The CBC results showed marked leukocytosis with a mature neutrophilia (Table 1). In addition, lymphocytosis (6,286/μl; reference range = 690 to 4,500/μl), monocytosis (4,041/μl; reference range = 0 to
840/μl), and eosinophilia (1,347/μl; reference range = 0 to 1,200/μl) were present. The results of the direct Coombs', antinuclear
antibody, and rheumatoid factor tests were negative. Antibodies against Ehrlichia canis and Borrelia burgdorferi were not detected. The Rickettsia rickettsii titer analyzed by immunofluorescent antibody (IFA) was 1:64, which indicated possible exposure or active infection. Because
the results were negative with the exception of a low titer for R. rickettsii, we suspected hepatozoonosis and planned to perform a muscle biopsy if no improvement occurred with doxycycline therapy.
Additionally, we dispensed deracoxib (50 mg orally once a day) as needed for pain. Within two days, the patient showed improvement
with doxycycline and deracoxib.
DEFINITIVE DIAGNOSIS AND TREATMENT
Two weeks later (55 days after the initial presentation), the dog was presented to our hospital for evaluation of acute stiffness
and sensitivity to touch. The owner said the dog had been moping around and seemed feverish for several days. The patient
had received doxycycline but had not received deracoxib for seven days.
1. A photomicrograph of a skeletal muscle biopsy sample from this patient. There is a developing meront cyst within the host
cell between muscle fibers (hematoxylin-eosin; 40X).
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On presentation, the patient had a rectal temperature of 101 F (38.3 C), weighed 42 lb (19.1 kg), and was sensitive over the
cervical and lumbar spine as well as the right and left axial regions on deep palpation. Proglottids (Dipylidium caninum) were evident in the stool.
Because the dog had not improved with the doxycycline therapy, we proceeded with the muscle biopsy. The patient was sedated
with medetomidine hydrochloride (0.5 ml intravenously) and butorphanol tartrate (0.15 mg/kg intravenously), was given carprofen
(4.2 mg/kg subcutaneously), and was then prepared for surgery. Isoflurane anesthesia was available but not necessary in this
case.
2. A photomicrograph of a skeletal muscle biopsy sample from this patient. Note the focal cluster of mixed mononuclear inflammatory
cells, neutrophils, and some eosinophils associated with cystic rupture and necrotic myofibers (hematoxylin-eosin; 40X).
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Four muscle biopsy samples were obtained by surgical excision—one each from the left biceps, right cervical (trapezius), and
left and right epaxial (longissimus thoracis) areas. Because of the dog's nonresponsiveness to doxycycline and waxing and
waning temperature and pain, we discontinued the doxycycline and initiated trimethoprim-sulfamethoxazole (25.2 mg/kg b.i.d.
for 15 days), pyrimethamine (0.33 mg/kg [one-fourth of a 25-mg tablet] once a day for 15 days), and clindamycin (11 mg/kg
t.i.d. for 15 days) to treat suspected hepatozoonosis.
The next morning, the patient was bright, alert, responsive, and comfortable. We administered praziquantel (three 34-mg tablets
orally) and discharged the patient.
Histologic examination of the muscle biopsy samples revealed protozoal cysts (Figure 1) and myositis (Figure 2) that were consistent with Hepatozoon species infection (Table 2).
Table 2 Results of Histologic Examination of Skeletal Muscle Biopsy Samples*
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The patient continued to receive trimethoprim-sulfamethoxazole, pyrimethamine, and clindamycin for a total of 14 days and
was given deracoxib as needed for pain.
About one week later (Day 70 after the initial presentation), the patient was clinically normal. We initiated treatment with
decoquinate (Decox 6%—Alpharma) at a dose of 1 ¼ tsp once a day over food (¼ tsp/10 lb is approximately equal to 10 mg/kg,
dosing for the highest 10-lb increment) and discontinued all other medications except for deracoxib as needed for pain.
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