West Nile Virus Q & A for Pet Owners
Q: What animals are at risk of becoming ill from infection with West Nile Virus?
A: Horses and birds are most likely to suffer severe illness if bitten by a mosquito infected with West Nile virus. Over 20,000 birds representing more than 120 species have tested positive for West Nile virus since 2000. Hundreds of horses have contracted West Nile encephalitis and approximately one out of three have died as a result of the illness. A variety of other animals have had symptoms of neurologic disease and tested positive for West Nile virus. These are rare findings and have included a variety of different types of animals including alligators, sheep, goats, domestic dogs, bats, squirrels and other types of wild rodents.
Q: Are you sure that I don't have to worry about my dog or my cat?
A: Dogs and cats can become infected with West Nile virus by the bite of an infected mosquito, but the good news is that dogs and cats appear to be very resistant to developing disease. A study of dogs in Queens, New York (1999) showed that 5-11% of dogs tested had been exposed to West Nile virus, but none of the dogs' owners reported that their pets had been ill. It is very rare to have dogs or cats die from West Nile virus infection. If a dog or cat develops symptoms of a neurologic disease (confusion, seizures, paralysis, etc.), the pet should be evaluated by a veterinarian as soon as possible and more likely causes of illness should be considered first.
Q: Can infected birds or other animal spread West Nile virus to people?
A: No. West Nile virus is transmitted to people and animals by infected mosquitoes. There is no evidence of the virus being transmitted to people by contact with infected animals.
Q: Are pet birds at risk?
A: The disease risk to a pet bird depends on the amount of exposure the bird has to mosquitoes. Domestic birds kept strictly indoors have minimal risk. Pet birds that are caged or perched outdoors for variable lengths of time are at increased risk.
Q: Is there a vaccine available to protect birds from West Nile Virus?
A: Currently there is no labeled and approved vaccine to protect birds against West Nile virus. Some zoos are conducting experimental trials with avian vaccination to safeguard their collection, especially rare or endangered species. However, the effectiveness of the vaccine and optimal dose and method of administration are not yet known.
Q: What are the symptoms of West Nile Fever in horses?
A: West Nile virus primarily affects the brain and nerves. Therefore, symptoms may include a change in personality, hyperresponsiveness to sound or touch, muscle tremors or twitching, stumbling and falling, or circling. The illness may progress to more serious symptoms such as inability to stand, seizures, and death.
Q: Should infected horses be isolated or quarantined?
A: There is no need to isolate or quarantine a horse that is diagnosed or suspected of being infected with West Nile virus. An infected horse can not transmit the virus to people or other animals. The virus does not persist in an infected horse's bloodstream, so they are not a significant source of virus for mosquitoes.
Q: What is the treatment for West Nile Encephalitis?
A: Since West Nile encephalitis is caused by a virus, there is no specific treatment. More severe cases may need to be hospitalized and receive supportive medical care to control seizures and ensure proper hydration and nutritional intake.
Q: How can I protect my horse from West Nile virus?
A: The most effective and preferred way of reducing a horse's risk of developing West Nile encephalitis is vaccination. Two West Nile virus vaccination products are currently available from your veterinarian or over the counter. Initially, a horse must receive two doses of vaccine given three to six weeks apart to be fully immunized. Then an annual booster must be administered to maintain protection. Due to the longer mosquito season in southern states, your veterinarian may recommend more frequent boosters. Horses that are only vaccinated against “sleeping sickness” (Eastern equine encephalitis, Western equine encephalitis or Venezuelen equine encephalitis) are NOT protected against West Nile virus.
Limiting your horse's exposure to mosquitoes also reduces opportunity for transmission of West Nile virus and other encephalitis viruses. Keep your horse stabled indoors when mosquitoes are most active (dawn and dusk). Fans may also reduce the potential ability of mosquitoes to feed on horses.
Q: Should I apply insect repellents to my pets?
A: In general, this is not a recommended practice. Because dogs and cats are at very low risk of becoming ill from West Nile virus, the potential side effects of the insecticide outweigh the potential benefits. A more significant mosquito-borne disease threat to dogs and cats is heartworm disease. Safe and effective heartworm preventative medications can be obtained through your veterinarian.
Application of insecticides to pet birds or “pocket pets” (hamsters, gerbils) is potentially harmful and should only be done under the advise of a veterinarian. Using insect repellants may help decrease mosquito exposure to horses, but vaccination is the primary method of West Nile virus protection for horses.