Similar to the other diseases on this list, hepatozoonosis most commonly occurs in the Southern and Southeastern U.S. However, instead of being transmitted by a tick bite, this protozoan is transmitted when a dog ingests a tick!
There are two different species:Hepatozoon americanum (transmitted by the Gulf Coast tick) andHepatozoon canis (transmitted by the brown dog tick). In both cases, the tick carries the protozoan and will then release it into a dog’s gastrointestinal tract once the tick has been ingested.
This results in swollen lymph nodes, bleeding problems, and problems associated with the liver, lungs, and pancreas. In the case ofH. americanum, dogs will develop large, painful muscle cysts and inflammation whereas those infected withH. canis will not.
While theBabesia protozoan invades red blood cells, theHepatozoon species will invade white blood cells. In some cases, this can be seen on a microscope slide. Blood work values may appear abnormal such as a low red blood cell count, a high white blood cell count, low blood protein, and increased muscle enzymes. Definitive diagnosis is achieved via PCR testing and sometimes muscle biopsy.
canis can be quickly treated with one or two imidocarb injections and oral doxycycline. However,H. americanum cannot be completely cured. It is initially treated with clindamycin, pyrimethamine, and trimethoprim-sulfa. After that, long term treatment with decoquinate is necessary for a minimum of two years though maybe lifelong in most cases.