An ethnobotanical study of medicinal plants in Sheka Zone of Southern Nations Nationalities and Peoples Regional State, Ethiopia

Summary of statistical test of significance on the average number of medicinal plants cited among different informant groups in Sheka Zone is indicated in Table 5. The results of the analysis shows knowledge differences among different informant groups based on the specified parameters as indicated in the table.

The vast majority of the medicinal plants 141 (53%) collected from the study area belonged to herbaceous species. They account for more than 50% of the total medicinal plants. They were major reservoirs of medicines for local people of Sheka Zone. High usage of herbs as sources of herbal remedies might attribute to their relative abundance and ease of accessibility to healers. Study conducted by [32, 39] in southwestern Ethiopia reported that high usage of herbaceous medicinal plants was attributed to their relative abundance as compared to other plant growth forms and history of settlement the people using it. Moreover, the patterns of growth could also contribute the high frequency of usage of herbaceous plant species due to the fact that herbs are the dominant plant growth forms in the Ethiopian flora.

Large numbers of medicinal plants in the study area were also found to be used to treat only human health problems and only few of them were reported to be used to treat livestock ailments. The possible reasons could be attributed to the relative preference to and emphasis of the people on human health problems as compared to livestock health problems. Moreover, relatively larger number of medicinal plants were used for treating both human and livestock ailments. Availability of veterinary clinics could also be a factor as reported by [39] because people prefer modern healthcare services for their livestock in the presence of such services in their vicinity.

The study indicated that the most frequently used plant parts are leaves (66.93%) and roots (24.81%). It agrees with other ethnomedicinal studies in Ethiopia that showed leaves as the most frequently used plant parts [13, 14, 27, 28, 30, 33] followed by roots [12, 32, 34]. Some plant parts particularly the root, leaf, and bark are sensitive to harvesting so that affecting them could directly or indirectly affect the life of the whole plant. This is due to the fact that these plant parts play vital role in the whole life cycle of the plant species under question. Rare species for instance may be susceptible to local extinction due to over usage and pressure posed on its sensitive organs if care is not taken. Typical example is the case of Echinops kebericho whose root was highly marketable in local markets of Sheka Zone. It is obvious that uprooting the species could kill the individual plant leading to reducing its availability in its natural populations. Studies elsewhere in Ethiopia also indicated that over usage is a threat posing pressure on plant species in general and medicinal plants in particular [37]. Medicinal plant parts used could also serve as target organs for further medicinal plant profiling, promoting, and drug development.

In the current study, greater than 60% of the medicinal plant preparations were fresh plant material (Additional file 2). Similar finding was reported by [14, 27‐30, 33] that the fresh plant material is the most commonly used condition of preparation. Traditional healers claim that some medicinal plants lose their healing potential if not used in fresh condition. The implication was that there was limited practice of dry storage for future use. It means that there could be increasing frequency of harvesting which may affect the medicinal plant in use or its parts. Similar studies also confirmed that freshly harvested medicinal plant parts were frequently used in the preparation of plant derived remedies [39, 40].

According to the current study, the majority of the routes of administrations of the medicinal plants were internal through oral intake. However, there is no guarantee about the side effects of such type of medicinal plant intake. There may be high chance of health complications to arise creating both short term and long term problems on the life of the patient. Giday [39], for instance, reported that relatively less risk of being poisoned by improper use of herbal remedies was external/skin application as compared to internal/oral applications. The implication was the presence of problems of dosage, standardization, side effects, validity, and the susceptibility of delicate body parts of the patient above all. Hence, there is a need to give priority attention to the establishment of standardized traditional treatment guidelines for medicinal plants by well-known traditional healers. Ethnomedicinal studies such as [14, 29, 35, 40, 41] reported that oral administration is the most commonly used route followed by external/skin creaming.

