Characterisation of morbilliviruses isolated from Lake Baikal seals (Phoca sibirica)

Study of Canine Distemper Virus Presence in Catalonia's Wild Carnivores through H Gene Amplification and Sequencing

Canine distemper virus (CDV) is recognised worldwide as an important pathogen in both domestic and wild carnivores. Few data are available on its impact and spread on the wildlife/wildlife-domestic animal-environment interface. This study, aimed at developing a conservation-oriented control strategy, analysed 89 sick or deceased animals from 2019 to 2023 at the Wildlife Rehabilitation Centre in Torreferrussa. RT-PCR and sequencing of the partial H gene were used to detect and analyse CDV in tissues. The total positive percentage was 20.22% (18/89), comprising 13 red foxes (44.8%), 4 European badgers (28.6%), and 1 American mink (4.5%), while 24 Eurasian otters tested negative. Phylogenetic analysis indicated that all of the CDV strains belong to the European lineage. Geographically distant individuals and different species shared the same viral strain, suggesting a strong capacity of CDV for interspecies and long-distance transmission. This calls for further research, particularly focusing on potential impacts of CDV on endangered carnivores.

Complete genomic sequencing of canine distemper virus with nanopore technology during an epizootic event

Canine distemper virus (CDV) endangers a wide range of wild animal populations, can cross species barriers and therefore representing a significant conservational and animal health risk around the globe. During spring to autumn 2021, according to our current estimates a minimum of 50 red foxes (Vulpes vulpes) died of CDV in Hungary, with CDV lesions. Oral, nasal and rectal swab samples were RT-PCR screened for Canine Distemper Virus from red fox carcasses. To investigate in more detail the origins of these CDV strains, 19 complete genomes were sequenced with a pan-genotype CDV-specific amplicon-based sequencing method developed by our laboratory and optimized for the Oxford Nanopore Technologies platform. Phylogenetic analysis of the complete genomic sequences and separately the hemagglutinin gene sequences revealed the role of the Europe lineage of CDV as a causative agent for the current epizootic. Here we highlight the growing importance of fast developing rapid sequencing technologies to aid rapid response activities during epidemics or epizootic events. We also emphasize the urgent need for improved surveillance of CDV, considering the epizootic capability of enzootic strains as reported in the current study. For such future efforts, we provide a novel NGS protocol to facilitate future genomic surveillance studies.

CANINE DISTEMPER VIRUS IN THE SEA OTTER (ENHYDRA LUTRIS) POPULATION IN WASHINGTON STATE, USA

Before 2001, all serosurveys for morbilliviruses in sea otters (Enhydra lutris) in California, Washington, and Alaska, US, documented a 0% seroprevalence. The first published serologic detections of morbillivirus in sea otters occurred in 2001-02 in live-captured Washington sea otters, with a documented 80% seroprevalence. We conducted a retrospective study of sea otter cases from 1989 to 2010 compiled at the US Geological Survey, National Wildlife Health Center to identify cases of morbilliviral disease in Washington sea otters and to characterize the disease using immunohistochemistry, reverse transcription (RT)-PCR, genetic sequencing, virus isolation, and serology. We identified six cases of morbilliviral disease and 12 cases of morbilliviral infection in this population of sea otters during 2000-10. Significant histologic findings included inflammation in the white and gray matter of the brain characterized by lymphoplasmacytic perivascular cuffing, neuronal necrosis, and satellitosis in gray matter and by spongiosis, myelin degeneration, spheroids, and gemistocytes in white matter. Intranuclear and intracytoplasmic viral inclusion bodies were found in neurons, Purkinje cells, and glia. Immunohistochemistry for canine distemper virus (CDV) showed positive staining in neurons, glial cells, and cell processes. A pan-morbillivirus RT-PCR with subsequent restriction endonuclease digestion or sequencing identified CDV. Virus isolation was not successful. Two sea otters with morbilliviral encephalitis showed greater antibody titers to CDV than phocine distemper virus. Histologic changes were confined to the central nervous system and resembled neurologic canine distemper in domestic dogs. Cases of sea otters with morbilliviral infection without histologic changes could represent early infections or incompletely cleared sublethal infections. We found that morbillivirus was present in the Washington sea otter population as early as 2000, and we provide a description of the pathology of canine distemper in sea otters.

Prolonged Infection of Canine Distemper Virus in a Mixed-Breed Dog

Canine distemper virus (CDV) is a major viral pathogen in domestic dogs, belonging to the Paramyxoviridae family, in the Morbillivirus genus. It is present worldwide, and a wide range of domestic animals and wild carnivores are at risk. In the absence of vaccination, dogs have a low chance of survival; however, if and when a dog survives, it can take an average of a few weeks to a few months to fully wipe out the virus. In the present study, we traced the course of infection of a 1-year-old mixed-breed male dog. The animal had an unusually long course of persistent CDV infection with a vector-borne heartworm (Dirofilaria immitis) co-infection. The dog excreted the CDV for 17 months with PCR positivity in urine samples collected from February 2019 through June 2020. The sequencing and phylogenetic analysis of the hemagglutinin gene revealed the CDV to be the member of the endemic Arctic-like genetic lineage. To the best of our knowledge, this report represents the longest documented canine infection of CDV. Notably, we highlight the necessity regarding CDV infectivity studies to better comprehend the transmission attributes of the virus.

Free-roaming dogs limit habitat use of giant pandas in nature reserves

Giant pandas (Ailuropoda melanoleuca) were historically hunted using dogs and are currently threatened by free-roaming dogs and their associated diseases. To better understand the spatial magnitude of this threat, we used a GIS approach to investigate edge effects of dogs on giant panda habitat. We first examined two nature reserves with contrasting free-roaming dog populations: Liziping, with many dogs (~0.44/km²), and Daxiangling, with few dogs (~0.14/km²). Spatial analysis indicated that giant pandas at Liziping (but not Daxiangling) showed a shift in habitat use away from populated areas consistent with a risk response to the foray distance of free-roaming dogs (10.9 km path-distance). Most giant panda locations (86%) from the 2014 census in Liziping were clustered around remote “dog-free zones.” Expanding this analysis across the entire giant panda range revealed that 40% of panda habitat is within the foray distance of dogs. Our assessment will inform dog control programs including monitoring, education, veterinary care, and other measures. We recommend that reserves designated for the release of translocated pandas receive priority consideration for dog control efforts. Only by understanding and managing complex interactions between humans, domestic animals, and wild animals can we sustain natural systems in a world increasingly dominated by humans.

