Traditional medicine (TM) has been used by humans for thousands of years. The World Health Organization (2002), defines traditional medicine, in part, as a medicine system that includes medication therapies like herbal medicines as a well as non-medication therapies like acupuncture. The same organization defines herbal medicines to include herbs, herbal materials, herbal preparations and finished herbal products, that contain as active ingredients parts of plants, or other plant materials, or combinations thereof. The World Health Organization (WHO) estimates that 80% of the population living in developing countries uses TM for their primary health care needs [1]. However, this percentage varies from country to country. For instance, 90% of the population in Ethiopia, 70% in Rwanda, and 60% in Uganda and Tanzania use TM for their PHC [2]. TM is widely used in Uganda for the prevention, diagnosis and treatment of social, mental and physical illness [3]. Although a diversity of material – plant, animal and inorganic material – are used in traditional medicines, plants dominate.

In Uganda, households possess indigenous knowledge of traditional cures for non complicated ailments. On the other hand, Traditional medicine practitioners (TMPs) are an invaluable source of specialized knowledge about TM and are very important human resources for the practice and delivery of primary health care services [3]. The WHO recognizes the invaluable role of TM and its practitioners, and it is for this reason that the Alma Ata Declaration of 1978 recommended that TM and its practitioners should be integrated into primary health care programmes [4] as important resources for achieving health for all.

Although a majority of people rely on TM, indigenous knowledge (IK) related to TM is getting steadily eroded[ [5]. It is believed that this is a consequence of people adopting new lifestyles and migrating to urban centers [6]. Other workers have identified lack of confidence among users and practitioners as a cause of loss of knowledge of TM [7, 8]. In the African Region, IK is handed down from generation to generation by oral tradition, and sometimes custodians of this knowledge die before passing it on [9].

To control the loss of IK related to TM it is necessary to document and conserve as much of this knowledge as possible in line with WHO policy and as reflected in the different resolutions adopted by the World Health Assembly [10–12] and WHO Regional Committee for Africa [13, 14] on TM and medicinal plants. These resolutions urge Member States to among other things, produce inventories of effective practices as well as evidence on safety, efficacy and quality of traditional medicines and undertake relevant research; to take effective measures in collaboration with other partners; to ensure conservation of medicinal plants and encourage their sustainable utilization; and to respect, preserve and widely communicate, as appropriate, the IK and practices.

Previous studies in Uganda have inventoried herbal medicines and associated IK of processing and administration [3], in general ethnobotanical studies or in disease specific inventories such as those targeting malaria, tuberculosis [15], or HIV/AIDS and related conditions [16]. Owing to the wide cultural diversity and ecological diversity a high diversity of IK including that associated with herbal medicines exists in Uganda. However, little of this knowledge has been documented to date. This study complements the earlier studies by extending our knowledge of herbal medicines in four culturally and ecologically diverse regions of Uganda.

Field research for this project was conducted between October 2008 and February 2009 in the districts of Mukono, Nakapiripirit, Kanungu and Pallisa (Figure 1). These districts were selected because they are rural and remote with poor infrastructure and service delivery. Rural and remote communities are known to be marginalized in terms of access to health services and suffer high levels of poverty because they lack appropriate means of income generation [9]. These factors force people to use traditional medicine (TM) and keeps the indigenous knowledge associated with TM intact.

The communities in the study districts are ethnically diverse and belong to different tribes. The people of Mukono belong to the Baganda tribe. The people of Nakapiripirit are Ngakarimojong by tribe, those of Kanungu are Bakiga and the ones of Pallisa belong to the tribes of the Ateso and the Bagwere. This implies that they have different IK and exploit useful plants in different ways. All these cultural groups subsist on crop agriculture as their main source of livelihood apart from the Ngakarimajong who are nomadic cattle keepers [17].

Data were collected using an ethnobotanical survey. The survey started off with key-informant interviews that included local politicians, elderly people, and a nursing sister as participants. In the key informants interviews the focus was on understanding health seeking behavior.

