Canine distemper virus: an emerging disease in wild endangered Amur tigers (Panthera tigris altaica)

Canine Distemper Virus Pathogenesis in the Ferret Model

Canine distemper virus (CDV) is a highly contagious pathogen within the morbillivirus genus infecting a wide range of different carnivore species. The virus shares most biological features with other closely related morbilliviruses, including clinical signs, tissue tropism, and replication cycle in the respective host organisms.In the laboratory environment, experimental infections of ferrets with CDV were established as a potent surrogate model for the analysis of several aspects of the biology of the human morbillivirus, measles virus (MeV). The animals are naturally susceptible to CDV and display severe clinical signs resembling the disease seen in patients infected with MeV. As seen with MeV, CDV infects immune cells and is thus associated with a strong transient immunosuppression. Here we describe several methods to evaluate viral load and parameters of immunosuppression in blood-circulating immune cells isolated from CDV-infected animals.

The evolutionary dynamics history of canine distemper virus through analysis of the hemagglutinin gene during 1930-2020

Canine distemper virus (CDV) is a lethal viral disease of carnivores which is considered to be a serious threat to domestic and wild species. Despite the widespread use of vaccines, CDV still occurs in vaccinated animals and current vaccines does not guarantee complete protection. In this study, a total of 286 hemagglutinin (H) gene sequences of the virus isolated in 25 countries during 90 years (1930-2020) were analyzed by Bayesian maximum likelihood analysis to estimate the population dynamics. We identified the most recent common ancestor (TMRCA) of the virus in 1868 in the USA which arrived in continental Europe in 1948, and from there, the virus spread rapidly to other continents. The Canidae family was identified as the original host as well as a source of the subsequent spread. We identified 11 lineages of geographic co-circulating strains globally. The effective population size experienced a two-phase-exponential growth between 2000-2005 and 2010-2012. Our findings provide a novel insight into the epidemic history of canine distemper virus which may facilitate more effective disease management. This study uses a large set of sequencing data on the H gene of CDV to identify distinct lineages of the virus, track its geographic spread over time, analyze its likelihood of transmission within and between animal families, and provide suggestions for improved strategies to combat the virus.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10344-023-01685-z.

Persistent and Severe Viral Replication in PBMCs with Moderate Immunosuppression Served an Alternative Novel Pathogenic Mechanism for Canine Morbillivirus

Measles virus and canine distemper virus (CDV) cause lethal infections in their respective hosts characterized by severe immunosuppression. To furtherly acknowledge the attenuated mechanisms of the regionally ongoing epidemic CDV isolates and provide novel perspectives for designing new vaccines and therapeutic drugs, a recombinant CDV rHBF-vacH was employed with a vaccine hemagglutinin (H) gene replacement by reverse genetics based on an infectious cDNA clone for the CDV wild-type HBF-1 strain. Interestingly, unlike previously published reports that a vaccine H protein completely changed a pathogenic wild-type CDV variant to be avirulent, rHBF-vacH was only partially attenuated by alleviating the degree of viral immunosuppression, and still caused 66.7% lethality in ferrets with a prolonged period of disease. Further comparisons of pathogenic mechanisms proved that the weaker but necessary invasions into peripheral blood mononuclear cells (PBMCs) of rHBF-vacH, and subsequently persistent viral replications in PBMCs and multiple organs, together contributed to its 66.7% mortality. In addition, despite significantly higher titers than the parent viruses, rHBF-vacH would not be a suitable candidate for a live vaccine, with great invasion and infection potentials of PBMCs from 16 tested kinds of host species. Altogether, sustained and severe viral replication in PBMCs with moderate immunosuppression was first proven to be an alternative novel pathogenic mechanism for CDV, which might help us to understand possible reasons for CDV fatal infections among domestic dogs and the highly susceptible wild species during natural transmission. IMPORTANCE Despite widespread vaccine campaigns for domestic dogs, CDV remained an important infectious disease in vaccinated carnivores and wild species. In recent years, the regionally ongoing epidemic CDV isolates have emphasized conservation threats to, and potentially disastrous epidemics in, endangered species worldwide. However, little is known about how to deal with the CDV variants constantly regional epidemic. In this study, we employed a recombinant CDV rHBF-vacH with a vaccine H gene replacement in a CDV wild-type HBF-1 context to attenuate the epidemic CDV variant to design a new vaccine candidate. Interestingly, rHBF-vacH was only partially attenuated by alleviating the degree of viral immunosuppression, and still caused 66.7% lethality in ferrets by weaker but necessary invasions into PBMCs, and subsequently persistent and severe viral replications in PBMCs. Significantly higher virus titers of rHBF-vacH in vitro might indicate the rapid cell-to-cell spreads in vivo that indirectly contribute to fatal infections of rHBF-vacH in ferrets.

Canine Distemper Virus in Tigers (Panthera tigris) and Leopards (P. pardus) in Nepal

From wild dogs (Lycaon pictus) in the Serengeti to tigers (Panthera tigris altaica) in the Russian Far East, canine distemper virus (CDV) has been repeatedly identified as a threat to wild carnivores. Between 2020 and 2022, six Indian leopards (P. pardus fusca) presented to Nepali authorities with fatal neurological disease, consistent with CDV. Here, we report the findings of a serosurvey of wild felids from Nepal. A total of 48 serum samples were tested, comprising 28 Bengal tigers (P. t. tigris) and 20 Indian leopards. Neutralizing antibodies were identified in three tigers and six leopards, equating to seroprevalences of 11% (CI: 2.8-29.3%, n = 28) and 30% (CI: 12.8-54.3%, n = 20), respectively. More than one-third of seropositive animals were symptomatic, and three died within a week of being sampled. The predation of domestic dogs (Canis lupus familiaris) has been posited as a potential route of infection. A comparison of existing diet studies revealed that while leopards in Nepal frequently predate on dogs, tigers do not, potentially supporting this hypothesis. However, further work, including molecular analyses, would be needed to confirm this.

Detection and sequence analysis of Canine morbillivirus in multiple species of the Mustelidae family

BACKGROUND

Canine morbillivirus (canine distemper virus, CDV) is a member of the Paramyxoviridae family. Canine distemper is a serious viral disease that affects many mammalian species, including members of the Mustelidae family. These animals have an elusive nature, which makes related virological studies extremely challenging. There is a significant knowledge gap about the evolution of their viruses and about the possible effects of these viruses to the population dynamics of the host animals. Spleen and lung tissue samples of 170 road-killed mustelids belonging to six species were collected between 1997 and 2022 throughout Hungary and tested for CDV with real-time RT-PCR.

RESULTS

Three species were positive for viral RNA, 2 out of 64 Steppe polecats (Mustela eversmanii), 1 out of 36 European polecats (Mustela putorius) and 2 out of 36 stone martens (Martes foina); all 18 pine martens (Martes martes), 10 least weasels (Mustela nivalis) and 6 stoats (Mustela erminea) tested negative. The complete CDV genome was sequenced in five samples using pan-genotype CDV-specific, amplicon-based Nanopore sequencing. Based on the phylogenetic analysis, all five viral sequences were grouped to the Europe/South America 1 lineage and the distribution of one sequence among trees indicated recombination of the Hemagglutinin gene. We verified the recombination with SimPlot analysis.

CONCLUSIONS

This paper provides the first CDV genome sequences from Steppe polecats and additional complete genomes from European polecats and stone martens. The infected specimens of various species originated from distinct parts of the country over a long time, indicating a wide circulation of CDV among mustelids throughout Hungary. Considering the high virulence of CDV and the presence of the virus in these animals, we highlight the importance of conservation efforts for wild mustelids. In addition, we emphasize the importance of full genomic data acquisition and analysis to better understand the evolution of the virus. Since CDV is prone to recombination, specific genomic segment analyses may provide less representative evolutionary traits than using complete genome sequences.

