Distribution of local healers in the study area

Information on a total of 352 local healers was collected through our survey, which was distributed across 103 villages in nine townships in Gongcheng (Fig. 2). According to the statistics at the township level, Limu had the largest population of 54 local healers, followed by Sanjiang (48), Guanyin (47), and Xiling (45). Forty-three local healers were in Jiahui, 35 in Lianhua, 35 in Gongcheng, 23 in Ping'an, and 22 in Longhu (Table 1). The value of per capita healers (Pch) was calculated, and the highest value was noted in Guanyin (4.90‰), followed by Sanjiang (3.33‰), Longhu (2.10‰), Jiahui (1.63‰), Limu (1.23‰), and Xiling (1.16‰), and the lowest values were in Gongcheng, Lianhua, and Ping'an, at around 0.60‰ (Table 1, Fig. 3). At the village level, the Shuibin village in Guanyin township has the most local healers with 24 people, followed by Shitang village in Guanyin township with 16 people and Sanlian village in Sanjiang township with 11 people. There are near 30 villages with just only one or two local healers from Gongcheng, Lianhua, and Ping'an townships.

Table 1 The number of local healers in townships within Gongcheng

From the data, we found that the Gongcheng, Lianhua, and Ping'an townships had relatively low Pch, at about 0.60‰. Because the Gongcheng township is the seat of the county government, and the Lianhua and Ping'an townships are close to the Gongcheng township, these three townships have undergone the highest degree of urbanization, modern construction and economic development in recent years and are more influenced by modern Chinese and Western medicine. Hence, the number of local healers in these townships today is lower. The Guanyin and Sanjiang townships now have the highest distribution of Pch, reaching 4.90‰ and 3.33‰, respectively. These two townships are typical minority nationality townships, with the population of Yao nationality accounting for more than 90%. These results indicate that these areas with a denser population of Yao nationality had greater preservation of local healers and medicinal knowledge and must as key areas for the protection inheritance of traditional medicinal knowledge. In addition, the Guanyin township is located in the extreme north of Gongcheng and the Du Pangling Mountains. The Sanjiang township is located in southeastern Gongcheng and south of the Yindian mountains. These two townships are located in remote mountainous areas, are populated with many Yao people, and have a relatively low degree of economic development. With continuing urbanization and economic development, the succession and inheritance of local healers and traditional knowledge have been disregarded in recent years. Therefore, the protection and inheritance of traditional knowledge should be strengthened as quickly as possible, especially in Guanyin and Sanjiang townships.

Demographics of the informants

Among the 352 local healers in the study area, 279 (79.26%) were male, and 73 (20.74%) were female. This is owing to the conservative inheritance of Yao medicinal knowledge, and the custom of passing knowledge on to male members, rather than female members of the society; a matter which is also related to the fact that women are predominantly engaged in housework and agricultural work, while men are mostly engaged in physical and technical labor. Concerning age, the oldest healer was a 101-year-old man from Changjia village in Limu township, who had been a healer for more than 60 years. The youngest was a woman aged 28 years, a healer for nearly 5 years. The ages were mostly between 40 and 79 years (n = 308), while only 23 healers were 28–39 years old, and only 21 were 80–101 years old. Notably, the number of young healers was very low (Fig. 4). Of all healers, those aged 60–69 years were the highest number (27.56%), followed by those aged 70–79 years (24.15%). We counted the number of healer who begin to learn medical knowledge in each age group and found that 20–29 age group was the most (n = 138), followed by 30–39 age group (n = 93) and 40–49 age group (n = 59) (Fig. 4). The number of people in the 20–39 age group is 231 (65.63%), which shows that most healers in Gongcheng begin to learn medical knowledge from the young age. In contrast, the current statistics about healers of all age groups show that young healers are in the minority. Therefore, more than half of the local healers were exceeding 60 years, and the lack of succession and inheritance of Yao medicine is evident. One reason for this phenomenon is that the manner of succession is quite conservative, in that passing on knowledge to external sources and female members are generally restricted. Furthermore, there is no written language of the Yao ethnic group, so the inheritance depends on oral transmission, and unfortunately, the great traditional knowledge has not been passed down by written records. Moreover, young people are resistant to learning traditional knowledge, as they feel it is outdated, useless, and a source of only meager income. They are more willing to travel great distances for work that will give them a higher income or learn Chinese medicine and Western medicine, which are generally more acceptable to the public. This phenomenon also occurs in other areas, with some facing the serious threat of losing their inherited traditions [7, 8, 14, 34, 35].

