Canine babesiosis is a disease caused by the intraerythrocytic
protozoan parasites Babesiacanis and Babesiagibsoni.
Babesiosis is transmitted by ticks to susceptible canine hosts.
Rhipicephalussanguineus is the most common tick
vector in the United States.
Splenectomized dogs, immunocompromised dogs and young dogs
between the ages of two and eight months are most susceptible
to infection. Canine babesiosis occurs worldwide. Within
the United States
it is most common in the southeast. Although canine babesiosis
is considered uncommon in the U.S.,
it is of clinical significance due to its morbidity and mortality.
It is an important differential when history and clinical
signs are consistent with infection and other more common
diseases have been ruled out.
Pathogenesis and Clinical Signs
Animals are affected after an infected tick bites and feeds
on a susceptible host for a minimum of three days. When the
babesia organism is introduced into the host, it attaches
to erythrocyte membranes and is endocytosed. Hemolytic anemia
and hypotensive shock are typical clinical syndromes of infection.
Hemolytic anemia results from direct erythrocyte damage by
the parasite, and both intravascular and extravascular immune-mediated
destruction of red blood cells. Infection can produce thrombocytopenia,
the mechanism of which consists of immune-mediated destruction
and sequestration in the spleen. Physical examination reveals
splenomegaly, lymphadenomegaly, fever and less frequently,
lethargy, vomiting, hematuria, and icterus. Hypotensive shock
results from the release and production of vasoactive amines
and cytokines which produce vasodilation. It most often occurs
in puppies with the peracute form of the disease. Death may
occur and is seen most often in
B. gibsoni infections and in puppies affected with
B. canis and B.gibsoni. Chronic infections, subclinical
carrier states and atypical canine babesiosis may also occur.
Infection with B. canis or B. gibsoni is definitively diagnosed
by demonstration of the parasites on red cells. Blood smears
may be stained with Diff-Quik or preferably Wrights
or Giemsa stain. Stained smears demonstrate 2.4mm x 5.0mm,
piriform-shaped, intraerythrocytic parasites which are usually
paired (B. canis), or 1.0mm x 3.2mm pleomorphic, single
to multiple, intraerythrocytic organisms (B. gibsoni).
Blood samples collected from the peripheral capillary beds
in the tip of the ear or the nail bed are most likely to reveal
parasites. The feathered edge and monolayer of the smear
should be closely examined for parasitized red blood cells.
Practitioners may read their own smears and/or submit them
to a nearby veterinary diagnostic laboratory. Babesia organisms
may be a challenge to find in chronic infections or in asymptomatic
carrier animals. Submission of a blood sample for serologic
testing is an important adjunct diagnostic tool to help rule
in the disease particularly when titers are significantly
elevated. Serologic testing is available at Louisiana Veterinary
Medicine Diagnostic Laboratory and at the University of Illinois
Laboratories of Veterinary Diagnostic Medicine. Serologic
tests which are currently available include the indirect fluorescent
antibody test (IFA), which is used most frequently, and a
more recently developed dot ELISA test.
The most effective drugs used in the treatment of canine
babesiosis include diminazeneaceturate, phenamidineisethionate,
and imidocarbdipropionate which are not available or approved
for use in the United States.
Treatment of canine babesiosis in the U.S.
is therefore mostly aimed at treating symptoms. The majority
of babesia cases diagnosed in dogs in the U.S.
are caused by the less virulent strains of B. canis
and dogs frequently recover from these infections naturally
with supportive therapy. Clindamycin has been successfully
used to treat canine babesiosis and may be considered in refractory
or more severe and virulent infections.
Prevention of canine babesiosis is mostly aimed at controlling
the vector. It is an important aspect since treatment is
not always successful. The environment should be treated
to decrease tick numbers, dogs should be treated to control
tick infestations, and ticks should be removed from parasitized
animals as quickly as detected.
Recently, a vaccine which minimizes the severity of infection
was developed. The vaccine is reported to be 70 to 100% effective
in diminishing the pathologic effects which typically ensue
upon infection. The vaccine is currently available in Europe
where canine babesiosis is more common life-threatening disease.
Blood transfusion poses a significant risk to recipient animals,
therefore it is recommended that donor animals be tested for
infection with babesia organisms. Splenectomy prior to testing
significantly improves the likelihood of finding organisms
in a blood sample from an infected donor.
It is important for practitioners to keep less common diseases
such as Babesiosis in the list of differential diagnoses for
acute hemolytic anemia, shock and icterus. It is equally
important that practitioners know how to diagnose diseases
which are less common and that they be diligent in their efforts
to find a cause for disease when the more common possibilities
have been ruled out. Animals are traveling more often today
than ever before, making exotic diseases more common and more
likely to spread to new areas. Canine babesiosis is an important
diagnostic consideration which practitioners should not neglect
-by Kristen Ripberger, Class of 2000
-edited by Armando Irizzary, DVM