Human major infections: Tuberculosis, treponematoses, leprosy-A paleopathological perspective of their evolution.

The key to evolution is reproduction. Pathogens can either kill the human host or can invade the host without causing death, thus ensuring their own survival, reproduction and spread. Tuberculosis, treponematoses and leprosy are widespread chronic infectious diseases whereby the host is not immediately killed. These diseases are examples of the co-evolution of host and pathogen. They can be well studied as the paleopathological record is extensive, spanning over 200 human generations. The paleopathology of each disease has been well documented in the form of published synthetic analyses recording each known case and case frequencies in the samples they were derived from. Here the data from these synthetic analyses were re-analysed to show changes in the prevalence of each disease over time. A total of 69,379 skeletons are included in this study. There was ultimately a decline in the prevalence of each disease over time, this decline was statistically significant (Chi-squared, p<0.001). A trend may start with the increase in the disease's prevalence before the prevalence declines, in tuberculosis the decline is monotonic. Increase in skeletal changes resulting from the respective diseases appears in the initial period of host-disease contact, followed by a decline resulting from co-adaptation that is mutually beneficial for the disease (spread and maintenance of pathogen) and host (less pathological reactions to the infection). Eventually either the host may become immune or tolerant, or the pathogen tends to be commensalic rather than parasitic.

Treponematosis in the eastern highlands of New Guinea.

Serological tests for treponemal disease were undertaken among the inhabitants of 10 census units in the Eastern Highlands of New Guinea. Many sera gave reactive results to some or all of the tests performed. To exclude biological false positive reactions the Treponema pallidum immobilization (TPI) test was carried out on each serum, the results being taken to indicate the presence or absence of treponemal disease in the individual. Clinically, leprosy and malaria were rare and no cases of active yaws were seen. Some middle-aged people showed clinical evidence of old yaws infections. The prevalence of treponemal disease in the census units varied from 3.9% to 79.2%, males having a higher prevalence than females. The children under 15 years showed no serological evidence of treponemal disease in all but 3 units, in which the prevalence ranged from 14.3% to 40%. It is concluded that the treponemal disease involved was yaws. Special interest lies in the non-infected children and adults who have no relative cross-immunity from yaws in a country which is rapidly developing.