Babesia rapidly emerging parasite in the United States

Babesia rapidly emerging parasite in the United States

Nov 01, 2002

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Signalment Canine, Basset Hound, 9 weeks old, female, 12 lbs.

Clinical history The puppy presents for lethargy, sleeping excessively, and pale mucous membranes. One tick has been removed.

Physical examination The findings include rectal temperature 104.5° F, heart rate 135/min, respiratory rate 40/min, pale mucous membranes, normal capillary refill time, and normal heart and lung sounds. There is an enlarged spleen detected on abdominal palpation.

Laboratory results A complete blood count and serum chemistry profile were performed and are outlined in Table 1, p. 15S.

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Radiographic review: Survey thoracic and abdominal radiographs were done.

My comments: The thoracic radiographs are normal. The abdominal radiographs show an enlarged spleen.

Ultrasound examination: Thorough abdominal ultrasonography was performed. The puppy was positioned in dorsal recumbency for the ultrasonography.

My comments: The liver is enlarged and shows decreased homogeneous texture. No masses noted within the liver parenchyma. The gall bladder is mildly distended, and its walls are not thickened or hyperechoic. The spleen is greatly enlarged and shows inhomogeneous texture - no masses noted. The left and right kidneys are similar in size, shape and echotexture.

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Each kidney shows inhomogeneous texture. No masses or calculi were noted in either kidney. The ureter for each kidney is prominent and contains echogenic debris - a normal finding in this age of puppy. The urinary bladder is distended with urine and contains some urine sediment material - no masses or calculi noted. The left and right adrenal glands are similar in size and shape. The stomach, small intestines, and colon are normal. The pancreas shows inhomogeneous texture. One normally can expect to see small amounts of free fluid accumulated within the abdominal cavity of this age of puppy - a completely normal finding.

Case management: In this case, acute babesiosis is the clinical diagnosis. This case presentation is most typical of a puppy with acute babesiosis. Attending veterinarians have to collect blood and look at the blood films well before any whole blood transfusion is done.

Do you think of and do this? The preferred treatment for babesiosis is imidocarb at 6.6 mg/kg subcutaneously or intramuscularly every two weeks for three times and not clindamycin. Because of the low platelet count, I would use steroid therapy for a few days. Otherwise, supportive care and monitoring are needed.

Review on canine babesiosis An excellent review of canine babesiosis was provided by Dr. Macintire of Auburn University at the last ACVIM Forum - Macintire DK: babesia gibsoni - an emerging disease. Proc ACVIM Forum 20:474-475, 2002. The review follows:

Babesia species are infectious organisms that affect red blood cells of vertebrate hosts. Babesia canis and Babesia gibsoni currently reside in the United States.

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These organisms have traditionally been differentiated based on their appearance in stained blood smears. Babesia canis organisms are larger and appear as bilobed piriform organisms that often occur in pairs and are approximately 4-5 um in length. Babesia gibsoni organisms are smaller (1-2.5 um in diameter) and appear as round to oval or ring-shaped organisms, usually single, in red blood cells. Babesia canis is endemic in Europe, southern Africa, Asia and the Americas.

Subtypes There are three subtypes of Babesia canis: B. canis canis, B. canis vogeli and B. canis rossi. These strains differ in virulence, geographic location and tick vector, but are identical in appearance.

In the United States, the most common strain is B. canis vogeli, which is the least pathogenic form. Although severe hemolytic anemia, thrombocytopenia and life-threatening disease have been reported in young dogs, heavily parasitized dogs and dogs transfused with infected blood; most dogs infected with B. canis vogeli in the United States are subclinical carriers.

Although not highly pathogenic, the B. canis vogeli organism appears to be endemic in the southeastern United States, particularly among Greyhounds.

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A recent study differentiating the three subspecies of Babesia canis by polymerase chain reaction and restriction enzyme analysis suggests that they may actually be closely related but distinct and separate species. The most pathogenic type, B. canis rossi, is endemic in South Africa. Babesia canis canis is found in Europe and parts of Asia and is considered intermediate in pathogenicity.

Small Babesia organisms infecting dogs were first identified as Babesia gibsoni in dogs and jackals from India in 1910. This parasite is now considered endemic among dogs in northern Africa, the Middle East and southern Asia. In 1991, 11 dogs from Southern California were diagnosed with a small Babesia organism and developed severe hemolytic anemia and thrombocytopenia.