Malaria remains a major cause of morbidity and mortality especially in sub-Saharan Africa. Whereas herbal medicines have long been used for disease remedy in many African communities, there is limited evidence on the extent of use, their safety, and efficacy. This study, sought to identify herbal medicinal plants used by communities in low and high malaria transmission settings in Uganda for managing of malaria.

An Ethnobotanical survey was conducted across four geographical regions purposively selected to represent moderate-to-high (Apac, Arua and Tororo districts) and low (Kabale district) malaria transmission settings. One-hundred and two (102) traditional medicine practitioners (TMPs) in Ugandan local communities were included in the study. A checklist was used to collect data and covered the following areas; knowledge on malaria transmission, malaria symptoms, diagnosis, medicinal plants used, preparations, preservation methods and doses. Data was analyzed in MS Excel^®. Consensus factor, use value metrics and frequencies were calculated.

Ninety-seven plant species distributed across 45 families were mentioned by TMPs in management of malaria in Ugandan communities. Plant family Asteraceae, 15.5% (15/97) had the highest distribution of plants reported by TMPs. Vernonia amygdalina Delile, Aloe vera Burm. F., Artemisia annua L., Vernonia grantii Oliv. and Justicia betonica L. were the most mentioned, with use values of 0.4, 0.3, 0.2, 0.15 and 0.14 respectively. Leaves 64% and root barks 18% were the most harvested plant parts while decoctions (54%) and infusions 26% were the most common methods of preparing herbal products for individuals with malaria. Medicines were stored as dry powders for extended periods although some were prepared as fresh plants. Nearly all medicinal preparations were administered orally with varying dosage (5 ml-500 ml*3times a day) recommendations. Treatment duration varied between 3 and 7 days among practitioners. TMPs mentioned that malaria is transmitted by mosquitoes while others, said poor hygiene, stagnant water and body contact.

A diverse number of plant species, use and preparation methods are documented in this study as a way of preserving traditional knowledge in Uganda. Vernonia amygdalina Del., Aloe vera (L) Burm. f, Vernonia grantii Oliv. and Justicia betonica L. were identified as important plant species that can be further studied to validate their safety, antiplasmodial and active bioactive phytochemicals that can provide novel lead compounds for malaria treatment. These plant species can also be conserved through cultivation for sustainable use.

In Uganda, malaria is estimated to be responsible for 30–50% of out-patient visits, 15–20% of hospital admissions and up to 20% of in-patient deaths [1]. Malaria is thus one of the leading causes of morbidity and mortality in the country especially among children under five years [2]. Uganda is among the six African countries that account for approximately 55% of the global malaria burden [3]. The stagnation in malaria eradication efforts poses a challenge for the attainment of the sustainable development goals which target a reduction of 95% malaria incidence and mortality by 2030 [4].

Artemisinin-based combination therapies are the mainstay in malaria treatment however, recent studies in northern Uganda report prevalence of slow clearing parasites [5, 6]. Furthermore, the studies found increasing prevalence of K13 gene mutations, 469Y and 675 V associated with artemisinin resistance among P. falciparum parasites. With no known effective therapeutic alternatives to artemisinin-based agents, widespread emergence of artemisinin resistance threatens to worsen malaria disease outcomes especially in sub-Saharan Africa [7]. This calls for continuous search for effective alternative agents for malaria treatment especially from medicinal plants.

