Do I need to worry about mosquitos and my horse?
YES YES YES YES YES. Mosquitos are not only annoying, they can kill your horse. And in a particularly horrible manner. You may have hear of EEE, WEE, and WNV. Eastern Equine Encephalitis, Western Equine Encephalitis, and West Nile Virus. There is also VEE, Venezuelan Equine Encephalitis, which is primarily found in South America but closely related to EEE and WEE. To give you an idea of how horrible these diseases are, encephalitis literally means swelling of the brain.
As the name suggests, EEE is found on the east coast, and WEE on the west coast. West Nile is everywhere. EEE and WEE are usually near coasts, but they can be found inland as well.
These are all a type of virus that uses birds and mosquitos to flourish. The virus lives in birds, and is transmitted from bird to bird via mosquito. These bird to bird mosquitos typically just feed on birds. However, there are mosquitos that will take a blood meal from an infected bird, let’s say with EEE, and then take a blood meal from a horse. Tah-dah, the virus is now in the horse. Another interesting tidbit about these viruses….. they are zoonotic, meaning they can also infect humans. But, there is not enough EEE or WEE or WNV in a horse for an infected horse to be a danger to other horses or humans. These diseases still need to travel from bird to mosquito to horse or human.
Let’s start with EEE, the nastiest of these viruses. After exposure to EEE, the virus hangs out in your horse for one to three weeks. Then, all of a sudden, your horse has a raging fever, it could be as high as 106. He displays neurological problems, he can’t walk well, he wanders aimlessly, his head is suddenly very heavy, he might not be able to swallow, he is weak and won’t eat, and he will eventually become paralyzed. EEE has the highest death rate, somewhere around 85%. Horses that succumb usually do so within a few days of symptom onset. Horses that survive often have permanent neurological issues.
Moving on to WEE, the signs are similar. With this particular strain of virus, the mortality rate is somewhere around 40%. Still horrible, and surviving horses often have long term problems.
WNV has a mortality rate of around 35%, but the neurological problems can persist in surviving horses.
Any time your horse shows signs of neurological problems, call your Veterinarian. It might be something as subtle as a droopy lower lip or ears, or more obvious like hind leg weakness, balance issues, falling, twitching, seizures, head pressing, or hypersensitivity and restlessness.
There are no cures for any of these mosquito borne diseases. Horses can be supported and made more comfortable, but that’s all. HOWEVER…. all of these diseases have safe and effective vaccines available. Typically, initial vaccinations need to be boosted a few weeks later, and after that, every six or twelve months.
So… know the signs, vaccinate your horse, and carry on. And also make sure your farm is not mosquito friendly! For tips on making the barn area mosquito un-friendlly, read this article.