Wisconsin Division of Public Health Disease Surveillance Manual (EpiNet, February 2005)
I. IDENTIFICATION
A. CLINICAL DESCRIPTION: A tickborne and bloodborne febrile illness caused by various species of Babesia (protozoan parasites of the red blood cells). The disease, which has the potential to be severe and occasionally fatal, is typically associated with constitutional symptoms and hemolytic anemia.
B. REPORTING CRITERIA: Clinical diagnosis with laboratory confirmation.
C. LABORATORY CRITERIA FOR CONFIRMATION:
- Identification of intraerythrocytic Babesia parasites by light microscopy in a peripheral blood smear
- Isolation of the parasite from a whole blood specimen by animal inoculation
D. WISCONSIN CASE DEFINITION:
Confirmed Babesiosis: A clinically compatible illness that is laboratory confirmed.
Probable Babesiosis : A clinically compatible illness with demonstration of a Babesia‑specific antibody titer of at least 1:256 with an indirect fluorescent antibody (IFA) test for total Ig or IgG. The titer should be at least 1:1024 for infection with WA1-type parasites.
Comments : Confirmation of the diagnosis of babesiosis by a reference laboratory is strongly encouraged. The validity of the diagnosis of babesiosis is highly dependent on the laboratory that does the testing. For example, differentiation between malaria and Babesia parasites on peripheral blood smears can be very difficult.
Please note that the following techniques are not considered sufficient for laboratory confirmation of babesiosis:
- Fourfold change in antibody titer: Intra- and inter-laboratory variability in titer determination preclude the use of titer change to definitively diagnose babesiosis.
- Polymerase chain reaction: Use of this method to demonstrate Babesia DNA in blood is still experimental, and false-positive results may be obtained.
- IFA testing for IgM antibody: A positive IFA result for IgM is insufficient for diagnosis in the absence of a positive IFA result for IgG. If the IgM result is positive but the IgG result is negative, a follow-up blood specimen should be tested. If IgG seroconversion is not noted, the IgM result likely was a false positive.
- Immunoblot testing for IgG or IgM: This method is still experimental.
III. ACTIONS REQUIRED / PREVENTION MEASURES
WISCONSIN DISEASE SURVEILLANCE CATEGORY II: Report to the patient's local health officer on an Acute and Communicable Disease Case Report (DPH 4151) or other means within 72 hours of the identification of a case or suspected case.
A. EPIDEMIOLOGY REPORTS REQUESTED:
1. Acute and Communicable Diseases Case Report (DPH 4151).
2. Babesiosis Case Report Form (CDES 101).
B. PUBLIC HEALTH INTERVENTIONS:
Patient education as needed to minimize future risk of exposure to infected ticks. Because Babesia sp. can be acquired by blood transfusion, ascertain whether patient recently received blood or blood products.IV. CONTACTS FOR CONSULTATION
A. BCDP / COMMUNICABLE DISEASE EPIDEMIOLOGY SECTION: (608) 267-7321.
B. REGIONAL STAFF: See Epinet Introduction: “REGIONAL OFFICE CONTACTS”.
C. WSLH: Viral and Rickettsial Serology, 608/262-0248.
V. RELATED REFERENCES
1. “Babesiosis” DPH Disease Fact Sheet Series: View a list of all current Communicable Disease Fact Sheets
2. Heymann DL, ed. Babesiosis. In: Control of Communicable Diseases Manual. 18 th ed. Washington , DC : American Public Health Association, 2004: 61-63.
3. Pickering LK, ed. Babesiosis. In: Red Book: 2003 Report of the Committee on Infectious Diseases. 26 th ed. Elk Grove Village , IL : American Academy of Pediatrics, 2003:211-212.
VI. DISEASE TRENDS
Babesiosis was not an officially reportable condition in Wisconsin until April, 2000. Since then, only six cases have been reported, one of which was transfusion-acquired.