Determinants of herder attitudes towards the Vulnerable snow leopard Panthera uncia in Yushu Prefecture, China

Yushu Prefecture in Qinghai Province provides some of the largest known stretches of habitat for the Vulnerable snow leopard Panthera uncia in China. People living in these areas are dependent on agropastoralism. Support from local communities is necessary for effective long-term conservation action for snow leopards, but loss of livestock to snow leopards can create financial burdens that induce negative attitudes and encourage retaliatory killing. We assessed factors driving herders' attitudes towards snow leopards and their conservation. We found that herders had higher agreement with positive than with negative statements about snow leopards despite nearly half reporting livestock loss to snow leopards within the last 5 years. No retaliatory killing was reported. Herders with more years of formal education and fewer livestock losses were more likely to have positive attitudes whereas those with lower importance of snow leopards to their religion, fewer livestock losses, and fewer years of education were more likely to have negative attitudes. Understanding the multifaceted mechanisms responsible for positive views towards species is imperative for reaching conservation goals. Our findings ascribe to the importance of increased education and adherence to Tibetan beliefs in promoting conservation tolerance towards snow leopards in Qinghai Province, but also indicate a need for further research into the impact of livestock loss.

Canine and Phocine Distemper Viruses: Global Spread and Genetic Basis of Jumping Species Barriers

Canine distemper virus (CDV) and phocine distemper (PDV) are closely-related members of the Paramyxoviridae family, genus morbillivirus, in the order Mononegavirales. CDV has a broad host range among carnivores. PDV is thought to be derived from CDV through contact between terrestrial carnivores and seals. PDV has caused extensive mortality in Atlantic seals and other marine mammals, and more recently has spread to the North Pacific Ocean. CDV also infects marine carnivores, and there is evidence of morbillivirus infection of seals and other species in Antarctica. Recently, CDV has spread to felines and other wildlife species in the Serengeti and South Africa. Some CDV vaccines may also have caused wildlife disease. Changes in the virus haemagglutinin (H) protein, particularly the signaling lymphocyte activation molecule (SLAM) receptor binding site, correlate with adaptation to non-canine hosts. Differences in the phosphoprotein (P) gene sequences between disease and non-disease causing CDV strains may relate to pathogenicity in domestic dogs and wildlife. Of most concern are reports of CDV infection and disease in non-human primates raising the possibility of zoonosis. In this article we review the global occurrence of CDV and PDV, and present both historical and genetic information relating to these viruses crossing species barriers.

The Canine Morbillivirus Strain Associated with An Epizootic in Caspian Seals Provides New Insights into the Evolutionary History of this Virus

Canine morbillivirus (canine distemper virus; CDV) is a worldwide distributed morbillivirus that causes sporadic cases and recurrent epizootics among an increasing number of wild, feral, and domestic animal species. We investigated the evolutionary history of CDV strains involved in the 1988 Lake Baikal (CDVPS88) and the 2000 Caspian Sea (CDVPC00) seal die-offs by recovery of full-length sequences from archived material using next-generation sequencing. Bayesian phylogenetic analyses indicated that CDVPC00 constitutes a novel strain in a separate clade (tentatively termed "Caspian") from the America-1 clade, which is comprised of older vaccine strains. The America-1/Caspian monophyletic group is positioned most basally with respect to other clades and is estimated to have separated from other CDV clades around 1832. Our results indicate that CDVPC00 recovered from the epizootic in the Caspian Sea in 2000 belongs to a previously undetected novel clade and constitutes the most ancestral wild-type CDV clade.

Marine Morbilliviruses: Diversity and Interaction with Signaling Lymphocyte Activation Molecules

Epidemiological reports of phocine distemper virus (PDV) and cetacean morbillivirus (CeMV) have accumulated since their discovery nearly 30 years ago. In this review, we focus on the interaction between these marine morbilliviruses and their major cellular receptor, the signaling lymphocyte activation molecule (SLAM). The three-dimensional crystal structure and homology models of SLAMs have demonstrated that 35 residues are important for binding to the morbillivirus hemagglutinin (H) protein and contribute to viral tropism. These 35 residues are essentially conserved among pinnipeds and highly conserved among the Caniformia, suggesting that PDV can infect these animals, but are less conserved among cetaceans. Because CeMV can infect various cetacean species, including toothed and baleen whales, the CeMV-H protein is postulated to have broader specificity to accommodate more divergent SLAM interfaces and may enable the virus to infect seals. In silico analysis of viral H protein and SLAM indicates that each residue of the H protein interacts with multiple residues of SLAM and vice versa. The integration of epidemiological, virological, structural, and computational studies should provide deeper insight into host specificity and switching of marine morbilliviruses.

Phylogenomic insights to the origin and spread of phocine distemper virus in European harbour seals in 1988 and 2002

The 1988 and 2002 phocine distemper virus (PDV) outbreaks in European harbour seals Phoca vitulina are among the largest mass mortality events recorded in marine mammals. Despite its large impact on harbour seal population numbers, and 3 decades of studies, many questions regarding the spread and temporal origin of PDV remain unanswered. Here, we sequenced and analysed 7123 bp of the PDV genome, including the coding and non-coding regions of the entire P, M, F and H genes in tissues from 44 harbour seals to shed new light on the origin and spread of PDV in 1988 and 2002. The phylogenetic analyses trace the origin of the PDV strain causing the 1988 outbreak to between May 1987 and April 1988, while the origin of the strain causing the 2002 outbreak can be traced back to between June 2001 and May 2002. The analyses further point to several independent introductions of PDV in 1988, possibly linked to a southward mass immigration of harp seals in the winter and spring of 1987-1988. The vector for the 2002 outbreak is unknown, but the epidemiological analyses suggest the subsequent spread of PDV from the epicentre in the Kattegat, Denmark, to haul-out sites in the North Sea through several independent introductions.

