FACTORS ASSOCIATED WITH INFLUENZA-A VIRUS -INFECTIONS IN FINISHING PIGS

In August of 1989 sera from 2115 finishing pigs out of 214 herds in th e north of Schleswig- Holstein (Germany) were tested for antibodies ag ainst three strains of Influenza A viruses by using die haemagglutinat ion inhibition test. Seroprevalences of A/Swine/Nederland/25/80 (H1N1) , A/Philippines/2/82 (H3N2), and A/Port Chalmers/1/73 (H3N2) on herd l evel were 23.4%, 20.6% and 5.1% respectively. The mean within herd pre valences were 9.69%, 14.7% and 0.6%, respectively. Antibodies against H1N1 and H3N3 strains were simultaneously found in 7.5% of the herds a nd in 1.6% of die pigs. In 485 (22.9%) of the pigs and in 83 (38.3%) o f die herds at least one of the strains was prevalent. In 61 (73.5%) o f those herds there was no evidence of a clinical outbreak before test ing. A higher risk of infection with influenza virus was associated wi th high pig density (greater-than-or-equal-to 200 pigs per km2) and wi th management factors as greater herd size (> 300 finishing pigs), sla tted floors (compared to straw bedding) and all in-all out system (com pared to continuous purchase).