Abstract
BG-Malaria (BGM) trap is a simple adaptation of the widely-used BG-Sentinel trap (BGS). It is proven to be highly effective for trapping the Brazilian malaria vector, Anopheles darlingi, in field conditions, and the African vector, Anopheles arabiensis, under controlled semi-field environments, but has not been field-tested in Africa. Here, we validated the BGM for field sampling of malaria vectors in south-eastern Tanzania. Using a series of Latin-Square experiments conducted nightly (6pm-7am) in rural villages, we compared mosquito catches between BGM, BGS and human landing catches (HLC). We also compared BGMs baited with different attractants (Ifakara-blend, Mbita-blend, BG-Lure and CO2). Lastly, we tested BGMs baited with Ifakara-blend from three odour-dispensing methods (BG-Cartridge, BG-Sachet and Nylon strips). One-tenth of the field-collected female Anopheles gambiae s.l. and Anopheles funestus were dissected to assess parity. BGM captured more An. gambiae s.l. than BGS (p < 0.001), but HLC caught more than either trap (p < 0.001). However, BGM captured more An. funestus than HLC. Proportions of parous An. gambiae s.l. and An. funestus consistently exceeded 50%, with no significant difference between methods. While the dominant species caught by HLC was An. gambiae s.l. (56.0%), followed by Culex spp. (33.1%) and Mansonia spp. (6.0%), the BGM caught mostly Culex (81.6%), followed by An. gambiae s.l. (10.6%) and Mansonia (5.8%). The attractant-baited BGMs were all significantly superior to un-baited controls (p < 0.001), although no difference was found between the specific attractants. The BG-Sachet was the most efficient dispenser for capturing An. gambiae s.l. (14.5(2.75–42.50) mosquitoes/trap/night), followed by BG-Cartridge (7.5(1.75–26.25)). The BGM caught more mosquitoes than BGS in field-settings, but sampled similar species diversity and physiological states as BGS. The physiological states of malaria vectors caught in BGM and BGS were similar to those naturally attempting to bite humans (HLC). The BGM was most efficient when baited with Ifakara blend, dispensed from BG-Sachet. We conclude that though BGM traps have potential for field-sampling of host-seeking African malaria vectors with representative physiological states, both BGM and BGS predominantly caught more culicines than Anopheles, compared to HLC, which caught mostly An. gambiae s.l.
Highlights
Between 2010 and 2015, there have been declines of more than 50% in malaria cases worldwide [1]
As malaria vectors were the prime focus of interest in this study, further analyses was done on An. gambiae s.l. and An. funestus mosquitoes
BG-Malaria trap (BGM) and BG-Sentinel trap (BGS) captured similar numbers of An. funestus compared to human landing catches (HLC) (RR = 1.2, 95%Confidence Intervals (CI): (0.62–2.32), p = 0.587) and (RR = 0.71 (0.36–1.39, p = 0.314), respectively
Summary
Between 2010 and 2015, there have been declines of more than 50% in malaria cases worldwide [1]. The World Health Organization (WHO) estimates that since 2016 the number of malaria cases is increasing again [1] and in many low and middle-income endemic areas, such as different regions of Africa, Asia and South America, malaria and other mosquitoborne illnesses still remain major public health challenges [1, 3, 4]. Difficult to achieve, such tools should be effective in different areas, so that the data obtained can be compared across regions. For these tools to be considered representative, they should capture similar species diversities and physiological states of mosquitoes as those that would normally bite humans
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