In Ethiopia, there is a long history of using medicinal plants to treat a variety of diseases (Mesfin et al., 2014) and endowed with a variety of agro-ecological zones, attributing to existence of various plant species including many cultivated and wild plant, and cultural diversities and their associated indigenous knowledge. Similarly, according to  scholars  view,  Ethiopia  is  believed  to  be home for about 6,500 species of higher plants, with approximately 12% of these endemic (Mesfin et al., 2014).  Approximately 80% of humans and 90% of the livestock population in the country rely on traditional medicinal plants to cure different ailments (Dawit, 2001) due to difficulties in accessing modern health facilities, the  cultural  acceptability  of  healers,  and  low   cost   of traditional medicine (Nguta et al., 2010). Different scholars in their study described that, the greater concentrations of medicinal plants are found in the south and southwestern parts of the country following the concentration of biological and cultural diversity (Belayneh et al., 2012; Mesfin et al., 2014). Despite the use of traditional medicine over many centuries, relatively small numbers of tree and shrub species have been studied.

Beside the importance, Ethiopia’s traditional medicine as elsewhere in Africa is faced with problems of continuity and sustainability (Ensermu et al., 1992). Nowadays herbal practitioners have to walk greater distance for collection of herbal medicine that once grew in the vicinity of their homes.  Bizuneh et al. (2018) in their ethnobotanical study reported that, valuable indigenous knowledge associated with medicinal plants was under risk and need to be properly documented. Those studies so far conducted in medicinal plants also reported that, the existing medicinal plants were on conservation risk (Belachew and Behailu, 2018; Muluken et al., 2018).  Bizuneh et al. (2018) also stated that the problem is further compounded by the fact that traditional knowledge on traditional medicine is also being lost at an alarming rate.

Some findings also reflect potentially important information gaps and need for standardization of ethno-medicinal studies on indigenous medicinal plants in Ethiopia (Getachew et al., 2017). Additionally, According to Gonfa et al. (2015), Solomon et al. (2016) and Banchiamlak and Yound (2019), those medicinal plants available in the study region are becoming extinct and the associated knowledge held by elders has received less attention and hence, they are in the verge of disappearance. Additionally in the study area, medicinal plants are exposed to various destructive anthropogenic activities and this situation calls for integrated conservation measures. Furthermore, the rich ethnomedicinal knowledge held by the Sidama community at large and traditional medicine practitioners, in particular, needs an in-depth study and documentation (Nigatu et al., 2018).  In line with this, this study was conducted to document the knowledge of traditional healers on the use of medicinal plants against certain illnesses in human and livestock in Boricha district and to validate the traditional use and identify more bioactive secondary metabolites in support of its traditional uses.

Description of the study area

Boricha  district  is  located  in  Sidama Zone,  in  Southern  Nations Nationalities and Peoples Regions (SNNPR), at 311 km (Figure 1). Its geographical location extends from 6º46’N to 7º01'N and 38º04'E to 38 º24'E with an estimated area coverage of 588.05 km², administratively, the district comprise 39 villages. Based on the information from BoFED (2016) of SNNPR, BorichaWereda has an estimated total population of 255,514 of these 130,757 are men and 124,757 women. About 95.6 percent of the populations are estimated to be rural inhabitants (Southern Nation Nationalities and Peoples Regional State, Bureau of Finance and Economic Development, 2016).

Selection of informants, plant specimen collection and identification

Forty two traditional healers (37 male and 5 female) of different ages (30 to 80 years) were purposively selected as key informants with the help of local elders, agricultural office workers and administrative personnel of Boricha district. These traditional healers come from Sidama nation and the language of communication was Sidama or native to the study area. The data was collected in two rounds. The first round from December 01 to 17, 2018 and the second round from February 02 to 16, 2019.  Prior to the interview process, discussions were held with the informants through assistance of local elders to clarify the purpose of the study and build confidence of the respondents to provide reliable information without suspicion. Face-to-face meetings were held with traditional healers. A key informant interview guide was used to collect the data. These key informants were asked to provide information on plant(s) use against any kind of illness in humans and livestock, and the type of plant and the parts used, the methods of remedy preparation, the routes of administration, the dosage used and threats. The traditional healers were used as guides during field trips to collect voucher specimens. Voucher specimens were taxonomically identified by a botany specialist (Dr. MeseleNegash). A voucher specimen were labeled with scientific and vernacular names and deposited in a herbarium at Wondo Genet College of Forestry and Natural Resource, Hawassa University. 

