Comparison of an improved polymerase chain reaction protocol and the indirect hemagglutination assay in the detection of Eperythrozoon suis infection

Department of Veterinary Diagnostic Investigation, College of Veterinary Medicine, Kansas State University, Manhattan 66506. The ability of an improved polymerase chain reaction (PCR) protocol to detect Eperythrozoon suis DNA in the blood of experimentally infected nonsplenectomized pigs was evaluated. The protocol utilizes previously described E. suis-specific primers and a proprietary DNA-releasing reagent in a 2-step amplification cycle followed by visualization of the 492-bp amplification product on agarose gels. This PCR protocol successfully amplified E. suis DNA in blood from all postinfection samples and from the preinfection samples of 2 pigs, indicating preexisting natural infections. Results of the indirect hemagglutination test on serum samples from these pigs revealed that only 1 pig developed detectable antibody titers to E. suis infection during the 43-day study; that pig was determined by PCR to have been infected naturally with E. suis prior to experimental inoculation. These results confirm previous reports of poor antibody response of young pigs to E. suis infection and demonstrate the potential of PCR as a valuable tool for the diagnosis and study of E. suis infection in pigs.