Publication: The epidemiology of malaria in a Karen population on the western border of Thailand
Issued Date
1996-01-01
Resource Type
ISSN
00359203
Other identifier(s)
2-s2.0-0029874459
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Mahidol University
Rights Holder(s)
SCOPUS
Bibliographic Citation
Transactions of the Royal Society of Tropical Medicine and Hygiene. Vol.90, No.2 (1996), 105-111
Suggested Citation
C. Luxemburger, Kyaw Lay Thwai, N. J. White, H. K. Webster, D. E. Kyle, L. Maelankirri, T. Chongsuphajaisiddhi, F. Nosten The epidemiology of malaria in a Karen population on the western border of Thailand. Transactions of the Royal Society of Tropical Medicine and Hygiene. Vol.90, No.2 (1996), 105-111. doi:10.1016/S0035-9203(96)90102-9 Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/17645
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Title
The epidemiology of malaria in a Karen population on the western border of Thailand
Abstract
From November 1991 to November 1992 a prospective, descriptive study of malaria epidemiology was conducted in a Karen population on the western border of Thailand. Two study groups were selected at random and more than 80% of the subjects were followed for one year. In Group 1, comprising 249 schoolchildren (aged 4-15 years), daily surveillance for illness was combined with fortnightly malaria surveys. These children experienced 1.5 parasitaemic infections per child-year (95% confidence interval [CI] 1.3-1.7), of which 68% (193/285) were symptomatic (Plasmodium falciparum 84%, P. vivax 57%). The estimated pyrogenic densities were 1460/μL for P. falciparum and 181/μL for P. vivax. In Group 2, comprising subjects of all age from 428 households, malaria was diagnosed during two-monthly surveys, at weekly home visits, and otherwise by passive case detection. Malaria and splenomegaly prevalence rates were low in all age groups (spleen index 2-9%; P. falciparum prevalence rate 1-4%; P. vivax 1-6%). Group 2 subjects had 1.0 infections per person-year (95% CI 0.9-1.1), most of which were symptomatic (312/357; 87%). Malaria infections clustered in households. Overall, P. vivax caused 53% and P. falciparum 37% of the infections (10% were mixed), but whereas P. vivax was most common in young children, with a decline in incidence with increasing age, P. falciparum incidence rates rose with age to a peak incidence between 20 and 29 years, although the risk of developing a severe malaria decreased with increasing age. There was no death from malaria during the study. P. falciparum infections were more common in males, subjects with a history of malaria before the study, and in those who had travelled outside their village. These findings suggest a higher transmission rate for P. vivax than P. falciparum, although adults still suffered symptomatic malaria due to both species. The 2 malaria parasites found in this area contribute approximately 50% of infections each, but their clinical epidemiology is very different.