Advances in canine distemper virus pathogenesis research: a wildlife perspective

Canine distemper virus (CDV) has emerged as a significant disease of wildlife, which is highly contagious and readily transmitted between susceptible hosts. Initially described as an infectious disease of domestic dogs, it is now recognized as a global multi-host pathogen, infecting and causing mass mortalities in a wide range of carnivore species. The last decade has seen the effect of numerous CDV outbreaks in various wildlife populations. Prevention of CDV requires a clear understanding of the potential hosts in danger of infection as well as the dynamic pathways CDV uses to gain entry to its host cells and its ability to initiate viral shedding and disease transmission. We review recent research conducted on CDV infections in wildlife, including the latest findings on the causes of host specificity and cellular receptors involved in distemper pathogenesis.

Detection of Peste Des Petits Ruminants Virus (PPRV) Genome from Nasal Swabs of Dogs

Peste des petits ruminants virus (PPRV) one of the most important viruses of small ruminants has a restricted host range. We report here the presence of PPRV virus in the nasal swabs of 3 out of 12 dogs in a routine microarray screening. The presence of PPRV sequence was further confirmed by PCR and sequencing. The sequence analysis revealed that the PPRV virus has close similarities with the viruses present in Indian subcontinent but was not identical to the vaccine virus used in India. Results suggest possible crossing of species barrier but requires further serological evidences.

Molecular phylogeography of canine distemper virus: Geographic origin and global spreading

Canine distemper virus (CDV) (Paramyxoviridae-Morbillivirus) is a worldwide spread virus causing a fatal systemic disease in a broad range of carnivore hosts. In this study we performed Bayesian inferences using 208 full-length hemagglutinin gene nucleotide sequences isolated in 16 countries during 37 years (1975-2011). The estimated time to the most recent common ancestor suggested that current CDV strains emerged in the United States in the 1880s. This ancestor diversified through time into two ancestral clades, the current America 1 lineage that recently spread to Asia, and other ancestral clade that diversified and spread worldwide to originate the remaining eight lineages characterized to date. The spreading of CDV was characterized by several migratory events with posterior local differentiation, and expansion of the virus host range. A significant genetic flow between domestic and wildlife hosts is displayed; being domestic hosts the main viral reservoirs worldwide. This study is an extensive and integrative description of spatio/temporal population dynamics of CDV lineages that provides a novel evolutionary paradigm about the origin and dissemination of the current strains of the virus.

Does greater thermal plasticity facilitate range expansion of an invasive terrestrial anuran into higher latitudes?

Temperature has pervasive effects on physiological processes and is critical in setting species distribution limits. Since invading Australia, cane toads have spread rapidly across low latitudes, but slowly into higher latitudes. Low temperature is the likely factor limiting high-latitude advancement. Several previous attempts have been made to predict future cane toad distributions in Australia, but understanding the potential contribution of phenotypic plasticity and adaptation to future range expansion remains challenging. Previous research demonstrates the considerable thermal metabolic plasticity of the cane toad, but suggests limited thermal plasticity of locomotor performance. Additionally, the oxygen-limited thermal tolerance hypothesis predicts that reduced aerobic scope sets thermal limits for ectotherm performance. Metabolic plasticity, locomotor performance and aerobic scope are therefore predicted targets of natural selection as cane toads invade colder regions. We measured these traits at temperatures of 10, 15, 22.5 and 30°C in low- and high-latitude toads acclimated to 15 and 30°C, to test the hypothesis that cane toads have adapted to cooler temperatures. High-latitude toads show increased metabolic plasticity and higher resting metabolic rates at lower temperatures. Burst locomotor performance was worse for high-latitude toads. Other traits showed no regional differences. We conclude that increased metabolic plasticity may facilitate invasion into higher latitudes by maintaining critical physiological functions at lower temperatures.

Wild bird surveillance for avian paramyxoviruses in the Azov-black sea region of Ukraine (2006 to 2011) reveals epidemiological connections with Europe and Africa

Despite the existence of 10 avian paramyxovirus (APMV) serotypes, very little is known about the distribution, host species, and ecological factors affecting virus transmission. To better understand the relationship among these factors, we conducted APMV wild bird surveillance in regions of Ukraine suspected of being intercontinental (north to south and east to west) flyways. Surveillance for APMV was conducted in 6,735 wild birds representing 86 species and 8 different orders during 2006 to 2011 through different seasons. Twenty viruses were isolated and subsequently identified as APMV-1 (n = 9), APMV-4 (n = 4), APMV-6 (n = 3), and APMV-7 (n = 4). The highest isolation rate occurred during the autumn migration (0.61%), with viruses isolated from mallards, teals, dunlins, and a wigeon. The rate of isolation was lower during winter (December to March) (0.32%), with viruses isolated from ruddy shelducks, mallards, white-fronted geese, and a starling. During spring migration, nesting, and postnesting (April to August) no APMV strains were isolated out of 1,984 samples tested. Sequencing and phylogenetic analysis of four APMV-1 and two APMV-4 viruses showed that one APMV-1 virus belonging to class 1 was epidemiologically linked to viruses from China, three class II APMV-1 viruses were epidemiologically connected with viruses from Nigeria and Luxembourg, and one APMV-4 virus was related to goose viruses from Egypt. In summary, we have identified the wild bird species most likely to be infected with APMV, and our data support possible intercontinental transmission of APMVs by wild birds.

Variable transcription of pro- and anti-inflammatory cytokines in phocine lymphocytes following canine distemper virus infection

Canine distemper virus (CDV) is a highly contagious viral pathogen. Domesticated dogs are the main reservoir of CDV. Although phocine distemper virus was responsible for the recent epidemics in seals in the North and Baltic Seas, most devastating epidemics in seals were also caused by CDV. To further study the pathogenesis of CDV infection in seals, it was the aim of the present study to investigate the mechanisms of CDV induced immunosuppression in seals by analyzing the gene transcription of different pro- and anti-inflammatory cytokines in Concanavalin A (Con A) stimulated and non-stimulated phocine lymphocytes in vitro following infection with the CDV Onderstepoort (CDV-OND) strain. Phocine lymphocytes were isolated via density gradient centrifugation. The addition of 1 μg/ml Con A and virus was either performed simultaneously or lymphocytes were stimulated for 48 h with Con A prior to virus infection. Gene transcription of interleukin (IL)-6, IL-12 and tumor necrosis factor alpha (TNFα) as pro-inflammatory cytokines and IL-4, IL-10 and transforming growth factor beta (TGFβ) as anti-inflammatory cytokines were determined by using RT-qPCR. CDV-OND infection caused an initial increase of pro-inflammatory phocine cytokines mRNA 24h after infection, followed by a decrease in gene transcription after 48 h. A strong increase in the transcription of IL-4 and TGFβ was detected after 48 h when virus and mitogen were added simultaneously. An increased IL-10 production occurred only when stimulation and infection were performed simultaneously. Furthermore, an inhibition of IL-12 on IL-4 was noticed in phocine lymphocytes which were stimulated for 48 h prior to infection. In summary, the duration of the stimulation or the lymphocytes seem to have an important influence on the cytokine transcription and indicates that the outcome of CDV infection is dependent on various factors that might sensitize lymphocytes or make them more susceptible or reactive to CDV infection.

