Spatial co-distribution of neglected tropical diseases in the east African great lakes region: revisiting the justification for integrated control

Abstract

Objective: To determine spatial patterns of co-endemicity of schistosomiasis mansoni and the soil-transmitted helminths (STHs) Ascaris lumbricoides, Trichuris trichiura and hookworm in the Great Lakes region of East Africa, to help plan integrated neglected tropical disease programmes in this region.

Method: Parasitological surveys were conducted in Uganda, Tanzania, Kenya and Burundi in 28 213 children in 404 schools. Bayesian geostatistical models were used to interpolate prevalence of these infections across the study area. Interpolated prevalence maps were overlaid to determine areas of co-endemicity.

Results: In the Great Lakes region, prevalence was 18.1% for Schistosoma mansoni, 50.0% for hookworm, 6.8% for A. lumbricoides and 6.8% for T. trichiura. Hookworm infection was ubiquitous, whereas S. mansoni, A. lumbricoides and T. trichiura were highly focal. Most areas were endemic (prevalence >or=10%) or hyperendemic (prevalence >or=50%) for one or more STHs, whereas endemic areas for schistosomiasis mansoni were restricted to foci adjacent large perennial water bodies.

Conclusion: Because of the ubiquity of hookworm, treatment programmes are required for STH throughout the region but efficient schistosomiasis control should only be targeted at limited high-risk areas. Therefore, integration of schistosomiasis with STH control is only indicated in limited foci in East Africa.

Figure 1

Prevalence of (a) Schistosoma mansoni; (b) hookworm; (c) Ascaris lumbricoides and (d) Trichuris trichiura in school-aged children, Great Lakes region, East Africa 1998–2005.

Figure 2

Predicted prevalence of Schistosoma mansoni infection in boys, 15–19 years, East Africa (inset Burundi) 1998–2007. Estimates are the mean posterior predicted prevalence values from a Bayesian geostatistical model.

Figure 3

Predicted prevalence of hookworm infection in boys, 15–19 years, East Africa (inset Burundi) 1998–2007. Estimates are the mean posterior predicted prevalence values from a Bayesian geostatistical model.

Figure 4

Predicted prevalence of Ascaris lumbricoides infection in boys, 15–19 years, East Africa (inset Burundi) 1998–2007. Estimates are the mean posterior predicted prevalence values from a Bayesian geostatistical model.

Figure 5

Predicted prevalence of Trichuris trichiura infection in boys, 15–19 years, East Africa (inset Burundi) 1998–2007. Estimates are the mean posterior predicted prevalence values from a Bayesian geostatistical model.

Figure 6

Predicted areas of co-endemicity for Schistosoma mansoni and one or more soil-transmitted helminth infections, East Africa. Hyperendemicity is defined as prevalence ≥50%, and endemicity is defined as prevalence ≥10% but <50%. Maps are based on predictions for boys aged 15–19.