The plant species used to treat ailments in the home were documented in household interviews using a questionnaire modified from that used by Almeida et al. [18]. To select respondents to participate in the interviews one village was selected serendipitously from each district. In each chosen village between 40 and 50 households were selected by simple random sampling. Interviews with children were conducted at one of the primary school in each of the villages. Ten pupils attending classes between primary 4 and 7, and equally distributed in gender were identified by the head teacher for the interviews. Altogether we interviewed 171 respondents (93 female and 78 male).

Our interviews centered on the following types of information: Common ailments that afflict households; form of health care sought by community members; specific ailments for which people seek health care from TMPs; materials used to treat ailments in traditional medicine; how the materials are used to treat ailments; and perceptions of efficacy.

In order to prioritize among the widely diverse herbal medicine plant species we conducted a Rapid Market Survey to determine the most important medicinal plants. According to Cunningham [19], highly valued species routinely appear in markets. We interviewed 20 market vendors of Owino market specialized in the sale of traditional medicines. Owino market is the largest market in Uganda. Vendors were requested to, among other things, name and rank the most valuable medicinal species. Species mentioned in all interviews were collected and identified with the help of a parataxonomist, and archived at Makerere University Herbarium (MHU). Species were identified using the Flora for Tropical Africa. Species names were verified by making reference to the IPNI (International Plant Names Index; http://www.ipni.org).

Permission to conduct this study was sought for and granted by the Uganda National Council for Science and Technology (SS 2163). In every village we requested for and acquired an endorsement to conduct the study by the local village politicians. Before every interview, the purpose, method and end use for the data collected were explained to every respondent before requesting for permission to interview the respondent.

In this study respondents were seen to self medicate using plants and allopathic medicines. Herbal medicines are frequently used in self medication to alleviate symptoms or shorten recovery time in self limiting ailments^b[22], such as malaria and diarrhea. On the other hand, allopathic medicine is preferred for the treatment of serious diseases and conditions like tuberculosis.

The practice of self-medication is popular in many parts of the world including Africa where the health infrastructure is poor, or where people have a negative attitude about the quality of care in medical facilities, or people can ill afford the consultation fees charged in medical facilities [13, 24, 25]. Respondents in this study stated that TMPs are not usually consulted (except in Nakapiripirit the most marginalized of the study districts). According to Tabuti et al. [3], TMPs are commonly consulted for chronic and difficult to understand ailment. The implications of poor patronage of TMP may be a faster loss of IK associated with TM.

Knowledge of how to treat ailments by respondents is acquired from parents and grandparents. Indeed older people mention significantly more remedies than the young. This is in agreement with studies conducted elsewhere which show that older people have more IK than younger ones and that they are the ones who transmit this knowledge [9].

This survey has indicated that abundant indigenous knowledge on traditional medicine (TM) still exists and that TM is still important in Uganda, because respondents mentioned many species and remedies used in traditional medicine and stated that they use it as a first line of health care when they fall sick. The patronage of TMPs in this study appears to be low. This is somewhat confusing given the reportedly important role that TMPs play in TM [4]. More rigorous health seeking behavior studies should be conducted to clarify this important aspect of TM.

There is need to validate the efficacy and safety of the remedies reported in this study to determine whether they are effective to treat the diseases that they are claimed to treat and are safe to use. Priority species should be those that are used to treat diseases that respondents have observed to be effective and for which people have the highest agreement measured as informant consensus factor (ICF) such as meningitis (Additional file 1: Table S1). The first step in this direction should be to conduct a literature review to see what information exists for the target species before bioassays are conducted in the laboratory.

Secondly, this study was conducted in only four districts of Uganda, and showed that IK varied between districts. This means that more detailed surveys covering the whole country remain to be undertaken to complete the documentation of this knowledge in Uganda. Thirdly, a wider market survey of medicinal plants needs to be conducted to capture the whole diversity of herbal medicine species sold in markets.

^aEnjoka is an all inclusive term that may refer to abdominal worms. It may also mean abdominal cramps/pain which are believed to be caused by worms among other things; gonorrhea; or painful menses in females

^bSelf limiting ailments are disease conditions whose symptoms may disappear even without treatment