Why Mosquitoes Don't Spread Hepatitis

Mosquito feeds on a human. James Gathany/CDC Public Health Image Library

It's a beautiful day and you're outside enjoying the fresh air. You feel a small prick on your arm and notice that a mosquito is getting a free meal. Without realizing, you kill it with a quick slap of your hand, but notice a little blood on your arm where the mosquito was. Along with the nuisance of a mosquito bite, you might be worried about possible infections you can catch, including hepatitis.

It's intuitive to think that when a mosquito bites someone who is infected with hepatitis, and then bites another person, the second person could be exposed to the disease. Fortunately, viral hepatitis isn't spread through mosquitoes. Let's look at some reasons why.

Mosquitoes Inject Saliva, Not Blood

Because hepatitis B and hepatitis C are spread by contact with infected blood, it's very tempting to think of mosquitoes as flying hypodermic needles. However, the "needle" that mosquitoes feed with, called the proboscis, is actually a complex structure that has separate channels. When a mosquito bites, it injects saliva through one channel. The saliva functions as a lubricant to help the mosquito feed easier. The blood it sucks as a meal flows in a completely separate channel and only in one direction: toward the mosquito. So, it's biologically unlikely for infected blood to be spread to another person.

But, Wait! Mosquitoes Spread Malaria and Yellow Fever. Why Not Hepatitis?

Since mosquitoes can spread some diseases, such as malaria and yellow fever, it is tempting to think they can spread other blood-borne diseases like HIV and hepatitis.

The answer is in the saliva! When a mosquito bites, it injects its own saliva into whatever it is biting. The diseases spread by mosquitoes are actually spread through the mosquito's saliva. Hepatitis, however, is spread through infected blood.

Need More Proof? Viruses are Fragile

The hepatitis viruses are very picky about what they infect and where they can survive. They really like livers, and mosquitoes don't have livers! This means that the mosquitoes aren't really a good home and the viruses wouldn't survive long enough to be spread, even if they could be. Also, people who study mosquitoes have noticed they usually don't bite two people consecutively. After they bite, they will fly away to let their food digest and then after a period of time, they will feed again. Because the hepatitis viruses don't last long in a harsh environment, they wouldn't survive long enough to infect.

What About Insects and Spiders?

Mosquitoes are part of a very diverse biological classification called arthropods, which include a variety of life.

Some types of arthropods include insects, spiders, centipedes, shrimp and crayfish. Experts agree that arthropods don't spread viral hepatitis. A fair bit of scientific study has gone into how arthropods spread disease, especially since HIV emerged in the 1980s.

If Not Mosquitoes, What Does Spread Hepatitis C?

Hepatitis C is spread by direct contact with infected blood. So, some things that could expose you to infected blood would be razors, needles and toothbrushes. Also, certain behaviors put you at a higher risk for spreading hepatitis C. Examples of these would include injecting street drugs without sterile needles and works as well as having certain types of sex with someone who is infected (though this doesn't happen often).

Sources:

Can I Get HIV From Mosquitoes? Centers For Disease Control and Prevention. October 20, 2006. http://www.cdc.gov/hiv/resources/qa/qa32.htm

Viral Hepatitis C. Centers For Disease Control and Prevention. March 7, 2008. http://www.cdc.gov/NCIDOD/DISEASES/HEPATITIS/c/faq.htm#s8

Why Mosquitoes Cannot Transmit AIDS. Rutgers Cooperative Extension. http://www.rci.rutgers.edu/~insects/aids.htm

Continue Reading