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Recent studies have correlated anticoagulant rodenticide exposure to the development of mange in wild felids. However, a causative association between anticoagulant exposure and the onset of mange or immune dysfunction that may increase susceptibility of wild felids to manage has not been established. To investigate the potential connection between anticoagulant rodenticide exposure and immune dysfunction, specific-pathogen-free domestic cats were exposed to brodifacoum over a six-week period and vaccinated with irrelevant antigens at different points during the course of the experiment to assess recall and direct immune responses. Measures of immune response included delayed-type hypersensitivity tests and cell proliferation assays. IgE and antigen-specific antibodies were quantified via ELISA assays. No cats developed coagulopathies despite having detectable levels of brodifacoum in the blood. Brodifacoum cats had significant decreases in the production of certain cytokines including IL-6 and IL-4. The results of this study suggest that cats may be less susceptible to anticoagulant rodenticide induced coagulopathy and that the effects of environmentally realistic brodifacoum exposure on humoral and cell-mediated immunity against foreign antigen exposures in domestic cats are minimal.

Characterizes the genome of Borna disease virus (BDV), the cause of a rare neurological disease found in horses and sheep, identified through the construction of a subtractive complementary DNA expression library. Isolation of hybridized clone; Nucleotide sequence analysis; In vitro transcription and translation; Recognition of protein by antibodies; Implications of BDV-specific clone.

Borna disease virus (BDV), which seems to be distinct from all other known viruses, exhibits a unique mechanism of pathogenesis. This review highlights several aspects of the biology of infection with this virus and summarizes the preliminary characterization of the agent. Studies on BDV may help to illuminate several important areas of neurobiology, including the mechanisms regulating the replication of a new type of RNA virus in the nuclei of neural cells, the neuroinvasiveness and neurotropism of such viruses, their T cell-mediated immunopathology, tolerance in newborn animals to persistent viral infection of the central nervous system, and behavioral diseases and eating disorders induced by such agents. [ABSTRACT FROM PUBLISHER]

• Felis catus genomes harbor multiple copies of endogenous feline leukemia virus (enFeLV) • Lynx rufus genomes do not harbor enFeLV • F. catus and L. rufus hybrids would have at least 1 copy enFeLV per cell • The contested animal lacks any enFeLV • The contested animal is not a domestic cat hybrid In October 2018, Colorado Parks and Wildlife seized an animal believed to be an illegally possessed bobcat. The owner claimed the animal was a bobcat/domestic cat hybrid, exempted from license requirements. Burden of proof lay with CPW to determine the lineage of the animal. Commercial microsatellite arrays and DNA barcoding have not been developed for identification of bobcat/domestic cat hybrids, and limited time and resources prevented development of such tests for this application. Instead, we targeted endogenous feline leukemia virus (enFeLV) to quickly and inexpensively demonstrate the absence of domestic cat DNA in the contested animal. Using this assay, we were able to confirm that the contested animal lacked enFeLV, and therefore was not a domestic cat hybrid. [ABSTRACT FROM AUTHOR]

Abstract Background Feline immunodeficiency virus (FIV) naturally infects multiple species of cat and is related to human immunodeficiency virus in humans. FIV infection causes AIDS-like disease and mortality in the domestic cat (Felis catus) and serves as a natural model for HIV infection in humans. In African lions (Panthera leo) and other exotic felid species, disease etiology introduced by FIV infection are less clear, but recent studies indicate that FIV causes moderate to severe CD4 depletion. Results In this study, comparative genomic methods are used to evaluate the full proviral genome of two geographically distinct FIV subtypes isolated from free-ranging lions. Genome organization of FIVPle subtype B (9891 bp) from lions in the Serengeti National Park in Tanzania and FIVPle subtype E (9899 bp) isolated from lions in the Okavango Delta in Botswana, both resemble FIV genome sequence from puma, Pallas cat and domestic cat across 5' LTR, gag, pol, vif, orfA, env, rev and 3'LTR regions. Comparative analyses of available full-length FIV consisting of subtypes A, B and C from FIVFca, Pallas cat FIVOma and two puma FIVPco subtypes A and B recapitulate the species-specific monophyly of FIV marked by high levels of genetic diversity both within and between species. Across all FIVPle gene regions except env, lion subtypes B and E are monophyletic, and marginally more similar to Pallas cat FIVOma than to other FIV. Sequence analyses indicate the SU and TM regions of env vary substantially between subtypes, with FIVPle subtype E more related to domestic cat FIVFca than to FIVPle subtype B and FIVOma likely reflecting recombination between strains in the wild. Conclusion This study demonstrates the necessity of whole-genome analysis to complement population/gene-based studies, which are of limited utility in uncovering complex events such as recombination that may lead to functional differences in virulence and pathogenicity. These full-length lion lentiviruses are integral to the advancement of comparative genomics of human pathogens, as well as emerging disease in wild populations of endangered species.

With the exception of human immunodeficiency virus (HIV), which emerged in humans after cross-species transmissions of simian immunodeficiency viruses from nonhuman primates, immunodeficiency viruses of the family Lentiviridae represent species-specific viruses that rarely cross species barriers to infect new hosts. Among the Felidae, numerous immunodeficiency-like lentiviruses have been documented, but only a few cross-species transmissions have been recorded, and these have not been perpetuated in the recipient species. Lentivirus seroprevalence was determined for 79 bobcats (Lynx rufus) and 31 pumas (Puma concolor) from well-defined populations in Southern California. Partial genomic sequences were subsequently obtained from 18 and 12 seropositive bobcats and pumas, respectively. Genotypes were analyzed for phylogenic relatedness and genotypic composition among the study set and archived feline lentivirus sequences. This investigation of feline immunodeficiency virus infection in bobcats and pumas of Southern California provides evidence that cross-species infection has occurred frequently among these animals. The data suggest that transmission has occurred in multiple locations and are most consistent with the spread of the virus from bobcats to pumas. Although the ultimate causes remain unknown, these transmission events may occur as a result of puma predation on bobcats, a situation similar to that which fostered transmission of HIV to humans, and likely represent the emergence of a lentivirus with relaxed barriers to cross-species transmission. This unusual observation provides a valuable opportunity to evaluate the ecological, behavioral, and molecular conditions that favor repeated transmissions and persistence of lentivirus between species. [ABSTRACT FROM AUTHOR]

SARS-CoV-2 rapidly adapts to new hosts following cross-species transmission; this is highly relevant as novel within-host variants have emerged following infection of susceptible wild and domestic animal species. Furthermore, SARS-CoV-2 transmission from animals (e.g., white-tailed deer, mink, domestic cats, and others) back to humans has also been observed, documenting the potential of novel animal-derived variants to infect humans. We investigated SARS-CoV-2 evolution and host-specific adaptation during an outbreak in Amur tigers ( Panthera tigris altaica ), African lions ( Panthera leo ), and spotted hyenas ( Crocuta crocuta ) at Denver Zoo in late 2021. SARS-CoV-2 genomes from longitudinal samples collected from 16 individuals were evaluated for within-host variation and genomic signatures of selection. The outbreak was likely initiated by a single spillover of a rare Delta sublineage subsequently transmitted from tigers to lions to hyenas. Within-host virus populations rapidly expanded and diversified. We detected signatures of purifying and positive selection, including strong positive selection in hyenas and in the nucleocapsid (N) gene in all animals. Four candidate species-specific adaptive mutations were identified: N A254V in lions and hyenas, and ORF1a E1724D, spike T274I, and N P326L in hyenas. These results reveal accelerated SARS-CoV-2 adaptation following host shifts in three non-domestic species in daily contact with humans.

