Not published as conference proceedings

Donkeys are notorious for being a ‘stoical’ species. They typically do not overtly demonstrate symptoms of being in pain and discomfort. This masking behaviour is a key survival technique for many prey species. In acute scenarios, such as colic or acute musculoskeletal injury, there is an inherent risk that owners may not recognise the donkey is unwell or in discomfort until advanced stages, and vets may overlook the severity of the situation. For disease processes such as surgical colic and colitis, where prompt treatment is necessary to maximise a favourable outcome, a delay in recognition of a donkey in pain has a significant negative impact on prognosis. For chronic conditions, such as dental pathology, persistent ocular lesions and osteoarthritis, a donkey may not receive adequate analgesia and other treatment required if subtle symptoms of pain are not acknowledged. 

The ability to objectively identify evidence of pain is therefore of benefit to donkey welfare, not only in recognition of acute discomfort but also for monitoring of chronic conditions, assessing quality of life, post-operative pain management and intensive care cases. Owners, vets, nurses and other clinic support staff can all be trained in the use of simple pain scoring tools. Validated pain scoring systems have been developed for horses. However, as donkeys have unique behavioural tendencies and physiology, it stands to reason that tools designed for horses may not be directly transferable to use in donkeys. Furthermore, as different sources of pain, whether acute or chronic, may result in different signs, the accuracy of objective pain scoring does not fit with a ‘one size fits all’ approach. 

Facial expression based pain scales and composite pain scales have now been developed and evaluated for the scoring of acute pain in donkeys [1]. These scales used those developed for horses as their baseline, adjusting and adding further parameters using expert donkey knowledge. Results from this study indicate that acute head-related pain and colic pain are most reliably assessed using the facial pain scale, whilst acute orthopaedic pain and post-surgical castration pain are better assessed using the composite pain scale. In both scales, parameters are given a numerical score, with a higher number denoting greater evidence of pain. 

The composite pain score is a multifactorial scale based on 20 parameters, scored during observations over a 5-minute period. For example, a donkey that has no audible signs of pain is given a score of 0, a donkey with audible teeth grinding and moaning more than four times in the 5-minute observation period is given a score of 3. Scores are weighted and there is a maximum score of 60. The scale includes behavioural and physiological parameters as well as responses to stimuli. Those parameters that do not require a hands-on approach are assessed first, observing the donkey from a suitable distance to avoid any effect that disturbance due to human interaction may elicit. 

The facial pain scoring scale is a multifactorial scale based on 12 parameters, scored during observations over a 2-minute period. For example, ears in a normal position are scored 0, ears held in an abnormal position (hanging down or backwards) are scored 2. There is a maximum score of 24. 

Inter-observational reliability has been demonstrated for both scales. Whilst there are clear limitations, repeated use of the scales by trained observers provides an objective data set which is clinically applicable. Elevated scores should promote discussion of why that score is present – is the donkey in pain, why and what is the response to any treatment administered? For hospitalised patients, scores that are increasing are an immediate alert that a treatment plan may need adjusting. 

Work is underway to evaluate scoring systems for assessment of chronic pain in donkeys. The availability of validated scales will be welcome to those vets and owners caring for not only geriatric donkeys, but any donkey with a chronic health condition. In a study [2], researchers constructed a chronic pain score, which is an amalgamation of composite and facial pain scoring scales. The study demonstrated good inter-observational reliability between well trained, previously inexperienced observers. The choice to amalgamate two scoring scales arose because pilot work indicated that donkeys experiencing pain from chronic conditions may show changes in facial expressions akin to those found in donkeys in acute pain, whilst demonstrating behavioural changes that are quantifiable using the composite pain scale. Validation of this chronic pain scale will be of major benefit to those monitoring the health and welfare of any donkey living with a chronic health condition. It is hoped that the regular use of chronic pain scale scoring will assist treatment monitoring and will be a welcome inclusion to a quality of life assessment toolkit. 

References 

1. van Dierendonck, M.C., Burden, F.A., Rickards, K. and van Loon, J.P.A.M. (2020) Monitoring acute pain in donkeys with the Equine Utrecht University Scale for Donkeys Composite Pain Assessment (EQUUSDONKEY-COMPASS) and the Equine Utrecht University Scale for Donkey Facial Assessment of Pain (EQUUS-DONKEY-FAP). Animals 10(2), 354. 

2. van Loon, J.P.A.M., de Grauw, J.C., Burden, F., Vos, K.J., Bardelmeijer, L.H. and Rickards, K. (2021) Objective assessment of chronic pain in donkeys using the donkey chronic pain scale (DCPS): A scale-construction study. Vet. J. 267, 105580.

