157 Yaws

This disease has suffered from variable and confus­ing descriptions. It is now generally called yaws, although the term framboesia is also still in common use. Although primary, secondary, and tertiary stages of the condition are recognized, further subdi­visions have been made that are associated with various alternative terminology.

Yaws is generally considered to be a highly conta­gious disease in tropical areas of the world, and in populations with limited hygiene. It is characterized in the early stages by variable cutaneous changes, and eventually affects joints and bones. The causal organism is considered to be Treponema pertenue, although the taxonomy of the pathogenic trepo­nemes is in some doubt, and some reclassification may well take place in the near future. An incuba­tion period of up to 28 days is followed by the appear­ance of the primary lesion, 2 to 5 centimeters in diameter, which develops into granular excrescences at times with lymph node enlargement. Further eruptions take place, which can be characterized by a “waxing and waning” of successive lesions. Single or multiple lesions can eventually develop on the feet (“crab yaws,” “ulcerative plantar papules”) and are some of the most painful and disabling lesions of all. Eventually, in what some would see as a tertiary stage, there can be patchy depigmentation, deep de­struction and remodeling of bones, and gangosa (changes to nasopharyngeal structures). The inter­nal organs are not normally involved, and in this respect it contrasts markedly with the sister trepone- matosis venereal syphilis.

Distribution and Incidence

As a result of the intensive campaign against yaws that was carried out in the 1950s by the World Health Organization, the disease is no longer pres­ent in many populations where previously it was a serious health threat. Nevertheless, some comment on its previous geography and ecology is worthwhile, particularly as this may tell us something about its adaptive evolution.

Exceptions to the geographic rules that might be seen to govern this condition are not difficult to find. For instance, in the case of mean annual rainfall, yaws was usually found in areas where there is 50 to 75 inches of rain a year, but it has occurred in drier climates as represented by parts of Madagascar, In­dia, and Bolivia. In all, there were probably some 50 million yaws cases in the world half a century ago.

In the 1940s and early 1950s, estimates of yaws prevalence were made in various areas of the world, partly in relation to yaws eradication programs. Al­though regional figures have now dropped radically, it is pertinent to the history of the subject to note the extent of the previous evidence, and the variation found. In the case of most of the New World, al­though yaws was probably introduced by slaves cen­turies ago, no significant incidence has remained into this century. However, in the Caribbean area, which had been varyingly affected by the slave trade, yaws displayed some contrasts. Thus, Cuba was reported as having a low frequency of yaws, whereas in Haiti 60 to 80 percent of the rural popula­tion were estimated to have had yaws. Similarly, Jamaica registered 70 to 80 percent frequency fig­ures in some districts. In South America, Brazil was known to have many cases, especially in the north­ern regions where 350,000 cases were at one time noted. In Colombia, there was also regional varia­tion, with the Pacific coast regions reporting 80,000 cases (with a general rate of 43.5 per 100,000).

In the Old World, the disease was endemic in parts of Africa, Asia, and the Pacific. In Africa, quite high frequencies were found in some areas, although pos­sibly the highest incidences occurred in Asia and the Pacific. In 1945, in the area then designated the Belgian Congo, there were 325,994 cases; and, in the same year, Tanganyika recorded 69,000 cases. Also about this time, frequencies in French West Africa varied from 0.02 percent (Niger) to 6.3 percent (Ivory Coast). French Equatorial Africa similarly had frequencies ranging from 0.1 percent (Chad) to 4.3 percent (Gabon), and the regional incidences in Uganda varied from 2 percent to 17.5 percent.

Yaws was also an important disease in the more tropical areas of Asia. In the Indian territory of Madhya Pradesh, 5.6 percent of the population was recorded as having yaws. Indonesia may have had as many as 10 million yaws cases before its anti-yaws campaign had any effect, and in some areas possibly 60 percent of the population had some experience of the disease. Thailand may also have had some 1.4 million cases prior to its current reduction, and in Laos, too, 1 to 15 percent of the population was thought to be affected.

Territories of the Pacific area showed some surpris­ing frequencies, and clearly the relatively small populations of most of the islands did not prevent the spread of this disease. It was frequent on Guam, and, in 1953, on Simbo Island 20 percent of the general population had experienced yaws (and 78 percent of the children had been affected at some time). Also in the early 1950s, it was recorded that 17 percent of the population of Wallis Island and 18 percent of 80,000 Western Samoans had yaws.

