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TDK conference 2013

Genetic analysis of canine parvovirus type 2
Varga Szilvia - year 6
SzIU, Faculty of Veterinary Science, Department of Microbiology and Infectious Diseases
Supervisor: Dr. Cságola Attila


Canine parvovirus type 2 (CPV-2) infections is one of the most frequent causes of death in young susceptible dog populations worldwide. CPV-2 is responsible for haemorrhagic enteritis, fever and high mortality, mainly in young dogs. Since its emergence in 1978, the original CPV-2 was replaced by its distinct genetic variants designated today as types CPV-2a, CPV-2b, CPV-2c, New CPV-2a and New CPV-2b. Numerous vaccines were developed for immunisation, but in recent years a number of vaccinated animals developed CPV-2 induced disease or even died, and the virus was isolated from pups and also from adults showing typical symptoms.

During this study 42 out of 50 examined faecal samples, originated from dogs showing digestive tract symptoms, were proved to be positive. The samples originated from different parts of the country. Nucleic acid and predicted amino acid sequences of the gene encoding VP2 capsid protein were determined and analysed of 25 positive samples. These sequences were compared to the original virus and the vaccine strains available in GenBank. Most of the studied samples were detected as the New CPV-2a type, but we found two sequences which could evolve presumably through the recombination of a CPV-2a and a vaccine virus. The Hungarian CPV-2 sequences include several mutations which either were already described in international letters or were newly detected by us. These mutations affect the fine structure of the virus influencing the access of CPV-2 to the host cell, the immunogenicity and the binding of antibodies responsible for neutralization. For the first time in Europe, substitution of amino acid in position 324 of the VP2 capsid protein was successfully detected in the strains studied by us, together with the detection of a so far Hungarian specific mutation affecting residue 516.

Concerning the observed amino acids that influence immunogenicity, the CPV-2 sequences found in the samples in our country substantially differ from the original CPV-2 and from the vaccine strains widely used in Hungary. The phylogenetic tree confirmed the close relationship or the genetic distance among the Hungarian viruses and the reference and vaccine strains as well. Since the vaccines contain the original type 2 CPV, which is no longer present in the field, a number of international studies are focusing on the efficacy of such vaccines. The genetic analysis of the virus may help the development of even more effective vaccines and the control of the ongoing epidemiological situation.

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