Hepatozoonosis in A dog with skeletal and joint involvement: A case report and review of the literature

A 4-5 month-old dog was presented with a one week history of inappetence, lethargy and pain, mostly evident when walking. The dog had been found infested with ticks in a field three weeks prior to presentation. Physical examination findings included poor body condition score, tachycardia, pale mucous membranes, weakness and unwillingness to stand, extreme pain on palpation of all limbs, mild lymphadenomegaly and multiple swollen joints. The dog suffered from moderate anemia and mild thrombocytopenia. Blood smear evaluation revealed that 12% of the neutrophils and monocytes were parasitized by Hepatozoon gamonts confirmed as Hepatozoon canis by PCR and sequencing. Serum biochemistry abnormalities included hypoalbuminemia, hyperglobulinemia, elevated alkaline phosphatase activity and mild hyponatremia. PCR for Ehrlichia canis was negative. Survey radiographs showed evidence of polyostotic involvement of bone cortices with thickening and marked diffuse continuous periosteal proliferation of the humerus, ulna, radius, femur and tibia. Joint fluid from the tarsal joints showed marked increase in WBC, predominantly of neutrophils, some of which parasitized by H. canis. Bacterial cultures, including specific culture for Mycoplasma spp. were negative. The pup was treated with doxycycline, amoxicillin-clavulanic acid and multipledoses of imidocarb dipropionate. During a period of four months the pup's clinical signs were resolved and its hematological and radiographic parameters improved substantially. Despite that, the H.canis parasite load increased. This is an unusual case of canine hepatozoonosis with concurrent periosteal reaction and polyarthiritis.