DETECTION OF THEILERIA-SERGENTI INFECTION IN CATTLE BY POLYMERASE CHAIN-REACTION AMPLIFICATION OF PARASITE-SPECIFIC DNA

A pair of synthetic oligonucleotide primers, designed from the gene en coding a 32-kDa intraerythrocytic piroplasm surface protein of Theiler ia sergenti, were used to amplify parasite DNA from the blood of T. se rgenti-infected cattle by means of the polymerase chain reaction (PCR) . PCR-amplified DNA was examined by electrophoresis and by dot blot or microplate hybridization using a parasite-specific cDNA probe. PCR wa s specific for T. sergenti, since no amplification was detected with D NA from Anaplasma centrale, Babesia ovata, uninfected erythrocytes, an d leukocytes. This method was sensitive enough to detect about 4.5 par asites per mul of blood with a 10-mul sample volume. Moreover, of 66 s pecimens from grazing cattle, 40 were microscopically positive, wherea s PCR revealed that 54 samples were positive. Therefore, PCR provides a useful diagnostic tool for detecting T. sergenti-infected cattle, an d it is significantly more sensitive than the current methods.