The efficacy of co-feeding as a means of maintaining Borrelia burgdorferi: a North American model system.

Although research on co-feeding as a means of maintaining tick-borne pathogens has focused chiefly on viruses, recent interest has been directed toward the importance of this phenomenon in maintaining the Lyme disease spirochete, Borrelia burgdorferi. In the current study, an experimental model was developed to determine under what conditions immature co-feeding ticks exchange B. burgdorferi using the principal North American vector (Ixodes scapularis) and reservoir (Peromyscus leucopus) species. Experiments conducted with the density of ticks likely to be encountered in nature (8 nymphs & < 40 larvae) demonstrated that no co-feeding larvae became infected; in contrast, horizontal transmission infected 30-64% of test larvae. Only the highest densities of ticks (40 nymphs & > 200 larvae) produced infected larvae (5%) upon co-feeding of larvae and nymphs. An important role for co-feeding in the ecology of Lyme disease in North America has yet to be established.