钩端螺旋体病的研究进展

钩端螺旋体病(钩体病)是全世界范围内流行的人兽共患病,也是洪涝灾区重点监控的传染病之一.2007年6月,我国多个省市遭受暴雨洪灾,钩体病一旦爆发,将成为重大公共卫生问题.此文就钩体病的病原学、流行病学、发病机制、诊断及预防进行综述.     

Research needs in leptospirosis

Leptospirosis is a widespread infection of man and animals, and locally it assumes considerable importance as a public health and economic problem. It is an important occupational infection among persons working with animals or in environments that may be contaminated by infected animals. In recent years, considerable attention has been devoted to this infection but efforts to control and eliminate it, especially from natural foci, are hindered by gaps in our knowledge. This memorandum is a review of recent progress and current problems in leptospirosis research, with special reference to taxonomy, epidemiological methods, and control measures. Certain aspects of the basic biology of leptospires that are relevant to these topics are also discussed.     

Recent work on leptospirosis

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. icteroh?morrhagi? 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.¹ 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 Indies²; 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.     

Cardiac involvement in leptospirosis

Leptospirosis is a neglected global disease with significant morbidity and mortality. Cardiac complications such as chest pain, arrhythmias, pulmonary oedema and refractory shock have been reported in patients with severe disease. However, the frequency and extent of cardiac involvement in leptospirosis, are under-reported and poorly understood. Multiple factors may contribute to clinical manifestations that suggest cardiac involvement, causing diagnostic confusion. A variety of electrocardiographic changes occur in leptospirosis, with atrial fibrillation, atrioventricular conduction blocks and non-specific ventricular repolarization abnormalities being the most common. Electrolyte abnormalities are likely to contribute to electrocardiographic changes; direct effects on Na(+)-K(+)-Cl(-) transporters in the renal tubules have been postulated. Echocardiographic evidence of myocardial dysfunction has not been adequately demonstrated. The diagnostic value of cardiac biomarkers is unknown. Histopathological changes in the myocardium have been clearly shown, with myocardial inflammation and vasculitis present in postmortem studies. Nonetheless, the pathophysiology of cardiac involvement in leptospirosis is poorly understood. Cardiac involvement, demonstrated electrocardiographically or clinically, tends to predict poor outcome. No specific therapies are available to prevent or treat cardiac involvement in leptospirosis; current management is based on correction of deranged homeostasis and supportive therapy. Evidence suggests that direct myocardial damage occurs in patients with severe leptospirosis, and further studies are recommended to elucidate its pathophysiology, clinical features and contribution to overall prognosis, and to identify appropriate diagnostic investigations and specific therapies.