We have finally found a usefulness for mosquitoes: we can analyze the blood they feed on (often ours) to discover the infections of their victims. This method, presented during a conference held in Malaysia last November and illustrated in an article in Nature, could serve not only to identify the pathogens from which humans have been infected in a given area, but also to identify an animal reservoir of a new virus before it jumps species (spillover).
Last dinner. After catching around 55,000 mosquitoes in Brisbane parks between 2021 and 2022, researchers tested the blood they dined on for antibodies to the Ross River virus, which causes an endemic disease in Australia and the Pacific Islands southern. They then sequenced the DNA fragments present to identify the animal host they had stung.
Of the mosquitoes caught, 480 had eaten blood: more than half was human blood, 9% was from cows and 6% from kangaroos, as well as other minor percentages from other animals. Of the blood collected in the 253 insects that had feasted on our bodies, more than 50% had antibodies to the Ross River virus; the percentage rose to over 75% in the case of cows and kangaroos.
Arthritis and joint pain are the most common symptoms of the disease caused by the Ross River virus (whose name derives from the Australian Ross River, in the photo, where the first case was identified). It belongs to the same family of mosquito-borne viruses that cause dengue, Japanese encephalitis, and yellow fever.
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Future applications. In theory, this approach could be used for any pathogen that triggers an immune response in the host (and therefore also for SARS-CoV-2 or Ebola, for example). “This technique could help researchers delve deeper into some diseases we know little about, such as Japanese encephalitis in Australia,” said Eloise Skinner, a disease ecologist at Griffith University.
Current limits. Currently, the method still has several limitations: one of all, the impossibility of collecting data regarding when and where animals and humans were infected by mosquitoes − thus preventing timely action to curb any increase in infections .
Furthermore, it is not clear whose blood the mosquitoes ingested is: in practice, several mosquitoes could have bitten the same host, and therefore the final data on infections could be false. A final obstacle is given by the fact that mosquitoes are generally difficult to catch, especially since the females, after having eaten, hide in dark and damp places to digest.