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United States Department of Agriculture

Agricultural Research Service

Title: Synergism Between Porcine Reproductive and Respiratory Syndrome Virus (Prrsv) and Salmonella Choleraesuis in Swine

Authors
item Wills, Robert - IOWA STATE UNIVERSITY
item Gray, Jeffrey
item Cray, Paula
item Yoon, K - IOWA STATE UNIVERSITY
item Ladely, Scott
item Zimmerman, J - IOWA STATE UNIVERSITY

Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 29, 1999
Publication Date: October 29, 1999
Citation: Wills, R.W., Gray, J.T., Cray, P.J., Yoon, K.J., Ladely, S.R., Zimmerman, J. 1999. Synergism between porcine reproductive and respiratory syndrome virus (prrsv) and salmonella choleraesuis in swine. Veterinary Microbiology. 71: P.177-192

Interpretive Summary: Porcine reproductive and respiratory syndrome virus (PRRSV) and Salmonella choleraesuis are important components of the porcine respiratory disease complex. PRRSV and S. choleraesuis are two leading causes of economic loss in the swine industry. While respiratory disease is common in both S. choleraesuis and PRRSV infections, the factors that contribute to its development remain largely undefined. The objective of this study was to characterize the interaction of PRRSV, Salmonella choleraesuis, and stress in the production of disease in young swine. All combinations of three factors (inoculation with S. choleraesuis on day 0, PRRSV on day 3, and treatment with dexamethasone (a stressor) on days 3 to 7) were used to produce eight treatment groups in two independent trials. Fecal samples, tonsil and nasal swabs, serum samples and postmortem tissues were collected for bacteriologic and virologic examinations. No clinical signs were observed in pigs inoculated with only PRRSV or only S. choleraesuis. In contrast, pigs which were infected with S. choleraesuis and PRRSV were severely affected while pigs which received all three treatment factors were severely affected and 43 percent (3 of 7) of animals in this group died. These results suggested that PRRSV, S. choleraesuis, and dexamethasone acted together to produce a syndrome similar to that observed in the field. This work can serve as a model for future study of the disease by veterinarians and other researchers.

Technical Abstract: Porcine reproductive and respiratory syndrome virus (PRRSV) and Salmonella choleraesuis are two leading causes of economic loss in the swine industry. While respiratory disease is common in both S. choleraesuis and PRRSV infections, the factors that contribute to its development remain largely undefined. We investigated the interaction of PRRSV, S. choleraesuis, and stress in 5-week-old swine. All combinations of three factors (inoculation with S. choleraesuis on Day 0, PRRSV on Day 3, and treatment with dexamethasone on Days 3-7) were used to produce eight treatment groups in two independent trials. Fecal samples, tonsil and nasal swabs, serum samples and postmortem tissues were collected for bacteriologic and virologic examinations. No clinical signs were observed in pigs inoculated with only PRRSV or only S. choleraesuis. In contrast, pigs which were dually infected with S. choleraesuis and PRRSV exhibited unthriftiness, rough hair coats, dyspnea, and diarrhea. The pigs which received all three treatment factors were the most severely affected and 43% (three of seven) of the animals in this group died. Individuals in this group shed significantly higher quantities of S. choleraesuis in feces and had significantly higher serum PRRSV titers compared to other treatments (p</= 0.05). In addition, S. choleraesuis and PRRSV were shed longer and by more pigs in this group than other groups and S. choleraesuis was recovered from more tissues in this group on Day 21 post inoculation. These results suggested that PRRSV, S. choleraesuis, and dexamethasone acted synergistically to produce a syndrome similar to that observed in the field.

Last Modified: 4/16/2014
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