There are significant numbers of donkeys kept as companion animals, both in the UK and abroad. Like their horse and pony compatriots, many kept donkeys are geriatric. Additionally, obesity is a common problem, irrespective of age. Diagnosis and management of endocrine disease in donkeys is challenging as many of the available tests for horses have not been specifically validated in donkeys. Furthermore, endocrinopathic laminitis in the donkey is not infrequently subclinical. The term ‘subclinical,’ is perhaps inappropriate, for the lack of clinical signs may not correlate with the severity of the laminitis episode but instead be a feature of the donkey’s notoriously stoic behaviour with respect to pain.

As a species, the donkey has evolved to be extremely energy efficient, with an inherent ability to maintain good body condition on lower energy diets. They have a slower intestinal transit time and greater efficiency of fibre digestion than the horse [1]. Donkeys appear able to accumulate adipose tissue with ease. Whilst these innate traits serve the working donkey or those kept in harsh environments where food resources are scarce well, they predispose the sedentary donkey to obesity, dyslipidaemias, insulin dysregulation and other metabolic disorders.

Donkey, or asinine, metabolic syndrome is increasingly recognised by equine veterinary practitioners. Clear and precise definitions are lacking and currently rely on extrapolations from equine metabolic syndrome. The clinician presented with an obese donkey should be suspicious of underlying metabolic derangements. The donkey may be generally obese, or have defined regional adiposity, with deposits along the neck, dorsum and rump being common. There are usually substantial subcutaneous fat deposits on the ventral abdomen in obese donkeys. Awareness of the obese donkey may only arise when the otherwise healthy donkey is presented for routine preventative care, such as vaccination or dental care. This provides an ideal opportunity to discuss the donkey’s body condition and diet, with the intention to reduce development of metabolic disease. Initial clinical assessment must include an evaluation of any indicators of laminitis, whether subtle or overt. The donkey that is described as unwilling to walk may actually be in discomfort rather than being unused to handling. It is imperative that provided diets are appropriate for the donkey’s life stage. For the adult, healthy donkey, with good molar function, the majority of forage intake should be provided by straw, with hay/haylage or restricted grazing making up the remainder of the diet. Owners should be advised to aim for straw to provide 75% of intake in summer and 50% in winter. Supplementation with a vitamin and mineral balancer is recommended. The conscientious owner may be willing to have their forage sugar content analysed, to further guide dietary management.

If a donkey remains obese, despite sufficient time and appropriate diet for expected weight loss to ensue, further investigation for metabolic disease should be undertaken. Basal insulin concentrations may be elevated in obese donkeys. The established reference range at The Donkey Sanctuary for a non-fasted insulin sample in the adult donkey is 0-15.1 uIU/ml (TOSOH AIA, using two-site immunoenzymometric serum assay). As for horses, a normal insulin concentration does not rule out insulin dysregulation and dynamic tests are recommended for further investigation. Protocols have been developed for donkeys, with intravenous glucose tolerance test, combined glucose-insulin test and oral glucose tolerance tests described in the literature [2] but insulin cut-off values for these tests have not been validated for donkeys. In the author’s clinic, the oral glucose tolerance test with corn syrup is used as this provides an accessible and practical dynamic test. The major limitation being that the protocol used is that developed for horses and may not be directly transferable to donkeys and, again, there is no validated insulin cut-off value. Consequently, diagnosis of asinine metabolic syndrome is currently made based upon combinations of clinical observations, poor weight loss despite appropriate diet, evidence of hyperinsulinaemia or insulin dysregulation and history of laminitis episodes.

Management of asinine metabolic syndrome is as challenging as the diagnosis. Many owners struggle to appropriately diet their donkey, particularly if any companion is not obese and/or has different dietary requirements. It is now widely understood that donkeys form strong bonds with their companions and can become distressed and at risk of hyperlipaemia if separated. However, for short periods if one donkey needs supplementary feed companions can be kept in sight of each other, yet physically separated by a fence or stable door. Owners should also try to encourage their donkeys to exercise, which is admittedly no mean feat. Turn out onto a bare pasture, which donkeys can explore and exercise within, is likely to carry more benefit than stabling a donkey away from rich grass pastures. If a donkey is accepting of a head collar and being led, many owners enjoy taking their animals for short walks. Providing enrichment activities that encourage the donkey to be mobile and explore are also helpful.

