An ethnobotanical study of medicinal plants used in Kilte Awulaelo District, Tigray Region of Ethiopia

Background The Ethiopian people have been dependent on traditional medicine, mainly medicinal plants, from time immemorial for control of human and animal health problems, and they still remain to be largely dependent on the practice. The purpose of the current study was to conduct ethnobotanical study to document medicinal plants used to treat diseases of human and domestic animals in Kilte Awulaelo District in the Tigray Region of Ethiopia. Methods Ethnobotanical data were collected between July and September 2011 through semi-structured interviews, ranking exercises and field observations. For the interviews, 72 knowledgeable informants were sampled using purposive sampling method. For the different ranking exercises, key informants were identified with the help of elders and local administrators from informants that were already involved in the interviews. Results The study revealed 114 medicinal plant species belonging to 100 genera and 53 families. The plants were used to treat 47 human and 19 livestock diseases. Of the species, the majority (74%) were obtained from the wild. Herbs were the most utilized plants, accounting for 44% of the species, followed by shrubs (29%). Leaf was the most commonly used plant part accounting for 42.98% of the plants, followed by roots (25.73%). Preference ranking exercise on selected plants used against abdominal pain indicated the highest preference of people for Solanum marginatum. Direct matrix ranking showed Cordia africana as the most preferred multipurpose plant in the community. Preference ranking of selected scarce medicinal plants indicated Myrica salicifolia as the most scarce species, followed by Boscia salicifolia and Acokanthera schimperi. According to priority ranking, drought was identified as the most destructive factor of medicinal plants, followed by overgrazing and firewood collection. Conclusion Medicinal plants are still playing significant role in the management of various human and livestock diseases in the study area with herbs taking the lead in the number of plants used in the preparation of remedies, which may be an indication of their relatively better abundance as compared to other life forms. Recurrent drought was reported to have seriously threatened medicinal plant resources in the District. Awareness is thus needed be raised among local people on sustainable utilization and management of plant resources. Ex situ and in situ conservation measures should be taken to protect the medicinal plants of the District from further destruction and special attention should be given to the medicinal plants that were indicated by preference ranking exercise as the most threatened ones.


Background
About 80% of the Ethiopian population and 90% of livestock still depend on traditional medicinal to fight a number of diseases [1,2]. The reliance on medicinal plants is partly owing to the high cost of modern drugs, inaccessibility of modern health institutions and due to cultural acceptability of the system [3][4][5]. However, as time goes on, the traditional knowledge and the associated plants in the country are gradually being depleted for reasons mainly attributed to environmental degradation and deforestation, which in turn brought about the loss of some important medicinal plants [4,6]. On the other hand, documentation work related to traditional medical knowledge in the country still remains at minimum level calling for conduct of more ethnobotanical studies.
The people of Tigray Region, in general, and Kilte Awulaelo District, in particular, are also expected to have rich knowledge on traditional medicine involving medicinal plants. Such knowledge is, however, currently being threatened, as it is happening elsewhere in the country, due to environmental degradation and deforestation. On the other hand, published reports indicate that only few ethnobotanical studies have been conducted in Tigray to properly document the use of medicinal plants [7][8][9][10]. The studies conducted in the districts of Alamata [7], Enderta [8], Hawzen [9], and Asgede Tsimbila [10] documented 25, 27, 33 and 68 medicinal plants, respectively. However, no such study has far been conducted in Kilte Awulaelo District. The purpose of the current study was, therefore, to gather and document information on the use of medicinal plants by people in Kilte Awulaelo District, in Tigray Region of in Ethiopia, to manage diseases of humans and domestic animals. The study was expected to play a role in prioritizing medicinal plants in the District for further evaluation and conservation.

