Utility of passive malaria surveillance in hospitals as a surrogate to community infection transmission dynamics in western Kenya

BACKGROUND: Malaria continued to be the major public health concern in sub-Sahara Africa, thus for better planning of control activities, periodic surveillance of both clinical and asymptomatic cases remains important. However, the usability of routinely collected malaria data in Kenyan hospitals as a predictor of the asymptomatic malaria infection in the community amidst rapid infection resurgence or reduction in different areas of disease endemicities remains widely unstudied. This study was therefore aimed to evaluate the utility of passive surveillance of malaria in health facilities as a proxy of infection transmission of the surrounding community in different transmission intensities. METHODS: Prospective multiple cross-sectional surveys were done in three villages in western Kenya. Monthly asymptomatic malaria positivity among school children, number of outpatient (OPD) confirmed malaria cases and abundancy of indoor resting malaria vectors were surveyed from June 2015 to August 2016. Community surveys on antimalarial drug use among adults and children were also done. Detection of malaria parasitaemia was done using thick and thin Giemsa stained blood slide microscopy for both clinical and school participants. A questionnaire was used to collect information on self-use of antimalarial drugs from randomly selected households. RESULTS: The overall OPD blood slide positivity from all study sites was 26.6% (95%CI 26.2–27.0) and highest being among the 5–14 years (41.2% (95% CI 40.1–42.3). Asymptomatic malaria positivity among the school children were 6.4% (95%CI 5.3–7.5) and 38.3% (95%CI 36.1–40.5) in low and high transmission settings respectively. A strong correlation between overall monthly OPD positivity and the school age children positivity was evident at Marani (low transmission) (rho = 0.78, p = 0.001) and at Iguhu (Moderate transmission) (rho = 0.61, p = 0.02). The high transmission setting (Kombewa) showed no significant correlation (rho = − 0.039, p = 0.89). CONCLUSION: Hospital malaria data from low and moderate malaria transmission predicted the infection transmission dynamics of the surrounding community. In endemic sites, hospital based passive surveillance didn’t predict the asymptomatic infection dynamics in the respective community. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13690-018-0288-y) contains supplementary material, which is available to authorized users.