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Identifying contributing factors to poor respiratory health is key to implementing effective control strategies. Serologic evaluation of pigs in late finishing can be a significant point to determine which of the main swine respiratory pathogens — PRRS virus, Mycoplasma hyopneumoniae or Swine Influenza Virus — are involved.

When groups of pigs are seropositive to these pathogens, clinically or subclinically, impairment in growth rate may be observed. Higher antibody titers were consistently associated with lower ADG in an IL study. Positive pigs grew from 18 gm (SIV) to approximately 40 gm/day (PRRS & Mycoplasma) slower than negative pigs. When pig groups were studied for exposure, the same pattern was noted. When greater than half of pigs were positive, a reduction in average gain of >20 gm/day was seen. For a typical exposure to Mycoplasma, that corresponds to 10 pounds less gain to market for surviving pigs.

A simple diagram (A) is displayed above. Twenty pigs per group, for five or more groups, are bled just prior to marketing. Serum is tested for antibodies to PRRS, Mycoplasma and SIV.

If exposure has occurred, pigs will show serologic evidence of this challenge. By confirming when pigs are exposed to disease, antibiotic and vaccine treatments can be optimally timed for maximum benefit. Diagram B completes the investigation outline for positive groups.

Post mortem examinations, slaughter checks and clinical monitoring may be added in some situations. Your herd veterinarian and diagnostic lab partners can assist in fine tuning the diagnostic process to meet your herd's particular disease challenge situation.

More information

Regula G, et al. Comparison of serologic testing and slaughter evaluation for assessing the effects of subclinical infection on growth in pigs. J Am Vet Med Assoc. 2000; 217: 888-895.

Maes D, et al. Mycoplasma hyopneumoniae: Benefit to Cost of Vaccination. Proceedings of American Association of Swine Veterinarians, February 2001; 327-334.

Bahnson PB. Ph.D Thesis, University of Minnesota. 1994.

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