Development and implementation of a strategy for intensified screening for gambiense human African trypanosomiasis in Kongo Central province, DRC

Abstract

Background The Democratic Republic of the Congo (DRC) accounts for the majority of the reported gambiense human African trypanosomiasis (HAT) cases. Kongo Central province in the DRC reports a relatively low, yet steady number of cases, and forms a transboundary focus with Angola and the Republic of Congo. This paper describes an intervention aimed at reducing the case burden in Kongo Central by improving passive case detection, complemented with reactive screening. Methodology/Principal findings At the initiation of this programme in August 2015, 620 health facilities were identified and equipped with Rapid Diagnostic Tests (RDTs) for HAT screening. Of these, 603 (97%) reported use of RDTs, and 584 (94%) that continued to use RDTs to the last quarter of 2016 were used in the analysis going forward. Among all health facilities involved, 23 were equipped to confirm HAT by microscopy, and 4 of the latter were equipped to perform molecular testing with loop-mediated isothermal amplification (LAMP). Patients clinically suspected of HAT were tested with an RDT and those with a positive RDT result were referred to the nearest microscopy facility for confirmatory testing. If RDT positive patients were negative by microscopy, they were tested by LAMP, either on fresh blood or blood that was dried on filter paper and transported to a facility performing LAMP. This network of diagnostic facilities reduced the median distance for a patient to travel to a screening facility from 13.7km when the classical card agglutination test for trypanosomiasis (CATT) was used as a screening test in the past, to 3.4km. As a consequence, passive case detection was improved by between 30% and 130% compared to the period before. Furthermore, the proportion of HAT cases detected in early stage disease by passive screening increased from 27% to 64%. Reactive screening took place in 20 villages where cases were reported by passive screening, and in 45 villages in the neighbourhood of these villages. Reactive screening was responsible for detection of 40% of cases, of which, 90% were in first stage of the disease. Conclusions This programme has demonstrated that it is possible to deploy passive screening for HAT at sub-country or country levels in the DRC, and this is made more effective when supplemented with reactive screening. Results and achievements showed an increase in the number of HAT cases detected, the majority of them in early disease, demonstrating that this strategy enables better population coverage and early detection of cases, which is critical in removing the HAT reservoir and interrupting transmission, and could contribute to HAT elimination in regions where it is implemented.

Passive surveillance of human African trypanosomiasis in Côte d’Ivoire: Understanding prevalence, clinical symptoms and signs, and diagnostic test characteristics

“…This is slightly more than proportions reported elsewhere [26]. In passive screening in Kongo Central in DR Congo however, only 39.9% of RDT positives referred for confirmatory testing to the CDT completed their referral [42]. Although the latter authors do not exclude that the group that did not complete the diagnostic examinations might have contained HAT cases, they considered it probable that most lost seropositives would have had a self-limiting illness and recovered.…”

“…The PPV and agreement of most tests was relatively low, compared to previous observations, driven strongly by the underlying low prevalence in the Bonon and Sinfra foci. In DR Congo, the PPV of SD Bioline HAT in passive case detection was 14.4% [42], while among patients with neurological disorders, the PPV of HAT Sero-K-Set was 50% [40], for HAT prevalences of respectively 0.1-0.8% and 2.9%. We observed PPVs for these RDTs of 4.9% and 2.5%, and 14.3% for rHAT Sero-Strip.…”

“…Dried blood spot testing of seropositive unconfirmed subjects to select individuals for additional parasitological follow-up has previously been performed either with serology, in trypanolysis and/or ELISA/Tbg [16,19], or with molecular tests [12]. So far, LAMP has been mainly applied in the field on seropositive microscopy negative subjects, to compensate for the imperfect sensitivity of microscopy [26,42]. Serological and molecular tests have rarely been performed in parallel [24].…”

Estimating the impact of Tiny Targets in reducing the incidence of Gambian sleeping sickness in the North-west Uganda focus

“…However, the broad coverage was the entire area, and the programme did not result in an increase in detection of cases which might be expected when screening is enhanced. A similar passive screening programme in a HAT endemic area of the DRC with no vector control did result in an increase in numbers of cases detected [ 28 ]. Additionally, there was an active screening campaign in the vector control area which did not detect any HAT cases [ 29 ].…”

Estimating the impact of Tiny Targets in reducing the incidence of gambiense sleeping sickness in the North West Uganda focus

“…However, the broad coverage was the entire area and the programme did not result in an increase in detection of cases which might be expected when screening is enhanced. A similar passive screening programme in a HAT endemic area of the DRC with no vector control did result in an increase in numbers of cases detected [29]. Additionally to this was an active screening campaign in the vector control area which did not detect any HAT cases [30].…”