ANTIGEN-CAPTURE ENZYME-IMMUNOASSAY - A COMPARISON WITH OTHER METHODS FOR THE DETECTION OF SPOTTED-FEVER GROUP RICKETTSIAE LN TICKS

To evaluate the prevalence of spotted fever group rickettsiae along th e Adriatic Coast of Croatia, 832 ticks were examined by hemolymph test , direct immunofluorescence, antigen-capture enzyme immunoassay, and p olymerase chain reaction. Very good agreement was observed among direc t immunofluorescence, polymerase chain reaction, and antigen-capture e nzyme immunoassay. Twelve ticks that were positive by hemolymph test a nd negative by both direct immunofluorescence and polymerase chain rea ction presumably do not represent spotted fever group rickettsiae. By direct immunofluorescence, spotted fever group rickettsiae were presen t in 12% of Rhipicephalus bursa, 10.6% of Rh. sanguineus, and 7.8% of Dermacentor marginatus. From the 98 ticks containing rickettsia-like o rganisms by hemolymph test, seven spotted fever group rickettsial isol ates were established in cell culture. Four isolates were identified a s Rickettsia conorii. The antigen-capture enzyme immunoassay, which ut ilizes a monoclonal antibody to antigens of the 135-kD surface protein shared among many members of the spotted fever group, is recommended for primary screening of tick samples because it is reliable and yet l ess labor-intensive than the hemolymph and direct immunofluorescence t ests. Although the polymerase chain reaction is too expensive for use as a screening method, it is recommended for confirmation of positive screening results. In addition to the technologic advance of the antig en-capture enzyme immunoassay, this study documented by contemporary m ethods that R. conorii is present along the eastern Adriatic Coast not only in the classic vector, Rh. sanguineus but also in Rh. bursa and D. marginatus.