Introduction

Mali's great Inland Delta of the Niger River (IDN) is an area comprised of seasonal flood plains and marshes the size of the state of Maine [1]. Over the past several decades, archaeologists, art historians, and anthropologists have uncovered the existence of complex societies in this area beginning in approximately 200 B.C. [2,3,4]. Of significance has been the discovery of an ancient town, Djenné-Jeno, where among other archaeological objects, figurative terracotta statues have been found [5,6,7].

This ancient site thrived until about 1700 A.D. In time, it was overshadowed by a newer Muslim town, Djenné, some three kilometers away [8]. For several hundred years, from 1100 A.D. until 1700 A.D., rich traditions of representational art flourished in Djenné-Jeno and surrounding areas. This art included objects in wood, metal, and terracotta [5]. It would be the terracotta figures that would most attract the attention of scholars, curators, and art collectors in the contemporary era (Fig. 1).

Fig. 1
figure 1

(Reproduced with permission of the Metropolitan Museum of Art)

Thirteenth century seated Djenné-Jeno terracotta figure. There are three vertical linear lines of round excrescences on the back interspersed with two vertical lines of round pitted circles. The excrescences may represent keloids intentionally created by cicatrization for beautification purposes. Height: 10 × 12 in. Accession Number: 1981.218

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Early Archaeological Investigations

As far as can be determined, the first Djenné-Jeno statuettes were discovered in 1933 by C. Daire, a local French school teacher, at Kaniana in the IDN. Aware of the importance of this finding, he wrote a letter to the Institut Français d'Afrique Noire (IFAN) in Dakar about these statuettes. Dated 16 February 1933, his letter provided significant details about these objects. He stated that they were made by the wives of blacksmiths as toys for children or as idols for the clans that occupied the area [9]. It is significant that Barbara Frank has documented the role of the wives of blacksmiths in Mali as potters [10]. She has reasonably put forth the view that the ancient Djenné-Jeno terracottas were perhaps made by the wives of blacksmiths [11].

During the French colonial era, several researchers uncovered terracotta statues as well as terracotta jars and other archaeological objects in the IDN. Among the earliest of these was Gilbert-Pierre Vieillard (1899–1940), who was an ethnologist and linguist. His principal research was among the Peul of the Fouta Djallon Mountains of Guinea [12]. He was a mentee of the renowned French naturalist and founder of the IFAN in Dakar, Théodore Monod (1902–2000). Toward the end of his time in West Africa, Viellard studied the Peul of Macina in what is now Mali. While there, he excavated what is probably a burial mound, and discovered terracotta figures. He published his findings in 1940, the year that he was killed in the World War II Battle of Lorraine [12, 13].

Another mentee of Théodore Monod was Georges Szumowski (1909–2004), who was the Chief of the Archaeology and Prehistory Section of the IFAN. Szumowski was of Ukrainian origins, and possessed a doctorate in archaeology. He was a highly productive archaeologist in the French Sudan (now Mali) in the 1950s. He made important discoveries during his archaeologic excavations. At Bankoni, near Mali's capital of Bamako, he excavated a stone pseudo-tumulus. He found in it a large terracotta statue of a style quite distinct from those of Djenné-Jeno [14]. He also conducted extensive digs in the IDN where he unearthed a terracotta statue [15].

Szumowski later immigrated to the United States where he joined the faculties of Long Island University and Fordham University in New York City. He also served as a Ukrainian Orthodox priest for 60 years, and passed away at Hospice House in Savannah, Georgia at the age of 95 years in 2004.

There were also other researchers who uncovered terracotta statues in the IDN. Among them were Raymond Mauny (1912–1994) and Annie Masson-Détourbet [16, 17].

Recent Archaeological Research and Studies

The American anthropologists and archaeologists, Roderick J. McIntosh and Susan Keech McIntosh, began archaeological excavations in the IDN in the 1970s. They have shed much light on the ancient civilizations that once flourished in this region. Their excavations uncovered terracotta figures or portions of them in physical locations that would seem to indicate that they may have been used in rituals directed toward ancestor worship or else when immured in the foundations of houses, as power objects to ward off building damage during the flood season [18]. One of the statues unearthed by them is a semi-recumbent figure found in an ancient rubbish tip with a head alongside of it. However, it is thought that the original head was removed and another placed next to the statue. One possibility, obviously impossible to prove, is that the decapitating and discarding this figure was in response to the growing presence of iconoclastic Islam in Djenné-Jeno [19].