Contributions of distemper control and habitat expansion to the Amur leopard viability

The Amur leopard (Panthera pardus orientalis) is a critically endangered top predator that struggles on the brink of extinction due to threats such as canine distemper virus (CDV), habitat loss, and inbreeding depression. Here we develop a viability analysis metamodel that combines a traditional individual-based demographic model with an epidemiological model to assess the benefits of alternative population management actions in response to multiple distinct threats. Our results showed an extinction risk of 10.3%-99.9% if no management actions were taken over 100 years under different levels of inbreeding depression. Reducing the risk of CDV infection in Amur leopards through the low-coverage vaccination of leopards and the management of sympatric domestic dogs could effectively improve the survival probability of the leopard population, and with habitat expansion added to these management measures, the population expanded further. Our findings highlight that protecting the Amur leopard necessitates a multifaceted synergistic effort, and controlling multiple threats together may significantly escalate overall viability of a species, especially for small-isolated threatened population. More broadly, our modeling framework could offer critical perspectives and scientific support for conservation planning, as well as specific adaptive management actions for endangered species around the world.

In the absence of management strategies, canine distemper virus threatens the future existence of the endangered Amur leopard.

Molecular diagnosis with the corresponding clinical symptoms of canine distemper virus infection in javan leopard (Panthera pardus ssp. melas)

Diseases are one of the possible threats to the conservation of wild cat populations. One disease that has been reported to infect and cause death, including in various wildlife, is the canine distemper virus (CDV). Here, we report the first case of CDV in an adolescent melanistic Javan female leopard in Indonesia. We combined the clinical report with the Reverse Transcription PCR (RT-PCR) analyses on the faecal and brain samples of partial nucleoprotein (CDV-N) and hemagglutinin (CDV-H) genes. We also performed analyses of urine, haematology, and blood chemistry. The CDV-H nucleotide sequence confirmed the CDV infection in the female leopard and was clustered to the CDV's Asia 1 genotype. This finding opens an investigating window to analyse the pathogen transmission between animals in wildlife, particularly to support the management of conservation in natural habitats in Indonesia.

Canine Distemper Virus in Autochtonous and Imported Dogs, Southern Italy (2014–2021)

Simple Summary

In the period 2014–2021, the circulation of CDV in dogs of Southern Italy was investigated. In this time span a reduction in the circulation of CDV was observed, with a higher frequency of detection of the pathogen in imported dogs (18.4%) compared to stray (7.4%) and household (3.9%) animals. These results underline the effectiveness of the prophylaxis strategy on autochthonous dogs as well as the importance of continuous surveillance of CDV, especially in imported dogs.

Abstract

This study aims to investigate the presence of canine distemper virus (CDV) infection in 949 autochthonous or illegally imported dogs from Southern Italy, over a period of eight years (2014–2021). CDV RNA was detected in 6.8% (65/949) of the animals tested, with no detection of CDV in dogs sampled in 2020–2021. The frequency of CDV detection was higher in imported dogs (19/103, 18.3%) with respect to stray (27/365, 7.4%) and household dogs (19/481, 3.9%). On sequence and phylogenetic analyses of selected strains, the analyzed viruses belonged to the Arctic clade, which has already been reported in Italy and in Europe. The results of our study may suggest a reduction of CDV circulation in Southern Italy, while at the same time highlighting the need for strict controls on dog importation, in order to prevent the introduction of viruses from endemic countries.

Canine morbillivirus (CDV): a review on current status, emergence and the diagnostics

The increasing host range of canine morbillivirus (CDV) affecting important wildlife species such as Lions, Leopard, and Red Pandas has raised the concern. Canine distemper is a pathogen of dogs affecting the respiratory, gastrointestinal, and nervous systems. Seventeen lineages of CDV are reported, and the eighteenth lineage was proposed in 2019 from India. Marked genomic differences in the genome of wild-type virus and vaccine strain are also reported.The variations at the epitope level can be differentiated using specific monoclonal antibodies in neutralization tests. Keeping in mind the current status of the emergence of CDV, genetic and molecular study of circulating strains of the specific geographical region are the essential components of the disease control strategy. New target-based diagnostics and vaccines are in need to counter the effects of the emerging virus population. Control of CDV is necessary to save the endangered, vulnerable, and many other wildlife species to maintain balance in the ecological system. This review provides an overview on emergence reported in CDV, diagnostics developed till today, and a perspective on the disease control strategy, keeping wildlife in consideration.

A Single Oral Immunization with Replication-Competent Adenovirus-Vectored Vaccine Induces a Neutralizing Antibody Response in Mice against Canine Distemper Virus

Canine Distemper Virus (CDV) is a fatal and highly contagious pathogen of multiple carnivores. While injectable vaccines are very effective in protecting domestic animals, their use in the wild is unrealistic. Alternative vaccines are therefore needed. Adenovirus (AdV) vectors are popular vaccine vectors due to their capacity to elicit potent humoral and cellular immune responses against the antigens they carry. In parallel, vaccines based on live human AdV-4 and -7 have been used in U.S. army for several decades as replicative oral vaccines against respiratory infection with the same viruses. Based on these observations, the use of oral administration of replication competent AdV-vectored vaccines has emerged as a promising tool especially for wildlife vaccination. Developing this type of vaccine is not easy, however, given the high host specificity of AdVs and their very low replication in non-target species. To overcome this problem, the feasibility of this approach was tested using mouse adenovirus 1 (MAV-1) in mice as vaccine vectors. First, different vaccine vectors expressing the entire or part H or F proteins of CDV were constructed. These different strains were then used as oral vaccines in BALB/c mice and the immune response to CDV was evaluated. Only the strain expressing the full length CDV H protein generated a detectable and neutralizing immune response to CDV. Secondly, using this strain, we were able to show that although this type of vaccine is sensitive to pre-existing immunity to the vector, a second oral administration of the same vaccine is able to boost the immune response against CDV. Overall, this study demonstrates the feasibility of using replicating AdVs as oral vaccine vectors to immunize against CDV in wildlife carnivores.

Serosurvey of viral pathogens in free-ranging dog populations in the high altitude Trans-Himalayan region

Dogs, as reservoir hosts, have been implicated in the decline of carnivore populations across the globe. We conducted a serosurvey of free-ranging dog populations to assess the population level exposure rates to three viral pathogens, canine parvovirus (CPV), canine distemper virus (CDV) and canine adenovirus (CAV) in a Trans-Himalayan landscape in India that is home to the endangered Snow Leopard. A total of 97 dogs were sampled across six villages as a part of a surgical sterilization campaign during the study period. Samples were tested for IgG antibodies using a table top ELISA kit. Exposure rates to the three viral pathogens in the dog populations was high; 100% for CPV, 54% for CDV and 66% for CAV, with high positive immunoglobulin titer values for CAV and CPV, and low to moderate values for CDV. Overall conservation efforts for native carnivores need to address the role of free-ranging domestic dogs in disease transmission.

