Recent work on leptospirosis

Abstract
All these facts, clinical, serological and epidemiological, combine to justify my opinion that we are dealing with a separate species of leptospira and not merely a subspecies or variety of the cosmopolitan Weil type. The dog strain consequently, occupies a position comparable to that of another leptospira, L. hebdomadis . It-is true this is a species still farther removed from the typical parasite of Weil's disease, as cross-agglutination by Weil serum is practically unknown. But L. hebdomadis has this in common with the dog strain, namely, it is the causative agent in epizootics among animals other than sewer rats, viz., the voles ( Microtus montebelloi ). The fact that these parasites are restricted to particular hosts, vole and dog, justifies, in my opinion, our desire to give them the rank of separate species. If, in future, we should find the dog strain adapting itself to live in the rat's kidney, we shall consider ourselves fortunate in having witnessed the time when this new condition was not yet established. Even in a case like that, historical arguments will uphold the dog strain's claim to the status of an independent species. On the strength of its divergent characters Professor Klarenbeek and I propose to name this organism Leptospira canicola . This discovery of the dog strain brings the number of human leptospiræ in Europe up to three : (1) the cosmopolitan L. icterohœmorrhagiœ in rat and dog, the cause of classical Weil's disease ; (2) L. canicola causing a specific canine disease ; (3) L. grippo-typhosa the infecting agent in the swamp fever of Eastern Europe. The clinical (non-icteric), serological and epidemiological picture (appearing in well-defined epidemics) clearly marks off this disease as entirely separate from other leptospiroses. ∗ ∗ The individuality of swamp fever is also supported by the experience of Kosthaff (Leyden), who infected a number of patients with swamp fever for therapeutic purposes. The disease was accompanied with high fever but jaundice never appeared. We are quite ignorant, however, of the species of animal acting as a reservoir of this leptospira. The discovery of this new species extending the range of study of leptospiroses in Europe does not introduce any complications or confusions. In this respect Europe is far better off than the East (except Japan), where there exists numerous strains separated by their serological reactions only, and not by any clear-cut clinical or epidemiological (virus-reservoir !) distinctive characters. We know of eight strains, at least, in the Dutch East Indies † † Not including the leptospiæ observed in two cases of idiopathic blackwater fever (not caused by malaria) in Deli (Sumatra) but which we did not succeed in cultivating ( Schüffner, Snyders, Kouwenaar ). ; Fletcher 1927, in the Malay Peninsula isolated six, some of them were identified with Dutch East Indian ones ; Taylor and Goyle 1931 in the Andamans found two more. They are all acting as the causative agent of Weil's disease in its serious or mild form. One should feel inclined, I admit, to avoid the difficulties by pooling all these Indian strains into one variable species. But I still want to resist the tendency to give up the Indian strains, because such a simplification is not really helpful : it obscures the problems instead of solving them. In Europe, at any rate, we need not resort to it at all. The characters peculiar to each of the leptospiroses of this continent, combined with the marked constancy of the biological characters of their causative agent allow us, nay they force us, to admit them as independent members of one nosographical family.