Molecular detection and clinical aspects of porcine circovirus 3 infection in pigs from Brazil / [Detecção molecular e aspectos clínicos da infecção por circovírus suíno 3 em suínos do Brasil]

Porcine circovirus 3 (PCV-3) DNA has been detected in serum samples from apparently healthy pigs as well as pigs with different clinical conditions. Molecular detection of PCV-3 was observed in swine serum samples from Southeastern - Brazil using a nested PCR designed specifically for this study. The epidemiology and clinical aspects of PCV-3 infection were evaluated. The samples originated from 154 pigs of both genders from different production phases and with different clinical presentations, sampled from 31 pig farms visited between 2013 and 2018. In this study, PCV-3 was detected in 26.7% of samples from all populations across varying ages. Statistical association (P=0.0285) was observed only between animals with respiratory signs and PCV-3; no PCV-3-positive animal had diarrhea. No statistical association was observed between PCV-3 and age, or gender of the pigs. Because PCV-3 is a newly discovered virus, there is very little information about its epidemiology. We hope that these data can help in future studies investigating PCV-3 epidemiology.(AU)

O DNA do circovírus suíno 3 (PCV-3) foi detectado em amostras de soro de suínos aparentemente saudáveis, bem como em suínos com diferentes condições clínicas. A detecção molecular do PCV-3 foi observada em amostras de soro de suínos da região Sudeste do Brasil, com uma nested PCR desenhada especificamente para este estudo. A epidemiologia e os aspectos clínicos da infecção por PCV-3 foram avaliados. As amostras foram coletadas de 154 suínos de ambos os sexos, de diferentes fases de produção e com diferentes sinais clínicos. Os animais pertenciam a 31 granjas visitadas entre 2013 e 2018. Neste estudo, o PCV-3 foi detectado em 26,7% das amostras de animais saudáveis e de animais com variados sinais clínicos, de ambos os sexos e de idades variadas. Associação estatística (P=0,0285) foi observada apenas entre animais com sinais respiratórios e PCV-3; nenhum animal positivo para PCV-3 apresentava diarreia. Não foi observada associação estatística entre o PCV-3 e a idade ou o sexo dos suínos. Por se tratar de um vírus recém-descoberto, existem poucas informações sobre sua epidemiologia. Espera-se que os dados deste trabalho possam contribuir para futuros estudos sobre a epidemiologia do PCV-3.(AU)

Retrospective study of porcine circovirus 3 (PCV3) in swine tissue from Brazil (1967-2018).

In this study, we report the molecular diagnosis and retrospective study of porcine circovirus 3 (PCV3) in frozen and formalin-fixed paraffin-embedded swine tissues (FFPE) collected from 1967 to 2018 in southeastern Brazil (Espírito Santo and Rio de Janeiro states). Frozen tissues from 35 pigs and FFPE tissues from 143 pigs were tested by nested PCR, targeting the PCV3 partial capsid gene. Bidirectional sequencing of 16 positive samples was performed, followed by sequence analysis and haplotype networks. A total of 26/178 samples (14.6%) tested positive for PCV3: 14/35 (40%) frozen tissue and 12/143 (8.4%) FFPE tissue. PCV3 was detected in the 1960s, 1970s, 2000s, and 2010s with the characterization of types PCV3a and PCV3b. A star-like distribution was observed in the grid of haplotypes, with a low haplotype diversity and more recent dispersal of the virus. A total of 40% of asymptomatic animals considered fit for slaughter tested positive for PCV3. In conclusion, PCV3 DNA was detected over 51 years of study, prior to initial reports and, so far, the sample detected in 1967 is the oldest partial capsid sequence described. The circulation of two different genotypes was reported, suggesting more than one introduction event of this virus into Brazil. Moreover, taken together, our studies indicated an ancient origin of PCV3 and its circulation in asymptomatic animals in Brazilian herds.