In recent decades, Malian and French archaeologists have conducted extensive investigations throughout many areas of Mali. Their studies have led to a greater understanding of the peoples who inhabited this region over the centuries [20]. Mamadou Sarr, who this writer knew, studied the hillocks of the Sevaré Plain near the town of Mopti [21]. Samuel Sidibé, then the Director of the Musée National du Mali, conducted an extensive inventory of archaeologic sites in the Upper Delta of the Niger around the town of Diré [22].

Dutch and Swiss archaeologists have also completed studies in the IDN [2, 23]. The Swiss group, formally known as the Mission Archaéologique et Ethnoarchaéologique Suisse en Afrique de l'Ouest, began their field studies in 1988. A number of this group's studies focused on the abandoned nineteenth century town of Hamdallaye, the capital of the former Peul Empire of Macina [24]. They also studied pottery traditions among the peoples of the IDN. They documented the central role of women in the creation of ceramic pottery.

Unauthorized Excavations

The Sahelian drought of the mid-1970s caused great hardships for the peoples of the Inland Delta of the Niger [25]. Poor crops and livestock losses created desperate economic and social conditions for peasant farmers and herdsmen. This, coupled with the presence of art dealers in Mali who had commercial links with counterparts in Europe and North America, gave rise to large-scale looting of archaeological sites in Mali. This was especially significant in the Niger Valley. This looting and an illegal traffic in terracotta figures was especially intense in the IDN. Fostering it was the development of an international demand by art collectors for these objects. This looting initially took the form of surface scraping for artifacts. However, it later evolved into well-organized digging involving groups of men. The consequences of this looting include damage to archaeological objects and their removal from their original contexts [26]. It is broadly estimated that several hundred and perhaps more terracotta figures were excavated in this manner. Unfortunately their original ethnographic contexts are lost.

The international demand for these objects eventually stimulated the creation of statuary copies in Mali. Many of these are architectonically similar to authentic ancient terracotta, and cannot be distinguished from the latter solely on the basis of form. However, thermo-luminescence analyses can determine within a certain range the age of the fired clay (Fig. 2).

Fig. 2
figure 2

Replica of Djenné-Jeno terracotta horse and rider. Height: 14 in. Dated in 2015 by thermo-luminescence analysis by Oxford Authentication Ltd. to less than a hundred years (Gift given to the author in 2006 by the family of the late Gani Alfarou Diallo of Mopti, Mali. Photograph by the author)

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Styles of Djenné-Jeno Statues

Although it has not always been possible to determine the original contexts of many Djenné-Jeno terracotta statues, it has been possible to identify various styles and the master hands that may have made them [5,6,7]. Bernard de Grunne is an art historian who has meticulously studied the iconography of these terracottas for many years [27]. He has concluded that they were part of a pantheistic religion that was widely practiced in this area of West Africa [5].

Djenné-Jeno terracotta statues were not only created in a variety of forms, but often their surfaces were modified to depict diverse postures, surface adornments, physical disabilities, and disease. All of these visible forms and surface treatments have invited interpretations. These have primarily been offered by African art historians, archaeologists, and social scientists, largely based on surmise. While the terracotta statue shown in Fig. 3 would likely be diagnosed as representing smallpox, the surface lesions could in fact depict the lesions of secondary stage syphilis or generalized urticaria because of their large diameters and relatively flat appearance. (Fig. 3).

Fig. 3
figure 3

(Reproduced with permission of the Museo d'Arte e Scienza, Milan, Italy)

Djenné-Jeno terracotta figure depicting numerous large flat and round lesions that are widely distributed on the body

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The above said, interpreting excrescences on the surfaces of Djenné-Jeno terracottas is further challenged by the stylization present in these statues. As a result, the lesions may not be realistically presented either as to form, size, or anatomical distribution. In the case of the statue under discussion here, the differential diagnosis could also reasonably include bejel (endemic syphilis), chickenpox (varicella), plague, and onchocerciasis. However, these possibilities would have to meet epidemiological criteria, including historical occurrence in the region and significant levels of prevalence, morbidity, and mortality to qualify for memorialization on terracotta statues.

A Medical and Epidemiological Approach to Identifying the Excrescences Depicted on Djenné-Jeno Terracotta Statues

Arriving at a definitive conclusion concerning what was being represented by the excrescences on the statues may never be possible. However, it is possible to identify likely probabilities based on a combined medical and epidemiological approach. The former utilizes a comprehensive approach to gathering information, in this case about objective evidence. The latter relies on considering those morbidities most likely present in the IDN during the time when these statues were made. The contemporary presence of diseases in this area has been relatively well documented since the beginning of the twentieth century. This knowledge can provide insight into the presence of these diseases in the past.