Fig. 4

a The number of healer in each age group in Gongcheng; b The number of healer who begin to learn medical knowledge in each age group in Gongcheng

Most of the famous and old healers in this survey are excellent representatives of local Yao healers in Gongcheng. Over their lifetimes, they continually accumulated practical experience from their therapeutic activities and also absorbed the experience of predecessors. This precious wealth of Yao medicine plays an important role in inheritance, innovation, and development. Furthermore, it is because of the accumulation and inheritance of the experience of Yao medicine from past generations that Yao medicine has developed and remained relevant in modern times. Therefore, these practices should be actively encouraged, and in-depth investigations and excavations should be implemented to avoid the decline in successors and loss of precious traditional experience.

Diseases treated in the study area

After sorting and statistical analysis, 352 local healers demonstrated a good history of treating diseases, which could be classified into 12 categories based on the eight systems of the human body and the medication characteristics of the Yao people. Gongcheng had the largest number of healers (176, 50%) who were successful in treating traumatic injury and orthopedics, followed by digestive system disease (101, 28.69%), skin and facial disease (93, 26.42%), and rheumatic disease (91, 25.85%) (Table 2).

Table 2 The types of diseases treated by local healers

Traumatic injury and orthopedics were the most common diseases that local healers effectively treated; these were related to local people being engaged in agricultural and forestry production; this type of labor commonly results in mechanical injuries, knife wounds, and fractures. Rheumatism, hyperostosis, traumatic injury, lithiasis, skin diseases, gynecological disorders, pediatrics, snake bites, orthopedics, and liver disease were commonly mentioned in the survey. According to the results, more than 30 local healers effectively treated these common diseases effectively, especially rheumatism and hyperostosis, which were resolved by more than 70 local healers. As these diseases are common, local healers must treat them timely, convenient, and efficiently to improve outcomes.

The public has recognized the unique curative effect of Yao medicine through the historical accumulation of experience with such diseases. Gynecological and pediatric diseases are common in the daily lives of the Yao. The various gynecological drugs commonly used include Campsis grandiflora, Hedyotis caudatifolia,　Nuphar pumila, Saururus chinensis, and Dichroa febrifuga. Furthermore, pediatric drugs including Primulina fimbrisepala, Ilex rotunda, Siphonostegia chinensis, Polygala polifolia, and Striga asiatica are potent and convenient for Yao healers who prefer to use fresh herbs as materials.

Disease incidence is often closely related to the local environment and climate, as well as ethnic activities and lifestyles. According to the survey, Gongcheng had the largest number of healers who could effectively treat rheumatic disease because Gongcheng is located in the south of the Nanling Mountains, where the high mountains, dense forests, high temperature, rainy weather, wind, cold, and damp heat are conducive to the development of rheumatism. Moreover, the ancestors of the Yao people frequently migrated to higher elevations with dense forests in the mountains. Life in these mountainous regions is tough, and traumatic injuries, snake bites, and insect bites are frequent occurrences; in addition, skin diseases and orthopedic diseases such as fractures, lumbocrural pain, and muscle or bone pain are locally common. Thus, the local healers' ability to treat such diseases has increased. Similar results have also been found in other minority areas in southern China [7, 8, 36, 37].

Informant consensus factor

The ICF was calculated for each disease category, ranging from 0.44 to 0.80 (Table 3). The highest ICF (0.80) was reported for digestive system disease with 20 species and 98 use reports, followed by urinary system disease (0.78) with 9 species and 37 use reports, nervous system disease (0.77) with 8 species and 32 use reports, skin and facial disease (0.75) with 19 species and 74 use reports, and pediatric (0.75) with 9 species and 33 use reports, etc.

Table 3 Informant consensus factor (ICF) by categories of diseases in the study area

The higher the ICF value, the higher the diversity of plant species used by healers to treat a particular disease category. The lower the ICF value, the more concentrated the plant species used by healers to treat a particular disease category [32]. Most disease categories had a high ICF value (near 1). The digestive system disease had the highest ICF value; this was probably related to the local healers obtaining a diversity of medicinal plants from wild habitats, while having little communication with other healers, during the conservative inheritance of medicinal knowledge. There were 110 plant species used to treat traumatic injury and orthopedic diseases, and this was likely related to the local people being prone to traumatic injury, hyperostosis, knife wound and fracture when engaged in agricultural and forestry production. Therefore, the healers were required to use a variety of plants for treatment when dealing with these emergencies. The lowest ICF was for circulatory and rheumatic disease, which was probably related to the long treatment cycle of these diseases. During long-term treatments, local healers had a high consensus on the species of medicinal plants used.