This evidence of yaws in various parts of the world just prior to the antibiotic campaigns for its eradica­tion helps to emphasize points of historical interest. One is that yaws probably had a relatively limited distribution in the New World.

Etiology and Epidemiology

Yaws is one of the four chronic infectious trepo­nemal diseases that affect humans, and, in contrast to pinta, endemic syphilis, and venereal syphilis, it appears to be especially adapted to hot and humid tropical and subtropical environments. Rural popu­lations were probably more affected than urban groups. The causal organism has been given sepa­rate species status, Treponeme pertenue, but the taxonomy of the treponematoses deserves reevalua­tion. The microorganism was discovered by Aldo Castellani in 1905, and since then its morphology has been to some extent revealed, especially by electron microscopy. Differences between the patho­genic treponemes have not, however, been resolved at this level, and it now seems unlikely that signifi­cant morphological differences will appear between T pertenue and Treponeme pallidum (which causes syphilis).

Only humans appear to be the natural hosts of all the pathogenic human treponemes. None have so far been cultivated in artificial media, and there is still much to Ieam about their biological characteristics. In terms of the nature of the lesions produced, the most divergent forms are yaws and venereal syphi­lis. There is variable cross-protection once an individ­ual has one variety of treponeme and comes into contact with another form.

The site of entry for yaws treponemes is not usu­ally the genitalia, but often the legs. Large numbers of treponemes are probably unnecessary to instigate the disease.

Like endemic syphilis, yaws characteristically de­velops during childhood by nonvenereal contact. Eventually, after chronic progress of the disease, over 8 months or more, individuals commonly un­dergo spontaneous cure, although some cases con­tinue to a tertiary stage.

Immunology

There appears to be no significant natural resistance to infection by yaws or other pathogenic treponemes. However, there is clear evidence that some individu­als can develop specific resistance or immunity fol­lowing infection with these treponemes. Thus, early clinical lesions can disappear, so there can be an asymptomatic or latent period, and this may or may not be followed by later-stage symptoms. The plasma cells and lymphocytes present in treponemal lesions indicate local antibody formation and some degree of immunologic response. Sera from yaws and the other pathogenic treponemes react to the same antigens.

Clinical Manifestations and Pathology

The progress of yaws seems best described in two major stages: an early phase with initial and secon­dary lesions; then a late stage, which usually devel­ops after some years.

The clinical features of early yaws can be summa­rized as follows. In the region of entry of the trepo­nemes, the primary lesions develop within the first 8 weeks. It is usual to find that the legs are involved first, the lesion being in the form of a large rounded itching papule, which is usually less than 5 or 6 centi­meters in size. There is the possibility that it will ulcerate or become secondarily infected. Crusting of the ulceration occurs, and eventually a raspberry­like granuloma develops beneath. Bleeding may oc­cur, and there can be a yellowish discharge.

Within 3 to 6 weeks after the initial lesion, secon­dary eruptions occur, and extend all over the body. These can continue for up to 2 years. Variants of these yearly yaws lesions have been given a confus­ing range of names. According to the 1951 WHO nomenclature, they may be summarized as follows.

Circinate (annular or ringworm) yaws lesions tend to encircle an area of skin, which may be several centimeters in diameter. Macular eruptions may oc­cur and can be depigmented or partly hyper­pigmented (peripherally). These disappear within a few weeks or months. The papular or “lichenous” rash can be regional or cover the whole body with small papules, usually for not more than a few weeks. Plantar and palmar lesions can be ulcerative or nonulcerative. In the case of painful ulcerating soles, the individual tends to walk on the outer border of the foot in a crablike fashion (“crab yaws”). Alterna­tively, in the nonulcerating lesions, there may later be a worm-eaten appearance associated with thick­ened dry Iiyperkeratotic skin. In the moist parts of the body (anus, vagina, mouth, nose, axillae), raised

VIIL Major Human Diseases Past and Present condylomatous areas resembling the condylomata of venereal and endemic syphilis can occur.

