The evening crepuscular host-seeking activity of Anopheles mosquitoes in northeast Brazil.

Studies on the timing of anopheline host-seeking are important for understanding mosquito ecology, behaviors, and possible role in disease transmission. To study the evening crepuscular host-seeking activity of anophelines and the effects of moonlight, anopheline mosquitoes were collected with light traps settled in a livestock area in the Brazilian Cerrado region. Traps (Silva traps) were placed next to animal enclosures at 1.5 m asl. The research was divided in 2 experiments: the first experiment (12 nights) comprised 2 trapping periods, one from 6 PM to 7 PM and one from 7 PM to 6 AM, and the second experiment (16 evenings) divided in three 20-min intervals based on the 3 twilight phases (civil: 6-6:20 PM; nautical: 6:20-6:40 PM; and astronomical: 6:40-7 PM). A total of 2,815 anopheline mosquitoes and 9 species were found. The main species were Anopheles triannulatus s.l., An. argyritarsis, An. goeldii, and An. evanse. Host-seeking mosquitoes were more frequently active during the first hour after sunset, with a significant peak in the second 20-min interval. After that, a decrease in the number of individuals was observed from the astronomical twilight onwards. Moonlight did not affect the evening flight activity of anophelines. By using LED-based passive light traps, the evening arrival time of anophelines at blood-feeding sites was demonstrated, and it may be a key time window for malaria vector control interventions.

Effect of ultraviolet LED and trap height on catches of host-seeking anopheline mosquitoes by using a low-cost passive light trap in northeast Brazil.

Light traps have been widely used for monitoring malaria vectors, although drawbacks remain. In this context, new tools and attractants are always becoming available to perform monitoring tasks, like the Silva trap, a passive and low-cost LED-light trap for host-seeking anopheline mosquitoes. In this work, the effectiveness of the Silva trap by using UV-LED and at different heights as well as a comparison with the conventional CDC-type (HP) light trap was studied. A total of 9009 mosquitoes and nine species were caught, Anopheles triannulatus, An. argyritarsis, and An. goeldii being the most frequent species. The green (520 nm) and blue (470 nm) LEDs attracted almost equal numbers of anopheline mosquitoes, but UV LEDs (395 nm) attracted a significantly lower number of individuals (Kruskal-Wallis = 19.68, P = 0.0001). Even with the predominance of mosquitoes trapped at the height of 1.5 m, no significant statistical difference was found among the four heights tested (0.5 m; 1.0 m; 1.5 m; 2.0 m). Green-baited Silva traps collected significantly more individuals than incandescent-baited CDC-type traps (U = 60.5; P = 0.0303). LEDs have been useful as light sources for attracting insect vectors and together with a low-cost trap, as the Silva trap, a feasible alternative to conventional trap-based monitoring Anopheles mosquitoes that can be implemented in the field.

Field performance of a low cost, simple-to-build, non-motorized light-emitting diode (LED) trap for capturing adult Anopheles mosquitoes (Diptera: Culicidae).

In this paper, a non-powered trap equipped with light-emitting diodes (LEDs) designed for capturing small night-flying insects was field-evaluated for sampling anopheline mosquitoes. This new light trap, referred to as the Silva trap, was compared with the Centers for Disease Control and Prevention (CDC) miniature light trap in a livestock area in northeastern Brazil. Light traps were operated from 18:00 to 06:00 between July and August 2018, over a 12-night period. A total of 3124 specimens and eight species were collected. Anopheles (Nyssorhynchus) argyritarsis was the prevalent species, followed by A. (Nys) triannulatus s.l., A. (Nys) goeldii, A. (Nys) evansae, A. (Nys) rangeli, A. (Nys) galvaoi, A. (Nys) darlingi and A. (Nys) albitarsis s.l. The total number of anopheline mosquitoes captured with the Silva trap was higher than the number of individuals captured with the CDC light trap, but no significant difference between the two trapping methods was found. Concerning the damaged specimens, the Silva trap damaged significantly less mosquitoes than the CDC light trap. According to these results, the Silva trap has acceptable performance in being an efficient tool for sampling anopheline mosquitoes, mainly in comparison with the CDC light trap. The Silva trap has a number of advantages over other trapping devices that collect questing mosquitoes and these advantages are pointed out and discussed.