Eastern equine encephalitis (EEE)

Recently, the news has reported on several Eastern equine encephalitis EEE cases that have occurred in the US. Until now, these EEE cases have only involved people. And now, two wolf pups at a zoo in MI have died of the infection.

With reports of EEE on the rise, it’s important to understand the truth and risk of this disease for our pets and how to limit their exposure.

Can Dogs and Cats get EEE?

The answer technically is yes, but the reality is it is highly unlikely.  

Before today, EEE had only been found in a few cases; involving very young dogs housed exclusively outdoors in the southeastern part of the United States.


First discovered in 1933, Eastern equine encephalitis virus (EEE) causes a highly lethal mosquito-borne disease affecting primarily horses but also a wide range of mammalian and avian hosts. EEE is distributed throughout the eastern half of North America, with estimated mortality rates in humans and horses reaching 75% and 90%, respectively, according to the Center for Disease Control (CDC).

EEE is Spread by Mosquitos


Eastern equine encephalitis, the disease caused by EEE is spread by the bite of mosquitos. The virus, often, passes through other animals including a variety of mammals and birds. These reservoir animals will carry the virus, but they do not show clinical signs or become ill. When mosquitos feed on these reservoirs, they can then transmit the infection to other horses or susceptible individuals.  

Signs and Symptoms of Infection in Pets


Although pets can on rare occasions contract, this virus and the resulting disease, the signs of the illness are generally so mild that you may not even realize that your pet is infected. A day or two of very mild “flu-like” symptoms involving gastrointestinal upset, lethargy, and loss of appetite may be the only signs. However, as occurs in infected people, the very young, elderly, or adults suffering from a debilitating disease often suffer from a more severe form. In these cases, pets show signs of fever, depression, incoordination, muscle weakness or spasms, seizures, or paralysis; in some instances, it is fatal. 

Treatment for Infected Pets


As this is a viral disease, there is no specific treatment for an EEE infection. Any treatment would be targeted to symptomatic care – managing the symptoms and signs in an individual patient. For those pets with mild symptoms, a full recovery from the infection is likely. 

Transmission of the Virus


Transmission of the virus from an infected dog or cat to a human has not been reported as our pets do not serve as very effective reservoirs for these diseases.

Prevention of EEE in Our Pets (Humans Too)

Unlike for horses, there is no vaccination offering prevention for this virus for people or pets. 

The best way to protect our pet(s) is to guard against mosquitoes! Additionally, and probably more importantly; mosquito control is vital in the prevention of the more commonly seen deadly mosquito-borne infection to our pets, Heartworm disease

Tips to Limit Mosquito Exposure


  • Keep animals indoors during peak periods of mosquito activity (dusk and dawn).
    • All cats should be kept indoors.
    • Avoid exercising your pets during these times, if at all possible. 
  •  Keep screens repaired and free of holes. 
  • Avoid turning on outdoor lights during the evening and overnight. Mosquitoes are attracted to light.
  • Eliminate stagnant or standing water on your property
    • Prevent water overflow from troughs, reduce run-off and pooling of irrigation water, eliminate accumulated water in flower pots or other such containers. Do not overlook those that have become overgrown by vegetation.
    • Dispose of bottles, cans, plastic containers or similar water-holding containers on your property. Turn over plastic wading pools, buckets, pails and feeders when not in use. Turn over wheelbarrows and change the water in birdbaths and stock tanks at least twice weekly; these provide excellent breeding habitat for domestic mosquitoes
    • Remove old tires and in which water can collect. The used tire has become the most important domestic mosquito producer in this country. 
    • Drill holes in the bottom of recycling containers and animal feeders that are left out of doors. Drainage holes that are located on the sides will allow enough water to collect for mosquitoes to breed.
  • Use landscaping to eliminate standing water that collects on your property. Mosquitoes can develop in any puddle that lasts more than four days. 
  • Eliminate piles of decaying organic matter such as leaves, lawn clippings, and manure. 
    • Clean clogged roof gutters on an annual basis, particularly if the leaves from surrounding trees tend to plug up the drains. Roof gutters are easily overlooked and can produce millions of mosquitoes each season.
  • Eliminate water features as sources of mosquito breeding areas
    •  Aerate ornamental pools or stock them with fish. Water gardens can become major mosquito producers if they are allowed to stagnate. 
    • Clean and chlorinate swimming pools that are not being used. A swimming pool that is left untended by a family that goes on vacation for a month can produce scores of mosquitoes. Be aware that mosquitoes can even breed in the water that collects on swimming pool covers/tarps.
  • Apply mosquito repellents approved for use in animals. Read the product label before using, and follow all instructions carefully.
    • For dogs, we recommend the use of Vectra 3D as a mosquito repellent.
    • Do Not apply mosquito repellents to cats – they are sensitive to these medications and serious illness; even death can occur with usage. 

If you have any questions or concerns regarding your pets and EEE or what mosquito repellent is safe for your pet(s), do not hesitate to contact the hospital for advice.


About Brook-Falls
Brook-Falls Veterinary Hospital and Exotic Care is dedicated to providing quality care to all companion pets and exotic animals. Brook-Falls is a Menomonee Falls, WI-based full-service veterinary hospital with an extensive range of comprehensive medical, dental, diagnostic, and surgical services to meet the varying needs of all patients. Brook-Falls Veterinary also offers informational and educational media and seminars for pet owners by way of blogs, digital TV series (Expert Veterinary Television), e-books, whitepapers, infographics, and more.
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