Babesiosis: Dogs

(Canine Babesiosis)

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Cases of canine Babesiosis may present with a wide variation in the severity of clinical signs, which can range from a hyperacute, shock-associated, haemolytic crisis to an inapparent, subclinical infection. In general, disease is less severe with B. canis infection than with B. gibsoni.

Clinical Signs & Symptoms:

  • Lethargy (weakness / loss of energy)
  • Pyrexia (fever)
  • Mucous membrane pallor
  • Splenomegaly (enlarged spleen)
  • Lymphadenopathy (swollen / enlarged lymph nodes)
  • Haemolytic anaemia (anaemia caused by the destruction of red blood cells)
  • Haemoglobinuria (dark red haemoglobin-containing urine)
  • Icterus (Jaundice – yellowing of the skin and eyes that is caused by too much bilirubin in the blood)
  • Depression
  • Anorexia (loss of appetite leading to weight loss)
  • Tachycardia (rapid heart rate)
  • Tachypnea (rapid breathing)
  • In severe cases: acute collapse, multiple organ failure, and death

Mucous membrane pallor due to anaemia

Laboratory investigations may document low red blood cell and platelet counts, abnormally low blood level of albumin, and bilirublin in the urine.

Initially, the anaemia can be normocytic, normochromic, and nonregenerative, but later develops into macrocytic, hypochromic, regenerative anaemia with reticulocytosis. The anaemia is hypochromic because the reticulocytes have not yet formed their adult concentrations of haemoglobin.

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Definitive diagnosis of infections from Babesia species relies on identification of piroplasms in erythrocytes on stained blood smears (Wright’s stain). However, although numerous organisms may be found in blood smears from acutely infected animals, parasitaemias are usually low and organisms are rarely found in samples collected from chronically infected dogs or asymptomatic carriers.

Serology may be useful in identifying the presence of antibodies to B. canis, which cross-react with those to B. gibsoni, thereby allowing indirect detection of previous infection with either organism.

Note: serologic testing in the diagnosis of Babesiosis has limitations. A positive test result is dependant on antibody response by the host, which may take a long time to develop. In acute infections, dogs with evidence of Babesia species may be serologically negative, necessitating repeat testing using convalescent sera.

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Diagnostic Tests

Indirect fluorescent antibody (IFA) assays to determine IgM and IgG titres to B. canis are available through diagnostic laboratories.

Polymerase Chain Reaction (PCR) of whole blood is generally available but results should be interpreted with caution because the techniques used in different diagnostic laboratories vary. Amplification of related organisms by nonspecific primers can result in false-positive reactions. Conversely, false-negative may also occur if extraction procedures fail to remove PCR inhibitors present in a blood sample. They may also occur if the level of circulating parasitaemia falls below the level of assay detection, due to normal decrease in circulating organisms or temporary suppression of the infection following treatment. To maximize the utility of molecular diagnostics, blood samples should be collected early in the course of clinical disease and before the initiation of chemotherapy, and they should be submitted to experienced diagnostic laboratories with stringent quality control measures in place.

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Imidocarb dipropionate
Diminazene aceturate
Pentamidine isethionate
Supportive therapy.

Dogs infected with B. canis usually respond to treatment with Imidocarb dipropionate at a dose of 6mg/kg I.M. administered twice at 14-day intervals. A higher dose administered once is recommended occasionally but can result in neurotoxicity. Another possible treatment is a single I.M. injection of Diminazene aceturate at a dosage of 5mg/kg.

Babesia gibsoni is considered more difficult to treat than B. canis. Recommended treatment protocols for B. gibsoni involve combining Atovaquone @ 13mg/kg PO q8h for 10 days, with Azithromycin @ 10mg/kg PO q24h for 10 days; Imidocarb dipropionate is not considered effective for treating B. gibsoni.

Babesia species infections can also be treated with Pentamidine isethionate @ 16mg/kg I.M q24h for 2 doses.

Treatment for Babesiosis reduces parasitaemia and supports resolution of clinical signs, although the infection itself may not be eliminated. Dogs diagnosed with Babesia species should be considered to be permanent carriers of the infection.

Note for veterinarians: For a more exhaustive list of potential antiparasitic drugs, consult table 77-3 in Greene’s Infectious Diseases of the Dog and Cat.

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Medical Abbreviations

by mouth
every 8 hours
every 12 hours
every 24 hours

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Currently an effective vaccine is not commercially available to protect dogs against Babesiosis.