BY ANNELIESE MOLL
For the UAS Whalesong
Mosquito-borne viruses, while not such a big deal for us here in Alaska, are a very real threat for people living in warmer climates. Surprisingly, there are quite a few viruses that mosquitoes can carry. Some of the ones that are more commonly known are malaria, West Nile virus, yellow fever, and more recently the zika virus (ZIKV). The zika virus was first recorded in 1947 in Uganda. However, since it was rare and the symptoms believed to be mild, there was not much thought given to it after that. It was the outbreak in Brazil in 2015, with the high number of microcephaly cases, that really brought ZIKV to the light. The link with microcephaly, a birth defect where the baby’s head is smaller than should be expected for its sex and age, is a comparatively new one. When the virus was first being described, it was noted that there was a potential for the virus to infect brain cells in mice.
With mosquito-borne viruses, the viruses are transmitted by female mosquitoes. The virus moves from the gut to the mosquito’s salivary glands. Interestingly enough, in another study, researchers found that mice developed more severe infections when a virus was injected by a mosquito than with a needle.
This has prompted several theories about what it is about a mosquito’s saliva that causes an increased reaction. One such theory is that there are a series of compounds in it that act as immune system suppressor, however, this has been shown to not be the case. This is what’s really going on: the saliva triggers an inflammation after the bite. Neutrophils, which are some of the body’s first responders, head to the site of the bite. Then, the macrophages engulf any microbes that are labeled as foreign. What researchers found was that the macrophages are infected by the virus they engulf, which then spreads the virus. Besides being transmitted though mosquito bites, the Zika virus can also be transmitted sexually.
However, there is another layer to ZIKV: there another mosquito borne virus that might cause people to be more susceptible. Dengue virus is similar enough to Zika that the antibodies from it can interfere with the immune system’s response to Zika and has the ability to act as a booster to the virus’s ability to replicate. This ability is called antibody-dependent enhancement. There are many other viruses that can take advantage of this technique in order to more effectively take over.
Currently, scientists are working to create a vaccine. There are three different vaccines to date that have undergone monkey studies. The data on these looks hopeful. Hopeful enough to perform the first human trials at the end of July/beginning of August of this year. However, nothing has been released, so there is currently no treatment.
While a vaccine is being developed, the best way to not being infected is to avoid mosquitoes. Some even have been discussing possibly trying to eliminate mosquitoes in some areas, however, that could have some very negative impacts on the environment. Not just from use of chemicals (or other extermination techniques), but there are many other organisms that are dependant on mosquitoes as a source of food.