For millennia, majority of the modern medicines have been developed from natural products or their derivatives. Particularly, the history of antimalarial drug development and treatment is intimately linked with medicinal plants and quinine, the first drug that was used for treatment of malaria was isolated from the Cinchona tree in 1820 [8]. In 1945, Chloroquine, a 4-aminoquinoline was synthesized from quinine and it became the first line treatment of un complicated malaria replacing its congener quinine. However, in the early 1960s, there was a high spread and mortality of P. falciparum chloroquine resistance which inspired researchers to actively develop effective alternative antimalarials against chloroquine-resistant malaria. Accordingly, many antimalarials such mefloquine and halofantrine were synthesized and in 1973, a novel sesquiterpene lactone called qinghaosu and later renamed artemisinin, was isolated from the Chinese herb Artemisia annua L [9]. Artemisinin has a unique mechanism of action which involves the heme-mediated decomposition of the endoperoxide bridge to produce carbon-centered free radicals that are toxic to the parasite [10]. However, because of its poor bioavailability, more potent derivatives such as artesunate, arteether, artemether and dihydroartemisinin were synthesized [9]. In order to increase the sensitivity of P. falciparum to artemisinins and defer drug resistance development WHO recommends Artemisinin based combination therapy (ACTs) which involves combining an artemisinin derivative with another antimalarial drug like lumefantrine, mefloquine, amodiaquine, sulfadoxine/pyrimethamine, piperaquine and chlorproguanil/dapsone [11]. ACTs have thus remained the focal drugs for treatment of P. falciparum malaria. As such the role of plants in the development of novel antimalarial agents cannot be under estimated especially due to the diverse repository of compounds with potential antiplasmodial activity.

Rural communities in Uganda and many parts of the world continue to use plant-sourced remedies against several ailments, including malaria. With the emerging reduction in efficacy of the current antimalarial agents and continued high burden of the disease, the need for efforts towards discovery and development of new effective therapies cannot be overstated. Previous studies [12,13,14,15] have documented the use of medicinal plants in treatment of malaria however such studies have mainly focused on the central and western regions of Uganda while high malaria settings like Apac and Arua have not been considered. A comprehensive assessment through ethnobotanical surveys of medicinal plants used in local communities in Uganda is key to preserve traditional knowledge, to conserve the important plant species and to provide baseline information about plant species needed in the drug development pipeline. This study, thus sought to document knowledge on herbal medicinal plants used for managing malaria by Ugandan communities in low, and high malaria transmission settings including Arua, Apac, Tororo and Kabale districts.

This was a cross sectional study. We used a descriptive exploratory approach to investigate communities’ knowledge on medicinal plants used for managing malaria. Aspects such as: (i) socio-demographic characteristics, (ii) knowledge on malaria symptoms and transmission, (iii) medicinal plants used for managing malaria, (iv) medicinal plant preparation, (v) source of the plant collection, (vi) drug administration and duration of treatment, and (vii) methods of preservation of the herbal preparations were investigated.

The study was conducted among in four rural districts of northern (Arua and Apac districts), eastern (Tororo district) and western Uganda (Kabale district) (Fig. 1) between October-December 2024. The districts were purposively selected based on malaria transmission intensities. Arua, Apac and Tororo districts are high transmission malaria areas while Kabale district is a low transmission area.

Arua district is located in west Nile, covering a total of 3,236.4 km² between latitude 20º 30’N and 30º 50’N and longitude 30º 30’E and 31º 30’E with a population of 820,500 people. It is bordered by Maracha district in the North West; Yumbe in the North East; Democratic Republic of Congo in the West; Nebbi in the South; Zombo in the South East; and Amuru district in the East. The major economic activity in the district is crop farming.

Apac district is in northern Uganda, located between longitudes 32^o E and 34^o E and latitudes 2^o N and 3^o N. It occupies an area of 3,255.9 km2 of which 9% is under swamps and water while 15% is under forest. It has a population of approximately 349,000 people.

Tororo district is a predominantly rural district in the Eastern region of Uganda that is 241,551 square kilometres large and located between latitude: 0° 44’ 59.99” N and longitude: 34° 04’ 60.00” E. It has a population of approx. 517,000 people. Wetland rice growing is the major economic activity in Tororo District favoring mosquito breeding especially in rainy seasons that are characterized with flooding.

Kabale district is in the western region of Uganda between longitudes 29° 34’ E and 35° 0’ E latitude 1° 29’ S and 4° 12’ N, it harbors a population of approximately 248,700 distributed in 19 subcounties and 1,345 villages. The altitude of Kabale district ranges between 1,219 and 2,347 m above sea level and temperatures average 18ºC during day and 10ºC at night. The major economic activity is agriculture.