Methods of treatment and ethnic characteristics

In all, 248 prescriptions were collected through interviews with local healers; their methods of treatment mainly included nine types: decoction (114, 45.97%); external application (50, 20.16%); medicinal liquor (26, 10.48%); stewing with meat (17, 6.85%); soaking (17, 6.85%); external washing (16, 6.45%); acupuncture and moxibustion cupping (4, 1.61%); plaster (3, 1.21%); and cream (1, 0.40%) (Fig. 5). There are several methods of external application, including fresh herbs directly smashed for external application; dry herbs ground into a powder to spread on the affected area; or herbs mixed with tea oil, tung oil, vinegar, or secondary rice water for external application. Medicinal liquor has always been a preferred method by local healers, and many also prefer to use their secret recipes; medicinal liquor is easy to prepare, and its ingredients can be more effective in this form. It also has antiseptic and antitoxic effects, which can delay hydrolysis and enhance the stability of many drugs. During our investigation, we also found that some Yao medicine methods were more distinctive, for example, stewing herbs with pig tripe, pig feet, pig bones, snails, frogs, or fish.

Fig. 5

Treatment methods used by local healers in Gongcheng

Local healers believe that when fresh herbs are directly used for general decoction or external washing without being specially processed, their medicinal power is fierce and toxic side effects may occur, especially in the use of Dayao (a type of traditional medicine defined by local Yao people). When herbs are mixed with meat, bone, or other compatible stews, their power is lessened, and the toxicity of some fresh herbs can be reduced after prolonged decoction. The decoction is the most common method of herbal remedy preparation and is used widely by other ethnic groups [7, 8, 38,39,40,41,42,43]. In addition, a small number of local healers make plasters and creams, and some use moxibustion and cupping skills for treatment, but this is quite rare.

In the current study, the local healers used rosin, tung oil, or Huangdan and other auxiliary materials to make ointments such as rheumatic bone pain ointment, Wuliu ointment, and other commonly used ointments for the treatment of rheumatic bone pain, scalds, knife wounds, and other diseases. Furthermore, it is worth noting that local healers made Liaodiaozhu cream (a type of cream prepared mainly from the plant Cynanchum paniculatum), wherein the crystals precipitate from the freshly picked herbs after washing, kneading, and sealing in a bottle. This cream is widely popular for its effect, convenience, and ease of preservation in treating common diseases such as knife wounds and styes.

Diversity of medicinal plants used in the study area

In this investigation, 306 medicinal plant species were identified in 248 prescriptions of local healers in Gongcheng, belonging to 116 families and 255 genera. The results provided each species information, including scientific name, family, Chinese name, local name, habit, medicinal part, usage, and voucher specimen number (Table 4). The statistical analysis of families and species is shown in Table 5. At the family level, Asteraceae contained the most species (25 species), followed by the Fabaceae (17), Rubiaceae (12), Rutaceae (9), Rosaceae (8), Lamiaceae (8), Malvaceae (8), Polygonaceae (8), Vitaceae (7), and Primulaceae (6). Similar results have been shown in other areas of China, where many species belonged to these families [7, 27, 35, 36, 44,45,46]. These ten families accounted for 8.62% of the total number of families, but the number of species included accounted for 35.29% of the total number of species. Although there were many medicinal plants commonly used by local healers in different families, only a few families were highlighted. There were 49 families with 2–5 species, accounting for 42.24% of all families; the remaining 57 families contained only one species.

Table 4 Inventory of medicinal plants traditionally used by Yao people in GongchengTable 5 The diversity of medicinal plants used by local healers in Gongcheng

In general, the distribution of medicinal plant species in various families was relatively scattered, and the selection of medicinal plants by local healers was highly diverse, indicating that local healers were competent at using a variety of medicinal plants to treat various diseases. Hence, the mountains with ideal habitat and high biodiversity are called the "Yao mountains" (Fig. 1), and the Yao people have a traditional custom of collecting herbs from the "Yao mountains".

