Ethnobotanical study of medicinal plants used by people in Zegie Peninsula, Northwestern Ethiopia

Zegie Peninsula (11° 43' N, 37° 20' E) is located at 600 km northwest of Addis Ababa in the country's northwest highlands, at an altitude of approximately 1800 meters. It is partly surrounded by Lake Tana, which is the largest lake in Ethiopia and the source of the Blue Nile. Zegie Peninsula is about three hours motorboat drive or 37 km on land from Bahir Dar, the capital city of Amahra Regional State (Fig. 1). The residents are Amahra people and speak the country's official language Amharic. Tankwas (papyrus boats) of ancient design, manufactured on the shores of Lake Tana, are the alternative forms of transport for the local people between Zegie and Bahir Dar. There are seven monasteries on the peninsula from the 16th and 17th century. Ura Kidane Mhret, one of the monasteries, houses myriads of treasures, beautiful mural paintings, icons, scrolls and thousand-year-old manuscriptsas well as crowns and dresses from Ethiopian Emperors. During the study time, there were no modern health facilities in the area. The main occupation of the people is fishing, and coffee plantation. Until recently, there was no farming practice because the monasteries in the peninsula had forbidden the use of any type of draft animal for farming. Nevertheless, currently, the people have started farming and clearing the forest for agricultural purposes and this may affect the natural habitats of some of the medicinal plants.

The ethnobotanical surveys were carried out from October 2005 to June 2006 using semistructured questionnaire [17] and interview was conducted in Amharic. Prior to the administration of the questionnaire, conversations with the informants were held with the assistance of local Farmers' Association representative to elaborate the objective of the study and to build on trust with the common goal to document and preserve the knowledge on medicinal plants. Two hundred informants were interviewed out of about 2855 inhabitants (1,338 females and 1517 males) of the Zegie peninsula (unpublished data, Bahir Dar Zuria Woreda Administration), these included 130 males and 70 females. Of which, six were male local healers (the only ones found on the peninsula). The female informants' age ranges from 30 to 85 years and the mean age is 51 years, and the male informants' age ranges from 30 to 93 years and the mean age is 64 years. The informants, except the healers, were selected randomly and no appointment was made prior to the visits. They were asked to give their knowledge about the plants they use against a disease, plant parts harvested, method of preparation of the remedy, details of administration and the dosage. Specimens of the reported medicinal plants were collected during regular systematic walk in the fields and identified by specialists at the Aklilu Lemma Institute of Pathobiology and the National Herbarium of Addis Ababa University following the Flora of Ethiopia and Eritrea [18‐21]. Voucher specimens were deposited at the Herbarium of Aklilu Lemma Institute of Pathobiology, Addis Ababa University.

The reported aliments were grouped into 10 categories based on the information gathered from the interviewees. The categories were: evil eye and 'satan beshita' (devil sickness), external injuries and parasites infections, gastrointestinal disorder and parasites infections, 'mich' (febrile disease characterized by fever, headache, sweating, Herpes labialis, and muscle spasm) and febrile diseases, rabies and internal disease, respiratory and throat infections, sensorial disease, snake bite, swelling (non-infectious or infectious swelling) and cancer, and venereal disease and impotence. Informant consensus factor (ICF) was calculated for each category of aliments to identify the agreements of the informants on the reported cures for the group of aliments. ICF was calculated as follows: number of use citations in each category (n_ur) minus the number of species used (n_t), divided by the number of use citations in each category minus one [22].

ICF = n ur − n t n ur − 1 MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacqqGjbqscqqGdbWqcqqGgbGrcqGH9aqpdaWcaaqaaiabb6gaUnaaBaaaleaacqqG1bqDcqqGYbGCaeqaaOGaeyOeI0IaeeOBa42aaSbaaSqaaiabbsha0bqabaaakeaacqqGUbGBdaWgaaWcbaGaeeyDauNaeeOCaihabeaakiabgkHiTiabigdaXaaaaaa@3FB7@

The fidelity level (FL), the percentage of informants claiming the use of a certain plant for the same major purpose, was calculated for the most frequently reported diseases or ailments as:

FL ( % ) = Np N × 100 MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacqqGgbGrcqqGmbatcqGGOaakcqGGLaqjcqGGPaqkcqGH9aqpdaWcaaqaaiabb6eaojabbchaWbqaaiabb6eaobaacqGHxdaTcqaIXaqmcqaIWaamcqaIWaamaaa@3B08@

Where Np is the number of informants that claim a use of a plant species to treat a particular disease, and N is the number of informants that use the plants as a medicine to treat any given disease [23]. These two methods are helpful in the selection of plants for further studies.

Eighty two percent of informants reported remedies for 52 aliments. Of which 26% are females and 74% are males, which indicated that most people continue to use traditional systems of health care including medicinal plants alone or in combination with modern pharmaceuticals. This continued reliance of many African people on traditional medicines is partly due to economic circumstances, which place modern health facilities, services and pharmaceuticals out of the reach of the majority of the population. However, in many cases, it is also attributable to the widespread belief in the effectiveness of many traditional therapies. Even where western biomedical care is available, many people still prefer traditional treatments for treating many aliments [4, 5, 11, 24].

