Last bloodsucker traps many pathogens

Malaria – Lausanne researchers have found that the mosquitoes that last sucked the blood of an animal infected with malaria catch the most pathogens. They report that in the journal “Proceedings B” of the Royal Society.

Malaria is caused by the so-called plasmodium. This single-cell parasite lodges in red blood cells and destroys them. More than 400,000 people die each year from the infectious disease.

The team led by Philippe Christe from the University of Lausanne has now shown that the order in which mosquitoes stick a sick animal influences the spread of the disease.

The super spreaders among mosquitoes

In field observations they discovered that a few mosquitoes carry a large number of malaria parasites. These are, so to speak, the super spreaders among insects. Most of them, however, are almost completely free of the pathogens.

The researchers took a closer look at this phenomenon in the laboratory. To do this, they had healthy mosquitoes sting canaries that carried the pathogen. Result: The insects all ingested the same number of parasites. But seven days after the blood meal, the mosquitoes that had last bitten were about five to ten times more contaminated with the pathogens.

According to the researchers, the parasites may notice if their host is bitten and then increase their infectiousness.

Refine epidemiological models

The researchers hope that their study will help develop better strategies to fight the disease. “The transmission of malaria increases in the course of the evening,” said Romain Pigeault from the University of Lausanne according to a communication from the university. “The mosquitoes that end up biting will be much more contagious than those that attack at dusk.” That is why mosquito nets become more important the further the night progresses.

The authors also propose to take greater account of the observed effects in epidemiological models of the spread of malaria.

https://doi.org/10.1098/rspb.2020.2615

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