Monitoring the developmental status of Trypanosoma brucei gambiense in the tsetse fly by means of PCR analysis of anal and saliva drops.

Teneral Glossina palpalis gambiensis (Diptera: Glossinidae) were infected with a culture of procyclic forms of Trypanosoma brucei gambiense using a single-bloodmeal membrane feeding technique. The infection was monitored by analysing the saliva (mature infection) and anal drop (midgut infection) of each fly at different post-infection times both by microscopic observation and polymerase chain reaction (PCR). Amplification revealed many more positive anal drops than microscopy. The monitoring showed that the installation of T. b. gambiense in Glossina took place at least 11 days after the infection and that maturation occurred after 29 days. It also reflected precisely the parasitic status of each tsetse fly as determined by the dissection, microscopic examination and PCR amplification of the midguts and salivary glands 47 days post-infection. Twice as many tsetse flies with mature salivary glands infection were revealed by PCR than by microscopic examination, but the two techniques gave exactly the same results regarding the proportion of flies with midgut infection. This study also demonstrated the ability of natural non-infective procyclic forms of T. b. gambiense, to colonise the midgut and subsequently establish in the salivary glands of G. p. gambiensis.