Skelton was unable to find evidences of leprosy bacilli in bedbugs living in the beds of lepers. Paldrock also was unable to find any evidence of leprosy bacilli in bedbugs a few hours after feeding on leprous tissue, but did find acid-fast rods in cockroaches which had fed on leprosy nodules, even fourteen days after the feeding.
A. J. Smith fed bedbugs on Duval’s organism and recovered acid-fast bacilli for considerable periods. The question arises, however, as to the significance of Duval’s bacillus for leprosy.
Acid-fast bacilli have been reported from head lice and mosquitoes, when the insects have been feeding on leprous tissue, but little or no evidence of any multiplication has been obtained.
For many years Jonathan Hutchinson insisted that leprosy was caused by the eating of imperfectly cured or decomposing fish, a view which now has no supporters.
For a time it was considered that the initial lesions of leprosy were to be found in the nasal mucosa and especially in ulcerations of the nasal septum and that it was by the atrium of the nasal mucous membrane that infection occurred.
There is no question but that the examination of the nasal mucus for leprosy bacilli is of prime importance in diagnosis and it may be that cases showing ulcerations of the septum are especially dangerous when sneezing, but very few believe that leprosy is to any extent contracted through this channel. De Azevedo examined smears from the nasal mucosa in 59 persons who were in close contact with lepers without finding acid-fast bacilli in a single instance.
With a period of incubation covering from two to ten years it is of course manifestly difficult to arrive at any correct idea as to transmission but there is a growing belief that the free and frequent use of soap is a decided factor in preventing infection which may, like rat leprosy, be best brought about by continued contact with a skin surface more or less abraded. There has been a suspicion, but no proof, that sexual intercourse may bring about infection.
Rat Leprosy.—A disease occurring naturally among rats was first observed by Stefansky, in Odessa, in 1903.
There are two types: (1) Of skin and muscles, and (2) of the lymphatic glands. In the skin form areas of alopecia are present with thickening of the site invaded. These areas are most often on the back of the head. Just as in human leprosy the epithelium is unaffected, the corium however being filled with cells packed with acid-fast bacilli, exactly similar to the picture in human leprosy. Ulceration of these subcutaneous nodules is common.