Acute onset of canine granulocytic ehrlichiosis in a young dog (Sponsored by IDEXX)

On May 31, 2010, a 2-year-old 27-kg (59.4-lb) neutered male mixed-breed dog was presented to the University of Missouri Veterinary Medical Teaching Hospital's Community Practice clinic for progressive lethargy and difficulty walking of about 4 days' duration. The morning of presentation, the dog refused to get up to go outside. It was up-to-date on its core vaccinations (i.e., rabies, DA2LPP) and received monthly heartworm preventive medication but no routine ectopic parasite control therapy.

On arrival at the clinic, the dog had to be brought into the building on a gurney. It would stand with reluctance and would walk a short distance with coaxing but appeared ataxic. On examination, the temperature was 39.5 C (103.2 F), the heart rate was 1 30 beats/min., and the respiratory rate was 32 breaths/min. Joint effusion was identified in the right carpus and stifle. It was difficult to evaluate conscious proprioception since the dog was unwilling to stand.

Initial evaluation included a complete blood count, serum biochemical profile, urinalysis, and a SNAP® 3Dx® Test (IDEXX Laboratories). The hematocrit was normal at 42% with total protein of 6.5, but the platelets were decreased at 80.2 x 103 /fjl. The white blood cell count was 8.8 x 103 /ul with a mild lymphopenia of 0.880 xlOVul- On blood smear examination, platelet clumps were not identified, but several granulocytic inclusions compatible with Ehrlichia ewingii or Ana-plasma phagocytophilum were seen. No abnormalities were identified on the serum biochemical profile. The urine specific gravity was well concentrated at 1.067 with a 1 + protein and an inactive urine sediment. The SNAP 3Dx Test result was negative for antibodies to Dirofilaria immitis, Borrelia burgdorferi, and Ehrlichia canis.

Neither the morulae nor clinical presentation can be used to distinguish between canine granulocytic ehrlichiosis and canine anaplas-mosis. However, because Missouri is considered a highly endemic region for E. ewingii but not A. phagocytophilum, a presumptive diagnosis of canine granulocytic ehrlichiosis was made. With the introduction of the SNAP8 4Dx® Plus Test, it is now possible to detect antibodies to E. ewingii. In this case, however, antibody results may still have been negative even had the new SNAP 4DX Plus Test been used given that this dog had an acute onset illness and might not have yet serocon verted.

Treatment was initiated with doxycycline at a dose of 10 mg/kg once daily by mouth. The dog was placed on intravenous fluids at twice maintenance rates; buprenorphine was given for analgesia (0.02 mg/kg subcutaneously every 8 hours). By the next morning, the temperature had normalized, and the dog was willing to stand and walk and eat canned dog food. Fluids were discontinued, and the dog was discharged from the hospital with instructions to continue a 14-day course of doxycycline. Additionally, 50-mg tramadol tablets (xl 0) were prescribed with instructions to administer 1 to 2 tablets by mouth twice daily as needed for pain control. Telephone follow-up about 2 weeks after discharge revealed that the dog's clinical improvement continued, with a return to clinical normalcy within 2 days of hospital discharge. The owner had discontinued tramadol after the first dose. Clinical signs did not recur after discontinuation of treatment. The owner did not return the dog for a recommended repeat complete blood count to re-evaluate the platelet count.