Babesiosis

Synonym: Piroplasmosis, "The malaria of the North East"

• An uncommon vector-borne malaria-like parasitic disease.
• Caused by protozoan parasites of the genus Babesia.
• An infection of rodents, cattle, wild animals and man.
• Spread by the bites of ixodid (hard-bodied) ticks which are also the vectors for Lyme Disease (25% of babesiosis patients have both diseases).¹
• Babesia parasites reproduce in red blood cells, forming cross-shaped inclusions (rarely seen).
• There are over a hundred different Babesia species - human disease is usually caused by B. divergens in Europe and B. microti in the Northeast and Midwest United States.

• Babesiosis has some similarities to malaria, but much rarer.
• Seroprevalence estimated at 3-8%.²
• Common in coastal areas in the northeastern United States, especially the offshore islands of New York and Massachusetts.¹
• Incidence and prevalence difficult to know as many cases of Babesiosis are misdiagnosed as malaria where the latter is endogenous and many cases are self-limiting.²

• Consider this infection in splenectomized patient living in the tropics who has had a tick bite and has presented with flu-like symptoms and in whom malaria has been excluded.
• Is being increasingly recognised in patients who receive blood transfusion.²
• The incubation period is typically 1 to 4 weeks, but may be longer.
• Severe symptoms occur in elderly, immunocompromised or asplenic.

Symptoms and signs

• Most cases are asymptomatic
• Those who are symptomatic may have anorexia, fever, fatigue, myalgia
• Examination may reveal jaundice, hepatosplenomegaly, haemolytic anemia, haemoglobinuria and renal failure

Babesia parasites invade the red cells directly, and multiply there - there is no exo-erythrocytic liver stage as required by human malaria parasites.

• FBC may reveal anaemia, thrombocytopenia, atypical lymphocytes and leukopenia.
• Diagnosis depends on microscopy of Giemsa-stained thin and thick films (the intracellular parasite resembles Plasmodia). Several smears may be needed before diagnosis is apparent.
• ESR, bilirubin, LDH and transaminases may be elevated.
• Urine may be dark and urinalysis may show haemoglobinuria and proteinuria.¹
• Immunofluorescence antibody testing or PCR may confirm diagnosis when blood films are negative.
• ELISA IgM for Lyme Disease may also be positive - it is important to treat both conditions where they co-exist.

• Malaria
• Lyme Disease
• Q-fever
• Tularaemia
• Tick borne infections

• ARDS
• Pulmonary oedema - most frequent lung complication and rarely fatal³
• Renal failure
• Multi-organ failure
• Coma

• Supportive care is the only treatment required if the patient is young and otherwise healthy.
• Elderly, immunocompromised patients, and splenectomized patients should be treated with clindamycin IV and quinine PO immediately to avoid acute renal failure.¹
• Azithromycin or trimethoprim-sulfamethoxazole may be tried if the above regime is ineffective.¹
• Consider exchange transfusion in severe cases - to reduce the level of parasitemia.⁴

Mortality rate estimated at 5%.² Poor outcomes are associated with hospitalization for more than 14 days, an intensive care unit stay more than 2 days, male sex and raised WCC and alkaline phosphatase. However, this is based on a very small number of patients and thus must be interpreted cautiously.²

• No vaccine is available
• When outside wear a hat, long sleeves and long pants to cover legs
• Use insecticides to repel or kill ticks
• Check for and remove ticks using tweezers e.g. between the fingers and toes (common areas)
• Use tweezers, and grab as closely to the skin as possible