In late 2019, SARS-CoV-2 spilled-over from an animal host into humans, where it efficiently spread, resulting in the COVID-19 pandemic. Through both natural and experimental infections, we learned that many animal species are susceptible to SARS-CoV-2. Importantly, animals in close proximity to humans, including companion, farmed, and those at zoos and aquariums, became infected, and many studies demonstrated transmission to/from humans in these settings. In this study, we first review the literature of SARS-CoV-2 infections in tigers and lions, and compare species, sex, age, virus and antibody detection assay, and types, frequency and length of clinical signs, demonstrating broad heterogeneity amongst infections. We then describe a SARS-CoV-2 outbreak in lions, tigers and hyenas at Denver Zoo in late 2021. Animals were tested for viral RNA (vRNA) for four months. Lions had significantly more viral RNA in nasal swabs than both tigers and hyenas, and many individual lions experienced viral recrudescence after weeks of undetectable vRNA. Infectious virus was correlated with high levels of vRNA and was more likely to be detected earlier during infection. Four months post-infection, all tested animals generated robust neutralizing antibody titers. Animals were infected with Delta lineage AY.20 identical to a variant circulating at less than 1% in Colorado humans at that time, suggesting a single spillover event from an infected human spread within and between species housed at the zoo. Better understanding of epidemiology and susceptibility of SARS-CoV-2 infections in animals is critical to limit the current and future spread and protect animal and human health.

Feline immunodeficiency virus (FIV) is the domestic cat analogue of HIV infection in humans. Both viruses induce oral disease in untreated individuals, with clinical signs that include gingivitis and periodontal lesions. Oral disease manifestations in HIV patients are abated by highly effective combination antiretroviral therapy (cART), though certain oral manifestations persist despite therapy. Microorganisms associated with oral cavity opportunistic infections in patients with HIV cause similar pathologies in cats. To further develop this model, we evaluated characteristics of feline oral health and oral microbiome during experimental FIV infection over an 8-month period following cART. Using 16S metagenomics sequencing, we evaluated gingival bacterial communities at four timepoints in uninfected and FIV-infected cats treated with cART or placebo. Comprehensive oral examinations were also conducted by a veterinary dental specialist over the experimental period. Gingival inflammation was higher in FIV-infected cats treated with placebo compared to cART-treated cats and controls at study endpoint. Oral microbiome alpha diversity increased in all groups, while beta diversity differed among treatment groups, documenting a significant effect of cART therapy on microbiome community composition. This finding has not previously been reported and indicates cART ameliorates immunodeficiency virus-associated oral disease via preservation of oral mucosal microbiota. Further, this study illustrates the value of the FIV animal model for investigations of mechanistic associations and therapeutic interventions for HIV oral manifestations., Competing Interests: Conflict of Interest Statement The authors declare that the research was conducted in the absence of any commercial or financial relationship that could be construed as a potential conflict of interest.

Objective: The purpose of this study was to identify knowledge gaps in the global prevalence of feline immunodeficiency virus (FIV) and to obtain professional opinions and experiences regarding FIV in selected countries. We conducted a literature review of abstracts that reported the prevalence of FIV and interviewed experts in feline medicine and retroviruses from different countries to determine regional perspectives., Methods: A total of 90 articles reporting FIV prevalence as a primary unbiased population-level analysis between 1980 and 2017 were indexed. FIV prevalence, demographics, year and location were analyzed. Statistics were evaluated and compared. In total, 10 experts were interviewed. Results were analyzed for congruence with the findings of the literature review., Results: FIV prevalence was typically in the range of 5-8%, with a global prevalence of 4.7%, and remained largely constant over the reporting period (1980-2017). Over 90% of articles reported greater prevalence in older male cats. More studies were conducted in North America and Europe and reported the lowest prevalence. Expert-estimated prevalence approximated literature review prevalence. Attitudes and recommendations for management were consistent among experts. The limitations of the present review include varying inclusion criteria of cats tested in different studies, variation in testing modalities and the inability to conduct summary statistics across dissimilar cohorts., Conclusions and Relevance: The global prevalence of FIV has not changed since its discovery 40 years ago. Prevalence is higher in older male cats and is lower in North America and Europe than other continents. Experts agree that FIV is not typically a disease of high concern and is often associated with infections of the oral cavity. Vaccination is not typically recommended and has been discontinued in North America. The evaluation of risk factors for FIV progression is useful in managing infections. Recommendations for future research include analyses to determine copathogen and environmental factors that impact progression, assessment of life span impacts and investigations of treatment efficacy and side effects., Competing Interests: Conflict of interestThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Interprofessional Education (IPE) and One Health are two common and overlapping frameworks for teaching collaborative practice. IPE is common at human medical institutions, while One Health is more common in graduate and veterinary programs. The connection between IPE and One Health is still being explored both in scholarship and in real-world professional settings. This prospective, qualitative research study examines the intersection of IPE and One Health at institutions that are members of the Clinical and Translational Science Award (CTSA) One Health Alliance (COHA). COHA consists of veterinary schools partnered with medical institutions through the National Institutes of Health CTSA funding mechanism with the specific goal of advancing the understanding of diseases shared by humans and animals. Twenty-four interviews were conducted with professionals across eight professions. Subjects noted that some of the biggest barriers to IPE education were awareness, accessibility, efficacy, and implementation beyond the classroom. Competency across multiple institutions and a consistent, validated evaluation tool were noted to be lacking. Interviews highlighted a lack of a shared mental model for IPE and One Health across the medical professions, major hurdles for implementation in professional curricula, and a disconnection between bridging IPE and One Health to the workforce and global challenges. Future work in this area may be focused on assessing the IPE and One Health offerings beyond COHA institutions, giving a more holistic understanding on how IPE and One Health are being deployed. One Health can be operationalized through the adoption of IPE principles and practices into curriculum. This research is critical to educate others on current applications, role, and definitions of One Health and IPE. The ultimate goal of this work is to help cultivate transdisciplinary leaders in the human and animal medicine who will have the skills to solve systemic problems., Competing Interests: None., (© 2024 Published by Elsevier B.V.)

