J. P. and Guy, J. S.}, year={2002}, month={Apr}, pages={360–369} }
 @article{hartup_bickal_dhondt_ley_kollias_2001, title={Dynamics of conjunctivitis and Mycoplasma gallisepticum infections in house finches}, volume={118}, ISSN={["0004-8038"]}, DOI={10.1642/0004-8038(2001)118[0327:DOCAMG]2.0.CO;2}, abstractNote={Abstract Conjunctivitis, an infectious disease caused by Mycoplasma gallisepticum (MG), has produced a significant decline in eastern House Finches (Carpodacus mexicanus) of North America. In this paper, we present findings from two complementary studies designed to clarify annual and seasonal trends of MG infections in House Finches from the northeastern United States. The first was a field study of House Finches common to urban and residential habitat from Mercer County, New Jersey. We documented conjunctivitis in 11% (188/1,651) of the birds examined. Conjunctivitis prevalence in House Finches ranged from 0 to 43% per month, and exhibited marked seasonal fluctuation (elevations during fall and winter months and lower disease prevalence during the breeding season). There was excellent intermethod agreement on disease prevalence when measured by either presence of physical signs (conjunctivitis) or MG infection (kappa = 0.75). During the peak of the breeding season (April through June), conjunctivitis was present in a greater proportion of males lacking a cloacal protuberance than males with a cloacal protuberance (P < 0.01), but was similar between breeding and nonbreeding females. The second study, a volunteer survey, revealed the proportion of northeastern U.S. monitoring sites with at least one diseased House Finch each month ranged from a peak of 59% (August 1995) to a minimum of 12% (July 1999). Subsequent to the epidemic peak of disease in 1995, a series of recurring cycles occurred, with elevations in those proportions noted in late fall and winter and minima during the breeding season. Mycoplasmal conjunctivitis now appears endemic among House Finches of that region and demonstrates dynamics consistent with annual variation in host density.}, number={2}, journal={AUK}, author={Hartup, BK and Bickal, JM and Dhondt, AA and Ley, DH and Kollias, GV}, year={2001}, month={Apr}, pages={327–333} }
 @article{ley_2001, title={Identification of avian mycoplasma strains by random amplification of polymorphic DNA (RAPD)}, ISBN={0392-0593}, number={6}, journal={Zootecnica International}, author={Ley, D. H.}, year={2001}, pages={46} }
 @article{wellehan_calsamiglia_ley_zens_amonsin_kapur_2001, title={Mycoplasmosis in captive crows and robins from Minnesota}, volume={37}, ISSN={["0090-3558"]}, DOI={10.7589/0090-3558-37.3.547}, abstractNote={Mycoplasma sturni is a recently described organism previously associated with conjunctivitis in European starlings (Sturnus vulgaris), northern mockingbirds (Mimus polyglottos) and blue jays (Cyanocitta cristata). Herein we describe the isolation of M. sturni from an American crow (Corvus brachyrhynchos) presenting with conjunctivitis. A nested-PCR was designed for identification of M. sturni in clinical specimens and the sensitivity of the reaction was found to be 10 colony-changing units. The organism was found in asymptomatic American crows caged with a nestmate of the crow with conjunctivitis. Mycoplasma sturni also was found in asymptomatic American robins (Turdus migratorius) and in a European starling (Sturnus vulgaris) housed at the same facility as the crows. Heterogenity of M. sturni isolates from different host species was found by random amplified polymorphic DNA (RAPD) analyses. Heterogeneity also was found among M. sturni isolates recovered from American crows. We suggest that M. sturni can successfully infect American crows and American robins with or without the presence of clinical disease. Furthermore, we demonstrate that nested-PCR is an effective method for the detection of M. sturni and that substantial genetic heterogeneity exists among natural isolates of this bacterial pathogen.}, number={3}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Wellehan, JFX and Calsamiglia, M and Ley, DH and Zens, MS and Amonsin, A and Kapur, V}, year={2001}, month={Jul}, pages={547–555} }
