Detection and Control of The Dry Season Plasmodium Falciparum Gametocyte Reservoir in Gedaref State- Eastern Sudan

Abstract

A large proportion of people who contract malaria during the wet season in areas of marked seasonal transmission retain chronic submicroscopic asymptomatic infections throughout the dry season. A study was therefore carried out in two villages Taiba and Abu Al Naja, in Gedaref State to evaluate the effectiveness of gametocytocidal drugs in eliminating gametocytes among inhabitants before the start of the transmission season. Parasitological and entomological surveys were conducted during the dry, pre-transmission and transmission seasons of 2001 and 2002. In the intervention village, all inhabitants harbouring gametocytes during the pre-transmission season received a schizontocidal drug (chloroquine) and a gametocytocidal drug (primaquine), while asymptomatic parasite carriers in the control village did not receive antimalarial treatment. Detection of sub-patent parasitaemia was performed by polymerase chain reaction (PCR) and reverse transcription (RT)-PCR was used for the detection of gametocytes among those with sub-patent parasitaemia. The entomological findings at the study areas, reported zero inoculation rates and low mosquito density during the pre-transmission and transmission seasons of 2001 and 2002. Overall, 40.03% and 28.8% of the studied population harboured sub-patent infections in the intervention and control villages, respectively, in dry season 2001. In 2002, sub-patent parasitaemia existed in only 6% and 4% of the population in the intervention and control villages, respectively. RT-PCR showed a significant reduction in the prevalence of gametocyte carriage in the intervention village from 12.4% during the pre-transmission season of 2001 to 8% during the pre-transmission season of 2002, compared to a constant figure of 10% in the control village during the same period. In addition, there was a significant increase in the parasite prevalence in the control compared to the intervention village in the transmission season of the 2002 (12.03% and 3.8%, respectively). The analysis of the clinical questionnaire at Taiba (2000) showed that most of the examined cases (582/611) did not show symptoms of infection (asymptomatic) and only 2.9% (18/611) were febrile with other symptoms; six of them were truly microscopically positive. Whereas 1.8% (11/611) were a-febrile with other symptoms and only two of them actually harboured the parasite. All asymptomatic cases and those with febrile and other symptoms cases, mentioned histories of malaria during the pre-transmission season 2001, were found harbouring sub-patent parasites as detected by PCR during the dry season 2001. In conclusion: the present study showed that targeting the gametocyte reservoir by administering gametocytocidal drugs during the pre-transmission season has a significant impact in reducing malaria burden in the short transmission season at the intervention village