Vector competence of Ixodes angustus (Acari : Ixodidae) for Borrelia burgdorferi sensu stricto

The vector competence of Ixodes angustus for Borvelia burgdorferi sensu str icto (s.s.) was investigated in the laboratory. The larval progeny of femal e ticks from Washington State were placed on Swiss-Webster mice that had be en inoculated intravenously with 10(8) spirochetes each of a Californian is olate of B. burgdorferi. Spirochetes were detected in 6 (12%) of 50 nymphs derived from larvae that had fed on these animals. Ten nymphs from the same cohort of experimentally infected ticks were placed on each of 4 naive dee r mice (Peromyscus maniculatus). One of the mice seroconverted to B. burgdo rferi and spirochetes were isolated from its ear tissues 4 weeks after expo sure to ticks. Further vector competence trials were conducted with I. angu stus ticks from California. Larvae were fed on deer mice that had been inoc ulated intradermally with B. burgdorferi along with larvae of I. spinipalpi s as a comparison group. There was no significant difference in the prevale nce of infection in nymphs of I. angustus (8.2%) versus those of I. spinipa lpis (12.1%). We conclude that I. angustus is a competent experimental vect or of B. burgdorferi s.s. and its efficiency for acquiring and transstadial ly passing such spirochetes is similar to that of I. spinipalpis.