People living with human immunodeficiency virus (PLWH) are a significant population globally. Research delineating our understanding of coinfections in PLWH is critical to care for those navigating infection with other pathogens. The recent COVID-19 pandemic underscored the urgent need for studying the effects of SARS-CoV-2 infections in therapy-controlled and uncontrolled immunodeficiency viral infections. This study established the utility of a feline model for the in vivo study of coinfections. Domestic cats are naturally infected with SARS-CoV-2 and Feline Immunodeficiency Virus, a lentivirus molecularly and pathogenically similar to HIV. In this study, comparisons are made between FIV-positive and FIV-negative cats inoculated with SARS-CoV-2 (B.1.617.2.) in an experimental setting. Of the FIV+ cats, three received Zidovudine (AZT) therapy in the weeks leading up to SARS-CoV-2 inoculation, and two did not. SARS-CoV-2 viral RNA was quantified, histopathologic comparisons of respiratory tissues were made, and T-cell populations were analyzed for immune phenotype shifts between groups. CD4+ T lymphocyte responses varied, with FIV+-untreated cats having the poorest CD4+ response to SARS-CoV-2 infection. While all cats had significant pulmonary inflammation, key histopathologic features of the disease differed between groups. Additionally, viral genomic analysis was performed, and results were analyzed for the presence of emerging, absent, amplified, or reduced mutations in SARS-CoV-2 viral RNA after passage through the feline model. Positive selection is noted, especially in FIV+ cats untreated with AZT, and mutations with potential relevance were identified; one FIV+-untreated cat had persistent, increasing SARS-CoV-2 RNA in plasma five days post-infection. These findings and others support the utility of the feline model for studying coinfection in people with HIV and highlight the importance of antiretroviral therapy in clearing SARS-CoV-2 coinfections to minimize transmission and emergence of mutations that may have deleterious effects.

Endogenous retroviruses (ERV) are indicators of vertebrate evolutionary history and play important roles as homeostatic regulators. ERV long terminal repeat (LTR) elements may act as cis-activating promoters or trans-activating enhancer elements modifying gene transcription distant from LTR insertion sites. We previously documented that endogenous feline leukemia virus (FeLV)-LTR copy number variation in individual cats tracks inversely with susceptibility to virulent FeLV disease. To evaluate FeLV-LTR insertion characteristics, we assessed enFeLV-LTR integration site diversity in 20 cats from three genetically distinct populations using a baited linker-mediated PCR approach. We documented 765 individual integration sites unequally represented among individuals. Only three LTR integration sites were shared among all individuals, while 412 sites were unique to a single individual. When primary fibroblast cultures were challenged with exogenous FeLV, we found significantly increased expression of both exogenous and endogenous FeLV orthologs, supporting previous findings of potential exFeLV-enFeLV interactions; however, viral challenge did not elicit transcriptional changes in genes associated with the vast majority of integration sites. This study assesses FeLV-LTR integration sites in individual animals, providing unique transposome genotypes. Further, we document substantial individual variation in LTR integration site locations, even in a highly inbred population, and provide a framework for understanding potential endogenous retroviral element position influence on host gene transcription., (© 2024. The Author(s).)

Background: Rapidly developing tests for emerging diseases is critical for early disease monitoring. In the early stages of an epidemic, when low prevalences are expected, high specificity tests are desired to avoid numerous false positives. Selecting a cutoff to classify positive and negative test results that has the desired operating characteristics, such as specificity, is challenging for new tests because of limited validation data with known disease status. While there is ample statistical literature on estimating quantiles of a distribution, there is limited evidence on estimating extreme quantiles from limited validation data and the resulting test characteristics in the disease testing context., Methods: We propose using extreme value theory to select a cutoff with predetermined specificity by fitting a Pareto distribution to the upper tail of the negative controls. We compared this method to five previously proposed cutoff selection methods in a data analysis and simulation study. We analyzed COVID-19 enzyme linked immunosorbent assay antibody test results from long-term care facilities and skilled nursing staff in Colorado between May and December of 2020., Results: We found the extreme value approach had minimal bias when targeting a specificity of 0.995. Using the empirical quantile of the negative controls performed well when targeting a specificity of 0.95. The higher target specificity is preferred for overall test accuracy when prevalence is low, whereas the lower target specificity is preferred when prevalence is higher and resulted in less variable prevalence estimation., Discussion: While commonly used, the normal based methods showed considerable bias compared to the empirical and extreme value theory-based methods., Conclusions: When determining disease testing cutoffs from small training data samples, we recommend using the extreme value based-methods when targeting a high specificity and the empirical quantile when targeting a lower specificity., (© 2024. The Author(s).)

Dermatophytes are highly infectious fungi that cause superficial infections in keratinized tissues in humans and animals. This group of fungi is defined by their ability to digest keratin and encompasses a wide range of species. We investigated a critical adhesion protein, subtilisin 3, utilized by Microsporum canis during initial stages of infection, analyzing its production and expression under varying growth conditions. Additionally, as this protein must be expressed and produced for dermatophyte infections to occur, we developed and optimized a diagnostic antibody assay targeting this protein. Subtilisin 3 levels were increased in culture when grown in baffled flasks and supplemented with either l-cysteine or cat hair. As subtilisin 3 was also produced in cultures not supplemented with keratin or cysteine, this study demonstrated that subtilisin 3 production is not reliant on the presence of keratin or its derivatives. These findings could help direct future metabolic studies of dermatophytes, particularly during the adherence phase of infections., (© 2023 The Authors. Journal of Basic Microbiology published by Wiley-VCH GmbH.)

Seasonal variation in habitat use and animal behavior can alter host contact patterns with potential consequences for pathogen transmission dynamics. The endangered Florida panther (Puma concolor coryi) has experienced significant pathogen-induced mortality and continues to be at risk of future epidemics. Prior research has found increased panther movement in Florida's dry versus wet seasons, which may affect panther population connectivity and seasonally increase potential pathogen transmission. Our objective was to determine if Florida panthers are more spatially connected in dry seasons relative to wet seasons, and test if identified connectivity differences resulted in divergent predicted epidemic dynamics. We leveraged extensive panther telemetry data to construct seasonal panther home range overlap networks over an 11 year period. We tested for differences in network connectivity, and used observed network characteristics to simulate transmission of a broad range of pathogens through dry and wet season networks. We found that panthers were more spatially connected in dry seasons than wet seasons. Further, these differences resulted in a trend toward larger and longer pathogen outbreaks when epidemics were initiated in the dry season. Our results demonstrate that seasonal variation in behavioral patterns-even among largely solitary species-can have substantial impacts on epidemic dynamics., (© 2023. Springer Nature Limited.)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is notable both for its impact on global public health as well as its well-publicized transmissibility to other species of animals. Infection of incidental animal hosts is concerning because of possible emergence of novel variants due to viral mutation. Species that are susceptible to SARS-CoV-2 include domestic and nondomestic cats, domestic dogs, white-tailed deer, mink, and golden hamsters, among others. We detail possible origins of transmission of SARS-CoV-2 to humans, as well as the ecological and molecular mechanisms needed for the virus to establish infection in humans from animals. We highlight examples of SARS-CoV-2 spillover, spillback, and secondary spillover, demonstrating the breadth in the variability of hosts and current transmission events that have been documented in domestic, captive, and wild animals. Lastly, we turn our focus to the importance of animal hosts as potential reservoirs and sources of variant emergence that can have profound effects on the human population. We note that a One Health approach emphasizing surveillance of animals and humans in certain environments using interdisciplinary collaboration is encouraged to manage disease surveillance, regulation on animal trade and testing, and animal vaccine development that will mitigate further disease outbreaks. These efforts will minimize the spread of SARS-CoV-2 and advance knowledge to prevent the spread of future emerging infectious diseases., Competing Interests: The authors declare no conflict of interest.

