Detection of a large unnamed Babesia piroplasm originally identified in dogs in North Carolina in a dog with no history of travel to that state

Abstract

Case description: A 12-year-old 46-kg (101.2-lb) sexually intact male Labrador Retriever was evaluated because of lymphadenomegaly. The dog resided in Texas, and its travel history included many southeastern and eastern shore states but not North Carolina.

Clinical findings: Following evaluation of the dog, a diagnosis of stage IVa intermediate- to large-cell lymphoma was made. A cyclophosphamide-hydroxydaunorubicin (doxorubicin)-vincristine-prednisone chemotherapy protocol was initiated. One week after the first chemotherapeutic treatment, a routine blood smear evaluation revealed single and paired intraerythrocytic large piroplasms that resembled Babesia canis. Via molecular testing, the organism was identified as a Babesia sp that had been detected previously in dogs in North Carolina.

Treatment and outcome: The dog was administered imidocarb diproprionate (7 mg/kg [3.2 mg/lb], IM) on 2 occasions (3-week interval). At 1, 4, 15, and 50 weeks after the second treatment, blood samples were analyzed specifically for the North Carolina Babesia sp via PCR assay; the result of each assay was positive.

Clinical relevance: Because of the morphologic similarity of the large piroplasm detected in dogs in North Carolina to B canis, molecular testing of large piroplasms detected in dogs is needed to definitively identify the infective Babesia sp. In the dog of this report, the infection was not eliminated following treatment with imidocarb diproprionate, which may have been a result of the immunocompromised state of the dog or the drug's ineffectiveness against this parasite. If imidocarb diproprionate is ineffective against the North Carolina Babesia sp, treated dogs may act as reservoirs of infection.