The Medical Approach to Identifying Possible Diseases Depicted as Excrescences on the Surfaces of Djenné-Jeno Terracotta Statues

A definitive diagnosis of any disease requires a well-established approach that begins with a medical history in which a patient describes symptoms and/or signs. This detailed history obviously cannot be used in addressing lesions depicted on these statues.

In living people, the physical examination is very comprehensive for an initial general medical visit, and focused for a specialty one. Concerning the statues, the approach is most analogous to a dermatologic examination. In this case, the usual observations about turgor, pallor, flush, cyanosis, abnormal pigmentation, and jaundice cannot be made. Nor can other observations be made such as atrophy, elasticity, moisture, and temperature.

In a dermatologic examination, lesions on the skin obviously receive special attention. Such lesions may include macules, papules, vesicles, pustules, blobs, rashes, ulcers, scales, crusts, desquamation scars, keloids, nodules, moles, warts, fibromas, keratoses, birthmarks, petechiae, ecchymosis, and purpura. The integumentary examination also encompasses the hair and nails.

Positive and negative findings are carefully noted at the completion of a medical history and physical examination. Based on these, a primary diagnosis is made. Differential diagnoses are also noted. These represent less probable causes of the illness that need to be either ruled in or out. Secondary diagnoses consisting of findings not related to a patient's chief complaint are also noted.

The final steps in establishing a definitive diagnosis include a range of appropriate laboratory and imaging studies and special procedures [28]. Sometimes, all of the above efforts cannot lead to a definitive diagnosis. In these instances, a probable diagnosis can be made.

Barriers to Making a Primary Diagnosis of Surface Lesions on Djenné-Jeno Terracotta Statues

It is obviously very challenging to make a primary diagnosis of the excrescences on the surfaces of Djenné-Jeno terracotta statues. The medical diagnostic processes discussed above are, in effect, reduced to visual inspection and deductive reasoning based on it. Visual inspection can inform about the relative size and form of dermatologic lesions, their frequency of depiction, and their anatomical locations. These observations can be supplemented by the historical epidemiology of diseases with prominent dermatologic manifestations, and which were associated with significant morbidity and mortality in West Africa. One might not be able to arrive at a primary or definitive diagnosis. However, this does not preclude arriving at a differential diagnosis or a provisional one based on statuary surface characteristics informed by historical epidemiologic evidence.

Epidemiological Considerations in Historical Context

The terracotta statues under discussion were created between 1100 and 1700 A.D. in the IDN in what is now Mali. Among 537 known intact statues, 225 (42 percent) demonstrate signs of illness that include dermatologic excrescences, scoliosis and other orthopedic deformities, goiters, and serpentine surface designs that could perhaps represent Guinea worm infection due to Dracunculus medinensis. These 537 statues have been dated by thermo-luminescence analysis. They are currently in museum and private collections. Most were excavated in the IDN over the past 40 years. Van Dyke found that among the 537 statues, 20 percent (107) exhibited dermatologic excrescences. She concluded that the majority probably depict smallpox [29]. This is a reasonable conclusion, but one that does not exclude other possibilities as she infers. Van Dyke cogently notes that caution needs to be exercised in the interpretations given to the surface forms present in these statues due to our general lack of knowledge of the belief systems of those who created them (Fig. 4).

Fig. 4
figure 4

(Blanpain Collection. Reproduced with permission of Bernard de Grunne)

Fragmentary torso of a Djenné-Jeno terracotta figure with excrescences that may represent smallpox. Height: 8 in. 1200–1400 A.D.

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An important and reasonable epidemiological assumption is that the dermatologic diseases depicted in a large number of the corpus of these statues had a high prevalence in the IDN during the periods when they were created. For this reason, the evidence that smallpox was being depicted is very strong [30, 31].

Gathering the Evidence

Although a number of authors have commented on the surface lesions present on the terracottas under discussion, none have approached the interpretation challenge from the medical and epidemiological perspectives that are employed here. In departing from usual practice in most scientific communications, I think it best to describe this author's educational and experiential credentials for so doing. Following graduation from medical school, I trained for several years in internal medicine, and then did a fellowship in tropical medicine after which I received a Master of Public Health and Tropical Medicine degree. For six years, as a medical epidemiologist with the U.S. Centers for Disease Control and Prevention, I participated in the smallpox eradication and measles control program in Mali, West Africa. During those years, I also assisted in the control of epidemics of yellow fever, cholera, and meningococcal meningitis. Smallpox was then a major disease problem in Mali, and was quickly brought under control through a strategy of ring vaccination of outbreaks [30,31,32,33,34,35].

The disease had an especially high prevalence among Peul and Tuareg nomads, and migratory Bozo fishermen in the IDN and along the course of the river [36,37,38].

