Ohio State University Extension Fact Sheet

Veterinary Preventive Medicine

1900 Coffey Road, Columbus, OH 43210

Wetlands and West Nile Virus

WNV-1008-06

What Is West Nile Virus?

West Nile Virus (WNV) is a viral disease previously seen only in Africa, Asia, and southern Europe. This virus can cause encephalitis or meningitis, infection of the brain and the spinal cord or their protective covering. For the past six years, WNV has caused disease in the United States.

In 1999, at least 62 people became seriously ill, and seven of those died. Since then, WNV has rapidly spread throughout North America. During the year 2000, 21 human cases of WNV encephalitis were reported in the United States, with two deaths. In 2001 there were 56 cases with seven deaths.

In 2002, 4,156 human cases of WNV encephalitis or WNV fever were reported, with 284 fatalities. During 2003, almost 10,000 human cases of WNV encephalitis and fever were reported from 46 states, with 208 fatalities. In 2004, there were some 2,500 human cases with 87 deaths, with the cases occurring primarily in the western United States. In 2005, there were 2,800 cases with 105 deaths.

In Ohio in 2005, WNV was reported in birds, mosquitoes, humans, and horses. There were 61 human and 15 horse cases identified. It is expected that WNV will continue to be a disease threat in 2006.

West Nile Virus is spread to people by the bite of an infected mosquito. The principal transmitter of West Nile Virus 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 a horse that has the disease.

Continued spread of this disease among wild birds and mosquitoes is anticipated. State, federal, and local agencies are working together to address the health risks of WNV to Ohio families and their animals. Public health officials found WNV in many species of birds, mosquitoes, and horses in 44 Ohio counties during 2005. Once this was known, mosquito control efforts were increased in those areas to protect people from the disease.

• Q. If I’m hiking or walking in an area with wetlands, how can I protect myself from West Nile Virus infection?
• WNV infections usually peak in late summer and early autumn, before mosquito numbers are reduced by hard freezes. If you hike or walk out of doors during this period, you should wear long-sleeved shirts, long pants, and apply insect repellents to clothing and skin, following the label directions, to prevent mosquito bites.


• Q. What is the value of a wetland?
• Wetlands are among the most biologically productive habitats in the world. Before European settlement, Ohio’s wetlands covered 18.9% (5 million acres) of the state. As settlers moved west, they drained the wetlands for timber and farming, thus eliminating 87% of the state’s original wetlands. Wetland-dependent wildlife species have been severely impacted by this significant reduction in the amount and quality of wetland habitat.
  Wetlands are highly productive. They warm quickly in spring and produce abundant quantities of food for amphibians, reptiles, shorebirds, migrating birds, and waterfowl. Even small sites, much less than an acre, can produce hundreds of frogs, toads, and salamanders. They also provide critical links to other habitat types and wildlife populations.


• Q. Should wetlands be drained to control mosquitoes? Because the Culex mosquito can breed in very small amounts of water, eliminating temporary standing water in plastic containers, discarded tires, or other water-holding containers around one’s property can greatly reduce breeding areas. Any stagnant water in rain barrels, irrigation ditches, clogged gutters, backyard home septic systems, and road-side ditches can serve as breeding sites. The difference between these water-holding places and wetlands is the presence of mosquito-eating predators. Wetlands are home to a host of mosquito-eating beetles, backswimmers, water striders, dragonfly larvae, and more, making wetlands significantly less ideal breeding sites for Culex mosquitoes.


• Q. Can wetlands be drained or are there regulations that protect them?
• Wetlands are afforded protection from draining under the authority of the Ohio Environmental Protection Agency in several sections of Ohio Administrative Code 3745. Under this authority, the hydrology necessary to support the biological and physical characteristics naturally present in wetlands shall be protected to prevent significant adverse impacts on the wetlands. A person can not alter the water levels of the wetland, which also includes groundwater recharge and discharge.

What Is the Status of WNV in Ohio?

WNV was confirmed in Ohio in 2005. Infected mosquitoes, birds, horses, and humans were found in 44 Ohio counties. Therefore, the virus is present throughout the state. Contact your local health department or log on to the web sites listed here for the current status on WNV in Ohio and for more information:

Ohio State University:
prevmed.vet.ohio-state.edu/Extension/WestNile/WNV.htm

Ohio Department of Health:
www.odh.state.oh.us/ODHPrograms/ZOODIS/ZooMain1.htm

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OSU Extension embraces human diversity and is committed to ensuring that all educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, age, gender identity or expression, disability, religion, sexual orientation, national origin, or veteran status.

Keith L. Smith, Associate Vice President for Agricultural Administration and Director, OSU Extension TDD No. 800-589-8292 (Ohio only) or 614-292-1868