Feline Immunodeficiency Virus (FIV) causes progressive immune dysfunction in cats similar to human immunodeficiency virus (HIV) in humans. Although combination antiretroviral therapy (cART) is effective against HIV, there is no definitive therapy to improve clinical outcomes in cats with FIV. This study therefore evaluated pharmacokinetics and clinical outcomes of cART (2.5 mg/kg Dolutegravir; 20 mg/kg Tenofovir; 40 mg/kg Emtricitabine) in FIV-infected domestic cats. Specific pathogen free cats were experimentally infected with FIV and administered either cART or placebo treatments ( n = 6 each) for 18 weeks, while n = 6 naïve uninfected cats served as controls. Blood, saliva, and fine needle aspirates from mandibular lymph nodes were collected to quantify viral and proviral loads via digital droplet PCR and to assess lymphocyte immunophenotypes by flow cytometry. cART improved blood dyscrasias in FIV-infected cats, which normalized by week 16, while placebo cats remained neutropenic, although no significant difference in viremia was observed in the blood or saliva. cART-treated cats exhibited a Th2 immunophenotype with increasing proportions of CD4 + CCR4 + cells compared to placebo cats, and cART restored Th17 cells compared to placebo-treated cats. Of the cART drugs, dolutegravir was the most stable and long-lasting. These findings provide a critical insight into novel cART formulations in FIV-infected cats and highlight their role as a potential animal model to evaluate the impact of cART on lentiviral infection and immune dysregulation.

During early phases of the SARS-CoV-2 epidemic, many research laboratories repurposed their efforts towards developing diagnostic testing that could aid public health surveillance while commercial and public diagnostic laboratories developed capacity and validated large scale testing methods. Simultaneously, the rush to produce point-of-care and diagnostic facility testing resulted in FDA Emergency Use Authorization with scarce and poorly validated clinical samples. Here, we review serologic test results from 186 serum samples collected in early phases of the pandemic (May 2020) from skilled nursing facilities tested with six laboratory-based and two commercially available assays. Serum neutralization titers were used to set cut-off values using positive to negative ratio (P/N) analysis to account for batch effects. We found that laboratory-based receptor binding domain (RBD) binding assays had equivalent or superior sensitivity and specificity compared to commercially available tests. We also determined seroconversion rate and compared with qPCR outcomes. Our work suggests that research laboratory assays can contribute reliable surveillance information and should be considered important adjuncts to commercial laboratory testing facilities during early phases of disease outbreaks.

Spatially heterogeneous landscape factors such as urbanisation can have substantial effects on the severity and spread of wildlife diseases. However, research linking patterns of pathogen transmission to landscape features remains rare. Using a combination of phylogeographic and machine learning approaches, we tested the influence of landscape and host factors on feline immunodeficiency virus (FIV Lru ) genetic variation and spread among bobcats ( Lynx rufus ) sampled from coastal southern California. We found evidence for increased rates of FIV Lru lineage spread through areas of higher vegetation density. Furthermore, single-nucleotide polymorphism (SNP) variation among FIV Lru sequences was associated with host genetic distances and geographic location, with FIV Lru genetic discontinuities precisely correlating with known urban barriers to host dispersal. An effect of forest land cover on FIV Lru SNP variation was likely attributable to host population structure and differences in forest land cover between different populations. Taken together, these results suggest that the spread of FIV Lru is constrained by large-scale urban barriers to host movement. Although urbanisation at fine spatial scales did not appear to directly influence virus transmission or spread, we found evidence that viruses transmit and spread more quickly through areas containing higher proportions of natural habitat. These multiple lines of evidence demonstrate how urbanisation can change patterns of contact-dependent pathogen transmission and provide insights into how continued urban development may influence the incidence and management of wildlife disease., (© The Author(s) 2023. Published by Oxford University Press.)

Feline leukemia virus (FeLV) is a gammaretrovirus with horizontally transmitted and endogenous forms. Domestic cats are the primary reservoir species, but FeLV outbreaks in endangered Florida panthers and Iberian lynxes have resulted in mortalities. To assess prevalence and interspecific/intraspecific transmission, we conducted an extensive survey and phylogenetic analysis of FeLV infection in free-ranging pumas ( n  = 641) and bobcats ( n  = 212) and shelter domestic cats ( n  = 304). Samples were collected from coincident habitats across the United States between 1985 and 2018. FeLV infection was detected in 3.12% of the puma samples, 0.47% of the bobcat samples, and 6.25% of the domestic cat samples analyzed. Puma prevalence varied by location, with Florida having the highest rate of infection. FeLV env sequences revealed variation among isolates, and we identified two distinct clades. Both progressive and regressive infections were identified in cats and pumas. Based on the time and location of sampling and phylogenetic analysis, we inferred 3 spillover events between domestic cats and pumas; 3 puma-to-puma transmissions in Florida were inferred. An additional 14 infections in pumas likely represented spillover events following contact with reservoir host domestic cat populations. Our data provide evidence that FeLV transmission from domestic cats to pumas occurs widely across the United States, and puma-to-puma transmission may occur in genetically and geographically constrained populations. IMPORTANCE Feline leukemia virus (FeLV) is a retrovirus that primarily affects domestic cats. Close interactions with domestic cats, including predation, can lead to the interspecific transmission of the virus to pumas, bobcats, or other feline species. Some infected individuals develop progressive infections, which are associated with clinical signs of disease and can result in mortality. Therefore, outbreaks of FeLV in wildlife, including the North American puma and the endangered Florida panther, are of high conservation concern. This work provides a greater understanding of the dynamics of the transmission of FeLV between domestic cats and wild felids and presents evidence of multiple spillover events and infections in all sampled populations. These findings highlight the concern for pathogen spillover from domestic animals to wildlife but also identify an opportunity to understand viral evolution following cross-species transmissions more broadly.

SARS-CoV-2 (SARS2) infection of a novel permissive host species can result in rapid viral evolution. Data suggest that felids are highly susceptible to SARS2 infection, and species-specific adaptation following human-to-felid transmission may occur. We employed experimental infection and analysis of publicly available SARS2 sequences to observe variant emergence and selection in domestic cats. Three cohorts of cats ( N  = 23) were inoculated with SARS-CoV-2 USA-WA1/2020 or infected via cat-to-cat contact transmission. Full viral genomes were recovered from RNA obtained from nasal washes 1-3 days post-infection and analyzed for within-host viral variants. We detected 118 unique variants at ≥3 per cent allele frequency in two technical replicates. Seventy of these (59 per cent) were nonsynonymous single nucleotide variants (SNVs); the remainder were synonymous SNVs or structural variants. On average, we observed twelve variants per cat, nearly 10-fold higher than what is commonly reported in human patients. We observed signatures of positive selection in the spike protein and the emergence of eleven within-host variants located at the same genomic positions as mutations in SARS2 variant lineages that have emerged during the pandemic. Fewer variants were noted in cats infected from contact with other cats and in cats exposed to lower doses of cultured inoculum. An analysis of ninety-three publicly available SARS2 consensus genomes recovered from naturally infected domestic cats reflected variant lineages circulating in the local human population at the time of sampling, illustrating that cats are susceptible to SARS2 variants that have emerged in humans, and suggesting human-to-felid transmission occurring in domestic settings is typically unidirectional. These experimental results underscore the rapidity of SARS2 adaptation in felid hosts, representing a theoretical potential origin for variant lineages in human populations. Further, cats should be considered susceptible hosts capable of shedding virus during infections occurring within households., (© The Author(s) 2022. Published by Oxford University Press.)