The study was done among adult TMPs and were purposively selected based on their reputation of using medicinal plants to manage malaria and willingness to participate in the study by providing written consent.

In each of the four districts (Arua, Apac, Tororo and Kabale), two sub counties were randomly selected i.e. Ayiva and Vurra from Arua District, West Budama and Tororo from Tororo District, Ibuje and Akokoro from Apac, Kabale North and Kabale south from Kabale Districts. From each of the sub counties, two villages were selected (Fig. 1). Within each village, TMPs were purposively selected. The interviews were conducted using a pretested key informant interview guide adopted from a previous study [16] with few modifications. The interview was conducted for an average of 30–45 min and written consent was sought and obtained from all TMPs that participated in the study. For each plant species that was mentioned in the study, a voucher specimen indexed as L 001- L 110 was prepared, identified by a taxonomist (Dr. Ssegawa Paul), and achieved at the Makerere University Museum. All plant species were named using Flora of Tropical East Africa (FTEA). Administrative clearance to conduct the study in the different Districts and villages was sought from the Resident District Commissioner and local councils respectively.

Numerical data were entered in MS Excel^© program where the relevant metrics were generated. Informant Consensus Factor (FIC) and Use Value (UV) metrics were computed. The FIC estimates homogeneity of information concerning use of medicinal plants for a particular ailment. It is calculated using the following formula [17].

where Nur = the number of use-reports in each category and nt = number of taxa used. On the other hand, the UV metric estimates the commonness of use of each plant species in each area and was determined using the following formula (20):

Where Nur is the number of use reports and Ni is total number of informants surveyed.

Map of Uganda showing location of study districts, sub counties and villages

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A total of 102 TMPs from high 74.5% (76/102) and low 25.4% (26/102) malaria transmission settings participated in the study. Of these 65.7% (67/102) were males (Table 1). The mean age of the TMPs was 54 ± 2 years (range of 27–85). Majority, 71.5% (73/102) of the TMPs had completed the primary level of education while 19.6% (20/102) had no formal education. Most participants practiced herbal medicine as a secondary occupation and majority were primarily subsistence farmers.

The common symptoms of malaria mentioned by traditional medicine practitioners included fever 94% (96/102), headache 67.6% (69/102), vomiting 62.7% (64/102) and convulsions 51.9% (53/102) (Fig. 2). Majority, 69.6% (71/102) of TMPs mentioned that malaria was spread through mosquito bites and over half, 64.7% (66/102) reported using symptoms in diagnosing malaria among individuals seeking care. A third 35.2% (36/102) of the TMPs mentioned managing individuals who already had malaria diagnosis from hospitals. TMPs neither had knowledge on the malaria causative parasite nor the conventional management of the disease as per the national malaria treatment guidelines. Participants also mentioned body contact, sharing utensils, drinking dirty water, stagnant waters, not sleeping under a mosquito net and a bushy environment as some of the other factors aiding malaria spread.

Shows symptoms of Malaria as mentioned by Traditional medicine practitioners and their frequency of mention

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TMPs were on average receiving 8±2 malaria patients per month in high transmission areas and 2–3 patients in low transmission areas. The duration of treatment for each malaria symptomatic patient varied among different TMPs ranging from 3 to 7 days. Traditional medicine practitioners mentioned that in most cases (96/102), their patients recovered, and this was assessed through self-reports. Those that did not recover were referred to health centers for further management. The cost of treatment varied widely amongst different TMPs. For some, treatment was free, and patients simply appreciated or gifted the practitioner after recovery. In high malaria transmission settings, treatment costs ranged between Uganda shillings 2000–10,000 (equivalent range 0.5-3 USD).

