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  • Author or Editor: Jeffrey J. Zimmerman x
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Objective—To document shedding of porcine reproductive and respiratory syndrome (PRRS) virus in mammary gland secretions of experimentally inoculated sows, to evaluate effects of vaccination during gestation on virus shedding during the subsequent lactation, and to evaluate shedding of PRRS virus in milk of sows in commercial herds.

Animals—6 sows seronegative for PRRS virus were used for experiment 1, and 2 sows were retained for experiment 2. For experiment 3, 202 sows in commercial herds were used.

Procedure—In experiment 1, 2 sows were inoculated with PRRS virus, 2 sows were vaccinated with modified- live PRRS virus vaccine, and 2 sows served as control pigs. Mammary gland secretions were assayed for PRRS virus. In experiment 2, pregnant vaccinated sows from experiment 1 were vaccinated with another modified-live PRRS virus vaccine. Mammary gland secretions were assayed in the same manner as for experiment 1. For experiment 3, milk collected from 202 sows in commercial herds was assayed for PRRS virus.

Results—In experiment 1, PRRS virus was detected in mammary gland secretions of both vaccinated and 1 of 2 virus-inoculated sows. In experiment 2, virus was not detected in samples from either vaccinated sow. In experiment 3, all samples yielded negative results.

Conclusions and Clinical Relevance—Naïve sows inoculated late in gestation shed PRRS virus in mammary secretions. Previous vaccination appeared to prevent shedding during the subsequent lactation. Results for samples obtained from sows in commercial herds suggested that virus shedding in mammary gland secretions of such sows is uncommon. (Am J Vet Res 2001;62:1876–1880)

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in American Journal of Veterinary Research


Objective—To estimate the annual cost of infections attributable to porcine reproductive and respiratory syndrome (PRRS) virus to US swine producers.

Design—Economic analysis.

Sample Population—Data on the health and productivity of PRRS-affected and PRRS-unaffected breeding herds and growing-pig populations were collected from a convenience sample of swine farms in the midwestern United States.

Procedure—Health and productivity variables of PRRS-affected and PRRS-unaffected swine farms were analyzed to estimate the impact of PRRS on specific farms. National estimates of PRRS incidence were then used to determine the annual economic impact of PRRS on US swine producers.

Results—PRRS affected breeding herds and growing-pig populations as measured by a decrease in reproductive health, an increase in deaths, and reductions in the rate and efficiency of growth. Total annual economic impact of these effects on US swine producers was estimated at $66.75 million in breeding herds and $493.57 million in growing-pig populations.

Conclusions and Clinical Relevance—PRRS imposes a substantial financial burden on US swine producers and causes approximately $560.32 million in losses each year. By comparison, prior to eradication, annual losses attributable to classical swine fever (hog cholera) and pseudorabies were estimated at $364.09 million and $36.27 million, respectively (adjusted on the basis of year 2004 dollars). Current PRRS control strategies are not predictably successful; thus, PRRS-associated losses will continue into the future. Research to improve our understanding of ecologic and epidemiologic characteristics of the PRRS virus and technologic advances (vaccines and diagnostic tests) to prevent clinical effects are warranted. (J Am Vet Med Assoc 2005;227:385–392)

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in Journal of the American Veterinary Medical Association