Traditionally, healers use different methods as means of dosage determination. Among these were finger strips of little finger, finger nails of little finger, glass, coffee cup, and teaspoon based on the age and sex of the patient. This study is in line with the reports of [29, 42] that dosage varies according to age, sex, and physical condition of patients. Moreover, they use different preparations (mixed plant extracts), milk, honey, meat soup, bread of red teff as antidote against the side effects. However, there is a high chance of the patient to be victim of the side effects of the medicinal plant in use and it is obvious that the scenario is even true in modern medical care services if great care is not taken. For that matter, the Food, Medicine, and Health Care Administration and Control Authority (EFMHACA) of Ethiopia, for instance, has already established standard treatment guidelines at various levels of health facilities (health centers, primary hospitals, and general hospitals) [24] for multi-stage treatment services. Yet the traditional treatment practices have a number of gaps in it despite its vital role in primary healthcare services.

For the current study, strong agreement among informants (greater than 50%) was observed for 16 of the 22 human health problems. The informant consensus factor (ICF) value for epilepsy was only 25% for the current study. Informant consensus values normally range between 0 and 1 [43]. High informant consensus factor values were observed for treating both human and livestock ailments in the study area. The implication was that only few medicinal plant species were reportedly used by very high proportion of informants to threat a given category of health problems. That means there was strong agreement among informants over which medicinal plant to use a in the traditional treatment of a given health problem. Low ICF values show informants’ disagreement over which medicinal plant species to use for treating a given category of health problem. It was stated that ICF is used to identify plants of particular intercultural relevance [43]. Hence, it would be necessary to group health problems into wide diseases categories.

The ICF values for the 22 major human diseases categories range in between 0.25 and 0.96 with average value of 0.62 as indicated in Table 2 of the results section. Since the values of informant consensus factor normally ranges between 0.00 at its lowest and 1.00 at its highest [23, 43], it implies that there is strong agreement among informants (> 50%) for the 16 of the health problems. High informant consensus factor values imply strong agreement of informants on which medicinal plant to use to cure specific type of aliment. Low informant consensus factor values on the other hand imply strong disagreement of informants on which medicinal plant to use to cure specific diseases. It means that if ICF value is high, few medicinal plants species are reported to be used by high number of informants to threat a particular category of health problem and vice versa. Hence, more than 90% of informant consensus factor was obtained for skin diseases (96%), poisoning/snake, insect bite (94%), and gastrointestinal (92%).

Parasitic infections such as scabies, pediculosis, and onchocerciasis were the commonest health complaints followed by bacterial and fungal infections in southwestern Ethiopia [44]. However, care should be taken while using such outdated literature sources and up-to-date research findings about the current status of various health problems should be referred. Onchocerciasis, for instance, was almost under control in Ethiopia and no significant case reports are available in the current situation. Recent research findings show that more than 40% of tropical health problems including malaria were caused by gastrointestinal parasites in developing countries [45, 46]. In Ethiopia, common helminthic infections for which traditional remedies were highly prescribed include tapeworm, ascariasis, hookworm, and pinworms [47]. A study conducted around Tepi Town of Sheka Zone also revealed that Ascariasis and Trichuris trichiura were the most common helminthes in the area [48].

The fidelity level of medicinal plants represents the relative healing potential of medicinal plants against a given ailment. In the current study, the relative healing potential or fidelity level (FL) of most sited medicinal plants with relatively higher fidelity level values for treating human, livestock, as well as both human and livestock aliments were identified and discussed. Relatively high fidelity levels were observed for medicinal plants the medicinal plant species have relatively high healing potential against the respective health problems mentioned. In other words, plants with high FL values could be target species prioritized for conservation, management, and sustainable use after their bioactivities were properly evaluated and confirmed. They could also contribute to medicinal plant data base. It was reported that lower fidelity level indicates a given medicinal plant species could have more number of mentions by the informants than medicinal plant species that have high fidelity level [43].

Considerable number of medicinal plants in Sheka Zone need further chemical profiling to assure their validity and efficacy. According to Heinrich [21], he noted that systematic evaluation of indigenous therapeutic methods and practices so as to improve healthcare in marginalized regions became an important element of the agenda of international and national organizations. Validation of therapeutic claims helps to increase confidence and generate income creating opportunity for marketing of herbal medicine [49].