 @article{mikaelian_ley_claveau_lemieux_berube_2001, title={Mycoplasmosis in evening and pine grosbeaks with conjunctivitis in Quebec}, volume={37}, ISSN={["0090-3558"]}, DOI={10.7589/0090-3558-37.4.826}, abstractNote={An outbreak of conjunctivitis affected evening grosbeaks (Coccothraustes vespertinus) and pine grosbeaks (Pinicola enucleator) in Quebec (Canada) during the winter 1998–99. One to 30% of the individuals from these two species were sick at 13 feeding stations. Sick birds were thin and had unilateral or bilateral catarrhal and lymphoplasmacytic conjunctivitis and rhinitis, and mucopurulent infraorbital sinusitis. Mycoplasmal organisms were isolated in cultures in an affected evening grosbeak and identified as Mycoplasma gallisepticum by direct immunofluorescence. Random amplified polymorphic DNA (RAPD) fin-gerprinting of this isolate resulted in a banding pattern that was identical to patterns of M. gallisepticum isolates made from similar lesions in house finches (Carpodacus mexicanus) and American gold finches (Carduelis tristis) throughout eastern North America. Mycoplasma gallisepticum was identified by polymerase chain reaction in another evening grosbeak and a pine grosbeak. These observations suggest that the same strain of M. gallisepticum is the likely etiology for the observed disease in evening and pine grosbeaks in Canada and represent an extension of the host-species range for the ongoing epidemic of M. gallisepticum conjunctivitis in eastern North America.}, number={4}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Mikaelian, I and Ley, DH and Claveau, R and Lemieux, M and Berube, JP}, year={2001}, month={Oct}, pages={826–830} }
 @article{hartup_kollias_ley_2000, title={Mycoplasmal conjunctivitis in songbirds from New York}, volume={36}, ISSN={["0090-3558"]}, DOI={10.7589/0090-3558-36.2.257}, abstractNote={A field study was conducted to determine the prevalence of conjunctivitis and Mycoplasma gallisepticum (MG) infections in house finches (Carpodacus mexicanus) and other songbirds common to bird feeders in Tompkins County (New York, USA). Eight hundred two individuals of 23 species and nine families of birds were captured and given physical examinations during the 14 mo study beginning in February 1998. Clinical conjunctivitis (eyelid or conjunctival swelling, erythema, and discharge) was observed in 10% (19/196) of house finches examined, and only in the winter months from November to March. Unilateral conjunctivitis was observed in 79% (15/19) of affected house finches; one case developed bilateral disease between 8 and 18 days following initial examination. Conjunctivitis was observed in a similar proportion of males and females sampled, and body condition scores and wing chord lengths were not significantly different between diseased and non-diseased house finches. Mycoplasma gallisepticum was isolated from 76% (13/17) of finches with conjunctivitis and 2% (3/168) of clinically normal house finches sampled during the study. DNA fingerprints of 11 MG isolates using random amplification of polymorphic DNA (RAPD) techniques showed no apparent differences in banding patterns over the course of the study, suggesting persistence of a single MG strain in the study population. The prevalence of conjunctivitis and MG infections declined in house finches between February/ March 1998 and February/March 1999 (23% to 6%, and 20% to 5%, respectively), but only the former was significant (P < 0.05). Conjunctivitis was also observed in four American goldfinches (Carduelis tristis) and one purple finch (Carpodacus purpureus). Mycoplasma gallisepticum infection was confirmed in the purple finch, the first documented case of MG-associated conjunctivitis in this species. The purple finch isolate was similar to house finch isolates from the study site by RAPD analysis. Positive plate agglutination (PA) tests were recorded in one other goldfinch and two purple finches, suggesting exposure of these individuals to MG. Positive PA tests were also obtained from two brown-headed cowbirds (Molothrus ater) and four tufted titmice (Parus bicolor), but MG infection could not be confirmed in these cases due to lack of samples. Based on these findings, the prevalence of MG infections in hosts other than house finches appear to be low in the population sampled. There is growing evidence, however, that songbird species other than house finches are susceptible to MG infection and disease.}, number={2}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Hartup, BK and Kollias, GV and Ley, DH}, year={2000}, month={Apr}, pages={257–264} }
