TRANSOVARIAL DEVELOPMENT OF SCRUB TYPHUS RICKETTSIAE IN A COLONY OF VECTOR MITES

The transovarial development of Rickettsia tsutsugamushi in a colony of Leptotrombidium (Leptotrombidium) akamushi, a mite vector of scrub typhus, has been studied over 5 generations. The transovarial infection rate was 98%; the filial infection rate was usually 100%, though lower rates were occasionally observed. These rates may not be valid for all populations of vector mites because they have been estimated for female mites producing only female offspring. Nevertheless, these studies show that transovarial passage of rickettsiae can be highly efficient. By this mechanism, point foci of virtually 100% infected larval mites could be produced. The risk of infection for man exposed to larval mites in such point loci would be extremely high. © 1969 Royal Society of Tropical Medicine and Hygiene.