Hepadnaviruses are partially double-stranded DNA viruses that infect a variety of species. The prototypical virus in this family is the human hepatitis B virus, which chronically infects approximately 400 million people worldwide and is a risk factor for progressive liver disease and liver cancer. The first hepadnavirus isolated from carnivores was a domestic cat hepadnavirus (DCH), initially identified in Australia and subsequently detected in cats in Europe and Asia. As with all characterized hepadnaviruses so far, DCH infection has been associated with hepatic disease in its host. Prevalence of this infection in the United States has not been explored broadly. Thus, we utilized conventional and quantitative PCR to screen several populations of domestic cats to estimate DCH prevalence in the United States. We detected DCH DNA in 1 out of 496 animals (0.2%) in the U.S. cohort. In contrast, we detected circulating DCH DNA in 7 positive animals from a cohort of 67 domestic cats from Australia (10.4%), consistent with previous studies. The complete consensus genome of the U.S. DCH isolate was sequenced by Sanger sequencing with overlapping PCR products. An in-frame deletion of 157 bp was identified in the N-terminus of the core open reading frame. The deletion begins at the direct repeat 1 sequence (i.e., the 5' end of the expected double-stranded linear DNA form), consistent with covalently closed circular DNA resultant from illegitimate recombination described in other hepadnaviruses. Comparative genome sequence analysis indicated that the closest described relatives of the U.S. DCH isolate are those previously isolated in Italy. Motif analysis supports DCH using NTCP as an entry receptor, similar to human HBV. Our work indicates that chronic DCH prevalence in the U.S. is likely low compared to other countries.

Identifying drivers of transmission-especially of emerging pathogens-is a formidable challenge for proactive disease management efforts. While close social interactions can be associated with microbial sharing between individuals, and thereby imply dynamics important for transmission, such associations can be obscured by the influences of factors such as shared diets or environments. Directly-transmitted viral agents, specifically those that are rapidly evolving such as many RNA viruses, can allow for high-resolution inference of transmission, and therefore hold promise for elucidating not only which individuals transmit to each other, but also drivers of those transmission events. Here, we tested a novel approach in the Florida panther, which is affected by several directly-transmitted feline retroviruses. We first inferred the transmission network for an apathogenic, directly-transmitted retrovirus, feline immunodeficiency virus (FIV), and then used exponential random graph models to determine drivers structuring this network. We then evaluated the utility of these drivers in predicting transmission of the analogously transmitted, pathogenic agent, feline leukemia virus (FeLV), and compared FIV-based predictions of outbreak dynamics against empirical FeLV outbreak data. FIV transmission was primarily driven by panther age class and distances between panther home range centroids. FIV-based modeling predicted FeLV dynamics similarly to common modeling approaches, but with evidence that FIV-based predictions captured the spatial structuring of the observed FeLV outbreak. While FIV-based predictions of FeLV transmission performed only marginally better than standard approaches, our results highlight the value of proactively identifying drivers of transmission-even based on analogously-transmitted, apathogenic agents-in order to predict transmission of emerging infectious agents. The identification of underlying drivers of transmission, such as through our workflow here, therefore holds promise for improving predictions of pathogen transmission in novel host populations, and could provide new strategies for proactive pathogen management in human and animal systems., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Gilbertson, Fountain-Jones, Malmberg, Gagne, Lee, Kraberger, Kechejian, Petch, Chiu, Onorato, Cunningham, Crooks, Funk, Carver, VandeWoude, VanderWaal and Craft.)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in 2019 and has resulted in millions of deaths worldwide. Certain populations are at higher risk for infection, especially staff and residents at long-term care facilities (LTCF), due to the congregant living setting and high proportions of residents with many comorbidities. Prior to vaccine availability, these populations represented large fractions of total coronavirus disease 2019 (COVID-19) cases and deaths in the United States. Due to the high-risk setting and outbreak potential, staff and residents were among the first groups to be vaccinated. To define the impact of prior infection on the response to vaccination, we measured antibody responses in a cohort of staff members at an LTCF, many of whom were previously infected by SARS-CoV-2. We found that neutralizing, receptor-binding domain (RBD)-binding, and nucleoprotein (NP)-binding antibody levels were significantly higher after the full vaccination course in individuals that were previously infected and that NP antibody levels could discriminate individuals with prior infection from vaccinated individuals. While an anticipated antibody titer increase was observed after a vaccine booster dose in naive individuals, a boost response was not observed in individuals with previous COVID-19 infection. We observed a strong relationship between neutralizing antibodies and RBD-binding antibodies postvaccination across all groups, whereas no relationship was observed between NP-binding and neutralizing antibodies. One individual with high levels of neutralizing and binding antibodies experienced a breakthrough infection (prior to the introduction of Omicron), demonstrating that the presence of antibodies is not always sufficient for complete protection against infection. These results highlight that a history of COVID-19 exposure significantly increases SARS-CoV-2 antibody responses following vaccination. IMPORTANCE Long-term care facilities (LTCFs) have been disproportionately impacted by COVID-19, due to their communal nature, the high-risk profile of residents, and the vulnerability of residents to respiratory pathogens. In this study, we analyzed the role of prior natural immunity to SARS-CoV-2 in postvaccination antibody responses. The LTCF in our cohort experienced a large outbreak, with almost 40% of staff members becoming infected. We found that individuals that were infected prior to vaccination had higher levels of neutralizing and binding antibodies postvaccination. Importantly, the second vaccine dose significantly boosted antibody levels in those that were immunologically naive prior to vaccination, but not in those that had prior immunity. Regardless of the prevaccination immune status, the levels of binding and neutralizing antibodies were highly correlated. The presence of NP-binding antibodies could be used to identify individuals that were previously infected when prevaccination immune status was not known. Our results reveal that vaccination antibody responses differ depending on prior natural immunity.

Dermatophytes are highly infectious fungi that cause superficial infections in keratinized tissues in humans and animals. This group of fungi is defined by their ability to digest keratin and encompasses a wide range of species. Classification of many of these species has recently changed due to genetic analysis, potentially affecting clinical diagnosis and disease management. In this review, we discuss dermatophyte classification including name changes for medically important species, current and potential diagnostic techniques for detecting dermatophytes, and an in-depth review of Microsporum canis , a prevalent zoonotic dermatophyte. Fungal culture is still considered the "gold standard" for diagnosing dermatophytosis; however, modern molecular assays have overcome the main disadvantages of culture, allowing for tandem use with cultures. Further investigation into novel molecular assays for dermatophytosis is critical, especially for high-density populations where rapid diagnosis is essential for outbreak prevention. A frequently encountered dermatophyte in clinical settings is M. canis , which causes dermatophytosis in humans and cats. M. canis is adapting to its primary host (cats) as one of its mating types (MAT1-2) appears to be going extinct, leading to a loss of sexual reproduction. Investigating M. canis strains around the world can help elucidate the evolutionary trajectory of this fungi.