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

Fewer than 500 Amur tigers (Panthera tigris altaica) remain in the wild. Due to low numbers and their solitary and reclusive nature, tiger sightings across their range in the Russian Far East and China are rare; sightings of sick tigers are rarer still. Serious neurologic disease observed in several wild tigers since 2001 suggested disease emergence in this endangered species. To investigate this possibility, histology, immunohistochemistry (IHC), in situ hybridization (ISH), and reverse transcription-PCR (RT-PCR) were performed on tissues from 5 affected tigers that died or were destroyed in 2001, 2004, or 2010. Our results reveal canine distemper virus (CDV) infection as the cause of neurologic disease in two tigers and definitively establish infection in a third. Nonsuppurative encephalitis with demyelination, eosinophilic nuclear viral inclusions, and positive immunolabeling for CDV by IHC and ISH were present in the two tigers with available brain tissue. CDV phosphoprotein (P) and hemagglutinin (H) gene products were obtained from brains of these two tigers by RT-PCR, and a short fragment of CDV P gene sequence was detected in lymph node tissue of a third tiger. Phylogenetically, Amur tiger CDV groups with an Arctic-like strain in Baikal seals (Phoca siberica). Our results, which include mapping the location of positive tigers and recognition of a cluster of cases in 2010, coupled with a lack of reported CDV antibodies in Amur tigers prior to 2000 suggest wide geographic distribution of CDV across the tiger range and recent emergence of CDV as a significant infectious disease threat to endangered Amur tigers in the Russian Far East.

Recognition of disease emergence in wildlife is a rare occurrence. Here, for the first time, we identify and characterize a canine distemper virus (CDV), the second most common cause of infectious disease death in domestic dogs and a viral disease of global importance in common and endangered carnivores, as the etiology of neurologic disease and fatal encephalitis in wild, endangered Amur tigers. We establish that in 2010 CDV directly or indirectly killed ~1% of Amur tigers. Location of positive cases over an expansive geographic area suggests that CDV is widely distributed across the tiger range. Interspecies interactions are increasing as human populations grow and expand into wildlife habitats. Identifying animal reservoirs for CDV and identifying the CDV strains that are transmissible to and among wildlife species, including Amur tigers and sympatric critically endangered Amur leopards (Panthera pardus orientalis), is essential for guiding conservation and mitigation efforts.

Morbillivirus cross-species infection: is there a risk for humans?

The WHO has set regional elimination goals for measles eradication to be achieved by 2020 or earlier. A major question is whether an opportunity for veterinary virus infection of humans may arise when measles is eradicated and if vaccination is discontinued. Lessons have been learned from animal to human virus transmission i.e., HIV and more recently from severe acute respiratory syndrome and avian influenza virus infections. We are therefore alerted to the risk of zoonosis from the veterinary morbilliviruses. In this review the evidence from viral genomics, animal studies and cell culture experiments will be explored to evaluate the possibility of cross-infection of humans with these viruses.

Emergence of Canine Distemper Virus Strains With Modified Molecular Signature and Enhanced Neuronal Tropism Leading to High Mortality in Wild Carnivores

An ongoing canine distemper epidemic was first detected in Switzerland in the spring of 2009. Compared to previous local canine distemper outbreaks, it was characterized by unusually high morbidity and mortality, rapid spread over the country, and susceptibility of several wild carnivore species. Here, the authors describe the associated pathologic changes and phylogenetic and biological features of a multiple highly virulent canine distemper virus (CDV) strain detected in and/or isolated from red foxes ( Vulpes vulpes), Eurasian badgers ( Meles meles), stone ( Martes foina) and pine ( Martes martes) martens, from a Eurasian lynx ( Lynx lynx), and a domestic dog. The main lesions included interstitial to bronchointerstitial pneumonia and meningopolioencephalitis, whereas demyelination—the classic presentation of CDV infection—was observed in few cases only. In the brain lesions, viral inclusions were mainly in the nuclei of the neurons. Some significant differences in brain and lung lesions were observed between foxes and mustelids. Swiss CDV isolates shared together with a Hungarian CDV strain detected in 2004. In vitro analysis of the hemagglutinin protein from one of the Swiss CDV strains revealed functional and structural differences from that of the reference strain A75/17, with the Swiss strain showing increased surface expression and binding efficiency to the signaling lymphocyte activation molecule (SLAM). These features might be part of a novel molecular signature, which might have contributed to an increase in virus pathogenicity, partially explaining the high morbidity and mortality, the rapid spread, and the large host spectrum observed in this outbreak.

Analysis of thyroid hormones in serum of Baikal seals and humans by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunoassay methods: application of the LC-MS/MS method to wildlife tissues

