Effect of large-scale installation of deltamethrin-impregnated screens and curtains in Bam, a major focus of anthroponotic cutaneous leishmaniasis in Iran

Abstract

Installation of deltamethrin-impregnated screens and curtains was assessed as a preventive measure against transmission of anthroponotic cutaneous leishmaniasis (ACL) by Phlebotomus sergenti in Bam, a well-known focus of ACL in Iran with a population of nearly 100,000. This was a quasi-experiment based on official data from an ACL control program in which one section of the city with about one-quarter of the population received the intervention. In the analysis, the rest of the city was used as control. Data covered June 2007 through October 2010. Comparison of cumulative incidence between the intervention and control areas before and after installation indicate a significant differential reduction in the cumulative ACL incidence in the intervention area and a reversal of the relative risk, beginning four months after the completion of installation, from RR = 1.14 (95% CI:1.05-1.23) to RR = 0.84 (95% CI:0.72-0.98). Results also indicate a return to a higher cumulative relative risk, RR = 1.51 (95% CI:1.30-1.77), several months after the loss of the preventive effect. Findings indicate the short-term effectiveness of such preventive measures but highlight the necessity of long-term, sustainable strategies. Results also suggest that shrinkage in the human reservoir pool in response to the intervention may play a significant role in prolongation of the preventive effect beyond the insecticidal life of impregnated materials in foci of anthroponotic cutaneous leishmaniasis and possibly anthroponotic visceral leishmaniasis due to L. donovani.