IMMUNOSEROLOGIC EVIDENCE OF COINFECTION WITH BORRELIA-BURGDORFERI, BABESIA-MICROTI AND HUMAN GRANULOCYTIC EHRLICHIA SPECIES IN RESIDENTS OFWISCONSIN AND MINNESOTA

In Wisconsin and Minnesota, Ixodes scapularis (Ixodes dammini) ticks a re the vector of three microorganisms that may cause significant disea se in humans and lower mammals. These diseases include Lyme borreliosi s, which is caused by Borrelia burgdorferi, babesiosis, which is cause d by Babesia microti, and human granulocytic ehrlichiosis (HGE), which is caused by an apparently new species in the genus Ehrlichica. Immun oserologic testing was performed on sera from patients with a diagnosi s of one of these diseases to determine if there was evidence of coinf ection with one or more of the other agents. Of 96 patients with Lyme borreliosis. 9 (9.4%) demonstrated immunoserologic evidence of coinfec tion: 5 (5.2%) with the agent of HGE, 2 (2.1%) microti, and 2 (2.1%) w ith both microorganisms. Of 19 patients diagnosed with HGE, 3 (15.8%) showed immunoserologic evidence of coinfection: 1 (5.3%) with B. burgd orferi, 1 (5.3%) with B. microti, and 1 (5.3%) with both microorganism s. One patient diagnosed with babesiosis was also seropositive for ehr lichiosis. These results provide evidence for coinfection. perhaps exp laining the variable manifestations and clinical responses noted in so me patients with tick-transmitted diseases. In certain clinical settin gs, laboratory testing for coinfection is indicated to ensure that app ropriate antimicrobial treatment is given.