Transstadial transmission occurs when a pathogen remains with the vector from one life stage ("stadium") to the next. [1] [2] [3] For example, the bacteria Borrelia burgdorferi, the causative agent for Lyme disease, infects the tick vector as a larva, and the infection is maintained when it molts to a nymph and later develops as an adult. [1] [2] This type of transmission is seen in other parasites like viruses or Rickettsia. [3] In addition to ticks, mites are another common vector. [3] [4] Some sources consider transstadial transmission a type of horizontal transmission, [5] [6] whereas other sources consider it vertical or partial vertical transmission. [7] [8]
Transstadial blockage could be considered the opposite of transstadial transmission, where the parasite cannot be carried over from one life stage to the next. [4] For example, viruses that undergo transstadial blockage will have decreased infectivity in molting insects. [4]