The females reported remedies to diseases associated to children such as 'mich', stomachache, 'kuruba' (diarrhea, dysentery, stomach disorder), dysentery, tonsillitis and babies' sickness (thinning, loss of appetite). The males reported (mean = 6.7 ± 2.79) more number of remedies than the females (mean = 2.3 ± 0.9) and there is a significant difference (p = 0.004) between female and male and agrees with the previous reports of ethnobotanical studies in northern and southern Ethiopia [4, 5]. This is because the traditional knowledge in the family or community is passed from male parent to his first-born son [25, 26].

All the healers were male and the number of aliments reported by them ranged from six to twenty. They also reported combination of multiple medicinal plants to treat an illness, whereas most of the non-healers, both females and males reported only a single medicinal plant treatment (Table 1, 2). The multiple prescriptions reported by the healers usually contain a range of pharmacologically active compounds; in some cases, it is not known which ingredients are important for the therapeutic effect and some are used as adjuvants [27].

The number of ethnomedicinally important plant species documented in Zegie Peninsula was 67. These species belong to 64 genera and 44 families. The genera Asteraceae, Euphorbiaceae, Fabaceae and Solanaceae were families with four species each followed by Malvaceae with three species and, Apocynaceae, Asclepiadaceae, Cucurbitaceae, Dracaenaceae, Moraceae, Rhamnaceae and Rutaceae, each contributing two species.

The most frequently utilized plant part was the underground part (root/rhizome/bulb = 42%) (Table 4). In studies conducted in Ethiopia, root (58.3%) is one of the most extensively used plant part in preparation of traditional herbal medicine [11]. In this study, herbs are used predominantly (52%, Fig. 2) as in most part of Ethiopia (34.8%) [27, 28].

The largest number of remedies was used to treat gastrointestinal disorder and parasites (22.8%) followed by external injuries and parasites (22.1%), rabies and internal diseases (17.9%). The proportion of remedies used for treatment of gastrointestinal related disease are also high in most studies conducted in Ethiopia, accounting for 35% compared to other type of remedies that were compiled as being used against human aliments [28]. The rest were used to treat swelling and cancer (8.3%), evil eye and devil sickness (6.2%), sensorial disease (6.2%), venereal disease and impotence (4.8%), 'mich' and febrile diseases (4.1%), respiratory and throat infection (4.1%), and snake bite (3.4%). Multiple plants treatments with different combinations of medicinal plants were used to treat seven external and internal illnesses. Seventy eight percent of the multiple plants treatments were roots and were prepared by mixing the ingredients with different proportions. Three were used to treat evil eye and one of the poly-herbal remedy had nine medicinal plants (Table 3).

The administration routes are oral (51.4%), external (38.6%), nasal (7.9%), and through the ear (2.1%). The remedies are taken with water, skimmed milk, honey, tef injera (local thin bread made from tef, Eragrostis tef) and boiled coffee. The measurements used to determine the dosages are not standardized and depend on the age and physical appearance of the patient, sociocultural explanation of the illness, diagnosis and experience of individual herbalist [5, 11]. Children are given less than adults, such as, one fourth of a coffee cup (2 ml to 5 ml), whereas, an adult is given up to one glass (approximately 250 ml) depending on the type of illness and treatment. The quantity of plant part used is measured by number of leaves, seeds and fruits, and length of root. For example, seven young leaves of Justicia schimperiana are used to treat ascaris, seven seeds of Calpurnia aurea are used to treat diarrhea and about 2 cm of root of Dorstenia barnimiana is used to treat cancer. The frequency of treatment depends on the type of illness and severity. In preparation of poly-herbal medicines, each medicinal plant is dried, powdered and stored separately, and the amount taken from each for any given disease varies.

Eight species of medicinal plants have veterinary importance. The plant parts used were leaf (62.5%) and root (37.5%). These are used as remedy for seven internal and external illnesses (Table 3). The number of veterinary important medicinal plants is low compared to those areas with culture of cattle raring. Giday and Ameni [29] documented 83 medicinal plants that are used to treat 37 types of livestock aliments. In our study area, people are not accustomed to cattle raring and, therefore, have low knowledge of veterinary important medicinal plants.

The medicinal plants that are presumed to be effective in treating a certain disease have higher ICF values. Table 5 shows disease categories with relatively higher ICF values: 'mich' and febrile diseases (0.80), evil eye and satan beshita (devil sickness) (0.70), and respiratory and throat infections (0.64). This may indicate high incidence of these types of diseases in the region, possibly due to the poor socio-economic and sanitary conditions of the people. The categories of diseases that are only treated by the healers and those that are rare have lower ICF values. These include swelling and cancer (38), and sensorial disease (0.25). The medicinal plants that are widely used by the local people have higher FL values than those that are less popular. On the other hand, medicinal plants that are known as remedies of a single aliment have 100% fidelity level than those that are used as remedies for more than one type of aliment. For example, Plumbago zeylanicum is used to treat cancer, respiratory infection, swelling, and rheumatic pain and its FL value is 40% (Table 6).