Thyroid hormones (THs) are essential for the regulation of growth and development in both humans and wildlife. Until recently, TH concentrations in the tissues of animals have been examined by immunoassay (IA) methods. IA methods are sensitive, but for TH analysis, they are compromised by a lack of adequate specificity. In this study, we determined the concentrations of six THs, L-thyroxine (T(4)), 3,3',5-triiodo-L-thyronine (T(3)), 3,3',5'-triiodo-L-thyronine (rT(3)), 3,5-diiodo-L-thyronine (3,5-T(2)), 3,3'-diiodo-L-thyronine (3,3'-T(2)), and 3-iodo-L-thyronine (3-T(1)), in the serum of humans (n = 79) and wild Baikal seals (n = 37), by isotope ([(13)C(6)]-T(4))-dilution liquid chromatography (LC)-tandem mass spectrometry (MS/MS), and compared the TH levels with those measured by an electrochemiluminescent immunoassay (ECLIA) method. T(3) and T(4) were detected in all serum samples of both humans and Baikal seals, whereas T(1), 3,3'-T(2), and 3,5-T(2) were below the limit of detection (LOD). rT(3) was detected in Baikal seal sera at concentrations higher than T(3) in 28 seal samples, indicating an anomaly in deiodinase activity in Baikal seals. In humans, regression analyses of TH concentrations, measured by ECLIA and LC-MS/MS methods, showed significant correlations for T(4) (r = 0.852) and T(3) (r = 0.676; after removal of a serum sample with abnormal T(3) levels). In Baikal seals, a low correlation coefficient (r = 0.466) for T(4) levels and no correlation for T(3) levels (p = 0.093) were found between ECLIA and LC-MS/MS methods. These results suggest that interference by a nonspecific reaction against anti-T(3) and anti-T(4) antibodies used in the ECLIA can contribute to inaccuracies in TH measurement in Baikal seals. When the relationship between concentrations of THs in sera and dioxin-like toxic equivalents in blubber samples of Baikal seals (n = 19) was examined, a significantly negative correlation was found for serum T(4) levels measured by the LC-MS/MS method, but not for those measured by ECLIA. Thus, our results indicate that the LC-MS/MS method is more reliable and accurate for the elucidation of alteration in circulating TH levels in wildlife, as caused by environmental and physiological factors.

Canine distemper spillover in domestic dogs from urban wildlife

Canine distemper virus (CDV) causes a major disease of domestic dogs that develops as a serious systemic infection in unvaccinated or improperly vaccinated dogs. Domesticated dogs are the main reservoir of CDV, a multihost pathogen. This virus of the genus Morbillivirus in the family Paramyxoviridae occurs in other carnivorous species including all members of the Canidae and Mustelidae families and in some members of the Procyonidae, Hyaenidae, Ursidae, and Viverridae families. Canine distemper also has been reported in the Felidae family and marine mammals. The spread and incidences of CDV epidemics in dogs and wildlife here and worldwide are increasing.

Susceptibility of carnivore hosts to strains of canine distemper virus from distinct genetic lineages

Using the complete haemagglutinin (HA) gene and partial phosphoprotein (P) gene we investigated the genotype of canine distemper virus (CDV) strains recovered from two wildlife species in Mecklenburg-Vorpommern, Germany. Phylogenetic analyses demonstrated significant differences between the strains from raccoons Procyon lotor (family Procyonidae) obtained in 2007 and strains from red foxes Vulpes vulpes (family Canidae) obtained in 2008. The raccoon strains belonged to the CDV European wildlife lineage whereas the red fox strains belonged to the CDV Europe lineage. We combined our genetic sequence data with published data from 138 CDV stains worldwide to investigate the proposed importance of amino acid substitutions in the SLAM binding region of the CDV HA protein at position 530 (G/E to R/D/N) and 549 (Y to H) to the spread of domestic dog-adapted CDV strains to other carnivores. We found no evidence that amino acid 530 was strongly affected by host species. Rather, site 530 was conserved within CDV lineages, regardless of host species. Contrary to expectation, strains from non-dog hosts did not exhibit a bias towards the predicted substitution Y549H. Wild canid hosts were more frequently infected by strains with 549Y, a pattern similar to domestic dogs. Non-canid strains showed no significant bias towards either H or Y at site 549, although there was a trend towards 549H. Significant differences between the prevalence of 549Y and 549H in wild canid strains and non-canid strains suggests a degree of virus adaptation to these categories of host.

Canine distemper virus diversity in Lake Baikal seal (Phoca sibirica) population

Morbillivirus epizootics in marine mammals have been found in a variety of marine mammal species throughout the world over the past 20 years. The virus epizootic which resulted in significant mortality of Siberian seals (Phoca sibirica) in Lake Baikal during 1987-1988 was caused by the canine distemper virus (CDV). In our previous papers we provided evidence that the CDV similar to strain, identified in 1988, continued to circulate in Lake Baikal seals after 1988. The aim of this study was an up to date detection of CDV in Baikal seals and an evaluation of the genetic diversity of Baikal seal CDVs in comparison with other virus isolates and strains available in the GenBank on the basis of nucleotide sequence analysis of the phosphoprotein gene fragment. The majority of CDVs recovered from 1992 till 2007 were found to be similar to the one responsible for the epizootic of Lake Baikal seals. Phylogenetic analysis revealed that more than one genotype of CDV was circulating in Lake Baikal seals after the epizootic of 1987-1988.

Zoonoses in wildlife integrating ecology into management

Zoonoses in wildlife not only play an important ecological role, but pose significant threats to the health of humans, domestic animals and some endangered species. More than two-thirds of emerging, or re-emerging, infectious diseases are thought to originate in wildlife. Despite this, co-ordinated surveillance schemes are rare, and most efforts at disease control operate at the level of crisis management. This review examines the pathways linking zoonoses in wildlife with infection in other hosts, using examples from a range of key zoonoses, including European bat lyssaviruses and bovine tuberculosis. Ecologically based control, including the management of conditions leading to spill-overs into target host populations, is likely to be more effective and sustainable than simple reductions in wildlife populations alone.

Pathogen evolution and disease emergence in carnivores

Emerging infectious diseases constitute some of the most pressing problems for both human and domestic animal health, and biodiversity conservation. Currently it is not clear whether the removal of past constraints on geographical distribution and transmission possibilities for pathogens alone are sufficient to give rise to novel host-pathogen combinations, or whether pathogen evolution is also generally required for establishment in novel hosts. Canine distemper virus (CDV) is a morbillivirus that is prevalent in the world dog population and poses an important conservation threat to a diverse range of carnivores. We performed an extensive phylogenetic and molecular evolution analysis on complete sequences of all CDV genes to assess the role of selection and recombination in shaping viral genetic diversity and driving the emergence of CDV in non-dog hosts. We tested the specific hypothesis that molecular adaptation at known receptor-binding sites of the haemagglutinin gene is associated with independent instances of the spread of CDV to novel non-dog hosts in the wild. This hypothesis was upheld, providing compelling evidence that repeated evolution at known functional sites (in this case residues 530 and 549 of the haemagglutinin molecule) is associated with multiple independent occurrences of disease emergence in a range of novel host species.

