Species which are parasitic to dogs include:
- Ehrlichia canis - most common - causes canine monocytic ehrlichiosis
- Ehrlichia ewingii - less common - causes canine granulocytic ehrlichiosis
- Ehrlichia chaffeensis - rare in dogs
Co-infections with a number of Ehrlichia species is common in dogs as well as coinfections with other tick-borne parasites such as Babesia gibsoni, Anaplasma phagocytophilum, Anaplasma platys, Neorickettsia risticii, Rickettsia massiliae and Borrelia afzelii.
Transmission by Rhipicephalus sanguineus is transstadial, and ticks acquires the bacteria by feeding on an infected dog in either the larvae or nymph form and the tick transmits the disease to another dog as either the nymph or adult form.
After an incubation period of 1 - 3 weeks, an acute febrile phase within the dog lasts for 2 - 4 weeks, during which Ehrlichia multiplies within circulating mononuclear cells and the mononuclear phagocytes within the liver, spleen, and lymph nodes.
The infected cells are then transported in circulation to the rest of the body, with a predilection for the the lungs, kidneys and meninges. Cells infected with Ehrlichia adhere to the vascular endothelium, resulting in vasculitis.
Clinical signs are usually nonspecific and include mental depression, lethargy, mild weight loss, vomiting, diarrhea, and anorexia, with or without hemorrhagic tendencies.
Blood tests usually reveal varying degrees of nonregenerative anemia and thrombocytopenia. Serum chemistry commonly reveals hyperglobulinemia (monoclonal or polyclonal gammopathy), hypoalbuminemia, and low albumin-globulin ratio.
Although a presumptive diagnosis can be made on visualization of the parasite under light microscopy, a definitive test requires molecular identification of the parasite species using indirect immunofluorescence antibody test, PCR testing or western blot.
In many cases, polyarthritis associated with E. ewingii may be self-limiting.
Previous infection does not confer lifelong immunity, and dogs can become reinfected with the same or other ehrlichial species after re-exposure to infective ticks.
- TPV Experience
- Ionita M et al (2013) Molecular evidence for bacterial and protozoan pathogens in hard ticks from Romania. Vet Parasitol Jan 29
- Ehrlichia Research Laboratory, College of Veterinary Medicine, The Ohio State University, Columbus, OH
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- Theodorou K et al (2013) Efficacy of rifampicin in the treatment of experimental acute canine monocytic ehrlichiosis. J Antimicrob Chemother Mar 8
- Fourie JJ et al (2013) Prevention of transmission of Ehrlichia canis by Rhipicephalus sanguineus ticks to dogs treated with a combination of fipronil, amitraz and (S)-methoprene (CERTIFECT(®)). Vet Parasitol 193(1-3):223-228