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

• Main Authors: Safiatou Doumbo (Author), Tuan M Tran (Author), Jules Sangala (Author), Shanping Li (Author), Didier Doumtabe (Author), Younoussou Kone (Author), Abdrahamane Traoré (Author), Aboudramane Bathily (Author), Nafomon Sogoba (Author), Michel E Coulibaly (Author), Chiung-Yu Huang (Author), Aissata Ongoiba (Author), Kassoum Kayentao (Author), Mouctar Diallo (Author), Zongo Dramane (Author), Thomas B Nutman (Author), Peter D Crompton (Author), Ogobara Doumbo (Author), Boubacar Traore (Author)
• Format: Book
• Published: Public Library of Science (PLoS), 2014-09-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 1935-2727; 1935-2735; 10.1371/journal.pntd.0003154
• Keywords: Arctic medicine. Tropical medicine; RC955-962; Public aspects of medicine; RA1-1270
• Source: PLoS Neglected Tropical Diseases, Vol 8, Iss 9, p e3154 (2014)

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 or whether genetic, behavioral, or environmental factors not accounted for here explain these findings.