Babesiosis

Babesiosis is a protozoan infection transmitted by ticks. Symptoms (flu-like syndrome and hemolytic anemia) begin 1-4 weeks after a tick bite. Patients at increased risk of infection are asplenic, elderly, or immunocompromised, e.g., AIDS patients.

CASES/YEAR
11,280 (US); 22,560 (Global)
CATEGORY
Arthropod-Borne
AGENT TYPE
Protozoa
OTHER NAMES
Babesia microti infection; B. divergens infection (Europe); B. duncani (formerly WA1-type parasite);
ACUITY
Acute-Moderate
INCUBATION
Usually 1 to 4 weeks after tick bite; As long as 176 days after transfusion; [PPID, p. 3404]
INITIAL SYMPTOMS
A flu-like syndrome in most patients; Patients with impaired immunity may develop severe babesiosis complicated by respiratory failure, DIC, CHF & renal failure; [Harrisons, p. 614, 618] Subclinical in 1/2 of children & 1/4 of adults; [Cecil, p. 2121]
PRECAUTIONS
"Blood and body fluid precautions." [CCDM, p. 63] "Not transmitted from person to person except rarely by transfusion." [CDC 2007 Guideline for Isolation Precautions]
COMMENTS
FINDINGS:
In untreated patients, the febrile illness lasts several days to a few months. Some patients have hemolytic anemia and thrombocytopenia. [CCDM, p. 61] Arthralgias, headache, nausea, hepatosplenomegaly, leukopenia, and thrombocytopenia are common findings. Less than 20% of patients have cough and dyspnea. Relative bradycardia has been reported. Severe cases are associated with prior splenectomy. Complications include acute renal failure, pulmonary edema, disseminated intravascular coagulation, shock, and respiratory failure. [ID, p. 2304] Babesiosis mimics malaria. The illness begins 1-4 weeks after a tick bite or 4-9 weeks after transfusion. Additional findings are diarrhea, sweating, and elevated liver transaminases. Antibodies become detectable about 1 week after onset of symptoms. [Guerrant, p. 676-81] The ticks are only 2 mm in diameter and not usually seen. [PPID, p. 3403] Renal failure from intravascular hemolysis may progress to hypotension, coma, and death. [Guerrant, p. 678] Severe cases resembling falciparum malaria (high fever, hemolytic anemia, jaundice, and renal failure) are seen in elderly patients and patients with splenectomy and AIDS. [Merck Manual, p. 1544]

EPIDEMIOLOGY:
Babesiosis is endemic on several USA east coast islands and in southern Connecticut. The vectors are nymphal Ixodes ticks, and the agents are protozoan parasites of red blood cells. Asymptomatic infections are common. Transmission has been reported by blood transfusion and, rarely, congenital/perinatal. On blood smear examination, the parasite may be confused with plasmodium falciparum. Reservoirs are rodents in the USA and cattle in Europe. [CCDM, p. 62-3] In Europe, babesiosis is a rare disease usually caused by B. divergens. Nearly all patients are asplenic. In the US, babesiosis is caused by B. microti, and asymptomatic cases are common. Patients at risk for severe disease are asplenic, elderly, infected with HIV, or immunosuppressed. [PPID, p. 3402]
DIAGNOSTIC
Blood smear (Wright or Giemsa stain); Serology; [CCDM, p. 61] Tetrads pathognomonic but rarely identified; Blood PCR most sensitive test; Serology; [ABX Guide] Giemsa stained thin smears; PCR and serology; [Harrisons, p. 618]
SCOPE
Global; In USA, most cases on eastern seaboard and some cases reported in upper Midwest (Wisconsin and Minnesota); [CCDM] Main foci in US (>90% of cases) are in CT, MA, MN, NJ, NY, RI, and WI; [PPID, p. 3400]
SIGNS & SYMPTOMS
  • >arthralgia
  • >fatigue, weakness
  • >fever
  • >myalgia
  • >relative bradycardia
  • E pharyngitis
  • G abdominal pain
  • G diarrhea
  • G hepatomegaly
  • G jaundice
  • G liver function test, abnormal
  • G nausea, vomiting
  • H anemia
  • H hemolysis
  • H leukopenia
  • H splenomegaly
  • H thrombocytopenia
  • N headache
  • N lethargy
  • N paresthesia
  • N stiff neck
  • R cough
  • R dyspnea
  • S petechiae and ecchymoses
  • *acute renal failure
  • *ARDS
  • *bleeding tendency
  • *pulmonary edema
  • *shock
  • *stupor, coma
  • *weight loss
ANTIMICROBIC

Yes

VACCINE

No

ENTRY
Needle (Includes Drug Abuse), Scalpel or Transfusion
VECTOR
Ticks
RESERVOIR
Cattle, Goats and Sheep, Deer, Elk and Antelope, Rodents, Wild Animals
RISK FACTORS
  • Asplenic patients
  • Have a blood transfusion
  • Work or play in tick-infested area
DRUG LINK
Merck Manual: Babesiosis
REFERENCES FOR CASES/YEAR
1. (US) Published in MMWR 2011 = 1,128; Use correction factor of 10 for reported diseases: 1,128 X 10 = 11,280;
2. (Global) The vast majority of cases in US; Sporadic cases in Europe and rest of world, e.g. about 30 cases in Europe caused by B. divergens, a pathogen of cattle. ; [Harrison ID, 2nd Ed, p. 1174] Estimate global rate = 2 X US rate = 22,560;