 @article{ley_2000, title={Mycoplasmosis: somethings old and somethings new}, volume={49}, number={2000}, journal={Proceedings of the ... Western Poultry Disease Conference}, author={Ley, D. H.}, year={2000}, pages={42–47} }
 @article{ley_geary_berkhoff_mclaren_levisohn_1998, title={Mycoplasma sturni from blue jays and northern mockingbirds with conjunctivitis in Florida}, volume={34}, ISSN={["0090-3558"]}, DOI={10.7589/0090-3558-34.2.403}, abstractNote={Northern mockingbirds (Mimus polyglottos) and blue jays (Cyanocitta cristata) in a Florida (USA) wildlife care facility developed clinical signs and gross lesions suggestive of the ongoing outbreak of Mycoplasma gallisepticum (MG) conjunctivitis in house finches (Carpodacus mexicanus) and American gold-finches (Carduelis tristis). Mycoplasmal organisms were cultured from conjunctival/corneal swabs of birds with sinusitis, conjunctivitis, and/or epiphora. All of the isolates tested were identified as Mycoplasma sturni by indirect immunofluorescence. Mycoplasma sturni as well as MG should be considered in the differential diagnosis of songbirds with conjunctivitis.}, number={2}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Ley, DH and Geary, SJ and Berkhoff, JE and McLaren, JM and Levisohn, S}, year={1998}, month={Apr}, pages={403–406} }
 @article{ley_stoskopf_miller_welte_berkhoff_degernes_fleming_1997, title={Evaluation of treatment of conjunctivitis associated with Mycoplasma gallisepticum in house finches (Carpodacus mexicanus)}, volume={11}, number={1}, journal={Journal of Avian Medicine and Surgery}, author={Ley, D. H. and Stoskopf, M. K. and Miller, E. N. and Welte, S. C. and Berkhoff, J. E. and Degernes, L. A. and Fleming, W. J.}, year={1997}, month={Mar}, pages={20–24} }
 @article{ley_berkhoff_levisohn_1997, title={Molecular epidemiologic investigations of Mycoplasma gallisepticum conjunctivitis in songbirds by random amplified polymorphic DNA analyses}, volume={3}, ISSN={["1080-6040"]}, DOI={10.3201/eid0303.970318}, abstractNote={An ongoing outbreak of conjunctivitis in free-ranging house finches (Carpodacus mexicanus) began in 1994 in the eastern United States. Bacterial organisms identified as Mycoplasma gallisepticum (MG) were isolated from lesions of infected birds. MG was also isolated from a blue jay (Cyanocitta cristata) that contracted conjunctivitis after being housed in a cage previously occupied by house finches with conjunctivitis, and from free-ranging American goldfinches (Carduelis tristis) in North Carolina in 1996. To investigate the molecular epidemiology of this outbreak, we produced DNA fingerprints of MG isolates by random amplification of polymorphic DNA (RAPD). We compared MG isolates from songbirds examined from 1994 through 1996 in 11 states, representing three host species, with vaccine and reference strains and with contemporary MG isolates from commercial poultry. All MG isolates from songbirds had RAPD banding patterns identical to each other but different from other strains and isolates tested. These results indicate that the outbreak of MG in songbirds is caused by the same strain, which suggests a single source; the outbreak is not caused by the vaccine or reference strains analyzed; and MG infection has not been shared between songbirds and commercial poultry.}, number={3}, journal={EMERGING INFECTIOUS DISEASES}, author={Ley, DH and Berkhoff, JE and Levisohn, S}, year={1997}, pages={375–380} }
 @article{noormohammadi_markham_whithear_walker_gurevich_ley_browning_1997, title={Mycoplasma synoviae has two distinct phase variable major membrane antigens, one of which is a putative hemagglutinin}, volume={65}, number={7}, journal={Infection and Immunity}, author={Noormohammadi, A. H. and Markham, P. F. and Whithear, K. G. and Walker, I. D. and Gurevich, V. A. and Ley, D. H. and Browning, G. F.}, year={1997}, pages={2542–2547} }
