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.

Evolution and Cryo-electron Microscopy Capsid Structure of a North American Bat Adenovirus and Its Relationship to Other Mastadenoviruses.

Since the first description of adenoviruses in bats in 2006, a number of micro- and megabat species in Europe, Africa, and Asia have been shown to carry a wide diversity of adenoviruses. Here, we report on the evolutionary, biological, and structural characterization of a novel bat adenovirus (BtAdV) recovered from a Rafinesque's big-eared bat (Corynorhinus rafinesquii) in Kentucky, USA, which is the first adenovirus isolated from North American bats. This virus (BtAdV 250-A) exhibits a close phylogenetic relationship with Canine mastadenovirus A (CAdV A), as previously observed with other BtAdVs. To further investigate the relationships between BtAdVs and CAdVs, we conducted mass spectrometric analysis and single-particle cryo-electron microscopy reconstructions of the BtAdV 250-A capsid and also analyzed the in vitro host ranges of both viruses. Our results demonstrate that BtAdV 250-A represents a new mastadenovirus species that, in contrast to CAdV, has a unique capsid morphology that contains more prominent extensions of protein IX and can replicate efficiently in a phylogenetically diverse range of species. These findings, in addition to the recognition that both the genetic diversity of BtAdVs and the number of different bat species from disparate geographic regions infected with BtAdVs appears to be extensive, tentatively suggest that bats may have served as a potential reservoir for the cross-species transfer of adenoviruses to other hosts, as theorized for CAdV. IMPORTANCE: Although many adenoviruses are host specific and likely codiverged with their hosts over millions of years, other adenoviruses appear to have emerged through successful cross-species transmission events on more recent time scales. The wide geographic distribution and genetic diversity of adenoviruses in bats and their close phylogenetic relationship to Canine mastadenovirus A (CAdV A) has raised important questions about how CAdV A, and possibly other mammalian adenoviruses, may have emerged. Although most adenoviruses tend to cause limited disease in their natural hosts, CAdV A is unusual in that it may cause high morbidity and sometimes fatal infections in immunocompetent hosts and is thus an important pathogen of carnivores. Here, we performed a comparative evolutionary and structural study of representative bat and canine adenoviruses to better understand the relationship between these two viral groups.

Parvovirus Capsid Structures Required for Infection: Mutations Controlling Receptor Recognition and Protease Cleavages.

Parvovirus capsids are small but complex molecular machines responsible for undertaking many of the steps of cell infection, genome packing, and cell-to-cell as well as host-to-host transfer. The details of parvovirus infection of cells are still not fully understood, but the processes must involve small changes in the capsid structure that allow the endocytosed virus to escape from the endosome, pass through the cell cytoplasm, and deliver the single-stranded DNA (ssDNA) genome to the nucleus, where viral replication occurs. Here, we examine capsid substitutions that eliminate canine parvovirus (CPV) infectivity and identify how those mutations changed the capsid structure or altered interactions with the infectious pathway. Amino acid substitutions on the exterior surface of the capsid (Gly299Lys/Ala300Lys) altered the binding of the capsid to transferrin receptor type 1 (TfR), particularly during virus dissociation from the receptor, but still allowed efficient entry into both feline and canine cells without successful infection. These substitutions likely control specific capsid structural changes resulting from TfR binding required for infection. A second set of changes on the interior surface of the capsid reduced viral infectivity by >100-fold and included two cysteine residues and neighboring residues. One of these substitutions, Cys270Ser, modulates a VP2 cleavage event found in ∼10% of the capsid proteins that also was shown to alter capsid stability. A neighboring substitution, Pro272Lys, significantly reduced capsid assembly, while a Cys273Ser change appeared to alter capsid transport from the nucleus. These mutants reveal additional structural details that explain cell infection processes of parvovirus capsids. IMPORTANCE: Parvoviruses are commonly found in both vertebrate and invertebrate animals and cause widespread disease. They are also being developed as oncolytic therapeutics and as gene therapy vectors. Most functions involved in infection or transduction are mediated by the viral capsid, but the structure-function correlates of the capsids and their constituent proteins are still incompletely understood, especially in relation to identifying capsid processes responsible for infection and release from the cell. Here, we characterize the functional effects of capsid protein mutations that result in the loss of virus infectivity, giving a better understanding of the portions of the capsid that mediate essential steps in successful infection pathways and how they contribute to viral infectivity.

