Cost-effectiveness of the use of vector control and mass drug administration, separately or in combination, against lymphatic filariasis

The costs and effects of two intervention strategies for the control of bancroftian filariasis - annual mass drug administrations (MDA) with a combination of diethylcarbamazine and ivermectin, with or without integrated vector control (VC) - were estimated in rural villages in South India. The aim was to compare the cost-effectiveness of MDA alone with that of MDA plus VC. Control of the local vector, Culex quinquefasciatus, was based on the application of polystyrene beads to cesspits, the treatment of drains with larvicidal Bacillus sphaericus and the stocking of wells with larvivorous fish. An itemized cost menu was used to cost MDA and MDA + VC, retrospectively. The annual transmission potential was used to assess the direct outcome of the disease-control methods, whereas the prevalence and intensity of microfilaraemia were used as indicators of the impact of each method. The per-capita costs were U.S.$1.49 for two rounds of MDA, U.S.$1.70 for 2 years of VC and, therefore, U.S.$3.19 for 2 years of MDA + VC. Integration of VC with MDA did not appear to be cost-effective: it cost an estimated U.S.$1.80 to stop an infective mosquito biting a villager using MDA alone but U.S.$3.32 to achieve the same result using MDA + VC. Similarly, the cost to reduce the prevalence of microfilaraemia in a three-village group by 1% was only U.S.$96.62 for MDA alone but U.S.$201.16 when vector control was integrated. The implications of these results for the control and elimination of filariasis in Indian village communities, and the options for sharing and minimizing costs, are discussed.