Canine Distemper Virus Lineages Research Articles

Phylogenetic analysis linked fatal neurologic disease in leopards (Panthera pardus) to Asia-5 lineage of canine distemper virus in Nepal

Canine distemper virus (CDV) is responsible for a highly contagious and often fatal neurological disease that affects various carnivores, including domestic dogs. In Nepal, recent reports of CDV exposure and illness in leopards (Panthera pardus) have raised concerns about the transmission of the virus among domestic dogs and wild carnivores. To investigate the genetic lineage and spread of CDV, our study utilized archived post-mortem samples from four leopards that exhibited clinical signs suggestive of canine distemper infection. These leopards were rescued in the Palpa, Dolakha, Kathmandu, and Parbat districts. Our phylogenetic analysis revealed that the CDV strains circulating among the leopards belong to the Asia-5 lineage, which is also prevalent among dogs and wild carnivores in Nepal and neighboring India. The genetic relatedness between the leopard CDV sequences and those from both dogs and other carnivores within the Asia-5 lineage suggests that leopards in Nepal may have acquired the virus from multiple sources, potentially facilitated by their generalist dietary habits preying on dogs and even mesocarnivores. Furthermore, we inspected specific amino acid substitution in the hemagglutinin gene of leopard CDV, which also suggests possible transmission from both domestic dogs and non-canid hosts, although further research is needed to draw definitive conclusions. Given the vulnerable state of the leopard population in Nepal, already threatened by poaching and retaliatory killing, the emergence of CDV as a potential novel threat is deeply concerning. Comprehensive surveillance studies are essential to understand the dynamics of CDV spillover and to develop informed interventions. Urgent measures, including vaccination programs and effective control of the dog population, are needed to mitigate the impact of this disease and safeguard the future of Nepal's leopards and other wild carnivores.

A novel and highly divergent Canine Distemper Virus lineage causing distemper in ferrets in Australia

Canine distemper virus (CDV) causes a highly contagious systemic infection in an array of animal species. In this study we report an outbreak of distemper in ferrets in two research facilities in Australia, caused by a novel lineage of CDV. While the CDV strain caused mainly mild symptoms in ferrets, histopathology results presented a typical profile of distemper pathology, with multi-system virus replication. Through the development of a discriminatory PCR, paired with full genome sequencing, we revealed that the outbreak was caused by a novel lineage of CDV. The novel CDV lineage was highly divergent, with less than 93% similarity across the H gene to other described lineages, including the vaccine strain, and diverged approximately 140–400 years ago. Enhanced surveillance to determine the prevalence of CDV in ferrets, dogs and other at-risk species is critical to better understand the presence and diversity of CDV in Australia currently.

The First Report and Phylogenetic Analysis of Canine Distemper Virus in Cerdocyon thous from Colombia.

Simple SummaryCanine distemper virus (CDV) is the etiological agent of a highly frequent viral disease of domestic and wild carnivores. It poses a threat for the conservation of endangered species. Our aim was to assess the presence and phylogenetic characterization of CDV from naturally infected Crab-eating Fox (Cerdocyon thous) from Colombia. We confirm for the first time the circulation of CDV South America/North America-4 Lineage in Crab-eating Fox. Our results are crucial for the understanding of the interspecies transmission of CDV in the domestic/wild interface and for the prevention and control of such an important multi-host pathogen.Canine distemper virus (CDV) is the etiological agent of a highly prevalent viral infectious disease of domestic and wild carnivores. This virus poses a conservation threat to endangered species worldwide due to its ability to jump between multiple species and produce a disease, which is most often fatal. Although CDV infection has been regularly diagnosed in Colombian wildlife, to date the molecular identity of circulating CDV lineages is currently unknown. Our aim was to evaluate the presence and phylogenetic characterization of CDV detected in samples from naturally infected Cerdocyon thous from Colombia. We sequenced for the first time the CDV infecting wildlife in Colombia and demonstrated the presence of South America/North America-4 Lineage with a higher relationship to sequences previously reported from domestic and wild fauna belonging to the United States of America. Our results are crucial for the understanding of the interspecies transmission of CDV in the domestic/wild interface and for the prevention and control of such an important multi-host pathogen.

