Seroconversion for Anaplasma phagocytophilum in a Mare with Concomitant Piroplasmosis

In this article, we describe the clinical course of a 3-year-old purebred mare at the third month of gestation found to be positive for Theileria equi (indirect immunofluorescence antibody test and polymerase chain reaction) at the time of the first evaluation. At the clinical examination, the mare showed profound depression, pale mucous membranes, enlarged lymph nodes, febrile temperature, hind limbs edema, and swelling of the right carpus. Anemia and thrombocytopenia were also observed. Because of worsening of clinical signs, treatment with oxytetracycline (6 mg/kg) was started. An improvement of clinical conditions was observed within 12 hours, with a full recovery in 2 weeks. Two months after the first hospitalization, new serological tests showed seroconversion to Anaplasma phagocytophilum. In conclusion, the severity of clinical signs was attributed to the concomitant infections, usually subclinical in Sicily.