Experimental infection of domestic turkeys with lymphoproliferative disease virus of North American origin.

Lymphoproliferative disease virus (LPDV) was first documented in wild turkeys in North America in 2009. LPDV infection is often subclinical but can manifest as lymphoid proliferation or round cell neoplasia. Despite high prevalence across many sampled areas corresponding to declining populations of wild turkeys, knowledge regarding LPDV pathogenesis, risk factors for disease development, and associated impacts on population dynamics are unknown. To understand transmission, viral shedding, and tissue tropism, we inoculated 21 domestic turkeys via the oral cavity, crop, nasal cavity, subcutis, or coelomic cavity. For 12 weeks, oropharyngeal swabs, cloacal swabs, and whole blood were collected weekly. At 1 week postinoculation, 3 turkeys (3/21; 14%) had detectable LPDV proviral DNA in blood by polymerase chain reaction, and 10 developed DNAemia (50%; 10/20) by 12 weeks. LPDV proviral DNA was intermittently detected in oropharyngeal and cloacal swabs. Splenomegaly was the most consistent gross finding in DNAemic birds (8/11; 73%). Lymphoid hyperplasia in the spleen was the most significant microscopic finding (9/11; 82%). Three turkeys (3/11; 27%) developed round cell neoplasia characterized by sheets of pleomorphic, round to polygonal cells in the adrenal gland, bone marrow, skin, small intestine, and/or spleen. LPDV was detected in the spleen and bone marrow from all turkeys with DNAemia and all neoplasms. Our study establishes that infection and disease with North American LPDV from wild turkeys can be experimentally reproduced in domestic turkeys, laying the groundwork for future investigations into LPDV pathogenesis, development of diagnostic techniques, and understanding the impacts of LPDV on wild turkey populations.

Sand Enteropathy in a Free-Ranging Brown Pelican (Pelecanus occidentalis) from Florida, USA.

A subadult Brown Pelican (Pelecanus occidentalis) was found dead near a fishing pier in Florida, US. Necropsy revealed abundant sand accumulation throughout the intestines. Fibrinous coelomitis with isolation of mixed bacteria, including Enterobacter cloacae complex, suggests secondary intestinal compromise. Sand ingestion might reflect geophagia, environmental hardships, or age-related diving inexperience.

Case report: Disseminated larval trematodiasis caused by Clinostomum marginatum in a green tree frog (Hyla cinerea).

Clinostomum spp. are common parasites of piscivorous birds. Metacercaria are typically observed in the muscles or just under the skin of fish and rarely amphibians. We describe an unusually severe case of Clinostomum marginatum infection in an adult female green tree frog (Hyla cinerea) from Georgia (USA). The frog was found in November 2015 with a high number (>250) of widely disseminated, raised, subcutaneous nodules. The frog died in December. At necropsy, it was emaciated, and the skin was covered in raised uniform, tan-green, subcutaneous, ∼2-3 mm diameter nodules. Each nodule contained 1-3 C. marginatum metacercariae. Microscopically, high numbers of trematodes were within subcutaneous tissues and in coelomic and oral cavities, lung, liver, kidney, ovary, orbit and calvarium. Small to large numbers of lymphocytes and melanomacrophages were in connective tissues and epidermis. A 732 bp region of COI was 98.8-99.8% similar to numerous sequences of C. marginatum and, phylogenetically it grouped with these C. marginatum sequences. The ITS-1 region was 100% similar to a C. marginatum sample from a great egret (Ardea alba) from Mississippi. This report represents a novel finding of severe trematodiasis in a free-ranging amphibian with C. marginatum infection.

Health Assessment of Adult Male Eastern Wild Turkeys (Meleagris gallopavo silvestris) from Western Kentucky, USA.

Wild turkeys (Meleagris gallopavo) are an important game species throughout the geographic range. Populations throughout multiple regions of the US have been declining, including in Kentucky, US, raising concerns among managers and resource users. To better understand the overall population health, we performed postmortem examinations and targeted pathogen, mineral, and toxicant testing on 36 adult male, apparently healthy, wild turkeys that were hunter harvested in western Kentucky during April 2018. We found that birds were in fair to good nutritional condition with no significant gross or microscopic lesions. Ticks (Amblyomma spp.) and lice (three species) were present on 94 and 31% of birds, respectively. We commonly detected intestinal nematodes and cestodes and found coccidian oocysts in 39% and capillarid eggs in 6% of birds. The prevalences of lymphoproliferative disease virus and reticuloendotheliosis virus were 39 and 11%, respectively. Spleen samples tested with PCR were positive for Borrelia burgdorferi, Haemoproteus sp., and Leucocytozoon sp. in 11, 83, and 3%, respectively. Based on a subjective histologic assessment of testis tissues, most birds had widespread and abundant sperm present. Mineral analysis and broad toxicant screening on liver samples from 32 turkeys were unremarkable. Further work is needed to assess potential population risk factors and to determine individual- and population-level impacts of pathogens on adults and poults.

Causes of morbidity and mortality in wild cottontail rabbits in the eastern United States, 2013-2022.

