Analysis of survey data about the effect of vaccination of sows against blue pig abortion (PRRS) in the Netherlands

: Questionnaires were used to collect information on the experience of pig breeders with the vaccination of sows against PRRS. There was a 1-year interval between the two questionnaires. Sixty-two pig breeders returned the first questionnaire and 36 returned the second questionnaire. Before they started vaccination, 61% of the pig breeders sent samples to the laboratory of the Animal Health Service for investigation. At least one blood sample was positive for PRRS antibodies, but PRRS virus was not detected in any of the samples. Repeat breeding was the most important reason to vaccinate sows. On 54 farms (77%) sows were first vaccinated during the suckling period, on one farm (2%) sows were vaccinated during gestation, and on 7 farms (11%) all sows were vaccinated irrespective of their phase of reproduction. Repeat vaccinations were given during the suckling period on all farms. Mild side effects were reported on 16 farms (25%). Repeat breeding was the most important adverse reaction, followed by anoestrus. After 1 year, 58% of the pig breeders expressed satisfaction with vaccination. Twenty-eight pig breeders stopped vaccinating their sows in the first year, mainly because vaccination had no effect on the technical results. The effect of PRRS on the technical results of eight farms before and a year after vaccination was analysed. Although technical results were slightly better after vaccination, it was not clear whether this improvement was due to vaccination. From the results of this study it can be concluded that, without good diagnostic investigations, the routine vaccination of sows against PRRS is not economically viable in herds infected with PRRS virus.