Babesiosis: For health professionals
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- Key information
- Transmission
- Clinical manifestations
- Diagnosis
- Treatment
- Laboratory testing
- Surveillance
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Key information
Babesiosis is a tick-borne zoonotic disease caused by the protozoan Babesia parasite which infects red blood cells. Babesia microti (B. microti) is the most common cause of babesiosis in North America. It is mainly transmitted by infected blacklegged ticks (Ixodes scapularis). Consult with your provincial or territorial public health authorities to find out where ticks are most likely to be found.
Babesiosis, like most tick-borne disease infections, occurs during the warmer months, but infections can occur throughout the year. Ticks can be active whenever the temperature is consistently above freezing, and the ground isn't covered by snow.
It's critical to remove attached ticks promptly as the risk of transmission of B. microti increases the longer the tick is attached. Infected blacklegged ticks typically need to be attached between 36 to 72 hours to transmit B. microti.
Individuals may not be aware of or remember being bitten by a tick. Therefore, it's important that health professionals conduct a detailed patient history, including history of exposure to ticks, when assessing individuals with signs or symptoms suggestive of babesiosis.
Signs and symptoms can vary from asymptomatic to severe illness. People who are immunocompromised are at higher risk of severe illness and potential relapses, often requiring hospitalization for treatment.
There's currently no vaccine to prevent babesiosis. The best way to prevent tick-borne diseases is to prevent tick bites.
For individuals presenting with signs or symptoms of babesiosis, we encourage health professionals to consider the possibility of other tick-borne diseases, such as:
- Lyme disease
- anaplasmosis
- Powassan virus disease
- tick-borne relapsing fever
Learn more about:
- Ticks in Canada
- How to remove a tick
- How to prevent tick bites
- Provincial and territorial public health authorities
Transmission
Babesiosis is primarily acquired through the bite of an infected tick. The tick known to transmit babesiosis is:
blacklegged tick (Ixodes scapularis), also known as deer tick
Source: Institut national de santé publique du Québec
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Other possible routes of transmission
Internationally, there have been cases of B. microti being transmitted through blood transfusions and organ transplants. However, the likelihood of transmission through transfusion in Canada is low.
While transmission of babesiosis during pregnancy is possible, the risk of passing babesiosis to a baby during pregnancy is considered low.
Learn more:
- Canadian Blood Services
- Héma-Québec
- The Society of Obstetricians and Gynaecologists of Canada: Pregnancy info
Clinical manifestations
The incubation period for babesiosis infection is 1 week to 4 weeks.
The incubation period for blood transfusion related transmission may be up to 6 months.
Symptoms may be absent or range from mild to severe and can be potentially fatal. Symptoms may progress over time, particularly in untreated individuals. Most people will remain asymptomatic or develop mild to moderate symptoms.
Individuals who develop symptoms days or weeks after a tick bite may not remember being bitten or associate symptoms with the bite.
Mild to moderate babesiosis infection (parasitemia of less than 4%) may present with gradual onset of symptoms which typically include:
- fever
- fatigue
- malaise
- chills
- sweats
- myalgia
Clinical manifestations associated with the following conditions may also be seen:
- hemolytic anemia
- thrombocytopenia
- splenomegaly
- hepatomegaly
Less common clinical manifestations may include:
- nausea
- headache
- dry cough
- loss of appetite
- scleral icterus or jaundice
Severe disease (parasitemia of 4% or greater) may present with similar manifestations but with greater intensity with progression to more severe or prolonged symptoms or complications.
Clinical manifestations of severe disease may include:
- gastrointestinal symptoms (such as nausea, vomiting, diarrhea)
- hemodynamic instability
- pulmonary, renal, and hepatic compromise
- altered mental state
Complications of babesiosis may include:
- acute respiratory distress syndrome (most common)
- severe anemia (warm autoimmune hemolytic anemia)
- disseminated intravascular coagulation
- congestive heart failure
- renal and liver impairment
- septic shock
- splenic infarct or rupture
- persistent or relapsing disease
- death
Risk factors for severe disease may include:
- asplenia
- advanced age
- compromised immune system
Rashes
While a cutaneous rash can occur at the site of infection, it is uncommon and does not have the appearance of an erythema migrans rash as seen in Lyme disease. The presence of an erythema migrans rash in a patient would be suggestive of an infection or co-infection with Borrelia burgdorferi (the bacterium that causes Lyme disease).
