United Kingdom

Preliminary investigation into relationships between donkey and horse skull morphology and brain morphology

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Date presented: 
Thursday 23 November 2017
Abstract

All horses and donkeys belong to the genus Equus but anatomical and behavioural differences exist among species. Equus caballus displays distinctive conformational attributes among breeds provisionally related to ganglion cell distribution and skull and brain morphology. Equus asinus shows less variation in skull shape, and little is known about brain organisation. The current research compared skull and brain morphology between horses and donkeys. Skulls of Equus caballus, primarily of Standardbred type (N=14) and Equus asinus (N=16), were obtained postmortem. All animals had been humanely euthanised for reasons unrelated to this study. Heads were sectioned sagitally along the midline and photographed for measurement of various skull structures using Image J software. Measurements included: skull index (SI)=zygomatic width*100/skull length; cranial index (CI)=cranial width*100/cranial length; nasal index (NI)=zygomatic width*100/nasal length; cranial profile index (CPI)=rectangular area bordered by an 80mm line from orbital notch and occiput; nasal profile index (NPI)= rectangular area bordered by 80mm line from orbital notch and tip of nasal bone; olfactory lobe area (OLA); OL pitch [angle between hard palate and the OL axis]; brain pitch [angle between longitudinal axis of the cerebral hemispheres and the hard palate]; and whorl location (WL) [distance of OL from the level of the forehead whorl]. A General Linear Model determined the main effect of species with Sidak’s multiple comparisons of species’ differences among the various measurements. Donkeys had shorter heads (cranial lengths) than horses (19.7±2.5 vs 23.6±1.4cm respectively; F1,23=51.49, P<0.0002). Donkeys also had smaller cranial widths (13±3.4cm; F1,17=15.91, P<0.001) and mandibular depths (24±2.6cm; F1,21=13.05, P<0.002) than horses (19±0.8 and 27.2±1.1cm, respectively). There was no species difference in SI, ZI, or NI (P>0.40), but donkeys tended to have a smaller CI than horses (F1,17=3.59, P<0.08). Similarly, donkeys had a smaller CPI than horses (F1,21=7.54, P<0.034), but there was no difference in NPI (F1,21=0.05, P>0.83). Donkeys also had a smaller OLA than horses (1.4±0.3 vs 2.3±1.3cm2 respectively; F1,13=4.96, P<0.05) although there was no difference in brain pitch (F1,23=0.69, P>0.43). The greatest difference was seen in WL, which corresponded to the level of the OL in horses, but was extremely rostral in donkeys (F1,21=24.29, P<0.0001). These results show clear differentiation in skull morphology between horses and donkeys which may be linked to behaviour. This may be useful in validating different approaches in the training and management of horses versus donkeys.

Lay person message: Horses demonstrate specific behaviours which may be associated with skull shape, although nothing is known about this relationship in donkeys. This pilot study has shown that donkeys have smaller brain cases and olfactory lobes than Standardbred horses. Donkeys’ facial whorls are located lower down the face while horses’ are in close proximity to the brain’s olfactory lobe. Clarifying differences between horses and donkeys is crucial to understanding species-specific behavioural responses and providing appropriate management and training practices.

P-glycoproteins play a role in ivermectin resistance in cyathostomins

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Laura Peachey, Gina L. Pinchbeck, Jacqui. B. Matthews, Faith A. Burden, A. Lespine, G. von Samson-Himmelstjerna, J. Krucken, Jane Hodgkinson. October 2017. P-glycoproteins play a role in ivermectin resistance in cyathostomins. International Journal for Parasitology: Drugs and Drug Resistance. 7:3.

