Detection of Trypanosoma congolense and T. brucei subspecies in cattle in Zambia by polymerase chain reaction from blood collected on a filter paper.

To facilitate epidemiology studies of African trypanosomiasis in cattle in Zambia, we adapted a polymerase chain reaction (PCR) method using blood spotted on filter papers. For easy preparation of template DNA from the dried blood, we adapted a simple DNA extraction method using Chelex-100, an anion-exchange resin. Using primers directed for repetitive nuclear DNA sequences, species-specific DNA amplifications were detected from the blood of rats infected with Zambian isolates of T. congolense and T. brucei subspecies. The method was sensitive enough to detect a single trypanosome for both species. In the Eastern Province of Zambia, 240 cattle were examined for motile flagellates in the buffy coat by the microhematocrit method, and 100 of them were positive for the test. These 100 animals were further examined by thin blood smears and PCR for species identification. The thin blood smear revealed 62 and 14 animals with T. congolense and T. brucei subspecies infection, respectively, whereas the PCR detected 73 of the former and 38 of the latter species. These results indicate that dried blood spots on filter papers are a useful source of DNA for detection of African trypanosomes by PCR.