VACCINATIONS FOR ALL HORSES

The core vaccines for horses— those recommended for every horse— protect against the following diseases:

• eastern/western equine encephalomyelitis— brain and spinal cord inflammation caused by alphaviruses that are usually transmitted by mosquitos. Two forms that most commonly affect horses are eastern equine encephalomyelitis (EEE), which is fatal in about 90 percent of cases, and western equine encephalomyelitis (WEE), which has a mortality rate of about 50 percent.

• rabies— a fatal viral disease of the central nervous system. Rabies is most often spread through saliva from the bite of an infected animal. In the United States, reservoirs of the virus exist in raccoon, skunk, fox and bat populations. Rabies is a public health threat, which means that veterinarians are required to report all cases.

• tetanus— paralytic disease characterized by spasms of the voluntary muscles, especially of the jaw. Caused by the neurotoxin of Clostridium tetani, a spore-forming anaerobic bacterium. C. tetani is ubiquitous in the soil, putting all horses at risk of exposure.

• West Nile encephalitis— caused by a flavivirus transmitted by mosquitoes. West Nile virus can infect birds, horses, humans and other mammals. Usually, infection with the virus causes little or no illness, but sometimes it triggers swelling of the brain (encephalitis) that produces limb weakness, muscle fasciculation (twitching), incoordination, behavioral changes, paralysis and recumbency. In severe cases, West Nile encephalitis can lead to coma and death.

For maximum effect against insect-borne diseases, initial vaccine series and boosters need to be completed three to six weeks before bug season. If you’ve been putting off spring vaccinations until the weather warms up, you’re already behind the ideal schedule.