Renal Abnormalities Caused by Canine Distemper Virus Infection in Terminal Patients

The aim of this study was to analyze the glomerular and tubular alterations in dogs with terminal distemper through light microscopy, immunofluorescence, and electron microscopy. Thirteen animals with a molecular diagnosis of distemper and neurological signs were selected. As a control group, 10 clinically healthy animals with no manifestations or signs of disease and with negative tests for Ehrlichia sp., Anaplasma sp., and Babesia sp. were included in this study. Renal tissue was evaluated by light microscopy, topochemistry for DNA/chromatin, and video image analysis to detect the nuclear phenotypes of the renal tubular epithelial cells (RTECs), immunofluorescence, and transmission electron microscopy. Results showed that dogs with distemper exhibited anemia, hypergammaglobulinemia, and proteinuria. Creatinine in the distemper group was lower compared to the control group (p = 0.0026), but there was no significant difference in relation to urea (p = 0.9876). Although this alteration may be due to the smaller muscle mass observed in animals with distemper, it probably is not of clinical importance. Glomerular and tubular lesions were confirmed by light microscopy in 84.6% of these animals. Additional findings in the animals with distemper included deposition of different classes of immunoglobulins, particularly IgM in 92.3% of the cases, fibrinogen deposition in 69.2% of the cases as assessed by immunofluorescence, alterations in the nuclear phenotypes of the RTEC characterized by condensation of chromatin, loss of DNA and reduction in the nuclear shape, and the presence of subendothelial and mesangial electron-dense deposits. These findings confirm the existence of renal alterations related to terminal distemper.

Molecular and pathological screening of canine distemper virus in Asiatic lions, tigers, leopards, snow leopards, clouded leopards, leopard cats, jungle cats, civet cats, fishing cat, and jaguar of different states, India

The present investigation was conducted to rule out canine distemper (CD) diseases in Indian wild felids (Asiatic lions, tigers, leopards, snow leopards, clouded leopards, leopard cats, jungle cats, civet cats, fishing cat, and jaguar). The collected samples were screened for CD virus (CDV) by histopathology (HP), immunohistochemistry (IHC) and reverse transcriptase-polymerase chain reaction (RT-PCR) targeting H gene and N gene. The HP and IHC of suspected samples portrayed that 22 [11 leopards, 6 lions, 3 tigers, 1 snow leopard and 1 civet cat] out of 129 (17.05%) wild felids were positive for CD. The major pathological consequences were observed in spleen, lung, kidney and brain. The syncytia and intranuclear as well as intracytoplasmic eosinophilic inclusion bodies were seen in CDV infected cells. Although the histopathological lesions in spleen were more specific and consistent, however, the severe demyelinated leukoencephalitis (usually expected in CD infected dog) was not observed in the brain of any Indian wild felids. Conversely, the CDV antigen has been portrayed via IHC in pancreatic islets of Langerhans of tiger species for the first time in this study. Moreover, the concurrent CD and babesiosis has also been observed in a lioness without a usual coffee-coloured urine. The N gene and H gene of CDV isolates were amplified, sequenced and subsequently constructed the phylogenetic tree. The phylogenetic analysis of H gene revealed that the CDV isolates from Indian lion formed separate clade with CDV isolates from Indian dog and Indian palm civet cat. Furthermore, two CDV isolates from Indian tigers formed clade with Onderstepoort vaccine strain and CDV isolates from dogs of Uttar Pradesh, USA and UK. Evidently, CDV is circulating in Indian wild felids and causing diseases in them.

Interferon-beta, interferon-gamma and their fusion interferon of Siberian tigers (Panthera tigris altaica) in China are involved in positive-feedback regulation of interferon production

As a group of cytokines, interferons are the first line of defense in the antiviral immunity. In this study, Siberian tiger IFN-β (PtIFN-β) and IFN-γ (PtIFN-γ) were successfully amplified, and the two were fused (PtIFN-γ) by overlap extension polymerase chain reaction (SOE-PCR). Bioinformatics analysis disclosed that PtIFN-β and PtIFN-γ have species-specificity and conservation in the course of evolution. After being expressed in prokaryotes, the antiviral activities and physicochemical properties of PtIFN-β, PtIFN-γ and PtIFNβ-γ were analyzed. In Feline kidney cells (F81), PtIFNβ-γ showed more active antiviral activity than PtIFN-β and PtIFN-γ, which has more stable physicochemical properties (acid and alkali resistance, high temperature resistance). In addition, PtIFN-β, PtIFN-γ and PtIFN-γ activated the JAK-STAT pathway and induced the transcription and expression of interferon-stimulated genes (ISGs). Janus kinase (JAK) 1 inhibitor inhibited ISGs expression induced by PtIFN-β, PtIFN-γ and PtIFN-γ. Overall, this research clarified that PtIFN-β, PtIFN-γ and PtIFNβ-γ have the ability to inhibit viral replication and send signals through the JAK-STAT pathway. These findings may facilitate further study on the role of PtIFN in the antiviral immune response, and help to develop approaches for the prophylactic and therapeutic of viral diseases based on fusion interferon.

A new canine distemper virus lineage identified from red pandas in China

Canine distemper virus (CDV) is a highly contagious virus that causes multi-systemic, sub-clinical to fatal diseases in a wide range of carnivore species. Based on the sequences of the haemagglutinin (H) gene, CDV strains have been classified into 18 major genetic lineages. In this study, we characterized the genomes of CDV isolated from the lungs of two dead red pandas in China. Histopathological and immunohistochemical analyses revealed damage due to viral infection in these lungs. The two strains showed a deep genetic distance from the other 18 recognized lineages (>4.6% at nucleotide level and >5.0% at amino acid level). The maximum clade credibility tree of the H- gene sequences showed that they belonged to an independent clade and had diverged a relatively long time ago from the Asia-4 lineage (since 1884). These results suggest that the analyzed strains belong to a new CDV lineage, which we designate as Asia-6. Our finding indicates that CDV infections in wildlife in China are complex and are a threat to endangered carnivores.

A RETROSPECTIVE STUDY OF BRAIN LESIONS IN CAPTIVE NONDOMESTIC FELIDS

This retrospective study identified and characterized brain lesions in captive nondomestic felids from a large cat sanctuary. Necropsy reports from January 2002 through December 2018 were examined, and gross images and microscopic slides were reviewed from individual cats, where available. In total, 255 cats met the following inclusion criteria: complete necropsy report available, brain examined grossly or microscopically, and age of >1 mon. Of the 255 cats, 49 cats (19%) were determined to have brain lesions. Eleven different felid species, as well as one captive-bred hybrid (liger), were included in the study, with tigers (Panthera tigris) (55%) and lions (Panthera leo) (18%) being the most common species. Lesions were grouped into six etiologic categories: neoplastic (32%), vascular (26%), inflammatory or infectious (20%), congenital (9%), idiopathic (7%), and metabolic (6%). Not included in these categorized lesions were previously undescribed amphophilic globules in the cerebral cortex of many cats with and without other brain lesions; these were in 95% of lion and 93% of tiger brains where the cerebral cortex was available for histologic examination. These globules were not associated with clinical disease. The histopathologic and gross brain changes documented in this study provide insight into specific diseases and pathologic processes that affect the brains of captive large cat populations.

A meta-analysis of cross-sectional studies on the frequency and risk factors associated with canine morbillivirus infection in China

BACKGROUND

The canine morbillivirus, previously known as canine distemper virus (CDV), is a pathogen which infects dogs worldwide and causes fatal disease. CDV has a broad range of hosts and can infect at least six orders and more than 20 mammalian families. Domestic dogs are the main hosts of CDV and play a central role in the transmission of the virus. However, the prevalence of CDV infection in China remains unknown since there are only a few studies which systematically analysed the prevalence of CDV in domestic dogs in the country. Therefore, we conducted a systematic review and meta-analysis of the frequency of CDV positivity and associated risk factors of CDV in Chinese domestic dogs.

