Detection ofTrypanosoma congolenseandTrypanosoma bruceisubspecies by DNA amplification using the polymerase chain reaction

Abstract

SUMMARY: The nuclear DNA ofTrypanosoma congolensecontains a family of highly conserved 369 base pair (bp) repeats. The sequences of three cloned copies of these repeats were determined. An unrelated family of 177 bp repeats has previously been shown to occur in the nuclear DNA ofTrypanosoma brucei brucei(Sloofet al.1983a). Oligonucleotides were synthesized which prime the specific amplification of each of these repetitive DNAs by the polymerase chain reaction (PCR). Amplification of 10% of the DNA in a single parasite ofT. congolenseorT. bruceispp. produced sufficient amplified product to be visible as a band in an agarose gel stained with ethidium bromide. This level of detection, which does not depend on the use of radioactivity, is about 100 times more sensitive than previous detection methods based on radioactive DNA probes. The oligonucleotides did not prime the amplification of DNA sequences in other trypanosome species nor inLeishmania, mouse or human DNAs. Amplification of DNA from the blood of animals infected withT. congolenseand/orT. bruceispp. permitted the identification of parasite levels far below that detectable by microscopic inspection. Since PCR amplification can be conducted on a large number of samples simultaneously, it is ideally suited for large-scale studies on the prevalence of African trypanosomes in both mammalian blood and insect vectors.