Endemic treponematosis and tuberculosis 



in the prehistoric southeastern United States: 



Biological costs of chronic endemic disease 



Mary Lucas Powell 



1 he importance of infectious disease as a selective force in 

 human adaptation has been argued eloquently during the past 

 quarter century (Alland 1970; Armelagos et al. 1978; 

 Buikstra 1981; Buikstra and Cook 1980; Burnet and White 

 1972; Cockbum 1973; McNeal 1976; Ortner and Putschar 

 1981). Many recent assessments of health in prehistoric pop- 

 ulations have treated only in general terms the observed prev- 

 alence of nonspecific periostitis, osteitis, and osteomyelitis, 

 with little or no consideration of specific infectious diseases. 

 The most commonly reported nonspecific lesion, periostitis, 

 may represent illness caused by endogenous bacterial and 

 viral infections, certain endemic (and more rarely, epidemic) 

 infectious diseases, nutritional disorders, trauma, or a vari- 

 ety of congenital syndromes (Greenfield 1980; Jaffe 1972). 

 Its mere presence in an individual or a population reported 

 without an epidemiological context is of minor significance 

 in evaluation of the biological costs of infectious disease 

 experience. 



Differential diagnosis of specific infectious diseases re- 

 quires familiarity with the pathogenesis and epidemiology of 

 the diseases in question. Certain infectious diseases such as 

 treponematosis and tuberculosis produce both pathog- 

 nomonic skeletal pathology (e.g., caries sicca in the former, 

 extensive vertebral destruction in the latter) and nonspecific 

 response. Ortner and Putschar (1981:105) note that "infec- 

 tious conditions affecting the skeleton tend to be subacute, 

 chronic diseases and may not be the immediate cause of 

 death." Because bone lesions typically occur relatively late 

 in the progress of disease subsequent to considerable soft 

 tissue involvement, their presence is indicative of relatively 

 long-term immune response. Some chronic diseases typ- 

 ically produce abundant skeletal morbidity yet rarely result in 

 death, because of the nature of their pathophysiological 

 effects, while others may produce high mortality but few 

 cases of skeletal involvement (Hackett 1951; Robbins and 

 Cotran 1980). This paperoutlinesbriefiy the different biolog- 

 ical costs of two chronic infectious di.seascs with distinctive- 

 ly different patterns of skeletal involvement and mortal im- 



iagrtb Paleopathology Symp. 1988 



pact, endemic treponematosis and tuberculosis, that have 

 been recently identified in skeletal samples from late 

 prehistoric American Indian populations in Alabama and 

 Georgia. 



Endemic treponematosis and tuberculosis 



Yaws, endemic syphilis, and venereal syphilis are considered 

 to be closely related disease entities because of the similarity 

 of their causal organisms and the morphology of their lesions 

 of skin and bone (Grin 1953; Hackett 1976; Hudson 1958; 

 Turner and Hollander 1957). As regards levels of morbidity 

 and mortality, however, the first two are radically different 

 from their more dangerous relative, being both more widely 

 prevalent and more benign because of their mode of trans- 

 mission and their pathophysiological effects. They are typ- 

 ically contracted in early childhood through direct contact 

 with infectious skin lesions rather than through venereal 

 transmission. Prevalence levels in endemic regions approach 

 100%, and lesions occur in approximately 50% to 75% of 

 late secondary and tertiary cases, resulting from hyper- 

 allergic response to superinfection by the sensitized hosts 

 (Hackett 1951). Both congenital transmission and invasion 

 of vital organ systems are rare, in contrast to the well- 

 documented effects of venereal syphilis (Grin 1956; Murray 

 et al. 1956). These diseases do not noticeably dampen fertil- 

 ity, and exert a negligible impact upon mortality except indi- 

 rectly through secondary bacterial or mycotic infection of 

 skin lesions. 



In his comprehensive study of endemic yaws in Uganda 

 ( I95I ), C.J. Hackett sought to document the complete range 

 of bone lesions observed radiographically in patients diag- 

 nosed by serological analysis. He noted in his introduction, 

 "It is not the differential diagnosis of the changes present in 

 one patient, but of those ... in a whole population that is 

 being considered." Hackett found that while some patients 

 displayed "classic" bone lesions characteristic of late second- 

 ary and tertiary yaws (sabre shins, polydactylitis, and os- 



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