The relative importance of a given medicinal plant within a culture in which it is found to be significant is evaluated through the application of quantitative ethnobotanical methods and data comparisons among diverse cultural groups within a given fragment of social groups or community. Quantitative ethnobotanical methods and approaches such as the use of informant consensus factor, relative healing potential, relative cultural importance, cultural significance index, ranking, and scoring are among the indices used in the systematic evaluation of the medicinal plant in need. Moreover, use variability of medicinal plants of interest in search of their bioactive compounds can be estimated by using the informant consensus factor (ICF) values. Hence, plants with the greatest bioactivity are considered to have the highest ICF values and are better candidates for bioprospecting and further profiling [50, 51]. Hence, the considerable number of medicinal plants recorded from Sheka Zone need further profiling to assure their validity and efficacy. As reported by [12], validation of bioactivity of medicinal plants preferred by traditional healers increase their acceptance both nationally and internationally for healthcare systems. Moreover, the findings of [27, 32] summarized that priority for further pharmacological studies must be given to medicinal plants scoring the highest fidelity level.

The etic/emic approach helps to visualize the way local people try to perceive their surroundings thereby seeking solutions to major practical problems in health, food security, social integrity, and environmental sustainability. Modern science has much to learn from traditional practices as the traditional practice has to learn a lot from modern science in all aspects of life related to the issues outlined above. For instance, it is a known fact that long before the discovery of modern healthcare systems and drugs, ancient people traditionally used to get self-medication by trial and error. Such traditional therapy was what traditional healers of today still engaging in, although the way they are doing it is closer to modernity. Hence, knowledge integration becomes among important aspects for the success of science. Social beliefs and taboos associated with diseases or any health problems and the associated herbal remedies used to treat such diseases have something to do with the mutual relationships between traditional healthcare system and modern healthcare services. However, relying on traditional healthcare system has yet its own advantages and disadvantages.

On the one hand, traditional healthcare system is believed to be very cost effective, easily accessible, and highly trusted by the patients who get the services if it is carefully performed by well experienced traditional healers. Just as a medical doctor treats his/her patients psychologically well in addition to other medical services, both the traditional healers and the patients in Sheka who are going to get traditional medication have a common belief that God has created the natural medicine, the herbs, and shared his medical knowledge to the authorized person, the traditional healer, so that they confidentially visit the herbalist in their locality to get medication. The healers also believe that God does not refuse them to care for their patients when they give the medicine on behalf of him. Such well-gifted people in Sheka are usually nominated as clan leaders and have specially recognized places in all social aspects in the culture and believe of the Sheka people. They even participate in governance, conflict resolution, and related issues in their society.

On the other hand, there is no evidence about the dosage determination, route of administration of medicinal plants, and the associated short term as well as long term side effects, although traditional healers in Sheka are well-adopted in treating patients. Hence, the issues of validity, standardization, and side effects are questionable so that there is a risk of committing life-threatening events. Even it is well obvious that in well-tested and confirmed modern medical services, there are events where life-threatening cases may occur. These events are related to dosage, patient’s health history, improper prescription of medicines, and related mistakes during multistage treatment options.

The Food, Medicine, and Health Care Administration and Control Authority of Ethiopia for instance prepared standard treatment guidelines for health institutions at various levels [24] which can serve as a standard reference for health professionals. EFMHACA further noted that irrational use of drugs has been one of the major problems in the Ethiopian healthcare system for a long time. It was emphasized that medicines should only be prescribed when necessary, and the benefit-risk ratio of administering the medicine should always be considered prior to prescribing where the prescription should be through the well understanding between the prescriber, the pharmacist, and the patient [24, 25, 52]. The above scenario calls for the need for integrating traditional healthcare system with modern medical services thereby validating, standardizing, and certifying traditional medication and the knowledgeable persons who are giving the service to the society.

