Contemporaneous and successive mixed Plasmodium falciparum and Plasmodium vivax infections are associated with Ascaris lumbricoides: an immunomodulating effect?
Following an investigation suggesting a protective role for Ascaris against cerebral malaria, possibly through immunomodulation, we examined whether Ascaris had any impact on mixed Plasmodium falciparum and Plasmodium vivax infections. We studied a cross section of 928 patient files between 1991 and 1999. Forty patients had contemporaneous mixed infections and 40 patients had P. falciparum infections, followed by P. vivax infections. There was a significant association between Ascaris infection and risk of having both contemporaneous or successive mixed P. falciparum and P. vivax infections (adjusted odds ratios respectively 6 [2-18] P = 0.001 and 3.6 [1.2-11.1] P = 0.02). There was a positive linear trend between the burden of Ascaris and the risk of mixed infections P < 0.0001. These results suggested the possibility that pre-existing Ascaris infection may increase tolerance of the host to different Plasmodium spp., thus facilitating their coexistence.
Nacher
M
M
Cellulaire et Moléculaire des Infections Parasitaires, Faculté de médecine Pitié-Salpétrière, Paris, France.
Singhasivanon
P
P
Gay
F
F
Silachomroon
U
U
Phumratanaprapin
W
W
Looareesuwan
S
S
D000818:Animals; D001196:Ascariasis / Q000150:complications* / Q000276:immunology; D017164:Ascaris lumbricoides; D003430:Cross-Sectional Studies; D006801:Humans; D007108:Immune Tolerance; D016778:Malaria, Falciparum / Q000150:complications*; D016780:Malaria, Vivax / Q000150:complications* / Q000276:immunology; D013785:Thailand