Malaria vectors in a traditional dry zone village in Sri Lanka.

Malaria transmission by anopheline mosquitoes was studied in a traditional tank-irrigation-based rice-producing village in the malaria-endemic low country dry zone of northcentral Sri Lanka during the period August 1994-February 1997. Adult mosquitoes were collected from human and bovid bait catches, bovid-baited trap huts, indoor catches, and pit traps. Mosquito head-thoraces were tested for the presence of Plasmodium falciparum and P. vivax, and blood-engorged abdomens for the presence of human blood by ELISAs. House surveys were done at two-day intervals to record cases of blood film-confirmed malaria among the villagers. A total of 7,823 female anophelines representing 14 species were collected. Trends in anopheline abundance were significantly correlated with rainfall of the preceding month in An. annularis, An. barbirostris, An. subpictus, An. vagus, and An. varuna, but were not significant in An. culicifacies and An. peditaeniatus. Malaria parasite infections were seen in seven mosquito species, with 75% of the positive mosquitoes containing P. falciparum and 25% P. vivax. Polymorph PV247 was recorded from a vector (i.e., An. varuna) for the first time in Sri Lanka. Computations of mean number of infective vector (MIV) rates using abundance, circumsporozoite (CS) protein rate, and human blood index (HBI) showed the highest rate in An. culicifacies. A malaria outbreak occurred from October 1994 to January 1995 in which 45.5% of village residents experienced at least a single disease episode. Thereafter, malaria incidence remained low. Anopheles culicifacies abundance lagged by one month correlated positively with monthly malaria incidence during the outbreak period, and although this species ranked fifth in terms of abundance, infection was associated with a high MIV rate due to a high CS protein rate and HBI. Abundance trends in other species did not correlate significantly with malaria. It was concluded that An. culicifacies was epidemiologically the most important vector in the study area.

Anopheline (Diptera:Culicidae) breeding in a traditional tank-based village ecosystem in north central Sri Lanka.

A 13-mo survey of immature anopheline mosquitoes breeding in surface water habitats was done at Mahameegaswewa village within the Huruluwewa watershed in north central Sri Lanka as part of a multidisciplinary study on malaria epidemiology. The watershed is representative of the ancient small tank-based irrigation network that still forms an important component of the rice production system in the low elevation dry zone. In total, 3,818 immatures representing 12 species were obtained from 2,940 samples taken from 5 larval habitats within the village ecosystem. Anopheles varuna Iyengar and An. culicifacies Giles were the most abundant species collected. Peak abundance in both species occurred in August-October. Anopheles barbirostris Van der Wulp and An. peditaeniatus Leicester also were abundant, but neither these nor the other anophelines attained comparable abundance to An. varuna and An. culicifacies. A clear progression in breeding habitat use from stream bed to tank bed and drainage area pools was seen in An. culicifacies during the premonsoon period. Environmental management measures to reduce or modify these habitats could potentially decrease malaria. transmission.

Household responses to malaria and their costs: a study from rural Sri Lanka.

A study of the cost of malaria at the household level, community perceptions, preventive measures and illness behaviour linked to the disease was undertaken in 5 villages in the dry zone of Sri Lanka. The surveyed community had a high knowledge of malaria, although side effects of antimalarial drugs were often confused with symptoms of the disease. The community sought prompt diagnosis and treatment at 'western-type' facilities, with 84% making use of government facilities as their first choice and 16% preferring private facilities. The preventive measures used were burning coils (54% of families) and special leaves (69% of families), and 93% of the families had their houses sprayed with insecticides. Average direct expenditure on a single malaria episode was $3 US, with some families spending more than 10% of the annual household net income per episode. The highest expenditure was on special diets for the sick person, to neutralize the perceived heating effect of the disease and its treatment.

PIP: Knowledge of community perceptions of malaria, treatment-seeking behaviors, and the household costs of illness is essential to the planning of sustainable malaria control interventions. These factors were investigated in household surveys conducted in 5 villages in Sri Lanka's dry zone in February 1995. 95% of the 216 families interviewed regarded malaria as their main health problem, followed by diarrhea and eye diseases. Malaria was ranked as the third most important community concern, following lack of water for cultivation and poverty. Overall knowledge of malaria's causes, symptoms, and treatment was high, although the side effects of antimalarial drugs were often confused with symptoms of the disease. Reported for the 3-month period preceding the survey were 178 episodes of malaria involving 160 families. Home treatment with paracetamol was the first step taken in 85% of cases; however, all families sought prompt treatment from Western-type facilities, especially government hospitals (48%) and mobile clinics (30%). No families consulted indigenous or ayurvedic physicians, despite their availability in the area. This utilization of prompt, effective treatment is presumed to reflect high knowledge about malaria, the perceived seriousness of the disease, and good transport facilities in the area. The total direct expenditure on a single episode of malaria averaged US $3; the median net annual income was $258. Special foods for malaria patients aimed at neutralizing the perceived heating effect of malaria and antimalarial drugs (e.g., sodas, oranges) were the most costly item. Adults lost an average of 7.8 days of work per episode and those accompanying them to health facilities lost 2.9 days. Preventive measures used by families included bed nets (23%), mosquito coils (54%), and insecticides (93%).