Table 1.

Key clinical publications on soil-transmitted helminth and malaria coinfection.

Organism	Country	Ascaris spp.	Hookworm	Trichuris spp.	Strongyloides spp.	All soil-transmitted helminths	Findings	Ref.
Hookworm	Malawi		↑ IR				Hookworm infection associated with malaria infection in a cross-sectional study	[74]
Ascaris lumbricoides	Gabon	↑ IR					A. lumbricoides associated with Plasmodium infection during pregnancy. Sensitivity of hookworm assay not considered sufficient for analysis. Study was a cross-sectional analysis within a clinical trial	[59]
Soil-transmitted helminths	Thai–Burmese border	↓ IR	↑ IR ↑ DS				A. lumbricoides infection was associated with a decreased risk of malaria in a cross-sectional analysis. Hookworm infection was associated with an increased risk of malaria and anemia. Any spp. of malaria was evaluated	[60]
A. lumbricoides, hookworm, Trichuris spp.	Brazil	↓ DS	↓ DS	↓ DS			Decreased drop in hemoglobin during acute Plasmodium vivax infection for helminth-infected children	[64]
A. lumbricoides, hookworm, Trichuris spp.	Uganda		↑ DS				Hookworm infection associated with lower hemoglobin level during malaria infection in school-aged children. Spatial and household clustering of coinfection noted	[69]
A. lumbricoides, hookworm, Trichuris spp.	Ethiopia		↑ DS			↓ DS	Higher malaria parasite density among those with hookworm infection. Soil-transmitted helminth infection negatively correlated with the severe malaria symptoms	[68]
A. lumbricoides, hookworm, Trichuris spp.	Ghana						Whole blood samples from helminth-infected children were exposed to malaria infected RBCs and expressed increased levels of IL-10, SOCS-3, FoxP3 and PD-1	[78]
A. lumbricoides, hookworm, Trichuris spp., Strongyloides spp.	Ghana	↑ IR	↑ IR	No Assoc.	No Assoc.		Pregnant women with hookworm and Ascaris infection had increased rates of malaria infection. No association was seen with Strongyloides or Trichura spp.	[73]
All gastrointestinal helminth, Ascaris	Kenya	No Assoc.					Gastrointestinal helminth infection and eosinophilia were statistically not associated with malaria susceptiblity	[76]
Hookworm, Trichuris spp., Strongyloides spp.	Uganda		↑ IR	No Assoc.	No Assoc.		Cross-sectional study in which hookworm infection is associated with malaria infection. No association noted with Trichuris or Strongyloides spp. infection	[71]
Hookworm, Trichuris, Ascaris	Zimbabwe		↑ IR				Hookworm infection is associated in a cross-sectional analysis with P. falciparum malaria infection	[70]
A. lumbricoides	Madagascar	↓ DS					Ascaris treatment with levamisole associated with increase in P. falciparum densities among 4–15-year-olds	[62,63]
A. lumbricoides, hookworm, Trichuris spp.	Uganda					No Assoc.	No association observed between intestinal helminth infection and malaria risk in a cross-sectional household-based sample	[61]
A. lumbricoides	Senegal	↑ DS					Higher prevalence in a prospective case–control study of Ascaris infection in individuals with severe malaria	[67]
Soil-transmitted helminths	Thailand					↑ DS	Helminth-infected subjects were more likely to develop falciparum clinically symptomatic malaria in a prospective trial	[75]
A. lumbricoides, hookworm	Thailand	↓ DS	↓ DS				A. lumbricoides and Necator americanus (hookworm) was associated with protection from cerebral malaria in a case–control trial. Helminth infection was associated with lower rates of renal failure, jaundice and peripheral mature schizonts. Helminth-infected individuals had higher reactive nitrogen intermediates in blood samples	[65,75,79]

DS measures include parasite density, severity of anemia and prevalence/incidence of severe malaria (or one of the severe malaria criteria including cerebral malaria). IR refers to any measure of infection, including incidence or prevalence.

Assoc.: Association; DS: Disease severity; IR: Infection rate; PD: Programmed death; RBC: Red blood cell.