Interest in causes of mortality of free-ranging, native North American lagomorphs has grown with the emergence of rabbit hemorrhagic disease virus 2 (RHDV2). Over the years 2013-2022, the Southeastern Cooperative Wildlife Disease Study received 119 Sylvilagus spp. case submissions from the central and eastern United States, comprising 147 rabbits. Most (86%) of these submissions occurred after detecting RHDV2 in the United States in 2020. Laboratory data from these rabbits were retrospectively evaluated for major causes, contributors to mortality, and pathogen detections. Gross and histologic examination was performed for 112 rabbits. Common primary causes of death included trauma (n = 49), bacterial disease (n = 31), emaciation (n = 6), and parasitism (n = 6). Among the 32 rabbits with bacterial disease, 12 were diagnosed with tularemia and 7 with pasteurellosis. Rabbits with pasteurellosis had disseminated abscessation, septicemia, and/or polyserositis. Less commonly, cutaneous fibroma (n = 2), notoedric mange (n = 2), encephalitozoonosis (n = 2), neoplasia (round-cell sarcoma; n = 1), and congenital abnormalities (n = 1) were diagnosed. RHDV2 was not detected in 123 rabbits tested. Although RHDV2 has not been detected in wild lagomorphs in the eastern United States, detections in domestic rabbits from the region emphasize the need for continued surveillance. Furthermore, continued surveillance for Francisella tularensis informs public health risk. Overall, increased knowledge of Sylvilagus spp. health furthers our understanding of diseases affecting these important prey and game species.

Surveillance for Selected Pathogens and Parasites of Northern Bobwhite (Colinus virginianus) from Western Oklahoma, USA, 2018-20.

The Northern Bobwhite (Colinus virginianus) has been undergoing a range-wide population decline. Potential causes for declines across its historic range have been investigated for decades and include habitat loss and fragmentation and a variety of parasitic and infectious diseases. Although there have been studies on bobwhite ecology in Oklahoma, USA, relatively little is known about parasites and pathogens in the region. We evaluated the health of free-ranging bobwhites from nine sites in western Oklahoma. From 2018 to 2020, 206 bobwhites were evaluated for gross and microscopic lesions and tested for selected pathogens. In general, bobwhites were in good nutritional condition with ample muscle mass and fat stores. No significant gross lesions were observed in any bobwhite and no significant histologic lesions were detected in a subset. There was no evidence of infection with or exposure to reticuloendotheliosis virus, West Nile virus, respiratory Mycoplasmataceae species, Pasteurella multocida, intestinal Eimeria spp., or oral Trichomonas spp. Several pathogens of potential concern were detected, including avian adenovirus (8.6%), Toxoplasma gondii (2.3%), and haemosporidians (a Haemoproteus sp. (1.5%), Leucocytozoon schoutedeni (1.5%), and Plasmodium homopolare haplotype 2 [lineage LAIRI01; 3.6%]). Physaloptera sp. (12%) and Sarcocystis sp. (1%) were detected in the breast muscle. Low intraspecific genetic diversity was noted for Physaloptera sp., and sequences were most similar to Physaloptera sequences from bobwhites and grasshoppers (Orthoptera) in Texas. Low intensities of chewing lice, chiggers, and ticks were observed. A subset of bobwhites had evidence of exposure to selected toxicants and heavy metals; a small number had low levels of iron, manganese, zinc, molybdenum, and copper, which were not considered diagnostically relevant. In general, bobwhites from western Oklahoma appeared to be in good health with a low diversity of pathogens detected, but future work is needed to understand potentially changing disease risks for this population.

High Prevalence and Broad Distribution of Trichomonas gypaetinii in Bald Eagles (Haliaceetus leucocephalus) in the USA.

Trichomonas gypaetinii was detected in 117 (88%) of 133 Bald Eagles (Haliaceetus leucocephalus) and in 0 of 7 Golden Eagles (Aquila chrysaetos) in the USA, with no sex or age prevalence difference. All eagles lacked associated lesions. This study indicated that T. gypaetinii is common and widespread in Bald Eagles, but rarely associated with disease.

Metagenomics for Pathogen Detection During a Mass Mortality Event in Songbirds.

Mass mortality events in wildlife can be indications of an emerging infectious disease. During the spring and summer of 2021, hundreds of dead passerines were reported across the eastern US. Birds exhibited a range of clinical signs including swollen conjunctiva, ocular discharge, ataxia, and nystagmus. As part of the diagnostic investigation, high-throughput metagenomic next-generation sequencing was performed across three molecular laboratories on samples from affected birds. Many potentially pathogenic microbes were detected, with bacteria forming the largest proportion; however, no singular agent was consistently identified, with many of the detected microbes also found in unaffected (control) birds and thus considered to be subclinical infections. Congruent results across laboratories have helped drive further investigation into alternative causes, including environmental contaminants and nutritional deficiencies. This work highlights the utility of metagenomic approaches in investigations of emerging diseases and provides a framework for future wildlife mortality events.