Circulation of Porcine Parvovirus Types 1 through 6 in Serum Samples Obtained from Six Commercial Polish Pig Farms

Porcine parvoviruses are small non-enveloped DNA viruses, very resistant to inactivation, and ubiquitous in the global pig population. Porcine parvovirus type 1 (PPV1) has been known since the 1960s and is a major causative agent of reproductive failure in breeding herds. During the last decade, several new parvoviruses have been identified in pigs by molecular methods and have been consecutively designated as PPV2 through PPV6. Epidemiology data for these viruses are limited, and the impact of these newly recognized parvoviruses on pigs is largely unknown. To further generate knowledge on the distribution of PPVs in pigs, a total of 247 serum samples were collected from six commercial Polish pig farms during 2013-2015 and tested by PCR assays and ELISAs. The pigs ranged from two to 18 weeks of age at sample collection. Breeding herds supplying the investigated farms were routinely vaccinated against PPV1. While all growing pig samples were negative for PPV1 DNA, young pigs were frequently negative for PPV1 antibodies and seroconversion to PPV1 was commonly seen at 9-10 weeks of age. The PPV2 antibody detection was highest in young pigs (2-6-week-old) and decreased in older pigs indicating passively acquired antibodies. The DNA prevalence rates in the serum samples analysed were 19% for PPV2, 7.7% for PPV3, 2.4% for PPV4, 4.0% for PPV5 and 6.1% for PPV6. Most PPV DNA-positive samples were identified in 9- to 18-week-old pigs with no obvious association with disease on the farm. All recently emerging PPV genotypes were detected in Polish farms. Similar to previous reports in other pig populations, PPV2 was the most frequent PPV genotype circulating in Poland.