A recent distemper virus outbreak in the growing canine populations of Galapagos Islands: a persistent threat for the endangered Galapagos Sea Lion

Canine Distemper Virus (CDV) is a highly contagious virus that can cross mammalian species barriers and has widespread impacts on both domestic animals and wildlife populations. This study describes a recent outbreak of CDV in the Galapagos Islands in 2019. A total number of 125 dogs with clinical signs compatible with CDV were included in this study. Nasal swabs were taken and analyzed by RT-qPCR for the detection of CDV, resulting in a positivity rate of 74.4% (IC95%, 66-81%). Among the CDV positive dogs, 82.2% presented with respiratory signs, 48.8% neurological signs, and 28.9% gastrointestinal signs. CDV has been previously reported in the domestic canine population of the Galapagos Islands in 2001 and 2004. The current study shows how CDV is still a threat for the endemic and endangered Galapagos sea lion, despite recent policies for dog population control and CDV vaccination.

Investigation of TLR1-9 genes and miR-155 expression in dogs infected with canine distemper

This study aimed to determine the relationship of toll-like receptor (TLR) 1-9 genes and microRNA (miR) -155 expression levels with hematologic parameters in dogs diagnosed with canine distemper. In the study, two groups were used pre-treatment and post-treatment. Infected dogs were diagnosed with canine distemper with the help of a rapid test kit and Real Time-Polymerase Chain Reaction (RT-PCR). Based on the correlation coefficients between the expression levels of the genes examined within the scope of the study and hematologic values, a positive correlation was found between the TLR2 gene and the monocyte (MON) value and between the TLR4 gene and the platelet (PLT) value in the pre-treatment group. A strong positive correlation was identified between TLR3 and TLR9 genes and erythrocyte (RBC) and hemoglobin (HGB) values; between TLR5 gene and RBC, HGB and hematocrit (HCT) values and between TLR9 gene and RBC and HGB values in the post-treatment group, on the other hand, a positive correlation was found between TLR1 gene and MON and neutrophil (GRAN) values; between TLR3 gene and HCT value and between TLR9 gene and MON and HCT values. The study concluded that miR-155 and TLR8 gene were upregulated at a statistically significant level (P < 0.05) Post-treatment in dogs infected with canine distemper and there was a positive correlation between the upregulation of miR-155 and the upregulation of TLR8 in the same period. This result suggests that the upregulated miR-155 expression post-treatment increased TLR8 gene expression. In the light of these findings, it miR-155 may have the potential to be used in clinical practice in the treatment or prognosis of dogs infected with canine distemper.

Canine distemper in neotropical procyonids: Molecular evidence, humoral immune response and epidemiology

Canine Distemper Virus (CDV) can produce a fatal multisystem disease in carnivores and other mammals and is an important threat for wildlife conservation. However, integrative and comparative studies in wild carnivores are scarce and some areas of the world lack of genetic studies. We explore the dynamic of host-CDV in a procyonid community during an outbreak. This study reports for the first time an index case occurred in a common raccoon (Procyon lotor) and for which a complete CDV diagnosis was performed. The long-term epidemiological analysis in two sympatric populations of common raccoons and white-nosed coatis (Nasua narica) was achieved through seroneutralization, RT-PCR and direct immunofluorescence assays. Additionally, hematologic analyses were performed and phylogenetic reconstruction of CDV was done using molecular data from this study. Overall prevalence for white-nosed coatis was 19.6 % and for common raccoons was 25.3 % by seroneutralization, and 13.3 % and 17.3 % by RT-PCR. Antibodies titer average for white-nosed coatis was 1:512 and 1:156 for common raccoons. Significant difference in prevalence between white-nosed coatis and common raccoons was detected during one season (summer 2013). White-nosed coatis showed differences in erythrocytes and monocytes counts between positives and negative animals. A 100 % similarity was found between CDV of white-nosed coati and CDV of common raccoon and is a new CDV sequence not previously described; this sequence is close to Asian and European lineage. An endemic state of distemper in both species was observed but showed different dynamics over time per host species. Differences in cellular and humoral responses were also detected between procyonids. The evidence found here may have serious implications for CDV understanding in wild carnivores, it reveals clear differences in the response over time to the same CDV strain, in two close related carnivore species.

Evaluation of a Direct Immunofluorescent Assay and/or Conjunctival Cytology for Detection of Canine Distemper Virus Antigen

Canine distemper is a common and potentially lethal multisystemic disease caused by the Canine distemper virus (CDV). We evaluated the diagnostic performance of direct immunofluorescent assay (FA) and cytology to detect CDV antigen in conjunctival cells compared with an established polymerase chain reaction (PCR) detection assay used as a gold standard for CDV diagnosis. Samples were collected from 57 young dogs presenting with central nervous system signs compatible with distemper disease. Exfoliative epithelial cells were collected from the right and left conjunctiva of each animal using nylon-bristled cytobrushes for cytology and cotton swabs for FA and PCR. For the direct FA, samples were stained with anti-CDV polyclonal antiserum conjugated to fluorescein isothiocyanate and imaged using a fluorescent microscope. Out of 57 dogs tested, 19 were PCR positive (15 positive in direct FA and 4 positive in cytology, including one that was negative by PCR), whereas 37 dogs were negative in all methods. A good agreement was observed between the FA and PCR, with a κ-value of 0.833 (95% CI: 0.678-0.989). Meanwhile, there was poor agreement between cytology and PCR (κ-value of 0.164; 95% CI: -0.045 to 0.373) and a fair agreement between FA and cytology (κ-value of 0.231; 95% CI: -0.026 to 0.487). Our results indicated a poor performance of cytology for the detection of CDV antigen. In contrast, FA is a 100% specific and an adequately sensitive assay (sensitivity: 78.95%, negative likelihood ratio: 0.21, 95% CI: 0.09-0.50) for antemortem diagnosis of canine distemper.

RT-PCR and sequence analysis of the full-length fusion protein of Canine Distemper Virus from domestic dogs

During 2007-2014, 84 out of 236 (35.6%) samples from domestic dogs submitted to our laboratory for diagnostic purposes were positive for Canine Distemper Virus (CDV), as analyzed by RT-PCR amplification of a fragment of the nucleoprotein gene. Fifty-nine of them (70.2%) were from dogs that had been vaccinated against CDV. The full-length gene encoding the Fusion (F) protein of fifteen isolates was sequenced and compared with that of those of other CDVs, including wild-type and vaccine strains. Phylogenetic analysis using the F gene full-length sequences grouped all the Argentinean CDV strains in the SA2 clade. Sequence identity with the Onderstepoort vaccine strain was 89.0-90.6%, and the highest divergence was found in the 135 amino acids corresponding to the F protein signal-peptide, Fsp (64.4-66.7% identity). In contrast, this region was highly conserved among the local strains (94.1-100% identity). One extra putative N-glycosylation site was identified in the F gene of CDV Argentinean strains with respect to the vaccine strain. The present report is the first to analyze full-length F protein sequences of CDV strains circulating in Argentina, and contributes to the knowledge of molecular epidemiology of CDV, which may help in understanding future disease outbreaks.