West Nile virus (WNV) is a viral disease that can cause encephalitis or meningitis, infection of the brain and the spinal cord or their protective covering. Prior to 1999, the disease was found only in Africa, Asia and southern Europe. Since 1999, WNV has spread throughout North America and has continued to cause disease in the United States. The yearly number of cases and fatalities has fluctuated depending on the weather conditions throughout the nation.
WNV is spread to people by the bite of an infected mosquito. The principal transmitter of WNV is the Northern House Mosquito (Culex pipiens). Mosquitoes first become exposed to the virus when they feed on birds that are infected with WNV. Once the mosquito is infected, it may transmit the virus to people or other animals when it bites them. Many birds can be infected with WNV, but crows and blue jays are most likely to die from the infection. Horses, too, are prone to severe WNV infection. People cannot get WNV from another person or from a horse that has the disease.
There is no vaccine currently available for WNV for people or most animals. However, there are vaccines available for horses, which represent 96.9 percent of all reported nonhuman mammalian cases.
WNV has become endemic in the United States and remains a serious disease threat; however, the number of cases and deaths vary significantly as climatic conditions vary by region from year to year. Sporadic seasonal epidemics will continue to occur in various regions of the country when weather and environmental conditions are most suitable. State, federal and local agencies continue to work together to address the health risks of WNV to Ohio families and their animals. Mosquito control efforts are often increased in urban areas during the summer to protect people from potential exposure to the disease.
How to Prevent WNV
Scrap tires can be a prime breeding source for mosquitoes, including the northern house mosquito, which can carry WNV. When discarded, tires can accumulate small pools of water, where adult mosquitoes will lay eggs. Over the course of one breeding season, thousands of mosquitoes can be generated from just one tire. If tires infested with eggs, larvae or pupae are transported, the potential to spread mosquitoes carrying the virus increases. Breeding takes place in water-filled tires, where eggs are laid and the larvae and the pupae can grow. Adult mosquitoes emerge from the water in as little as seven days after hatching.
Businesses such as retail tire sales locations, retreading operations, fleet maintenance garages and motor vehicle salvage dealers routinely remove tires in the course of business. Ohio regulations allow such facilities to accumulate a limited number of scrap tires generated by their business operations, but also require them to control mosquitoes at their facilities. Ohio's tire rules require that these facilities either keep water from accumulating in scrap tires stored at their site, or apply either larvicide or pesticide to the tires each month from April to November each year. Businesses choosing to treat scrap tires must maintain records to document their compliance.
Scrap tires may also be found around farms and private residences. Scrap tires are often found mixed with other solid waste at open dump sites. Such sites often provide additional containers (such as discarded cartons, packaging, buckets and more) that provide breeding locations for mosquitoes.
If you have scrap tires on your property or at your farm or business location, you are responsible for making sure they do not create a nuisance. There are a number of ways to eliminate mosquito-breeding in scrap tires:
- Remove and properly dispose of the tires.
- If the tires cannot be immediately removed, standing water in tires should be eliminated. This can be done by properly storing dry tires under a tarp and making sure rainwater does not accumulate.
- Where breeding areas cannot be eliminated, larviciding is the most effective control technique. Some larvacides can only be applied by certified pesticide applicators.
- If you are concerned about a tire pile in your area, contact local health officials or the Ohio EPA to find what mosquito control measures are being taken, or could be taken.
People with mild infections may experience fever, headache, body aches, skin rash and swollen lymph glands. People with more severe infections may experience high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, occasional convulsions and paralysis. If you have any of these symptoms, contact your doctor.
Reducing Mosquito Numbers Around Your Home, Neighborhood, Farm or Business
Breeding sites can be eliminated by removing standing water available to mosquitos. Here are some simple steps:
- Dispose of tin cans, plastic containers, ceramic pots or similar water-holding containers that have collected on your property.
- Promptly clean up solid waste and scrap tires that have been dumped or discarded on your property.
- Pay special attention to discarded tires. Stagnant water in tires is an ideal site for mosquito-breeding.
- Drill holes in the bottom of recycling containers left outdoors and in tires used for swings, barriers, running exercises, etc., so they won't hold water.
- Have clogged roof gutters cleaned every year, particularly if leaves from surrounding trees have a tendency to plug the drains. Roof gutters can produce millions of mosquitoes each season.
- Turn over plastic wading pools when not in use. Stagnant water in a wading pool becomes a place for mosquitoes to breed.
- Turn over wheelbarrows and don't let water stagnate in bird baths. Both provide breeding habitats for domestic mosquitoes.
- Aerate ornamental pools or stock them with fish. Water gardens can become major mosquito producers if they are allowed to stagnate. Clean and chlorinate swimming pools not in use. A swimming pool left untended for a month can produce enough mosquitoes to result in neighborhoodwide complaints. Mosquitoes may even breed in the water that collects on pool covers.
- Use landscaping to eliminate standing water that collects on your property. Mosquitoes may breed in any puddle that lasts for more than four days. You can call your local health department or your nearest Ohio EPA district office to ask about tire disposal locations.
Don't dump tires anywhere! Tires last a long time. Sooner or later, someone will be exposed to the mosquitoes breeding in them. Take them to a licensed scrap tire facility.
The Status of WNV in Ohio
WNV has been confirmed in Ohio every year since 2001. Infected mosquitoes, birds, horses and humans have been found in all Ohio counties. Therefore, the virus can be present throughout the state.
For the current status of WNV in Ohio and for more information, you can visit the following websites or contact your local health department.
- The Ohio State University: vet.osu.edu/extension/west-nile-virus-resources
- Ohio Department of Health: www.odh.ohio.gov/wnv