Porcine reproductive and respiratory syndrome virus: Age and management system disease modeling for pathogenic co-infection
Paul M. Dorr, DVM, PhD; Wondwossen A. Gebreyes, DVM, PhD, Diplomate ACVPM; Glen W. Almond, DVM, MSc, PhD
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Objectives: To construct models evaluating statistically significant associations between porcine reproductive and respiratory syndrome virus (PRRSV) and co-infectious agents, and to assess effects of changes in age and management system on co-infection status, serological profiles, lung lesions, and histopathological lesions in PRRSV-positive pigs
Materials and methods: Pigs 3, 9, 16, and 24 weeks of age from 41 sow sources representing one-, two-, and three-site production systems were necropsied on the basis of acute, subacute, and chronic disease stages (n = 5 animals per age group per farm). Logistic regression models were used to assess co-infection with other pathogens, serological profiles, and histopathological lesions in pigs PRRSV-positive by polymerase chain reaction and with lung lesions consistent with PRRSV infection, and in PRRSV-negative pigs. Additional models were stratified by age and type of production system.
Results: In the overall model, clinically ill PRRSV-positive pigs were more likely than PRRSV-negative pigs to be co-infected with swine influenza virus (SIV) type A (OR, 2.40; 95% CI, 1.07-5.39) and to have lung scores in the 11% to 50% range (OR, 1.65; 95% CI, 1.06-2.57). Three-week-old PRRSV-positive pigs were more likely to be co-infected with porcine circovirus type 2 (OR, 8.83; 95% CI, 1.76-44.26). Nine- and 16-week-old pigs were 15.57 and 5.75 times as likely to be co-infected with SIV, respectively.
Implications: Changes in PRRSV infection, disease manifestation, and associated co-factors such as age and type of management system are important considerations for prevention, vaccination timing, diagnostic testing, and treatment for disease complexes associated with PRRSV.
Keywords: porcine reproductive and respiratory syndrome virus, PRRSV, co-infection, disease modeling, epidemiology
Cite as: Dorr PM, Gebreyes WA, Almond GW. Porcine reproductive and respiratory syndrome virus: Age and management system disease modeling for pathogenic co-infection. J Swine Health Prod 2007;15(5):258-264.
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