Origin and spreading of canine morbillivirus in South America

Canine distemper virus (CDV) is a Morbillivirus (Canine morbillivirus) that greatly impacts domestic and wildlife carnivores worldwide. The CDV RNA genome has high genetic variability, evidenced by several lineages that follow a global geographic pattern. The evolutionary trajectories and population dynamics of CDV lineages are still unclear and debatable, particularly in South America, where relatively few sequences are available. We performed phylogenetic and Bayesian analyses using an updated dataset of the highly variable hemagglutinin (H) gene, including seven South American countries. The time to the most recent common ancestor (tMRCA) of the current CDV lineages was dated to the early 1900s in North America. Maximum likelihood and Bayesian maximum clade credibility phylogenies showed similar topologies with two main branches (L1 and L2) corresponding to the NA1 lineage (L1) and the remaining lineages worldwide (L2). The four circulating lineages in South America (EU1/SA1, SA2, SA3, NA4/SA4) arose from independent migration events from North America and Europe. North American strains colonized most northern South American countries via Ecuador and then Colombia and Peru, originating the SA3 and NA4/SA4 lineages during their spread. The entry and expansion in the southern part of South America (Argentina, Brazil, Chile, and Uruguay) occurred through three independent migration events and gave rise to the EU1/SA1 and SA2 lineages. South American lineages have specific combinations of amino acids under positive selection that constitute signatures of taxonomic and evolutionary relevance. Our findings provide a comprehensive scenario for the origin and migration routes of Canine morbillivirus in South America and highlight the importance of phylodynamics in understanding the geographic patterns of modern genetic variability.

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 Wild Carnivore Populations from the Czech Republic (2012-2020): Occurrence, Geographical Distribution, and Phylogenetic Analysis.

Canine distemper is a highly contagious viral disease in carnivores and represents a serious threat for both wild and domestic animals. The aim of our study was to monitor the occurrence of the canine distemper virus in wildlife from the Czech Republic, reveal the H gene heterogeneity in positive samples and perform subsequent phylogenetic analysis. In total, 412 wild animals of 10 species were included in the study: 219 red foxes (Vulpes vulpes), 79 European badgers (Meles meles), 47 European otters (Lutra lutra), 40 stone martens (Martes foina), 10 pine martens (M. martes), 7 raccoons (Procyon lotor), 5 undetermined martens (Martes sp.), 2 wolves (Canis lupus), 1 European polecat (Mustela putorius), 1 free-ranging ferret (Mustela putorius furo), and 1 free-ranging American mink (Neovison vison). Most animals were found dead or were killed by hunters during hunting seasons in the years 2012–2020 and came from all 14 regions of the Czech Republic. In the animals that were hunted, symptoms such as apathy, loss of shyness or disorientation were reported. Canine distemper virus (CDV) was detected by real-time RT-PCR in the tissues of 74 (18%) of the animals, including 62 (28%) red foxes, 4 (10%) stone martens, 3 (43%) raccoons, 2 (20%) pine martens, 2 (2.5%) European badgers and 1 (20%) undetermined marten. There was a statistical difference in positivity among animal species (p < 0.0001), regions (p = 0.0057), and the years of sampling (p = 0.0005). To determine the genetic characteristics of circulating variants of CDV in wildlife, 23 of 74 CDV variants were partially sequenced. Phylogenetic analysis showed that 21 variants belonged to the European lineage and two strains belonged to the European-Wildlife lineage. This study provides the first comprehensive overview of the prevalence and spatial distribution of CDV in wildlife in the Czech Republic, including molecular phylogenetic analysis of currently circulating CDV lineages.

A preliminary studio for the F gen of Canine Distemper Virus as target for phylogenetic analysis

The Canine Distemper is one of the main infectious diseases in domestic dogs. The introduction of live attenuated-viral vaccines has helped to maintain the disease under control. However, in the past few decades it has been observed worldwide a rising number of cases even in vaccinated animals. The Canine Distemper Virus lineages circulating in the world have been described based on the hemagglutinin analyses, due to its high degree of genetic variability. Recently, new studies have reported greater variations in the amino acidic sequence of a region in the fusion protein. In order to determine the variability of the field strains in comparison with the vaccines and strains from other lines, in this dissertation the genomic variability of the Fsp region from the canine distemper virus fusion protein gene is analyzed. With this purpose, a Polymerase Chain Reaction with reverse transcription, capable of amplifying this variable region, was implemented, and identified through its nucleotide sequence. These sequences were compared with vaccine strains and with field strains of known lineages. Additionally, a phylogenetic tree was built for this variable region. The results of the nucleotides comparison show that the field strains have more homology to the vaccine strain Onderstepoort and according to phylogeny, it would belong to the America 1 lineage.

