EFFECT OF SEQUENTIAL PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME AND SWINE INFLUENZA ON THE GROWTH AND PERFORMANCE OF FINISHING PIGS

Sows and gilts on a breeding and finishing unit seroconverted to porci ne reproductive and respiratory syndrome (PRRS) virus between February and March 1992. The signs of the disease progressed through the breed ing herd to the piglets, weaners, growers and finally the finishing pi gs. Forty-eight finishing pigs, on a nutritional experiment in which t he individual pigs' food intake was recorded daily, showed signs of PR RS and later of swine influenza virus infection. Blood samples collect ed at slaughter from 47 of the pigs were seropositive to PRRS virus hu t seronegative to swine influenza virus. However, an immunocytochemica l examination of a representative sample of the lungs of the pigs show ed that swine influenza virus was present, despite the negative serolo gical results. The infection of the finishing pigs with PRRS virus was associated with recurrent periods of inappetence and a decline in gro wth rate and performance. The total financial loss from the sequential infection with the two viruses, in a herd without high health status, was estimated at approximately pound 7 per pig.