endoparasite

Introduction

Herbal medicines have been used in human and animal medicine for centuries to treat parasitic diseases; few examples have been investigated for genuine anti-parasitic activity. In developing countries access to effective anthelmintic treatment for livestock is often limited by cost, availability and variable quality. Reports of resistance to benzimadazoles in ruminants in Ethiopia serve as a warning that anthelmintic resistance may also be an emerging problem [1,2]. In light of these issues there is increasing interest in plant remedies as alternatives to synthetic anthelmintics. This study used a participatory rural appraisal (PRA) to identify plants with potential anthelmintic activity in the Oromia region of Ethiopia; five plant extracts were shortlisted and tested for efficacy against cyathostomins using in vitro assays. Current attitudes to ethnoveterinary medicine were discussed.

Methods

Focus group discussions with 29 groups of donkey owners from the Oromia region of Ethiopia explored the use of plants to treat GI parasites in livestock. Current attitudes to herbal medicines were discussed and recorded using thematic analysis. Plants of interest were collected and identified at the National Herbarium, Addis Ababa, Ethiopia. Plants were shortlisted for in vitro tests based on four criteria; ranking in the PRA, supportive literature, no evidence of toxicity and availability. Hydro-alcoholic extraction of dried plant material from shortlisted species was performed. The efficacy of extracts was evaluated in the egg hatch assay (EHA) using cyathostomin eggs recovered from the faeces of donkeys at the Donkey Sanctuary, UK. Dose response curves were produced and ED-50 values calculated using probit analysis.

Results

The focus groups identified 21 plants used as anthelmintics in livestock. A general move away from traditional medicines in the younger generation was observed, although when asked if they would use plants in future many would consider this if they had been tested scientifically and were approved by professionals. The five plants shortlisted for in vitro analysis were Acacia nilotica, Cucumis prophetarum, Rumex abysinnicus, Vernonia amygdalinia and Withania somnifera. Three showed efficacy in the EHA; Acacia nilotica, Cucumis prophetarum and Rumex abysinnicus, with EC-50 values of 0.7, 1.1 and 1.3mg/ml respectively.

Conclusion

Three out of five of the plants identified in the PRA showed efficacy in vitro suggesting that plant remedies used by livestock owners in the Oromia region of Ethiopia may contain compounds with genuine anthelmintic activity. Evaluation of current attitudes suggests that plant remedies are not used unless there is no other option, but that they would be considered should scientific evidence of efficacy and safety be presented to them by animal health professionals [3]. It is therefore essential that a randomised controlled trial is used to verify whether in vitro anthelmintic activity can be translated in vivo and thus whether the plants identified in this study have potential as safe alternatives to synthetic anthelmintic drugs. This study has highlighted that local practices pertaining to the health of working equids are a rich source of information that may help to inform sustainable and effective treatment strategies in future.

In the developed world the control of equid gastrointestinal (GI) nematodes, in particular cyathostomins, is increasingly challenging due the threat of anthelmintic resistance. In developing countries such as Ethiopia despite high parasite burdens, access to genuine anthelmintic treatment is limited. In both situations there is a need for alternative treatment and management regimens for effective parasite control and consequently there has been increasing interest in the use of bioactive plant extracts (BPEs) [1]. This study identified candidate plants in the UK and Ethiopia and evaluated their in vitro efficacy against cyathostomin populations derived from donkeys. A participatory rural appraisal (PRA) approach was used to identify five ethnoveterinary medicines for use in donkeys in Ethiopia. In the UK three plants were identified following extensive review of literature citing efficacy against GI nematodes of other host species and two extracts were provided courtesy of Prof Jerzy Behnke, University of Nottingham. Hydro-alcoholic extraction of dried plant material was carried out for the eight extracts prior to reconstitution in both water and DMSO. Efficacy of each extract was evaluated by egg hatch assay (EHA) and larval migration assay (LMA) using eggs and larvae recovered from the faeces of donkeys at the Donkey Sanctuary, UK. Dose response curves were produced and ED-50 values were calculated using probit analysis. Of the five Ethiopian plant extracts tested, four showed efficacy in the EHA and/or LMA. The two most efficacious were Acacia nilotica and Rumex abyssinicus in the EHA with ED-50 values of 0.72mg/ml and 1.29mg/ml respectively. Of the five UK extracts four showed efficacy in the EHA and/or LMA. The two most efficacious were Carica papaya (papaya) in the LMA and Allium sativum (garlic) in the EHA with ED-50 values of 18.9µM and 0.65mg/ml respectively. The two BPEs most efficacious in vivo for Ethiopia and the UK are to be carried forward to in vivo trials. This study has demonstrated in vitro efficacy of nine plant extracts against cyathostomins. There is evidence in the literature that these plant extracts show efficacy both in vitro and in vivo against GI nematodes in other species. Therefore these results have identified potential alternatives to synthetic anthelmintics for the treatment of cyathostomins that require further investigation. [1] Githiori JB, Athanasiadou S, Thamsborg SM. Use of plants in novel approaches for control of gastrointestinal helminths in livestock with emphasis on small ruminants. Vet Para 2006;139, 308–320.