The Evidence for Smallpox Being Depicted on Djenné-Jeno Terracotta Statues

Until it was eradicated from Mali in the 1970s, smallpox epidemics were common, especially in the IDN. Clinical cases, examined by this author, were often quite severe (Fig. 5).

Fig. 5
figure 5

Young boy with the papular stage of the smallpox rash. Village of Leillehoi, Cercle of Ansougo, Mali, 1967 (Photograph by author)

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The lesions usually appeared at the same time, in distinction to chickenpox (varicella) in which they come out in crops. The face and extremities of smallpox victims were heavily covered with lesions which progressed from macules to papules, vesicles, pustules, and eventually scabs. Not infrequently, the vesicles and the pustules that succeeded them were umbilicated in their centers, meaning they had slight indentations in them (Fig. 6).

Fig. 6
figure 6

Forearm and hand of a woman with the vesicular stage of the smallpox rash. Some of the lesions exhibit umbilication. Cercle of Koutiala, Mali, 1967 (Photograph by the author)

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Although the lesions of smallpox were centrifugal, meaning that they were concentrated on the head and extremities, they also appeared on the torso. Here, their numbers were variable from one patient to another. They also appeared on the palms of the hands, which does not usually occur with chickenpox (Fig. 7).

Fig. 7
figure 7

Young girl in the desquamation stage with smallpox lesions on the palms of her hands. Cercle of Koutiala, Mali, 1967 (Photograph by the author)

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The lesions of smallpox were deep seated in the dermis of the skin unlike those of chickenpox which are superficial. Besides the severity of the rash which could also appear in the throat and mouth and the eyes, smallpox caused a serious systemic illness characterized by high fever, malaise, chills, vomiting, and headache for a few days before the rash appeared. These prodromal symptoms do not occur with chickenpox.

All stages of the smallpox rash contained infectious viral particles, and could thus result in transmission of the disease to others. Once the scabs fell off, they left behind depigmented areas of the skin which were often pitted [39]. Re-pigmentation of these areas eventually occurred over a period of several months. (Fig. 8).

Fig. 8
figure 8

Young girl at the end of the desquamation stage of smallpox with resulting depigmentation of areas of lesions. Most of the lesions were centrifugal on the face, arms, and legs, with relatively few on the torso. Village of Tiedjena, Arrondissement of Kimparana, Cercle of San, Mali, 1967 (Photograph by the author)

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While we possess excellent documentation of clinical smallpox in what is now Mali in the twentieth century, evidence for its existence in West Africa is assumed for antecedent periods based on its presence nearby in Egypt and elsewhere. Hopkins describes evidence of its presence in three Egyptian mummies dating from 1570 to 1085 B.C. He also received permission from then President Anwar el Sadat of Egypt in 1979 to examine the front and upper half of the unwrapped mummy of Rameses V, who died in 1157 B.C. Hopkins confirmed a rash of elevated pustules that "were most distinct on the lower face, neck, and shoulders, but also on the arms" [40].

The conclusion here is that a disease such as smallpox that was present in Egypt a millennium and more B.C. must certainly have eventually reached the area of the IDN via trans-Saharan trade routes over the course of time. Consequently, it is reasonable to conclude that the creators of the Djenné-Jeno terracottas were familiar with the disease (Fig. 9).

Fig. 9
figure 9

(Chambaud Collection. Reproduced with permission of Bernard de Grunne)

Kneeling female Djenné-Jeno terracotta figure with primarily centrifugal excrescences that appear to represent smallpox. Height: 12 in. 1350–1550 A.D.

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Indigenous Therapeutic and Preventive Methods for Smallpox

The importance of smallpox as a cause of serious morbidity and mortality is evident by the therapeutic and preventive measures that the peoples of central Mali once used to deal with it. They employed a variety of topical, ingested, and inhalational treatments [41]. These were all part of a spectrum of traditional medical practices created to address a number of diseases [42].

In addition to therapeutic efforts, groups in Mali and elsewhere practiced variolation, which is the purposeful inoculation of smallpox virus material into the skin of healthy people. This was usually done during outbreaks and epidemics. While a variety of techniques were employed they all involved the use of a sharp instrument such as a thorn, the tip of a feather, iron rod, or knife. These were often inserted into a vesicle in someone with a mild case of smallpox. Then the material was scraped into the skin of a recipient. Various anatomical sites were selected for scraping in the fluid with the intent of producing a mild case of smallpox. However, severe cases often resulted [43, 44]. These were often fatal (Fig. 10).

Fig. 10
figure 10

(Kenis Collection. Reproduced with permission of Bernard de Grunne)

Kneeling Djenné-Jeno terracotta figure with very diffuse dermatologic excrescences that most likely represent smallpox. Height: 8 in. 1330–1530 A.D.

