Department of Pathology, Harvard Medical School, Boston.
J Exp Med. 1931 Jul 31;54(2):181-6. doi: 10.1084/jem.54.2.181.
Study of two strains of epidemic (European) typhus and two strains of endemic (American) typhus in laboratory animals has shown their essential identity. .The characteristic typhus brain lesions can be shown to occur in all four strains after subcutaneous inoculation and Rickettsiae-filled cells can be found in the scrotal sac in all four strains after intraperitoneal inoculations. A strain of European typhus, which for 8 years has yielded no obvious scrotal reaction in guinea pigs, afterwards gave rise to a periodic scrotal reaction of variable severity. At present it occupies an intermediate position in this respect between the recently isolated European strain and the American strains. Variations in the scrotal reaction in guinea pigs appear to be correlated with strain variations in virulence in the human host. The incubation period in guinea pigs after intraperitoneal inoculation depends largely on the number of Rickettsiae injected.
对两种流行（欧洲）斑疹伤寒和两种地方（美洲）斑疹伤寒菌株在实验动物中的研究表明它们具有本质上的同一性。……皮下接种后，所有四种菌株都会出现典型的斑疹伤寒脑损伤，腹腔接种后，所有四种菌株的阴囊中都可以发现充满立克次体的细胞。一种欧洲斑疹伤寒菌株在 8 年内对豚鼠没有明显的阴囊反应，之后会引起周期性的、严重程度不同的阴囊反应。目前，它在这方面处于最近分离的欧洲菌株和美洲菌株之间的中间位置。豚鼠阴囊反应的变化似乎与人类宿主中菌株毒力的变化有关。腹腔接种后豚鼠的潜伏期在很大程度上取决于注射的立克次体数量。
