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. 2005 Oct;11(10):1571-7.
doi: 10.3201/eid1110.050106.

Plasmodium falciparum spatial analysis, western Kenya highlands

Otsyula G Munyekenye  1 , Andrew K Githeko, Guofa Zhou, Emmanuel Mushinzimana, Noboru Minakawa, Guiyun Yan
Affiliations

Plasmodium falciparum spatial analysis, western Kenya highlands

Otsyula G Munyekenye et al. Emerg Infect Dis. 2005 Oct.

Abstract

We carried out a population-based study to determine the unbiased, age-specific Plasmodium falciparum prevalence, asexual and sexual parasite density, and spatial distribution to establish rates of infection at a site in western Kenya. Three cross-sectional surveys were carried out in western Kenya highlands. Blood samples were taken from 1,388 persons from 6 months to 75 years of age. Parasite prevalence and densities in the population decreased with age and distance from valley bottoms. Children from 1 to 4 years of age had the highest parasite prevalence (38.8%-62.8%); in adults, prevalence declined to 2.9%-24.1%. Malaria prevalence declined by an average of 19% from July to December 2002 across age groups. These observations suggest that parasite transmission is intense at this altitude. Asexual parasite density indicated clustering near major vector breeding habitats. Variability in seasonal prevalence indicates transmission instability and susceptibility to epidemics.

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Figures

Figure 1
Figure 1
Distribution of residents sampled for Plasmodium prevalence, Iguhu village, Kakamega district, western Kenya.
Figure 2
Figure 2
A) Plasmodium falciparum trophozoite prevalence. B) Geometric mean of P. falciparum–infected erythrocytes per microliter of blood (error bars represent 95% confidence intervals), Iguhu village, Kakamega district, western Kenya.
Figure 3
Figure 3
A) Plasmodium falciparum gametocyte prevalence. B) Infection densities in different age groups, Iguhu village, Kakamega district, western Kenya.
Figure 4
Figure 4
Dynamics of monthly rainfall, monthly (geometric) mean parasite density, and monthly Plasmodium falciparum prevalence.
Figure 5
Figure 5
Results of weighted K function analysis on the global spatial clustering of Plasmodium falciparum infection intensities in Iguhu for age groups A) 0–9 years, B) 10–19 years, and C) >19 years in the July 2002 survey. The solid line is the observed value of the test statistic L(d) at a given distance d, and dashed lines indicate 95% confidence intervals.
Figure 6
Figure 6
Significant clustering of Plasmodium falciparum infection intensities in Iguhu village for children 0–9 years of age.
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