A Cohort Study on the Duration of Plasmodium falciparum Infections During the Dry Season in The Gambia

Background In areas where Plasmodium falciparum malaria is seasonal, a dry season reservoir of blood-stage infection is essential for initiating transmission during the following wet season. Methods In The Gambia, a cohort of 42 individuals with quantitative polymerase chain reaction-positive P falciparum infections at the end of the transmission season (December) were followed monthly until the end of the dry season (May) to evaluate infection persistence. The influence of human host and parasitological factors was investigated. Results A large proportion of individuals infected at the end of the wet season had detectable infections until the end of the dry season (40.0%; 16 of 40). At the start of the dry season, the majority of these persistent infections (82%) had parasite densities >10 p/mu L compared to only 5.9% of short-lived infections. Persistent infections (59%) were also more likely to be multiclonal than short-lived infections (5.9%) and were associated with individuals having higher levels of P falciparum-specific antibodies (P = .02). Conclusions Asymptomatic persistent infections were multiclonal with higher parasite densities at the beginning of the dry season. Screening and treating asymptomatic infections during the dry season may reduce the human reservoir of malaria responsible for initiating transmission in the wet season. In The Gambia, a cohort of individuals asymptomatically infected with P falciparumwas sampled monthly over the dry season. Higher density multiclonal infections were more likely to persist during the dry season.

Automated summary

In areas with seasonal Plasmodium falciparum malaria, a reservoir of blood-stage infection during the dry season is crucial for initiating transmission in the wet season. A study in The Gambia found that a significant proportion of individuals infected at the end of the wet season continued to have detectable infections until the end of the dry season. These persistent infections were more likely to have higher parasite densities and be multiclonal compared to short-lived infections. Screening and treating asymptomatic infections during the dry season may help reduce the reservoir of malaria responsible for transmission in the wet season.