The symbolic efficacy of medicinal plants: Practices, knowledge, and religious beliefs amongst the Nalu healers of Guinea-Bissau

Background: In attempting to understand how the use of medicinal plants is symbolically valued and transformed according to specific cosmologies, we gain valuable insight into the ethnopharmacologial practices, in terms of the major role played by healers, as custodians of local ethnobotanical knowledge, but also as ritual masters. Thus, the goal of this paper is to understand how medicinal plants are used differently depending on a combination between the healers' field of expertise and personal history on the one hand, and the diversified religious and symbolical frameworks on the other. Methods: This essay is based on intense ethnographical research carried out amongst the Nalu people of Guinea-Bissau. Methods included participant observation and semi-directed interviews with six locally-renown healers (four men and two women). The progress of their work and the changes operated within the sets of beliefs associated with ethnopharmacological practices were registered by means of repeated field visits. Results: A total of 98 species and 147 uses are accounted for, as well as a description of the plant parts that were used, as well as the methods of preparation and application according to the different healers' specialized practices. At the same time, this research describes those processes based on pre-Islamic and Muslim cosmologies through which medicinal plants are accorded their value, and treatments are granted their symbolic efficiency. Conclusions: Medicinal plants are valued differently in the pre-Islamic medicine and in the medicine practiced by Islamic masters. The increasing relevance of Islam within this context has affected the symbolic framework of ethnopharmacological practices. Nevertheless, the endurance of those processes by which symbolic efficiency is attributed to local treatments based on plants is explained not only by the syncretic nature of African Islam, but also by the fact that patients adopt different therapeutic pathways simultaneously.