Study of plants traditionally used in public and animal health management in Seharti Samre District, Southern Tigray, Ethiopia

Background In Ethiopia, medicinal plants have continued to play vital role in fulfilling human and livestock healthcare needs of different communities. However, these valuable resources are being depleted mainly due to agricultural expansion and deforestation. Therefore, immediate action is required to conserve these resources and document the associated knowledge. The purpose of this study was, thus, to document and analyze information associated with medicinal plants that are used in managing public and animal health problems in Seharti Samre District, Southern Tigray, Ethiopia. Methods Ethnobotanical data were collected from July 1, 2011 to December 30, 201 mainly using semi-structured interviews with informants sampled using purposive sampling technique and through field observations. Results The study revealed the use of 90 medicinal plant species in Seharti Samre District for the treatment of several human and livestock diseases. The plants belonged to 46 families and 82 genera. The majority of the medicinal plants were indicated to be harvested from the wild. Leaf was the most frequently harvested plant part accounting for 44% of the reported plants, followed by roots (16%), whole plants (10%) and seeds (8%). The most widely used method of preparation was crushing (37%), pounding (15%) and chewing (13%). Most medicinal plants were applied internally (64.6%), followed by external application on the skin (35.4%). Febrile illness is the disease group in the study area that scored the highest ICF value (0.97), followed by cardio-vascular problems (0.97) and evil eye (0.95). Different preference ranking exercises were also used to determine the most preferred and potential medicinal plants in the study area. Conclusion In Seharti Samre District, medicinal plants are still playing important role in the management of various human and livestock diseases, many of which are harvested for their leaf parts. However, activities of claimed medicinal plants need to be evaluated before recommending them for their wider use. Evaluation priority should be given to medicinal plants with the highest informant agreement as such plants are believed to have better activity.


Background
The problem of health in African countries, including Ethiopia, is very acute as people have no full access to government and private health services. The absence or inaccessibility of modern healthcare services and other factors such as high cost of modern drugs and services and better curing of herbal remedies against some chronic diseases has caused a large percentage of the population to rely on traditional medicine, and mostly on herbal remedies [1,2], for its primary health-care needs. In Africa, up to 80% of the population relys on traditional medicine to help meet its health care needs [3].
Ethiopia is a land of high variation in landscape, flora and fauna, multiplicity of ethnic groups with complex multicultural diversity, languages, cultures and beliefs which have in turn contributed to the high diversity of traditional knowledge and practices of the people including the use of medicinal plants. In Ethiopia, medicinal plants play important role in fulfilling human and livestock health care needs of different communities. Traditional use of medicinal plants has remained as the main alternative solution for different human and livestock health problems largely due to shortage of pharmaceutical products and modern health service stations, unaffordable prices of conventional drugs and drug resistance [4].
Today, many Ethiopian medicinal plants are facing extinction or severe genetic erosion mainly due to agricultural expansion, deforestation, over exploitation and destructive harvesting. Securidaca longipedenculata and Warburgia ugandensis are among the popular medicinal plants in Ethiopia that are being threatened due to over exploitation and destructive harvesting. Hagenia abysinica is another medicinal plant that is being depleted as a result of over exploitation [4]. For most of the threatened and endangered medicinal plants, no conservation action has been taken, and there is no even a complete inventory of these plants. Much of the knowledge on the uses of medicinal plants in the country is still held only by traditional societies and is usually transmitted verbally [5]. Unless the plants are conserved and the associated ethnomedicinal knowledge documented, there is a danger that both the valuable medicinal plants and the knowledge could vanish forever. As it is happening elsewhere in the country, medicinal plants of the Seharti Samre District of Tigray are facing the danger of being lost unless appropriate documentation and conservation measures are taken.
A number of ethnobotanical studies have previously been conducted in different parts of Tigray to document the use of medicinal plants [6][7][8][9][10][11][12][13][14]. For example, studies conducted by Teklay et al. [12], Abdurhman [9] and Zenebe et al. [13] reported the use of 114, 113 and 68 medicinal plants in Kilte Awlaelo, Ofla and Asgede Tsimbila districts, respectively. However, there is no record that indicates the documentation of medicinal plants used by the people of Seharti Samre District. The purpose of this study was, therefore, to document and analyze traditional knowledge of medicinal plants used to manage human and animal health problems in Seharti Samre District, Southern Tigray, Ethiopia.