Heterogeneity within the hemagglutinin genes of canine distemper virus (CDV) strains detected in Italy

Canine distemper virus (CDV) is a highly contagious viral pathogen causing lethal disease in dogs and other mammalians. A high degree of genetic variation is found between recent CDV strains and the old CDV isolates used in the vaccines and such genetic variation is regarded as a possible cause of the increasing number of CDV-related diseases in dogs. The H gene shows the greatest extent of genetic variation that allows for distinction of various lineages, according to a geographical pattern of distribution and irrespective of the species of identification. In the present study, hemagglutinin (H) genes obtained from field strains detected from clinical specimens of Italian dogs were analyzed genetically. Phylogenetic analysis revealed that a homogeneous group of CDV strains is widespread in Italian dogs, all which are included into the European lineage. Unexpectedly, strains 179/04 and 48/05 clustered along with CDVs of the Arctic lineage, the highest identity being to strain GR88 (98.0 and 98.4%aa, respectively). The full-length sequence of a red fox CDV strain, 207/00 was also determined and analyzed. The H protein of the fox CDV strain was unrelated to strains within the major European lineage. These results suggest that at least three different CDV lineages are present in Italy.

Canine vaccination--providing broader benefits for disease control

This paper reviews the broader benefits of canine vaccination to human and animal health and welfare with an emphasis on the impacts of mass dog vaccination against rabies in countries of the less-developed world. Domestic dogs are the source of infection for the vast majority (>95%) of cases of human rabies worldwide, and dogs remain the principal reservoir throughout Africa and Asia. Canine vaccination against rabies has been shown to dramatically reduce the number of cases in dogs, the incidence of human animal-bite injuries (and hence the demand for costly post-exposure prophylaxis) and the likely number of human cases, primarily in children. Further benefits include the mitigation of the psychological consequences of rabies in a community, improved attitudes towards animals and animal welfare and reduced livestock losses from canine rabies. Mass vaccination has recently been used in the conservation management of wild carnivore populations threatened by transmission of rabies and canine distemper virus from domestic dog populations. Vaccination of wildlife hosts directly may also provide an option for mitigating infectious disease threats. The development of integrated control measures involving public health, veterinary, wildlife conservation and animal welfare agencies is needed to ensure that control of canine diseases becomes a reality in Africa and Asia. The tools and delivery systems are all available--all that is needed is the political will to free the world from the ongoing tragedy of these diseases.

Phylogenetic characterization of canine distemper viruses detected in naturally infected dogs in North America

In 2004, six puppies and one adult dog from a total of four premises were subjected to necropsy evaluation. For five of the seven dogs, disease caused by canine distemper virus (CDV) infection was suspected based on clinical signs. In all of the dogs, a diagnosis of CDV infection was established by the presence of compatible gross and histologic lesions, immunohistochemical labeling for CDV antigen, and detection of CDV RNA by reverse transcription-PCR. To further characterize the CDV strains detected in the four cases, complete gene sequences were determined for the hemagglutinin (H) and fusion (F) protein genes, while partial gene sequencing was performed for the phosphoprotein gene. A total of 4,508 bases were sequenced for the CDV strains detected from each of the four cases. Two cases were found to have identical sequences except for 2 bases in the intergenic region of the F and H genes. Phylogenetic analysis strongly suggested an evolutionary relationship between sequences detected in these two cases and those of phocine distemper virus 2 and two other strains of CDV not previously detected in the continental United States. Clear phylogenetic relationships were not established for viruses detected in the two additional cases; however, one strain showed similarity to CDV strains detected in a panda from China. Importantly, the three CDV strains detected were demonstrated to be genetically distinct from known vaccine strains and strains previously reported in the continental United States.

Serum antibody levels against select bacterial pathogens in Atlantic bottlenose dolphins, Tursiops truncatus, from Beaufort NC USA and Charleston Harbor, Charleston, SC, USA

Concern over the emergence of zoonotic diseases in marine organisms is growing. In response to this concern, this study set out to measure antibody activities against bacterial pathogens in Atlantic bottlenose dolphins, Tursiops truncatus, from the coastal estuaries of NC and SC, USA. Individuals from Charleston SC harbor, a heavily industrialized shipping harbor estuary, and from Beaufort NC, a non-shipping estuary, were examined. Purified IgG was obtained from pooled sera using ammonium sulfate precipitation steps and protein-G procedures, which was then used to generate a panel of IgG-specific monoclonal antibodies. Two of these antibodies, mAbs BB-10-2 (IgG1) and BB-32-2 (IgG2b), were then used to determine total serum IgG concentrations using a sandwich capture ELISA. Circulating IgG levels were variable between individuals and between the two pods. MAb BB-10-2 was then used in an indirect ELISA to determine serum antibody activities against several common marine bacteria as well as the human pathogens E. coli and E. coli strain 0157:H7, Vibrio parahemolyticus, V. vulnificus, V. cholerae, Mycobacteria marinum, M. fortuitum, and M. chelonae. The highest antibody activities were against mycobacteria, two of which are zoonotic pathogens. Males had the highest antibody activities, thus suggesting low cell-mediated immunity against intracellular pathogens in these individuals. T-cell proliferation in response to Con-A, an indicator of cell-mediated immune function, was then measured in the Beaufort population. Males had the lowest proliferation responses, however a negative correlation between antibody activities and T-cell proliferation in individuals could not be established for either of the Mycobacteria species. Overall, antibody activities against all bacteria, including innocuous species such as V. anguillarum, V. natrigens, and M. xenopi were highly variable between individual dolphins and the two pods, with some animals exhibiting very high activities. These studies suggests that dolphin populations should be monitored by following the health and seroprevalence of pathogens of interest in select individual animals over time.

Detection and genetic characterization of canine distemper virus (CDV) from free-ranging red foxes in Italy

Fragments of the genes encoding the haemoagglutinin (H) and the nucleocapsid protein (N) of a canine distemper (CDV)-like virus affecting a red fox (Vulpes vulpes) were sequenced and analysed. The CDV-like virus detected in the fox was found to be not dissimilar, in both the H and N gene, from other CDVs spreading in Italy, as well as all over the world, and phylogenetic analysis on the H protein-encoding gene allowed to include all the Italian CDVs in the H European genotype.