Data collection and analysis

Based on the information obtained from the informants, the ailments reported were grouped and medicinal plant use variability was estimated. The level of homogeneity among information provided by different informants was calculated by the Informants’ Consensus Factor, ICF (Trotter and Logan, 1986) using the following formula:  

ICF = Nur – Nt / (Nur - 1)

Where, Nur = number of use reports from informants for a particular plant-use category; Nt = number of taxa or species that are used for that plant use category for all informants.  ICF Values range between 0 and 1, where ‘1’ indicates the highest level of informant consent. Descriptive statistics were used to analyze and summarize the ethnobotanical data.

ICF = Nur−Nt/ Nur−1

Ethical considerations

Participants gave their informed consent before commencing with the interview schedules as required by the University of Hawassa University ethics committee. Approval for the study was obtained from the Hawassa University, approval number: VPRTT/034/2016.

Diversity of species used

Forty two species distributed across 29 families and 35 genera were mentioned by traditional healers. These medicinal plant species are used to treat 17 ailments; 24 in humans, 6 in livestock and 12 in both human and livestock. The Lamiaceae were most presented with four species, followed by the Anacardiaceae, Boraginaceae, and Solanaceae families with three species each. Asteraceae, Cucurbitaceae, Cuppresaceae, Euphorbiaceae and Rutaceae each with two species and the rest representing one species. Whereas, Clutia abyssinica, Lactucainermis and Clerodendrum myricoides were the most frequently mentioned plant species, followed by  Lagenaria siceraria and   Stephania abyssinica. Shrubs constituted (45.24%) followed by trees (33.33%), herbs (16.67%) and climbers (4.76%) of the used species. Fifty nine percent of the medicinal plants were collected from the wild and the remaining ones from home gardens.

Informant consensus factor

Based on the used citations of the key informants, plants species were clustered into nine different categories (Table 1) to calculate the ICF values. The ICF values range between 0.81 (for lung infection and cough) and 0.98 (for gonorrhea and sexual transmitted disease). Thus, all clusters had an ICF value greater than 0.5 showing that all of them could be considered for validation in support of its traditional use

Informed consensus factor

ICF values were determined to know the agreement among the informants of Boricha area for use of plants to treat certain ailment categories. Eleven  plant species were reported to be used for treatment of febrile illness, sudden sickness and headache followed by skin, eye infection and ecto-parasite related (7 species); glandular swelling and cancer related problem (6 species), intestinal parasite, abdominal pain and stomach related problem (6 species); wound, body swelling and muscle contraction related illness (5 species); lung infection and cough (4 species);diarrhea and evil eye (3 species); gonorrhea and sexual transmitted disease (3 species) and jaundice (2 species). The ICF values are presented in the (Table 1) and it is clear that the ICF values varied from 0.81 up to 0.98. Gonorrhea and sexual transmitted disease has the highest ICF value 0.98 with 89 use-reports for 3 plant species. The species responsible for this high consensus was Clutia abyssinica, Lactuca inermis, and Clerodendrum myricoides with 89 of the 42 reported medicinal plants, followed by jaundice (ICF = 0.96; 33 use-reports, 2 species), intestinal parasite (ICF = 0.94; 91 use-reports, 4 species), glandular swelling and cancer (FIC= 0.93, 77 use reports, 6 species). Medicinal plants supposed to be efficient in treating particular ailment have high ICF values. The high ICF value for gonorrhea and sexual transmitted disease probably showed that this ailment is common in the study area due to lack of awareness in the region and there is a better communication established among informants for treating this ailment category. High ICF values also indicate that the species traditionally used to treat these ailments are more consensuses and believe than the others. The least agreement (ICF=0.81) between the informants was observed for plants used to cure lung infection and cough.

