Use of a PCR assay for the specific and sensitive detection of Trypanosoma Spp. in naturally infected dairy cattle in peri-urban Kampala, Uganda.

The objective of this study was to compare the sensitivity and specificity of the polymerase chain reaction (PCR) with the hematocrit centrifugation technique (HCT) and the mini-anion-exchange centrifugation technique (m-AECT) for diagnosis of trypanosome infections in livestock. In a cross-sectional study, 486 cattle from 50 randomly selected farms in Mukono County, Uganda were investigated in June 1994. The direct parasitological techniques were performed in the field, resulting in 45 (9.3%) animals positive by HCT and 78 (16%) positive by m-AECT. The total prevalence (combined evidence of HCT and m-AECT) was 18.9%, with 78.2% Trypanosoma brucei only, 10.9% T. vivax and 10.9% mixed (T. bruceil T. vivax) infections. Trypanosomes of the subgenus Nannomonas were not detected. DNA was prepared by lysis from 181 randomly selected blood samples and amplified by PCR using species-specific oligonucleotide primers. Overall, the PCR gave positive results in 63 (34.8%) blood samples, with 76.2% positive only for T. brucei, 20.6% positive only for T. vivax and 3.2% positive for mixed (T. bruceil T. vivax) infections. The preliminary results from this study demonstrate that the detection rate of PCR is about two times higher than that of the direct parasitological techniques, suggesting a higher sensitivity. The higher proportion of T. vivax infections detected by PCR as compared to HCT/m-AECT is likely to be due to false parasitological classifications which might occur under field conditions.