It goes without saying that exercise should not be advised until active laminitis has been ruled out. An association between obesity, insulin dysregulation and recurrent laminitis in donkeys has been reported but in a recent cross-sectional study of 707 donkeys in the UK [3], the presence of basal hyperinsulinaemia or PPID (indicated by seasonally adjusted elevations in ACTH) was not associated with increased odds of laminitis. However, this study acknowledged the lack of validated dynamic testing for either PPID or AMS and the potential errors in classification of cases. In the absence of definitive knowledge, clinicians should err on the side of caution and be alert to the potential for endocrinopathic laminitis. Management of laminitis in the donkey has been covered elsewhere [4].

The use of medication to treat asinine metabolic syndrome has not been extensively evaluated. As for horses, therapeutic protocols should only be used as an adjunct to dietary and exercise management. The use of levothyroxine in the donkey at standard equine doses has been reported [2]. Studies are needed to assess the safety and efficacy of ertugliflozin in the donkey, alongside any other medication proposed for treatment of metabolic syndrome in the horse.

References:

[1] Thiemann AK, Sullivan RJE. (2019). Gastrointestinal Disorders of Donkeys and Mules. Vet Clin North Am Equine Pract 35(3):419-432

[2] Mendoza FJ, Toribio RE, Perez-Ecija A. (2019) Metabolic and Endocrine Disorders in Donkeys. Vet Clin North Am Equine Pract 35(3):399-417

[3] Menzies-Gow NJ, Wakeel F, Little H, Buil J, Rickards K. (2021). Cross-sectional study to identify the prevalence of and factors associated with laminitis in UK donkeys. Equine Vet J. 54(4):757-765

[4] Thiemann A.K, Buil J, Rickards K, Sullivan R.J (2021). A review of laminitis in the donkey. Equine Vet Educ 34(10): 553-560

Colitis and typhlitis are diagnosed in donkey populations. Precise clinical presentations vary, depending on whether acute or chronic, a single individual or a number of animals in a group outbreak situation. The common feature, irrespective of circumstance, is that of a dull donkey and consequently, in the initial stages can be challenging to differentiate from the many other potential causes of dullness. Typically, donkeys present as inappetent, or only picking at feed, behaviour is depressed and they may distance themselves from companions. It is vital that owners and vets are aware that this likely constitutes a medical emergency and a clinical exam should be performed without delay. In acute cases, the donkey may be tachycardic, tachypnoeic, pyrexic, have congested mucous membranes with delayed capillary refill time and significantly reduced borborygmi. However, many cases can initially present with relatively normal parameters, yet progress to a peracute presentation and become moribund within hours. A salient point is the lack of diarrhoea in most donkeys with colitis. Ventral or limb oedema is not a consistent finding. Overt demonstrations of abdominal pain, such as rolling or kicking at the abdomen are uncommon in donkeys but if present are likely to indicate severe pain.

Thorough history taking is essential to guide diagnosis. Risk factors for colitis in donkeys include stressors such as recent movement, management or dietary change, alongside ingestion of toxic feed substances, infectious aetiologies, endoparasite infestation and recent anthelmintic or antimicrobial use. Right dorsal colitis does not appear to be common in donkeys, irrespective of short or long-term NSAID treatment at standard maintenance doses. Dysbiosis, secondary to any of the previously listed stressors, may be a significant factor in the development of colitis. Toxic and infectious causes are higher up the differential list in an outbreak situation. In chronic cases, insidious weight loss may be noted and intermittent episodes of dullness and colic.

Common differentials include hyperlipaemia, hepatopathies, other forms of colic including impaction or sand and any systemic inflammatory process causing pain and discomfort. Co-morbidities of any of these with typhlocolitis are not uncommon and can complicate diagnosis and treatment.

In addition to the basic clinical exam, vets should perform a rectal examination where possible. The aim is two-fold – to establish the presence of intestinal distension, displacement or impaction and to obtain a faecal sample for subsequent analysis. Testing for Salmonella, C.difficile and C.perfringens (including toxins) and Coronavirus alongside worm egg counts are recommended. Additional tests may be advised for foals. A blood sample should be obtained for routine biochemistry and haematology alongside inflammatory markers and, essentially, serum triglyceride concentrations. Feed samples can be collected for analysis if ingested toxins are suspected. Passage of a nasogastric tube is useful to assess for the presence of reflux. Transcutaneous ultrasonographic abdominal examination is ideal for further assessment, including measurement of intestinal wall thickness but may not be available in the field. Owners should be counselled as to the guarded prognosis and potential costs involved. Referral to a clinic setting should be considered for donkeys in need of intensive care but the risks of stress induced by movement will need to be taken into account.

