British and African biologists have studied the eyes of tsetse flies and have found that the purple color of tissue traps is especially attractive for these carriers of sleeping sickness. Such materials will help slow its spread in Africa, the researchers write in the scientific journal PLOS Neglected Tropical Diseases.
“The successful completion of our experiments suggests that computer models based on the concept of photoreceptors can be used to create textiles that are especially attractive to these flies. live in savannas, "the scientists write.
African tsetse flies continue to be one of the main threats to the health of people in many southern regions of Africa and to their livestock. Their danger is due to the fact that unicellular microorganisms - trypanosomes, such as Trypanosoma brucei, as well as other varieties of these parasites live in the saliva of these insects.
When a tsetse fly drinks the blood of people or animals, some of these "passengers" move from its mouth into the blood of the future victim. After some time, trypanosomes spread throughout the circulatory and lymphatic systems of their victims. Reproduction of trypanosomes in nerve tissues causes sleeping sickness, which subsequently leads to the death of the patient. Due to the existence of tsetse flies, almost half of Africa is still unsuitable for animal husbandry.
Now the authorities of African countries and local farmers, as noted by Roger Sunter from the University of Wales (UK) and his colleagues, are trying to solve this problem using special tissue traps. When an insect lands on them, an insecticide enters their limbs and proboscis, which kills the trypanosome carriers.
The world in the eyes of flies
As a rule, black or blue fabric is used for these purposes, which attracts the attention of insects. At the same time, local residents have long noticed that these materials do not always cope with such a task.
In some cases, for reasons unclear to observers, the tsetse ignored the traps, but attacked other decoys of almost the same color. It also turned out that different types of fabrics, covered with the same paint, for some reason caused completely different reactions in flies.
Santer and his team tried to figure out why this is happening. They reproduced the way the tsetse fly's complex faceted eyes perceive the world around it. To do this, scientists have created a full-fledged computer model of insect light-sensitive receptors and optical components of individual facets and calculated with its help how cotton and synthetic fabric looks from the point of view of an insect.
Calculations have shown that synthetic fabrics become attractive to flies only if they are dyed not blue or black, but purple. This is due to the way the tsetse perceive ultraviolet radiation, which is invisible to humans. Guided by this idea, scientists prepared several tsetse traps and tested their effectiveness by setting them at one of the research centers in the Zambezi River Valley, located in northern Zimbabwe.
These experiments showed that the violet tissue was indeed better at luring flies, as a result of which in new traps 1, 3-1, 5 times more insects accumulated than in their counterparts with black or blue fabric. This material had a similar effect on other types of flies that bite humans and animals and also carry dangerous diseases.
The researchers hope that their discovery will attract the attention of the authorities in Zimbabwe and other countries where tsetse is common, and help their residents protect themselves and their livestock from sleeping sickness.