 @article{hoffman_luttrell_davidson_ley_1997, title={Mycoplasmas in wild turkeys living in association with domestic fowl}, volume={33}, ISSN={["1943-3700"]}, DOI={10.7589/0090-3558-33.3.526}, abstractNote={One hundred and nineteen Merriam's wild turkeys (Meleagris gallopavo merriami) and 31 domestic chickens coexisting on a ranch in west-central Colorado (USA) were surveyed for mycoplasmosis by serologic and cultural methods. Although no clinical signs were apparent in any wild turkeys tested, 51 (43%) had positive rapid plate agglutination (RPA) reactions for M. gallisepticum (MG) and/or M. synoviae (MS); 37% of 56 adults and 48% of 63 subadults were classified as positive reactors to MG and/or MS. No turkeys tested in 1992 (n = 61) and 17 (29%) of 58 turkeys tested in 1993 were RPA-positive for M. meleagridis (MM). Hemagglutination inhibition (HI) test results were negative for MG, MS and MM as were most enzyme-linked immunosorbent assay (ELISA) test reactions (MG = 99%, MS = 93%, MM = 87%). Immunoblotting showed mild to moderate reactivity to MG proteins in 49% of 41 samples tested. Most chickens were strongly positive for MS by RPA (81%), HI (58%) and ELISA (87%); 48% also were positive for MG by RPA but all were MG-negative by HI and ELISA. No pathogenic mycoplasmas were isolated from either group of birds. Mycoplasma gallopavonis was commonly identified from the wild turkeys, and M. gallinaceum was isolated from both the chickens and wild turkeys. In a transmission study conducted in 1994, disease-free domestic turkeys failed to seroconvert when co-housed with wild turkeys from this population that were RPA-positive for MG. Collectively, the results of this study were inconclusive regarding the status of pathogenic mycoplasmas within this wild turkey population.}, number={3}, journal={JOURNAL OF WILDLIFE DISEASES}, author={Hoffman, RW and Luttrell, MP and Davidson, WR and Ley, DH}, year={1997}, month={Jul}, pages={526–535} }
 @article{ley_mclaren_miles_barnes_miller_franz_1997, title={Transmissibility of live Mycoplasma gallisepticum vaccine strains ts-11 and 6/85 from vaccinated layer pullets to sentinel poultry}, volume={41}, ISSN={["0005-2086"]}, DOI={10.2307/1592459}, abstractNote={In separate trials, layer pullets were vaccinated with Mycoplasma gallisepticum (MG) strain 6/85 or strain ts-11 commercially produced live vaccines. For a 15-wk postvaccination (PV) period, vaccinates were commingled with unvaccinated pullets and were in indirect contact with sentinel groups of pullets, broiler breeders, turkey breeders, or meat turkeys in adjoining pens. Infectivity and transmissibility of vaccine strains were determined by tracheal culture and serology at 1 wk followed by 3-wk intervals PV. Strain 6/85 was recovered from 0%-20% of vaccinates, but not from commingled pullets or sentinel birds. Strain ts-11 was recovered from 60%-90% of vaccinates and 0%-40% of commingled pullets but not from any of the sentinel birds. No birds in the 6/85 vaccine trial tested positive for MG antibodies by serology. MG enzyme-linked immunosorbent assays detected positive responses in ts-11 vaccinates (range = 10%-70%) at 42, 63, 84, and 105 days PV, and commingled pullets (10%) at 84 and 105 days PV. MG serum plate agglutination tests detected positive responses in 90% and 20% of ts-11 vaccinates at 42 and 105 days PV, respectively, and commingled pullets (10%) at day 42 PV. Clinical signs, morbidity, or mortality suggestive of pathogenic MG infection were not observed in any bird during either trial, and no gross lesions were observed at necropsy. Random amplified polymorphic DNA analysis was capable of distinguishing each of the vaccinal strains 6/85 and ts-11 from each other by their distinct DNA banding patterns.}, number={1}, journal={AVIAN DISEASES}, author={Ley, DH and McLaren, JM and Miles, AM and Barnes, HJ and Miller, SH and Franz, G}, year={1997}, pages={187–194} }
