Characteristics of malaria transmission in Kataragama, Sri Lanka: a focus for immuno-epidemiological studies.
Parasitological and entomological parameters of malaria transmission were monitored for 17 months in 3,625 residents in a Plasmodium vivax malaria endemic region in southern Sri Lanka; the study area consisted of 7 contiguous villages where routine national malaria control operations were being conducted. Malaria was monitored in every resident; fever patients were screened and 4 periodical mass blood surveys were conducted. An annual malaria incidence rate of 23.1% was reported during the period: 9.3% was due to P. vivax and 13.8% was due to P. falciparum; there had been a recent epidemic of the latter in this region, whereas the P. falciparum incidence rate in the previous 10 years had been negligible. There was a wide seasonal fluctuation in the malaria incidence, with the peak incidence closely following the monsoon rains. The prevalence of malaria due to both species detected at the 4 mass blood surveys ranged from 0.98% (at low transmission) to 2.35% (at peak transmission periods). Adults and children developed acute clinical manifestations of malaria. Entomological measurements confirmed a low degree of endemicity with estimated inoculation rates of 0.0029 and 0.0109 (infectious bites/man/night) for P. vivax and P. falciparum, respectively. Several anopheline species contributed to the transmission, and the overall man biting rates (MBR) showed a marked seasonal variation. Malaria at Kataragama, typical of endemic areas of Sri Lanka, thus presents characteristics of "unstable" transmission. Malaria was clustered in the population. There was a low clinical tolerance to P. falciparum malaria, to which most had only been at risk, compared to P. vivax, to which most had had a life-long exposure.
Malaria Research Unit, University of Colombo, Sri Lanka.
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C
Mendis
A C
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Gamage-Mendis
A P
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De Zoysa
T A
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Abhayawardena
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Carter
P R
PR
Herath
K N
KN
Mendis
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000818:Animals; D000852:Anopheles / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007303:Insect Vectors / Q000502:physiology*; D008288:Malaria / Q000453:epidemiology / Q000276:immunology / Q000635:transmission*; D008297:Male; D008875:Middle Aged; D009032:Mosquito Control; D010963:Plasmodium falciparum / Q000302:isolation & purification; D010966:Plasmodium vivax / Q000302:isolation & purification; D011891:Rain; D012621:Seasons; D012737:Sex Factors; D013188:Sri Lanka / Q000453:epidemiology