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Also known as smallpox inoculation, variolation was once widely practiced in Africa and elsewhere in the world including Europe and the United States [45,46,47,48,49]. The development of vaccination and its widespread adoption rendered variolation unnecessary. However, it continued to be practiced until the last case of the disease occurred in 1977 in Somalia.

The global effort to eradicate smallpox was led by the World Health Organization (WHO) under the leadership of Dr. Donald Ainsle Henderson, who had previously served as Chief of the Surveillance Section of the U.S. Centers for Disease Control and Prevention. Henderson brought to the global effort outstanding scientific abilities, great diplomatic and administrative skills, and a firm commitment to rid the world of smallpox [50].

In 1979, smallpox was declared eradicated by WHO [51]. A number of scientific papers as well as books have been written documenting the eradication of the disease [51,52,53,54,55]. Recently, Bob H. Reinhardt has written an excellent book that examines the eradication of smallpox as an example of U.S. medical and technological achievements, and political power set against the backdrop of the Cold War [56].

It should be noted that extensive efforts were made during the colonial era in sub-Sahara Africa to control smallpox. Recently, Schneider has contributed to our knowledge of these efforts by Belgian, British, and French administrations. In the French Sudan (Mali), smallpox was essentially endemic during this time with periodic epidemics in the 1930s, 1940s and 1950s, with 2982 cases in 1957 alone (33, 57).

The French regularly administered large numbers of smallpox vaccinations reaching as many as 950,000 during epidemic peaks. However, this locally produced liquid vaccine was very heat labile, and consequently often ineffective. Inadequate access to isolated and rural populations in Africa and elsewhere contributed to periodic outbreaks and epidemics. The development of heat stable lypholized smallpox vaccine in the 1960s and the meticulous maintenance of a "cold chain" of refrigeration, even in remote rural areas, resulted in the administration of 4,170,000 effective vaccinations in Mali between 1966–1970 in the American USAID-CDC smallpox eradication program [58].

The Evidence for Onchocerciasis Nodules Being Depicted on Djenné-Jeno Terracotta Statues

Onchocerciasis is a filarial parasitic disease transmitted by the bite of female Simulium blackflies of which there are several species. In sub-Sahara Africa, the Simulium damnosum species is a common vector. The parasite known as Onchocerca volvulus is transmitted by the blackflies to humans after they themselves become infected while biting someone who already has the disease. When biting infected persons, a blackfly ingests the microfilaria stage of the worm that lives in the skin of an infected person. After development in the fly, the now infected larva are injected into the skin when the fly next bites someone. These larva migrate to the subcutaneous areas where they develop into mature worms. Several male and female worms cluster in a nodule or cyst and produce microfilaria that lodge in the skin where they produce a variety of symptoms [59].

Pathologic Effects of Onchocerca volvulus

Nodules of various sizes develop beneath the skin in infected individuals where the adult worms can live for 15 years. They contain clusters of adult worms and microfilaria. Nodules can be few in number, and often form at the junction of long bones, on the pelvic girdle, on the shoulder and the head [60]. The presence of microfilaria in the skin gives rise to a variety of pruritic dermatologic symptoms and signs including papules [61].

Ocular involvement due to the migration of microfilaria can be extensive involving the cornea, retina, and other parts of the eye. Opacification of the cornea due to chronic inflammation leads to blindness over time. Many with severe onchocerciasis with blindness often live near or frequent fast-flowing streams and rivulets where blackflies breed. As a result, onchocerciasis is often referred to as River Blindness.

Female worms can produce as many as 1500 microfilaria a day. Most are produced during daylight hours, and this coincides with the diurnal biting habits of blackflies [62].

Epidemiological Evidence for the Depiction of the Dermatologic Lesions of Onchocerciasis on the Surfaces of Djenné-Jeno Terracotta Statues

Compared to the endemic-epidemic character of smallpox, onchocerciasis has historically been endemic. Present in a number of countries of sub-Sahara Africa, the disease has been endemic in western, central, and southern Mali, where ecologic conditions for blackfly breeding are ideal. Importantly, it is also present on and around the Bandiagara cliff system, with its many cascading streams that create oxygenation levels ideal for blackfly breeding.

The current administrative Cercle of Bandiagara encompasses most of this ecologic zone. Not surprisingly, health data for this cercle over the years have shown significant numbers of annual cases of onchocerciasis. The hilly and cliff-dominated terrain of Bandiagara lies 40 miles from the eastern border of the IDN, where the Djenné-Jeno terracotta statues have been found.

