For the first time, scientists have shown that malaria-transmitting mosquitoes actively avoid feeding on certain animal species such as chickens, using their sense of smell. Odours emitted by species such as chickens could provide protection for humans at risk of mosquito-transmitted diseases, according to a study in Malaria Journal.
Researchers found that Anopheles arabiensis, one of the predominant species transmitting malaria in sub-Saharan Africa, avoids chickens when looking for hosts to feed on. This indicates that, unlike humans, cattle, goats and sheep, chickens are a non-host species for A. arabiensis and that the mosquitoes have developed ways of distinguishing them from host species.
[quote]We were surprised to find that malaria mosquitoes are repelled by the odours emitted by chickens. This study shows for the first time that malaria mosquitoes actively avoid feeding on certain animal species, and that this behaviour is regulated through odour cues [/quote]To find out which species the mosquitoes prefer, the research team collected data on the population of human and domestic animals in three Ethiopian villages. They also collected blood-fed mosquitoes to test for the source of the blood that the mosquitoes had fed on. People living in the areas in which the research was conducted share their living quarters with their livestock.
The researchers found that while A. arabiensis strongly prefers human over animal blood when seeking hosts indoors, it randomly feeds on cattle, goats and sheep when outdoors, but avoids chickens in both settings, despite their relatively high abundance.
The researchers found that significantly fewer mosquitoes were caught in traps baited with chicken compounds than in control traps. Suspending a living chicken in a cage next to a trap had a similar repellent effect.
Because it feeds indoors and outdoors on various host species, A. arabiensis is difficult to control with existing methods, according to previous research. The results of this study suggest that, in combination with established control methods, the odours emitted by chickens and other non-host species could prove useful in controlling A. arabiensis.
People in sub-Saharan Africa have suffered considerably under the burden of malaria over an extended period of time and mosquitoes are becoming increasingly physiologically resistant to pesticides, while also changing their feeding habits for example by moving from indoors to outdoors. For this reason there is a need to develop novel control methods – and the humble chicken could be the answer.