In the later stages of yaws, usually after 5 years, further lesions may occur in individuals whose condi­tion has not become fully latent. In particular, there can be a nodular “lupoid” involvement of the skin, with the formation of granulation tissue, ulceration, and scar formation. In this late stage, there may also be one or a few large ulcers (“gummatous ulcera­tion”) lasting for years. Disturbances in pigmenta­tion may further occur, being usually patchy. Possi­bly the most significant of the late stages of yaws are those that cause significant changes in the bones, for these can clearly be searched for archaeologically and thus may provide an ancient perspective to the history of this disease. Parts of the skeleton, espe­cially the long bones, may show a range of changes from periostitis to deep cavitation and shaft swell­ing. In children there can also be dactylitis, which can produce remodeling and expansion of one or more phalanges, especially of the fingers. Also, the vault of the skull may be affected, causing localized cratering or more widespread osteitis and eventual stellate scarring. Most destructive of all is gangosa (rhinopharyngitis mutilans), which is characterized by massive destruction of the nose, palate, turbin­ates, and vomer.

History and Geography

It is important to emphasize at the outset that the history of yaws has been, to some extent, mixed up and confused by studies of syphilis. This, of course, is understandable, in that they are closely related treponemal diseases, and even now can be confused at a clinical level. It is thus small wonder that earlier writers could mistake one condition for the other, or are vague about the actual nature of the disease. Possibly the best example of this confusion is pro­vided by writings on the Australian aborigines, in whose tribes yaws may have been a long-term pre­European problem. Indeed, the Aranda tribe has an old established name, Irkintja, for the condition that many observers believed was syphilis (Hackett 1936b). This does not mean that all of the earlier medical writers were wrong, and Robert Koch, in a 1900 report to the German government, perceptively wrote that in the Bismarck Archipelago he had seen places where practically all children were infected with yaws, and that framboesia was frequently mis­taken for syphilis by both laypersons and medical practitioners. Koch went on to say that the alleged great epidemics of syphilis in the South Seas were in large part the result of this same misdiagnosis.

Antiquity Through the Fifteenth Century

Although it has been suggested that the biblical condition “blains” (Exodus IX) could have been yaws, and similarly that the reference by Pliny the Elder (first century A.D.) to a yawslike eruption of the face could have indicated early treponemal dis­ease, there is really no ancient written records that can be taken seriously as good evidence. On the other hand, the archaeological record does appear to provide clear proof of the antiquity of the treponemal diseases.

Regarding the medieval period, European history provides some facts that seem relevant to a full un­derstanding of the history and spread of yaws. In 1367 Marco Pizziani explored along the African coast, and by 1470 others had sailed south as far as the Equator. Portuguese settlements were estab­lished, linked to the slave trade, and these intimate contacts between widely different peoples and envi­ronments provided opportunities for the movement of disease as well as people. Although the estimated figure of between 300,000 and 400,000 Negro slaves arriving in Portugal by the end of the fifteenth cen­tury may well be too high, there is no doubt that we must recognize this as a significant corridor for the potential shunting of disease, including yaws, to other areas, including northern Europe. Moreover, the slaves did not simply move toward Europe and western Asia.

Sixteenth Through Eighteenth Century

At the very beginning of the sixteenth century, the first consignment of slaves from Africa arrived in His­paniola and, following this, millions more reached the New World. It was thus that yaws became estab­lished to varying degrees, depending on social and environmental factors, in various parts of the Ameri­cas. In 1648 Willem Piso, a Leiden doctor associated with the Dutch West India Company, which occupied a part of Brazil for a few decades, wrote in his Historia Naturalis Brasiliae of treponematosis in that country, mentioning a condition called “bubas” which he dis­tinguished from the “Spanish pocks.”

Earlier, in 1642, Jacobus Bontius, another Leiden doctor, had written of witnessing yaws as a result of his travels in the East Indies. In the Moluccas, the frequency of yaws led Bontius to call it a “common plague.”

From the middle of the seventeenth to the end of the eighteenth century, there were a series of writ­ings that consolidated the view that yaws was a dis­tinct disease. Some of this evidence is so skimpy as to provoke only the suspicion of yaws as, for example, the 1720 “epidemic” in Scotland of “sibbens,” with symptoms suggestive of intruded yaws.

On the other hand, John Brickell of North Caro­lina, writing in the 1730s, distinguished yaws and syphilis, and noted that the former condition was “brought hither by the Negroes from Guinea” and was “seldom cured by mercurials.” In the West In­dies physicians who attended slaves came to know the disease well. They, too, believed its origin was in Africa. As in Africa, yaws was a disease mostly of children in the Caribbean, and many plantations erected yaws houses. Edward Bancroft, an eight­eenth-century physician who gained experience with yaws in Guiana, South America, concluded that it could be transmitted by flies. This view was accepted by various medical writers in the follow­ing decades.

