[Public Health] West Nile Virus: Education Is Key — Knowledge Is Power!

Author’s note: West Nile virus (WNV) first came into the limelight in the United States in 1999. Since this time scientists of all types — entomologists, epidemiologists, virologists — as well as local, county, state and national authorities have focused their efforts on this mosquito-borne disease. Make sure that you are aware of the most up-to-date information on how to best avoid and protect yourself from mosquitoes that may carry WNV. Passing this information to your clients will be greatly appreciated and will add to the professional image you and your technicians portray.

West Nile virus (WNV) was first isolated from an adult woman in the West Nile District of Uganda in the 1930s. The virus was characterized in Egypt in the 1950s. WNV became recognized as a cause of severe human meningoencephalitis (inflammation of the spinal cord and brain) in elderly patients during an outbreak in Israel in 1957.  In recent years WNV has emerged in temperate regions of Europe and North America, presenting a threat to public, equine, and animal health. The most serious cases of WNV infection involve fatal encephalitis (inflammation of the brain) in humans and in horses and death in both wild and domestic birds.

Since the first reported human case in the U.S. in 1999, this mosquito-borne disease has received more attention in the press and by scientists than any other mosquito disease reported in the United States. There are many ways that the pest management professional can be involved with mosquito control, but the focus of this article will be on education. While you may not be able to sell a mosquito control service to your client, ensuring that your technicians are very well educated on the topic of WNV will speak volumes for the image that they portray to your customer. More importantly, educating the consumer about WNV, pointing out myth and fact about what they can and can’t do, will also help the overall battle against this mosquito-borne disease and others in the United States.

LIFE CYCLE. The West Nile virus is maintained in nature when a mosquito vector transmits the virus between vertebrate hosts. The primary vector for WNV in the United States are mosquitoes in the genera Culex sp., those that commonly breed in urban areas and prefer to feed on birds. At least 43 other different mosquito species including other Aedes, Anopheles, and Psorophora mosquito species, have tested positive for WNV. Mosquitoes acquire WNV when feeding on infected birds. The virus is then stored in the mosquito’s salivary glands and transmitted to humans and other incidental hosts when the mosquito takes a blood meal. The virus has been detected in many wild bird species, including the American crow. Humans, horses, and most other mammals are generally considered incidental or dead-end hosts, as they are not generally known to develop a high enough viral load to either transmit, or become a reservoir for West Nile virus.

SYMPTOMS. Although we certainly are not doctors, it is important to be familiar with the general symptoms of WNV, so that you can recognize and convey them clearly when speaking with the public. Unfortunately, symptoms are so general it is quite often difficult or confusing when comparing them to other illnesses. Remember, be familiar with the symptoms but do not attempt to make a diagnosis. Again, we are not medical professionals, but if, in the course of your discussion someone mentions the following symptoms you should simply suggest that they visit a doctor and get it checked out.

According to the Centers for Disease Control and Prevention (CDC) infection with WNV can be asymptomtic (no symptoms), or can lead to West Nile fever or severe West Nile disease.

It is estimated that about 20 percent of people who become infected with WNV will develop West Nile fever. Symptoms include fever, headache, tiredness, and body aches, occasionally with a skin rash (on the trunk of the body) and swollen lymph glands. While the illness can be as short as a few days, even healthy people have reported being sick for several weeks.

The symptoms of severe disease (also called neuro-invasive disease, such as West Nile encephalitis (encephalitis refers to an inflammation of the brain) or meningitis (inflammation of the membrane around the brain and the spinal cord)  include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. It is estimated that approximately 1 in 150 persons infected with the West Nile virus will develop this more severe form of disease. Serious illness can occur in people of any age; however people over age 50 and some immuno-compromised persons (for example, transplant patients) are at the highest risk for getting severely ill when infected with WNV.

Most individuals (about four out of five people) who are infected with West Nile virus will not develop any type of illness (an asymptomatic infection); however you cannot know ahead of time if you’ll get sick or not when infected.

Symptoms of West Nile fever will generally last a few days, although even some healthy people report having the illness last for several weeks. The symptoms of severe disease (encephalitis or meningitis) may last several weeks, although neurological effects may be permanent.

CONTROL. Successful West Nile virus control programs as practiced nationwide today rely upon principles of Integrated Pest Management (IPM). Area-wide mosquito IPM may utilize physical, chemical, mechanical, cultural, biological, and educational measures to attain the desired level of mosquito control consistent with a given community’s needs.  Chemical application measures are predicated upon surveillance data. Comprehensive surveillance programs therefore drive intervention efforts in a given area. Knowledge of the target mosquito vector allows efficient allocation of control resources specifically tailored to safely counter each stage of the mosquito life cycle.

