Intracutaneous infection with leptospira icterohaemorrhagiae (shibaura strain) of the guinea pig

Abstract

Experimental leptospirosis with Leptospira icterohaemorrhagiae Shibaura strain was studied in guinea pigs. When the pathogen was inoculated intracutaneously to the back of the animals, localized haemorrhage was observed at the inoculated site before the appearance of general haemorrhage. The severity of the local lesion increased progressively until the 7th day of inoculation. The minimum infective dose (MID) or the 50% infective dose (ID50) of the leptospiral suspension was determined by the appearance of the macroscopic local haemorrhage 7 days after inoculation. The MID thus determined was almost comparable with the value determined by the development of general symptoms and signs by conventional ip inoculation. The number of the pathogen per ID50 varied between 6 and 35 in five experiments. The local haemorrhage was effectively protected by active or passive immunization. Microscopically, haemorrhage at the inoculated site was found mainly in the dermis, directly beneath the epidermis in particular, and accompanied with leakage of the pathogen. The pathogen was also detected abunduntly in the thickened epidermal layer covering the inoculated area as well as in the epithelial matrix of hair-follicle, probably due to the proliferation of the pathogen at the site. © 1974, National Institute of Infectious Diseases, Japanese Journal of Infectious Diseases Editorial Committee. All rights reserved.