A total of ninety seven (97) plant species were mentioned by study participants across the four districts for treatment of malaria (Table 2). Plant species were distributed across 45 families with Asteraceae 15.5% (15/97) having the highest frequency (Fig. 3). Vernonia amygdalina Del (41) and Aloe vera (L.) Burm. F. (32) were the most mentioned with use values of 0.4 and 0.3 respectively. These were followed by Artemisia annua L. (21), Vernonia grantii Oliv. (15), Justicia betonica L. (14), Senna hirsute (L.) H.S. Irwin and Barneby (10), Psidium guajava L. (8), Schkuhria pinnata (Lam.) O. Ktze (8), Tetradenia riparia (Hochst.) Codd (5) and Sarcocephalus latifolius (smith)Bruce (5) among others. Plant spp like Aloe vera and Justicia betonica L. were mentioned by practitioners in all the four regions surveyed. The Informant Consensus factor in this study was calculated as 0.82.

Number of plant spp distributed among different families.

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Leaves were most frequently used (69%) in herbal medicine preparations followed by root bark (20%) and stem bark (7%) (Fig. 4). Most medicines were prepared in combination using methods such as by decoctions (54%) followed by infusions (26%), maceration (12%), and powder (7%) (Fig. 5). Medicinal products were stored as powders if the place of collection was far from the TMP however, most medicines were prepared and used fresh as and when needed. The oral route was principally used for treatment administration. The dose recommendations varied widely amongst the different TMPs and ranged from ½ teaspoon (~ 5mls) 2 or 3 times daily to 1 cup (~ 500 ml) taken 2 or 3 times daily. Plastic bottles, polythene bags and papers were used as storage material. In Kabale district, most TMPs cultivated their own medicinal plants as compared to other districts where plants were picked from nearby gardens, forests, or hills where they are abundant.

Plant parts used by TMPs for preparation of antimalarial herbal medicine in different parts of Uganda

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Preparation methods used by traditional medicinal practitioners as reported in different parts of Uganda

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Uganda ranks third among countries with the highest burden of Malaria in the world [2]. Malaria affects communities in rural settings in endemic areas with favorable climatic conditions for mosquito vector breeding [73]. Such conditions include ample rainfall (average 200 mm), optimal temperatures (26–47ºC), swamps, water bodies and forest cover. The high malaria transmission intensity in the three study districts of Apac, Arua and Tororo range from 390 to 1586 infective bites per person per year. Worse still, in such impoverished communities, the cost of antimalarial treatment coupled with long distances to health facilities fuels the use of alternative medicines such as medicinal plants for malaria treatment.

The results of this study show that communities in Arua, Apac, Tororo and Kabale districts use a diverse number of plant species for management of malaria. Plant species like Vernonia amygdalina Del, Aloe Vera (L.) Burm.f., Artemisia annua L., Vernonia grantii Oliv. and Justicia betonica L. were the most used across the four surveyed local communities and they contribute to the high informant consensus factor. The use of Vernonia amygdalina, Artemisinin annua, Aloe vera and Justicia betonica L. for treatment of malaria is well documented across Uganda in previous studies [66, 74, 75]. The wide use of the plant species by different communities across Uganda poses a challenge of sustainability and plant conservation strategies should be encouraged.

Artemisinin annua, from family Asteraceae has strong antimalarial activity and is the source of current antimalarial drugs including dihydroartemisinin, artemether and artesunate. However, recently, there is increasing artemisinin drug resistance reported especially in northern Uganda, calling for more efforts to search for novel compounds [76]. Vernonia amygdalina, a renowned antimalarial plant in communities, yielded two alkaloids namelyvernodalin and vernolide with median inhibitory concentrations of 0.52 µg/ml and 1.87 µg/ml against a chloroquine sensitive strain of P. falciparum (D10) [19] (Table 3). Similarly, fagamine a secondary carboxamide, isolated from Zanthoxyllum Chalybeum had an MIC value of 2.85 µg/ml [77]. The three phytochemicals can be used as leads for development of new antimalarial drugs.

