Babesia infections occur in dogs and other species, and are
transmitted mainly by ticks. Babesia are protozoal parasites that attack
blood cells, though the severity of illness varies considerably
depending on the species of Babesia involved, as well as the immune
response of the infected dog.
The primary result of a Babesia
infection is anemia as the immune system destroys infected red blood
cells, but Babesia can have other effects throughout the body as well.
Cause
Babesia are a type of microscopic
parasites that infect red blood cells, causing a disease called
babesiosis. There are many species of Babesia, which infect a wide
variety of animals, but there are only a few species that affect dogs.
While our understanding of Babesia is improving, diagnosis and treatment
of Babesia infections remains challenging.
Most Babesia infections are acquired through ticks. Because it is
spread by ticks, Babesia is most common in warmer weather when ticks are
most numerous. Infections are also possible through blood transfusions,
and in the case of one Babesia species (
Babesia gibsoni),
dog-to-dog transmission via bite wounds is thought to be a mode of
transmission. Mothers can also pass Babesia to their pups before birth.
Risk Factors
Babesia infections occur worldwide
in areas where the ticks that carry the disease are common. While any
dog can be infected, young dogs tend to suffer more serious illness.
Greyhounds, pit bull terriers, and American Staffordshire terriers seem
to be most susceptible to infection (Greyhounds with a strain of
Babesia canis, and terriers with
Babesia gibsoni).
Signs and Symptoms of Babesia
Babesia infections
have a wide range of severity: they can be very mild (dogs may not even
show symptoms) or very severe (sometimes fatal). The severity depends
mainly on the species of Babesia involved but also on the immune system
of the dog. Babesia species in the US generally produce milder disease
compared to some of the species found elsewhere. The course of the
disease may be cyclical, with periods of symptoms punctuated by times
where symptoms are absent. Signs and symptoms may include:
- fever
- weakness
- lethargy
- pale gums and tongue
- red or orange urine
- jaundice (yellow tinge to skin, gums, whites of eyes, etc)
- enlarged lymph nodes
- enlarged spleen
In severe cases, multiple organ systems may also be affected
such as the lungs, gastrointestinal tract, kidneys, and the nervous
system. Sometimes dogs suffer a very acute form of Babesiosis and
suddenly go into shock and collapse.
Diagnosis of Babesia
It can be difficult to
confirm a diagnosis of Babesiosis. Blood tests may show a decrease in
the number of red blood cells and platelets (thrombocytopenia),
but this is not specific to Babesia. Blood smears can be examined for
the presence of the Babesia organisms. If they are present, the
diagnosis can be confirmed, but they may not always show up on a smear
(taking blood from a cut on the ear tip or from a toenail can improve
the odds of finding the parasites).
Blood can also be tested for
antibodies to Babesia, though this can sometimes produce misleading
results. Specialized testing can check for genetic material from
Babesia, and while this is the most sensitive test, it is not widely
available and has some limitations as well. Generally, a combination of
lab tests along with clinical signs and history are used to make a
diagnosis.
The diagnosis is further complicated by the fact that dogs infected
with Babesia may also be infected with other diseases carried by ticks,
such as Erlichia, Lyme disease, or Rocky Mountain Spotted Fever
Treatment of Babesia
A variety of drugs have
been used to treat Babesia, with variable success. Imidocarb
dipropionate is used most commonly in the US; diminazine aceturate is
not available in the US but is used elsewhere. Both have a range of
side effects which can be quite severe. A newer combination of drugs,
azithromycin and atovaquone, is promising, though expensive. In severe
cases, blood transfusions may be necessary.
Treatment relieves the symptoms of babesiosis, but it seems that in
many cases, it does not fully clear the parasite from the body. Dogs
may remain infected at a low level, and Babesia can flare up again in
times of stress or reduced immune function. Dogs that have been
diagnosed with Babesia should not be bred or used as blood donors (to
prevent spreading disease).
Prevention of Babesia
Preventing exposure to the
ticks that carry Babesia is the best means of preventing babesiosis.
Check your dog daily for ticks and remove them as soon as possible
(ticks must feed for at least 24-48 hours to spread Babesia). This is
especially important in peak tick season or if your dog spends time in
the woods or tall grass (consider avoiding these areas in tick season).
Products that prevent ticks such as monthly parasite preventatives (e.g., Frontline®, Revolution®)
or tick collars (e.g., Preventic®) can be used; be sure to follow your
veterinarian's advice when using these products. Keep grass and brush
trimmed in your yard, and in areas where ticks are a serious problem,
you can also consider treating the yard and kennel area for ticks.
A vaccine is available in Europe, but is only effective against particular strains of Babesia and is not 100 percent effective.