Responses of the putative trachoma vector, Musca sorbens, to volatile semiochemicals from human faeces

Abstract

The putative vector of trachoma, Musca sorbens, prefers to lay its eggs on human faeces on the ground. This study sought to determine whether M. sorbens females were attracted to volatile odours from human faeces in preference to odours from the faeces of other animals, and to determine whether specific volatile semiochemicals mediate selection of the faeces. Traps baited with the faeces of humans and local domestic animals were used to catch flies at two trachoma-endemic locations in The Gambia and one in Ethiopia. At all locations, traps baited with faeces caught more female M. sorbens than control traps baited with soil, and human faeces was the most successful bait compared with soil (mean rate ratios 44.40, 61.40, 10.50 [P<0.001]; 8.17 for child faeces [P = 0.004]). Odours from human faeces were sampled by air entrainment, then extracts of the volatiles were tested by coupled gas chromatography-electroantennography with laboratory-reared female M. sorbens. Twelve compounds were electrophysiologically active and tentatively identified by coupled mass spectrometry-gas chromatography, these included cresol, indole, 2-methylpropanoic acid, butanoic acid, pentanoic acid and hexanoic acid. It is possible that some of these volatiles govern the strong attraction of M. sorbens flies to human faeces. If so, a synthetic blend of these chemicals, at the correct ratios, may prove to be a highly attractive lure. This could be

Flies as possible vectors of inflammatory trachoma transmission in a Brazilian municipality

“…). The Musca domestica was also the most captured fly in three different regions of Africa in a previous study 16 . However, the transmission of trachoma in Africa is related to M. sorbens, and the presence of C. trachomatis has been demonstrated only in this species 2 , 16 - 18 .…”

“…The Musca domestica was also the most captured fly in three different regions of Africa in a previous study 16 . However, the transmission of trachoma in Africa is related to M. sorbens, and the presence of C. trachomatis has been demonstrated only in this species 2 , 16 - 18 . Generally, the female of M. sorbens is associated with the transmission of trachoma, proliferating in human feces exposed in the environment 4 , 16 .…”

“…The trachoma infection or reinfection depend on the environmental conditions 14 , 15 . The presence of flies is considered an important risk factor for the transmission of trachoma 2 , 16 . Therefore, sanitary conditions and the control of flies are related to the reduction on the prevalence of trachoma 2 , 16 , 17 .…”

“…However, the transmission of trachoma in Africa is related to M. sorbens, and the presence of C. trachomatis has been demonstrated only in this species 2 , 16 - 18 . Generally, the female of M. sorbens is associated with the transmission of trachoma, proliferating in human feces exposed in the environment 4 , 16 . However, M. sorbens does not exist in Brazil 4 , as confirmed in our study.…”

Eliminating Trachoma by 2020: Assessing Progress in Nigeria

“…The end goal of this campaign is to provide access to sanitation, including lavatories with soap, to all Nigerians, especially in rural areas. Studies have shown that access to basic pit latrines lead to a significant reduction in the numbers of eye-seeking flies, correlating with an overall reduction in trachoma [29,30].…”