General knowledge of traditional medicines (TM) used as anthelmintics was high in this study, with all groups naming plants used in livestock species generally and 22/29 groups specifically naming plants for use in donkeys. In total, 21 different plant preparations were named for use in livestock. This is in line with previous reports of the wide use of TM’s in developing countries, often attributable to their accessibility and affordability. In Africa, up to 80% of the population use TM to help meet their health care needs [14
] and natural plant-derived products have been known for many decades to possess anthelmintic properties [28
]. However, many of the previous studies report the use of plant-based anthelmintics for humans [15
] or for ruminants, pigs and poultry livestock [16
]. Further, the majority of evidence for plant-based anthelmintics is in the form of observations rather than controlled studies [28
]. To the authors’ knowledge there are no published studies of the use of these materials in equids, despite their immense value to communities in developing countries [29
Of all the plants named by participants, V. amygdalina,
was the highest ranked plant for efficacy against gastrointestinal parasites. It is a perennial shrub that is abundant in tropical Africa, including the regions of interest in Ethiopia. It has been used for centuries by humans for the treatment of multiple ailments, and recent research has identified that it may have a number of health benefits such as antimalarial, antimicrobial, antifungal, antitumor, and anti-diabetic effects [30
]. There have also been several studies demonstrating its potential as an anthelmintic. For example; a study in puppies in Nigeria demonstrated a significant anthelmintic effect of the aqueous extract of V. amygdalina
leaves against Toxocara canis
and Ancyclostoma caninum
] and the aqueous extract of V. amygdalina
leaves has been shown to reduce faecal egg counts in calves infected with mixed gastrointestinal nematodes by 59.5% [32
]. One study investigated the bio-activity of a related species, V. anthelmintica
and demonstrated a faecal egg count reduction of 73.9% when sheep were administered 3 g/kg of crude aqueous extract of the seeds [33
]. Hagenia abyssinica
, also ranked highly, has well known anti-cestodal properties [15
] and was reportedly frequently used to treat human infection with tapeworm. Although H. abyssinica
and V. amygdalina
were the most frequently named plants here, there were important issues raised about the potential side effects of these two remedies, which ranged in severity and reportedly could include death of the animal if not used correctly. Negative side effects in humans have also been reported with the use of H. abyssinica.
The most common of these are diarrhoea and abdominal pain. Blindness, changes to the central nervous system, abortion and death, have also been associated with ingestion of a high dose of H. abyssinica
Amongst the other highly ranked plants, there are reports in the literature of anthelmintic activities, although the evidence is not as compelling as for V. amygdalina. Withania somnifera
has been identified in previous surveys of ethnoveterinary plants [36
] and an in vitro
study assessing the effect of aqueous extracts of this plant against Pheretima posthuma
(earthworm) showed a significant effect [37
]. Cucumis prophetarum
has also been identified in previous surveys [38
]. There are no studies assessing the specific anthelmintic activity of this plant species, however plants in the same family, Cucurbitaceae,
have been used for centuries as taenicidals and a recent study showed a related species Cucurbita moschata
to be effective against nematodes in vitro
]. The use of E. schimperi
and evidence for efficacy in vivo
and in vitro
is restricted to taenicidal activity [41
]. The informant consensus of plants named in this study was relatively high (close to 1) and indicates good homogeneity of cultural knowledge on the use of plants in the treatment of gastrointestinal parasitic disease suggesting that knowledge is shared between communities. This score indicates that relatively few different taxa of plants were reported by the different groups which may suggest that some of these plants could be efficacious. It was not possible to identify the species of plant that was referred to as ‘Abdul salim’ as the plant itself did not grow in the areas where the study was conducted and, therefore samples could not be collected for specific identification.