METHODS

We systematically searched for studies on the frequency of CDV in Chinese domestic dogs published in English and Chinese to conduct a meta-analysis using the random-effects model with a forest plot with a 95% confidence interval.

RESULTS

The overall estimated frequency of CDV positivity in Chinese domestic dogs was 22%. In addition, our data show that sampling season, age, breed, and immunisation status are associated with CDV infection frequency.

CONCLUSION

In a word, CDV is circulating in domestic dogs in China. Continued intervention strategies based on risk factors are necessary to reduce the frequency of CDV infection, especially in endemic regions.

TEMPORAL AND SPATIAL PATTERNS IN CANINE DISTEMPER VIRUS CASES IN WILDLIFE DIAGNOSED AT THE SOUTHEASTERN COOPERATIVE WILDLIFE DISEASE STUDY, 1975-2019

Canine distemper is a high-impact disease of many mammal species and has caused substantial carnivore population declines. Analysis was conducted on passive surveillance data of canine distemper (CDV)-positive wild mammal cases submitted to the Southeastern Cooperative Wildlife Disease Study, Athens, Georgia, US, between January 1975 and December 2019. Overall, 964 cases from 17 states were CDV positive, including 646 raccoons (Procyon lotor), 254 gray foxes (Urocyon cinereoargenteus), 33 striped skunks (Mephitis mephitis), 18 coyotes (Canis latrans), four red foxes (Vulpes vulpes), three gray wolves (Canis lupus), three American black bears (Ursus americanus), two American mink (Mustela vison), and one long-tailed weasel (Mustela frenata). Raccoon and gray fox case data from the state of Georgia (n=441) were selected for further analysis. Autoregressive integrated moving average models were developed predicting raccoon and gray fox case numbers. The best-performing model for gray foxes used numbers of gray fox CDV cases from the previous 2 mo and of raccoon cases in the present month to predict the numbers of gray fox cases in the present month. The best-performing model for raccoon prediction used numbers of raccoon CDV cases from the previous month and of gray fox cases in the present month and previous 2 mo to predict numbers of raccoon cases in the present month. Temporal trends existed in CDV cases for both species, with cases more likely to occur during the breeding season. Spatial clustering of cases was more likely to occur in areas of medium to high human population density; fewer cases occurred in both the most densely populated and sparsely populated areas. This pattern was most prominent for raccoons, which may correspond to high transmission rates in suburban areas, where raccoon population densities are probably highest, possibly because of a combination of suitable habitat and supplemental resources.

Exposure of Wild Sumatran Tiger (Panthera tigris sumatrae) to Canine Distemper Virus

Canine distemper virus (CDV) is recognized as a conservation threat to Amur tigers (Panthera tigris altaica) in Russia, but the risk to other subspecies remains unknown. We detected CDV neutralizing antibodies in nine of 21 wild-caught Sumatran tigers (42.9%), including one sampled on the day of capture, confirming exposure in the wild.

Prevalence and type of ocular disease in a population of aged captive nondomestic felids

OBJECTIVES

Report of prevalence and type of ocular disease in a captive population of nondomestic felids.

METHODS

Medical records of 202 cats from 1993 to 2018 were reviewed. Species, age at diagnosis, sex, ocular examination abnormalities, systemic/physical examination abnormalities, type of examination (visual, sedated, or anesthetized), ocular structures affected, other diagnostics, therapy, and resolution of ocular disease were recorded.

RESULTS

A total of 202 nondomestic felids including 18 different species (bobcat, caracal, cougar, Fishing cat, Geoffroy's cat, jaguar, jungle cat, leopard, leopard cat, liger, lion, lynx, ocelot, Sand cat, Savannah cat, serval, snow leopard, and tiger) from a rescue facility were evaluated. Forty-six ocular lesions were diagnosed in 33 (16.3%) cats from 8 different species (bobcat, caracal, cougar, leopard, lion, ocelot, serval, and tiger) with a mean age of 16 ± 5.9 years at time of diagnosis. Ocular lesions included corneal disease (37%) (ulcerations, perforations, keratitis, corneal scars), cataracts (23.9%), hyphema (8.7%), lens luxation (6.5%), retinal detachment (6.5%), uveitis (4.3%), conjunctival disease (4.3%), retinal degeneration (2.1%), glaucoma (2.1%), and optic neuritis (2.1%). Therapies included medical (topical antibiotics, anti-inflammatories, serum, etc.) and/or surgical management (enucleation, intracapsular lens extraction, corneoconjunctival transposition, and corneal burr debridement).

CONCLUSIONS

To the authors' knowledge, this is the first report of the prevalence of ocular disease in a population of captive nondomestic felids. It is difficult to diagnose and treat ocular disease in nondomestic cats due to challenges related to handling, diagnostics, and therapeutics in nondomestic species. Ocular disease seen in this population is similar to that found in domestic cat populations.

Sylvatic Canine Morbillivirus in Captive Panthera Highlights Viral Promiscuity and the Need for Better Prevention Strategies

Canine Distemper Virus (CDV) is a multi-host morbillivirus that infects virtually all Carnivora and a few non-human primates. Here we describe a CDV outbreak in an exotic felid rescue center that led to the death of eight felids in the genus Panthera. Similar to domestic dogs and in contrast to previously described CDV cases in Panthera, severe pneumonia was the primary lesion and no viral antigens or CDV-like lesions were detected in the central nervous system. Four tigers succumbed to opportunistic infections. Viral hemagglutinin (H)-gene sequence was up to 99% similar to strains circulating contemporaneously in regional wildlife. CDV lesions in raccoons and skunk were primarily encephalitis. A few affected felids had at least one previous vaccination for CDV, while most felids at the center were vaccinated during the outbreak. Panthera sharing a fence or enclosure with infected conspecifics had significantly higher chances of getting sick or dying, suggesting tiger-tiger spread was more likely than recurrent spillover. Prior vaccination was incomplete and likely not protective. This outbreak highlights the need for further understanding of CDV epidemiology for species conservation and public health.

Cerebral cysticercosis in a wild Bengal tiger (Panthera tigris tigris) in Bhutan: A first report in non-domestic felids

The endangered Bengal tiger (Panthera tigris tigris) is a keystone species playing an essential role in ecology as well as in the social and spiritual lives of the Himalayan people. The latest estimate of the Bengal tiger population in Bhutan accounts for 103 individuals. Infectious organisms, including zoonotic parasites causing high burden in human health, have received little attention as a cause of mortality in tigers. Taeniosis/cysticercosis, caused by the cestode Taenia solium, is considered one of the major neglected tropical diseases in Southeast Asia. We present here a case of neurocysticercosis in a Bengal tiger showing advanced neurological disease outside Thimphu, the capital city of Bhutan. After palliative care, the animal died, and necropsy revealed multiple small cysts in the brain. Here we show the presence of two genetic variants of T. solium in the parasite material collected based on PCR and sequencing of the complete cox1 and cytB genes. The sequences form a discrete branch within the Asia plus Madagascar cluster of the parasite. On other hand, tests for feline morbillivirus, feline calicivirus, canine distemper virus, Nipah, rabies, Japanese encephalitis, feline leukaemia and feline immunodeficiency virus were negative. In contrast, PCR for feline herpesvirus was positive and a latex agglutination test revealed an elevated antibody titer against Toxoplasma gondii (titer 1:256). The molecular examination of taeniid eggs isolated from the tiger faeces produced sequences for which the highest homology in GenBank is between 92% and 94% with T. regis and T. hydatigena. This fatal case of T. solium neurocysticercosis, a disease previously unrecorded in tigers or other non-domestic felids, demonstrates an anthropogenically driven transmission of a deadly pathogen which could become a serious threat to the tiger population.

