DETECTION OF TRYPANOSOMA-CONGOLENSE AND TRYPANOSOMA-BRUCEI SUBSPECIESIN CATTLE IN ZAMBIA BY POLYMERASE CHAIN-REACTION FROM BLOOD COLLECTEDON A FILTER-PAPER

To facilitate epidemiology studies of African trypanosomiasis in cattl e 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 repeti tive nuclear DNA sequences, species-specific DNA amplifications were d etected from the blood of rats infected with Zambian isolates of T. co ngolense 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 buff y coat by the microhematocrit method, and 100 of them were positive fo r the test. These 100 animals were further examined by thin blood smea rs and PCR for species identification. The thin blood smear revealed 6 2 and 14 animals with T. congolense and T. brucei subspecies infection , respectively, whereas the PCR detected 73 of the former and 38 of th e latter species. These results indicate that dried blood spots on fil ter papers are a useful source of DNA for detection of African trypano somes by PCR.