Ascaris lumbricoides infection is associated with protection from cerebral malaria

Abstract

Following reports of increased IgE in severe malaria and hypothesizing that helminth coinfections could modify its outcome, we conducted a retrospective case-control study to establish whether helminths affect the evolution of Plasmodium falciparum malaria. Some 182 severe cases, 315 mild controls and 40 controls with circulating schizonts were examined for intestinal helminths. Comparing cerebral malaria with mild controls, Ascaris lumbricoides was associated with a protective adjusted odds ratio (OR) of 0.58 (0. 32-1.03) P = 0.06, for coinfection with Ascaris and Necator americanus, OR = 0.39 (0.17-0.88) P = 0.02. Protection followed a dose-effect trend (P = 0.008). When comparing cerebral malaria cases and controls with circulating schizonts the OR was 0.25 (0.009-0.67) P = 0.006. We hypothesized that Ascaris infected patients may have had decreased cyto-adherence, possibly through endothelial cell receptor downregulation and/or decreased splenic clearance leading to the absence of selection of virulent P. falciparum strains. IgE-anti-IgE immune complexes resulting from helminth preinfection may have an important role in influencing clinical presentation of severe malaria, and in establishing malaria tolerance, through the CD23/NO pathway.

Association of helminth infections with increased gametocyte carriage during mild falciparum malaria in Thailand.

“…In remote areas, where malaria treatment is likely to be delayed, treating helminths could theoretically result in less anemia and gametocyte carriage during falciparum malaria, but it could also increase the risk of cerebral malaria. 7 Thus the extent of harmful 14 and beneficial consequences 7 of helminth infections may need further investigations in order to define malaria and helminth control strategies.…”

“…We recently observed an association of helminth infections with protection from cerebral malaria, 7 with indirect elements suggesting decreased cytoadherence in helminthinfected patients. We also observed decreased hemoglobin concentrations in helminth-infected mild falciparum malaria cases.…”

Influence of Soil Transmitted Helminths Infection Towards Malaria Disease

“…Multiple parasitic infections will affect the patient's immune system and have an impact on the clinical manifestations of diseases [5], [8]. Most studies suggest that STH are protective against malaria infection [9], [10], although some are found different results [11], [12], [13]. Double infection of malaria and STH is influenced by many factors, such as parasitic species and genetic factors of the patient.…”

Association of splenomegaly with cerebral malaria and decreased concentrations of reactive nitrogen intermediates in Thailand.

“…The fact that there were significant differences in the prevalence of splenomegaly, but not for RNI concentrations, between cases and controls can be reconciled with the fact that in both groups RNI concentrations were lower in patients with splenomegaly (Table 3), if we assume that the NO induction pathway also affected spleen size. Th1 cytokines, may have increased immune proliferation within the spleen 10 and induced NO release, whereas Th2 cytokines, through the CD23/NO pathway, 21 may have led to NO release without prior stimulation of spleen cells.…”