Malaria “hotspots” within a larger hotspot; what’s the role of behavioural factors in fine scale heterogeneity in western Kenya?

Abstract

Background: Malaria remains a major public health problem in Kenya accounting for the highest morbidity and mortality especially among children. Previous reports indicate that infectious agents display heterogeneity in both space and time and malaria is no exception. Heterogeneity has been shown to reduce the effectiveness of interventions. Previous studies have implicated genetic (both human and parasite) and environmental factors as mainly responsible for variation in malaria risk. Human behaviour and its potential risk for contributing to variation in malaria risk has not been extensively explored.

Objective: To determine if there were behavioural differences between the people living in hotspots (high malaria burden) and cold spots (low malaria burden) within a geographically homogeneous and high malaria transmission region.

Design: A prospective closed cohort study.

Setting: The study was conducted in the Health and Demographic Surveillance Site in Bungoma East sub-County.

Subjects: A total of 400 people in randomly selected households in both the fever hotspots and cold spots were tested for malaria at quarterly intervals using malaria rapid diagnostic tests (RDTs).

Results: Significant heterogeneity in malaria incidence and prevalence was observed between villages. Incidence of malaria was significantly higher in the hotspots (high malaria burden areas) compared to the cold spots (low malaria burden) (49 episodes per 1000 person months compared to 26/1000, t test p < 0.001). The incidence also varied significantly among the individual villages by season (P: 0.0071). Knowledge on malaria therapy was significantly  associated with whether one was in the cold spot or hotspot (P: 0.033). Behavioural practices relating to ITN use were significantly associated with region during particular seasons (P: 0.0001 and P: 0.0001 respectively).

Conclusion: There is marked and significant variation in the incidence of malaria among the villages creating actual hotspots of malaria within the larger hotspot. There is a significant difference in malaria infections between the hotspots and cold spots. Knowledge on malaria therapy and behavioural factors such as ITN use may contribute to the observed differences during some seasons.