Comparative Effectiveness of Chemical, Biological or Combination of Both Mosquito Larvicides for Dengue Control in George Town, Penang, Malaysia – A Field Trial

Background: Tackling the increasing trend of the dengue menace remains one of the most challenging tasks in public health medicine. Extensive literature search revealed no previous community intervention trial done in Penang and Malaysia to compare effectiveness of the use of various mosquito larvicides based on container indices as the definitive measurable outcomes. The study aim was to identify the most effective mosquito larvicidal measure for dengue control in dengue-sensitive areas in George Town, Penang.

Methods: A field trial was conducted in three localities randomly selected from a list of 33 dengue-sensitive areas. Area A was treated with both chemical and biological larvicide, Area B was treated with biological larvicide and Area C was treated with chemical larvicide as a standard preventive measure. Container indices (CI) were obtained weekly for eight consecutive weeks and data was analyzed using Repeated Measures ANOVA test in SPSS version 21.

Results: Comparative effectiveness of larvicidal measures between the three areas remained inconclusive as the p-value could not be computed between the three areas due to termination of iteration on ‘between-areas’ factor, although descriptively, better vector control was achieved through monotherapy with biological larvicide alone. Area A’s CI showed a drastic drop from 1.79 to 1.05 for the first two weeks, zero for weeks 3-5, 1.67 at week 6 and reducing to zero for the last two weeks. Area B’s CI showed an initial increase from 1.05 to 1.43 for the first two weeks and subsequently reduced to zero and remained zero until week 8. Area C’s CI showed zero reading for the first two weeks and by week 3, it went up to 1.00 before it reduced to and remained zero until week 8.

Conclusion: Monotherapy with biological larvicide alone seemed to offer better vector control, although statistical evidence of its superiority remained inconclusive. In view of this, integrated vector management should be enhanced by harnessing community participation to curtail dengue infections, irrespective of the choice of larvicide used for vector control.