This chapter identifies animal diseases that are host specific and reviews the effects of various human diseases on animals. It also identifies history, etiologic, human Infection, diagnosis, public health aspects and therapeutic aspects of each disease important to epidemiology and prevention. The chiggers, rather than the rodent hosts on which they live, are responsible for the maintenance of scrub typhus foci within endemic areas. Scrub typhus is generally seen in people whose occupations or recreational activities bring them into contact with ecotypes favourable to vector chiggers and their rodent hosts. The high efficiency of transovarial transmission of scrub typhus rickettsiae has been demonstrated in at least three naturally infected, laboratory-reared species: Leptotrombidium arenicola, L. fletcheri, and L. pallidum. Outbreaks of scrub typhus are frequently traceable to a common site of exposure, and sequential chigger surveys consistently yield sharply delineated “mite islands” in the same locations.