Ethno-medicinal plants, parts used, preparation and application

Informants claimed that shrubs and trees were commonly abundant and year-round, easy to obtain and withstand long dry seasons compared to other habits of plant groups. Consistent with this study, earlier reports (Mesfin et al., 2009; Kefyalew, 2015; Abiyot et al., 2018) indicated that shrubs and trees are found to be widely used plant habits as having remedies against certain ailments. Balcha (2014), Lulekal et al. (2014), Getachew (2016), Getachew et al. (2017), Nigatu et al. (2018) and Abiyot et al. (2018) reported that, the majority of the plant materials were harvested from wild sources for medicinal purposes. Similarly, this study  reports  that  most  of  the  medicinal plants were obtained from wild sources calling for the need to conserve them at botanical garden. The same idea was raised from earlier study by Ensermu et al. (1992) nowadays herbal practitioners have to walk greater distance for collection of herbal medicine that once grew in the vicinity of their homes Consistent with this study, (Figure 2A) large proportion of herbal preparations from leaves were reported (Tesfaye et al., 2009; Gonfa et al., 2015; Bizuneh et al., 2018; Abiyot et al., 2018; Nigatu et al., 2018 and Banchiamlak and Yound, 2019). This difference attributed to differences in the variations in the concentration of the active ingredients in botanical fractions as a result of climatic and edaphic factors reported on the proportion of root fractions (Lulekal et al., 2014; Melesse et al., 2015). Extensive use of root fractions may pool attention as uprooting may result in destruction of the plant species claimed as having medicinal properties. Furthermore, leaves carry copious amounts of plant secondary metabolites that have medicinal properties (Bhattarai et al., 2006). Informants claimed that fresh forms of the preparations were considered more powerful than dried ones to treat the ailments in humans and livestock (Figure 2D). Similar results were reported earlier (Endalew, 2007; Seyoum, 2009; Belachew and Behailu, 2018, Abiyot et al., 2018; Nigatu et al., 2018) which could be associated to the components and activities of active principles of fresh preparations. In this study, remedy preparation from single plant parts accounted for 82% and preparations from combined plant species were about 18% (Figure 2D). This consensus was in agreement with Bizuneh et al. (2018) earlier founding.This indicated that preparations from single plant part were reported to be high and disagrees with the earlier report of (Mirutse et al., 1999) who claimed that the combined plant materials were reported to have high proportion in remedy preparations. Medicinal trees and shrubs in the study area were prepared in different forms. The most common mode of preparation was crushing (38%), followed by chewing (32%). This result is in agreement with the earlier founding of Emiru et al. (2011), Gonfaet al. (2015) and Bizuneh et al. (2018) who noted that the principal method of remedy preparation was through crushing. Internal and external route of applications were reported by the informants in the treatment of various ailments. Oral application accounted for 72%. The choice of oral administration is related to the use of some solvents or additives (honey, milk, butter and food) that are commonly believed to serve as a vehicle to transport the remedies (Tolossa et al., 2013; Balcha, 2014; Abiyot et al., 2018; Belachew and Behailu, 2018; Nigatu et al., 2018; Banchiamlak and Young, 2019). The additives are also important to minimize discomfort, improve the taste and reduce adverse effects such as nausea and vomiting. It is also believed to be enhancing the efficacy and healing conditions. Earlier similar   findings   were   reported   by  other  researchers (Mesfin et al., 2009; Filate et al., 2009) indicating the oral route as the most preferred mode of administration. However, there is no consensus on the dosage used and frequency of the medication among healers.

Threats to medicinal plants

In the study area, human related activities such as deforestation, firewood collection  and  construction  were recorded as the main threats to the existence and use of plant species in general and to medicinal plants in particular. Similarly, different scholars Gonfa et al. (2015), Solomon et al. (2016), Abiyot et al. (2018), Nigatu et al. (2018) and Banchiamlak and Young (2019) reported that, the same problem were observed in their study area.

About forty two medicinal plants species were distributed across 29 families and 35 genera as having medicinal properties against 17 human and livestock ailments used by the local community were collected and recorded. The medicinal plant resource in the area is considerable, the Wereda being relatively rich in medicinal plant diversity.  The associated knowledge of the local people is deep-rooted in the time-honoured use practices of herbal medicine. Of the identified medicinal plants, 24 species were noted to treat human ailments, 6 species for livestock ailment treatment and 12 species for both human and livestock health treatments. Shrubs were found to be dominant as traditional medicinal plant remedy sources in the study area followed by trees, herbs and climbers. Leaves were also found to be the most harvested plant parts for the preparation of the remedies followed by bark and roots. In the preparation of medicines, single plants were used to prepare the medicines to cure the diseases rather than mixing with each other. The routes of administration are mainly internal in which oral administration is the common one.  Lack of awareness, agricultural expansion in relation to population growth, secrecy and oral based knowledge transfer were observed problems in the study area. The medicinal plant resources, the associated traditional knowledge and medical practices are in dire need of protection through implementation of appropriate conservation strategies and development of the plants and the knowledge in a modern context. Furthermore, the information generated will also inform future validation studies to increase the acceptability of plant-based remedies in human and animal healthcare systems. Thus, human related activities are threat for the existence of plants claimed medicinal plants calling for creditable measures for sustainable utilization of the resource.

The authors declare that they have no conflict of interests.

The authors’ sincere gratitude goes to Hawassa University for funding this project. They also appreciate the   informants   who   without   reservation  shared  their ethnomedicinal knowledge with them, the elders and the local administration for their support in facilitating the interview process and Hawassa University Department of Botany for supporting them in plant identification process.