Karla Gonçalves

Typing of canine parvovirus strains circulating in Brazil between 2008 and 2010.

Abstract Detection and characterisation of the canine parvovirus (CPV-2) strains that are currently circulating are essential for the understanding of viral evolution and the development of measures to control its spread. In the present study, stool samples from 144 dogs were analysed by polymerase chain reaction (PCR) for CPV-2, and 29.2% (42/144) of them were positive. From the 42 positive strains, 71.4% (30) of the dogs had signs of haemorrhagic gastroenteritis. The sequencing of the 583bp fragment of the VP2 gene from the positive strains identified 78.6% (33/42) of them as type 2c, 19% (8/42) as type 2b and 2.4% (1/42) as type 2a. A phylogenetic analysis of the variants circulating in the canine population of Brazil showed that they are very similar to those found in other countries and type 2c has become the predominant type circulating in Brazil.

High rate of viral evolution in the capsid protein of porcine parvovirus

In recent years, it has been shown that some parvoviruses exhibit high substitution rates, close to those of RNA viruses. In order to monitor and determine new mutations in porcine parvovirus (PPV), recent PPV field isolates from Austria, Brazil, Germany and Switzerland were sequenced and analysed. These samples, together with sequences retrieved from GenBank, were included in three datasets, consisting of the complete NS1 and VP1 genes and a partial VP1 gene. For each dataset, the nucleotide substitution rate and the molecular clock were determined. Analysis of the PPV field isolates revealed that a recently described amino acid substitution, S436T, appeared to be common in the VP2 protein in the Austrian, Brazilian and German virus populations. Furthermore, new amino acid substitutions were identified, located mainly in the viral capsid loops. By inferring the evolutionary dynamics of the PPV sequences, nucleotide substitution rates of approximately 10(-5) substitutions per site per year for the non-structural protein gene and 10(-4) substitutions per site per year for the capsid protein gene (for both viral protein datasets) were found. The latter rate is similar to those commonly found in RNA viruses. An association of the phylogenetic tree with the molecular clock analysis revealed that the mutations on which the divergence for both capsid proteins was based occurred in the past 30 years. Based on these findings, it was concluded that PPV variants are continuously evolving and that vaccines, which are based mainly on strains isolated about 30 years ago, should perhaps be updated.

First detection of canine parvovirus type 2c in Brazil

The presence of canine parvovirus type 2 (CPV-2), 2a and 2b has been described in Brazil, however, the type 2c had not been reported until now. In the current study, seven out of nine samples from dogs with diarrhea were characterized as CPV-2c, indicating that this virus is already circulating in the Brazilian canine population.