It was a dark and muggy night in June; Jane, a student at the University of Pittsburgh Pymantuning Lab of Ecology, decides to take a stroll through a forest trail nearby. Prior to leaving, Jane forgets to apply insect repellant. She immediately learns her lesson while a barrage of mosquitos penetrate the epidermis of her skin. Jane returns with an astounding amount of red bumps caused by the immune response that combats mosquito saliva.
When Jane returns to civilization, she visits the student health center. As a safe sex advocate, she takes a sexually transmitted disease (STD) test, including a human immunodeficiency virus (HIV) test. A few days later, Dr. Hu calls Jane with results from the medical test. “Jane, the HIV test result is positive; I would like you to come into the office,” says Dr. Hu. Jane burst into tears and blame the mosquitos for the HIV infection. The physician attempts to ease the stress by informing her that individuals with HIV live long lives when medicating with anti-viral cocktails that slow infection rates. Jane asks, “Why did this happen to me?” Dr. Hu educates her on the possible modes of transmission and mosquitos are not one of them.
Jane demands to take a follow-up test to reconfirm the results. When the second results process, Jane tests negative for HIV; she instantly feels as if the “weight of the world is lifting off her shoulders.” Dr. Hu said, “0.2 percent of HIV tests give false positive results; sometimes western blots are used in addition to HIV tests in order to confirm result accuracy.” Jane is gracious that she is the 0.2 percent that result in false positive tests; she lives happily ever after.
It doesn’t end here! Are mosquitos’ vectors for the transmission of HIV to humans? The answer is possibly, but highly unlikely! According to mediaaids.org, a female mosquito penetrates the human skin with a needle-like mouthpart called a proboscis. The proboscis consists of a salivary tube (hypopharynx) which is separate from the blood drawing canal (labrum); therefore, the blood flows into the mosquito and saliva is only injected.
You ask, why are other diseases, such as malaria, transmissible by mosquitos? Malaria multiplies within a mosquito and transmits into the salivary glands where it can be injected into the host. HIV cannot replicate within the gut of a mosquito because it requires specialized cells only found in humans. Even if HIV could be transmissible through mosquito saliva, the uptake of virus is not sufficient to initiate an infection within a human. It would take thousands, if not millions, of HIV infected mosquitos to accumulate an ample amount of virus to jumpstart the infection.
To confirm the notion that mosquitos cannot act as a vector of HIV, researchers designed in-vitro experiments testing this theory (Jupp & Lyons, 1987). In addition to mosquitos, bedbugs were tested for HIV transmissibility. After the insects fed on a blood-virus mixture, reverse transcriptase activity was assayed. Although, the virus survived in bedbugs for 1-4 hours (time dependent upon genus), there was no virus survival in mosquitos, and the transmission of HIV to uninfected blood was unsuccessful. It was determined that bedbugs and mosquitos are not mechanical vectors of HIV.
Altogether, this idea of HIV transmissibility by mosquitos is established in medical literature as fiction; although, there are many ways to transmit HIV, it is very difficult to contract. Now you can sleep well at night, or run on a trail knowing that you will not contract HIV via mosquito. You can however; contract malaria, yellow fever, and West Nile, just to name a few. Case in point; HIV is the least of your worries.
Note: The story represented in the aforementioned post is fictitious.
by Sheream Reed
Jupp, P. G., & Lyons, S. F. (1987). Experimental assessment of bedbugs (cimex lectularius and cimex hemipterus)and mosquitoes (aedes aegypti formosus) as vectors of human immunodeficiency virus. AIDS (London, England), 1(3), 171.
Mosquitos Can Transmit HIV. (2015). Retrieved June 24, 2015, from http://www.mediaaids.org/content/page/mosquitoes_can_transmit_hiv_aids