Lyme disease is a problem more commonly thought to occur in our canine and human friends than horses. However, occur it does, and it can have a wide range of signs and symptoms. This disease is a perplexing and confusing one to diagnose and treat in horses, as it has similar clinical signs to many other diseases.
Lyme, Slyme, What’s in a Name?
Lyme disease is a relatively recent disease for horses and humans, as it did not achieve widespread recognition until 30 years ago, when multiple humans–mostly children–were diagnosed with an infectious arthritis in Old Lyme and Lyme, Conn., hence the name. The disease is caused by the bacteria Borrelia burgdorferi, so it is also sometimes called Lyme borreliosis.
The organism B. burgdorferi is not a bacterial infection you can just pick up at any run-of-the-mill, bacteria-laden mini mart. This particular bacteria prefers to be hosted by ticks. As a result, the infection is thought to be transmitted to humans, horses, and dogs solely via a tick bite.
The ticks most frequently implicated in carrying B. burgdorferi bacteria are of the genus Ixodes. This particular genus has approximately 250 species of ticks worldwide (at least 25 of which live in North America). So, yes, Lyme disease occurs worldwide, with cases in humans and other mammals having occurred in Europe, Asia, Africa, and Japan. In North America, Lyme disease occurs most often in the Northeastern and Midwestern United States, but it can occur throughout the country.
To understand how humans and other mammals acquire this infection, you must understand how ticks acquire the bacteria first. The Ixodes species of tick (also known as a deer tick or black-legged tick) has a two-year life cycle from egg to adult, requiring a blood meal at each life stage. The larval form of the tick begins as it emerges from the egg, which is