Seroepidemiological survey of distemper virus infection in the Caspian Sea and in Lake Baikal

Forty Caspian seals were surveyed seroepidemiologically between 1993 and 1998 around the times of mass mortality that occurred in 1997 in the Caspian Sea and seven Baikal seals were also surveyed in 1998. Virus neutralizing tests and ELISA clearly suggested that distemper virus epidemic was caused in Caspian seals before the spring of 1997 and that CDV infection continued to occur in Lake Baikal in recent years.

Contact rates between wild and domestic canids: no evidence of parvovirus or canine distemper virus in crab-eating foxes

Evaluating the risk of disease spill-over from domestic dogs to wildlife depends on knowledge of inter-specific contact rates and/or exposure to aetiological agents in dog environments. Here, contact rates of crab-eating foxes (Cerdocyon thous) with sympatric domestic dog populations were measured over 25months in Amazon Brazil. Foxes and dogs were serologically and clinically monitored for exposure to canine parvovirus (CPV-2) and canine distemper virus (CDV), pathogens known to have caused wildlife population declines elsewhere. Twenty-two of 24 (92%) tagged foxes visited one or more houses in a median 2 (range 1-3) villages per night where dog densities ranged from 7.2 to 15.4 per km(2) (mean 9.5 per km(2)). Foxes spent an average 6.4% (0-40.3%) of their 10h nocturnal activity period in villages, the equivalent of 38m (range 0-242) per night. The rate of potential exposure to disease agents was thus high, though varied by 3 orders of magnitude for individual foxes. Overall, 46% of the fox population was responsible for 80% of all contacts. None of the 37 monitored foxes however showed serological or clinical evidence of infection with CPV-2 or CDV. Seroprevalences for CPV-2 and CDV antibodies in the local domestic dog population were 13% (3/23) and 9% (2/23), respectively, and 89% of 97 monitored pups born during the study presented clinical signs consistent with active CPV-2 infection (haemorrhagic diarrhoea, vomiting, rapid morbidity and emaciation). Although there was no evidence for infection with either virus in foxes, the high level of contact of foxes with peridomestic habitats suggests that the probability of potential spill-over infections from dogs to foxes is high.

Anthropogenic environmental change and the emergence of infectious diseases in wildlife

By using the criteria that define emerging infectious diseases (EIDs) of humans, we can identify a similar group of EIDs in wildlife. In the current review we highlight an important series of wildlife EIDs: amphibian chytridiomycosis; diseases of marine invertebrates and vertebrates and two recently-emerged viral zoonoses, Nipah virus disease and West Nile virus disease. These exemplify the varied etiology, pathogenesis, zoonotic potential and ecological impact of wildlife EIDs. Strikingly similar underlying factors drive disease emergence in both human and wildlife populations. These are predominantly ecological and almost entirely the product of human environmental change. The implications of wildlife EIDs are twofold: emerging wildlife diseases cause direct and indirect loss of biodiversity and add to the threat of zoonotic disease emergence. Since human environmental changes are largely responsible for their emergence, the threats wildlife EIDs pose to biodiversity and human health represent yet another consequence of anthropogenic influence on ecosystems. We identify key areas where existing expertise in ecology, conservation biology, wildlife biology, veterinary medicine and the impact of environmental change would augment programs to investigate emerging diseases of humans, and we comment on the need for greater medical and microbiological input into the study of wildlife diseases.

Antigenic differences in the H proteins of canine distemper viruses

Antigenic properties between new Japanese field isolates and vaccine strains of canine distemper virus (CDV) have been compared using four monoclonal antibodies (MAbs) (JD-5, JD-7, JD-11 and d-7) against the hemagglutinin (H) proteins of CDV. JD-5, JD-7 and JD-11 are newly established antibodies. Three MAbs, namely d-7, JD-5 and JD-11, reacted similarly to all the CDV strains examined. However, JD-7 reacted much more strongly with the vaccine strains and an old field isolate than the recent field isolates in immunofluorescence, radio immunoprecipitation and virus neutralization assays. These results indicate that an antigenic region in the H protein, concerned with neutralization and recognized by JD-7, has been altered in the recent field isolates.

Genotypes of canine distemper virus determined by analysis of the hemagglutinin genes of recent isolates from dogs in Japan

Canine distemper of domestic dogs is caused by canine distemper virus (CDV), a member of the morbilliviruses. It has been a highly contagious disease of great veterinary importance for centuries, but for the last several decades it has been controlled satisfactorily by modified live vaccines. In the 1990s, however, it was described that CDV strains genetically different from vaccine strains may have caused the disease in vaccinated dogs. The highest antigenic variation is found in the H protein. Therefore, in the present study, hemagglutinin (H) genes obtained from current vaccines and field isolates and amplified directly from clinical specimens were genetically analyzed by restriction fragment length polymorphism assay and sequencing. Phylogenetic analysis of the H-gene amino acid sequences revealed that at least two CDV genotypes are circulating among dogs in Japan; one is a genotype to which almost all Japanese CDV isolates belong and the other has not been previously described. Both are separate and independent from the other lineages or genotypes of vaccine strains, as well as European and U.S. CDV isolates. The results suggest that CDV has also evolved in Japan, and further studies will be needed for an evaluation and possible improvement of the efficacies of current CDV vaccines.

Genetic analysis of the central untranslated genome region and the proximal coding part of the F gene of wild-type and vaccine canine distemper morbilliviruses

Located between the open reading frames encoding the matrix (M) and the fusion (F) protein the morbillivirus genome contains an unusually large non-coding intercistronic region (M-F UTR) of up to 5.6% of the full length genome. Any function(s) of this region have largely remained obscure. Here, we analyze the M-F UTR and the proximal coding part of the downstream F gene of several recent canine distemper morbillivirus (CDV) wild-type (wt) isolates and vaccine strains. While the F gene coding part appeared to be highly conserved (about 93% homology), a considerable degree of strain-specific variation of up to 21.4% was evident when comparing the M-F UTR. Phylogenetic analysis revealed a co-circulation of several contemporary CDV genotypes within a close geographic range (central Europe). A remarkably distinct CDV wt lineage, so far detected only in mustelids, is displayed. A rather non-scattered pattern of mutations within the M-F UTR suggested superimposition of RNA sequence and/or secondary structure constraints. Extensive folding in the long (460 nt) and moderately GC-rich 5'-UTR of the F mRNA was evident, particularly around the putative F protein translation initiation codon (AUG461 of the Onderstepoort vaccine strain). The region immediately preceding the putative F initiation site also harbored the only mutation unique to both vaccine strains within the F-5'UTR (position 455: Awt vs. Cvac). The putative F protein start codon, AUG461, was found to be mutated to AUA or GUA in all wt isolates analyzed and in another vaccine strain (Rockborn). Possible consequences for F protein translation initiation in wt CDV are discussed.