Initial treatment in an ambulatory setting and whilst awaiting results of initial diagnostics centres on stabilising the donkey, restoring fluid and energy deficits and relieving pain. Unless there is gastric reflux and/or complete ileus, if the donkey is not voluntarily eating, nasogastric intubation of a water/electrolyte combination (the average standard size donkey stomach will hold approximately 3 litres of fluid) with dextrose or glucose powder and oat-based cereal (fine milled porridge cereals) should be given. If an infectious or toxic aetiology is suspected, enteral adsorbants such as smectites may be given down the stomach tube. Severely hypovolemic donkeys, or those with total ileus may require intravenous fluid boluses in the field before being stable enough to transport to a clinic. Analgesia is essential, usually flunixin meglumine at 1.1mg/bwt BID i.v providing the donkey is sufficiently hydrated, otherwise anti-endotoxic doses can be given and/or paracetamol at 20-25mg/kg p.o BID. Alpha-2 agonists and opioids may be required for multimodal analgesia, again extrapolating from standard equine doses. Use of corticosteroids in the acute phase is often debated and should be subject to a risk benefit analysis -the merits of potent anti-inflammatory activity versus worsening of systemic infection for example. Decision making for administration of other medications, such as anthelmintics, antimicrobials, gastroprotectants, pro-kinetics and other anti-inflammatory and anti-endotoxin therapies follow the same rationale as for horses and there are no peer-reviewed donkey specific guidelines. In our Donkey Sanctuary population, post mortem data of non-survivors indicates that very sick donkeys with colitis may be predisposed to gastric glandular ulceration.

If the donkey is worsening or failing to respond to treatment and intensive care is an option then remember to hospitalise companions with the patient, to reduce further distress. As for horses, strict biosecurity measures should be adhered to until infectious causes can be ruled out. In a donkey with severe hypoalbuminaemia, colloid fluid therapy may be indicated. Severe mural oedema has been identified at post-mortem in the intestines of donkeys subjected to aggressive crystalloid therapy and this likely worsens ileus. Other conspicuous findings of non-survivors in our population at post-mortem have included focal or diffuse severe necrotisation and encysted cyathostome burdens

Vets and owners should establish clear end points for treatment, if the donkey is responding poorly. Repeated transabdominal ultrasound, blood work including lactate quantification and results of abdominocentesis may be used to guide decision making. There are donkey specific biochemical and haematology parameters [1] but normal intestinal wall thicknesses

and lactate reference ranges have not been established. For patients that are responding favourably, provision of their normal diet and good nursing care are essential for recovery. Like horses, donkey colitis patients may be prone to laminitis. Transfaunation using faeces from another donkey is a valid consideration in the recovering patient. Note that the donkey gut microbiome is not the same as that of the horse [2] and therefore horse-specific probiotics are unsuitable.

References:

[1] The Donkey Sanctuary (2020). Parameters for Haematology and Biochemistry. Available at: https://www.thedonkeysanctuary.org.uk/research/sites/uk/files/2020-02/parameters-for-haematology-and-biochemistry.pdf

[2] Edwards, J.E., Schennink, A., Burden, F. Long S., van Doorn D.A., Pellikaan W.F., Dijkstra J., Saccenti E., Smidt H.. (2020) Domesticated equine species and their derived hybrids differ in their fecal microbiota. Anim Microbiome 2(1):8

Introduction: This report highlights the need to consider liver fluke as a differential for liver disease in the donkey and the need for correct faecal sampling and treatment.

History and Clinical signs: An 11 year old donkey gelding was referred to investigate ongoing weight loss, elevated liver enzymes, hypoalbuminemia and eosinophilia. The donkey had received treatment for suspected colitis with moxidectin and prednisolone. The feed had been increased and dental correction performed as necessary. A routine strongyle faecal egg count had 0 epg. 1 week prior to referral, the donkey had developed pyrexia and dullness, which responded to Flunixin.

Examination and Diagnostic findings: The donkey was in BCS 2 /5.  T 38, HR 64, RR 20, gut sounds and rectal examination were unremarkable.  A routine oral glucose absorption test was normal.  The only significant finding on ultrasound examination of the abdomen were changes in the liver parenchyma; large numbers of abnormally dilated bile ducts and blood vessels disrupted the liver architecture.  A liver biopsy was not performed due to concerns about the risk of penetrating a vessel.

A full examination of the donkey’s parasite history revealed that there was an episode  of liver fluke (Fasciola hepatica) noted 1 year prior to referral  that had been treated with Triclabendazole at 18mg/kg oral. Subsequent tests had given two negative faecal egg tests for fluke at intervals of 16 and 35 days.

A repeat faecal examination was performed testing for liver fluke, which proved positive at the time of examination. 