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This is the first report of a fatal infection with Taenia solium in a Bengal tiger.

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There is a need for research into infectious disease threats to tigers in Bhutan.

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The importance of a ‘One Health’ approach is demonstrated and recommended.

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Non-domestic felids.

Distemper, extinction, and vaccination of the Amur tiger

Canine distemper virus (CDV) has recently emerged as an extinction threat for the endangered Amur tiger (Panthera tigris altaica). CDV is vaccine-preventable, and control strategies could require vaccination of domestic dogs and/or wildlife populations. However, vaccination of endangered wildlife remains controversial, which has led to a focus on interventions in domestic dogs, often assumed to be the source of infection. Effective decision making requires an understanding of the true reservoir dynamics, which poses substantial challenges in remote areas with diverse host communities. We carried out serological, demographic, and phylogenetic studies of dog and wildlife populations in the Russian Far East to show that a number of wildlife species are more important than dogs, both in maintaining CDV and as sources of infection for tigers. Critically, therefore, because CDV circulates among multiple wildlife sources, dog vaccination alone would not be effective at protecting tigers. We show, however, that low-coverage vaccination of tigers themselves is feasible and would produce substantive reductions in extinction risks. Vaccination of endangered wildlife provides a valuable component of conservation strategies for endangered species.

Identification of Novel Feline Paramyxoviruses in Guignas (Leopardus guigna) from Chile

The family of paramyxoviruses has received growing attention as several new species have been identified recently, notably two different clusters in domestic cats, designated as feline morbillivirus (FeMV) and feline paramyxovirus (FPaV). Their phylogenetic origin and whether wild felids also harbor these viruses are currently unknown. Kidney samples from 35 guignas (Leopardus guigna), a wild felid from Chile, were investigated for paramyxoviruses using consensus-RT-PCR. In addition, thirteen serum samples of guignas were screened for the presence of FeMV-specific antibodies by an immunofluorescence assay (IFA). Viral RNA was detected in 31% of the kidney samples. Phylogenetic analyses revealed two well-supported clusters, related to isolates from domestic cats, rodents and bats. No significant histopathology changes were recorded in infected guignas. Serology identified two samples which were positive for FeMV-specific antibodies. Our study highlights the diversity of paramyxovirus infections in felids with special emphasis on guignas from Chile.

Identifying Candidate Genetic Markers of CDV Cross-Species Pathogenicity in African Lions

Canine distemper virus (CDV) is a multi-host pathogen with variable clinical outcomes of infection across and within species. We used whole-genome sequencing (WGS) to search for viral markers correlated with clinical distemper in African lions. To identify candidate markers, we first documented single-nucleotide polymorphisms (SNPs) differentiating CDV strains associated with different clinical outcomes in lions in East Africa. We then conducted evolutionary analyses on WGS from all global CDV lineages to identify loci subject to selection. SNPs that both differentiated East African strains and were under selection were mapped to a phylogenetic tree representing global CDV diversity to assess if candidate markers correlated with documented outbreaks of clinical distemper in lions (n = 3). Of 54 SNPs differentiating East African strains, ten were under positive or episodic diversifying selection and 20 occurred in the clinical strain despite strong purifying selection at those loci. Candidate markers were in functional domains of the RNP complex (n = 19), the matrix protein (n = 4), on CDV glycoproteins (n = 5), and on the V protein (n = 1). We found mutations at two loci in common between sequences from three CDV outbreaks of clinical distemper in African lions; one in the signaling lymphocytic activation molecule receptor (SLAM)-binding region of the hemagglutinin protein and another in the catalytic center of phosphodiester bond formation on the large polymerase protein. These results suggest convergent evolution at these sites may have a functional role in clinical distemper outbreaks in African lions and uncover potential novel barriers to pathogenicity in this species.

Dependence of the leopard Panthera pardus fusca in Jaipur, India, on domestic animals

The ecology and predator–prey dynamics of large felids in the tropics have largely been studied in natural systems where wild ungulates constitute the majority of the prey base. However, in tropical countries where communities are primarily agrarian, the high density of domestic animals in human-dominated landscapes can be a potential prey source for large carnivores. We demonstrate almost complete dependence of the Vulnerable leopard Panthera pardus fusca in the Jhalana Reserve Forest in Jaipur, north-west India on domestic animals as prey. We analysed 132 leopard scats collected during the dry season of November 2017–April 2018. Domestic animals comprised the majority of the leopards' prey (89.5% frequency of occurrence): dogs Canis lupus familiaris (44%), cats Felis catus (13%), goats Capra aegagrus hircus (16%) and cattle Bos taurus (15%). Wild species, which occurred in the leopards' diet at a relatively low frequency, were rodents, the hare Lepus nigricollis, small Indian civet Viverricula indica, rhesus macaque Macaca mulatta, northern plains grey langur Semnopithecus entellus and mongoose Herpestes edwardsii. Diet is also a function of availability of potential prey, but no data are available on the density of the leopard's wild prey species in Jhalana Reserve Forest. Nevertheless, our results suggest that abundance of domestic prey around Jhalana Reserve Forest sustains the c. 25 known leopards. We conclude that these leopards, by preying on feral dogs in an urban environment, could be considered as suppliers of a service to the human population amongst whom they thrive, although this potentially exposes the leopards to the canine distemper virus.

Feline Morbillivirus Infection Associated With Tubulointerstitial Nephritis in Black Leopards (Panthera pardus)

Feline morbillivirus (FeMV) is an emerging RNA virus in the Paramyxoviridae family that was recently discovered in domestic cats ( Felis catus). To date, 2 genotypes (FeMV-1 and FeMV-2) have been detected in cats from various countries, and FeMV-1 is recognized as a pathogen associated with nephritis. However, information regarding the pathological roles and potential transmission to other felids is limited. In this article, we describe the identification of FeMV in 2 black leopards ( Panthera pardus) in Thailand that showed severe azotemia and tubulointerstitial nephritis. Molecular analysis of the partial coding sequence of the L gene revealed that these leopard FeMV strains were genetically close to the FeMV-1 isolate from domestic Thai cats. Immunohistochemistry and immunofluorescence analyses using polyclonal IgG antibodies against the FeMV matrix (M) protein showed FeMV-M antigen in renal tubular epithelial cells. These analyses also showed infiltrating lymphocytes in the renal parenchymal lesions and in the cytoplasm of lymphoid cells residing in the spleen, suggesting viral tropism and a possible pathological role. These findings are the first evidence that indicates that the black leopard could be a possible host for FeMV infection. As for other cats, the role of FeMV as a potential cause of renal disease remains to be established. The pathogenesis of FeMV infection in black leopards, or in other wild felids, through a viral transmission mechanism warrants further investigation.

Genetic signature of disease epizootic and reintroduction history in an endangered carnivore

Emerging infectious diseases have recently increased in wildlife and can result in population declines and the loss of genetic diversity in susceptible populations. As populations of impacted species decline, genetic diversity can be lost, with ramifications including reduced effective population size and increased population structuring. For species of conservation concern, which may already have low genetic diversity, the loss of genetic diversity can be especially important. To investigate the impacts of a novel pathogen on genetic diversity in a genetically depauperate endangered species, we assessed the ramifications of a sylvatic plague-induced bottleneck in black-footed ferrets (Mustela nigripes). Following a plague epizootic, we genotyped 184 ferrets from Conata Basin and Badlands National Park, South Dakota, at seven microsatellite loci. We compared our results to pre-plague studies in the same population. We observed population substructuring into three genetic clusters. These clusters reflect founder effects from ferret reintroduction events followed by genetic drift. Compared to the pre-plague population, we observed losses of allelic diversity in all clusters, as well as significantly reduced heterozygosity in one cluster. These results indicate that disease epizootics may reduce population size and also genetic diversity. Our results suggest the importance of early and sustained management in mitigating disease epizootics in naïve populations for the maintenance of genetic diversity.

