Malaria Parasitemia Among Febrile Patients Seeking Clinical Care at an Outpatient Health Facility in an Urban Informal Settlement Area in Nairobi, Kenya.

Henry N Njuguna,Newton Wamola,Robert F Breiman,Leonard Cosmas,Meghna Desai,Joseph O Oundo,Ann M Buff,Joel M Montgomery

doi:10.4269/ajtmh.15-0293

Abstract

Nairobi is considered a low-risk area for malaria transmission, but travel can influence transmission of malaria. We investigated the demographic characteristics and travel history of patients with documented fever and malaria in a study clinic in a population-based surveillance system over a 5-year period, January 1, 2007 to December 31, 2011. During the study period, 11,480 (68%) febrile patients had a microscopy test performed for malaria, of which 2,553 (22%) were positive. Malaria was detected year-round with peaks in January, May, and September. Children aged 5–14 years had the highest proportion (28%) of positive results followed by children aged 1–4 years (23%). Almost two-thirds of patients with malaria reported traveling outside Nairobi; 79% of these traveled to three counties in western Kenya. History of recent travel (i.e., in past month) was associated with malaria parasitemia (odds ratio: 10.0, 95% confidence interval: 9.0–11.0). Malaria parasitemia was frequently observed among febrile patients at a health facility in the urban slum of Kibera, Nairobi. The majority of patients had traveled to western Kenya. However, 34% reported no travel history, which raises the possibility of local malaria transmission in this densely populated, urban setting. These findings have important implications for malaria control in large Nairobi settlements.

Highlights

We describe the demographic features of febrile patients with malaria parasitemia, identify the geographical regions to which they frequently traveled, and assess the seasonal patterns of malaria infection among patients seeking care at an outpatient clinic in the Kibera slum in Nairobi, Kenya, from 2007 to 2011
68% (N = 11,480) had a blood slide processed for malaria microscopy
Our study demonstrates that malaria parasitemia is relatively common in febrile patients in Kibera, Nairobi, both with and without a recent history of travel

Summary

Introduction

Kenya has four eco-epidemiological malaria zones: endemic Lake Victoria and coastal counties; epidemic-prone highland counties; seasonal transmission counties; and counties with no-to-very-low transmission risk, including Nairobi County, primarily due to high altitude and low seasonal temperatures.[4,5] Among children < 15 years of age, malaria parasite prevalence varies across the eco-epidemiological zones from a high of 38% in the lake-endemic counties to a low of ≤ 1% in low-risk counties.[5] Efforts to reduce the burden of malaria through the four main prevention and control strategies have focused primarily on areas with high malaria prevalence.[4,6]. Rural populations migrate in search of economic opportunity, which has resulted in more people living in crowded, informal settlements (i.e., slums). An estimated 1.9 million people or 60% of the total population of Nairobi lives in informal settlements.[9] Unlike many developing countries, Kenya has a relatively well-developed transportation infrastructure that facilitates frequent travel of workers and families from Nairobi to their rural homes

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Conclusion