A RETROSPECTIVE STUDY OF CAUSES OF SKIN LESIONS IN WILD TURKEYS (MELEAGRIS GALLOPAVO) IN THE EASTERN USA, 1975-2013.

Skin lesions of Wild Turkeys ( Meleagris gallopavo ) are a common cause of concern to wildlife biologists and the general public and are a frequent reason for submission to diagnostic laboratories. The purpose of this retrospective study is to evaluate the causes, occurrence, and epidemiologic patterns of skin lesions in Wild Turkeys in the eastern US. Skin lesions were diagnosed in 30% (n=199) of the 660 Wild Turkey samples submitted to the Southeastern Cooperative Wildlife Disease Study diagnostic service from 1975 to 2013. Avian pox was the most frequent cause of skin lesions (66%, n=131), followed by bacterial dermatitis (22%, n=44), ectoparasitism-related dermatitis (3%, n=6), fungal dermatitis (2.5%, n=5), and neoplasia (2.0%, n=4). Although the gross appearance of skin lesions is often insufficient to determine the etiology, the anatomic distribution of lesions and temporal occurrence of certain diseases may offer insights into likely causes. Cases with lesions involving or restricted to the head and neck were much more likely to be caused by avian pox than other etiologies. Similarly, lesions restricted to the feet were more likely to be of bacterial origin. Skin lesions observed in the fall and winter were more likely to be caused by avian pox, whereas bacterial dermatitis was more frequently observed in the spring and summer. This retrospective study provides a summary of the causes of skin lesions in Wild Turkeys and serves as a useful reference to diagnosticians and biologists when evaluating Wild Turkeys with skin lesions.

Screening wild and semi-free ranging great apes for putative sexually transmitted diseases: Evidence of Trichomonadidae infections.

Sexually transmitted diseases (STDs) can persist endemically, are known to cause sterility and infant mortality in humans, and could have similar impacts in wildlife populations. African apes (i.e., chimpanzees, bonobos, and to a lesser extent gorillas) show multi-male mating behavior that could offer opportunities for STD transmission, yet little is known about the prevalence and impact of STDs in this endangered primate group. We used serology and PCR-based detection methods to screen biological samples from wild and orphaned eastern chimpanzees and gorillas (N = 172 individuals, including adults, and juveniles) for four classes of pathogens that either commonly cause human STDs or were previously detected in captive apes: trichomonads, Chlamydia spp., Treponema pallidum (syphilis and yaws), and papillomaviruses. Based on results from prior modeling and comparative research, we expected STD prevalence to be highest in females versus males and in sexually mature versus immature individuals. All samples were negative for Chlamydia, Treponema pallidum, and papillomaviruses; however, a high percentage of wild chimpanzee urine and fecal samples showed evidence of trichomonads (protozoa). Analysis revealed that females were more likely than males to have positive urine-but not fecal-samples; however, there was no evidence of age (sexual maturity) differences in infection status. Sequence analysis of chimpanzee trichomonad samples revealed a close relationship to previously described trichomonads within the genus Tetratrichomonas. Phylogenetic comparisons to archived sequences from multiple vertebrate hosts suggests that many of the chimpanzee parasites from our study are likely transmitted via fecal-oral contact, but the transmission of some Tetratrichomonas sequence-types remains unknown and could include sexual contact. Our work emphasizes that only a fraction of infectious agents affecting wild apes are presently known to science, and that further work on great ape STDs could offer insights for the management of endangered great apes and for understanding human STD origins.

