TY - JOUR
T1 - High prevalence of asymptomatic Plasmodium falciparum Infections in a highland area of western Kenya
T2 - A cohort study
AU - Baliraine, Frederick N.
AU - Afrane, Yaw A.
AU - Amenya, Dolphine A.
AU - Bonizzoni, Mariangela
AU - Menge, David M.
AU - Zhou, Goufa
AU - Zhong, Daibin
AU - Vardo-Zalik, Anne M.
AU - Githeko, Andrew K.
AU - Yan, Guiyun
N1 - Funding Information:
Received 21 October 2008; accepted 26 January 2009; electronically published 28 May 2009. Potential conflicts of interest: none reported. Financial support: National Institutes of Health (grants R01 AI050243, D43 TW001505, and R03 TW007360). Reprints or correspondence: Dr. Frederick N. Baliraine, Program in Public Health, College of Health Sciences, University of California at Irvine, 3501B Hewitt Hall, Irvine, CA 92697 ([email protected]; [email protected]).
PY - 2009/7/1
Y1 - 2009/7/1
N2 - Background. Transmission of malaria in an area of hypoendemicity in the highlands of western Kenya is not expected to lead to rapid acquisition of immunity to malaria. However, the subpopulation of individuals with asymptomatic Plasmodium falciparum infection may play a significant role as an infection reservoir and should be considered in malaria-control programs. Determination of the spatiotemporal dynamics of asymptomatic subpopulations provides an opportunity to estimate the epidemiological importance of this group to malaria transmission. Methods. Monthly parasitological surveys were undertaken for a cohort of 246 schoolchildren over 12 months. The prevalence of P. falciparum infection among 2611 blood samples was analyzed by both microscopy and polymerase chain reaction, and infection durations were determined. Results. Infection prevalence and duration (range, 1-12 months) decreased with age and altitude. The prevalence was high among pooled blood samples recovered from children aged 5-9 years (34.4%) and from those aged 10-14 years (34.1%) but was significantly lower among blood samples obtained from older children (9.1%). The prevalence decreased from 52.4% among pooled blood samples from children living at an altitude of ∼1430 m to 23.3% among pooled samples from children living at an altitude of 1580 m. Conclusions. The prevalence of asymptomatic P falciparum infection was high, with polymerase chain reaction analysis detecting a significantly greater number of infections, compared with microscopy. Our results are consistent with gradual acquisition of immunity with increasing age upon repeated infection, and they also show that the risk of malaria transmission is highly heterogeneous in the highland area. The results provide strong support for targeted malaria-control interventions.
AB - Background. Transmission of malaria in an area of hypoendemicity in the highlands of western Kenya is not expected to lead to rapid acquisition of immunity to malaria. However, the subpopulation of individuals with asymptomatic Plasmodium falciparum infection may play a significant role as an infection reservoir and should be considered in malaria-control programs. Determination of the spatiotemporal dynamics of asymptomatic subpopulations provides an opportunity to estimate the epidemiological importance of this group to malaria transmission. Methods. Monthly parasitological surveys were undertaken for a cohort of 246 schoolchildren over 12 months. The prevalence of P. falciparum infection among 2611 blood samples was analyzed by both microscopy and polymerase chain reaction, and infection durations were determined. Results. Infection prevalence and duration (range, 1-12 months) decreased with age and altitude. The prevalence was high among pooled blood samples recovered from children aged 5-9 years (34.4%) and from those aged 10-14 years (34.1%) but was significantly lower among blood samples obtained from older children (9.1%). The prevalence decreased from 52.4% among pooled blood samples from children living at an altitude of ∼1430 m to 23.3% among pooled samples from children living at an altitude of 1580 m. Conclusions. The prevalence of asymptomatic P falciparum infection was high, with polymerase chain reaction analysis detecting a significantly greater number of infections, compared with microscopy. Our results are consistent with gradual acquisition of immunity with increasing age upon repeated infection, and they also show that the risk of malaria transmission is highly heterogeneous in the highland area. The results provide strong support for targeted malaria-control interventions.
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U2 - 10.1086/599317
DO - 10.1086/599317
M3 - Article
C2 - 19476434
AN - SCOPUS:67650667774
SN - 0022-1899
VL - 200
SP - 66
EP - 74
JO - Journal of Infectious Diseases
JF - Journal of Infectious Diseases
IS - 1
ER -