Responses of Glossina fuscipes fuscipes to visually attractive stationary devices baited with 4-methylguaiacol and certain repellent compounds in waterbuck odour

Abstract

Background A blend of compounds (pentanoic acid, guaiacol, δ-octalactone and geranylacetone) identified in waterbuck ( Kobus defassa ) body odour referred to as waterbuck repellent compounds (WRC) and a synthetic repellent 4-methylguaiacol have previously been shown to repel tsetse flies from the morsitans group. However, these repellents have not been evaluated on palpalis group tsetse flies. In this study, we evaluated the effect of these repellents on catches of Glossina fuscipes fuscipes (major vector of human sleeping sickness) in biconical traps and on sticky small targets which are visually attractive to palpalis group flies. The attractive devices were baited with different doses and blends of the repellent compounds. We also assessed the effect of removal of individual constituents in the synthetic blend of WRC on catches of G . f . fuscipes . Methodology/Principal findings The study was conducted in western Kenya on four islands of Lake Victoria namely Big Chamaunga, Small Chamaunga, Manga and Rusinga. The tsetse fly catches from the treatments were modeled using a negative binomial regression to determine their effect on catches. In the presence of WRC and 4-methylguaiacol (released at ≈2 mg/h and ≈1.4 mg/h respectively), catches of G . f . fuscipes were significantly reduced by 33% ( P <0.001) and 22% ( P <0.001) respectively in biconical traps relative to control. On sticky small targets the reduction in fly catches were approximately 30% ( P <0.001) for both 4-methylguiacol and WRC. In subtractive assays, only removal of geranylacetone from WRC significantly increased catches (by 1.8 times; P <0.001) compared to the complete blend of WRC. Conclusions/Significance We conclude that WRC and 4-methylguaiacol reduce catches of G . f . fuscipes at stationary visually attractive traps and suggest that they may serve as broad spectrum repellents for Glossina species. We recommend further studies to investigate the effects of these compounds on reduction of G . f . fuscipes attracted to human hosts as this may lead to development of new strategies of reducing the prevalence and incidence of sleeping sickness.

Effect of zebra skin-derived compounds on field catches of the human African trypanosomiasis vector Glossina fuscipes fuscipes

“…A four-component repellent blend identified from waterbuck, Kobus ellipsiprymnus defassa (waterbuck repellent compounds, WRC), comprising geranyl acetone, guaiacol, pentanoic acid and -octalactone embedded in repellent collars is currently being used to protect cattle against savannah tsetse flies in some parts of Kenya (Saini et al, 2017). Further field evaluation of the WRC on the riverine tsetse flies G. f. fuscipes, using traps and targets, has shown some promising results for the control of the vectors of the human-infective trypanosomes (Mbewe et al, 2019).…”

Cellular and Molecular Targets of Waterbuck Repellent Blend Odors in Antennae of Glossina fuscipes fuscipes Newstead, 1910

“…The size of the residue ellipse represents the strength of the contact. reduced trap catches by 33% and the different components had a different contribution to spatial repellency of the WRB (Mbewe et al, 2019). Our results show the additional effect of WRB as an antifeedant, besides on its spatial repellency.…”

“…Until recently, the main tools for tsetse control were odor-baited traps and targets (Kuzoe and Schofield, 2004). Additionally, recent use of the tsetse repellent blend (waterbuck repellent blend [WRB]) has reduced the transmission of animal trypanosomiasis in cattle by reducing contact between bloodseeking Glossina pallidipes and cattle hosts (Saini et al, 2017) and has been shown to reduce trap catches of Glossina fuscipes fuscipes (Mbewe et al, 2019). The cellular and molecular mechanisms of the spatial repellent odors are not well understood, yet such knowledge will enable us to improve the efficacy of the existing repellent blend or to identify novel repellents for control of various tsetse fly species of both medical and veterinary importance.…”

Sustainable Elimination (Zero Cases) of Sleeping Sickness: How Far Are We from Achieving This Goal?

“…However, it has only been used for extensive tsetse elimination in Zimbabwe and in the Zambian West Province because of the cost, the logistic requirements, and the need for government commitment [94]. Repellents can also be employed for vector control, for instance, the push-pull control method employs repellents to push the tsetse flies towards stationary visual attractants designed to kill the flies [98]. The repellent mix called waterbuck repellent compounds (WRC) and 4-methylguaiacol which were known Mortisan group tsetse fly repellents were tested for their effects on the Palpalis group and found to effectively repel Glossina fuscipes fuscipes [98].…”

“…Repellents can also be employed for vector control, for instance, the push-pull control method employs repellents to push the tsetse flies towards stationary visual attractants designed to kill the flies [98]. The repellent mix called waterbuck repellent compounds (WRC) and 4-methylguaiacol which were known Mortisan group tsetse fly repellents were tested for their effects on the Palpalis group and found to effectively repel Glossina fuscipes fuscipes [98]. Similarly, unrefined zebra skin odour, as well as a chemical mix with identical odor, was found to significantly repel Glossina pallidipes [99].…”