Molecular Surveillance for Lymphoproliferative Disease Virus in Wild Turkeys (Meleagris gallopavo) from the Eastern United States.

Lymphoproliferative disease virus (LPDV) is a poorly understood, oncogenic avian retrovirus of domestic turkeys that has historically been restricted to Europe and Israel. However, a recent study reported LPDV in multiple wild turkey diagnostic cases from throughout the eastern United States of America (USA). To better understand the distribution of LPDV in the eastern USA, we surveyed 1,164 reportedly asymptomatic hunter-harvested wild turkeys from 17 states for the presence of LPDV proviral DNA by PCR. In total, 564/1,164 (47%) turkeys were positive for LPDV. Wild turkeys from each state had a relatively high prevalence of LPDV, although statewide prevalence varied from 26 to 83%. Phylogenetic analysis revealed two major clades of LPDV in the USA, although one was at a low frequency suggesting restricted transmission, as well as significant clustering by state of isolation. To determine the best tissue to target for diagnostic purposes, liver, spleen, and bone marrow were tested from a subset of 15 hunter-harvested wild turkeys and 20 wild turkey diagnostic cases. Overall, bone marrow provided the highest level of detection for both hunter-harvested turkeys and diagnostic cases. The sensitivity of LPDV detection between tissues was not significantly different for diagnostic cases, but was for hunter-harvested birds. These results indicate that LPDV infection is common and widespread in wild turkey populations throughout the eastern USA, even without overt signs of disease.

Avian oncogenesis induced by lymphoproliferative disease virus: a neglected or emerging retroviral pathogen?

Lymphoproliferative disease virus (LPDV) is an exogenous oncogenic retrovirus that induces lymphoid tumors in some galliform species of birds. Historically, outbreaks of LPDV have been reported from Europe and Israel. Although the virus has previously never been detected in North America, herein we describe the widespread distribution, genetic diversity, pathogenesis, and evolution of LPDV in the United States. Characterization of the provirus genome of the index LPDV case from North America demonstrated an 88% nucleotide identity to the Israeli prototype strain. Although phylogenetic analysis indicated that the majority of viruses fell into a single North American lineage, a small subset of viruses from South Carolina were most closely related to the Israeli prototype. These results suggest that LPDV was transferred between continents to initiate outbreaks of disease. However, the direction (New World to Old World or vice versa), mechanism, and time frame of the transcontinental spread currently remain unknown.

Gene duplication and phylogeography of North American members of the Hart Park serogroup of avian rhabdoviruses.

Flanders virus (FLAV) and Hart Park virus (HPV) are rhabdoviruses that circulate in mosquito-bird cycles in the eastern and western United States, respectively, and constitute the only two North American representatives of the Hart Park serogroup. Previously, it was suggested that FLAV is unique among the rhabdoviruses in that it contains two pseudogenes located between the P and M genes, while the cognate sequence for HPV has been lacking. Herein, we demonstrate that FLAV and HPV do not contain pseudogenes in this region, but encode three small functional proteins designated as U1-U3 that apparently arose by gene duplication. To further investigate the U1-U3 region, we conducted the first large-scale evolutionary analysis of a member of the Hart Park serogroup by analyzing over 100 spatially and temporally distinct FLAV isolates. Our phylogeographic analysis demonstrates that although FLAV appears to be slowly evolving, phylogenetically divergent lineages co-circulate sympatrically.

Infectious canine hepatitis in a gray fox (Urocyon cinereoargenteus).

A free-ranging adult male gray fox (Urocyon cinereoargenteus) with moderate diarrhea and thick ocular mucus discharge was examined postmortem. Microscopically, the fox had intranuclear inclusion bodies within hepatocytes. Canine adenovirus-1 was identified by polymerase chain reaction (PCR) and nucleotide sequencing. To our knowledge, this is the first report of clinical infectious canine hepatitis in a gray fox.