Virulence in Mice of Orientia tsutsugamushi Isolated from Patients in a New Endemic Area in Japan

Four strains of Orientia tsutsugamushi (KN-1, KN-2, KN-3 and GJ-1) isolated from patients in an area of Gifu Prefecture, Japan, in which tsutsugamushi disease is newly endemic, were examined for their virulence in mice. Among these, KN-1 (identified as Kawasaki type), GJ-1 (identified as Kuroki type) and KN-2 strains were found to be non-lethal for BALB/c mice as well as CH3/HeJ mice, even with high doses (10⁶ × being the 50% mouse infectious dose). On the other hand, the KN-3 strain was found to be sufficiently virulent to kill BALB/c mice. Among the prototype strains (Gilliam, Karp and Kato), the Karp and Kato strains exhibited high virulence to mice, while the Gilliam strain killed only a susceptible strain of mouse. BALB/c mice infected with KN-1 and KN-2 strains showed significant splenomegaly and moderate ascites accumulation in the first week of infection, while these symptoms became prominent during the second week of infection using KN-3, Karp and Kato strains. After infection with the GJ-1 strain, these symptoms were not observed. Antibody responses induced by infections with highly virulent strains were lower than that with low or intermediate virulent strains.     

Multiple Copulations and Post-Copulatory Guarding in a Free-Living Population of Sika Deer (Cervus nippon)

Multiple copulations by females and post‐copulatory guarding by males, were studied in a free‐living sika deer population, on Nozaki, an island of the Goto Group, off the coast of Kyushu, Japan. In 1990, 1991, and 1993, observations were carried out mainly on open grassland in the central section of the island. It was found, that 10 of 22 females in estrus copulated more than once and five of them copulated with several males (multi‐male copulations), while the remainder copulated with a single male (repeated copulation). Almost all copulations were followed by guarding behavior. Dominant males (DMs) guarded significantly longer and more effectively than subordinate males (SMs). Guarding was interrupted in four of the SMs, when the guarding male was forcibly driven away from a female by higher ranked males (‘take‐over’) and in three cases when the female left the guarding male spontaneously (‘escape’). The only interruption of guarding of a DM was caused when a lower ranked male sneaked towards the guarded female and mated with her briefly (sneak). Interruptions of guarding initiated by females (escapes) occurred more when they were guarded by SMs than by DMs. Our results suggest that female sika deer indulge in multiple copulations to seek better genetic quality, rather than insuring fertility, enhancing genetic diversity, or avoiding harassment. The post‐copulatory guarding by DMs appears to be more effective in the prevention of additional copulations by females with other males than guarding by SMs. Moreover, SMs decrease the duration of the pre‐copulatory phase to achieve copulation before having to give way to DMs.