Microsporum canis is the primary agent causing dermatophytosis in cats, and also infects humans, dogs, and other species. Assessment of genetic variation among M. canis isolates in the United States has not been conducted. Further, M. canis mating type and assessment of disease severity associated with genotypic characteristics have not been rigorously evaluated. We therefore isolated M. canis from 191 domestic cats across the US and characterized genotypes by evaluation of ITS sequence, MAT locus, and microsatellite loci analysis. The genes SSU1 and SUB3, which are associated with keratin adhesion and digestion, were sequenced from a subset of isolates to evaluate potential genetic associations with virulence. Analysis of microsatellite makers revealed three M. canis genetic clusters. Both clinic location and disease severity were significant predictors of microsatellite variants. 100% of the M. canis isolates were MAT1-1 mating gene type, indicating that MAT1-2 is very rare or extinct in the US and that asexual reproduction is the dominant form of replication. No genetic variation at SSU1 and SUB3 was observed. These findings pave the way for novel testing modalities for M. canis and provide insights about transmission and ecology of this ubiquitous and relatively uncharacterized agent.

As the development of combination antiretroviral therapy (cART) against human immunodeficiency virus (HIV) drastically improves the lifespan of individuals with HIV, many are now entering the prime age when Alzheimer's disease (AD)-like symptoms begin to manifest. It has been shown that hyperphosphorylated tau, a known AD pathological characteristic, is prematurely increased in the brains of HIV-infected individuals as early as in their 30s and that its levels increase with age. This suggests that HIV infection might lead to accelerated AD phenotypes. However, whether HIV infection causes AD to develop more quickly in the brain is not yet fully determined. Interestingly, we have previously revealed that the viral glycoproteins HIV gp120 and feline immunodeficiency virus (FIV) gp95 induce neuronal hyperexcitation via cGMP-dependent kinase II (cGKII; also known as PRKG2) activation in cultured hippocampal neurons. Here, we use cultured mouse cortical neurons to demonstrate that the presence of HIV gp120 and FIV gp95 are sufficient to increase cellular tau pathology, including intracellular tau hyperphosphorylation and tau release to the extracellular space. We further reveal that viral glycoprotein-induced cellular tau pathology requires cGKII activation. Taken together, HIV infection likely accelerates AD-related tau pathology via cGKII activation., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2022. Published by The Company of Biologists Ltd.)

Pathogen management strategies in wildlife are typically accompanied by an array of uncertainties such as the efficacy of vaccines or potential unintended consequences of interventions. In the context of such uncertainties, models of disease transmission can provide critical insight for optimizing pathogen management, especially for species of conservation concern. The endangered Florida panther experienced an outbreak of feline leukemia virus (FeLV) in 2002-04, and continues to be affected by this deadly virus. Ongoing management efforts aim to mitigate the effects of FeLV on panthers, but with limited information about which strategies may be most effective and efficient.We used a simulation-based approach to determine optimal FeLV management strategies in panthers. We simulated use of proactive FeLV management strategies (i.e., proactive vaccination) and several reactive strategies, including reactive vaccination and test-and-removal. Vaccination strategies accounted for imperfect vaccine-induced immunity, specifically partial immunity in which all vaccinates achieve partial pathogen protection. We compared the effectiveness of these different strategies in mitigating the number of FeLV mortalities and the duration of outbreaks.Results showed that inadequate proactive vaccination can paradoxically increase the number of disease-induced mortalities in FeLV outbreaks. These effects were most likely due to imperfect vaccine immunity causing vaccinates to serve as a semi-susceptible population, thereby allowing outbreaks to persist in circumstances otherwise conducive to fadeout. Combinations of proactive vaccination with reactive test-and-removal or vaccination, however, had a synergistic effect in reducing impacts of FeLV outbreaks, highlighting the importance of using mixed strategies in pathogen management. Synthesis and applications: Management-informed disease simulations are an important tool for identifying unexpected negative consequences and synergies among pathogen management strategies. In particular, we find that imperfect vaccine-induced immunity necessitates further consideration to avoid unintentionally worsening epidemics in some conditions. However, mixing proactive and reactive interventions can improve pathogen control while mitigating uncertainties associated with imperfect interventions.

Human SERINC5 (SER5) protein is a recently described restriction factor against human immunodeficiency virus-1 (HIV-1), which is antagonized by HIV-1 Nef protein. Other retroviral accessory proteins such as the glycosylated Gag (glycoGag) from the murine leukemia virus (MLV) can also antagonize SER5. In addition, some viruses escape SER5 restriction by expressing a SER5-insensitive envelope (Env) glycoprotein. Here, we studied the activity of human and feline SER5 on HIV-1 and on the two pathogenic retroviruses in cats, feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV). HIV-1 in absence of Nef is restricted by SER5 from domestic cats and protected by its Nef protein. The sensitivity of feline retroviruses FIV and FeLV to human and feline SER5 is considerably different: FIV is sensitive to feline and human SER5 and lacks an obvious mechanism to counteract SER5 activity, while FeLV is relatively resistant to SER5 inhibition. We speculated that similar to MLV, FeLV-A or FeLV-B express glycoGag proteins and investigated their function against human and feline SER5 in wild type and envelope deficient virus variants. We found that the endogenous FeLV recombinant virus, FeLV-B but not wild type exogenous FeLV-A envelope mediates a strong resistance against human and feline SER5. GlycoGag has an additional but moderate role to enhance viral infectivity in the presence of SER5 that seems to be dependent on the FeLV envelope. These findings may explain, why in vivo FeLV-B has a selective advantage and causes higher FeLV levels in infected cats compared to infections of FeLV-A only., Competing Interests: Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Dermatophytosis is a superficial fungal infection of keratinized tissues that can occur in humans and other animals. In domestic cats, the majority of cases are caused by Microsporum canis and can spread to other animals and humans via arthrospores. Between 2019 and 2021, 164 cases of suspected dermatophytosis were recorded in animals from a high-volume shelter in California. Samples (hair, nail, and skin scraping) were collected for routine screening from these individuals. One hundred and twenty-six of these were diagnosed as M. canis by culture and internal transcribed spacer (ITS) sequence. In four suspected dermatophytosis cases occurring in kittens in 2019, cultures grown at 20°C yielded fungi with colony morphology more similar to Arthroderma species than Microsporum. Morphologic and microscopic examinations were conducted, and gene segments for the ITS, β-tubulin, and translation elongation factor 1-alpha (TEF1) regions were sequenced from DNA extracted from these cultures. Sequences were aligned to other dermatophytes using maximum likelihood and neighbor-joining trees and were compared to previously described fungal species to assess nucleotide homology. We identified two previously undescribed fungal species, herein proposed as Arthroderma lilyanum sp. nov. and Arthroderma mcgillisianum sp. nov. M. canis co-cultured in two of the four cases. Other physiologic tests supported this diagnosis. These species have significance as potential pathogens and should be considered as rule-outs for dermatophytosis in cats. The potential for infection of other species, including humans, should be considered., Lay Summary: Two novel fungal species were cultured and characterized from four cases of suspected ringworm in cats at an animal shelter in CA, US. These species were genetically distinct from other dermatophytes and are herein described as Arthroderma lilyanum sp. nov. and Arthroderma mcgillisianum sp. nov., (© The Author(s) 2022. Published by Oxford University Press on behalf of The International Society for Human and Animal Mycology.)

