Animal Care & Control
West Nile Virus 2001
West Nile virus is a mosquito-borne viral infection that is frequently asymptomatic but which can cause flu-like symptoms or, in its most severe manifestation, can lead to central nervous system infection causing encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord). West Nile virus is a flavivirus commonly found in Africa, West Asia, and the Middle East, but until 1999 had not previously been documented in the Western Hemisphere. It is not known from where the U.S. virus originated, but it is most closely related genetically to strains found in the Middle East, and it is closely related to St. Louis encephalitis virus found in the United States.
In 1999, 62 cases of human West Nile encephalitis, including 7 deaths, occurred in the New York area. This started the spread of West Nile virus in the U.S. The virus persisted through the 1999-2000 winter, and spread rapidly throughout New York State and the northeastern and Mid-Atlantic United States in the summer and fall of 2000. By the end of the 2000 mosquito season, all but one county in New York State had documented West Nile virus activity and the virus had been detected in 12 states and the District of Columbia. Fourteen New York City residents – one of whom later died - and six other New Jersey, were hospitalized due to West Nile virus infection in 2000. Based on its widespread distribution, it is likely that West Nile virus has now been established in the Western Hemisphere.
West Nile virus is spread by the bite of an infected mosquito. The usual cycle for this virus is bird – mosquito – bird, where the mosquito is the vector that transmits the causative organism (the virus) from host (the bird) to host. But, sometimes the vector mosquito feeds on other species besides birds and transmits the virus outside the usual cycle to humans and other mammals. Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. Infected mosquitoes can then transmit West Nile virus to humans and animals while biting to take blood. The virus is located in the mosquito’s salivary glands. During blood feeding, the virus may be injected into the animal or human, where it may multiply, possibly causing illness.
Even in areas where mosquitoes do carry the virus, very few mosquitoes – much less than 1% - are infected. If the mosquito is infected, less than 1% of the people who get bitten and become infected will get severely ill. The chances you will become severely ill from any one mosquito bite are extremely small. People 50 and older are at the highest risk of becoming seriously ill if they are infected. West Nile encephalitis is NOT transmitted from person-to-person. You can NOT get it from touching or kissing a person who has the disease, or from a health care worker who has treated someone with the disease. There is no documented evidence of animal-to-person transmission of West Nile virus. However, persons should always avoid bare-hand contact when handling any dead animals and use gloves or double plastic bags when picking them up.
West Nile virus has NOT been found in Colorado as of Dec. 2001. But, with birds being the natural host of the virus many experts say it is just a matter of time. The virus has been found in at least 70 species of birds found dead in the United States. As the virus spreads throughout the bird species and birds continue to migrate south for the winter and mix with birds from other parts of the country and then migrate back north in the summer experts say we will see the West Nile virus spread across the country.
Colorado has started to test dead crows, ravens, and magpies that have been dead less than 48 hours and are not maggot infested. Testing is done between May 1st and October 1st. If you find a dead crow, raven, or magpie that you would like to see about being tested, place it in a double plastic bag and keep it cool. Call you local health department to find out if it is a bird they are interested in having tested. In Denver, you can call
303-698-0076.
As with all diseases transmitted by mosquitoes, you can reduce your risk of getting the disease by reducing mosquito population. Because mosquitoes breed in standing water you can start by eliminating standing water on your property by taking the following steps:
- Dispose of tin cans, plastic containers, ceramic pots or similar water-holding containers.
- Remove all discarded tires on your property. Used tires have become the most important source of mosquito breeding in the nation.
- Drill holes in the bottoms of recycling containers that are kept outdoors.
- Make sure roof gutters drain properly, and clean clogged gutters.
- Turn over plastic wading pools and wheelbarrows when not in use.
- Change the water in birdbaths at least twice a week.
- Clean vegetation and debris from edges of ponds.
- Clean and chlorinate swimming pools, outdoor saunas and hot tubs.
- Drain water from pool covers.
- Use landscaping to eliminate standing water that collects on your property.
For more information on West Nile Virus see the sites below:
Colorado Dept of Public Health & Environment -Zoonotic Disease
Maps of the US Showing Activity of West Nile Virus
CDC’s West Nile Virus Site
|