Co-infection of long-term carriers of Plasmodium falciparum with Schistosoma haematobium enhances protection from febrile malaria: a prospective cohort study in Mali.

• Published in: PLoS Neglected Tropical Diseases
• Main Authors: Safiatou Doumbo, Tuan M Tran, Jules Sangala, Shanping Li, Didier Doumtabe, Younoussou Kone, Abdrahamane Traoré, Aboudramane Bathily, Nafomon Sogoba, Michel E Coulibaly, Chiung-Yu Huang, Aissata Ongoiba, Kassoum Kayentao, Mouctar Diallo, Zongo Dramane, Thomas B Nutman, Peter D Crompton, Ogobara Doumbo, Boubacar Traore
• Format: Article in Journal/Newspaper
• Language: English
• Published: Public Library of Science (PLoS) 2014
• Subjects: Arctic medicine. Tropical medicine; RC955-962; Public aspects of medicine; RA1-1270; Arctic; Sickle
• Online Access: https://doi.org/10.1371/journal.pntd.0003154; https://doaj.org/article/c0a31546582f47b3a6df36ed2c99ceaa

Malaria and schistosomiasis often overlap in tropical and subtropical countries and impose tremendous disease burdens; however, the extent to which schistosomiasis modifies the risk of febrile malaria remains unclear.We evaluated the effect of baseline S. haematobium mono-infection, baseline P. falciparum mono-infection, and co-infection with both parasites on the risk of febrile malaria in a prospective cohort study of 616 children and adults living in Kalifabougou, Mali. Individuals with S. haematobium were treated with praziquantel within 6 weeks of enrollment. Malaria episodes were detected by weekly physical examination and self-referral for 7 months. The primary outcome was time to first or only malaria episode defined as fever (≥ 37.5 °C) and parasitemia (≥ 2500 asexual parasites/µl). Secondary definitions of malaria using different parasite densities were also explored.After adjusting for age, anemia status, sickle cell trait, distance from home to river, residence within a cluster of high S. haematobium transmission, and housing type, baseline P. falciparum mono-infection (n = 254) and co-infection (n = 39) were significantly associated with protection from febrile malaria by Cox regression (hazard ratios 0.71 and 0.44; P = 0.01 and 0.02; reference group: uninfected at baseline). Baseline S. haematobium mono-infection (n = 23) did not associate with malaria protection in the adjusted analysis, but this may be due to lack of statistical power. Anemia significantly interacted with co-infection (P = 0.009), and the malaria-protective effect of co-infection was strongest in non-anemic individuals. Co-infection was an independent negative predictor of lower parasite density at the first febrile malaria episode.Co-infection with S. haematobium and P. falciparum is significantly associated with reduced risk of febrile malaria in long-term asymptomatic carriers of P. falciparum. Future studies are needed to determine whether co-infection induces immunomodulatory mechanisms that protect against febrile malaria ...