Genetic diversity of canine parvovirus variants circulating in Nigeria.

Canine parvovirus (CPV) is a fast-evolving single-stranded DNA virus that causes severe and fatal gastrointestinal disease in dogs. Lately, several mutations affecting viral protein (VP) capsid resulting in highly pathogenic variants with distinctive immunological and clinicopathological characteristics abound. This study involved screening stools of 44 randomly selected clinical cases of canine gastroenteritis from 4 cities (Ibadan, Jos, Makurdi, and Zaria) in Nigeria for CPV antigen using an on-the-spot immunoassay test kit, as well as, molecular detection of viral nucleic acid by polymerase chain reaction. Subsequently, nucleic acid sequencing of 1195-bp amplicons encompassing the VP2 encoding region was done. The resultant 40 high-quality amino acid sequences obtained were analysed for the identification and grouping of the viruses into their discrete variants - CPV-2a, CPV-2b, or CPV-2c, using key amino acids substitutions - Asn, Asp, or Glu respectively at position 426 of the VP2 gene. One-third (11/40; 27.5%) of the analysed sequences were identified as CPV-2a and two-third (29/40; 72.5%) as CPV-2c. The original CPV and CPV-2b were not detected. Also, the "new CPV-2a variant" with mutation S297A identified had two additional mutations (Y324I and T440A) associated with selective pressure and vaccination failure in their sequences. Similarly, unique CPV-2c mutants carrying genetic markers (S297A, Y324I, and Q370R) that are highly related to CPVs of Asian origin were observed. These findings revealed a high level of divergence of existing CPVs in circulation; suggesting that CPV is rapidly evolving in Nigeria lately.