Development of methods for the control of triatomines, vectors of Chagas disease

FABIO GUIDOBALDI; PABLO G. GUERENSTEIN

Buenos Aires

Encuentro; 3er encuentro internacional sobre enfermedades olvidadas y XV simposio sobre control epidemiológico de enfermedades transmitidas por vectores; 2012

mundo Sano

Introduction. Two of the main vectors of Chagas disease are the triatomines Triatoma infestans and Rhodnius prolixus. Triatomines are adapted to the sylvatic, peri-domestic, and domestic environment. Vector management is currently mainly accomplished by insecticide spraying in the infested houses. However this is not ideal considering that insecticides could affect people living in the sprayed houses, and that particular insecticides are useless after the insect population develops resistance. Vector control is the most effective method to prevent Chagas disease (WHO, 2010). The development of lured trap devices to capture triatomines would constitute a safe and sustainable vector control method. The lures can deliver a physical stimulus (heat, light, humidity), chemical stimulus (host odors, CO2, aggregation pheromone, etc), or a combination of two or more of those stimuli, thus generating a ?multimodal bait? that ideally should result in a synergistic attractive effect between the components. Materials and methods. Using T. infestans and R. prolixus, we carry out experiments in a dual-choice trap olfactometer, which is a very challenging device in which the insects have to be activated, attracted and captured (i.e., let themselves fall into the tubes, and not just approach the odor source like in standard olfactometers) in order to obtain a response to an odor source. We are testing blends of synthetic odors that do not require the use of CO2, a compound that is either expensive or unpractical to use in the field. We also carry out experiments to evaluate other aspects of a potential trap. Our current design is a pit-fall trap. However, we are assessing the advantages of, in addition, using an adhesive surface in the trap-device to capture the bugs that just get close to the bait. The possible disadvantage of such an addition could be the release of the alarm pheromone by the immobilized-stressed insects inside the trap, resulting in trap avoidance and lower capture performance. Results and Discussion. A synthetic blend consisting of L(+)-lactic acid, hexanoic acid and ammonium was assayed using as positive control live mouse odor. Positive control as well the test blend evoked significant activation and attraction (capture) in R. prolixus and T. infestans. Other promising synthetic compounds or blends of odors did not evoke such a response. We propose that blends using the 3 compounds mentioned are strong attractants for triatomines. Nevertheless the blend is less powerful than the live host, so improvements have to be made to maximize the blend performance. The results of our experiments on the attraction/repulsion of insects trapped on adhesives surfaces of a trap will also be presented.   References ·         WHO, 2010. Chagas disease (American trypanosomiasis). Fact sheet N°340. http://www.who.int/mediacentre/factsheets/fs340/en/index.html