Last edited 05/2022

Mice, chipmunks, and other small mammals, as well as birds act as the major natural reservoirs for B. burgdorferi.

  • B. burgdorferi is not present in the deer, but the tick mates and feeds on them thus the disease is common where there are many deer
  • the female tick drops off, lays eggs which hatch and jump aboard mice, racoons and birds (1,2).

Three stages can be identified in Ixodes ticks - larvae, nymphs and adult forms which require blood feeding during each stage.

  • during feeding from reservoir hosts, Borrelia burgdorferi spirochetes are taken up by the larval and nymphal forms of the tick (1,2).
  • B. burgdorferi is believed to be transmitted in the saliva of the tick bite
    • B. burgdorferi is distributed in the midgut of the infected tick and within 24-72 hours it disseminates to other tissues, including the salivary glands. From here the spirochaete is inoculated into the next host.
    • the infection is most likely to be transmitted to humans by the nymphal form of the Ixodes ticks when they bite the humans (Ixodes ticks also serve as vectors for tick borne encephalitis and babesiosis).
      • they are at peak activity in spring and summer.

Fleas, flies, and mosquitoes do not act as vectors for Lyme disease (4).