Babesiosis Clinical Presentation

Updated: Jul 31, 2018
  • Author: Burke A Cunha, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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The history of babesiosis includes fever and chills. Patients with babesiosis have symptoms similar to those of malaria. Symptoms are related to the degree of red blood cell (RBC) parasitemia. The spectrum of disease manifestation is broad, ranging from a silent infection to a fulminant malarialike disease that results in severe hemolysis and, occasionally, death.

In the United States, infection with B microti in otherwise healthy individuals generally remains subclinical; however, symptomatic infection is common in asplenic patients, older patients, and patients with underlying medical conditions, including human immunodeficiency virus (HIV) infection. Because bovine babesiosis due to B divergens and B bovis in Europe mostly occurs in patients who are asplenic, such infections are generally clinically overt and frequently fatal.

Patients typically report a history of travel to an endemic area between May and September. This is the period during which the Ixodes tick is in its infectious nymph stage. Because the nymph, the primary vector, is only 2 mm in diameter when engorged, most patients do not recall a tick bite. The incubation period after the tick bite is usually 1-3 weeks but may occasionally be as long as 9 weeks.

Initial symptoms begin gradually and are nonspecific. Common symptoms include the following:

  • Malaise

  • Fatigue

  • Anorexia

  • Shaking chills

  • Fever – This may be sustained or intermittent, and temperatures may be as high as 40°C

  • Headache

  • Myalgias

  • Arthralgias

  • Nausea

  • Vomiting

  • Abdominal pain

  • Depression and emotional lability

  • Dark urine

  • Photophobia, conjunctival injection, sore throat, or cough – These are less common symptoms

  • Neck stiffness

  • Altered sensorium

  • Shortness of breath

In a series of 139 patients who were hospitalized with babesiosis in New York, the following were the most common symptoms [14] :

  • Fatigue, malaise, and weakness (91%)

  • Fever (91%)

  • Shaking chills (77%)

  • Diaphoresis (69%)

In some untreated patients, symptoms of babesiosis may last for months. Subclinical infections may spontaneously recrudesce after splenectomy and after immunosuppressive therapy.


Physical Examination

Physical findings may vary, depending on the severity of disease. Most patients with babesiosis have few, if any, physical findings. Fever is generally present. A minority of patients have jaundice and splenomegaly.

Hepatomegaly may be noted. Petechiae may be present in a few patients. Ecchymoses have been noted occasionally. A rash similar to erythema chronicum migrans has been described, but this probably represents intercurrent Lyme disease. Slight pharyngeal erythema may occur. Babesiosis has been associated with shock and acute respiratory distress syndrome (ARDS). Rigors and altered mental status may be noted.



The complications of babesiosis are related to the degree of intravascular hemolysis. The main complications include jaundice, hemoglobinuria, and potential renal failure. The following may be observed:

  • Shock

  • Death

  • Relapse

  • Spontaneous splenic rupture [16, 17]

Patients who have undergone splenectomy are unable to clear infected RBCs; this inability results in higher levels of parasitemia, eventually leading to hypoxemia and subsequent risk of cardiopulmonary arrest.

In severe cases, damage to RBC membranes, decreased deformability, and cytoadherence to capillaries and venules lead to pulmonary edema and respiratory failure. These respiratory problems begin after treatment has been initiated, at a time when intraerythrocytic death of parasites has been postulated to cause sensitivity to endotoxin. ARDS may occur through mechanisms such as endotoxemia, complement activation, immune complex deposition, cytoadherence, microemboli, and disseminated intravascular coagulation.

Cardiac complications of babesiosis include the following:

  • Myocardial infarction

  • Congestive heart failure

Renal complications of babesiosis include the following:

  • Renal insufficiency

  • Renal failure

Postsplenectomy patients may experience hemophagocytic syndrome, acute renal failure, and generalized seizures. Coma can occur, possibly as a consequence of severe sepsis, ARDS, or multiple organ dysfunction syndrome (MODS). Coinfection with Lyme disease is a possible complication.