Breed: Pitbull Terrier
A two-year-old male Pitbull terrier from Texas was obtained by a rescue organization in New York. Shortly after he was acquired, his care givers saw that he was lethargic and had pale mucus membranes. The patient was initially admitted to a specialty practice emergency service. Blood was collected and submitted for a CBC.
Patient reference range units
HCT 20 38-56 %
MCV 94 59-76 fl
MCHC 30 32-39 g/dl
Retic 471 10-110 K/ul
Retic % 22
WBC 8,500 4.9 – 17.6 /ul
Neutrophils 4,250 2,940 – 12,670 /ul
Lymphs 1700 1060 – 4950 /ul
Monos 425 130 – 1150 /ul
Eos 2,125 70 – 1490 /ul
Platelets 45,000 140 – 490 K/ul
Upon examination of a blood smear, small oval shaped structures, approximately 0.5 – 2 micron in size, were noted within several erythrocytes. The structures revealed a very small, oval shape with a basophilic, eccentric nucleus and a small amount of clear to light basophilic cytoplasm.
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Microscopic Description and Comments:
The structures were consistent with the trophozoite stage of a hemic protozoal organism known as Babesia. There are many different species of Babesia, but only a few that infect dogs and even fewer that are recognized in North America.
Via the morphology of these organisms Babesiosis was concluded. Based on the organism’s size, breed and the patients travel history, Babesia gibsoni was considered most likely. Babesia gibsoni in the US is most commonly seen in pitbulls, particularly those that have been used in illegal dog fights.
Canine babesiosis has a world-wide distribution. In the US, endemic species include Babesia gibsoni and Babesia conradae. These are both small sized babesia species but so far, B.conradae has been described only in California. Babesia canis vogeli is also endemic, but this species has much larger sized trophozoites.
Babesia can be transmitted by ticks, dog bites (with wound exposure to infected blood as would likely occur in fighting dogs), transplacental infection or a blood transfusion.
Clinical signs associated with babesiosis are variable ranging from asymptomatic to demonstrating signs associated with anemia. Although the anemia resulting from Babesia gibsoni infection is usually not life threatening, a secondary IMHA can manifest with infection and this can sometimes result in significant hemolysis. The IMHA and the anemia will not usually resolve with treatment for Babesia only, it usually requires concurrent treatment for IMHA.
Thrombocytopenia is a common finding in patients with B. gibsoni but spontaneous hemorrhage or a thrombocytopenia associated coagulopathy are not expected features of this disease.
Although Babesia was readily diagnosed via blood smear exam in this patient, other diagnostics include serology and PCR. PCR is the most sensitive and specific assay, allowing for speciation.
Babesial disease in dogs infected with B. gibsoni and B. conradae can usually be effectively treated with Azithromycin and Atovaquone. The treatment chosen is usually determined by the species of Babesia infecting the patient, as well as other factors including cost and the patient’s tolerance of the medication.
This patient was transferred to a general practice for follow up treatment. Approximately a month later, his veterinarian was contacted and indicated that the dog was doing very well.
A.J.Birkenheuer: Babesiosis, In Infectious Disease of the Dog and Cat: Greene, 4th ed., Ames, Wiley, 2011 pp 771-784.
Peter Irwin: Babesia and Cytauxzoonosis, In Arthropod-Borne Infectious Diseases of the Dog and Cat: editor – M. Day, 2nd ed., Boca Raton, CRC Press, 2016 pp 77-96.