Detection Of Canine Parvovirus Type 2 And Analysis Of VP2 Gene Sequence In Three Areas Of Heilongjiang Province From 2014 To 2015

Canine parvovirus(CPV) is a major pathogen of diarrhea in dogs and a small,non-enveloped virus, containing a single-stranded DNA, belonging to the genus Parvovirus within the family Parvoviridae. CPV is responsible for acute gastroenteritis and leucopenia in puppies, which emerged in 1978 and spreaded all over the world. Since then, this disease becomes endemic worldwide. As an acute infective sickness, its morbidity and mortality are very high respectively, and it is one of the most important disease in pets, army dogs, patrol dogs,which has caused serious economic losses.To trace evolution of canine parvovirus-2(CPV-2), a total of 201 stool samples were collected from dogs with diarrhea in Heilongjiang province of northeast China from May 2014 to April 2015. The presence of CPV-2 in the samples was determined by PCR amplification of the VP2 gene(568 bp) of CPV-2. The results revealed that 95 samples(47.26%) were positive for CPV-2, and they showed 98.8% ~ 100% nucleotide identity and 97.6% ~ 100% amino acid identity. Of 95 CPV-2-positive samples, types new2a(Ser297Ala), new2b(Ser297Ala), and 2c accounted for 64.21%, 21.05%, and 14.74%, respectively. The positive rate of CPV-2 and the distribution of the new2 a, new2 b and 2c types exhibited differences among regions, seasons, and ages. Immunized dogs accounted for 48.42% of 95 CPV-2-positive samples. Confections with canine coronavirus, canine kobuvirus, and canine bocavirus were identified. Phylogenetic analysis revealed that the identified new2 a, new2 b, and CPV-2c strains in our study exhibited a close relationship with most of the CPV-2 strains from China; type new2 a strains exhibited high variability, forming three subgroups; type new2 b and CPV-2c strains formed one group with reference strains from China. Of 95 CPV-2 strains, Tyr324 Ile and Thr440 Ala substitutions accounted for 100% and 64.21%, respectively; all type new2 b strains exhibited the Thr440 Ala substitution, while the unique Gln370 Arg substitution was found in all type 2c strains. Our data revealed that the co-circulation of new CPV-2a, new CPV-2b, and rare CPV-2c, as well as new CPV-2a and new CPV-2b were the main epidemic strains in the three regions of Heilongjiang province.