Cyathostomins, the predominant parasitic nematodes of equids, have developed varying degrees of resistance to all three classes of anthelmintic licensed for use in horses. It is essential that the effectiveness of alternative methods of control for these pathogens are quantified, including incorporating climatic data and the commonly advocated practice of removal of faeces from pasture. Here, we obtained monthly faecal worm egg counts (FWEC, n=4,460 individual counts) from 803 donkeys based at The Donkey Sanctuary (Devon, UK). The dataset also included age, sex, field, FWEC history and previous anthelmintic administrations in each individual, as well as the pasture hygiene management method applied in the field where the donkey was grazed. FWEC were analysed alongside local climatic data using a generalised linear mixed model to assess associations between these variables and each observed monthly FWEC. The preferred model was identified using a model selection algorithm based on penalised likelihoods, and associated a 2.1% decrease in FWEC per day with air frost two calendar months ago (p<0.001) and a 38% lower FWEC in groups with twice weekly manual faecal removal compared to those with no faecal removal (p=0.004). Other weather effects, both alone and as interaction terms with the average FWEC of the field were included in the model, alongside individual FWEC history with anthelmintic administration as interaction terms and date as a single term. Our study identifies factors that may be useful as part of on-going predictive modelling based methods of improving targeted selective therapy.

The Donkey Sanctuary is a British charitable organisation based in Sidmouth, Devon, England, which’s mission is to transform the quality of life for donkeys, mules and people worldwide through greater understanding, collaboration and support, and by promoting lasting, mutually life-enhancing relationships. The Donkey Sanctuary was founded in 1969 and registered as a charity in 1973 by Dr Elisabeth Svendsen. The Donkey Sanctuary has a total of seven farms in the UK including a reception farm for new arrivals where the study is based, a laboratory, pathologist and an specialized hospital. The Donkey Sanctuary currently looks after around 2.600 animals (in a total estimated UK census of 10.000 animals).

Animals are admitted into a quarantine Farm where they spend a minimun of 6 weeks to assess their health status including full coprological study. Donkey are relinquished or rescued by the charity and arrive from different origins: directly from a private owner, another organitation or hospital or one of the charity’s holding base located in different parts of the country. This animals wopuld have been previosly admitted into those centres and taken there due to biosecirity reasons or becuase transport could be in detriment of their health at that time. Animals that need urgent veterinary treatment would be sent to the closest equine hospital for treatment until consider fit to be transported.

Management of hundreds of animals and their pasture can be challenging from the parasitological point of view, especially if we tend into consideration that the majority of donkeys unlike horses would be asyntomathic despite having high parasite burdens. It is rare for donkeys to show signs such as diaorrhea, weight loss or a poor body condition that are more commonly found in the horse.

Working equines in Mexico are distributed throughout the territory, but the management practices and the health and welfare conditions differ widely between regions depending on people's customs and specific climate conditions. The Eastern coast of México has an important equine population used for work in rural production systems. Something that owners and animal workers are concerned about is how the gastrointestinal parasite burden affects the equines nutritional status and health. This is because parasite reinfestations are most likely to occur in hot, humid climates. However, there are few reliable data to support this and the lack of information makes it difficult to design treating strategies and extension activities to ensure the health and welfare of equines in these areas. To address this, a trial was designed to determine the prevalence of animals infected with gastrointestinal nematodes, the parasite burdens and their effects on the nutritional status and haematological values of working equines from a tropical area of Mexico. One hundred and twelve equines were randomly selected in five different villages of the area. One sample of faeces and one sample of blood (in a tube containing EDTA) were obtained from every animal. Gastrointestinal parasite burden using the McMaster technique, proportions of nematodes species present through a coproculture, packed cell volume, total plasma proteins, red blood cell count and white blood cell count, were measured. The nutritional status was assessed using body condition score. Data was analysed using descriptive statistics. All calculations were done per species (horses, donkeys and mules) and community (1, 2, 3, 4, and 5). Prevalence of infected equines was higher than 90%. The most common nematode species was Strongylus vulgaris. The parasite burden was low to moderate in horses and donkeys, higher in mules; however, it did not affect the body condition, nor the haematological values (P>0.05). Results suggest that in spite of the high prevalence and parasite burdens, equines involved in this trial are not being seriously affected, as shown by the body condition and haematological parameters.