West Nile Virus Found In Arizona Dog

2019 has been a big year for West Nile virus (WNV) in Arizona. There have been 300 mosquitoes that tested positive through August 27th. According to a press release from the Arizona Veterinary Medical Association, “There are currently 135 human WNV cases statewide (including 9 deaths) and 21 asymptomatic blood donors, the majority in Maricopa County. Approximately 60% of all human WNV cases nationally have been reported just from Arizona. One horse, one sentinel chicken flock, one grackle, and one dog have also tested positive for WNV in Arizona this year.” The dog was a 5 year old German Shepherd dog that developed neurological signs, problems walking, head tilt and exaggerated movement of the legs. The dog was tested for multiple diseases that cause meningitis including valley fever, tick fever and several other tick diseases. All of those tests were negative. The dog is responding to treatment with a 50% improvement in his neurological status.

WNV causes a fatal encephalitis (inflammation of the brain) in humans, birds and horses. This is the first case of WNV causing encephalitis in a dog in 15 years. Many WNV infections in dogs are transient with mild clinical signs. Cats can also be infected with WNV. Like dogs, the symptoms are usually a mild fever that resolves without further treatment. The virus is transmitted by mosquitoes which is why the Centers for Disease Control monitors mosquitos all over the country. According to the Arizona Department of Health Services, ‘Humans, horses and other mammals do not pass the virus on to other biting mosquitoes.”

To prevent you and your pets from becoming infected with WNV, avoid mosquitoes. Use repellents that are specifically designed for your pet. Although DEET containing products work well for humans, they are not recommended for dogs or cats because they may lick it off their fur and skin which can be toxic. Also, remove standing water from the environment to prevent mosquitoes from laying eggs.


-‘Zoonotic Disease Alert: West Nile Virus in a Dog’, Arizona Veterinary Medical Association email alert, August 28, 2019.

-‘West Nile Virus’, Arizona Department of Health Services, www.azdhs.gov.