Description of study district and people
Kilte Awulaelo District is located at 825 km north of the capital Addis Ababa, in the Eastern Zone of Tigray Regional State, Northern Ethiopia. It shares borders with the districts of Howzien and Sease Tsadamba in the north, Atsbi Womberta in the east, Douga Tembien in the west and Enderta in the South (Figure 1). The District is composed of 18 kebeles. Kebele is the smallest administrative unit in Ethiopia. Altitude in the District ranges between 1900 and 2460 meters above sea level. It covers an area of 101,758 hectares, of which 21,620 hectares are farmlands, 7,930.85 hectares are grazing areas, 44,134 hectares are enclosure areas and 28,073.15 hectares are occupied by hills and residential areas [11], Kilte Awulaelo Plan and Finance Office, unpublished data, 2010.
According to 2001-2010 rainfall data, the District has a high rainfall distribution between July and August and a smaller rainfall between March and June and in September. The mean monthly rainfall and mean annual rainfall of the District are 50.14 mm and 601.68 mm, respectively [National Metrological Service Agency, Mekelle Branch Office, unpublished data].
Tigrigna, an official language in Tigray Region, is the language spoken by the people residing in Kilte Awlaelo District. The language belongs to the Semitic language family. Based on the population census of 2007 by the Ethiopian Central Statistical Agency [12], the total population of the District is 111,546, of which 48.89% are males and 51.11% are females.
Malaria, upper respiratory problems, skin infection, infestation of intestinal parasites, pneumonia, soft tissue injury, gastritis, diarrheal, arthritis and eye diseases have been reported as the ten most common diseases in the District. In 2010, there were five functional health centres in the District where the kebeles Agulae, Negash, Beati Akor, Tsige Reda and Abraha Atsbha had one each [Kilte Awulaelo Health Office, unpublished data, 2010].

Selection of study kebeles and informants
Ethnobotanical data were collected between July and September 2011 from nine kebeles that were purposively selected with the help of elders and local authorities of the District based on better availability of traditional healers and knowledgeable people. The kebeles were Ayne Alem, Negash, Tseada Neale, Agulae, Abraha Atsbha, Adi Kesandid, Genfel, Mahbere Weyni, and Mesanu.
For the interview, 72 healers and knowledgeable informants (eight from each sampled kebele) were selected using purposive sampling method [13], of which 61 were males and 11 were females. The informants selected from each sampled kebele were the most knowledgeable ones as suggested by respective kebele elders and administrators who participated in the selection process. The ages of the informants ranged between 20 and 82 years. Three key informant groups (one group containing nine individuals) were respectively involved in three different ranking exercises (two preference ranking exercises and one direct matrix ranking exercise). The key informants were selected from the already interviewed informants with help of elders and local administrators.

Ethnobotanical data collection
Ethnobotanical data were collected through semistructured interviews and observations by following standard methods [13,14]. Series of individual interviews were carried out to gather information regarding local names of plants used, their threats and management, part(s) used, preparations methods, routes of remedy administration, diseases treated and side effects of remedies. The same method was also used to collect data on habit, habitat, marketability and conservation status of the reported medicinal plants. Interviews were conducted using Tigrigna, language that is spoken by the people in the study District. For each reported plant species, specimen was collected, pressed, dried, and identified and voucher was kept at Jimma University Herbarium. Field observations were also used to record habit and habitat of each medicinal plant with the assistance of local guides and interviewed informants. The

Data analysis
The data were summarized using Microsoft Office Excel 2007 computer programme. Descriptive statistical methods were employed to analyze and summarize the ethnobotanical data. Preference ranking exercise [13] was conducted by nine key informants on six medicinal plants used to treat abdominal pain in the District. Abdominal pain was the disease against which the highest number o f medicinal plants was prescribed by informants. The plants used in such exercise were short-listed by the key informants following group discussion on their importance to manage abdominal pain. The informants were given the plants and asked to arrange them based on their personal level of efficacy. Medicinal plant that was believed to be the most effective was given the highest value, i.e. 6, and the one with the least effectiveness a value of 1 and rank was determined based on the total score of each species.
Preference (priority) ranking exercise [13] was conducted by nine key informants on six medicinal plants, shorted-listed by the same, to rank them based on informants' perceived level of threat. A value of 6 was given for the most scarce medicinal plant and 1 for the least scarce ones, and scores of each species were finally summed and ranked.
Direct matrix ranking exercise [13] was employed on seven medicinal plants that were most frequently reported as multipurpose medicinal plants in the study District. A group of nine key informants were asked to rank the plants with different uses (including their use as medicinal plants) through discussion based on their perceived level of usefulness using a numerical scale (0 for no value, 1 for lowest value and 7 the highest value). Values assigned for each plant were added together to determine its rank. Medicinal plant having the highest values is ranked first, an indication of its highest level of threat.