The medicinal plants observed in this study were classified into 152 species of herb (49.67%), 68 species of shrub (22.22%), 32 species of tree (10.46%), 29 species of the woody vine (9.48%), and 25 species of the herbaceous vine (8.17%) (Fig. 6). Herbs were most numerous and accounted for around half of the total species, because most herbs are easy to pick, cultivate and reproduce, and are convenient for use. These results are consistent with other research [44, 46,47,48,49]. In addition, the medicinal plants used by local healers fell into various life forms, which demonstrated that local healers had experimented with the use of an extensive range of plants over hundreds of years and had finally amassed the unique knowledge and experience of Yao medicine as we find it today.

Fig. 6

Life forms of medicinal plants in the study area

The efficacy of medicinal plants is closely related to the medicinal part used. Different medicinal parts of the same plant may have different efficacy, and the same medicinal part may have different efficacy in different prescriptions. There were 330 medicinal parts belonging to 306 medicinal plants in Gongcheng, which were treated as 330 medicinal species. Among them, whole plants were the greatest in number (125 species), accounting for 37.88% of the total species, followed by roots (20.30%), rhizomes (7.27%), stems (7.27%), root tubers (4.55%), leaves (4.24%), stem and leaves (4.24%), barks (including root-barks) (3.94%), fruits (including legume and rinds) (3.64%), seeds (2.12%), flowers (including inflorescence) (1.82%), and others (including bulbs, bulbils, corms, tuber, stem pith, and thorns) (2.73%) (Table 6). Among the 330 medicinal parts used by the local healers in Gongcheng, there were two main categories of whole plants and roots, in a total of 192 species, that accounted for 62.75% of the total species. Similar results have been found in some minority communities of Guangxi [7, 8, 27, 36, 50]. The local healers generally believe that roots are where the plant's medicinal powers converge, and their efficacy is optimal. Among whole plants, most are herbs, because herbs are easy to pick, and their habitats are diverse.

Table 6 Medicinal plant parts used by local healers in GongchengRelative frequency of citation

The RFC evaluates important plant species used by local healers to treat various diseases. From the 248 prescriptions investigated, the number of prescriptions mentioning plant species (FC) used ranged from one to 14. Calculations showed that 33 medicinal plant species had an FC > 5 (Table 7). The RFC value calculated for these 33 medicinal plant species ranged from 0.024 to 0.056. The higher RFC values included Kadsura longipedunculata, Schefflera heptaphylla, and Plantago asiatica.

Table 7 Relative frequency of citation (RFC) of plant species mentioned in prescriptions

The higher the RFC value, the more familiar was the local healers with the species; furthermore, and of great importance, the species were abundant and easy to obtain locally. Ten of these 33 medicinal plant species were traditional Laoban medicines, indicating that the local healers were good at using traditional Laoban medicines to treat diseases, especially Kadsura longipedunculata (the Laoban medicine name is xiao zuan) in the treatment of rheumatism. It also showed that local healers had a long history of using Laoban medicines, including Achyranthes aspera (the Laoban medicine name is niu xi feng) for the treatment of hyperostosis and rheumatic bone pain, Uncaria rhynchophylla (the Laoban medicine name is ying zhua feng) treatment for hyperostosis, lumbocrural pain, rheumatic bone pain, and others [26, 27]. These were all traditional and common usages in the local area.

Protect Yao traditional medicinal knowledge and medicinal plants

As for the protection of Gongcheng Yao traditional medicinal knowledge, the local government should provide a better environment for Yao healers, consider the legality of medical practice for Yao healers and give appropriate advertisements for those Yao healers. The local government also may pay more attention to the inheritance of Yao traditional medicinal knowledge and set up training course for young people. We firmly believe that the training of young personnel will strongly support the sustainable development of Yao medicine [35] and also is a very important approach for the conservation of Yao traditional medicinal knowledge.

Based on the demographic investigation, the Yao healers in Gongcheng aged over 60 more than half, some Yao healers are dying out, but their traditional medicinal knowledge was not be documented, so the further survey and record of Yao traditional medicinal knowledge is imperative [51], especially Sanjiang and Guanying townships in Gongcheng. Books and scientific reports about medicinal plants and Yao traditional medicinal knowledge should be published [8, 52].

In order to enhance the public understanding and confidence, as well as the safety of Yao traditional medicines, the advanced theories and methods of pharmacology, phytochemistry, and molecular pharmacognosy should be applied to study the Yao traditional medicines and traditional medicinal knowledge [8, 52]. And also in order to conserve local medicinal plant resources, the local government should encourage Yao people to plant preferred or rare medicinal plants in their farmlands [8, 35, 51, 52], which also in line with the strategy of rural revitalization.