First complete genome sequence of Asia-4 lineage of canine distemper virus in China

We previously reported a novel Asia-4 lineage of canine distemper virus (CDV) in China based on the H gene. In the present study, a Chinese CDV NJ(11)2 strain of the Asia-4 lineage from Nanjing, China was isolated and its whole genome sequence was obtained. The CDV NJ(11)2 strain clustered with the Thai strains of the Asia-4 lineage in the phylogenetic tree of the complete genome. Phylogenetic analysis based on six individual genes also revealed that the CDV NJ(11)2 strain belonged to Asia-4 lineage. According to the individual N and H genes, two Chinese strains XJ4 from Xinjiang and C11 from Chengdu were clustered with the Asia-4 lineage. These results suggested that the Asia-4 lineage of CDV appeared in the three regions of China. Interestingly, Chinese BJ16B35 strain was identified as a novel putative recombinant virus from a major parent virus of the Asia-1 lineage and a minor parent virus of the America-1 lineage. The first genome sequence of Chinese Asia-4 lineage of CDV contributes to the knowledge of the evolution and molecular epidemiology of CDV infection.

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.

Genetic characterization of canine distemper virus from wild and domestic animal submissions to diagnostic facilities in Canada

Traditionally considered an agent affecting domestic dogs, canine distemper virus (CDV) is now well known for an ability to infect a broad range of hosts. In Ontario, domestic dogs are routinely vaccinated and clinical disease attributed to CDV infection in this population is infrequent. CDV has been regularly documented in Ontario wildlife spanning at least 4 decades however, the molecular identity of circulating CDV strains is currently unknown. Our objective was to investigate the molecular identities of and genetic relationships between CDV detected in wild and domestic animals from Canada, across multiple host species and over time. Samples were opportunistically collected from submissions to the Ontario-Nunavut node of the Canadian Wildlife Health Cooperative and the Animal Health Laboratory in Guelph, Ontario. RT-PCR was used to confirm CDV diagnosis, and the hemagglutinin gene was sequenced. Phylogenetic relationships were inferred, and the geographic distribution of clades was visualized using a geographic information system. Phenetic relationships between sequences were investigated with a median joining network analysis and through mixed multivariable linear regression. CDV sequences from ten wild and domestic species were characterized into seven lineages, that overlapped geographically and temporally. The predominant lineage circulating in Ontario wildlife, denoted Canada-1, has not been previously described to the authors knowledge. Our analysis indicates that the Canada-1 lineage is most genetically similar to America-1 sequences, however according to current methodology represents a distinct lineage. Multiple co-circulating CDV lineages were also identified, and raccoons appear to play an important role in the maintenance and transmission of these heterogeneous lineages in Ontario. This study also confirmed the presence of CDV from a lineage not found to be circulating in Ontario wildlife, in a domestic dog imported into Ontario from South America. Therefore, travel and the trade of animals may be an important avenue for the introduction of novel CDV lineages. It remains unclear whether and to what extent the genetic heterogeneity identified poses a risk to the efficacy of current vaccines. Increasing viral activity and continued antigenic drift resulting in partial protection or vaccine failure remains a concern.

New members to Arctic-like lineage of canine distemper virus from Turkey

Canine distemper virus (CDV) causes a multisystemic fatal disease, briefly named as distemper, in domestic and wild animals. Molecular characterization studies serve to identify local strains, accordingly, helps to determine the scope of vaccination in prevention of distemper. We aimed with this study to update the molecular status of CDV in domestic dogs in Turkey.Sequence analysis of the H gene revealed that novel Turkish sequences formed a separated clade in Arctic-like lineage. Italian clade which mainly included strains originated from wild canid or non-canid localized nearly to novel Turkish clade. Codons 530th and 549th determining the affinity of domestic or wild animals to distemper were Asparagine and Tyrosine, respectively.This report presented the presence of CDV strains belonging to Arctic-like lineage for the first time in domestic dogs in Turkey. The findings pave the way for the reassessment of the circulation and geographical shifting of Arctic-like lineages of CDV.