Hypersensitivity reaction to a tick bite
Individuals may develop a hypersensitivity reaction within 24 hours of a tick bite. A hypersensitivity reaction will produce an erythematous skin lesion less than 5 cm in diameter which doesn't expand and usually recedes within 48 hours.
Hypersensitivity skin reactions shouldn't be confused with erythema migrans as seen in Lyme disease. Individuals who develop erythematous skin lesions which haven't resolved within 48 hours should be reassessed to determine whether an erythema migrans rash has developed.
Diagnosis
Babesiosis should be considered in individuals presenting with:
- history of tick exposure
- clinical signs and symptoms that are consistent with babesiosis
Laboratory testing can be conducted when appropriate.
In cases of unexplained exposure, health professionals should inquire about recent blood transfusions and organ transplants.
History of tick exposure
A history of tick exposure includes:
- a recent tick bite or
- living in or having recently visited a potential blacklegged tick habitat
While a known history of tick exposure, particularly to blacklegged ticks, helps with the diagnosis, absence of a history of exposure doesn't rule out babesiosis. Individuals may not recall a tick bite because ticks are tiny, and their bites are usually painless. Furthermore, blacklegged ticks can be found outside currently identified risk areas.
A tick may carry multiple pathogens and transmit them to humans via a single bite. Therefore, while investigating babesiosis, health professionals should consider infection or co-infection with other tick-borne diseases, such as:
- Lyme disease
- anaplasmosis
- Powassan virus disease
- tick-borne relapsing fever
Consider consultation with an infectious disease specialist when suspecting co-infection.
Treatment
Most symptomatic cases of babesiosis can be managed successfully with timely diagnosis and appropriate treatment.
Treatment of babesiosis typically involves a combination of two prescription medications. The typical combinations are:
- atovaquone and azithromycin or
- clindamycin and quinine
Health professionals should base the clinical management of babesiosis on the presenting illness and a person's individual risk factors for severe disease. Consultation with an infectious disease specialist is recommended when considering the treatment and management plan.
For people without risk factors and mild to moderate symptoms
Treatment is not typically indicated until a diagnosis is confirmed by laboratory testing. Treatment duration is usually 7 to 10 days and clinical improvement should be observed within a few days. Symptoms usually resolve within 1 to 2 weeks, although people may have symptoms for up to 3 months.
For people who have risk factors and present with mild to moderate symptoms or symptoms of severe disease
Treatment should begin immediately. These patients typically require hospitalization for treatment, and they should continue to be monitored for complications or relapsing disease following treatment. They may need intravenous treatment and supportive care, such as respiratory support, dialysis, vasopressors, exchange transfusions or blood transfusions.
For people who have received treatment and still have persistent symptoms of babesiosis
Co-infections with other tick-borne diseases should be considered.
Laboratory testing
Laboratories that employ conventional diagnostic assays and interpretive criteria should be the only laboratories conducting diagnostic testing. Health professionals should send samples to their provincial and territorial laboratories. They will coordinate with the National Microbiology Laboratory or the National Reference Centre for Parasitology, when necessary.
Samples to collect for patients being investigated for babesiosis include:
- acute serum or whole blood sample: collected as early as possible after symptom onset
- convalescent serum sample: collected 2 to 6 weeks after the acute sample
Laboratory tests for babesiosis include:
- detecting Babesia species DNA in whole blood specimen by amplification of specific targets by polymerase chain reaction
- identification of Babesia via Giemsa staining of thin blood smears
- immunofluorescent assays detecting both IgG and IgM antibodies to prior infection
All tests may be negative in patients who received early treatment.
Laboratory testing should be done through a licensed and accredited public health laboratory.
Surveillance
Babesiosis is a nationally notifiable disease. Nationally notifiable diseases are infectious diseases that have been identified collectively by the federal, provincial and territorial governments as priorities for surveillance and control efforts.
The national notification system receives cases reported through provincial and territorial public health authorities. Both the confirmed and probable cases of babesiosis are reportable. The national case definition for babesiosis is used to classify cases reported to the Public Health Agency of Canada.
Provinces and territories have their own legislation for reporting of priority infectious diseases. Please consult provincial or territorial public health authorities for reporting requirements in your jurisdiction.
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