Description of the study area
The study was conducted in Seharti Samre District (Woreda) located between 12 0 30' and 13 0 02' latitude north and 38 0 59' and 39 0 26' longitude east in south east of Tigray at about 57 km southwest of Mekelle, the capital city of Tigray Region and 820 km north of Addis Ababa ( Figure 1). The District has undulated type of landscape with altitude ranging from 1470 to 2370 meter above sea level (m.a.s.l) (Seharti Samre District Rural Agricultural Office, unpublished data of 2011). The District has warm and hot climate conditions and unimodal rainfall distribution that extends from April to September with the highest peak in July and August.
The great majority of inhabitants in the District belong to Tigray ethnic group. According to unpublished report of 2011 obtained from Seharti Samre District Health Office, the public healthcare coverage of the District reaches 85%. However, there are people who still rely on traditional medicine due to low cost of the service and more preference to the system. A study by Yirga [8] reported the use of 27 medicinal plants in the neighbouring District of Enderta. In the District, there are five health centres and eighteen health posts. Pneumonia, skin diseases, malaria, intestinal parasites infection and diarrhoea, acute respiratory tract infection, gastritis, urinary tract infection, diarrhoea, snake bites and conjunctivitis are the top ten human health problems in the District (Seharti Samre District Health Office, unpublished report, 2011). Anthrax, black-leg, trypanosomiasis, bloat, gland swelling, cough and intestinal diseases are the major livestock diseases in the District (Seharti District Samre Veterinary Health Office, unpublished report, 2011).

Selection of study sites
The study was conducted in Seharti Samre District from July 1, 2011 to December 30, 2012. Prior to conducting this study, proposal approval letter was received from Jimma University Ethical Review Committee (ERC) and verbal informed consent from each informant who participated in the study.

Sampling of informants
Purposive sampling method was employed to select 66 traditional healers and knowledgeable individuals (55 men and 11 women) between the ages of 20 and 76 years for semi-structured interviews. Informants that were involved in preference/priority and direct matrix rankings were selected randomly from those healers and knowledgeable individuals that were already sampled for the interviews.

Collection of data and plant specimens
Semi-structured interviews and field observation [15,16] were employed to collect ethnobotanical data. Individual interviews were held with informants to gather data on medicinal plants with regards to plants parts used, methods of preparation, dosage, route of administration, diseases treated, threats, conservation status, cultivation practice, marketability, acquisition/transfer of indigenous knowledge and attitudes of people towards using such plants. All communications with informants were held in Tigrigna, the official language of Tigray Region. Specimens of medicinal plans were collected, dried and identified with the help of botanists at Aklilu Lemma Institute of Pathobiology and the National Herbarium, Addis Ababa University (AAU) and were deposited at the Jimma University Herbarium.

Data analysis and presentation
Microsoft Excel spreadsheet software was employed for organizing and analysis of ethnobotanical data. Descriptive statistical analysis was employed to determine the number of medicinal plants used and ailments treated in the study District, the most frequently used plant parts, main routes of remedy administration and to identify popular medicinal plants, main ways of knowledge acquisition/transfer, major habitats of the plants and their marketability.
Informant consensus factor (ICF) was calculated for each ailment group to estimate level of agreement among informants in the selection of plants against a given category. ICF was calculated using the formula ICF ¼ nur−nt nur−1 [17] where ICF stands for informant consensus factor, nur for number of use citations in each category and nt for number of species used.
Preference ranking technique [18] was used to identify the most preferred medicinal plants used in the District to treat snake bite based on informants' personal preference or perception. Snake bite is one of the ten most important human health problems in the District. It is also among the ten diseases with the highest ICF values. The most preferred plant was assigned the highest score (6), while the least effective one was given the lowest value (1). For this purpose, eight individuals were randomly selected from the people that had already served as key informants. Each informant was provided with fresh specimens of six medicinal plants having the highest frequency of report by informants for being used to treat snake bite. The informants were then asked to rank the plants according to their degree of preference.
Priority ranking exercise [18] was also performed by seven informants to rank different factors perceived as threats to medicinal plants in the study area based on level of destructive impacts. During exercises, informants assigned values 1-4, 1 for the least destructive threat and 4 for the most destructive one.
Direct matrix ranking [16,18] was performed for six commonly reported multipurpose medicinal plants. Based on the relative benefits obtained from each plant, a group of five informants were asked to discuss and assign, to each attribute, a value between 1 and 4 (1 for the lowest value and 4 for the highest value). Scores were then added and plants ranked.

