Monitoring the elimination of gambiense human African trypanosomiasis in the historical focus of Batié, South-West Burkina Faso

The World Health Organisation has targeted the elimination of human African trypanosomiasis (HAT) as zero transmission by 2030. Continued surveillance needs to be in place for early detection of re-emergent cases. In this context, the performance of diagnostic tests and testing algorithms for detection of the re-emergence of Trypanosoma brucei gambiense HAT remains to be assessed. We carried out a door-to-door active medical survey for HAT in the historical focus of Batié, South-West Burkina Faso. Screening was done using three rapid diagnostic tests (RDTs). Two laboratory tests (ELISA/T. b. gambiense and immune trypanolysis) and parasitological examination were performed on RDT positives only. In total, 5883 participants were screened, among which 842 (14%) tested positive in at least one RDT. Blood from 519 RDT positives was examined microscopically but no trypanosomes were observed. The HAT Sero-K-Set test showed the lowest specificity of 89%, while the specificities of SD Bioline HAT and rHAT Sero-Strip were 92% and 99%, respectively. The specificity of ELISA/T. b. gambiense and trypanolysis was 99% (98-99%) and 100% (99-100%), respectively. Our results suggest that T. b. gambiense is no longer circulating in the study area and that zero transmission has probably been attained. While a least cost analysis is still required, our study showed that RDT preselection followed by trypanolysis may be a useful strategy for post-elimination surveillance in Burkina Faso.</p

Malaria morbidity in high and seasonal malaria transmission area of Burkina Faso.

Malariometric parameters are often primary endpoints of efficacy trials of malaria vaccine candidates. This study aims to describe the epidemiology of malaria prior to the conduct of a series of drug and vaccine trials in a rural area of Burkina Faso.Malaria incidence was prospectively evaluated over one year follow-up among two cohorts of children aged 0-5 years living in the Saponé health district. The parents of 1089 children comprising a passive case detection cohort were encouraged to seek care from the local health clinic at any time their child felt sick. Among this cohort, 555 children were randomly selected for inclusion in an active surveillance sub-cohort evaluated for clinical malaria during twice weekly home visits. Malaria prevalence was evaluated by cross-sectional survey during the low and high transmission seasons.Number of episodes per child ranged from 0 to 6 per year. Cumulative incidence was 67.4% in the passive and 86.2% in the active cohort and was highest among children 0-1 years. Clinical malaria prevalence was 9.8% in the low and 13.0% in the high season (p>0.05). Median days to first malaria episode ranged from 187 (95% CI 180-193) among children 0-1 years to 228 (95% CI 212, 242) among children 4-5 years. The alternative parasite thresholds for the malaria case definition that achieved optimal sensitivity and specificity (70-80%) were 3150 parasites/µl in the high and 1350 parasites/µl in the low season.Clinical malaria burden was highest among the youngest age group children, who may represent the most appropriate target population for malaria vaccine candidate development. The pyrogenic threshold of parasitaemia varied markedly by season, suggesting a value for alternative parasitaemia levels in the malaria case defintion. Regional epidemiology of malaria described, Sapone area field centers are positioned for future conduct of malaria vaccine trials

Suivi de l’élimination de la Trypanosomiase Humaine Africaine dans le foyer historique de Batié au sud-ouest du Burkina Faso

International audienceThe World Health Organisation has targeted the elimination of human African trypanosomiasis (HAT) as zero transmission by 2030. Continued surveillance needs to be in place for early detection of re-emergent cases. In this context, the performance of diagnostic tests and testing algorithms for detection of the re-emergence of Trypanosoma brucei gambiense HAT remains to be assessed. We carried out a door-to-door active medical survey for HAT in the historical focus of Batié, South–West Burkina Faso. Screening was done using three rapid diagnostic tests (RDTs). Two laboratory tests (ELISA/T. b. gambiense and immune trypanolysis) and parasitological examination were performed on RDT positives only. In total, 5883 participants were screened, among which 842 (14%) tested positive in at least one RDT. Blood from 519 RDT positives was examined microscopically but no trypanosomes were observed. The HAT Sero-K-Set test showed the lowest specificity of 89%, while the specificities of SD Bioline HAT and rHAT Sero-Strip were 92% and 99%, respectively. The specificity of ELISA/T. b. gambiense and trypanolysis was 99% (98–99%) and 100% (99–100%), respectively. Our results suggest that T. b. gambiense is no longer circulating in the study area and that zero transmission has probably been attained. While a least cost analysis is still required, our study showed that RDT preselection followed by trypanolysis may be a useful strategy for post-elimination surveillance in Burkina Faso

Age-specific incidence of fever over one year follow-up.

<p>Age-specific incidence of fever over one year follow-up.</p

Time to first malaria episode among children 0–5 years evaluated by active surveillance from the low through high transmission season.

<p>Time to first malaria episode among children 0–5 years evaluated by active surveillance from the low through high transmission season.</p

Malaria case definition using objective fever according to the season.

<p>a. Sensitivity and specificity of alternative parasite threshold for malaria case definition in the high transmission season using objective (> = 37.5 degrees C) fever. b. Sensitivity and specificity of alternative parasite threshold for malaria case definition in the low transmission season using objective (> = 37.5 degrees C) fever.</p

Incidence density of malaria episode according to season and different level of parsitemia.

<p>Incidence density of malaria episode according to season and different level of parsitemia.</p

Age-specific malaria incidence according to the season.

<p>a. Seasonal variation in age-specific clinical malaria incidence evaluated by active surveillance over one year. b. Seasonal variation in age-specific clinical malaria incidence evaluated by passive surveillance over one year.</p

Malariometric parameters Prevalence by Age Group in active surveillance cohort according to the season.

<p>Malariometric parameters Prevalence by Age Group in active surveillance cohort according to the season.</p