Lyme disease, which is caused by the bacteria Borrelia burgdorferi and transmitted through the bite of a tick, affects domestic animals and humans. At least 4 known species of ticks can transmit Lyme disease. However, the great majority of Lyme disease transmissions are due to the bite of a very tiny tick commonly called the deer tick, or black-legged tick. The scientific name of the tick species involved on the west coast of the US is Ixodes pacificus; Ixodes scapularis is the species involved elsewhere in the United States (primarily the northeast and the Midwest). It is important to note that ticks do not cause Lyme disease, they merely transmit the bacteria that cause it. However, in some areas, as many as half of adult ticks carry the bacteria.Lyme disease occurs much more frequently in dogs than in cats. When infected, cats may show lameness, fever, loss of appetite, fatigue, or difficulty breathing. Lyme disease can also affect the kidneys, joints, nervous system, and heart. Many cats do not show noticeable signs, despite being infected. The diagnosis of Lyme disease is based on history, signs of disease, laboratory tests, and elimination of other disorders. Additional tests may be necessary depending on which part of the body is affected. Antibiotics are required for treatment in all animals that display signs of Lyme disease. Rapid response is seen in limb and joint disease in most cases, although the signs do not completely resolve in a significant number of affected animals. The infection may persist in spite of antibiotic treatment, and a second round of treatment may be necessary. Additional therapy to help the affected organ systems and signs is also important, especially when the disease affects the kidneys, heart, or nerves. Want to learn more? Read "Lyme Disease in Cats" now.