Veterinary session

Canine distemper virus (CDV) is frequently detected pathogen worldwide. Previously, CDV infection was considered as a disease specific to Carnivores, but todays CDV caused disease has been found in many different species (Ailuridae, Mustelidae, Viverridae, Procyonidae, Phocidae, Felidae), including non-human primates (Macaca fuscata, Macaca mulatta). CDV is a highly contagious pathogen that often causes fatal, systemic disease. There is no effective specific treatment for the disease, the symptomatic therapy is the only option, which is highly expensive and there are doubts about its efficiency. The CDV caused diseases could be prevented by vaccination, and many different vaccines are available in Hungary. In recent years, increasing number of CDV caused clinical signs and deaths were observed in young and adult, vaccinated and unvaccinated dogs.

In order to survey the virus strains causing the current diseases, samples were collected from affected animals, and examined with molecular biological methods. Based on phylogenetic examinations, CDVs are generally divided into seven clusters (America 1 and 2, Asia 1 and 2, Arctic, Europe and European wildlife).

Our results indicate that the viruses causing diseases in Hungary belongs to the Arctic group, and they have very close relationship to each other. Based on the phylogenetic analysis, the currently spreading CDVs may originate from a virus detected in 2006 in Hungary. Although, according to the analysis of Hemagglutinin protein, the CDVs belonging to Arctic cluster shows the higher similarity to America 1 group containing most of vaccine strains, the differences on the amino acid level could be sufficient enough so that the detected CDVs in this study can results sever clinical signs and deaths even repeatedly vaccinated animals, too. Regular vaccinations means selective pressure on the virus, resulting changes in antigen structure of the virus, thus the efficiency of the vaccine decreases over time.

The CDV caused fatal epidemics more times in primates, and even human cell cultures could be successfully infected with the virus. Therefore there might be a risk that the virus will adopt to humans, which could have very serious consequences. Hence why we think it is important to develop a vaccine that could keep up with the evolution of the virus, and to use these vaccines in order to minimize the risk of the virus spreading to the human population.