You Wouldn’t Know it If a Bug Bit You!
July 15, 1999 2 minutes read
You Wouldn’t Know it If a Bug Bit You!
Hilton E, et al. Am J Med 1999;106:404-409.
The seroepidemiology of five tick-borne diseases (including Borrelia burgdorferi, Ehrlichia chaffeensis, Ehr-lichia equi, Babesia microti, and organisms of the spotted fever group of Rickettsia) was assessed in 835 subjects recruited for participation in a Lyme vaccine study. All of the participants resided or worked in a high-risk area of New York, including Suffolk (n = 828) and West-chester (n = 7) counties, and all of them were routinely active in the outdoors. Sera were obtained at baseline and at one year, and in the event of symptoms suggestive of infection. Follow-up serologies at one year were available for 671 participants.
The seroprevalence of infection at the beginning of the study was similar for all of the organisms (~ 4-5%) with the exception of Babesiosis, which was unusual (1%). Antibodies to B. burgdorferi were the most prevalent, being identified in 34 subjects (5%) at baseline. Seven patients (1%), five of whom were symptomatic, had evidence of seroconversion during the study.
Surprisingly, seroevidence of infection was found in 4% of subjects to either Rocky Mountain Spotted Fever or Ehrlichia, including E. chaffeensis in 23 and E. equi in one. Over the course of the one-year study, five (1%) additional patients seroconverted to E. chaffeensis, including two with symptoms suggestive of ehrlichial infection. Six patients (1%) seroconverted to Rocky Mountain Spotted Fever during the study—none of them had any knowledge of infection due to Rickettsia.
Infection due to B. microti was infrequent; only six (1%) patients had evidence of infection at baseline, and one patient had seroconverted during the study.
In summary, antibodies to one or more tick-borne organisms were found at baseline in 88 subjects (13%) residing or working in an area endemic for tick-borne diseases, and 19 subjects (2.8%) seroconverted to one of the organisms during the one-year study. Most of the infections were asymptomatic and detected solely by serological means. Not surprisingly, most of the patients had no recollection of a tick bite, which is fairly common for these infections. Serological evidence of dual infection was unusual (0.8%), and no evidence of co-infection was found during the course of this one-year study.
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