Tick-borne Disease Health Alert

May 6, 2011

Anaplasmosis Rivals Lyme Disease As Record Numbers of Minnesotans Sick from Tick-Borne Diseases in 2010

MDH urges medical providers to note the following:


Babesiosis is a malaria-like illness caused by red blood cell parasites (Babesia spp.). It is carried by the same ticks that carry Lyme disease.

  • MDH recommends at least 2 of the following 3 tests: PCR, peripheral blood smear, or serology.
  • Recommended treatment is atovaquone + azithromycin (for mild to moderate cases) or clindamycin + quinine (for severe cases) x 7-10 days. Repeated treatment and monitoring of parasitemia levels may be necessary for patients with certain forms of immune compromise.
  • Transfusion-transmitted babesiosis can occur and should be considered in transfusion recipients who develop anemia, thrombocytopenia, or a febrile illness after receiving cellular blood products. Suspect cases should be promptly reported to associated blood banks and MDH.

Lyme disease

  • The pathognomonic erythema migrans (EM) rash is present in the majority (but not all) cases of Lyme disease. It is not always “bulls-eye” in appearance but does expand in size over time. If a patient has an EM highly suggestive of Lyme disease and recent symptom onset (<2-3 weeks), B. burgdorferi antibody tests are not recommended because of low sensitivity at this stage of infection.
  • Seroconversion to IgG antibodies on Western blot is expected for patients with symptoms lasting > 1 month. For patients who have had signs and symptoms for >1 month or who do not have an EM rash, diagnosis should be based on laboratory tests in addition to symptomatology.
  • Long-term or repeated antibiotics for the treatment of “chronic” Lyme disease is not necessary, safe, or recommended. Evidence does not demonstrate persistence of viable B. burgdorferi after treatment with the correct antibiotic for the indicated treatment duration (2-4 weeks). Persistent symptoms following proper treatment may be due to lingering inflammatory processes, an unrecognized tick-borne coinfection, or an unrelated process.

Human anaplasmosis / ehrlichiosis

These disease names are often used interchangeably, which is incorrect. Human anaplasmosis (formerly “human granulocytic ehrlichiosis”; etiologic agent Anaplasma phagocytophilum) is endemic to Minnesota and is carried by Ixodes scapularis ticks (Lyme disease vector). In contrast, human ehrlichiosis caused by Ehrlichia chaffeensis is endemic to many southern states and carried by Lone Star ticks. However, another newly-identified form of ehrlichiosis is caused by the Ehrlichia muris-like agent, which is transmitted by I. scapularis ticks.

  • PCR tests provide the best sensitivity and specificity. A peripheral blood smear for Anaplasma can also be performed, but sensitivity can be low.
  • If serologic tests are ordered, make sure to include both Anaplasma and Ehrlichia, or also order a PCR test. Anaplasma and Ehrlichia can be cross-reactive on serologic assays.
  • Transfusion-transmitted anaplasmosis cases have occurred in Minnesota and should be considered in patients who develop a fever and thrombocytopenia post-transfusion. Contact the associated blood bank immediately about any suspect transfusion cases and notify MDH.

Rocky Mountain spotted fever (RMSF)

Although RMSF is considered rare in Minnesota, MDH receives a few reports every year in patients with no travel history. A Dakota County child who contracted the infection in Minnesota died of RMSF in 2009.
RMSF is carried by Dermacentor ticks, which are common in wooded or brushy areas throughout the state.

  • Signs of RMSF can include fever, maculopapular or petechial rash, and thrombocytopenia.
  • To prevent severe disease, tetracycline treatment should be initiated for any suspect cases while test results are pending, even for children.

Powassan disease

Powassan (POW) virus is a tick-transmitted flavivirus, that includes a strain (lineage II or “deer tick virus”) that is transmitted by Ixodes scapularis. The virus can cause encephalitis or meningitis, and long-term sequelae occur in approximately 50% of patients. Approximately 10-15% of cases are fatal.

Most patients had neuroinvasive disease (12 encephalitis and 8 meningitis) but 2 were non-neuroinvasive POW fever cases. Seventeen (77%) cases were male. The virus appears to be widely distributed in the same wooded parts of the state that are endemic to other tick-borne diseases transmitted by I. scapularis.


All tick-borne diseases are reportable to MDH; reports need to include demographic, clinical, and laboratory information. Please contact MDH tick-borne disease epidemiology staff at 651-201-5414 for associated forms or see Tickborne Disease Case Report Form.


More information/guidelines

Updated Friday, April 25, 2014 at 12:51PM