Molecular identification of a recent type of canine distemper virus in Japan by restriction fragment length polymorphism

Restriction fragment length polymorphism analysis was used to differentiate recent field viruses of canine distemper virus (CDU) from vaccine strains. Virus genomes were amplified by using reverse transcriptase-polymerase chain reaction in part of the haemagglutinin gene. After digestion with EcoRV, the PCR products of recent field isolates were cut into two fragments that differ from the uncut form of old strains including all of vaccine strains. This method could be applied to fresh or stored brains, spleens and peripheral blood mononuclear cells of infected dogs. This molecular approach is useful for determining the causative agent of postvaccinated CDV infection.

Morbillivirus infections in aquatic mammals

Morbillivirus infections which were not documented in aquatic mammals until 1988, have caused at least five epizootics in these species during the last 10 years. Affected populations include European harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) in 1998, Baikal seals (Phoca siberica) in Siberia from 1987-1988, striped dolphins (Stenella coeruleoalba) in the Mediterranean Sea from 1990-1992 and bottlenose dolphins (Tursiops truncatus) along the eastern coast of the United States from 1987-1988 and in the Gulf of Mexico from 1993-1994. Clinical signs and lesions in affected animals were similar to those of canine distemper. Lesions were mainly seen in lung, central nervous and lymphoid tissues and included formation of intranuclear and intracytoplasmic inclusion bodies. Syncytia were commonly found in lung and lymphoid tissues of cetaceans but not of pinnipeds. Antigenic and molecular biological studies indicate that a newly discovered morbillivirus, termed phocine distemper virus, and canine distemper virus were responsible for recent pinniped epizootics; cetacean die-offs were caused by strains of a second, newly recognized cetacean morbillivirus. Serological evidence of morbillivirus infection has been identified in a broad range of marine mammal populations and recent epizootics probably resulted from transfer of virus to immunologically-naive populations.

Molecular epidemiology of animal virus diseases

In this review the application of methods of molecular epidemiology, particularly the combined approach of amplifying defined fragments of viral genomes using the polymerase chain reaction and subsequent nucleotide sequencing analysis, is described. Emphasis is put on examples of a few important diseases (e.g. those caused by morbilliviruses, rhabdoviruses, pestiviruses and aphthoviruses) to demonstrate the impact of this methodology. Molecular epidemiology is already an important and very sensitive tool to study the evolution of viruses at a level superior to previous methodologies and providing a better understanding of epidemiological relationships.

Analysis of the haemagglutinin gene of current wild-type canine distemper virus isolates from Germany

The haemagglutinin (H) gene sequences from three wild-type canine distemper viruses (CDV) isolated during 1994-1995 were sequenced to determine whether contemporary strains had undergone significant genetic changes relative to the currently used vaccine strains. The new isolates were closely related to each other (> 99%) and displayed about 90-91% sequence homology to the Onderstepoort and Convac vaccine strains. There were one to four additional potential glycosylation sites compared to the vaccine strains which were also present in a German dog CDV isolate dating from 1990. However, only a very slight reduction in neutralizing titre against the new isolates was found when compared with the Onderstepoort and Rockborn vaccine strains. Cysteine and proline residues were well conserved indicating a conserved three dimensional structure for the protein. By phylogenetic analysis the recent isolates showed a narrow clustering close to the previous canine isolates indicating a linear pattern of evolutionary changes. A comparison with published CDV H gene sequences suggested the presence of different lineages of CDV on a global scale and possible cocirculation of more than one genotype of CDV.

Detection of animal pathogens by using the polymerase chain reaction (PCR)

The polymerase chain reaction (PCR) is a nucleic acid-based technique that enables the rapid and sensitive detection of specific micro-organisms. Although this technique is widely used in veterinary research, it has not yet found applications in routine microbiological analysis of veterinary clinical samples. However, advances in sample preparation together with the increasing availability of specific gene sequences will probably lead to the more widespread diagnostic use of PCR in the future. PCR is likely to have a strong impact in the epidemiology, treatment and prevention of animal infectious diseases.

Canine distemper virus--a morbillivirus in search of new hosts?

Canine distemper morbillivirus (CDV) induces a multisystemic, often fatal disease in a wide and seemingly expanding host range among the Carnivora. Several genotypes of an otherwise monotypic virus species co-circulate in a geographically restricted pattern. Interspecies transmissions frequently occur, often leading to devastating epizootics in highly susceptible or immunologically naive populations.

Rinderpest and other animal morbillivirus infections: comparative aspects and recent developments

The genus morbillivirus presently comprises measles virus of man, rinderpest virus (RPV), peste des petits ruminants virus (PPRV), and canine distemper virus (CDV). 'Emerging' morbilliviruses, such as phocid distemper virus (PDV) of seals, dolphin (DMV) and porpoise morbillivirus (PMV) have probably been present for a long period of time and outbreaks are possibly related to introduction into a highly susceptible population and/or be the result of interspecies transmission. In this review some comparative aspects of morbillivirus infections, particularly with respect to rinderpest and canine distemper viruses, are presented. Topics include pathogenesis, epidemiology, molecular phylogeny, diagnosis and prophylaxis. Recent developments in molecular biology have created tools which have enabled us to achieve a better understanding of morbillivirus infections at the nucleic acid level ('molecular epidemiology') while recombinant DNA technology has allowed new bivalent recombinant vaccines with improved heat stability to be produced.

Canine distemper virus in Lake Baikal seals (Phoca sibirica)

The virus epizootic which resulted in significant mortality in Siberian seals (Phoca sibirica) in Lake Baikal during 1987/88 was caused by canine distemper virus. Sequence analysis of the virus glycoprotein genes revealed that it was most closely related to recent European field isolates of canine distemper virus. This paper presents evidence that the same virus continued to circulate in seals in Lake Baikal after the initial epizootic. Three out of 45 brain tissue samples collected from seals culled in the spring of 1992 were positive for canine distemper virus-specific nucleic acid by the reverse transcription/polymerase chain reaction and the sequences were closely related to that of the original virus isolated in 1988.