Anti-mosquito coating on water tanks cuts dengue cases by 45% in Colombian trial

Researchers from the University of Freiburg conducted a cluster-randomized trial in 20 urban neighborhoods of Cúcuta, Colombia, comparing areas where household water tanks were treated with a long-lasting insecticidal coating to untreated control areas. Each neighborhood comprised roughly 1,600 to 2,000 households.

One year after application, neighborhoods with coated tanks recorded 337 dengue cases per 100,000 inhabitants, versus 529 cases per 100,000 in control areas — a 45% greater reduction in incidence. The proportion of homes harboring mosquito larvae or pupae also fell significantly in treated zones.

The coating uses microcapsules that slowly release two active ingredients: one kills adult Aedes aegypti mosquitoes and inhibits egg-laying, while the other prevents larval and pupal development. Laboratory testing showed the coating remains effective for more than 12 months.

Direct costs amounted to approximately US$2 per year per tank. Previous safety assessments indicated that water from treated containers posed no health risk to humans.

Lead author Dr. Rocío Cárdenas noted that large washing tanks are among the most important breeding sites for Aedes aegypti in Colombia. Project leader Prof. Dr. Axel Kröger emphasized that targeting breeding sites with a single annual application can protect many people through a relatively simple measure.

The study, published in The Lancet Infectious Diseases, was described by Prof. Dr. Philipp Henneke as a prime example of the planetary health approach, with a concept developed for a specific region but holding international relevance.

Researchers cautioned that results cannot be directly transferred to Germany, where the Asian tiger mosquito (Aedes albopictus) is spreading. Differences in mosquito species, climate, container types, and control programs limit direct applicability.

However, Kröger suggested a do-it-yourself solution for Europe is conceivable once the coating receives regulatory approval. Current larval control in Germany often requires reapplication of biological agents such as Bti every two weeks, whereas a multi-month coating could reduce the burden on households and authorities.