Early workers thought that rodents were the
natural reservoir of infection, but it is now believed
that mites are both the vector and the reservoir (4).
Naturally-infected mites, reared in the laboratory,
have transmitted the infection for more than
twenty generations, while uninfected chiggers, if
fed experimentally on infected mice, take up R.
tsutsugamushi, but fail to transmit the infection
transovarially to the next generation (5).
This mite is fastidious in matters of temperature, humidity and food, and finds
everything suitable in restricted areas. Scrub typhus is generally seen in people
whose occupational or recreational activities bring them into contact with ecotypes
favourable with vector chiggers (6).