Plasmodium-helminth coinfection and its sources of heterogeneity across East Africa

Abstract

Background: Plasmodium-helminth coinfection can have a number of consequences for infected hosts, yet our knowledge of the epidemiology of coinfection across multiple settings is limited. This study investigates the distribution and heterogeneity of coinfection with Plasmodium falciparum and 3 major helminth species across East Africa.

Methods: Cross-sectional parasite surveys were conducted among 28 050 children in 299 schools across a range of environmental settings in Kenya, Uganda, and Ethiopia. Data on individual, household, and environmental risk factors were collected and a spatially explicit Bayesian modeling framework was used to investigate heterogeneities of species infection and coinfection and their risk factors as well as school- and individual-level associations between species.

Results: Broad-scale geographical patterns of Plasmodium-helminth coinfection are strongly influenced by the least common infection and by species-specific environmental factors. At the individual level, there is an enduring positive association between P. falciparum and hookworm but no association between P. falciparum and Schistosoma species. However, the relative importance of such within-individual associations is less than the role of spatial factors in influencing coinfection risks.

Conclusions: Patterns of coinfection seem to be influenced more by the distribution of the least common species and its environmental risk factors, rather than any enduring within-individual associations.

Figure 1.

Geographical distribution of Plasmodium or helminth monoinfection and coinfection among school children in 299 schools in Ethiopia, Kenya, and Uganda. A, Plasmodium falciparum and hookworm coinfection. B, P. falciparum and schistosome (either Schistosoma haematobium along the coast of Kenya or Schistosoma mansoni elsewhere) coinfection.

Figure 1.

Geographical distribution of Plasmodium or helminth monoinfection and coinfection among school children in 299 schools in Ethiopia, Kenya, and Uganda. A, Plasmodium falciparum and hookworm coinfection. B, P. falciparum and schistosome (either Schistosoma haematobium along the coast of Kenya or Schistosoma mansoni elsewhere) coinfection.

Figure 2.

Relationship between the prevalence of Plasmodium–helminth coinfection and the least and most common species among schoolchildren in 299 schools in Ethiopia, Kenya, and Uganda, according to species: coinfection with Plasmodium falciparum and hookworm and (A) least common and (B) most common species; coinfection with P. falciparum and schistosome (either Schistosoma mansoni or Schistosoma haematobium) infection and (C) least common and (D) most common species, as defined on a school-by-school basis. Line of identity is indicated by dashed line. Overall correlation coefficients for each graph: (A) 0.937, (B) 0.685, (C) 0.967, and (D) 0.615; all P < .001.

Figure 3.

Geographical distribution of Plasmodium–helminth monoinfection and coinfection among school children in the subset analysis: 4220 children in 56 schools in western Kenya and eastern Uganda (A and B) and 5232 children in 51 schools in south coastal Kenya (C).