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.

Codon usage bias in the H gene of canine distemper virus

Canine distemper virus (CDV), a non-segmented single negative-stranded RNA (ssRNA), is the etiological agent of canine distemper. Canine distemper is a highly contagious and lethal viral disease in domestic dogs and wild carnivores. Study of the evolution of CDV presents an essential key to improve the vaccine efficacy. In this study, a total of 328 full-length CDV hemagglutinin (H) gene sequences were subjected to phylogenetic, amino acid mutations, and codon usage analysis. In accordance with previous study, CDV genotypes consisted of fifteen lineages. The unique amino acid substitution sites in each CDV lineages have been identified for the first time, including America-1 (Q330H), America-2 (I585S), Asia-1 (A359V), Asia-2 (H61R), Asia-3 (P108Q), Asia-4 (K213T), India-1/Asia-5(S497P), Arctic (S20L), Africa-1(N489S), Colombian (V41I), EWL (I44V), Europe (D560E), Europe-1/South America-1(K161Q), South America-2 (R580Q), and East African (S214A). Codon usage analysis indicated that H gene exhibited low codon usage bias and further neutrality plot analysis demonstrated that natural selection played a dominated role in driving CPV evolution. The effective number of codons (ENC) plots show that all the different sequences are below the standard curve, indicating that mutational pressure is not the only factor affecting CUB but other forces, including natural selection. The neutrality analysis showed that the slope of the regression line was 0.1501, indicating natural selection dominates directional mutation pressure in driving the codon usage pattern. In addition, nucleotide composition, relative synonymous codon usage value, dinucleotide content, and geographical distribution have been proven to influence the codon usage bias of the CDV H gene. The novel findings enhanced the understanding of CDV evolution.

Genotyping of Canine Distemper Virus Lineage in Clinically Infected Dogs in Puducherry, Southern India

Aims: This study aimed to determine the Canine Distemper Virus (CDV) lineage circulating in the Puducherry region (Southern India) and how they are genetically and antigenically related to the vaccine and other known CDV lineages around the world.&#x0D; Study Design: The study involved genetic characterization of the canine distemper virus strains/lineages circulating in the clinically suspected dogs in the field.&#x0D; Place and Duration of Study: Department of Veterinary Clinical Complex, Animal Husbandry Department, Private Veterinary Clinics, NGOs like Bark India, People for Animals organization, Puducherry between January 2018 and December 2019.&#x0D; Methodology: The ocular and nasal swabs were collected from 40 dogs suspected for canine distemper from Puducherry state (Southern India). Following viral RNA Extraction and cDNA synthesis; the cDNAs were screened for virus by targeting the CDV Nucleocapsid (N) gene using Reverse Transcriptase PCR. Further, the N gene positive cDNAs were genetically characterized for sequence analysis of the CDV hemagglutinin (H) gene.&#x0D; Results: A total of 15 (37.5%) out of 40 ocular/ nasal swabs were found to be CDV positive by RT-PCR targeting the N gene. The sequence analysis of the H gene revealed forty-nine non-synonymous and thirty-three synonymous mutations (out of 356 amino acids) in comparison with vaccine strain. The vaccine virus (Onderstepoort strain), which is related to the America 1 lineage, possessed high level of (30 – 35 i.e. more than 10%) amino acid divergence with the CDV sequences analysed in this study. The Phylogenetic analysis revealed that the present CDV sequences formed a separate monophyletic group with the CDV sequences of other Indian dogs and the Indian wildlife (Lion) and is clustered away from the vaccine strain. The CDV sequences were closer to the CDVs of Africa - 2 lineage than the other Asian lineages. The Recombination analysis revealed no potential breakpoints and recombination events.&#x0D; Conclusion: Together, these findings highlighted the possible existence of the novel Indian CDV lineage/s distinct from the vaccine strain and from other known Asian lineages.