Diseases treated
The plants were used to treat 47 human and 19 livestock diseases. Of the total medicinal plants, 56% were used to treat human diseases only (Table 1), 37% were used against diseases of both human and domestic animals ( Table 2) and 7% were employed to treat diseases of domestic animals only (Table 3). With regard to human diseases, abdominal pain was the one against which a high number of medicinal plants (26 species) were prescribed, followed by wound (21 species), febrile illnesses (19 species), evil eye (19 species), toothache (15 species), ascariasis (15 species), anthrax (14 species), Tinea capitis (12 species), snake bite (10 species), tonsillitis (10 species), eye infection (10 species) and itching (10 species). Preference ranking exercise on six medicinal plants used to treat abdominal pain revealed Solanum mariginatum as the most preferred medicinal plant, followed by Cucumis ficifolius and Olea europaea subsp. cuspidata (Table 4).

Plant parts used and modes of remedy preparations
According to interview results, leaf was the most commonly used plant part accounting for 43% of the total reported medicinal plants, followed by roots (26%) and whole part (6%). It was found out that most remedies were processed by crushing (34%), chewing (12%) or boiling (8%) or used in unprocessed form (8%). The majority (59%) of remedies were prepared from fresh materials only. Some remedies were prepared from either dried or fresh materials (30%) while few (11%) were prepared from dried materials only. Water and different additives such as honey, sugar, butter, salt, coffee, tea and milk were often used in the preparation of remedies. The additives were claimed to either reduce poisoning or improve flavour.

Routes of remedy administration and dosage
More than half (55%) of the remedy preparations were applied externally by spreading them directly on the affected part of the skin, tying or fumigation, and 45% of preparations were applied internally, of which oral was the most commonly used route of application accounting for 36% of the total remedies, followed by local (5%), nasal (3%) and auricular (1%). Result shows that there was no agreement in measurement or unit used among the informants. Most informants used measuring units such as cup, spoon, drops and fingers but still differed in the doses they administered. Most of the remedies were reported to have no adverse effects except for some species such as Phytolacca dodecandra, Euphorbia abyssinica and Nicotiana glauca that were indicated to be poisonous both to human and domestic animals.

Multipurpose medicinal plants
Result of direct matrix ranking conducted by nine key informants on seven selected multipurpose medicinal plants showed Cordia africana as the most preferred multipurpose plant, followed by Eucalyptus globules, Opuntia ficus-indica and Dodonia angustifolia ( Table 5).

Habitats and conservation status of medicinal plants
Out of the total medicinal plants, 84 (74%) were obtained from wild, 16 (14%) were cultivated in home gardens, and 14 (12%) were either grown in homegardens or harvested from the wild.
According to informants, nowadays search for some medicinal plants, especially trees and some shrubs, required a lot of time and travelling long distances. Of the total reported medicinal plants, 48% were rarely encountered, while 43% were commonly found and the rest (9%) were moderately or occasionally encountered. Result of preference ranking exercise on six medicinal plants, reported by the most informants in the District as threatened species, shows that that Myrica salicifolia was among the highly threatened species, followed by Boscia salicifolia, Acokanthera schimperi, Acacia abyssinica, Olea europaea subsp. cuspidata and Acacia abyssinica. The principal threats of medicinal plants in the area were reported to include drought, overgrazing and firewood collection. Informants ranked drought as the most serious threat to medicinal plants followed by overgrazing, firewood collection, agricultural expansion, soil erosion and collection of other different factors.

