Abstract
Since 2000, human malaria cases in Malaysia were rapidly reduced with the use of insecticides in Indoor Residual Spray (IRS) and Long-Lasting Insecticide Net (LLIN). Unfortunately, monkey malaria in humans has shown an increase especially in Sabah and Sarawak. The insecticide currently used in IRS is deltamethrin K-Othrine® WG 250 wettable granule, targeting mosquitoes that rest and feed indoor. In Sabah, the primary vector for knowlesi malaria is An. balabacensis a species known to bite outdoor. This study evaluates an alternative method, the Outdoor Residual Spray (ORS) using a novel formulation of deltamethrin K-Othrine® (PolyZone) to examine it suitability to control knowlesi malaria vector in Sabah, compared to the current method. The study was performed at seven villages in Sabah having similar type of houses (wood, bamboo and concrete). Houses were sprayed with deltamethrin K-Othrine® (PolyZone) at two different dosages, 25 mg/m2 and 30 mg/m2 and deltamethrin K-Othrine® WG 250 wettable granule at 25 mg/m2, sprayed indoor and outdoor. Residual activity on different walls was assessed using standard cone bioassay techniques. For larval surveillances, potential breeding sites were surveyed. Larvae were collected and identified, pre and post spraying. Adult survey was done using Human Landing Catch (HLC) performed outdoor and indoor. Detection of malaria parasite in adults was conducted via microscopy and molecular methods. Deltamethrin K-Othrine® (PolyZone) showed higher efficacy when sprayed outdoor. The efficacy was found varied when sprayed on different types of wall surfaces. Deltamethrin K-Othrine® (PolyZone) at 25 mg/m2 was the most effective with regards to ability to high mortality and effective knock down (KD). The vector population was reduced significantly post-spraying and reduction in breeding sites as well. The number of simian malaria infected vector, human and simian malaria transmission were also greatly reduced.
Highlights
Malaria is still one of the tropical diseases that post a great challenge as far as global health is concerned
This study aims to evaluate the effectiveness of new formulation deltamethrin K-Othrine1 (PolyZone) as compared to currently used vector control which applied deltamethrin K-Othrine1 WG 250 wettable granule on different wall surfaces sprayed indoor and outdoor
Since spraying was done by trained and experienced staff of Ministry of Health Malaysia and conducted according to World Health Organization (WHO) guidelines and manufacturer instruction, it was strongly believed that quality of spraying or quality of insecticide required for all houses during 1st spraying and 2nd spraying was satisfactorily achieved and was not considered as factor that could have influence on the result obtained
Summary
Malaria is still one of the tropical diseases that post a great challenge as far as global health is concerned. Despite much government effort to reduce transmission of malaria, cases are still being recorded in rural areas of Sabah and Sarawak [3,4,5] with most of them are knowlesi malaria [6,7]. Cases of knowlesi malaria have been reported throughout Malaysia and the cases are increasing year after year. Deaths due to knowlesi malaria were been reported [3]. In Sabah, the primary vector for knowlesi malaria is An. balabacensis [8]. They are found abundant in rural areas inhabiting the forest and shown to rest and feed outdoor typically after dusk [8,9]. An. balabacensis is an early biter and bites throughout the night, which makes its control using current control strategy challenging
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