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第25号公告板 - Summer 2006
VirologyPorcine Reproductive and Respiratory Syndrome (PRRS)
PRIETO C, CASTRO JM
Porcine reproductive and respiratory syndrome virus infection in the boar: a review.
Theriogenology, 2005, Volume 63, N°1, 1-16
This paper, focused on the effects of PRRSV infection in boars, is built up on a series of targeted questions and answers that review the various epidemiological and clinical consequences of the presence of the virus in the reproductive tract of boars. One of the characteristics of PRRSV infection in boars is that it induces only limited or even no clinical signs (transient fever, depression and anorexia), which makes it rather tricky to identify potential infected animals. In most cases, the quality of semen results altered by PRRSV infection, but the type of alterations may vary. The more reliable methods for the detection of PRRSV in semen are virus isolation and swine bioassay. The technique of RT-PCR allows the detection of even lower amounts of viral genome but does not distinguish infectious virus from a portion of viral genome and thus can lead to false positive results, especially during the chronic phase of the disease. Difficult to determine is the actual absence of PRRSV from semen since shedding is intermittent and not correlated to serological status. Regarding venereal transmission of PRRSV, it is likely to require a relatively high amount of virus and the risk of transmission clearly increases with the number of females inseminated with the same contaminated semen. Attempts to control venereal transmission of PRRSV showed that modified-live vaccines allowed to reduce or eliminate shedding of wild-type virus. However, the semen of vaccinated boars can subsequently transmit the vaccine virus.