In 1966, 113 new cases of onchocerciasis were reported from the Cercle of Bandiagara. In Mali overall that year, 3,107 cases were reported, of which 1,035 were from the southern Cercle of Sikasso. In 1971, 6,756 cases were reported in all of Mali, of which 458 (7 percent) were in the Region of Mopti, whose subdivision, the Cercle of Bandiagara, accounted for most [63].

It is reasonable to assume that onchocerciasis is an ancient disease, and that it was present in and around the Bandiagara cliffs during the centuries when the terracotta statues were created. The proximity of this area and other endemic zones to the south of the IDN would have constituted sources of exposure to the disease to inhabitants of the latter. Such exposure could have occurred during travel for trade or while engaged in other activities including warfare (Fig. 11).

Fig. 11
figure 11

(Private Collection. Reproduced with permission of Bernard de Grunne)

Djenné-Jeno terracotta female figure depicting possible onchocercal nodules on the head, arms, and at the juncture of the long bones of the left arm. Height: 9 in. 1200–1400 A.D.

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Beliefs about Onchocerciasis in Mali

Between November 1969 and May 1970, a study was conducted of local beliefs and practices concerning both onchocerciasis and trypanosomiasis in western Mali. This study was undertaken within the context of a mass vaccination campaign against smallpox, measles, and yellow fever. During this campaign, people were also examined for trypanosomiasis and onchocerciasis. The population reached in this campaign was 538,280 distributed in 1,264 villages.

The 27-question survey was conducted in all of the villages visited. Questions elicited specific information about beliefs in the causes of both diseases, the vectors, ecologic factors, preventive measures and treatments [64].

Relevant to onchocerciasis, 11.6 percent of people examined had nodules, 1.6 percent were blind, and 5.5 percent had other types of onchocerciasis-caused skin lesions. These figures speak for a significant level of endemicity.

Each of the four ethnic groups (Bamana, Khassonke, Malinke, and Sarakole) surveyed had specific names for the nodules and for the blackfly. Of note is the fact that the nodules were viewed as congenital because so many older people had them.

Some village leaders among the Bamana verified the dermatologic lesions as associated with being close to a stream or river, and had participated in voluntary village relocation. They believed that spirits in the water caused the illness, including blindness. There was no recognition of a relationship between blackflies and the disease [65].

The Control of Onchocerciasis in West Africa

Early drugs for the treatment of onchocerciasis were of limited effectiveness because while they were microfilariacidal, they had little effect on the adult worms. In 1981, however, a new drug, Mectizan (ivermectin), came into use after it was shown to kill the microfilaria and sterilize the adult worms for several months [66, 67].

A concerted effort to control the disease in West Africa was launched in 1974 by four United Nations agencies working in concert. This Onchocerciasis Control Program (OCP), which encompassed eleven countries, first relied on aerial insecticide spraying to destroy the blackfly vector. In 1981, Mectizan was employed with great effectiveness to control the microfilaria burden in affected populations, and to impede the fertility of the adult worms. It was donated to the OCP by Merck and Company which had developed the drug. Recurrent treatment with this monotherapy in endemic areas eventually eliminated much of the reservoir of microfilaria and rendered adult worms sterile for several months. The periodic treatment of those with living adult worms will be necessary for at least 15 years or so given their longevity [67, 68].

Evidence for Treponemal Diseases Being Depicted on Djenné-Jeno Terracotta Statues

Endemic treponemal diseases include yaws, endemic syphilis (bejel), and pinta. These three diseases are related to venereal syphilis, and are caused by spirochetes that are difficult to differentiate from the one that causes the latter disease. The current classification of these spirochetes indicates their close relationship to the cause of venereal syphilis, Treponema pallidum subsp. pallidum. The organisms for the other three are: yaws (Treponema pallidum subsp. pertenue), endemic syphilis (Treponema pallidum subsp. endemicum), and pinta (Treponema pallidum subsp. carateum) [69].

The origins of the treponematoses have undergone considerable re-evaluation in recent years based on archaeological, historical, and advanced phylogenetic research. Essentially, there are three hypotheses, the Columbian hypothesis, the pre-Columbian hypothesis, and the Unitarian hypothesis. The first, which is perhaps the best known, holds that syphilis originated in North America, and was imported into Europe by Columbus and his crew following the voyage of 1492 [70]. The pre-Columbian hypothesis holds that syphilis existed in the Old World before 1493, but that it was incorrectly diagnosed as other illnesses such as leprosy [71]. The Unitarian hypothesis is based on the belief that all venereal and non-venereal treponematoses are caused by the same organism. It further postulates that the various clinical signs of the four diseases are due to climatic conditions and social determinants in given geographic areas [72].