Discussion
Despite the large scale environmental degradation and recurrent droughts, there is still rich knowledge on the use of medicinal plants in Kilte Awlaelo District. A total of 114 medicinal plants are in use in the study District to treat various human and animal diseases. Similar studies undertaken in Ofla District, Tigray Region, Ethiopia, came up with 113 medicinal plants [15]. As compared to human diseases, diseases of domestic animals in the District were treated with a relatively fewer number of plant species, which could be due to the less  [16,17]. High number of medicinal plants is used in the treatment of abdominal pain and this may suggest the high importance or prevalence of the disease in the study district. The fact that Solanum mariginatum is the most frequently used plant to treat abdominal pain could indicate better efficacy of the plant or its higher abundance in the study District.
Leaf was the most used plant part in the preparation of remedies in the District as compared to other parts. Many studies conducted elsewhere in Ethiopia also showed the dominance of leaves in the preparation of remedies [8,19,[24][25][26][27]. In contrast, another study [28] indicated root as the most commonly harvested plant part in a study carried out in five Districts of Tigray Region, Ethiopia. A study conducted in Mana Angetu District, in Oromia Region of Ethiopia also witnessed the common usage of root [29]. Harvesting root of a plant poses more threat to survival of plant than collecting other parts such as fruits, seeds and leaves [6].
According to current results, herbal remedies are largely prepared using fresh materials. There were also many plants from which parts were claimed to either be used as dried or fresh materials. The fact that both forms are used in the preparation of remedies in a given community creates a better opportunity for people to have access to materials used in medicine preparation across the different seasons of the year.
The current study indicated that there was no agreement in measurement or unit used among informants. Most informants reported use of measuring units such as cup, spoon, drops and fingers but still there was difference in doses. The variation in quantity, unit of measurement, and duration of treatment of prescribed plant preparations was also noted in a study conducted elsewhere in the country [28]. A study reported that lack of precision and standardization of preparations are two of the drawbacks of traditional health care system [20].
The greater proportions of remedies were applied externally, which is in agreement with result of a study conducted in Bench District, south-western Ethiopia [30]. However, studies conducted in Mana Angetu District, south-eastern Ethiopia [29] and Konta Special District, Southern Ethiopia [27] revealed that most medicinal plant preparations were taken internally, out of which drinking takes the highest proportion.
Nearly half of the medicinal plants recorded were herbs which may indicate their relatively better abundance as compared to other life forms. Other studies conducted elsewhere in Ethiopia also indicated the dominance of herbs [16,21,27,28]. However, a study conducted in Mana Angetu District, Oromia Region of Ethiopia, reported the dominance of shrubs in medicinal plant preparations [29]. The fact that most of the woody plants in the current study area are depleted could have forced the local people to dwell more on herbaceous medicinal plants. It is not a common practice in the District to sell medicinal plants in local markets, which is in agreement with the finding of study carried out in Bench District, south-western Ethiopia [30].
The majority of medicinal plants in the study District were obtained from the wild. This result agrees with that of other studies conducted elsewhere in the country [14,19,24,26,27,31]. As most of medicinal plants in the District are harvested from the wild, they are highly exposed to various anthropogenic and natural factors and as a result many of them are rarely encountered. Special attention is needed to be given to the medicinal plants that were indicated by preference ranking exercise as the most threatened ones.
There is little practice of cultivating medicinal plants in the area, which is in agreement with other studies conducted elsewhere in the country [15,24,26]. The local community in the study District is not giving much attention for management of medicinal plants. This could be explained by the lack of knowledge among ordinary people about the importance of medicinal plants as most of them are only known by few knowledgeable people.

Conclusion
Despite the large scale environmental degradation and recurrent drought, medicinal plants are still playing significant role in the management of various human and livestock diseases in Kilte Awulaelo District. In the District, 114 medicinal plants were reported to be used to treat various human and livestock diseases. Relatively higher number of medicinal plants was used in the treatment of human diseases as compared to that used against livestock diseases, which might be attributed to the higher number of diseases affecting the former. Result demonstrated the usage of high number of medicinal plants to treat abdominal pain, probably suggesting high importance or prevalence of the disease in the study District. Solanum mariginatum was the most frequently used plant to treat abdominal pain and this could indicate better efficacy or higher abundance of the plant in the study District. Leaf was the most frequently used plant part in the preparation of remedies in the District. Herbs took the higher proportion of the reported medicinal plants, which could be an indication of their relatively better abundance as compared to other life forms. Recurrent drought was reported to have seriously threatened medicinal plant resources in the study area. Despite this fact, there is little effort in the District to cultivate or mange medicinal plants. Thus awareness is needed be raised among local people on sustainable utilization and management of the plant resources. Ex situ and in situ conservation measures should be taken to protect the medicinal plants of the District from further destruction and special attention should be given to the medicinal plants that were indicated by preference ranking exercise as the most threatened ones.