xenoparasite

[ zĕn′ə-părə-sīt′, zē′nə- ]

n.

An ectoparasite that becomes pathogenic when the resistance of its host weakens.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.