INVESTIGATIONS ON THE OCCURRENCE OF PORCI NE REPRODUCTIVE AND RESPIRATORY SYNDROME .1. ITS COURSE AND ECONOMIC-EFFECTS

The clinical signs, including reproductive disorders, and the results of serological investigations within a large breeding herd infected wi th PRRS virus are described. Litter size and the percentage of sucklin g and weaned pigs reared were both reduced over a period of some month s. The acute phase of the disease lasted 10-12 weeks followed by a chr onic stage of illness. There was a correlation between the duration of pregnancy, the proportion of pregnant sows, the number of live piglet s per sow and the conception rate with the presence of infection. Acut e infections were also associated with anoestrus and an increased cull ing rate due to infertility. Sows that recovered.from PRRS virus infec tion produced litters of normal size. Serological investigations indic ated that infection persisted for at least 12 months after the initial onset of clinical signs. Financial losses within the breeding herd in 1991 were estimated to be some 442,831 DM.