Intestinal helminths and malnutrition are independently associated with protection from cerebral malaria in Thailand.

Although human infection with Ascaris appears to be associated with protection from cerebral malaria, there are many potential socio-economic and nutritional confounders related to helminth infection that need to be considered. In a hospital-based study, 37 cases of cerebral malaria and 61 cases of non-severe malaria with high parasite biomass (i.e. hyperparasitaemia and/or circulating schizonts) answered a structured questionnaire and were screened for intestinal helminths. Logistic regression was then used to adjust for the potential confounders. The adjusted odds ratios (OR) and their 95% confidence intervals (CI) still showed a significant protective association for helminths (OR = 0.24; CI = 0.07-0.78, P = 0.02) and malnutrition (OR = 0.11; CI = 0.02-0.58; P = 0.01), with no evidence of interaction between the two. There was also a significant dose-effect trend for the helminth infections (P = 0.048). These results, despite coming from a hospital-based study, indicate that the apparent association between helminths and protection from cerebral malaria is not the result of socio-economic or nutritional confounders.