Tuberculosis and leprosy: Evidence for 

 interaction of disease 



Keith Manchester 



Leprosy and tuberculosis are chronic infective diseases of 

 mankind, caused by bacteria of the genus Mycobacterium. 

 Tuberculosis is not solely a human disease, but is also en- 

 countered in lower mammals, in birds, and in certain cold- 

 blooded animals. In contrast, although a leprosy-like disease 

 has been identified in chimpanzee and in "wild" armadillo, as 

 an important and relevant epidemiological entity it is essen- 

 tially a human disease. Historically, on current evidence, 

 both infections are relative newcomers to the spectrum of 

 human disease. Perhaps more than any other disease in hu- 

 man history, leprosy has generated strong social reaction, 

 which persists overtly or as undercurrent in many parts of the 

 world today, has stimulated legislation, and given rise to 

 abhorrence. These emotive aspects of disease have spanned 

 many centuries. The reactions at epidemics of plague were, 

 undoubtedly, of greater intensity, but these were short-lived 

 and, in themselves, were epidemic. It is likely therefore that 

 the manifold reactions and opprobrium of leprosy were due 

 to the chronicity of the disease, its mutilating and pitiful 

 presentation, and to ill-founded theology. But, to what extent 

 this last was a reactive root is not known; Christian and non- 

 Christian medieval communities both practiced segregation 

 and demonstrated ambivalence of attitude, harsh and benefi- 

 cent, toward the leprosy sufferer. Tuberculosis was the sub- 

 ject of Touching for the King's Evil in the European Middle 

 Ages, but little other public reaction was engendered. In 

 terms of mortality, tuberculosis was the "Captain of all the 

 men of death." 



Bacteria of the genus Mycobacterium are responsible for 

 more human suffering and misery than any other bacteria. 

 Both tuberculosis and leprosy are eliminated as serious 

 health problems in Western Europe and yet. in past centuries 

 both were of immense significance therein. Today both arc 

 still of immense significance in many parts of the world, 

 particularly the tropics and subtropics. In Western Europe, 

 the increasing eradication of tuberculosis is due largely to 

 improved socioeconomic conditions and, more particularly, 

 to prudent public health measures. Eradication of bovine 

 tuberculosis, mass immunological screening of juveniles, 

 and appropriate vaccination are eliminating the disease. The 



Zagreb l^leopaihology Symp. 1988 



demise of tuberculosis is, therefore, due to human agency. 

 Not so with leprosy. The changing patterns in leprosy preva- 

 lence and in clinical intensity have been, and to some extent 

 still are, totally independent of any human activity directed 

 toward control and eradication. 



This paper seeks to review the history of tuberculosis and 

 leprosy in antiquity and to consider the historic changing 

 patterns within the concept of modern epidemiology and 

 immunology. 



Bacteriology 



The bacteria responsible for the human diseases of leprosy 

 and tuberculosis are members of the genus Mycobacterium. 

 This genus, which contains about 30 species, is characterized 

 by the ability of the bacilli to retain staining by fuchsin and 

 related bacteriological stains in the laboratory after exposure 

 to weak acids. This acid-fast property is not, however, 

 unique to the mycobacteria. Of greater genus specificity and 

 taxonomic value is the nature of the lipids within the bacterial 

 cell walls. It is likely that the virulence or pathogenicity of 

 each species is intluenced by the specific lipid content. It is 

 also likely that the host immunological response to invasion 

 by the bacteria is infiuenced by the lipid content. 



Of all the mycobacterial species, M. leprae is unique in 

 that it is not possible, with present laboratory methods, to 

 culture the bacterium in vitro. As a pathogen, its natural host 

 is mankind, although, as noted, a leprosy-like disease has 

 been recorded in chimpanzee and armadillo. Antigenically. 

 M. leprae has been shown to be related to M. vaccae. an 

 environmental saprophyte (Grange 1980:30). An evolution- 

 ary significance of this finding has not, as yet, been demon- 

 strated. 



M. tuberculosis, in common with all other mycobacteria 

 except M. leprae, is culturable in vitro. M. tuberculosis is. 

 however, unique among the culturable mycobacteria in pos- 

 sessing no environmental saprophytic strains. It is an obli- 

 gate pathogen. Many of the other culturable mycobacteria 

 may be responsible for disease in man or animals, and Col- 

 lins and Grange (1983:18) remark that not all mycobacteria 



23 



