Elimination of PRRS Using An Inactivated Vaccine in Combination With A Roll-Over Method in A Hungarian Large-Scale Pig Herd

Background:Four countries are free from the porcine reproductive and respiratory syndrome virus (PRRSV) in Europe, a virus that causes severe economic losses worldwide. A number of countries have initiated eradication programmes against the disease. Among the applied methods, complete depopulation-repopulation is the safest and fastest but at the same time the most expensive process. Another possible way of heard eradication is to replace the infected breading stock by gilts reared PRRSV free on the infected farm. This way maintaining continued farm production. In this paper, the authors present a successful complex method of eradication (including the application of an inactivated vaccine and segregated rearing of offspring) in a Hungarian large scale pig farm. Case presentation:A farm of 1475 sows (Farm A) was infected with PRRSV and the clinical signs of reproductive failure were eliminated by using an inactivated vaccine (Progressis®, Ceva). At the beginning of eradication, gilts selected for breeding were vaccinated at 60 and 90–100 days of age, respectively. The subsequent vaccinations of breeding animals were applied at 6 months of age, on the 60–70th day of pregnancy and at weaning. The 7weeks-old piglets of the vaccinated sows, approximately 1200 piglets were transported in groups of 300 animals to a closed, empty farm (Farm B) after a testing negative with PCR, and they were reared here until 14 weeks of age. These seronegative gilts were subsequently transported to a third, closed, empty farm (Farm C), and (having reached the breeding age) they were inseminated here after a negative serological test (ELISA). At the same time, Farm A was depopulated, cleaned and disinfected. All pregnant gilts were transported from Farm C to Farm A after being tested negative with ELISA, where follow-up was performed after farrowing by two serological tests with an interval of six months. Based on the subsequent negative test results, the competent authority declared the herd PRRSV free. Conclusions:The farm presented in this study was the first in the course of the National PRRS Eradication Programme to eradicate PRRSV successfully by vaccinating the sows with an inactivated vaccine and performing segregated rearing of the offspring. Production was almost continuous during the whole process of the population replacement. Testing for monitoring purposes was also cheaper and simpler because of the use of an inactivated vaccine.