Hunting can fundamentally alter wildlife population dynamics but the consequences of hunting on pathogen transmission and evolution remain poorly understood. Here, we present a study that leverages a unique landscape-scale quasi-experiment coupled with pathogen-transmission tracing, network simulation and phylodynamics to provide insights into how hunting shapes feline immunodeficiency virus (FIV) dynamics in puma (Puma concolor). We show that removing hunting pressure enhances the role of males in transmission, increases the viral population growth rate and increases the role of evolutionary forces on the pathogen compared to when hunting was reinstated. Changes in transmission observed with the removal of hunting could be linked to short-term social changes while the male puma population increased. These findings are supported through comparison with a region with stable hunting management over the same time period. This study shows that routine wildlife management can have impacts on pathogen transmission and evolution not previously considered., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Parasite success typically depends on a close relationship with one or more hosts; therefore, attributes of parasitic infection have the potential to provide indirect details of host natural history and are biologically relevant to animal conservation. Characterization of parasite infections has been useful in delineating host populations and has served as a proxy for assessment of environmental quality. In other cases, the utility of parasites is just being explored, for example, as indicators of host connectivity. Innovative studies of parasite biology can provide information to manage major conservation threats by using parasite assemblage, prevalence, or genetic data to provide insights into the host. Overexploitation, habitat loss and fragmentation, invasive species, and climate change are major threats to animal conservation, and all of these can be informed by parasites., (© 2021 Society for Conservation Biology.)

Genomics encompasses the entire tree of life, both extinct and extant, and the evolutionary processes that shape this diversity. To date, genomic research has focused on humans, a small number of agricultural species, and established laboratory models. Fewer than 18,000 of ∼2,000,000 eukaryotic species (<1%) have a representative genome sequence in GenBank, and only a fraction of these have ancillary information on genome structure, genetic variation, gene expression, epigenetic modifications, and population diversity. This imbalance reflects a perception that human studies are paramount in disease research. Yet understanding how genomes work, and how genetic variation shapes phenotypes, requires a broad view that embraces the vast diversity of life. We have the technology to collect massive and exquisitely detailed datasets about the world, but expertise is siloed into distinct fields. A new approach, integrating comparative genomics with cell and evolutionary biology, ecology, archaeology, anthropology, and conservation biology, is essential for understanding and protecting ourselves and our world. Here, we describe potential for scientific discovery when comparative genomics works in close collaboration with a broad range of fields as well as the technical, scientific, and social constraints that must be addressed., Competing Interests: The authors declare no competing interest., (Copyright © 2022 the Author(s). Published by PNAS.)

Competing Interests: The authors declare no competing interest.

Endogenous retroviruses (ERVs) are increasingly recognized for biological impacts on host cell function and susceptibility to infectious agents, particularly in relation to interactions with exogenous retroviral progenitors (XRVs). ERVs can simultaneously promote and restrict XRV infections using mechanisms that are virus and host specific. The majority of endogenous-exogenous retroviral interactions have been evaluated in experimental mouse or chicken systems, which are limited in their ability to extend findings to naturally infected outbred animals. Feline leukemia virus (FeLV) has a relatively well-characterized endogenous retrovirus with a coexisting virulent exogenous counterpart and is endemic worldwide in domestic cats. We have previously documented an association between endogenous FeLV (enFeLV) long terminal repeat (LTR) copy number and abrogated exogenous FeLV in naturally infected cats and experimental infections in tissue culture. Analyses described here examine limited FeLV replication in experimentally infected peripheral blood mononuclear cells, which correlates with higher enFeLV transcripts in these cells compared to fibroblasts. We further examine NCBI Sequence Read Archive RNA transcripts to evaluate enFeLV transcripts and RNA interference (RNAi) precursors. We find that lymphoid-derived tissues, which are experimentally less permissive to exogenous FeLV infection, transcribe higher levels of enFeLV under basal conditions. Transcription of enFeLV-LTR segments is significantly greater than that of other enFeLV genes. We documented transcription of a 21-nucleotide (nt) microRNA (miRNA) just 3' to the enFeLV 5'-LTR in the feline miRNAome of all data sets evaluated ( n  = 27). Our findings point to important biological functions of enFeLV transcription linked to solo LTRs distributed within the domestic cat genome, with potential impacts on domestic cat exogenous FeLV susceptibility and pathogenesis. IMPORTANCE Endogenous retroviruses (ERVs) are increasingly implicated in host cellular processes and susceptibility to infectious agents, specifically regarding interactions with exogenous retroviral progenitors (XRVs). Exogenous feline leukemia virus (FeLV) and its endogenous counterpart (enFeLV) represent a well-characterized, naturally occurring XRV-ERV dyad. We have previously documented an abrogated FeLV infection in both naturally infected cats and experimental fibroblast infections that harbor higher enFeLV proviral loads. Using an in silico approach, we provide evidence of miRNA transcription that is produced in tissues that are most important for FeLV infection, replication, and transmission. Our findings point to important biological functions of enFeLV transcription linked to solo-LTRs distributed within the feline genome, with potential impacts on domestic cat exogenous FeLV susceptibility and pathogenesis. This body of work provides additional evidence of RNA interference (RNAi) as a mechanism of viral interference and is a demonstration of ERV exaptation by the host to defend against related XRVs.

SARS-CoV-2 spillback from humans into domestic and wild animals has been well documented, and an accumulating number of studies illustrate that human-to-animal transmission is widespread in cats, mink, deer, and other species. Experimental inoculations of cats, mink, and ferrets have perpetuated transmission cycles. We sequenced full genomes of Vero cell-expanded SARS-CoV-2 inoculum and viruses recovered from cats ( n = 6), dogs ( n = 3), hamsters ( n = 3), and a ferret ( n = 1) following experimental exposure. Five nonsynonymous changes relative to the USA-WA1/2020 prototype strain were near fixation in the stock used for inoculation but had reverted to wild-type sequences at these sites in dogs, cats, and hamsters within 1- to 3-d postexposure. A total of 14 emergent variants (six in nonstructural genes, six in spike, and one each in orf8 and nucleocapsid) were detected in viruses recovered from animals. This included substitutions in spike residues H69, N501, and D614, which also vary in human lineages of concern. Even though a live virus was not cultured from dogs, substitutions in replicase genes were detected in amplified sequences. The rapid selection of SARS-CoV-2 variants in vitro and in vivo reveals residues with functional significance during host switching. These observations also illustrate the potential for spillback from animal hosts to accelerate the evolution of new viral lineages, findings of particular concern for dogs and cats living in households with COVID-19 patients. More generally, this glimpse into viral host switching reveals the unrealized rapidity and plasticity of viral evolution in experimental animal model systems., Competing Interests: The authors declare no competing interest.

