Journal Article

Sand fly synthetic sex-aggregation pheromone co-located with insecticide reduces the incidence of infection in the canine reservoir of visceral leishmaniasis: A stratified cluster randomised trial

Dilger, Erin, Carter, Vicky, Kravar-Garde, Lidija, Alves, Graziella B., Bell, Melissa J., Makhdoomi, Muhammad M., Bray, Daniel P., Hamilton, James G. C., González, Mikel A., Courtenay, Orin, Calvo-Bado, Leo A., Nunes, Caris M., Brazil, Reginaldo P., Goncalves, Raquel

2019

Overview

To evaluate the efficacy of a synthetic sex-aggregation pheromone of the sand fly vector Lu. longipalpis, co-located with residual insecticide, to reduce the infection incidence of Leishmania infantum in the canine reservoir. A stratified cluster randomised trial was designed to detect a 50% reduction in canine incident infection after 24 months in 42 recruited clusters, randomly assigned to one of three intervention arms (14 cluster each): synthetic pheromone + insecticide, insecticide-impregnated dog collars, or placebo control. Infection incidence was measured by seroconversion to anti-Leishmania serum antibody, Leishmania parasite detection and canine tissue parasite loads. Changes in relative Lu. longipalpis abundance within households were measured by setting three CDC light traps per household. A total 1,454 seronegative dogs were followed-up for a median 15.2 (95% C.I.s: 14.6, 16.2) months per cluster. The pheromone + insecticide intervention provided 13% (95% C.I. 0%, 44.0%) protection against anti-Leishmania antibody seroconversion, 52% (95% C.I. 6.2%, 74·9%) against parasite infection, reduced tissue parasite loads by 53% (95% C.I. 5.4%, 76.7%), and reduced household female sand fly abundance by 49% (95% C.I. 8.2%, 71.3%). Variation in the efficacy against seroconversion varied between trial strata. Equivalent protection attributed to the impregnated-collars were 36% (95% C.I. 14.4%, 51.8%), 23% (95% C.I. 0%, 57·5%), 48% (95% C.I. 0%, 73.4%) and 43% (95% C.I. 0%, 67.9%), respectively. Comparison of the two interventions showed no statistically consistent differences in their efficacies; however, the errors were broad for all outcomes. Reductions in sand fly numbers were predominant where insecticide was located (chicken and dog sleeping sites), with no evidence of insecticide-induced repellence onto humans or dogs. The synthetic pheromone co-located with insecticide provides protection particularly against canine L. infantum parasite transmission and sand fly vector abundance. The effect estimates are not dissimilar to those of the insecticide-impregnated collars, which are documented to reduce canine infection incidence, human infection and clinical VL disease incidence, in different global regions. The trialled novel lure-and-kill approach is a low-cost potential vector control tool against ZVL in the Americas.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Abundance / Agglomeration / Aggregation / Aggregation pheromone / Analysis / Animals / Antibodies / Biology and Life Sciences / Brazil / Clusters / Collars / Communicable Disease Control - methods / Disease Reservoirs / Disease transmission / Dog Diseases - epidemiology / Dog Diseases - parasitology / Dog Diseases - prevention & control / Dog Diseases - transmission / Dogs / Entomology / Female / Health aspects / Households / Humans / Incidence / Infection / Infection control / Infections / Insecticides / Insecticides - pharmacology / Leishmania / Leishmania infantum - drug effects / Leishmaniasis / Leishmaniasis, Visceral - epidemiology / Leishmaniasis, Visceral - prevention & control / Leishmaniasis, Visceral - transmission / Leishmaniasis, Visceral - veterinary / Life sciences / Light traps / Loads (forces) / Male / Medicine and Health Sciences / Parasite Load / Parasites / Parasitic diseases / Parasitology / Pest Control - methods / Pheromones / Poultry / Protection / Psychodidae - metabolism / Randomization / Seroconversion / Serum / Sex / Sex Attractants - metabolism / Sex Attractants - pharmacology / Sleep / Surveys and Questionnaires / Tissue / Transmission / Tropical diseases / Vector-borne diseases / Veterinary colleges / Veterinary medicine / Viral antibodies / Visceral leishmaniasis