A worrying new report indicates that when mosquitoes encounter antibiotics in their meals of blood, their gut microbiomes (totality of the microorganisms and their genetic componets) are drastically reduced. This means that they become less adept at fending off a subsequent malaria infection.
The implications of this are that the mosquito gut microbiome usually acts strongly in response to an ingestion of blood. This helps to ward off malaria causing parasites like Plasmodium falciparum, by mounting an immune response.
Malaria is caused by a single-celled parasite belonging to genus Plasmodium. The parasite is transmitted by mosquitoes in territories in over 100 countries and presents a risk to about 3.3 billion people. Mosquitoes spread the parasite to humans through their bites; the parasite then travels to the liver, where it matures and reproduces in forms that infect the red cells and cause clinical symptoms.
When researchers based at Imperial College London fed mosquitoes blood with clinically relevant levels of a common antibiotic mixture of penicillin and streptomycin, the protective microbiome altered in composition and lost over half of its species diversity. After the treated mosquitoes feasted on the blood of Plasmodium-infected mice, 21 percent more of the insects carried the malaria parasite. The researchers found a similar result when they fed the mosquitoes human blood from malaria patients mixed with the antibiotic cocktail.
Although the gut microbiome can protect mosquitoes from parasites, its rapid proliferation after the insects feed can also hamper the hosts’ fitness. The researchers found that treating the mosquitoes with antibiotics led to increases in the number of egg-bearing females, the number of eggs per female, and mosquito survival rates, suggesting that antibiotics can boost the populations of both P. falciparum and its insect vectors.
This means that the common use of antibiotics to treat fevers, tuberculosis, leprosy, and other diseases in areas such as sub-Saharan Africa could actually help to increase the risk of malaria and work against malaria treatments.
The findings have been reported in Nature Communications. The study is titled “Antibiotics in ingested human blood affect the mosquito microbiota and capacity to transmit malaria.”
