MORE TICK-

Disease-causing organisms such as B. caballi and B. burgdorferi are just the beginning of the bacteria and viruses ticks can spread from animal to animal. “People need to become aware of the fact that ticks are very dirty critters. When they bite and transmit a disease, they don’t always transmit just one organism,” says epidemiologist Angela Pelzel-McCluskey, DVM. “We also need to realize that there are often co-infections, and a number of diseases we are not yet identifying. Many people think that the only tick-borne diseases to worry about are Lyme disease or Rocky Mountain spotted fever in humans, not realizing that there are many other diseases out there that they and/or their horses could get.”

Researchers are still working to identify the organisms transmitted by ticks and understand which ones, if any, may cause illnesses—but much remains unknown. “What we have identified at this point is probably very limited; our diagnostics are not very good. We haven’t even developed adequate tools to identify or diagnose what ticks might be carrying,” says PelzelMcCluskey. “In the future we will probably discover more organisms that may be detrimental to human and animal health.”

So far, researchers have identified several other diseases that may affect horses. Fortunately, either they do not make horses seriously ill or they are very rare:

• Tick paralysis. This disease is not caused by a pathogen; rather, it’s a reaction to a neurotoxin found in a tick’s saliva. The primary signs are weakness or incoordination beginning in the hind limbs and progressing throughout the body. It affects many animals, including dogs, sheep and cattle as well as people and horses. The primary culprits are the Rocky Mountain wood tick (Dermacentor andersoni) and