A small, biting fly, the vector of a major parasitic disease, visceral leishmaniasis, often lays its eggs on dogs before infecting humans. However, the insect manages to modify the smell of dogs to make them irresistible to female flies.
Attract females with an irresistible scent left on dogs
Visceral leishmaniasis (or black fever) causes between 20 and 30,000 deaths per year. It is the deadliest parasitic disease in the world after the unbridled malaria. A parasite of the genus Leishmania is the cause of the disease and the insect vector is a small biting fly of the Phlebotomines. As with mosquitoes, only females are dangerous. And left untreated, visceral leishmaniasis is fatal in almost all cases.
Common in Europe, the disease is also raging on the American continent with 95% of infections. Among the countries most affected, Brazil is in the lead. The insect succeeds in laying eggs on its human hosts via another animal reservoir, namely dogs. As explained in a study by Lancaster University (UK) published in PLOS pathogens, they manage to change the smell of man’s best friend in order to attract female flies.
A real discovery
Before this work, researchers knew that this “parasitic manipulation” could take place on rodents. By changing their scent, the latter became more attractive to female flies. This therefore resulted in more stings and thus a better transmission of the parasite. On the other hand, the fact that dogs are also one of the natural reservoirs of the disease in humans is a real discovery. Let us recall in passing that infected dogs transmit the disease by biting and licking.
As part of their work, the researchers collected hair and blood from dogs in Governador Valadares (Brazil). Then, after screening the animals, they extracted the odorous chemicals about fifteen dogs. These substances were then presented to male and female sandflies. The hairs attracted insects of both sexes, but infected samples were seduces 67.7% of females, a data absent in males.
Now scientists want to answer other questions. They wonder, for example, why the smell of infected dogs is so attractive to female flies and would like to identify the most compelling chemicals. They would also like to know which receptors activate in insects. According to the researchers, this information could prove important in the fight against visceral leishmaniasis.