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Ehrlichiosis is a group of diseases, usually named according to the host species and the type of white blood cell most often infected. Canine monocytic ehrlichiosis is caused by Ehrlichia canis and, occasionally, E. chaffeensis. Canine granulocytic ehrlichiosis is caused by Anaplasma phagocytophilum and Ehrlichia ewingii.

Infections in Animals

Species Affected

E. chaffeensis can infect dogs, coyotes, red foxes, deer, goats and lemurs. Disease has been documented in dogs and lemurs. The primary reservoir hosts are deer. E. ewingii causes disease in dogs, which may also be the reservoir host. E. canis can infect dogs, wolves and jackals, which are also the reservoir hosts.

Incubation Period

The incubation period is usually 8 to 20 days for canine monocytic ehrlichiosis, and 1 to 14 days for equine granulocytic ehrlichiosis. The incubation period for tick-borne fever is 5 to 14 days in naturally infected animals, and 2 to 6 days after experimental transmission in blood.

Ehrlichiosis in cats

There is evidence that cats are susceptible to ehrlichiosis, but documented cases are rare. It is not known whether this disease is under-reported, cats are less susceptible to clinical disease, or cats simply remove ticks during self-grooming and thus are infected less often.

Granulocytic ehrlichiosis was recently reported in a cat infected with A. phagocytophilum in Sweden. The symptoms included fever, anorexia, lethargy, dehydration and tachypnea. Possible ehrlichiosis has also been diagnosed in three cats with fever, anemia, anorexia and loss of condition.

Communicability

None of the organisms that cause ehrlichiosis in animals appear to be directly communicable to other animals or to humans, except by blood transfusion. Animals can introduce infected ticks into the home, increasing the risk of human exposure.