Detection of PCV3 in various sample types from wild boars in Poland

Background
In 2016, the new circovirus, PCV3, was discovered in pigs displaying various clinical symptoms. To date, this virus is believed to be pathogenic for pigs and considered equal or greater economic significance for the porcine sector compared to PCV2. Besides pigs, other species, including wild boars, have been identified as susceptible to PCV3 infection. Infection in wild boars is not linked with any clinical outcome. However, the data regarding the detailed pathogenesis of PCV3 infection in wild boars contain some knowledge gaps. Available data indicate that PCV3 is highly prevalent in wild boars, and this species can represent a potential reservoir of the virus for pigs. Therefore, this research aimed to assess the prevalence of PCV3 in different samples collected from wild boars.
Results
154 of 285 (54%) sampled wild boars tested positive for PCV3 DNA presence. There were no statistically significant differences between the proportion of positive individuals culled in different regions of the country. PCV3 genetic material was detected in every tested sample type, and the sample type significantly influenced the detection rate (p < 0.05), with the highest and lowest detection rates in liver (47.02%) and feces (2.5%). No statistically significant differences (p > 0.05) were found in the detection rate of different organs between animals of various age categories. The highest viral load expressed as Ct value was determined in the liver, however, it was not significantly different from that noted for serum (p > 0.05). The obtained genome sequences were similar to those previously determined for animals infected in Poland.
Conclusions
PCV3 is highly prevalent in the Polish wild boar population and circulates among animals of different ages. Due to the viral prevalence and the quantity in the liver, this organ can represent the target site for replication and one of the most suitable samples for PCV3 detection in wild boars.