OCCURRENCE OF HIGH-RATIO OF MALES AFTER INTRODUCTION OF MINOCYCLINE IN A COLONY OF LEPTOTROMBIDIUM-FLETCHERI INFECTED WITH ORIENTIA-TSUTSUGAMUSHI

In colonies of Leptotrombidium fletcheri mites infected with Orientia tsutsugamushi (Ot), the agent of scrub typhus, males rarely appear. In the present study, the development of a high ratio of males was obser ved after introduction of minocycline (MC). A high dose of MC was inje cted subcutaneously into a mouse, and by feeding unfed larvae from an infected mite colony on this mouse, the Ot in the mites were successfu lly killed, Of a total of 130 unfed larvae attached to the mouse, 29 d eveloped into females; of these, 9 laid an average of 112.4 eggs/femal e. Unfed larvae in the succeeding generations were attached to untreat ed mice. All adults in the P and F1 generations were females, and male s started to appear at the F2 generation. The ratio of males to female s was 332:7, 108:13, 263:61 and 71:9 at the F2, F3, F4 and F5 generati ons, respectively. These data suggest that Ot in the ovary or gonad ma y suppress the development of males.