African Swine Fever (ASF) was reported in domestic pigs in China in 2018. This highly contagious viral infection with no effective vaccine reached pandemic proportions by 2019, substantially impacting protein availability in the same region where the COVID-19 pandemic subsequently emerged. We discuss the genesis, spread, and wide-reaching impacts of this epidemic in a vital livestock species, noting parallels and potential contributions to ignition of COVID-19. We speculate about impacts of these pandemics on global public health infrastructure and suggest intervention strategies using a cost: benefit approach for low-risk, massive-impact events. We note that substantive changes in how the world reacts to potential threats will be required to overcome catastrophes driven by climate change, food insecurity, lack of surveillance infrastructure, and other gaps. A One Health approach creating collaborative processes connecting expertise in human, animal, and environmental health is essential for combating future global health crises., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Tucker, Fagre, Wittemyer, Webb, Abworo and VandeWoude.)

Anellovirus infections are highly prevalent in mammals, however, prior to this study only a handful of anellovirus genomes had been identified in members of the Felidae family. Here we characterise anelloviruses in pumas (Puma concolor), bobcats (Lynx rufus), Canada lynx (Lynx canadensis), caracals (Caracal caracal) and domestic cats (Felis catus). The complete anellovirus genomes (n = 220) recovered from 149 individuals were diverse. ORF1 protein sequence similarity network analysis coupled with phylogenetic analysis, revealed two distinct clusters that are populated by felid-derived anellovirus sequences, a pattern mirroring that observed for the porcine anelloviruses. Of the two-felid dominant anellovirus groups, one includes sequences from bobcats, pumas, domestic cats and an ocelot, and the other includes sequences from caracals, Canada lynx, domestic cats and pumas. Coinfections of diverse anelloviruses appear to be common among the felids. Evidence of recombination, both within and between felid-specific anellovirus groups, supports a long coevolution history between host and virus., (Copyright © 2021 Elsevier Inc. All rights reserved.)

SARS-CoV-2 has had a disproportionate impact on nonhospital health care settings, such as long-term-care facilities (LTCFs). The communal nature of these facilities, paired with the high-risk profile of residents, has resulted in thousands of infections and deaths and a high case fatality rate. To detect presymptomatic infections and identify infected workers, we performed weekly surveillance testing of staff at two LTCFs, which revealed a large outbreak at one of the sites. We collected serum from staff members throughout the study and evaluated it for binding and neutralization to measure seroprevalence, seroconversion, and type and functionality of antibodies. At the site with very few incident infections, we detected that over 40% of the staff had preexisting SARS-CoV-2 neutralizing antibodies, suggesting prior exposure. At the outbreak site, we saw rapid seroconversion following infection. Neutralizing antibody levels were stable for many weeks following infection, suggesting a durable, long-lived response. Receptor-binding domain antibodies and neutralizing antibodies were strongly correlated. The site with high seroprevalence among staff had two unique introductions of SARS-CoV-2 into the facility through seronegative infected staff during the period of study, but these did not result in workplace spread or outbreaks. Together, our results suggest that a high seroprevalence rate among staff can contribute to immunity within a workplace and protect against subsequent infection and spread within a facility. IMPORTANCE Long-term care facilities (LTCFs) have been disproportionately impacted by COVID-19 due to their communal nature and high-risk profile of residents. LTCF staff have the ability to introduce SARS-CoV-2 into the facility, where it can spread, causing outbreaks. We tested staff weekly at two LTCFs and collected blood throughout the study to measure SARS-CoV-2 antibodies. One site had a large outbreak and infected individuals rapidly generated antibodies after infection. At the other site, almost half the staff already had antibodies, suggesting prior infection. The majority of these antibodies bind to the receptor-binding domain of the SARS-CoV-2 spike protein and are potently neutralizing and stable for many months. The non-outbreak site had two unique introductions of SARS-CoV-2 into the facility, but these did not result in workplace spread or outbreaks. Our results reveal that high seroprevalence among staff can contribute to immunity and protect against subsequent infection and spread within a facility.

Feline leukemia virus (FeLV) is associated with a range of clinical signs in felid species. Differences in disease processes are closely related to genetic variation in the envelope ( env ) region of the genome of six defined subgroups. The primary hosts of FeLV are domestic cats of the Felis genus that also harbor endogenous FeLV (enFeLV) elements stably integrated in their genomes. EnFeLV elements display 86% nucleotide identity to exogenous, horizontally transmitted FeLV (FeLV-A). Variation between enFeLV and FeLV-A is primarily in the long terminal repeat (LTR) and env regions, which potentiates generation of the FeLV-B recombinant subgroup during natural infection. The aim of this study was to examine recombination behavior of exogenous FeLV (exFeLV) and enFeLV in a natural FeLV epizootic. We previously described that of 65 individuals in a closed colony, 32 had productive FeLV-A infection, and 22 of these individuals had detectable circulating FeLV-B. We cloned and sequenced the env gene of FeLV-B, FeLV-A, and enFeLV spanning known recombination breakpoints and examined between 1 and 13 clones in 22 animals with FeLV-B to assess sequence diversity and recombination breakpoints. Our analysis revealed that FeLV-A sequences circulating in the population, as well as enFeLV env sequences, are highly conserved. We documented many recombination breakpoints resulting in the production of unique FeLV-B genotypes. More than half of the cats harbored more than one FeLV-B variant, suggesting multiple recombination events between enFeLV and FeLV-A. We concluded that FeLV-B was predominantly generated de novo within each host, although we could not definitively rule out horizontal transmission, as nearly all cats harbored FeLV-B sequences that were genetically highly similar to those identified in other individuals. This work represents a comprehensive analysis of endogenous-exogenous retroviral interactions with important insights into host-virus interactions that underlie disease pathogenesis in a natural setting. IMPORTANCE Feline leukemia virus (FeLV) is a felid retrovirus with a variety of disease outcomes. Exogenous FeLV-A is the virus subgroup almost exclusively transmitted between cats. Recombination between FeLV-A and endogenous FeLV analogues in the cat genome may result in emergence of largely replication-defective but highly virulent subgroups. FeLV-B is formed when the 3' envelope ( env ) region of endogenous FeLV (enFeLV) recombines with that of the exogenous FeLV (exFeLV) during viral reverse transcription and integration. Both domestic cats and wild relatives of the Felis genus harbor enFeLV, which has been shown to limit FeLV-A disease outcome. However, enFeLV also contributes genetic material to the recombinant FeLV-B subgroup. This study evaluates endogenous-exogenous recombination outcomes in a naturally infected closed colony of cats to determine mechanisms and risk of endogenous retroviral recombination during exogenous virus exposure that leads to enhanced virulence. While FeLV-A and enFeLV env regions were highly conserved from cat to cat, nearly all individuals with emergent FeLV-B had unique combinations of genotypes, representative of a wide range of recombination sites within env . The findings provide insight into unique recombination patterns for emergence of new pathogens and can be related to similar viruses across species.