Cost-effectiveness and sustainability of lambdacyhalothrin-treated mosquito nets in comparison to DDT spraying for malaria control in western Thailand.

The cost-effectiveness of lambdacyhalothrin-treated nets in comparison with conventional DDT spraying for malaria control among migrant populations was evaluated in a malaria hyperendemic area along the Thai-Myanmar border. Ten hamlets of 243 houses with 948 inhabitants were given only treated nets. Twelve hamlets of 294 houses and 1,315 population were in the DDT area, and another 6 hamlets with 171 houses and 695 inhabitants were in the non-DDT-treated area. The impregnated net program was most cost-effective (US$1.54 per 1 case of prevented malaria). Spraying with DDT was more cost-effective than malaria surveillance alone ($1.87 versus $2.50 per 1 case of prevented malaria). These data suggest that personal protection measures with insecticide-impregnated mosquito net are justified in their use to control malaria in highly malaria-endemic areas in western Thailand.

Cost and performance of malaria sector: a case study at Malaria Sector 11, Tak Province, Thailand.

The objective of this study was to assess the cost and performance of each operational unit at the malaria sector level and to calculate the unit cost of each activity accordingly. Data were collected at Malaria Sector No.11 situated at the western border of Thailand with Myanmar during the fiscal year of 1995. The unit cost was calculated by dividing the total cost of each activity by its output using appropriate units of analysis. The result showed that 67% of the total cost of malaria sector was labor cost and 45% of the total cost was allocated to diagnosis and treatment activities. Unit cost in terms of cost/visit, cost/case found, cost/case of falciparum malaria treated, cost/case of vivax malaria treated, cost/house spray and cost/impregnated net were US$1.85, 8.21, 10.07, 8.46, 2.24 and 1.54 respectively. The results of this study will provide important information as to the best use of limited available resources to determine which activities should be stopped, continued, increased or decreased at the malaria sector level.

Cost-effectiveness analysis of lambdacyhalothrin-treated nets for malaria control: the patients' perspective.

The present study was undertaken to evaluate the cost-effectiveness of lambdacyhalothrin-treated nets in comparison with conventional DDT-spraying as a method of malaria control according to the patients' perspective among migrant populations in a high-risk area along the Thai-Myanmar border in Thailand. Ten hamlets comprising 243 houses with 948 inhabitants were given only treated nets. Twelve hamlets comprising 294 houses and 1,315 inhabitants represented the DDT-treated area and another six hamlets with 171 houses and 695 inhabitants served as controls. Information as to consumer costs was obtained by interviewing 3,214 patients seeking care at all levels of the health care system in the study area. Analysis showed that the impregnated-net program was more cost-effective than the DDT-spraying program or surveillance alone (US$ 0.59 vs US$ 0.74 vs US$ 0.79 per 1 case of prevented malaria). We conclude that in a high-risk area such as along the Thai-Myanmar border in western Thailand, integrating the use of impregnated nets with large-scale primary health care programs is likely to constitute the most cost-effective method for controlling malaria according to the patients' perspective.

The effect of pyrethroid impregnated mosquito nets on field malaria vector populations in experimental huts and in individual local houses.

Studies were carried out in Tak Province, northwest Thailand to determine repellency and killing effects of four commercially available pyrethroids etofenprox, deltamethrin, lambdacyhalothrin and permethrin treated mosquito nets on field malaria vector populations in experimental huts and local houses. The studies reveal that all four test pyrethroids have a highly repellency effect. Repellency ratio between lifted and torn nets also showed some different among the four pyrethroids. Mosquito net treated with 0.3 g/m2 permethrin was most toxic to mosquito followed by 0.02 g/m2 deltamathrin, etofenprox 0.3 g/m2 and 0.02 g/m2 lambdacyhalothrin. However, careful consideration for future use should also include problem of cross-resistance, persistence of chemicals and also type of mosquito net material.

Practical uses of acridine orange fluorescence microscopy of centrifuged blood (QBC Malaria Test) and the QBCII Hematology System in patients attending malaria clinics in Thailand.

We evaluated the detection of malaria parasites using acridine orange fluorescence microscopy of centrifuged blood (AOFM/CB or "QBC Malaria Test") at two government malaria clinics in rural Thailand. In a subgroup of the patients, a QBC Hematology System for the determination of complete blood counts was also utilized. A Giemsa-stained thick smear (GTS) reading of 100 (1,000x) microscopic fields was used as standard. The AOFM/CB sensitivities were 97% overall and 95% for P. falciparum (Pf). Sensitivity was lower for P. vivax (Pv) (76%). Pv sensitivity depended largely on ameboid form density. A threshold for AOFM/CB to consistently detect Pv ameboid forms was estimated to be 10/100 WBC (700/microliters blood). AOFM/CB was capable of detecting Pf gametocytes and schizonts more frequently than GTS. The total Pf rings per microliter blood estimated from GTS was highly correlated with the number of Pf rings per Paralens microscopic field (PMF) suggesting that AOFM/CB could be used quantitatively. From a technical standpoint, the rural tropical settings of Thailand in this study were not an obstacle to the use of QBC Hematology. The system was found to be useful in conjunction with AOFM/CB. However, in patients heavily infected with Pf gametocytes of Pv ameboid forms, their total WBC and lymphocyte counts needed to be appropriately corrected. Overall, AOFM/CB appears to be a promising tool for field diagnosis of malaria if it is affordable to developing countries.

Acridine orange fluorescent microscopy and the detection of malaria in populations with low-density parasitemia.

Detection of low-density malaria parasites with Giemsa-stained thick smears (G-TS) requires time and experience and becomes impractical with high sample loads. Acridine orange fluorescent microscopy (AO/FM) of capillary centrifuged blood may offer an alternative technique. We compared AO/FM readings with G-TS in 290 specimens from asymptomatic people in Thai villages endemic for malaria. AO/FM specimens were prepared in modified capillary tubes coated with acridine orange (Quantitative Buffy Coat or "QBC tubes") and examined under a fluorescent microscope. Twenty-three (85.2%) of the 27 specimens found positive by G-TS had under 100 parasites/microliters blood (less than 35 parasites/200 microscopic fields). The overall AO/FM sensitivity was 78.9% [range: 66.7% (10/15)-86.7% (13/15)]. For Plasmodium falciparum, regardless of stages, the sensitivities varied from 66.7% (8/12) to 91.7% (11/12). AO/FM performed better for P. falciparum than for Plasmodium vivax and for asexual than for sexual stages of the parasite. However, the species- and stage-specific results must be interpreted with caution because of the small sample sizes and very low parasite densities involved. The test specificity was 96.6% [range: 95.6% (263/275)-97.1% (263/271)]. These levels of accuracy plus the known advantages of AO/FM suggest that the test, supplemented with G-TS to improve species and stage differentiation, is also useful for screening low-density parasitemias.