Disease transmission

Transstadial transmission

Transstadial (i.e. from one life stage to the next) occurs in East Coast fever (ECF) caused by the protozoan Theileria parva and transmitted mainly by R. appendiculatus but also by R. zambeziensis. In both vectors the parasite is acquired during larval or nymphal feeding and transmitted in the next stage by nymphs (if acquired by larvae) or adults (if acquired by nymphs). After transmission of the parasite to a na├»ve animal, the ticks are free of infection. The parasite undergoes a complex reproductive cycle in the ticks in contrast to many other pathogens. Anaplasma spp. for instance can also be transmitted transstadially but are already infectious in the same lifecycle stage in which the pathogen was acquired. Intrastadial transmission of Anaplasma spp. is also possible.