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Wildlife and 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, an infection of the brain and the spinal cord. For the past 4 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 44 states and the District of Columbia. During the year 2000, 21 human cases of WNV encephalitis were reported in the United States, with two deaths, and 56 cases in 2001 with 7 deaths.

In 2002, 3737 human cases of WNV encephalitis were reported with 201 fatalities to date. In Ohio in 2002, WNV was reported in all 88 counties, either in birds, mosquitoes, humans or horses. There were 430 human and 644 horse cases identified. It is expected that WNV will continue to be a disease threat in 2003.

The 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 horse that has the disease.

Continued spread of this disease among wild birds and mosquitoes is anticipated. In Ohio, state, federal, and local agencies are working together to address the potential health risks of WNV to Ohio families and their animals. Public health officials found WNV in crows, blue jays, mosquitoes and horses in 88 Ohio counties during 2002. Once this was known, mosquito control efforts were increased in those areas to protect people from the disease.

Q. Are duck and other wild game hunters at risk for West Nile Virus infections?
A. Because they are outdoors, hunters who go into the field while mosquitoes are still active may be at risk if they are bitten by mosquitoes in areas with West Nile Virus activity. The extent to which West Nile Virus may be present in wild game is unknown at this time.

Q. What should wild game hunters do to protect themselves from West Nile Virus infection?
A. West Nile Virus infections usually peak in late summer and early autumn, before mosquito numbers are reduced by hard freezes. If you hunt during this period, you should wear long-sleeved shirts, long pants, and apply insect repellants to clothing and skin, following the label directions, to prevent mosquito bites.

Q. Will the wetland where I hunt ducks be drained to control mosquitoes?
A. Although mosquitoes are found in wetlands, natural predators help reduce their numbers in all but the wettest years. In order to successfully transmit the West Nile Virus to people, a mosquito must first bite an infected bird and then bite a person. Few mosquitoes feed on both birds and people. The virus-carrying northern house mosquito has been identified as an important threat, and it breeds in stagnant pools around homes. You can reduce their numbers by removing all discarded tires from your property; disposing of tin cans, plastic containers, ceramic pots, and similar water-holding containers; making certain that your roof gutters drain properly; draining water from pool covers; turning over wheelbarrows and plastic wading pools when not in use; and eliminating standing water around your property

Q. Can you get West Nile Virus if you eat wild meat?
A. As far as we know, proper cooking kills West Nile Virus, so there is no danger in eating wild game. The Centers for Disease Control and Prevention (CDC) does recommend that hunters wear gloves when handling and cleaning all game to prevent blood exposure to the bare hands.

Q. Who should hunters contact for information about the risk for West Nile Virus infection in a specific geographic area?
A. Local health departments will know where West Nile Virus has been found in Ohio.

Q. I enjoy watching birds. If I see a lot of crows roosting in an area, should I be concerned about West Nile Virus?
A. No. Seeing crows alive and well is a good indication that the virus is not in your area. Dead crows, however, may indicate the presence of the virus and should be reported to your local health department.

Q. Are crows the only birds affected by West Nile Virus?
A. No, but crows and their relatives (especially blue jays) are most seriously affected by the virus. Large numbers of North American crows and other birds have died from West Nile virus infection. Some exotic birds in zoos died. West Nile Virus has been identified in at least 111 species of free ranging and captive birds found dead in the United States. The public reported most of these birds. Wildlife biologists have also found evidence that some healthy birds have been exposed to the West Nile Virus and have survived.

Q. Will West Nile Virus cause songbird populations to become endangered?
A. While we are still learning about the impact of West Nile Virus on our native birds, it seems unlikely that healthy native songbirds will be greatly threatened. Studies show that many species and individuals survive West Nile Virus infections. Wildlife disease scientists are monitoring the impact of WNV as it moves west across the country.

Q. Are any other wild animals at risk for West Nile Virus?
A. We are still learning about the susceptibility of other species to the West Nile Virus. While it does appear that some mammals are affected, at this time, it appears that crows and members of the crow family, are the most susceptible bird species impacted by West Nile Virus.

Q. Can infected mammals be carriers (i.e., reservoirs) for West Nile Virus and transmit the virus to humans?
A. West Nile Virus is transmitted by infected mosquitoes. At this time, there is no documented evidence of animal-to-animal or animal-to-person transmission of West Nile Virus. Bird-to-bird transmission has been reported in laboratory studies; however, the significance of this under natural conditions is unknown at this time.

Source: Ohio State University