It has not yet been rebolved to what extent the boar is involved in the epidemiology of the infection.
The intermittent excretion of PCV-2 in semen has already been proved, but the actual seminal dose required for the infection could not yet be defined. In this study 152 boars of an insemination centre and 90 boars from breeding farms were serologically tested for PCV-2 antibodies via INGEZIM CIRCOVIRUS IgG/IgM ELISA test kit of the Ingenasa company (Madrid, Spain). This test offers the possibility to distinguish between IgG and IgM antibodies, through this allowing the determination of the point of time of infection. Via externe and nested PCR the semen of the boars was screened for PCV-2 nucleic acid. To determine a possible association to the age of the animals the pigs were divided into five groups of age.
Based on the PCV-2 antibody results it was shown that no boar had an acute infection, because no animal had positive IgM titers. The boars of the breeding farms had higher IgG seroprevalences compared to the boars of the insemination centre. The PCR of the semen samples resulted in significantly higher values for the boars of the breeding farms (23.35 % in the externe PCR/25.5 % in the nested PCR) compared to the boars of the insemination centre (11.2 %). Within the younger boars (<= 16 months of age) a high number of animals tended to have positive results. Every boar was only sampled once, therefore it cannot be ruled out that a later sampling time led to a different PCR result.
In conclusion, the present study confirms the high prevalence of PCV-2 not only in boars from breeding farms, but also in boars from insemination centers. PCV-2 could be found in both groups in a remarkable number of samples. Excretors of PCV-2 antigen cannot exclusively be determined serologically. Considering the fact that one single boar is able to produce large amounts of semen weekly, which are used for artificial insemination nationally and internationally, the risk of the spread of this pathogen is obvious.