Larval control through water management, vegetation management and source reduction, where compatible with other cultural control measures, can provide a sound pest management alternative. Additionally, the use of currently available environmentally friendly, EPA-approved larvicides can aid in an effective mosquito IPM program.

When it is clear that source elimination or larval control measures are inadequate, or in the case of imminent disease, the Environmental Protection Agency (EPA) and CDC have emphasized in a published joint statement the need for considered application of adulticides by PMPs trained in the special handling characteristics of these products. The extremely small droplet aerosols utilized in adult mosquito control are designed to impact primarily flying adult mosquitoes. Degradation of these small droplets is rapid, leaving little or no residue in the target area at ground level. These special considerations are major factors that favor the use of very low application rates for these products, generally less then 4 grams active ingredient per acre, and are instrumental in minimizing adverse impacts.

WHAT CAN I DO? Most often the general question that one may be faced with is: “What can I do?”  Although several ‘top 10’ lists are available on the Internet from trusted sources, here are some keys things that an individual may want to keep in mind.

• Make sure doors and windows have tight fitting screens.
• Repair or replace screens that have tears or holes in them. The last thing that you want is mosquitoes entering the house. This is especially important for those that live in areas where there are significant   mosquito populations.
• Wear long sleeves, long pants, socks and closed shoes when venturing outdoors especially during peak mosquito activity such as dusk and dawn. 
• Beware of the times that mosquitoes are most active, generally April through October, and avoid prime mosquito locations including marshes and wetlands. 
• Use mosquito repellents on exposed skin whenever you are in an outdoor area where mosquitoes may be present. Repellents will provide extra protection individuals need when exposed to mosquitoes and other disease-carrying insects. 
• Eliminate standing water, including clogged gutters, pool covers, empty wheel-barrows, and pools of water anywhere in the yard.
• Dispose of tin cans, plastic containers, ceramic pots or similar water-holding containers that have accumulated.
• Be sure to remove used tires, which are a common mosquito breeding site. 
• Remind or help neighbors to eliminate breeding sites on their properties. 
• Clean and chlorinate swimming pools, outdoor saunas and hot tubs. If not in use keep covered. 

Unfortunately, even if an individual home-owner takes care of outdoor breeding sites in their backyard, the next-door neighbor can keep the local population going if they too do not take steps to remove breeding sites. Encourage local officials to address smaller bodies of water such as ponds with an appropriate mosquito larvicide. Additionally, larger bodies of water may be stocked with mosquito-eating fish. In your community, ensure that planners/organizers of summertime activities for youth and the elderly (those that are most at-risk for contacting WNV) — such as summer camps, park and recreation centers, and senior centers are proactively using established pest control strategies for mosquito control. Learn as much as you can about your community’s mosquito control program. If local elected officials have not implemented a mosquito control program in your area, you may want to voice an opinion about doing so. Ensure that local community leaders are giving protection to the public through integrated mosquito management programs.

For more information on a particular local level, whether state or smaller, I have included several Web sites at the end of this article that provide the PMP in any part of the country a resource for gaining more local information for their particular area. If you suggest that someone seek more information, be sure to guide them to a reliable source, such as the CDC’s Web site, www.cdc.gov.
For more local information you might suggest a local university or state/local government department of health Web site in addition to those I have provided.

KNOWLEDGE = SUCCESS. Your current business plan may or may not include mosquito treatment options. Regardless, being knowledgeable about West Nile virus and ensuring that each of your service technicians are, can only increase the professional image that you display. Being knowledgeable and passing on facts to your customers will increase your chances for success in the future! 

The author is a research scientist from Racine, Wis. He can be reached at rkopanic@giemedia.com.

Literature cited:
Centers for Disease Control — Web site — http://www.cdc.gov/ncidod/dvbid/westnile/index.htm

American Mosquito Control Association — Web site — http://www.mosquito.org/mosquito-information/virus.aspx

On the Web

The following websites contain excellent educational material about West Nile virus and other arboviruses, mosquito control activities, steps individuals can take to protect themselves, and West Nile virus surveillance results throughout the United States:

• www.cdc.gov/ncidod/dvbid/westnile/index.htm
  The Centers for Disease Control and Prevention (CDC) West Nile virus Homepage, which features a wealth of information plus many links to other WNV sites.
• http://cindi.usgs.gov/hazard/event/west_nile/west_nile.html
  The site for updated West Nile virus surveillance maps of positive bird, mosquito, equine and human cases.
• www.epa.gov/pesticides/factsheets/skeeters.htm
  The EPA site with mosquito control guidelines, fact sheets on mosquito sprays, etc. 
• http://npic.orst.edu
  Click on “West Nile virus Resource Guide.” This is the National Pesticide Information Center (NPIC) with insect repellent information and links to a multitude of other West Nile virus sites.