GENETIC CHARACTERISTICS OF CANINE DISTEMPER VIRUSES CIRCULATING IN WILDLIFE IN THE UNITED STATES.

Canine distemper virus (CDV) is a highly contagious disease of wild and domestic mammals. Maintenance of CDV among wildlife plays an important role in the disease epidemiology. Wild animals, including raccoons (Procyon lotor) and gray foxes (Urocyon cinereoargenteus), serve as reservoirs of CDV and hamper the control of the disease. Recently, we discovered that at least three different CDV lineages (America-3 [Edomex], America-4, and America-5] that are genetically different from the available vaccine strains are circulating in domestic dogs in the United States. Because wildlife serve as a reservoir for the virus, it is important to determine if wildlife play a role in the maintenance and spread of these lineages. To determine the genetic characteristics of circulating strains of CDV in wildlife in various geographic regions in the United States, we studied the nucleotide sequences of the hemagglutinin (H) gene of 25 CDV strains detected in nondomestic species. The species included were free-ranging wildlife: three fishers (Martes pennanti), six foxes, one skunk (Mephitis mephitis), 10 raccoons, two wolves (Canis lupus), and one mink (Neovison vison). Strains from two species in managed care, one sloth (Choloepus didactylus) and one red panda (Ailurus fulgens), were also evaluated. Phylogenetic analysis of the H genes indicated that in addition to America-3, America-4, and America-5 lineages, there are at least two other lineages circulating in US wildlife. One of these includes CDV nucleotide sequences that grouped with that of a single CDV isolate previously detected in a raccoon from Rhode Island in 2012. The other lineage is independent and genetically distinct from other CDV strains included in the analysis. Additional genetically variable strains were detected, mainly in raccoons, suggesting that this species may be the host responsible for the genetic variability of newly detected strains in the domestic dog population.

Phylogenetic evidence of the intercontinental circulation of a Canine distemper virus lineage in the Americas

Canine distemper virus (CDV) is the cause of a multisystem disease in domestic dogs and wild animals, infecting more than 20 carnivore and non-carnivore families and even infecting human cell lines in in vitro conditions. Phylogenetic classification based on the hemagglutinin gene shows 17 lineages with a phylogeographic distribution pattern. In Medellín (Colombia), the lineage South America-3 is considered endemic. Phylogenetic studies conducted in Ecuador using fragment coding for the fusion protein signal peptide (Fsp) characterized a new strain belonging to a different lineage. For understanding the distribution of the South America-3 lineage in the north of the South American continent, we characterized CDV from three Colombian cities (Medellín, Bucaramanga, and Bogotá). Using phylogenetic analysis of the hemagglutinin gene and the Fsp region, we confirmed the circulation of CDV South America-3 in different areas of Colombia. We also described, for the first time to our knowledge, the circulation of a new lineage in Medellín that presents a group monophyletic with strains previously characterized in dogs in Ecuador and in wildlife and domestic dogs in the United States, for which we propose the name “South America/North America-4” due its intercontinental distribution. In conclusion, our results indicated that there are at least four different CDV lineages circulating in domestic dogs in South America: the Europe/South America-1 lineage circulating in Brazil, Uruguay, and Argentina; the South America-2 lineage restricted to Argentina; the South America-3 lineage, which has only been reported in Colombia; and lastly an intercontinental lineage present in Colombia, Ecuador, and the United States, referred to here as the “South America/North America-4” lineage.

Phylogenetic analysis of haemagglutinin gene deciphering a new genetically distinct lineage of canine distemper virus circulating among domestic dogs in India.

