Comparison of PCR with Parasitology and Serology in the Diagnosis of a Low Virulent Strain of Trypanosoma brucei gambiense in mice

Abstract

BALB/c mice infected with a low virulent strain of Trypanosoma brucei gambiense IL3253 were treated intraperitoneally（ip）with either Melarsoprol （Mel-B, obtained from WHO，Geneva）or phosphate-buffered saline（PH 7.8） containing 1％ glucose （PSG） as controls. The mice were subsequently monitored regularly for parasites by direct microscopic examination of their tail blood or buffy coat and by polymerase chain reaction（PCR）．Suratex®（AccuPharma，NY）， an　assay　that　detects　circulating trypanosome parasite antigen，was also used．Mel-B was found to be an effective drug for treatment against T.b. gambiense and at the end of the first treatment schedule of 3 series of 3 injections at 7 days post- infection（DPI），all treated mice were negative for parasites even by PCR, while all the control animals were positive. Suratex®（AccuPharma, NY）was found to be inappropriate in the serodiagnosis of trypanosomosis due to T.b. gambiense in mice as it gave high levels of false positives. At 34 DPI, all the BALB/c mice were sacrificed and 0.5ml of their blood injected ip into individual SCID mice. The SCID mice were likewise monitored for parasites or for evidence of infection by microscopic examination and PCR for up to 115 DPI. None of the SCID mice injected with blood from BALB/c previously treated with Mel-B showed any parasite either in their tail blood or buffy coat over the entire sampling period, though some of these mice were shown to harbor an infection by PCR at some time over the sampling interval. This experiment affirms the importance of the various techniques used in the diagnosis of trypanosomosis. A repeated　negative　 PCR　test　in　combination　with　clinical　and conventional microscopical examination may be a useful diagnostic regimen in the diagnosis of trypanosomosis.