Lyme disease is an infectious disease of humans, dogs, and other domestic and wild animals that can cause a variety of different signs and symptoms. It is caused by a bacterial pathogen called Borrelia burgdorferi . The bacteria normally infect small mammals, especially mice.
Ticks then feed on the mammals and pick up the bacteria when they take their blood meal.
Ticks, being sloppy eaters, then spread the bacteria to the next victim when they bite. The deer tick is the most common tick involved in spreading the disease, but other types of ticks play host to the organism too. Lyme Disease in Dogs A lot of the information you'll find on the Internet might lead you to believe that Lyme Disease is a common and well understood problem in dogs. Most of what we know about Lyme disease in dogs is inferred from information on the disease in humans combined with studies of experimentally infected laboratory dogs, not dogs that caught the disease naturally. The most common signs in dogs appear to be fever, joint pain and stiffness, lameness, depression and loss of appetite.