Cessation of porcine reproductive and respiratory syndrome (PRRS) virus spread in a commercial swine herd
Wayne R. Freese, DVM and HanSoo Joo, DVM, PhD
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We report a case of porcine reproductive and respiratory syndrome (PRRS) virus infection that appeared to spontaneously stop spreading. We compared serologic profiles of this 250-sow farm (herd A) with those of another 300-sow farm (herd B), both with a previous history of PRRS. In November 1992, we collected serum samples from pigs of different age groups (from I week to 3 years old) from both herds. We tested PRRS virus antibody titers by an indirect-fluorescent antibody (IFA) method. IFA titers of >1:16 were detected in 20 of 129 pigs (15.5%) from herd A and 73 of 158 pigs (46.2%) from herd B. In April 1993, none of 30 pigs between 4-26 weeks of age from herd A were seropositive, while all 60 pigs of the same age group from herd B were seropositive. A group of IS gilts in herd A, introduced in January 1992 from a form showing no clinical signs of PRRS, remained seronegative. No PRRS virus was isolated in April 1993 from 30 serum samples from pigs 5-10 weeks old in herd A, while virus was isolated from 4 of 28 sera from pigs of a similar age in herd B. PRRS virus stopped spreading in herd A, while the infection is still endemic in herd B.
Cite as: Freese WR, Joo HS. Cessation of porcine reproductive and respiratory syndrome (PRRS) virus spread in a commercial swine herd. J Swine Health Prod 1994;2(1):13-15.
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