Malaria transmission at a new irrigation project in Sri Lanka: the emergence of Anopheles annularis as a major vector
Ramasamy, R.; De Alwis, R.; Wijesundere, A.; Ramasamy, M.S.
American Journal of Tropical Medicine and Hygiene 47(5): 547-553
1992
ISSN/ISBN: 0002-9637 PMID: 1449195 Document Number: 399693
Malaria transmission was studied in a newly irrigated area (Weheragala) of the Mahaweli project in the dry zone of Sri Lanka. Observations were performed for a 3-month period following the northeast monsoon in 1990. Parasitaemia in the population varied from 20.2% in February to 7% in May, and infection was due to both Plasmodium falciparum and P. vivax. Night catches of mosquitoes collected with human bait in March, April and June included a high proportion of A. annularis. Mosquitoes containing sporozoites in the salivary glands were identified by an ELISA. A. culicifacies, A. annularis, and A. aconitus were all implicated as vectors in the area. The highest entomological inoculation rate, 0.12 infected bites/h, was observed with A. annularis and P. vivax in March. Only P. vivax infections were seen in A. annularis and A. aconitus (a single specimen seen in March). It is suggested that a change in the ecosystem from dry zone forest to irrigated cultivated land is the cause of the increased prevalence of A. annularis in this area and its emergence as a major vector of malaria.