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106 Babesiosis

Etiology and Pathophysiology ○ False-positive, false-negative results • Dogs with positive Babesia titers or PCR
recognized
• Sporozoites in tick salivary glands transmitted ○ Tests vary between laboratories. should never be used as blood donors, even
VetBooks.ir • Sporozoites enter red blood cells (RBCs), ○ Not always able to detect all species (check Possible Complications
after treatment.
to dog during feeding (requires 2-3 days)
with laboratory about sensitivity and
where they become merozoites and undergo
specificity)
asexual reproduction.
specific antibabesial treatment can worsen
• Intravascular and extravascular hemolysis occurs. • IFA test > 1 : 64 is considered positive. Prolonged immunosuppressive therapy before
• Secondary immune-mediated destruction of ○ Cannot differentiate species outcome and should not be used in sick,
RBCs and platelets may occur. ○ False-negative results can occur with acute hospitalized dogs.
• Azotemia and proteinuria are presumed to be or peracute disease or severe immunosup-
secondary to glomerulonephritis and are most pression. Recommended Monitoring
commonly seen with B. annae infections but • Monitor hematocrit and platelet count daily
are recognized with increasing frequency in TREATMENT until improvement is seen and then every
association with other Babesia spp. 1-3 weeks until anemia and thrombocyto-
Treatment Overview penia resolve.
DIAGNOSIS It may not be possible to completely eradicate • PCR should be negative 60 and 90 days
the parasite in all cases, but clinical signs usually after treatment if the parasite has been
Diagnostic Overview improve with supportive care and antiparasitic successfully eradicated.
Most dogs with babesiosis have one or more of therapy. The treatment of choice depends on
the following abnormalities: thrombocytopenia, which Babesia species is identified. Currently, PROGNOSIS & OUTCOME
anemia, hyperglobulinemia, and/or splenomegaly. most data are available for treatment of B. canis
Polymerase chain reaction (PCR) assays have and B. gibsoni. • Good prognosis with early diagnosis and
become the primary means of accurately diagnosing treatment; prognosis worsens if treatment
Babesia infections; however, serologic testing can Acute General Treatment preceded by immunosuppressive therapy
help make a presumptive diagnosis of babesiosis • Supportive treatment may require blood • Animals may remain subclinically infected
in cases with low numbers of circulating parasites. transfusion (p. 1169) for animals that are for life.
anemic. • Severely anemic animals may die without
Differential Diagnosis • Intravenous (IV) fluids may be required in supportive care such as blood transfusions or
• Immune-mediated hemolytic anemia animals that are febrile and dehydrated. hemoglobin-based oxygen-carrying solutions.
• Immune-mediated thrombocytopenia • Imidocarb diproprionate 6.6 mg/kg IM once,
• Zinc toxicosis repeat in 7-14 days. Pretreatment with PEARLS & CONSIDERATIONS
• Splenic torsion atropine (0.02-0.04 mg/kg IM or SQ 30
• Ehrlichiosis minutes before imidocarb injection) may Comments
• Leptospirosis reduce cholinergic side effects. Imidocarb • New Babesia species are being identified
• Heartworm disease with caval syndrome appears to reduce morbidity and mortality through molecular techniques.
• Neoplasia: lymphoma or hemangiosarcoma for nearly all Babesia spp but is not effective • Babesia spp can be transmitted vertically and
for the clearance of B. gibsoni. It is the should be considered in puppies with weak-
Initial Database treatment of choice for B. canis vogeli. ness and pallor.
One or more of the following may be identified • Atovaquone 13.5 mg/kg PO q 8h with fatty
in dogs with babesiosis: meal for 10 days plus azithromycin 10 mg/ Prevention
• Regenerative anemia: important to note that kg PO q 24h for 10 days is the treatment • Effective tick control is likely to reduce the
not all dogs with Babesia infections have anemia of choice for B. gibsoni. Results in elimination risk of infection.
• Thrombocytopenia: the most common or reduction of the parasite below the limit • Screening blood donors for Babesia infections
hematologic abnormality in dogs with of detection of PCR testing in ≈82% of can reduce the chances of iatrogenic infections.
babesiosis; platelet counts can be as low as cases. Resistance to atovaquone has been • Screen breeding bitches of at-risk breeds.
< 5000 platelets/mcL. identified. • Avoid blood transmission via transfusion
• Blood smear: identification of Babesia • Clindamycin 25 mg/kg PO q 12h for 14 from infected or previously infected dogs or
organisms (an erythrocyte is ≈8 microns in days as a single agent has been associated blood-contaminated instruments (e.g., shared
diameter) (figure at www.ExpertConsult.com) with clinical improvement but not clearance needles).
○ Small babesiosis: 1-3 micron signet ring of B. gibsoni.
forms • A combination of clindamycin 25 mg/kg Technician Tips
○ Large babesiosis: 3-6 micron single or PO q 12h, metronidazole 15 mg/kg PO q The characteristic features of Babesia make them
paired teardrop forms, but other more 12h, and doxycycline 5 mg/kg PO q 12h identifiable on a blood smear, but they are often
ameboid forms can predominate has been associated with elimination or found in low numbers
• Serum bilirubin: may be increased reduction of the parasite below the limit of
• Hyperglobulinemia: a polyclonal gammopa- detection of PCR testing. A well-defined Client Education
thy is frequently detected treatment course has not been established, In highly endemic areas, use a topical/oral
• Urinalysis: +/− bilirubinuria, hemoglobinuria with treatment times ranging from 24-92 acaricide plus a repellent tick collar.
or proteinuria days.
• Coombs’ test: positive in up to 85% of cases • Concurrent immune suppression should be SUGGESTED READING
• Protein losing nephropathy: has been the avoided whenever possible because it may Birkenheuer AJ, et al: Double-blind placebo con-
primary finding in some cases reduce the ability to clear the infection with trolled trial evaluating the efficacy of an atovaquone
antiprotozoal drugs. azithromycin combination therapy for chronic
Advanced or Confirmatory Testing Babesia gibsoni infections. J Vet Intern Med
• PCR test: only way to determine species or Chronic Treatment 18:494-498, 2004.
subspecies and is more sensitive than blood • Vector control: topical, oral or wearable AUTHOR: Adam J. Birkenheuer, DVM, PhD, DACVIM
smear acaricides EDITOR: Joseph Taboada, DVM, DACVIM

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