Researcher Predicts Steady-to-Decreasing Number of West Nile Virus Cases in Animals This Summer

Missouri's mild winter is coming to an end. In addition to spring's warmer temperatures, the change in season means more mosquitoes and a high risk for West Nile Virus infection. A University of Missouri-Columbia researcher who tracks the virus across Missouri said that, although the number of Missouri West Nile cases may decrease this summer, large numbers of birds, mosquitoes and other animals might still carry the virus.


"We expect to see steady to declining numbers of clinical West Nile virus cases this summer," said Gayle Johnson, associate professor of veterinary pathobiology at the MU College of Veterinary Medicine. "Reported cases in horses have significantly decreased. The horses have developed a strong immunity to the disease that can be attributed to vaccination or subclinical infection. The human population still can be exposed to the virus, however, because infected birds, especially crows and blue jays, can still be found in the environment."


The West Nile Virus was first detected in the Western Hemisphere in New York in 1999. The number of West Nile cases in Missouri peaked in 2002 with 676 reported cases in horses, 227 in birds and 168 in people. Last summer, these numbers dropped to less than 20 cases in horses, 116 in birds and 36 in people. Currently, there is no West Nile vaccine for humans.


According to the Centers for Disease Control (CDC), four out of five people infected by the West Nile virus will not develop any symptoms. The elderly are more likely to develop symptoms, which may include fever, headache, body aches and disorientation. People and animals that live in areas with a large mosquito and bird population also have a higher risk of contracting the disease.


"There are a number of steps people can take to protect themselves and their animals, including wearing long-sleeved shirts, long pants and insect repellent when going outside at dusk or dawn," Johnson said. "Put insect repellent on pets and horses, and try to keep them inside during peak hours of mosquito feeding. Contact a veterinarian to learn about the vaccines for horses and mosquito control for dogs. Don't forget to read insect repellent labels. Products that are safe for dogs may be toxic for cats. If people suspect they or their animals have contracted the virus, they should contact a physician or veterinarian or their county health department."


Less than 50 percent of people usually wear insect repellant, and according to the Centers for Disease Control, there have been more than 16,000 cases of human West Nile virus since the virus was first detected in the United States. Johnson recommends that people be alert for dead birds, especially crows and blue jays, as previous research has shown they are a good predictor for the occurrence of human cases.


Source: University of Missouri-Columbia