With reference to the Djenné-Jeno statues, pinta is not a consideration given that its historical presence has been limited to Mexico, Central and South America, and the Caribbean. Discussion here is therefore limited to yaws, bejel (endemic syphilis), and venereal syphilis. All three diseases are primarily transmitted through direct contact.

Yaws

The causative agent of yaws, now known as T. pallidum subsp. pertenue, was first discovered by the eminent Italian bacteriologist, pathologist, and tropical disease specialist, Aldo Castellani, in Ceylon (Sri Lanka) in 1905 [74,75,76]. Previous to this discovery, he had served in 1902–1903 with the British Commission on Sleeping Sickness in Uganda. He discovered flagellated parasites in the spinal fluid of patients, and named them Trypanosoma ugandense. Later, the name of the causative agent of sleeping sickness (trypanomiasis) was changed to Trypanosoma gambiense. In subsequent years, different trypanosomal strains were elucidated. However, to Castellani goes the credit for discovering the protozoan that is the cause of this serious disease [77].

Cecil John Hackett was a leading authority on yaws who, during his long career in tropical medicine, served as Director of the Wellcome Museum of Medical Science in London, and later as Senior Medical Officer, Research Planning and Coordination, with the World Health Organization. He supported the hypothesis that yaws arose in the Afro-Asian land mass from mutants of the pinta genome around 10,000 B.C. He also postulated that endemic syphilis (bejel) arose from yaws about 7000 B.C. with the development of arid climates following the last period of glaciation. He supported the view that venereal syphilis arose from endemic syphilis around 3000 B.C. in southwestern Asia. Later, it spread to Europe around 100 B.C., where he believed it was a mild disease until a mutation occurred at the end of the fifteenth century A.D. [78].

Clinical yaws is a three-stage disease beginning with a non-tender papule called a "mother yaw." Following healing of the initial lesion, secondary papules appear on various parts of the body, including the palms of the hands and soles of the feet. Eventually, these lesions heal. However, in about 10–20 percent of cases, a third stage occurs within several years in which destructive lesions occur in the bones and skin. A single dose of penicillin cures the disease, as does treatment with erythromycin, tetracycline, or doxycycline in those allergic to penicillin [79, 80].

Yaws frequently affects children who manifest the lesions of its secondary stage. The disease has only been found in hot humid climate zones of tropical areas of the world. An unanswered ecological question is whether or not the region of the IDN was a more humid zone during the centuries when the terracotta statues were created. A related question is whether or not yaws was at that time strictly limited to hot humid environments. There are no easy answers to these important questions.

In recent years, few to no cases of yaws have been reported from the regions of Mali in which the IDN is located [81]. This area is now in the Sahel, and characterized by a hot and dry climate where yaws is generally not found.

Endemic Syphilis (Bejel)

Endemic syphilis is a non-venereal disease that usually occurs in children between 2 and 15 years of age in arid regions. It is generally contracted from contact with infected skin and mucosal membranes, and contaminated fomites. The initial lesion is often not apparent, but the secondary ones are. They include maculopapular lesions similar to those seen in the same stage of venereal syphilis. The tertiary phase is similar to that of yaws in causing damage to the bones, heart, skin, and brain [82].

Endemic syphilis is found in hot dry climate zones including the Sahel of West Africa, Saudi Arabia, Iraq, Iran, Turkey, and other countries. The name bejel is derived from the Arabic bajal, meaning uncountable. It was long believed that endemic syphilis and yaws were never present in the same geographic areas. However, in 1961, Cockburn reported that both diseases were simultaneously found in the southern Sudan (now South Sudan) [83].

Given that the secondary stages of both yaws and endemic syphilis occur in children, it would seem unlikely that they would be depicted on the surfaces of terracotta statues that otherwise seem to represent adults. However, the secondary stage of venereal syphilis also, like endemic syphilis, provides florid skin lesions consisting of macules and papules. This disease is found in the Sahel at present where its prevalence is quite high [81]. Whether or not it was present in the region at the time the terracotta statues were made is an open question.

Discussion

The Djenné-Jeno terracotta statues were created over several hundred years between 1100 A.D. and 1700 A.D. Surface excrescences on the surfaces of some of these statues have challenged interpretation for many years (Fig. 12).

Fig. 12
figure 12

(Private Collection. Reproduced with permission of Bernard de Grunne)

Djenné-Jeno terracotta figure depicting relatively few dermatologic excrescences. They probably represent smallpox because of their predominantly centrifugal location. Height: 10 in. 1200–1400 A.D.