35% (34/96) of the plant species in this study have been evaluated for their in-vitro antiplasmodial activity (Table 3). This verifies and confirms their local use in the Ugandan communities for treatment of malaria. From previous studies, plant species such as; Psidium guajava, Senna occidentalis, Harrisonia abyssinica, Moringa oleifera, Hoslunda opposita, Azadiracha indica, Ageratum conyzoides, Chemopodium opulifolium, sida rhombifolia and Carissa spinarum were very active with minimum inhibitory concentrations < 5 µg/ml [26, 32, 44, 45, 49, 54, 56, 71]. With the high antiplasmodial activity, these plants can be potential sources for new antimalarial drugs. On the other hand, medicinal plants such as Vernonia granti Oliv. with a high use value is yet to be investigated for its anti-plasmodial activity.

Most of the active and mentioned plant species belong to family Asteraceae which is one of the largest families in the plant kingdom with over 2500 species distributed widely all over the world. The family is knowned for its diverse pharmacological activities owed to presence of numerous phytochemicals including phenolic compounds like quercetin (a) that has shown significant antimalarial activity invitro [78,79,80].

Most herbal medicines were prepared as decoctions or infusions. An infusion is prepared by soaking fresh plant parts for a short period of time with cold or boiling water while a decoction is prepared by boiling two or more plant spp at minimum heat for a given period of time [81]. Decoction is a common method of medicine preparation among local communities; for instance, one of the TMPs in this study mentioned that Zanthoxylum chalybeum and Sarcocephalus latifolius are dried, pounded and boiled together in water and then 150 ml are taken three times a day. Another TMP mentioned that Vernonia grantii, Crotalaria ochroleuca, aloe vera and Justicia betonica are boiled together and 200mls are taken once per day. The combination of different medicinal herbs ensures use of less plant materials thus potentially minimizing toxic effects while maximizing efficacy through additive or synergistic effects. Also, some plant species in the decoction play different roles for example, Azadirachta indica (A. Juss) in a preparation can act as an antipyretic to control high temperatures [82]. On the other hand, Euclea racemosa contains phytosterols that possess anti-inflammatory and anti-pain activity; it was noted that in this study, TMPs rub the plant powder on joints to control joint pain [83]. Eucalyptus is also added in herbal medicines as a preservative to prolong the shelf life of the herbal products [84].

This study showed that TMPs in the surveyed communities had knowledge about malaria disease and its mode of transmission. This was evident by the symptoms most frequently mentioned which were consistent with the well-known clinical symptoms of malaria. On the contrary, practitioners demonstrated limited knowledge about the malaria causative agent and lacked sufficient knowledge on conventional treatment of malaria. Furthermore, the variable nature of dosing among different practitioners, even within the same village was concerning as it shows a lack of dose standardization. Dose standardization presents a challenge that has long been experienced among TMPs mainly due to the numerous and diverse bioactive phytochemicals contained in plant based medicines, numerous range of indigenous healing practices, lack of training for the TMPs, lack of a basic knowledge of the possible side effects and efficacy of the plant remedies. Since TMPs play an important role in rural health care, this calls for training and education on such pertinent issues especially in poverty-stricken regions where the malaria transmission and disease burden remain high.

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LB conceived the research idea, collected field data, analyzed and interpreted the data as well as prepared the first draft of the manuscript. MO, FWO, SN, COO, GO and AL conceived the research idea and collected field data. All authors revised and efficiently contributed to improvement of drafts and approved the final manuscript.

Correspondence to Lydia Bunalema.

The study protocol was reviewed and received ethics approval from Makerere University School of Biomedical Sciences’ Research and Ethics Committee (#SBS-2022-213). Clearance to conduct the study in Uganda was granted by the Uganda National Council of Science and Technology (#NS431ES). A written informed consent was obtained from each traditional medicine practitioner prior to the interview. The study adhered to ethical principles in the Declaration of Helsinki (2013).

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The authors declare no competing interests.

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