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Serological monitoring of porcine reproductive and respiratory syndrome (PRRS) virus on pig farms in Croatia

During 1995 on several pig producing farms in Croatia reproductive and respiratory disturbances were recognized. The phenomenon was studied epizootiologically, clinically, pathomorpfologically, virusologically, bacteriologically and serologically. Based on a characteristic epizootiological situation, specific clinical and pathomorphological findings, as well as positive serological tests, the diagnosis of porcine reproductive and respiratory syndrome (PRRS) was established. In 1997 systematic seroepidemiological monitoring on 10 different breeding farms in Croatia were performed. On a few farms where epidemic form of PRRS turn over chronic endemic form as well as farms without any clinical symptoms the serological monitoring was carried on. The purpose of the present study was to determinate the seroprevalence of antibodies against PRRS virus in different categories of swine on different breeding farms ranging from 500 to 4000 sows. The results presented in this study are encompasing 1000 serological tests of different pig categories from 10 different farms. The blood samples of reproductively active animals were collected from boars and both saws and gilts. The females were sampled for first time before insemination, than 60th day of gestation and during the first week after farrowing. In fattening pigs blood sera were taken from 55 day old nursery pigs, 80 and 150 day old fattening swine. The serological tests were performed at the Department of Virology of the Central Veterinary Institute of Croatia, by mean of enzyme-linked immunosorbent assay (ELISA) using commercial kits IDEXX HerdCheck. The results revealed that 7 out of 10 studied farms were seropositive for presence of PRRS virus, while only 3 of tham remained seronegative. A total number of positive animals on different farms were between 59 % to 95 % respectively (averaging 78,6 %). On the farms were sows, gilts and boars were positive the fattening pigs were also always significantly positive. On all 7 examined farms were seropositive: 74,3 % nongravid sows; 75,7 % 60th days of gestation sows; 70 % sows after farrowing; 97,1 % nongravid gilts; 78,6 % gilts in 60th days of gestation; 78,6 % gilts after farrowing; 72,9 % of boars; 90 % of 55 day old nursery pigs; 81,4 % of 80 and 81,4 % of 150 day old fattening pigs. Based on extensive number of individual animals from largest pig producing farms in Croatia and very high seroprevalence it is concluded that PRRS is largely distributed all ower the country. An interesting observation from epizootiologic prospective is that on 3 of seronegative farms the reproductive animals were not imported, while all 7 seropozitive farms intriduced animals and semen were imported from European country.

reproductive and respiratory syndrome; pig; serology; Croatia

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