Characterization and Comparison of SLAM/CD150 in Free-Ranging Coyotes, Raccoons, and Skunks in Illinois for Elucidation of Canine Distemper Virus Disease

Canine distemper virus (CDV) is a cause of significant disease in canids and increasingly recognized as a multi-host pathogen, particularly of non-canid families within Carnivora. CDV outbreaks in sympatric mesocarnivores are routinely diagnosed in the Forest Preserve District of Cook County, Illinois. CDV is diagnosed more commonly and the disease more severe in raccoons and striped skunks than in coyotes. Research in other species suggests host cell receptors may play a role in variable disease outcome, particularly, the signaling lymphocyte activation molecule (SLAM) located on lymphoid cells. To evaluate receptor differences, partial SLAM genes were sequenced, and predicted amino acid (AA) sequences and structural models of the proposed viral interface assessed. Of 263 aligned nucleotide base pairs, 36 differed between species with 24/36 differences between canid and non-canids. Raccoon and skunk predicted AA sequences had higher homology than coyote and raccoon/skunk sequences and 8/11 residue differences were between coyote and raccoons/skunks. Though protein structure was similar, few residue differences were associated with charge and electrostatic potential surface alterations between canids and non-canids. RNAScope^®(Advanced Cell Diagnostics, Silicon Valley, USA) ISH revealed low levels of expression that did not differ significantly between species or tissue type. Results suggest that differences in host receptors may impact species-specific disease manifestation.

Cross-species transmission and evolutionary dynamics of canine distemper virus during a spillover in African lions of Serengeti National Park

The outcome of pathogen spillover from a reservoir to a novel host population can range from a "dead-end" when there is no onward transmission in the recipient population, to epidemic spread and even establishment in new hosts. Understanding the evolutionary epidemiology of spillover events leading to discrete outcomes in novel hosts is key to predicting risk and can lead to a better understanding of the mechanisms of emergence. Here we use a Bayesian phylodynamic approach to examine cross-species transmission and evolutionary dynamics during a canine distemper virus (CDV) spillover event causing clinical disease and population decline in an African lion population (Panthera leo) in the Serengeti Ecological Region between 1993 and 1994. Using 21 near-complete viral genomes from four species we found that this large-scale outbreak was likely  ignited by a single cross-species spillover event from a canid reservoir to noncanid hosts <1 year before disease detection and explosive spread of CDV in lions. Cross-species transmission from other noncanid species probably fuelled the high prevalence of CDV across spatially structured lion prides. Multiple lines of evidence suggest that spotted hyenas (Crocuta crocuta) could have acted as the proximate source of CDV exposure in lions. We report 13 nucleotide substitutions segregating CDV strains found in canids and noncanids. Our results are consistent with the hypothesis that virus evolution played a role in CDV emergence in noncanid hosts following spillover during the outbreak, suggest that host barriers to clinical infection can limit outcomes of CDV spillover in novel host species.

Impact of host intraspecies genetic variation, diet, and age on bacterial and fungal intestinal microbiota in tigers

The bacterial microbiota in the gut varies among species, as well as with habitat, diet, age, and other factors. Intestinal microbiota homeostasis allows a host to adjust metabolic and immune performances in response to environmental changes. Therefore, potential implications of the gut microbiota in sustaining the health of the host have gained increasing attention in the field of endangered animal conservation. However, the effect of host intraspecies genetic variation on the gut microbiota is unknown. Moreover, little is known about the complexity of the gut mycobiota. Tigers are listed as endangered species, raising worldwide concern. Potential influences of subspecies, diet, and age on the gut microbiota in tigers were investigated in this study to provide a better understanding of the response of the tiger gut microbiota to external changes. The results revealed that the impacts of the factors listed above on gut bacterial and fungal communities are versatile. Host intraspecies genetic variation significantly impacted only fungal alpha diversity of the gut microbiota. Differences in diet, on the other hand, had a significant impact on alpha diversity of the gut microbiota, but exerted different effects on beta diversity of gut bacterial and fungal communities. Host age had no significant impact on the diversity of the gut fungal communities, but significantly impacted beta diversity of gut bacterial communities. This comprehensive study of tiger gut microbiota is an essential reference for tiger conservation when considering feeding and management strategies, and will contribute to a better understanding of the mycobiota in wildlife.

Development and validation of a portable, point-of-care canine distemper virus qPCR test

Canine distemper virus (CDV) is a multi-host pathogen that can cause significant mortality in domestic, wild terrestrial and marine mammals. It is a major conservation threat in some endangered species. Infection can result in severe respiratory disease and fatal encephalitis. Diagnosis and disease monitoring in wildlife, and differentiation of CDV from rabies (a life-threatening zoonotic disease that can produce similar neurologic signs), would benefit from the availability of a portable, point-of-care (POC) diagnostic test. We therefore developed a quantitative RT-PCR assay for CDV using shelf-stable, lyophilized reagents and target-specific primers and probes for use with the handheld Biomeme two3™ qPCR thermocycler. Biomeme's extraction methodology, lyophilized reagents, and thermocycler were compared to our standard laboratory-based methods to assess sensitivity, efficiency and overall test performance. Results using a positive control plasmid for CDV showed comparable sensitivity (detection of 50 copies) and PCR efficiency between the two platforms, and CDV detection was similar between platforms when tested using a modified live CDV vaccine. Significantly higher Ct values (average Ct = 5.1 cycles) were observed using the Biomeme platform on known CDV positive animal samples. CDV detection using the Biomeme platform was similar in 25 of 26 samples from suspect CDV cases when compared to standard virology laboratory testing. One false positive was observed that was negative upon retest. The Biomeme methodology can be adapted for detection of specific targets, and this portable technology saves time by eliminating the need for local or international sample transport for laboratory-based diagnostics. However, results of our testing suggest that decreased diagnostic sensitivity (higher Ct values) relative to laboratory-based methods was observed using animal samples, so careful validation and optimization are essential. Portable qPCR platforms can empower biologists and wildlife health professionals in remote and low-resource settings, which will greatly improve our understanding of CDV disease ecology and associated conservation threats in wildlife.