From the total of 414 informants, highest numbers of informants (380) were males, whereas only few of them (34) were females due to cultural preseasons. Obviously, ethnobotanical field work is affected by various factors such as cultural background of the society, field situations, willingness of informants, and related sociocultural limitations. Hence, less number of female informants as compared to male informants was interviewed during the current study. A study conducted in Burkina Faso, for instance, showed that it was impossible to interview equal number of men and women due to the traditional rules governing many societies [52]. Age wise, the age range for the entire study was 18 years to 96 years of age. On average, more medicinal plants were reported by male informants (5.542 ± 3.725) than female informants (4.765 ± 1.986) with significance difference (p = 0.0465); elders of age > 30 years (5.832 ± 0.213) than youngers of age 18–30 years (4.149 ± 0.218) with significant difference (p = 0.00001); illiterate informants (6.295 ± 0.211) than literate informants (4.341 ± 0.287) with significant difference (p = 0.00001); key informants (13.367 ± 1.426) than general informants (4.862 ± 0.105) with significant difference (p = 0.00001). This study agrees with [31, 53] that older people cited more medicinal plant species than younger people. Moreover, it is in line with [28, 31] that reported illiterate people and key informants are more knowledgeable about medicinal plants as compared to literate people and general informants (Table 5).

High ranking medicinal plant species are priority species for further profiling against gastrointestinal problem efficacy and safety. Quantitative analytical tools such as ranking and scoring are among the quantitative ethnobotanical approaches used to generate scientifically rigorous results [1, 3]. The authors further noted that pairwise matrix of medicinal plants in relation to a given aliment selected based on the results of ranking and scoring is used to test for the consistency of the relationships of preferences as well as transitivity of results.

Furthermore, pairwise comparison of top five medicinal plants against gastrointestinal problems as obtained from the ten respondents (R₁ through R₁₀) also show that Croton macrostachyus Del. ranked first followed by Prunus africana (Hook.f.) Kalkm. Peperomia retusa (L.f.) A. Dietr, Lobelia giberroa Hamsl, and Celosia schweinfurthiana Schinz respectively in this order confirming consistency of relationships and transitivity of results. It implies that the above plant species were found to be culturally important in the study area due to their wide use by a large number of users of the plants due to their curative properties.

Harvesting impacts on multipurpose plant species can be tested by ranking and scoring [1, 5]. It is obvious that there are instances where the most utilized species is going to be most threatened one in its locality if appropriate conservation, management, and sustainable use measures are not taken. This is clear from the point of view of whether the rate at which the species is utilized in the area is much greater than the rate at which it is replacing itself or not in its natural habitats [54]. The worst problem arises when such events are so latent that even it is going to be difficult to take immediate conservation measures to save the rare species. Even species which are not multipurpose but known for their single use value such as medicinal purpose may be at risk of extinction under such circumstances. For instance, medicinal plant species such as Echinops kebericho and Vangueria madagascariensis were found to be highly wanted species in Sheka Zone for their high medicinal value but they were found to be very rare in their occurrences and distributions in the area and hence they are typical examples.

The route of administration and dosage of medicinal plant plants is usually based on haphazard applications except for few well experienced and knowledgeable traditional healers. Even well-qualified healers are not perfect. The implication of such scenario is that improper use of the medicinal plants can have both short term and long term serious impacts on the health of the patient and sometimes life threatening.

There are relatively high ranking medicinal plants of higher fidelity level in Sheka Zone. They are used to treat humans (204 species), livestock (ten species), and both humans and livestock (52 species) health problems. These high ranking medicinal plants are candidates for further phytochemical profiling in drug research and development.

Medicinal plants with relatively highest use values are considered to be the most used ones. They are considered being under pressure due to over usage which may in the long run can lead to the rarity of the species. Such species need conservation priorities. It was noted that high use diversity index commonly interpreted as the pressure on a given resource arising from use [23]. Therefore, the current study showed that high ranking medicinal plants based on their use diversity values (Table 6) need priority attention for conservation. Hence, there is also a need to establish the direct relationship between the use values of medicinal plants and the actual impact on them arising from harvesting.