Are itchier insect bites more likely to make us sick?

28 June 2016

New research suggests the worse our reactions to mosquito bites are, the more likely it is we’ll get sick, says Dr Cameron Webb.

New research suggests we could better understand mosquito-borne disease by looking closely at our itchy bites.

Mosquitoes need blood. Unfortunately, they often get that blood from us; some of us are bitten more commonly than others. But mosquitoes aren’t flying syringes transporting droplets of infected blood from person to person. The mosquitoes need to be infected with a pathogen first before it can be passed on. And, more importantly, the mozzie’s spit must be infected.

Bites and bumps

When a mosquito bites, she (only female mozzies bite) injects saliva to get the blood flowing. It’s a mixture of chemicals that helps the mosquito suck up blood from their unsuspecting victim.

Bites are usually worse on kids. Lolo from Tahiti/FlickrCC BY

The reaction to mosquito bites can vary greatly. For many, a “mozzie bite” will be a mild annoyance that resolves itself without too much trouble. For others, the reaction can be more serious.

It is particularly troublesome for young children who seem to react the worst. While there are no magic solutions to solve the itch, reactions generally get less severe as we develop a tolerance to bites.

The spit may cause a reaction but it can also contain something more serious. Mosquito-borne pathogens, such as malariadengue and chikungunya, infect hundreds of millions of people every year. The emergence of Zika virus and its link to birth defects is yet another reminder of how potent these pathogens can be.

Spit the secret to infection

Not everyone bitten by a mosquito carrying a virus will develop symptoms. New research suggests the worse our reactions to mosquito bites, the more likely it is we’ll get sick.

The scientists allowed the yellow fever mosquito, Aedes aegypti, to bite laboratory mice and then injected the mice with Semliki Forest virus (an African mosquito-borne virus that generally causes mild symptoms in humans) via syringe.

Other mice were only injected with the virus. What they found was that the immune cells that rushed to the bite site as part of an inflammatory response helped the virus replicate and spread. Mice without mosquito bites had substantially lower rates of infection.

The implication is the reaction of the host to a mosquito bite may play a critical role in the virus' ability to infect the host. This isn’t surprising, and previous research has suggested an important role for mosquito saliva in virus transmission. These mosquito-borne viruses have evolved to exploit mosquitoes to get from host to host, why not adapt to the immune response of their hosts to further aid their survival?

Reducing bite reactions and infection risks

The latest research hints at a fascinating potential for mosquito-borne disease prevention.

There’s a pretty easy way to stop mozzies from biting you. Fairfax county/FlickrCC BY

We already have a wide range of safe and effective mosquito repellents that can help prevent bites. We just need to encourage people to use them correctly. If you can stop mosquitoes biting, you can stop disease.

Perhaps the use of anti-inflammatory creams or other medications may further reduce the chances of illness. It’s difficult to stop all bites and only takes one infected mosquito to slip through the cracks in our repellent coverage to cause infection.

Could using these creams act as a safety net? If you can’t stop all the bites, at least minimising the inflammation may assist in reduce risk of disease!

This article was first published in The Conversation.

Kobi Print

Media and PR Adviser (Medicine and Health)
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