MALAYSIAN PARASITES III 
A SUMMARY REVIEW OF COLLECTIONS OF TROMBICULID MITES 
IN THE ASIATIC-PACIFIC AREA 
By 
J. R. AUDY 
Contents 
Page 
Introduction 29 
Summary of trombiculid collections . . . . . . . .31 
Comments on the summarised collections 
Relative poverty of deforested and settled areas . . . . . . 33 
Effect of bias in collecting host species . . . . . . . .33 
Effect of seasonal changes . . . . . . . . . .34 
Distribution of the major groups of trombiculids ...... 34 
Summary 42 
Introduction 
Although trombiculid mites are among the most numerous of all ectoparasites of mammals 
in the tropics of this region, relatively few were collected until after 1930. The great stimulus 
provided during World War II by researches into scrub-typhus has gradually given way to the 
stimulus provided by any large and newly amassed body of information in which there is wide- 
spread interest by a considerable number of fellow- workers. 
These mites are well known because some members transmit scrub-typhus and others 
cause scrub-itch, an affliction which may have considerable economic and military importance 
locally and which is much more widespread than scrub-typhus. A number of workers are now 
suspecting that they may transmit various rickettsial, viral, and even protozoal (e. g. Toxoplasma , 
Giroud et al . , 1952) infections among their animal hosts*. They represent a rich and numerous 
source of potential vectors of the zootic infections which form the background to a number of 
human diseases. 
Sufficient information about the trombiculids is now gathering for useful zoogeographical 
studies to be started. It is important for such purposes to distinguish between (a) casual 
collections from some occasional host or a few hosts, (b) extensive collections, by casually 
sampling a relatively large number of foci in a country or district and (c) intensive collections, 
carried out over a year or more. The known patchy distribution of these mites, and the fact 
that many or most of them show more or less seasonal incidence, means that all casual and most 
extensive collections are likely to give a false impression of the species present and their relative 
abundance. Furthermore, deforestation and settlement tend to eliminate most of the native 
species of host and mite, and to allow a minority to become locally very populous together with 
introduced mites and introduced commensal hosts, as may be seen in Table 1. Collections 
made around villages and in cleared areas may thus leave the native mite fauna almost 
unsampled, even though the cleared areas may have become considerably overgrown. 
* All the available epidemiological evidence also incriminates a species of Trombicula as the vector 
of Epidemic Haemorrhagic Fever (EHF) in Korea (Department of the Army Technical Bulletin TB 
MED 240, Washington, D.C., U.S.A., 5 May 1953, p. 5). 
MALA YA , No. 26 , 1953 
