The clinical manifestations of babesiosis range from subclinical
illness to fulminating disease resulting in death or prolonged convalescence.1-3 Symptoms
begin after an incubation period of 1 to 6 weeks from the beginning
of tick feeding. The unengorged I. scapularis deer
tick is only about 2 mm in length, so there is often no recollection
of a tick bite. Typical symptoms include intermittent
temperature to as high as 40°C (104°F) and one or more of the following:
chills, sweats, myalgia, arthralgia, nausea, and vomiting. Other
less common clinical manifestations are emotional lability and depression,
hyperesthesia, headache, sore throat, abdominal pain, conjunctival
injection, photophobia, weight loss, and nonproductive cough.
While the number of symptoms appears to be similar in children
and adults, the duration of symptoms and frequency of hospitalization
is greater in adults over 50 years of age. Adults and children who
are immunocompromised, especially those who lack a spleen or who
have HIV or malignancy, are at increased risk of life-threatening
disease.9,10The overall babesiosis mortality rate
is about 5% but as high as 21% in highly immunocompromised
hosts. B. microti may be co-transmitted with the agents
causing Lyme disease and human granulocytic anaplasmosis. Patients
experiencing babesiosis and Lyme disease coinfection generally have
an increase in the number of symptoms and a longer duration of illness
compared with patients experiencing Lyme disease alone.11 Asymptomatic
babesial infection may persist for months or even years and may
result in disease recrudescence or transmission of babesiosis through
blood donation.12