Full size image

In this communication, I have approached this challenge through an analysis that combines medical and epidemiological evidence. In so doing, I have attempted to determine the possible diseases or non-disease human interventions that might have given rise to these dermatologic alterations. The configuration and anatomical placement of excrescences on some statues persuade that they reflect beautification efforts. These could have been created in real life, as shown in Fig. 1, by the technique of cicatrization of the epidermis, resulting in keloid scar formation.

The process of clinical and epidemiological reasoning has led to the consideration of several diseases. Together, these comprise a differential diagnosis of possibilities. These diseases include smallpox, measles, molluscum contagiosum, onchocerciasis, yaws, secondary endemic syphilis, secondary venereal syphilis, leprosy, urticaria, and chickenpox [84].

While secondary yaws appears to be a possibility, clinical and epidemiological evidence tends to rule it out as a diagnosis. The reasons are that it is a pediatric illness that would not likely have been memorialized on statues depicting adults. In addition, it probably was not endemic in the IDN centuries ago nor is it at present. There is also no geo-historical evidence that the current hot and dry Sahelian climate of this region was hot and humid at the time these statues were created.

The secondary stage of endemic syphilis is found in this region, and has no doubt been there for many centuries. However, like secondary yaws, it is a pediatric disease not usually present in adults. These considerations relevant to yaws and endemic syphilis would tend to remove them from depiction on the surfaces of terracotta statues of adults.

Although chickenpox is a consideration, it is a fairly benign childhood illness. Likewise, urticaria are usually benign and generally of short duration. On the basis of these observations, they can be eliminated from diagnostic consideration. Leprosy needs to be considered given its dermatologic manifestations and chronicity. Untreated, the disease leads to significant deformities of the face and extremities. None of these latter medical signs are simultaneously depicted on statues with surface excrescences.

The secondary stage of venereal syphilis, with its dramatic dermatologic rash of highly infective macules and papules, requires diagnostic consideration. However, questions remain about the presence of venereal syphilis in West Africa prior to the fifteenth century when a number of these statues were created. If it were present in West Africa earlier than the fifteenth century, then it would have to receive serious consideration in the differential diagnosis.

This leaves two important possibilities in the provisional diagnosis. Onchocerciasis must be seriously considered because while the adult worms create discrete nodules of varying sizes, the microfilia infiltrate the skin where they produce pruritic papular and macular eruptions.

Smallpox ranks very high in the differential diagnosis given several clinical and epidemiological lines of evidence. The disease caused a prominent five-stage rash that lasted for about three weeks before the eschars fell off, leaving behind both temporary vitiligo and then pitted scars. The Variola major form of smallpox carried a mortality of from 20 to 50 percent.

These terrifying clinical characteristics of smallpox were in addition to its epidemiologic pattern as both an endemic and epidemic disease. Thus, a disease with a high morbidity and mortality and known to appear in devastating epidemics would seem to have merited memorialization on the terracotta statues.

The anatomical distribution, size, and form of excrescences on a number of statues reflect the rash of smallpox. A few statues actually depict the indentation or umbilication in the center of smallpox vesicles which was commonly seen when the disease existed (Fig. 13).

Fig. 13
figure 13

(Daniel Shapiro Collection. Reproduced with permission of Bernard de Grunne)

Two Djenné-Jeno terracotta figures on which umbilication of smallpox vesicles is shown as holes in the centers of the lesions. Height: 16 in. 1220–1460 A.D.

Full size image

Dr. Donald Ainsle Henderson, who headed the successful 10-year World Health Organization effort to eradicate smallpox, examined photographs of the terracotta statues shown in Figs. 9 and 12. His excited response was: "I was stunned as I looked at the pictures of the Djenné-Jeno terracotta statues. There is no question. That is smallpox, obviously done by someone who was perceptive about the pox distribution and umbilication" [85].

The existence of smallpox in West Africa and in the IDN during the millennium when the statues were made provides historical evidence that those who made them were familiar with the disease. This is an important piece of persuasive evidence that the lesions depicted on these statues are indeed smallpox.

Conclusions

In this study, clinical, diagnostic, and epidemiological methodologies have been applied to arrive at a possible definitive diagnosis of the excrescences depicted on Djenné-Jeno terracotta statues made between 1100 A.D. and 1700 A.D. While it has not been possible to arrive at a single definitive diagnosis, examination of all the evidence has permitted consideration of several provisional diagnoses. These include smallpox, onchocerciasis, the secondary stage of venereal syphilis, and intentional cicatrization to create keloids in order to achieve beautification. Although it is beyond the scope of this inquiry, it would be of great interest to know of the cultural contexts of these statues, which clearly occupied an important place in the lives of those who created them.