Treatment plan:  Treatment was initiated with Closantel orally at 20mg/kg repeated after 8 weeks. A balanced diet supplemented by a vitamin /mineral supplement was provided.

Outcome: Subsequent faecal tests for fluke over the following 1 year have remained negative. Liver values and haematology returned to normal within 15 days. A repeat Ultrasound examination after 3 months showed the vasculature returned to normal size and the parenchyma appeared to be grossly normal. The donkey gained 23 kg in weight over the following 48 days and was scored at  BCS 3/5.

Discussion: Fasciola hepatica (Liver fluke) infection is recognised in horses and donkeys, but few reports detail individual cases. The infection prevalence in UK donkeys based on faecal analysis has been variably stated as 4-8% (Matthews and Burden, 2013), and 9% in a recent study of 596 donkeys (Barrio pers. comm 2019).  Howell et al. 2019 described a sero-prevalance of Fasciola based on a horse specific ELISA at 8.7% in a survey of 183 UK horses.

Clinical signs and liver pathology are usually considered  to be mild.

Fox et al. (2011) describe an increasing infection risk with liver fluke across the UK due to climate change resulting in wetter, warmer weather that encourages the survival and development of the free living stage of the parasite and  intermediate snail host. Equines are at risk if they co graze pastures with ruminants that carry the parasite.

There are no licensed products for treatment of liver fluke in equines and there is reported resistance to some products. After treatment repeat sampling is required and a further flukicide treatment may be needed.

References:

Fox, N.J., White, P.C., McLean, C.J., Marion, G., Evans, A. and Hutchings M.R. (2011) Predicting impacts if climate change on Fasciola hepatica risk PLoSOne Jan 10; 6 (1) 0. e16126 doi.10.1371/journal.pone.0016126.

Howell, A.K., Malalana, F., Beesley, N.J., Hodgkinson, J.E., Rhodes, H., Sekiya, M., Archer, D., Clough, H.E., Gilmore, P., and Williams, D.J.L.( 2019) Fasciola hepatica in UK horses . Equine Vet J. https://doi.org/10.1111/evj.13149

Matthews, J.B. and Burden F.A (2013) Common helminth infections of donkeys and their control in temperate climates.  Equine Vet. Educ 25 (9) 461-467

Anthelmintic resistance is a growing problem in both the developed and developing world; of most concern is the level of resistance detected against the potent macrocylic lactone (ML) anthelmintics. To identify and target a common mechanism of resistance to anthelmintics would allow potential modification of existing drugs, and may even enable the prediction and prevention of the development of resistance to novel drugs. There is a growing body of evidence that P-glycoproteins (P-gps) are involved in resistance to the MLs in many parasitic nematodes of humans and veterinary species (Ardelli et al, 2011). P-gps belong to class two of the ATP binding cassette (ABC) transporter protein superfamily; they are responsible for the active removal of xenobiotic compounds from cells. The cyathostomins are gastrointestinal nematodes of equids that cause significant pathology. Recently resistance to MLs has been described in cyathostomins (Molento et al, 2008), its mechanisms have not yet been elucidated.

Anthelmintic resistance is a major veterinary and public health issue globally, of most concern is the level of resistance to the macrocyclic lactones. Recent studies have identified a role in resistance for the ATP binding cassette (ABC) drug transporters, P-glycoproteins (P-gps). This study demonstrates the effect of the P-gp inhibitor ketoconazole on the efficacy of ivermectin (IVM) against equid cyathostomin larvae using the larval migration inhibition test (LMIT). Third stage cyathostomin larvae (L3) were cultured from two populations; 1) with recent history of IVM resistance in vivo and 2) naive to anthelmintic exposure. The sensitivity to IVM in each group (n=8) was characterised using the LMIT. The IVM LMIT was repeated for each sample with and without the addition of 10µM ketoconazole. Probit analysis was performed on grouped data from each population to give LC-50 values. The LC-50 value for IVM in Populations 1 and 2 was 4.9 and 2.4µg/ml respectively indicating that Population 1 has a resistant phenotype in comparison to Population 2. Addition of 10µM ketoconazole to IVM in Population 1 caused a drop in LC-50 value from 5.8 to 1.6µg/ml. In Population 2 the effect of the addition of ketoconazole was negligible (1.1 to 0.9µg/ml). This study demonstrates that the P-gp inhibitor ketoconazole causes reversion to a sensitive phenotype in IVM-resistant cyathostomins, inferring that P-gps play a role in their resistance to IVM. This work will be corroborated by investigation into P-gp genes and their expression in cyathostomins.

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.