Acquisition/transfer of medicinal plants knowledge
Majority (65.6%) of informants reported that transfer of knowledge on medicinal plants in the study District took place along the family line, from parents to children. Some informants (21.2%) reported close relatives as sources of knowledge while other informants (9.1%) indicated transfer of the knowledge on payment (9.1%) and few reported acquisition of knowledge through trial and error methods (6.1%). Results of interviews also revealed that 69.7% of the informants were willing to transfer their knowledge of medicinal plants along the family line verbally and 9.1% reported that they were happy to transfer the knowledge verbally assisted by practical demonstration. Other informants (21.2) reported that they had no interest to transfer their knowledge at all.

Comparison of medicinal plant knowledge between age groups
Analysis was made to compare medicinal plant knowledge among two age groups Result revealed that members belonging to the age group above 40 year reported an average of 2 medicinal plants while those belonging to the age group between 20 and 40 years reported an average of less one medicinal plant. During interviews and field visits, informants above 40 years of age were found to be very conversant on how to collect plants, process remedies and administer them. Besides, older informants had stronger belief in the curative effect of their medicinal plants as compared to the younger generation.

Medicinal plants reported and diseases treated
Ninety medicinal plant species that were used for the treatment of 51 human (Table 1) and 25 animal diseases ( Table 2) were reported by the informants in Seharti Samre District. Of the total medicinal plants, 62 were used to treat human diseases only, 25 to treat both human and animal diseases and three to mange animal diseases only. The medicinal plants belonged to 46 families and 82 genera. The family Solanaceae was represented by 9 species, Lamiaceae by 8 species, Fabaceae by 6 species, Asteraceae and Euphorbiaceae by 5 species each, Malvaceae by 4 species, Boraginaceae and Capparidaceae by 3 species each. The families Rutaceae, Asclepiadaceae, Apocynaceae, Brassicaceae, Cucurbitaceae, Oleaceae, Rhamnaceae and Vitaceae contributed 2 species each and the remaining 28 families were represented by one species each. Most of the recorded medicinal plants were shrubs and herbs accounting for 42.2% and 39%, respectively, followed by trees (14.4%) and climbers (4.4%).

Plant part (s) and methods used in preparation of remedies
Leaves were the most preferred plants parts used in the preparation of remedies (44%), followed by roots (16%),                (Figure 2). Crushing (37%), pounding (15%) and chewing (13%) were dominantly used in the preparation of remedies ( Figure 3). Substances such as cold water, honey, coffee, butter, salt, sugar, soap, ash and milk were mixed with the plant materials during remedies preparations. The majority (60%) of remedies were prepared from fresh plant materials. Some (21.1%) were prepared from either dry or fresh materials and others (18.9%) from dry parts only.

Route of remedy administration and dosage
Most medicinal plant preparations were applied internally (64.6%), out of which drinking took the lead (44.5%). Some are applied externally on the skin (35.4%), of which 42.5% are smeared on the skin (42.5%) ( Table 3). Informants reported that dosages differed among traditional medicine practitioners even in treating the same health problem as remedies are prescribed with units of local measurement such as pinch, tea spoon (powder), tablet size of seed (semisolid), coffee cup, tea cup and water cup (liquid), finger length (root) and fist (leaves).  (Table 4).

Informants' preference on medicinal plants used to treat snake bite
Preference ranking exercises of six selected informants indicate that Rhoicissus tridentata was the most preferred plant in treating snake bite, followed by Nicotiana tabacum (Table 6).

Multipurpose medicinal plants
The people in the study district relied on locally growing plant species for various purposes such as construction,   Table 7).

Habitats of and threats to medicinal plants
The majority (60.2%) of medicinal plants were collected from the wild. Some (29%) were also collected from both farmlands and roadsides ( Figure 4). According to reports of informants, agricultural expansion is considered as number one threat to the survival of medicinal plants in the study area, followed by, cutting of trees for charcoal and fire wood consumption (Table 8).