Canine distemper (CD) is one of the highly contagious and invariably fatal viral diseases of dogs and other carnivores. Despite the widespread use of modified live vaccines to control CD, the prevalence of disease has increased at an alarming rate in recent years. Although a number of factors may be ascribed for vaccine failure, antigenic differences among the vaccine and wild-type strains have gained the interest of researchers. Considering the high genetic variability of haemagglutinin gene (H gene) and its role in eliciting the immune response to canine distemper virus (CDV), we have generated nine full-length CDV H gene sequences from infected dogs including three vaccinated cases. Bayesian analysis was performed using 102 full-length H gene nucleotide sequences over a time frame of 76years (1940-2016) from 18 countries. The time to the most recent common ancestor (tMRCA) of CDV was estimated to be 1696 AD. Phylogenetic reconstruction clustered Indian wild-type viruses into a distinct monophyletic group clearly separated from the previously established CDV lineages. This signifies the presence of a novel genetic variant (proposed as "Lineage India-1/Asia-5") circulating among dog population in India. To investigate the importance of substitutions at amino acid residues 530 and 549 of CDV H protein in determining the host switches from canid to non-canid hosts, we analysed 125 H gene sequences including nine sequences generated in this study. Selection pressure analysis and analysis of amino acid sequences revealed a trend towards adaptation of 549H variants in non-canid hosts although no role of G/E530R/D/N substitution could be identified. This is the first comprehensive study about the nature and ecology of CDV circulating among dog population in India. Outbreaks in vaccinated animals as observed in this study have raised a concern towards the effectiveness of current vaccine strains warranting detailed investigation.

Promising use of Polymerase Chain Reaction Associated to Reverse Transcription for the Detection of the America-1 Lineage of Canine Distemper Virus

Promising use of Polymerase Chain Reaction Associated to Reverse Transcription for the Detection of the America-1 Lineage of Canine Distemper Virus

Phylogenetic analysis of the wild-type strains of canine distemper virus circulating in the United States

BackgroundCanine distemper (CD) is a highly contagious, systemic, viral disease of dogs seen worldwide. Despite intensive vaccination in developed countries, recent reports suggest both the re-emergence and increased activity of Canine distemper virus (CDV) worldwide, including the United States. CDV is an RNA virus of the genus Morbillivirus within the family Paramyxoviridae. Viral genomic RNA encodes six structural proteins. Of the six structural proteins, the hemagglutinin (H) gene has the greatest genetic variation and is therefore a suitable target for molecular epidemiological studies. The majority of neutralizing epitopes are found on the H protein, making this gene also important for evaluation of changes over time that may result in antigenic differences among strains. The aim of this study was to determine the phylogenetic relationship of CDV strains circulating in the US.MethodsFifty-nine positive canine distemper virus samples collected from dogs from different regions and states from 2014 to 2017 were sequenced with a targeted next-generation sequencing (NGS) method. The sequences of the H, F, and P genes and the matrix-fusion (M-F) intergenic region of the amplified CDVs were analyzed individually.ResultsSequence analysis of the H gene revealed that there are at least 3 different lineages of CDV currently circulating in the US. These lineages include America-3 (Edomex), America-4, and a clade that was previously reported in association with an outbreak in Wyoming, which was linked to a domestic dog-breeding facility in Kansas in 2010. These lineages differ from the historically identified lineages in the US, including America-1, which contains the majority of the vaccine strains. Genetic differences may result in significant changes to the neutralizing epitopes that consequently may lead to vaccine failure. Phylogenetic analyses of the nucleotide sequences obtained in this study of the F and P genes and the M-F intergenic region with sequences from the GenBank database produced similar findings to the H gene analysis.ConclusionsThe CDV lineages currently circulating in the US differ from the historically identified lineages America-1. Continuous surveillance is required for monitoring circulating CDV strains in the US, to prevent potential vaccine breakthrough events.

Antigenic analysis of genetic variants of Canine distemper virus

Canine distemper virus (CDV) is an RNA virus of the genus Morbillivirus within the family Paramyxoviridae. CDV produces multi-systemic disease in dogs and other terrestrial carnivores. With the development of modified live vaccines in the 1950s and 1960s, the disease, with a few exceptions, has been successfully controlled. However, recently the cases of CDV in vaccinated dogs have been increasing throughout the world, including the United States. There are many reasons that can lead to vaccine failure, including antigenic differences between the vaccine strains and the currently circulating wild-type strains. Currently, there are at least three genetically different CDV lineages circulating in the US. Therefore, in this study, we evaluated various wild-type CDV and vaccine isolates to determine if the genetic differences observed among various strains result in significant antigenic differences based on changes to the neutralizing epitopes. The results of a cross-neutralization assay revealed that there are antigenic differences among the tested CDV wild-type isolates as well as between the tested isolates and the vaccine strains currently used in the US. Therefore, these results suggest the need to develop an updated CDV vaccine.