Towards a fuller understanding of mosquito behaviour: use of electrocuting grids to compare the odour‐orientated responses ofAnopheles arabiensisandAn. quadriannulatusin the field

Abstract

. The epidemiological role of and control options for any mosquito species depend on its degree of ' anthropophily ' . However, the behavioural basis of this term is poorly understood. Accordingly, studies in Zimbabwe quantified the effects of natural odours from cattle and humans, and synthetic components of these odours, on the attraction, entry and landing responses of Anopheles arabiensis Giles (Diptera: Culicidae) and Anopheles quadriannulatus Theobald. The numbers of mosquitoes attracted to human or cattle odour were compared using electrocuting nets (E-nets), and entry responses were gauged by the catch from an odour-baited entry trap (OBET) relative to that from an odour-baited E-net. Landing responses were estimated by comparing the catches from E-nets and cloth targets covered with an electrocuting grid. For An. arabiensis , E-nets baited with odour from a single ox or a single man caught similar numbers, and increasing the dose of human odour from one to three men increased the catch four-fold. For An. quadriannulatus , catches from E-nets increased up to six-fold in the progression: man, three men, ox, and man + ox, with catch being correlated with bait mass. Entry responses of An. arabiensis were stronger with human odour (entry response 62%) than with ox odour (6%) or a mixture of cattle and human odours (15%). For An. quadriannulatus , the entry response was low (< 2%) with both cattle and human odour. Anopheles arabiensis did not exhibit a strong entry response to carbon dioxide (CO 2 ) (0.2 -2 L/min). The trends observed using OBETs and E-nets also applied to mosquitoes approaching and entering a hut. Catches from an electrocuting target baited with either CO 2 or a blend of acetone, 1-octen-3-ol, 4-methylphenol and 3-n-propylphenolcomponents of natural ox odour -showed that virtually all mosquitoes arriving there alighted on it. The propensity of An. arabiensis to enter human habitation seemed to be mediated by odours other than CO 2 alone. Characterizing ' anthropophily ' by comparing the numbers of mosquitoes caught by traps baited with different host odours can lead to spurious conclusions; OBETs baited with human odour caught around two to four times more An. arabiensis than cattle-baited OBETs, whereas a human-baited E-net caught less ( ∼ 0.7) An. arabiensis than a cattle-baited E-net. Similar caution is warranted for other species of mosquito vectors. A fuller understanding of how to exploit mosquito behaviour for control and surveys requires wider approaches and more use of appropriate tools.

Comparative assessment of diverse strategies for malaria vector population control based on measured rates at which mosquitoes utilize targeted resource subsets

“…However, the complexity of these models, and their reliance upon local measurements of several entomological input parameters, all of which have limited precision and accuracy, may well limit broader application of this approach beyond the crude application to existing data presented in Figure  2. Recent attempts to rejuvenate and improve existing entomological survey methodology for detecting resource utilization attempt events with electrified grids [84–86], sticky traps [77, 87], mechanized aspirators [70], and high resolution cameras [75, 76], should enable improved sensitivity of utilization attempt event detection at surveyed samples of resource subset targets. However, while such technical advances may well address the inaccuracies of attempts to estimate utilization rates for subsets of resting sites or other non-nutritional resources by improving event detection sensitivity, they are unlikely to improve their precision because considerable uncertainty arises from the need for relatively complex models (Equations 25a, 25b and 30) that require correspondingly numerous measurements of input parameters.…”

Shoo fly, don't bother me! Efficacy of traditional methods of protecting cattle from tsetse

“…E-targets baited with human odour may serve as models of humans that would allow us to measure the numbers of vectors that are attracted to humans with or without a repellent without exposing the subjects to risk. Electric nets have been shown to be effective against a wide range of vectors, including mosquitoes (Torr et al, 2008), and thus the methods described in this study could be readily applied to studies of mosquito-borne diseases of humans.…”

“…These can range from the ubiquitous bednets and window screens designed specifically to protect against biting insects through to the 'inadvertent' protection provided by being within a house, which many species of mosquito are inhibited from entering (Lindsay et al, 2003;Torr et al, 2008).…”

Microorganism-mediated behaviour of malaria mosquitoes

“…Several other studies have also shown higher attraction of An. arabiensis to human than cow odour Torr et al, 2008;, while other studies show that An.…”

“…gambiae in both field and laboratory studies Pates et al, 2001;Takken & Verhulst, 2013), only a few studies have reported An. arabiensis to be more attracted to human compared to cow odour Torr et al, 2008;Takken & Verhulst, 2013 …”