Marketed medicinal plants
Local market survey carried out in three towns of the District, namely Samre, Wenberta Adekeala and Fina Rewa revealed that plants were not sold in the markets for their sole medicinal purpose. The medicinal plants Klinia odora, Lepidium sativum, Allium sativum, Rumex abyssinicus, Plumbago zeylanica, Linum usitatissimum and Ruta chalepensis were sold primarily for their uses as species and food.

Discussion
It is encouraging to find out that a high number of medicinal plants (90 species) are still being used by people in Seharti Samre District of Tigray Region, northern Ethiopia, to treat several human and livestock diseases. Ethnobotanical studies conducted in Ofla and Raya-Azebo districts of the same Region [6] came up with comparable numbers of medicinal plants, 83 and 60 species, respectively.
Several of the medicinal plants that were recorded from Seharti Samre District, were also mentioned in reports of studies previously conducted in Ethiopia, some of which (e.g. Aloe sp, Ficus palmata, Justica schimperiana, Lepidium sativum, Linum usitatissimum, Nicotiana tabacum, Otostegia integrifolia, Ricinus communis, Rumex abyssinicus, Ruta chalepensis and Zehneria scabra) [6,19] were exactly used for same medicinal purposes, which could be an indication of their pharmacological effectiveness.
Analysis of the data revealed Solanaceae, Lamiaceae and Fabaceae as the highest contributors of medicinal plants in the Seharti Samre District, which could be a reflection of their dominance in the flora of Ethiopia and Eritrea [20,21] in terms of their species richness. The study also showed that people in the study District use a relatively high number of shrubs and herbs, which is in agreement with studies conducted elsewhere in the country [22].
It was found out that two-third of medicinal plants in the study District were harvested from the wild, which is in agreement with reports of many studies conducted in the country [6,23,24]. Medicinal plants growing in the wild are highly exposed to different anthropogenic factors such as agricultural expansion, deforestation for   charcoal and fire wood consumption, grazing, and harvesting for timber production and construction [22]. Olea europaea subsp. cuspidata, Maesa lanceolata, Cordia africana, Croton mycrostachyus, Acokanthera schimperi, Phytolacca dedocandra) are among the medicinal plants that were reported to be highly affected by the aforementioned factors. Leaves and root were the most commonly used plant parts in the preparation of remedies in the study District. Many studies conducted in different parts of Ethiopia also showed that leaves are used more frequently than any other parts [6,25,26]. As compared to other parts, damage inflicted on medicinal plants due to harvest of leaves is very minimal [27].
Most of the medicinal plant species were reported to be processed through crushing followed by pounding and chewing. Ethnobotanical studies conducted in different parts of the country [9,25,26] reported similar results. Majority of the remedies in the study District were reported to be taken internally/orally followed by smearing on the skin. Several studies conducted in different parts of the county [28] also revealed that oral followed by dermal were the principal routes of remedy administration.
One of the major problems in traditional medicine is lack of standard dosages and précised measurements [5]. According to informants in the study District, the amount of dosage prescribed for same/similar health problems vary as remedies are prescribed with different units of local measurement. Inconsistency of doses has also been reported in studies conducted elsewhere in Ethiopia [6,29,30].
The study revealed that informants above the age of 40 years had relatively better knowledge of medicinal plants as compared to the younger ones (20 to 40 years old). Similar study conducted among the Zay community in Ethiopia [24] revealed that 90% of the elders above 40 years of age had rich medicinal plant knowledge. Study conducted in Nigeria [31] reported that the highest percentage of younger generation had no any knowledge of traditional medicine practice due to more exposure to modern life style. This may demonstrate the impact of modernization on medicinal plant use and transfer of the associated knowledge to the younger generation. The fact that most of the knowledge on traditional medication is kept with elders for the sake of secrecy, gaining respect and generating income is believed to contribute towards depletion of the same as generation passes by.

Conclusion
A total of 90 medicinal plants were reported by informants from the study District. As most of the medicinal plants were harvested from the wild, appropriate conservation measures are required to ensure their sustainable harvesting besides to efforts of aawareness creation among the community by concerned bodies regarding the usefulness of their medical plants. The efficacy and safety of the claimed medicinal plants need to be evaluated before recommending them for their wider use. Priority should be given to medicinal plants with the highest informant agreement as such plants are believed to have better activity.