In this closing period of the eighteenth century and the first decades of the next, the stages of yaws development were slowly being understood. Vaccina­tion was also tried in an attempt to prevent the disease, and positive results were claimed. Some­what more alarming in humanitarian terms, the experimental injecting of slaves was carried out, at times with “success.” Of special value were experi­ments on humans known to have already suffered from yaws, the negative results showing that immu­nity to secondary infection was possible.

Nineteenth Through Twentieth Century Gangosa, meaning nasal voice, was first mentioned in the literature by a Spanish medical committee in 1828, and by 1891 J. Numa Rat had discussed these lesions in rhinopharyngitis mutilans and viewed them as an indication of the tertiary stage of yaws. Similarly, E. C. Stirling in 1894 was the first to note “boomerang leg” (also called sabre tibia), which was a later-stage yaws feature he saw in Australian aborigines.

The question of the taxonomy of the pathogenic treponemes was opened up for debate in 1900, when Joseph Hutchinson agreed that, contrary to grow­ing opinion, yaws and syphilis were simply differ­ent patterns of the same disease-an argument that was to be strongly defended later by Ellis H. Hudson (1946, 1958). But during this century, the treponemal diseases have tended to be worked on more and more in isolation. Thus, R. L. Spittel (1923) concentrated not only on yaws but specifi­cally on parangi, the form with which he had had considerable experience in Ceylon. Perhaps the most versatile treponematologist has been C. J. Hackett, whose field work in the 1930s took him to tribal communities in Australia and Africa. His contributions dealing with the bone changes in yaws and syphilis have been especially significant. These findings in turn are helping physical anthro­pologists to trace the history of these diseases in human skeletal materials. It is hoped that such efforts will soon produce major breakthroughs in our knowledge of the history of the treponematoses.

Don R. Brothwell

Bibliography

Brickell, John. 1737. Natural history of North Carolina. New York.

Castellani, Aldo. 1905. On the presence of Spirochaetes in two cases of ulcerated parangi (yaws). British Medical Journal ii: 1280, 1330—1, 1430.

Dijke, M. J. V., C. Bakker, and H. W. Hoesen. 1921. On the etiology of rhinopharyngitis mutilans. In Transac­tions OftheFourth Congress of the Far Eastern Associa­tion OfTropical Medicine, 2: 129-37. Weltevreden.

Fox, H. 1944. Yaws (framboesia tropica). In Clinical tropi­cal medicine, ed. A. T. Bercovitz, Chapter 23, New York.

Guthe, T., and R. R. Willcox. 1954. Les treponematoses: Problfeme mondial. Chronique de TOrganisation Mond­iale de la Sante 8: 41—122.

Hackett, Cecil J. 1936a. Boomerang leg and yaws in Aus­tralian aborigines, Monograph No. 1. Royal Society of Tropical Medicine and Hygiene. London.

1936b. A critical survey of some references to syphilis and yaws among the Australian aborigines. Medical Journal OfAustralia i: 733—45.

1951. Bone lesions of yaws in Uganda. Oxford.

Hackett, Cecil J., and L. J. A. Loewenthal. 1960. Different diagnosis of yaws lesions. World Health Organization Monograph Series No. 45. Geneva.

Hermans, E. H. 1931. Framboesia tropica. Acta Lei- densia Scholae Medicinae Tropicae, Vol. 6. Lugduni- Batavorum.

Hill, K. R., R. Kodijat, and M. Sardadi. 1951. Atlas of framboesia. World Health Organization Monograph Series No. 5. Geneva.

Hudson, Ellis H. 1946. Treponematosis. New York.

1958. Non-Venereal syphilis. Edinburgh.

Hutchinson, J. H. 1900. A discussion on yaws. British Medical Journal ii: 561.

May, Jacques M. 1958. The ecology of yaws. In The ecology of human disease, Chapter 16. New York.

Rat, J. N. 1891. Framboesia (yaws). London.

Schell, R. F., and D. M. Musher, eds. 1983. Pathogenesis and immunology of treponemal infection. New York.

Spittel, R. L. 1923. Framboesia tropica (parangi of Cey­lon). London.