Predictors of malaria-association with rubber plantations in Thailand

BACKGROUND The national Global Fund-supported malaria (GFM) program in Thailand, which focuses on the household-level implementation of vector control via insecticide-treated nets (ITNs)/long-lasting insecticidal nets (LLINs) combined with indoor residual spraying (IRS), has been combating malaria risk situations in different provinces with complex epidemiological settings. By using the perception of malaria villagers (MVs), defined as villagers who recognized malaria burden and had local understanding of mosquitoes, malaria, and ITNs/LLINs and practiced preventive measures, this study investigated the predictors for malaria that are associated with rubber plantations in an area of high household-level implementation coverage of IRS (2007-2010) and ITNs/LLINs (2008-2010) in Prachuap Khiri Khan Province. METHODS A structured questionnaire addressing socio-demographics, household characteristics and health behavioral factors (knowledge, perceptions and practices) regarding the performed interventions was administered to the 313 households (70 malaria-affected and 243 malaria-unaffected) that had respondents aged ≥18 years of both genders. In the univariate and multivariate analyses, only 246 (78.6%) MV respondents (62 malaria-affected and 184 malaria-unaffected) were analyzed to determine the predictors for risk (morbidity). RESULTS The majority (70%) of households were covered by IRS. For a combination of ITNs/LLINs, there were 74% of malaria-affected households covered and 46% of malaria-unaffected households. In a logistic regression analysis using odds ratios (aORs) adjusted on the variables and a 95% confidence interval (CI), malaria affecting MVs was associated with daily worker (i.e., earning daily income by normally practicing laborious activities mostly in agriculture such as rubber tapping and rubber sheet processing at the smallholdings of rubber plantations) (aOR = 2.9, 95% CI: 1.1-7.4), low-moderate level of malaria knowledge (aOR = 2.4, 95% CI: 1.1-5.0) and sleeping under mosquito-nets (nets/ITNs/LLINs intermittently and ITNs/LLINs only) (aOR = 2.0, 95% CI: 1.0-3.7). CONCLUSIONS The MV predictors for malaria-association with rubber plantations included occupation (daily worker), misconceptions about malaria (mosquito and prevention) and the use of mosquito-nets. Human practices such as revisiting rubber plantations while exposed to multiple bites at multiple locations are more likely to apply to daily workers than to rubber farmers/tappers and others. The promotion and use of ITNs/LLINs depends substantially on cultural factors and defensive behaviors relevant to their occupational risk despite the perceived threats of malaria and the perceived benefits of ITNs/LLINs. This information supports the conclusion that GFM program implementation in Thailand or elsewhere for malaria-associated with rubber plantations would benefit from the potential use of ITNs/LLINs and changes in personal protection behaviors.