 @article{ley_berkhoff_mclaren_1996, title={Mycoplasma gallisepticum isolated from house finches (Carpodacus mexicanus) with conjunctivitis}, volume={40}, ISSN={["0005-2086"]}, DOI={10.2307/1592250}, abstractNote={An epornitic of conjunctivitis in free-flying house finches (Carpodacus mexicanus) occurred in several mid-Atlantic and eastern states of the USA in 1994. Clinical signs and gross lesions ranged from mild to severe unilateral or bilateral conjunctival swelling with serous to mucopurulent drainage and nasal exudate. Microscopic lesions consisted of chronic lymphoplasmacytic conjunctivitis, rhinitis, and sinusitis. Notably slow-growing mycoplasmas were isolated from conjunctival and/or infraorbital sinus swabs from clinically affected birds. Isolates were identified as Mycoplasma gallisepticum (MG) by direct immunofluorescence and DNA probe-based polymerase chain reactions. These findings suggest that MG is the likely etiology for this epornitic of conjunctivitis in house finches.}, number={2}, journal={AVIAN DISEASES}, author={Ley, DH and Berkhoff, JE and McLaren, JM}, year={1996}, pages={480–483} }
 @article{ley_avakian_berkhoff_1993, title={CLINICAL MYCOPLASMA-GALLISEPTICUM INFECTION IN MULTIPLIER BREEDER AND MEAT TURKEYS CAUSED BY F-STRAIN - IDENTIFICATION BY SODIUM DODECYL-SULFATE POLYACRYLAMIDE-GEL ELECTROPHORESIS, RESTRICTION-ENDONUCLEASE ANALYSIS, AND THE POLYMERASE CHAIN-REACTION}, volume={37}, ISSN={["1938-4351"]}, DOI={10.2307/1592041}, abstractNote={In February 1991, a flock of North Carolina multiplier breeder turkeys experienced respiratory signs, sinusitis, airsacculitis, and increased mortality. Mycoplasma gallisepticum (MG) was isolated, and appropriate control measures were initiated. Ultimately, this outbreak involved several breeder flocks of an integrated turkey production company before the last infected flock was identified in May 1991. During this time, MG was also isolated from a flock of commercial layer-type chickens raised as pullets in close proximity to the index turkey flock. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and restriction endonuclease analysis indicated that these isolates were identical to each other and to examples of the vaccinal F strain. Additionally, MG isolates from the affected turkey breeder and layer flocks were identified as MG F strain by use of an F strain-specific DNA probe and polymerase chain reaction. A separate outbreak of MG disease in several meat-turkey flocks of a Midwest producer/processor yielded isolates identified as F strain by the polymerase chain reaction. These studies demonstrated: 1) the utility of newer technologies for disease outbreak investigations; and 2) the potential of MG F strain to cause disease in breeder and meat turkeys under field conditions.}, number={3}, journal={AVIAN DISEASES}, author={LEY, DH and AVAKIAN, AP and BERKHOFF, JE}, year={1993}, pages={854–862} }
 @article{ley_flammer_cowen_whitt_1993, title={Performance characteristics of diagnostic tests for avian chlamydiosis}, volume={7}, DOI={10.2307/27671089}, number={4}, journal={Journal of the Association of Avian Veterinarians}, author={Ley, D. H. and Flammer, K. and Cowen, P. and Whitt, D.}, year={1993}, pages={203} }
 @article{ley_avakian_1992, title={AN OUTBREAK OF MYCOPLASMA-SYNOVIAE INFECTION IN NORTH-CAROLINA TURKEYS - COMPARISON OF ISOLATES BY SODIUM DODECYL-SULFATE POLYACRYLAMIDE-GEL ELECTROPHORESIS AND RESTRICTION ENDONUCLEASE ANALYSIS}, volume={36}, ISSN={["1938-4351"]}, DOI={10.2307/1591763}, abstractNote={Mycoplasma synoviae (MS) isolates made in 1988-89 from turkey flocks in North Carolina, Missouri, and Ontario, Canada, were compared with each other and MS reference strains (WVU-1853, F10-2AS, Neb-3S, and K1968) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of cell proteins and restriction endonuclease analysis (REA) of DNA. SDS-PAGE and REA indicated considerable homology among MS reference strains and recent field isolates. However, sufficient differences were resolved to identify the MS reference strains as different from each other and the field isolates, and to classify seven of nine recent field isolates as a cluster of nearly identical strains. The results suggest that flocks infected with members of the cluster were epizootiologically associated, possibly by a common or point source of infection.}, number={3}, journal={AVIAN DISEASES}, author={LEY, DH and AVAKIAN, AP}, year={1992}, pages={672–678} }