BACKGROUND: The causative agents of babesiosis (Babesia microti) and Lyme disease (Borrelia burgdorferi) are transmitted by the same tick species (Ixodes scapularis), which is present in most Indiana counties. Indiana is classified as a low-incidence state for Lyme disease (1.3 cases/100,000 persons from 2011–2015) and babesiosis is rare, with only one probable case reported during the same period. In June 2016, the Indiana State Department of Health (ISDH) was notified of approximately 120 patients in northwestern Indiana being treated for babesiosis and Lyme disease co-infection.
METHODS: Symptoms among 14 patients with reportedly representative clinical presentations were compared with the clinical criteria specified in the national surveillance case definitions for babesiosis and Lyme disease. Blood specimens were collected during June 27–29, 2016 for reference testing at the Centers for Disease Control and Prevention. Babesiosis testing included light microscopy of blood smears, polymerase chain reaction, and indirect fluorescent antibody testing (IFA). Lyme disease testing included whole cell sonicate and C6 peptide enzyme immunoassays followed by IgM and IgG Western blots.
RESULTS: Illness onsets ranged from July 2015 to June 2016, with 12 (86%) patients having onset more than one month prior to laboratory testing. Subjective clinical criteria consistent with babesiosis and/or Lyme disease included fatigue (86%); myalgia (86%); sweats (57%); headache (43%); and arthralgia (43%). Objective clinical criteria for babesiosis were rarely reported (fever, 7%; anemia, 7%). Objective clinical criteria for Lyme disease (dermatologic, rheumatologic, neurologic or cardiac abnormalities) were not reported. The median number of antimicrobial medications reported for each patient was three (range: 1–6). Two (14%) patients had low levels of B. microti antibodies detected by IFA; however, none of the patients had laboratory evidence supporting diagnoses of active babesiosis or Lyme disease at the time of testing.
CONCLUSIONS: This investigation did not reveal evidence of a cluster of babesiosis or Lyme disease in northwestern Indiana, though this group of patients was receiving multiple medications for these diagnoses. Most patients did not have acute illnesses or objective clinical criteria for either disease. Babesiosis and Lyme disease are best considered as differential diagnoses for patients with possible tick exposure who have recent acute illnesses compatible with these diseases. In low-incidence states, it is especially important to obtain robust laboratory results using an accredited laboratory. Patients for whom these diseases are suspected should be diagnosed and treated according to existing recommendations promulgated by the Infectious Diseases Society of America.