Mosquitoes are tiny flying syringes which comprise a group of about 3,500 species, that transfer droplets of infected blood from person to person.
They hatch into motile larvae that feed on aquatic algae and organic material.
The adult females of most species have tube-like mouthparts called proboscis that can pierce the skin of a host and feed on blood, which contains protein and iron needed to produce eggs.
Thousands of mosquito species feed on the blood of various hosts
The mosquito’s saliva is transferred to the host during the bite, and can cause an itchy rash.
Mosquito saliva in the absence of any pathogens contains hundreds of proteins.
Now, researchers reporting in PLOS Neglected Tropical Diseases have discovered that the interaction of these proteins with the human immune system causes an immune response that can be detected for days after a mosquito bite.
Mosquitoes plasma carry viruses including dengue, yellow fever, chikungunya, Zika and Ross River virus.
They can also transmit malaria, which is caused by a parasite.Viruses take advantage of this biological requirement of mosquitoes to move from host to host.
The pathogens mosquitoes spread by sucking the blood cause over half a million deaths each year and hundreds of millions of cases of severe illness.
The rapid spread of the novel coronavirus has made people become conscious, thinking of possibilities that it could be spread through mosquito bite.
No scientific evidence suggests that mosquitoes are transmitting SARS-CoV-2, the virus that causes COVID-19.
Cameron Webb, a Clinical Associate Professor and Principal Hospital Scientist, University of Sydney stated that there was the need to learn more about the nature of the new coronavirus to help scientists understand whether a mosquito could have a tendency to spread the virus among the people.
He explained that based on the current understanding about the virus, it was highly unlikely for a mosquito to pick up the virus by biting an infected person, let alone to pass it on to others.
Mr Webb explained that mosquitoes could not transmit other viruses, including HIV and Ebola based on a study done.
For HIV, he observed that due to the low concentrations of the HIV circulating in the blood mosquitoes actually do not become infected when they bite infected individuals, adding that for Ebola, mosquitoes did not get infected when scientists injected the virus into them.
When a mosquito bites and sucks up some blood that contains a virus, the virus quickly ends up in the gut of the insect.
From there, the virus needs to infect the cells lining the gut and “escape” to infect the rest of the body of the mosquito, spreading to the legs, wings, and head.
The virus then has to infect the salivary glands before being passed on by the mosquito when it next bites.
This process can take a few days to over a week but time is not the only barrier.
The virus also has to negotiate getting out of the gut, through the body and then into the saliva, each step in the process can be an impenetrable barrier for the virus.
This may be straightforward for viruses that have adapted to this process but for others, the virus will perish in the gut or be excreted.
According to Mr Webb mosquitoes are not a known vector for COVID-19 but was understandable that people would be concerned when there were things like West Nile Virus that are out there and transmitted by mosquitoes.
He noted that COVID-19 mostly spread via droplets produced through the act of coughing, sneezing and by touching surfaces that are contaminated like door knobs, car seats, microphones among others.
Mr Webb indicated that although coronavirus had been found in blood samples from infected persons, stressing that there was no evidence it could spread via mosquitoes.
“Even if a mosquito did pick up a high enough dose of the virus in a blood meal, there is no evidence the virus would be able to infect the mosquito itself.
And if the mosquito is not infected, it won’t be able to transmit it to the next person she bites,” he added.
BY JOYCELINE NATALLY CUDJOE