Bacterium immunizes mosquitoes against Dengue fever and Zika infection

While the strong usually eat the weak, every year the minuscule mosquito causes hundreds of millions of cases of severe or even fatal disease by transmitting parasites (malaria) or a wide variety of viruses to humans through their bites, e.g. flaviviruses (sidenote: Flavivirus is a genus of viruses which consists of >70 members including several that are considered significant human pathogens. Transmitted to humans through the bite of infected mosquitoes, Flaviviruses display a broad spectrum of diseases that can be roughly categorised into two phenotypes:
- systemic disease involving haemorrhage (Dengue and yellow Fever virus)
- and neurological complications (West Nile and Zika viruses) Explore https://pubmed.ncbi.nlm.nih.gov/34696709/ ) (Dengue (sidenote: Dengue viral infection transmitted to humans through the bite of infected mosquitoes. Most people with dengue have mild or no symptoms and will get better in 1–2 weeks. Rarely, dengue can be severe and lead to death. If symptoms occur, they usually begin 4–10 days after infection and last for 2–7 days: high fever (40°C/104°F), severe headache, pain behind the eyes, muscle and joint pains, nausea, vomiting, swollen glands, rash. Individuals who are infected for the second time are at greater risk of severe dengue. There is no specific treatment for dengue. Explore https://www.who.int/en/news-room/fact-sheets/detail/dengue-and-severe-dengue ) , Zika (sidenote: Zika viral infection transmitted primarily by Aedes mosquitoes, which bite mostly during the day. Most people with Zika virus infection do not develop symptoms; those who do typically have symptoms including rash, fever, conjunctivitis, muscle and joint pain, malaise and headache that last for 2–7 days. Zika virus infection during pregnancy can cause infants to be born with microcephaly and other congenital malformations as well as preterm birth and miscarriage. There is no specific treatment available for Zika virus infection or disease. Explore https://www.who.int/news-room/fact-sheets/detail/zika-virus ) , etc.), alphaviruses (sidenote: Alphavirus genre de virus comprenant 27 virus dont le redouté (et imprononçable) Chikungunya, qui après un délai d’incubation de 2 à 10 jours, provoque une fièvre et des atteintes articulaires sévères. Les alphavirus sont transmis par la piqûre d’un moustique infecté. Explore https://www.ncbi.nlm.nih.gov/books/NBK7633/ ) (Chikungunya), etc. What if the solution is not to eliminate the mosquito (insecticides) or keep it at bay (mosquito nets, repellent), but simply to prevent it from catching the virus and transmitting it to humans? 

Protecting the mosquito...

This serious solution has been put forward by a Chinese team based on their work on the gut microbiota of mosquitoes. Among the 55 bacteria present in the insects’ digestive tract, one – Rosenbergiella YN46 – caught their attention. Why? Because it permanently prevented the mosquitoes that ingested it from catching flaviviruses.

How is this possible? This bacterium takes up permanent residence in the mosquito’s digestive tract, where it transforms glucose (sugar) into an acid. As a direct consequence, the digestive tract contents become highly acidic, spoiling the flaviviruses. Unable to infect mosquitoes, these viruses will not then infect humans.

...to protect humans

The researchers did not confine themselves to laboratory work. They confirmed their idea in the field. They observed that, in the prefectures of the Chinese province of Yunnan in which Dengue wreaks havoc, mosquitoes rarely harbor the bacterium in their digestive systems. Conversely, in prefectures where only a few isolated cases of dengue fever have been reported, the majority or almost all mosquitoes (91.7% in Wenshan prefecture) carry the bacterium.

The good news is that not only is it easy to inoculate mosquitoes with the bacterium (you just need a bowl of sugar water containing the bacterium), but that the insect retains it throughout its life (from aquatic larvae to winged adult) and passes it on to the next generation. In other words, inoculation with the protective Rosenbergiella YN46 bacterium lasts for life and is passed on to the mosquito’s offspring.