An improved, multimodal, trap for Triatoma infestans, a kissing bug vector of Chagas disease: laboratory tests

Abstract

Triatomines, commonly known as kissing bugs, are vectors of the protozoan Trypanosoma cruzi, responsible for Chagas disease in the Americas. In South America, Triatoma infestans is one of the main vectors of that disease. Triatomine control programs require practical, economical, and reliable tools and methods to monitor infestation in homes, especially when insects are present at low densities, and detection sensitivity must be improved. In a previous work, a sticky pitfall trap baited with a human-based synthetic odor blend (L(+)lactic acid + valeric acid + ammonia) was developed. That trap captured a significant number of bugs although less than a host-baited trap. In the present work, we added a CO₂ source (a yeast culture) and a heat source (heated paraffin wax) to that odor blend, and tested the resulting multimodal bait in the trap used previously. As the resulting multimodal trap captured as many bugs as a host-baited trap, we also aimed at evaluating the role of the bait constituents in its capture performance. Tests were conducted with two nymphal stages (third and fourth) of T. infestans, within three experimental boxes (containing one trap each) under semi-controlled laboratory conditions, overnight. The percentage of insects captured per trap per treatment was statistically analyzed using a binomial Generalized Linear Mixed Model. The multimodal trap captured as many fourth and third instar nymphs as a trap baited with a mouse (80 % for fourth instar and 57.1 % for third instar nymphs) and more than an unbaited trap (20 % for fourth instar and 14.3 % for third instar nymphs). While the yeast culture plus the odor blend evoked a very good capture performance, (64.3 % for third instar nymphs), the heated paraffin wax appeared to decrease the bait performance when the yeast culture was absent (7.1 % capture for third instar nymphs). Different hypotheses are proposed to explain this. Our results suggest that the addition of the yeast culture to the odor blend was responsible for the improvement of the bait. In summary, we reached a high-performance trap to capture T. infestans nymphs in the laboratory. This trap deserves to be tested in a field setting.