Rapid Epidemiological and Entomological Survey for Validation of Reported Indicators and Characterization of Local Malaria Transmission in Guinea, 2017

Abstract

To confirm and investigate possible explanations for unusual trends in malaria indicators, a protocol for rapid, focal assessment of malaria transmission and control interventions was piloted in N'Zérékoré and Macenta Prefectures, which each reported surprisingly low incidence of malaria during the peak transmission months during 2017 in holoendemic Forested Guinea. In each prefecture, epidemiological and entomological cross-sectional surveys were conducted in two sub-prefectures reporting high incidence and one sub-prefecture reporting low incidence. Investigators visited six health facilities and 356 households, tested 476 children, performed 14 larval breeding site transects, and conducted 12 nights of human landing catches during the 2-week investigation. Rapid diagnostic test positivity in the community sample of children under five ranged from 23% to 68% by subprefecture. Only 38% of persons with fever reported seeking care in the public health sector; underutilization was confirmed by verification of health facility and community healthcare worker (CHW) registries. High numbers of Anopheles mosquitoes were collected in human landing collections in N'Zérékoré (38 per night in combined indoor and outdoor collections) and Macenta (87). Most of the detected breeding sites positive for Anopheles larvae (83%) were shallow roadside puddles. In the investigated prefectures, malaria rates remain high and the low reported incidence likely reflects low utilization of the public health-care sector. Strengthening the CHW program to rapidly identify and treat malaria cases and elimination of roadside puddles as part of routine cleanup campaigns should be considered. Systematic joint epidemiological/entomological investigations in areas reporting anomalous signals in routine data can allow control programs to respond with tailored local interventions.

Figure 1.

Location of subprefectures reporting high incidence (blue circles) and low incidence (yellow triangles) visited during joint epidemiological/entomological investigation in N’Zérékoré (A) and Macenta (B) Prefectures, Guinea. This figure appears in color at www.ajtmh.org.

Figure 2.

Distribution of reported health-care seeking behavior in community members reporting fever in the preceding 2 weeks, assessed during joint entomological/epidemiological investigation in N’Zérékoré (A) and Macenta (B) Prefectures, Guinea. This figure appears in color at www.ajtmh.org.

Figure 3.

Counts of monthly all-cause patient consults recorded by community health-care workers (CHWs), health facilities, and health posts, assessed during joint entomological/epidemiological investigation in N’Zérékoré (A) and Macenta (C) Prefectures, Guinea; and counts of monthly all-cause patient consults after exclusion of confirmed malaria cases in N’Zérékoré (B) and Macenta (D) Prefectures, Guinea. This figure appears in color at www.ajtmh.org.

Figure 4.

Mean number of Anopheles collected in human landing collections and human behavioral observations conducted in N’Zérékoré and Macenta. Two human landing collections (comprised indoor and outdoor collections) were made per night in the subprefectures of: (A) Palé, (B) Koropara, (C) Samoé, (D) Bofossou, (E) Daro, and (F) Serédou. The second night of human behavioral observations (number of people observed in the courtyard at each hour) is presented here.