Risks associated with dispersive nocturnal flights of sylvatic Triatominae to artificial lights in a model house in the northeastern plains of Colombia

Abstract

Background: Control initiatives and continuous surveillance of vector-borne transmission have proved to be effective measures for diminishing the incidence of Chagas disease in endemic countries. However, the active dispersal of infected sylvatic adult triatomines by flight represents one of the main obstacles to eliminating domestic transmission.

Methods: In order to determine the risk that active dispersal of sylvatic adult triatomines represents in Colombian northeastern plains, we quantified the distribution and abundance of triatomines in palm trees (primarily Attalea butyracea) using live bait traps. Directional light traps were used to estimate the frequency of sylvatic triatomine dispersal and their possible origin. Finally, the effect of environmental parameters and artificial light sources on the take-off of sylvatic Rhodnius prolixus was evaluated in field experiments.

Results: R. prolixus was found in 90 % of the palm trees that densely aggregated toward the northern portion of the study area. R. prolixus, and three other sylvatic triatomine species were found to actively disperse and were attracted to the directional light traps (Triatoma maculata, Panstrongylus geniculatus and Psammolestes arthuri). Temperature, relative humidity, wind speed and night luminosity did not affect the active dispersal of the triatomines which is higher the first two hours after sunset. Artificial lights from houses at 60 and 110 m played a key role in the directionality of the R. prolixus take-offs. Trypanosoma cruzi was isolated from R. prolixus, T. maculata and P. geniculatus and was genotyped as T. cruzi I, III and IV.

Conclusions: Our results highlight the potential risk in Colombian northeastern plains of actively dispersing sylvatic triatomines and their role in the domestic introduction of Discrete Typing Units of T. cruzi associated to sylvatic foci of Chagas disease transmission.

Fig. 1

Study area and abundance of triatomines in palm trees. Map of the location showing with colors the distribution and abundance of sylvatic triatomines in palm trees at Miramar farm in Paz de Ariporo (Casanare-Colombia). Satellite image from Google Maps®

Fig. 2

Light traps and take-off arena used in the field experiments. a. Directional light traps (modified from Sjorgen & Rickman (1966) [27]). b. Experimental cubical tent for take-off experiments (modified from Minoli & Lazzari (2006) [31])

Fig. 3

Source of flying Rhodnius prolixus captured with directional light traps. Histograms with numbers of R. prolixus captured with directional light traps facing to the NW, NE, SW, and SE. White arrow is the mean vector (N = 118 insects, μ = 351.47° and r = 0.269). Satellite image from Google Maps®

Fig. 4

Number of actively dispersing triatomines captured with directional light traps. Histograms with numbers of R. prolixus captured per hour after dusk on the directional light traps facing to the NW, NE, SW, and SE

Fig. 5

Take-off directions of sylvatic Rhodnius prolixus. Histograms with the total numbers of flying R. prolixus under field conditions with lights turned on or off. Mean vectors: with light bulbs turned on and at 60 m μ = 356.88°, r = 0.306 and at 110 m μ = 52.44°, r = 0.358; with light bulbs turned off and at 60 m μ = 101.41°, r = 0.135 and at 110 m μ = 96.72°, r = 0.125. Asterisks indicates directionality to the house (set at 0°) (Hodges-Ajne test, p < p(α)). NS = not significant