The most frequently reported signs associated with gastrointestinal parasites in donkeys were observation of worms in the faeces and loss of body condition. This may indicate a relatively high burden of parasitism prior to any treatment being given. Indeed, previous studies have reported a high prevalence of parasitism within the donkey population in Ethiopia [1
]. ‘Loss of body condition’ in a donkey is not necessarily pathognomonic for helminthiasis and it was acknowledged by participants that the same plant based preparations were often used for multiple clinical presentations. This may result in some mis-classification bias within this study however ongoing work is investigating a selected number of highly ranked plants for their bio-activity against Cyathostome spp. in-vitro
The preparation methods described were relatively straight forward and often used leaves or whole plants crushed and mixed with water to make an infusion which was then administered. This is akin to preparation methods reported in other ethnoveterinary medicine studies [42
]. However between groups there was a variety of methods of preparation and measures of ingredients used resulting in limited useful information relating to how these plants are prepared for use in donkeys. It may be that each family group has slightly different preparation methods or may be indicative of a certain amount of ‘trial and error’ involved when extending the use of plant-based medicines traditionally established for use in cattle/small ruminants to donkeys as was reported within this study.
There was no report of prophylactic dosing with anthelmintics among donkeys, and animals were treated based on the recognition of clinical signs. This may, in part, be due to socio-economic pressures influencing the frequency with which medical interventions are sought for donkeys. Further research is required in order to describe how socio-economic and other contextual determinants drive owner decision making regarding preventive health care, particularly given the large population of donkeys within these communities.
Although traditional medicines continue to play a significant role within the community health care system in Ethiopia [44
] there appears to be a general shift away from traditional remedies for anthelmintic treatment in this study area due to the availability of clinical services. The perception was that clinics provide a more accurate diagnosis and dosage of medicines and that these represent a modernisation and improvement in practice and had fewer side effects. This finding was similar to that reported by Bussman et al.
in 2011 [45
]. It appears that the younger generation in particular are not as interested in learning about and retaining the knowledge relating to plant-based medicines. Others have shown that ethnoveterinary knowledge is greater in older informants and those with lower education levels [46
]. As knowledge of plant-based remedies is passed on through word of mouth and generally stays within family lines, it may be prudent to collect further information for documentation of additional plant-based remedies for use in veterinary species before this information disappears.
There appears to be a widespread practice of drenching donkeys with plant-based remedies for treating many conditions and this poses a significant risk of aspiration pneumonia (cases are regularly reported to the Donkey Sanctuary clinic, pers comm.). Additionally, chemical anthelmintics were often reported to be in tablet form which were mixed with water and drenched. Practical alternatives for these problems need to be developed and communicated in order to reduce this risk.
In many cases, people were unable to name the chemical anthelmintic product they used but those that did spoke of “Albendazole”. It is unknown whether the helminth population is susceptible to the treatments available in these regions and whether the method, and dose, given to donkeys is sufficient for control. In other parts of the world a range of anthelmintics (benzimidazoles, tetrahydropyrimidines and macrocyclic lactones) have been widely used against equine gastrointestinal nematodes for many years; however, anthelmintic resistance is present in many populations in developed countries and threatens sustainable control in future [11
]. Although the degree of anthelmintic resistance has not yet been established in nematodes of donkeys or horses in Ethiopia, continued use of a limited range of chemical anthelmintics, combined with the effects of under or inappropriate dosing, or inferior quality generic products, are all risk factors for promoting anthelmintic resistance. Benzimidazole resistance in small ruminant nematodes has already been demonstrated in Ethiopia [47
Some potential biases may have been introduced due to the roles of the researchers as veterinarians and animal health assistants. This may have influenced the participants’ discussions to favour clinical medicine; however, it was considered that a good range of views relating to the benefits and disadvantages of both clinic-based medicine and traditional medicine were obtained so we consider this bias to be minimal. The timing of the study was at the beginning of the wet season and consequently, in some regions there was little vegetation evident. This may result in an amount of recall bias among participants leading to some ‘out of season’ plants being omitted from the discussion however, we asked the question about plant use in general and given that people recalled annual trends in plant use it is anticipated that this source of bias would be minimal. There may have been some selection bias with more knowledgeable participants selected by the DA’s who were influential in selecting the participants; however, they were briefed on which participants to recruit and it is believed that we communicated with a broad range of donkey owners.
Further research is required to determine helminth sensitivity to anthelmintic preparations commonly used in these regions. Additionally, further work is warranted to investigate the potential use of plant-based preparations as anthelmintics in donkeys and other species.
Aside from investigating options to overcome the threat of resistance problems, there are several other advantages of using plant-based anthelmintics in developing countries including cost, availability and environmental aspects [28