REVIEW OF CANINE DISTEMPER VACCINATION USE AND SAFETY IN NORTH AMERICAN CAPTIVE LARGE FELIDS (PANTHERA SPP.) FROM 2000 TO 2017

Data on canine distemper virus (CDV) vaccination were collected on 812 large felids (351 tigers, Panthera tigris; 220 lions, Panthera leo; 143 snow leopards, Panthera uncia; 50 leopards, Panthera pardus; and 48 jaguars, Panthera onca) from 48 institutions to assess vaccine use and safety. The documented individual vaccination events with multiple products numbered 2,846. Canarypox-vectored CDV vaccines were the most commonly used vaccines (96.3% of all vaccinations) and the Purevax^® Ferret Distemper (PFD) vaccine was the most commonly used canarypox-vectored vaccine (91.0% of all vaccinations). Modified live virus (MLV) CDV vaccines were used for 3.7% of all vaccinations, and only in tigers, lions, and snow leopards. Adverse effects were reported after 0.5% (13 of 2,740) of the canarypox-vectored vaccinations and after 2.9% (3 of 104) of the MLV CDV vaccinations. This low complication rate suggests large felids may not be as sensitive to adverse effects of MLV CDV vaccines as other exotic carnivores. Serological data were available from 159 individuals (69 tigers, 31 lions, 31 snow leopards, 22 jaguars, and 6 Amur leopards, Panthera pardus orientalis) vaccinated with the PFD vaccine, and 66.0% of vaccinates seroconverted (defined as acquiring a titer ≥1: 24) at some point postvaccination: 24.3% after one vaccination, 55.8% after two vaccinations, 54.3% after three vaccinations, and 79.2% after four or more vaccinations. Among animals exhibiting seroconversion after the initial PFD vaccinations, 88.9% still had titers ≥12 mo and ≥24 mo after the last vaccination, and 87.5% had titers ≥1: 24 at ≥36 mo after the last vaccination. The study was unable to assess fully the safety of vaccination with either canarypox-vectored or MLV CDV vaccines during gestation because of the small number of animals vaccinated while pregnant (n = 6, all vaccinated with PFD).

Immunohistochemical identification of antigens of canine distemper virus in neotropical felids from Southern Brazil

The pathologic and immunohistochemical findings associated with infections due to canine distemper virus (CDV) are described in the cougar (Puma concolor), margay (Leopardus wiedii) and jaguarundi (Herpailurus yagouaroundi) from Southern Brazil. Tissue sections of the neotropical felids (n = 3) that died at the Bela Vista Sanctuary, Paraná, Southern Brazil were routinely processed for histopathology to identify possible histopathologic patterns associated with infections due to CDV. Selected formalin-fixed paraffin embedded tissue sections of the lungs and urinary bladder were used in immunohistochemical assays designed to identify the antigens of CDV. The main histopathologic patterns identified were interstitial pneumonia in the margay and jaguarundi, while ballooning degeneration of the transitional epithelium of the urinary bladder was observed in the cougar. Positive immunoreactivity to antigens of CDV was identified within intralesional sections of the lungs of the two wild felids with interstitial pneumonia and in the degenerated urothelium of the cougar. These findings indicate that these neotropical cats were infected by a viral infectious disease pathogen common to the domestic dog and add to the few documented descriptions of CDV-induced infections in wildlife from Brazil.

Antiviral efficacy of favipiravir against canine distemper virus infection in vitro

Background

Canine distemper (CD) is an acute infectious disease with high morbidity rates caused by a highly contagious pathogen (Canine Morbillivirus, also known as canine distemper virus, CDV). CDV can infect a broad range of carnivores resulting in complex clinical signs. Currently, there is no effective method to treat for CDV infections. Favipiravir (T-705), a pyrazine derivative, was shown to be an effective antiviral drug against RNA viruses, acting on RNA-dependent RNA polymerase (RdRp). However, whether the T-705 has antiviral effects following CDV infection is unclear. Here, we investigated the antiviral effect of T-705 against CDV-3 and CDV-11 strains in Vero and DH82 cell lines.

Results

Our data demonstrated that T-705 significantly inhibited the replication of CDV-3 and CDV-11 in both Vero and DH82 cells at different concentrations, ranging from 2.441 μg/ml to 1250 μg/ml. Additionally, T-705 exhibited efficacious antiviral effects when administered at different time points after virus infection. Cytotoxicity tests showed a slight decline in viability in Vero cells after T-705 treatment, and no apparent cytotoxicity was detected in T-705 treated DH82 cells. Comparison of anti-CDV polyclonal serum only inhibition of CDV in supernatant, T-705 directly inhibited viral replication in cells, and indirectly reduced the amount of virions in supernatant. The combination application of T-705 and anti-CDV polyclonal serum exhibited a rapid and robust inhibition against virions in supernatant and virus replication in cells.

Conclusions

Our data strongly indicated that T-705 effectively inhibited viral replication following CDV infection in vitro, and could be a potential candidate for treatment for CD.

Evolution and Interspecies Transmission of Canine Distemper Virus-An Outlook of the Diverse Evolutionary Landscapes of a Multi-Host Virus

Canine distemper virus (CDV) is a worldwide distributed virus which belongs to the genus Morbillivirus within the Paramyxoviridae family. CDV spreads through the lymphatic, epithelial, and nervous systems of domestic dogs and wildlife, in at least six orders and over 20 families of mammals. Due to the high morbidity and mortality rates and broad host range, understanding the epidemiology of CDV is not only important for its control in domestic animals, but also for the development of reliable wildlife conservation strategies. The present review aims to give an outlook of the multiple evolutionary landscapes and factors involved in the transmission of CDV by including epidemiological data from multiple species in urban, wild and peri-urban settings, not only in domestic animal populations but at the wildlife interface. It is clear that different epidemiological scenarios can lead to the presence of CDV in wildlife even in the absence of infection in domestic populations, highlighting the role of CDV in different domestic or wild species without clinical signs of disease mainly acting as reservoirs (peridomestic and mesocarnivores) that are often found in peridomestic habits triggering CDV epidemics. Another scenario is driven by mutations, which generate genetic variation on which random drift and natural selection can act, shaping the genetic structure of CDV populations leading to some fitness compensations between hosts and driving the evolution of specialist and generalist traits in CDV populations. In this scenario, the highly variable protein hemagglutinin (H) determines the cellular and host tropism by binding to signaling lymphocytic activation molecule (SLAM) and nectin-4 receptors of the host; however, the multiple evolutionary events that may have facilitated CDV adaptation to different hosts must be evaluated by complete genome sequencing. This review is focused on the study of CDV interspecies transmission by examining molecular and epidemiological reports based on sequences of the hemagglutinin gene and the growing body of studies of the complete genome; emphasizing the importance of long-term multidisciplinary research that tracks CDV in the presence or absence of clinical signs in wild species, and helping to implement strategies to mitigate the infection. Integrated research incorporating the experience of wildlife managers, behavioral and conservation biologists, veterinarians, virologists, and immunologists (among other scientific areas) and the inclusion of several wild and domestic species is essential for understanding the intricate epidemiological dynamics of CDV in its multiple host infections.

Comparative sequence analysis of morbillivirus receptors and its implication in host range expansion

SLAM (CD150) and nectin-4 are the major morbillivirus receptors responsible for virus pathogenesis and host range expansion. Recently, morbillivirus infections have been reported in unnatural hosts, including endangered species, posing a threat to their conservation. To understand the host range expansion of morbilliviruses, we generated the full-length sequences of morbillivirus receptors (goat, sheep, and dog SLAM, and goat nectin-4) and tried to correlate their role in determining host tropism. A high level of amino acid identity was observed between the sequences of related species, and phylogenetic reconstruction showed that the receptor sequences of carnivores, marine mammals, and small ruminants grouped separately. Analysis of the ligand binding region (V region; amino acid residues 52-136) of SLAM revealed high amino acid identity between small ruminants and bovine SLAMs. Comparison of canine SLAM with ruminants and non-canids SLAM revealed appreciable changes, including charge alterations. Significant differences between feline SLAM and canine SLAM have been reported. The binding motifs of nectin-4 genes (FPAG motif and amino acid residues 60, 62, and 63) were found to be conserved in sheep, goat, and dog. The differences reported in the binding region may be responsible for the level of susceptibility or resistance of a species to a particular morbillivirus.

Psittacid Adenovirus-2 infection in the critically endangered orange-bellied parrot (Neophema chrysogastor): A key threatening process or an example of a host-adapted virus?

