pertaining to zoogeography.
receptors. for the lyme disease agent, b. burgdorferi, the presence of a specific receptor, tick receptor for outer surface protein a, abbreviated as trospa, enables i. scapularis to serve as the specific vector for this pathogen within its zoogeographic range. it is likely that other, closely related species, for example, i. affinis, also carry this receptor, since these ticks also harbor the pathogen and transmit it to vertebrate hosts. whether it also occurs in the western blacklegged tick, i. pacificus, is unknown. however, other tick species, for example, dermacentor variabilis, which often share the same hosts as i. scapularis or i. affinis, are not competent vectors since they lack this receptor. hhs.gov