Sep102013

"West Nile Virus and Mosquito Control"

People have heard of West Nile Virus: It is up there on the list of health nuisances, along with several other geographically-linked or animal-themed viral boogeymen. Although the public focus on West Nile as a pathogen to watch – in America at least – has softened over the years, the RNA virus is still active in several mosquito populations that reside throughout the country.

WNV TransmissionWest Nile Virus is a zoonotic arbovirus, meaning that it originates in arthropods, in this case the mosquito.   It is described as zoonotic due to the fact that it can be transferred from one species to another. For a long time West Nile was not considered to be a threat to human beings – it was thought to pass from mosquito to bird, or mosquito to bird to another animal, such as a horse. Since the discovery of West Nile in the 1930's to the early 1990's, the virus was low on the international radar. This all changed in 1994 when a serious outbreak concerning humans occurred in Algeria, and then later in 1996 in Romania. The first case of West Nile was reported in New York City in 1999. Since then the virus has traversed much of the United States, reaching up into Canada, and down into South America.

mosquitoesdeadMost cases of infection are relatively minor, ranging from a low-grade fever, and flu-like symptoms, to bouts of fatigue, muscular pain and vomiting. These cases that are the most common do not require any hospital stays and can normally be treated with rest and re-hydration. Less than one percent of cases progress to the point of needing medical intervention, those cases include neuroinvasive symptoms. In order to be designated a neurotropic virus, the pathogen has to have a negative effect on the central nervous system itself, meaning that it is, in essence, attacking nerve cells. These rare, severe cases are classified two different ways. The first is West Nile Encephalitis, which can cause inflammation of the brain. The second is West Nile Meningitis, which causes the erosion of the coverings of the spinal cord and those that cushion the brain. One can also experience extrapyramidal symptoms, such as tardive dyskinesia, which leads to involuntary movement of the muscles. There are a few very specific risk factors that increase one's likelihood to contract a more intensive version of the virus: having received an organ transplant, being over 50 years old, and having either hypertension or diabetes.

WNV VaccineThere is currently no human vaccine for West Nile Virus, as most of the time the symptoms involved with exposure clear up all by themselves. There are vaccines available for horses, and it is highly recommended that they are treated with a booster previous to mosquito season. As far as prevention in humans goes, there are several non-medical interventions that can be put into place previous to the spring and summer months. Several sources recommend that individuals sport long-sleeved shirts and pants when about to enter an area that might be rife with mosquito activity. They also recommend that individuals use bug spray, have sturdy screens on the windows, and stay indoors during the peak days of mosquito season. While these are all doable, if not simply common sense suggestions, one would be hard-pressed to find someone willing to don a long-sleeved shirt and long pants in the height of a Virginia summer. So, where does that leave us?

There are several other ways to adjust the environment that one is living in, especially one such as the home. Mosquito management can be as simple as monitoring the areas of standing water in one's yard, or even in one's potted plants. Mosquitoes breed more readily in small pools of stagnant water – so, watch out for ditches, or even kiddie pools that have been left out for too long. As far as pest control options go, PermaTreat Pest Control offers a service called Yard Guard that would control the mosquito population in your yard. Through the combination of these suggestions and services, one can effectively combat West Nile Virus and the mosquito populations that spread it to other hosts.

References:

CDC. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Diseases. (2013). West Nile virus: Prevention and control (Division of Vector Borne Diseases). Retrieved from website: http://www.cdc.gov/westnile/prevention/index.html

EPA. US Environmental Protection Agency, (2011). West Nile virus facts. Retrieved from website: http://www.epa.gov/Region5/pesticides/wnv_facts.htm

Gaines, D. N. Virginia Department of Health, Environmental Health. (2011). Mosquito breeding habitats. Retrieved from website: http://www.vdh.virginia.gov/lhd/CentralShenandoah/EH/WNV/mosquito_breeding_habitats.htm

Hunt, M. (2010). Microbiology and immunology. (5th ed.). Retrieved from http://pathmicro.med.sc.edu/mhunt/arbo.htm

Nash, D., Mostashari, F., Miller, J., O'Leary , D., Murray , K., Huang, A., & Rosenberg, A. (2001). The outbreak of west nile virus infection in the new york city area in 1999. New Englad Journal of Medicine344(24), 1807-14. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/11407341

Zuckerman, A., & Mushahwar, I. (2007). Emerging viruses in human populations. (pp. 137-142). Amsterdam, The Netherlands: Elsevier. Retrieved from http://books.google.com/books?id=HgyS__P8UAQC&pg=PA147&dq=neurotropic viral infections west nile&hl=en&sa=X&ei=Fh3LUcvFBoz69gTNwoCADQ&ved=0CDQQ6AEwAQ