Psittacid Adenovirus-2 (PsAdv-2) was identified in captive orange-bellied parrots (Neophema chrysogastor) during a multifactorial cluster of mortalities at the Adelaide Zoo, South Australia, and an outbreak of Pseudomonas aeruginosa septicaemia at the Tasmanian Department of Primary Industries, Parks, Water and Environment captive breeding facility, Taroona, Tasmania. This was the first time that an adenovirus had been identified in orange-bellied parrots and is the first report of PsAdv-2 in Australia. To investigate the status of PsAdv-2 in the captive population of orange-bellied parrots, 102 healthy birds from five breeding facilities were examined for the presence of PsAdv-2 DNA in droppings and/or cloacal swabs using a nested polymerase chain reaction assay. Additionally, eight birds released to the wild for the 2016 breeding season were similarly tested when they were recaptured prior to migration to be held in captivity for the winter. PsAdv-2 was identified in all breeding facilities as well as the birds recaptured from the wild. Prevalence of shedding ranged from 29.7 to 76.5%, demonstrating that PsAdv-2 is endemic in the captive population of orange-bellied parrots and that wild parrots may have been exposed to the virus. PsAdv-2 DNA was detected in both cloacal swabs and faeces of the orange-bellied parrots, but testing both samples from the same birds suggested that testing faeces would be more sensitive than cloacal swabs. PsAdv-2 was not found in other psittacine species housed in nearby aviaries at the Adelaide Zoo. The source of the infection in the orange-bellied parrots remains undetermined. In this study, PsAdv-2 prevalence of shedding was higher in adult birds as compared to birds less than one year old. Preliminary data also suggested a correlation between adenovirus shedding prevalence within the breeding collection and chick survival.

Recovery planning towards doubling wild tiger Panthera tigris numbers: Detailing 18 recovery sites from across the range

With less than 3200 wild tigers in 2010, the heads of 13 tiger-range countries committed to doubling the global population of wild tigers by 2022. This goal represents the highest level of ambition and commitment required to turn the tide for tigers in the wild. Yet, ensuring efficient and targeted implementation of conservation actions alongside systematic monitoring of progress towards this goal requires that we set site-specific recovery targets and timelines that are ecologically realistic. In this study, we assess the recovery potential of 18 sites identified under WWF's Tigers Alive Initiative. We delineated recovery systems comprising a source, recovery site, and support region, which need to be managed synergistically to meet these targets. By using the best available data on tiger and prey numbers, and adapting existing species recovery frameworks, we show that these sites, which currently support 165 (118-277) tigers, have the potential to harbour 585 (454-739) individuals. This would constitute a 15% increase in the global population and represent over a three-fold increase within these specific sites, on an average. However, it may not be realistic to achieve this target by 2022, since tiger recovery in 15 of these 18 sites is contingent on the initial recovery of prey populations, which is a slow process. We conclude that while sustained conservation efforts can yield significant recoveries, it is critical that we commit our resources to achieving the biologically realistic targets for these sites even if the timelines are extended.

Endoparasites of the Siberian tiger (Panthera tigris altaica)

There have been few reports on the diversity and prevalence of parasitic fauna of the endangered Siberian tiger, which inhabits the territory of the Russian Far East. The present review attempts to summarize the information about the parasitic fauna of wild Siberian tigers, which includes 15 helminths and 3 protozoan species. The most prevalent parasitic species was found to be Toxocara cati, followed by Toxascaris leonina. Another commonly recorded Platyhelminth species is Paragonimus westermani, which causes a lethal infection of the lung parenchyma in Siberian tigers. However, the information about infections by this fluke in the Siberian tigers is scarce, although P. westermani infections pose a serious health hazard to tiger populations. The nematodes Aelurostrongylus abstrusus and Thominx aerophilus are found in Siberian tigers with an occurrence rate of 2.3% and 19%, respectively. The information on the parasitic infestations of captive populations of Siberian tigers is also presented along with the sources of infection and hazards for the wild tiger populations in their natural environment.

Primary study of seroprevalence to virus pathogens in wild felids of South Primorie, Russia

Seroprevalence to nine different virus pathogens was estimated for Russian big cats (Amur tiger (Panthera tigris altaica Temminck, 1844) and far-eastern leopard (Panthera pardus orientalis (Schiegel, 1857))) in Southern Primorie, Russia (n = 25), in 2008–2016. Serum samples from smaller cats (Eurasian lynx (Lynx lynx (Linnaeus, 1758)) and far-eastern wildcat (leopard cat) (Prionailurus bengalensis euptilurus (Elliot, 1871))) were also tested for these pathogens (n = 19) during the same period. Felids of Russian Southern Primorie showed seroprevalence to eight out of nine tested pathogens, including highly dangerous feline immunodeficiency virus, feline leukemia virus, and canine distemper virus. Antibodies to feline panleukopenia virus were found to be much more widespread in cats (45%) than antibodies to any other virus. They were detected in samples taken from tigers, leopards, and far-eastern wildcats but not lynxes. Antibodies to pseudorabies virus were detected only in Amur tiger (29%), whose main prey is the most common carrier of the virus (wild boar), unlike for the other studied cats’ species.

Canine distemper viral infection threatens the giant panda population in China

We evaluated exposure to canine distemper virus (CDV) in eight wild giant pandas (Ailuropoda melanoleuca) and 125 unvaccinated domestic dogs living in and around Foping National Nature Reserve (FNNR), China. Seventy-two percent of unvaccinated domestic dogs (mixed breed) had neutralizing antibodies for CDV due to exposure to the disease. The eight wild giant pandas were naïve to CDV and carried no positive antibody titer. RT-PCR assays for hemagglutinin (H) gene confirmed the presence of CDV in 31 clinically ill dogs from several areas near FNNR. Genomic sequence analysis showed that the 21 canine CDV were highly homologous to each other and belonged to the Asian-1 genotype. They showed high homology with the GP01 strain sequenced from a fatally infected giant panda, suggesting cross-species infection. Observational and GPS tracking data revealed home range overlap in pandas and dogs around FNNR. This study shows that CDV is endemic in domestic dogs near FNNR and that cross-species CDV infection threatens the wild giant panda population.

Molecular cloning and functional characterization of eleven subtypes of interferon-α in Amur tigers (Panthera tigris altaica)

Interferon has a broad-spectrum of antiviral effects and represents an ideal choice for the development of antiviral drugs. Nonetheless, information about alpha interferon (IFN-α) is vacant in Amur tiger (Panthera tigris altaica), an endangered species and indigenous to northeast Asia. Herein, 11 PtIFN-αs genes, which encoded proteins of 164-165 amino acids, were amplified. Afterwards, expression and purification were conducted in Escherichia coli. In physicochemical analysis, PtIFN-αs were shown to be highly sensitive to trypsin and remained stable despite changes in pH and temperature. In feline kidney cells (F81)/vesicular stomatitis virus (VSV)/canine distemper virus (CDV)/avian influenza virus (AIV) systems, PtIFN-αs were demonstrated to have distinct antiviral activities, some of them (PtIFN-α and PtIFN-α9) inhibited viral transcription levels more effectively than the other subtypes including Felis catus IFN-α, an effective therapeutic agent used for viral infections clinically. Additionally, PtIFN-α and PtIFN-α9 can up-regulate the transcription and expression of p53, a tumor suppressor factor, which could promote apoptosis of virus-infected cells. In conclusion, we cloned and expressed 11 subtypes of PtIFN-α for the first time. Furthermore, PtIFN-α and PtIFN-α9 were likely to be more efficient against both chronic viral infections and neoplastic diseases that affect the Amur tiger population. It will be of significant importance for further studies to protect this endangered species.