MULTIPLE INFECTIONS OF IXODES-SCAPULARIS TICKS BY BORRELIA-BURGDORFERI AS REVEALED BY SINGLE-STRAND CONFORMATION POLYMORPHISM ANALYSIS

The genetic heterogeneity of the spirochete Borrelia burgdorferi withi n single adult black-legged ticks from Shelter Island, N.Y., was deter mined by cold, single-strand conformation polymorphism (SSCP) analysis , The central region of the ospA gene of B. burgdorferi from infected ticks was amplified by nested PCR. Amplified product of the correct si ze was obtained from 20 of 45 ticks (44%). This is the fraction of tic ks that is expected to be infected with B. burgdorferi. Four variant c lasses were determined by SSCP analysis, Eight ticks were infected wit h a single variant, nine ticks were infected with two variants, two ti cks were infected with three variants, and one tick was infected with all four variants, DNA from each variant was sequenced. Five different sequences were found. The sequence of each variant was different from that of another variant by a single base. SSCP analysis could disting uish three of the four single-base changes found in the region.