Infected Mosquitos May Help Save Lives
Chris Walker (11 AM Micro) found an interesting story that may indicate an “outside the box” approach for managing Dengue Fever, which is an important tropical disease. Long time readers of BIO230 may recall Wolbachia coming up before with insects, in this Spring 2013 bonus essay about bedbugs. However, I do offer the cautionary tale of the “rabbit-proof fence” as an unfortunate occurrence which was the result of an intentional release of an organism. Here is Chris’ summary:
Dengue fever, or break-bone fever, is a tropical disease caused by the Dengue virus, of which there are 4 currently known strains. The characteristic symptoms include excruciating joint pain, hammer-pounding headaches, fever and rash (CBS News, 2013). Typically, symptoms only last a few days, but the virus can also develop into a more severe form of the disease (hemorrhagic dengue fever). Hemorrhagic dengue fever is more likely to occur in those who are immuno-compromised and in children. Although a person develops lifetime immunity to the particular strain to which they are initially infected, it is believed that a person who is infected a second time with a different strain of the virus may have a better chance of developing hemorrhagic dengue fever (WHO). This can then lead to internal bleeding, shock, organ failure and death. There are an estimated 390 million people are infected with the disease each year, mostly in Asian and Latin American countries, and there are currently no vaccines.
The way that it spreads is through mosquito bites. A female mosquito bites an infected person, acquires the virus, and then transfers the virus to the next person she bites. The interesting thing is that there is a specific type of mosquito (Aedes aegypti) that transmits this virus. What makes this mosquito so special is that it does not play host to a bacteria (Wolbachia) that is normal microbiota found in most other insect species and mosquitos. Scientists believe that the Wolbachia bacteria, which lives in the insects gut, prevents the growth of the virus and therefore prevents the transfer of the virus to uninfected hosts.
With this in mind, scientists experimented and found a way to infect this particular type of mosquito with Wolbachia so that the mosquitos actually pass the bacteria on to subsequent generations. In some cases, this effectively eliminated the ability of that mosquito to carry and infect people with the virus. However, the caveat is that there are different Wolbachia strains as well, which produce varying results in how they eliminate the virus. One strain works at 100%, but it is the hardest one to sustain in the mosquito population.
I find the story very interesting because of all the unique science involved and the potential practical applications. The dengue virus itself is very interesting in the way it invades and acts against the host’s cells. It is an RNA virus that attaches to white blood cells. The reaction of the white blood cells to the presence of the virus is what causes a majority of the symptoms. This virus is also related to many other common viruses including yellow fever and west-nile virus, which are both transmitted via mosquito bites. The fact that scientists have been able to identify and use the bacteria to inhibit the transmission of the virus as well as modify future mosquito generations is fascinating. It could be possible that this type of research could open doors in the battles against other disease causing organisms such as West-Nile virus, malaria, and Lyme disease, which are all transmitted by arthropods.