INDIRECT FLUORESCENT IGM ANTIBODY-RESPONSE OF PIGS INFECTED WITH PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME SYNDROME VIRUS

IgG and IgM antibody responses were examined by an indirect fluorescen t antibody method in pigs following inoculation with different porcine reproductive and respiratory syndrome virus (PRRSV) isolates or a vac cine virus. Viremia was also examined in the pigs. The IgG antibody wa s first detected between 9 and 14 days post inoculation (PI) and maint ained high titers for at least 7 weeks PI. No change in IgG antibody t iters was observed when the pigs were reinoculated with PRRSV 35 days PI. IgM antibody was detected between 5 and 28 days PI in the pigs. Re inoculation at 35 days PI caused a short term rise of IgM antibody. Vi rus was isolated from sera collected between 2 and 21 days PI. The IgM antibody was detected regularly in sera collected during viremia and up to 1-2 weeks after the viremic periods. These results suggest that pigs with detectable IgM antibody are probably pigs with recent infect ion and that routine testing of IgM antibody in purchased breeding pig s from seropositive farms may be useful in identification of pigs with recent infection. (C) 1997 Elsevier Science B.V.