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Publication date: 
25 October 2017
Volume: 
7
Issue: 
3
Abstract

Anthelmintic resistance is a global problem that threatens sustainable control of the equine gastrointestinal cyathostomins (Phylum Nematoda; Superfamily Strongyloidea). Of the three novel anthelmintic classes that have reached the veterinary market in the last decade, none are currently licenced in horses, hence current control regimens focus on prolonging the useful lifespan of licenced anthelmintics. This approach would be facilitated by knowledge of the resistance mechanisms to the most widely used anthelmintics, the macrocyclic lactones (ML). There are no data regarding resistance mechanisms to MLs in cyathostomins, although in other parasitic nematodes, the ABC transporters, P-glycoproteins (P-gps), have been implicated in playing an important role. Here, we tested the hypothesis that P-gps are, at least in part, responsible for reduced sensitivity to the ML ivermectin (IVM) in cyathostomins; first, by measuring transcript levels of pgp-9 in IVM resistant versus IVM sensitive third stage larvae (L3) pre-and post-IVM exposure in vitro. We then tested the effect of a range of P-gp inhibitors on the effect of IVM against the same populations of L3 using the in vitro larval development test (LDT) and larval migration inhibition test (LMIT). We demonstrated that, not only was pgp-9 transcription significantly increased in IVM resistant compared to IVM sensitive L3 after anthelmintic exposure (p < 0.001), but inhibition of P-gp activity significantly increased sensitivity of the larvae to IVM in vitro, an effect only observed in the IVM resistant larvae in the LMIT. These data strongly implicate a role for P-gps in IVM resistance in cyathostomins. Importantly, this raises the possibility that P-gp inhibitor-IVM combination treatments might be used in vivo to increase the effectiveness of IVM against cyathostomins in Equidae.

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Endocardial Peripheral Nerve Sheath Tumour with Features of a Benign Schwannoma in a Donkey

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Georgios Paraschou, Alejandro Suarez-Bonnet, Vicky S. Grove, S. L. Priestnall. November 2017. Endocardial Peripheral Nerve Sheath Tumour with Features of a Benign Schwannoma in a Donkey. Journal of Comparative Pathology. 157:4. 280-283.

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Publication date: 
1 November 2017
Volume: 
157
Issue: 
4
Page numbers: 
280-283
DOI number: 
10.1016
Abstract

A peripheral nerve sheath tumour, with features of a benign schwannoma and arising from the endocardium of the right ventricle, was found incidentally during routine post-mortem examination of a 28-year-old gelding donkey. Macroscopically, five round to oval, white to grey and red, firm masses, firmly attached to the endocardium were identified. Microscopically, the endocardium and adjacent subendocardium were infiltrated by a variably demarcated, non-encapsulated mesenchymal neoplasm with features of a benign schwannoma, including concurrent presence of Antoni A and Antoni B areas, nuclear palisading, neoplastic cells with enlarged bizarre nuclei (‘ancient change’) and the formation of Verocay-like bodies. Immunohistochemically, the tumour cells were variably strongly positive for expression of S100 and glial fibrillary acidic protein. This is the first cardiac tumour reported in a donkey and is macroscopically, histologically and immunohistochemically similar to endocardial schwannoma occurring in Wistar rats.

This article was published online prior to print.

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Training Compassionate Vets for Calmer Donkeys

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Date presented: 
Tuesday 3 October 2017
Abstract

INTRODUCTION
Working donkeys and mules often require veterinary intervention for a variety of clinical problems. It is crucial that vets, animal health professionals and other equine professionals have a sound knowledge of donkey and mule behaviour to enable them to assess the animals and provide treatment in a species-accurate, humane and compassionate way.
HANDLING TECHNIQUES AFFECT EQUINE WELFARE
The way in which donkeys and mules are handled can affect their welfare since quality of life is measured not only by physiological factors but also by emotional and affective states (1). Negative interactions can contribute to the development of fearful behavioural responses which can persist for a long time after the interaction takes place. Correct application of behaviour modification techniques can positively develop the human-animal bond and help the animal to remain calm during required veterinary procedures, often meaning that painful methods of restraint are not required. Simple techniques for approaching equines, taking rectal temperatures, using stethoscopes and appropriate restraint can, and should, be used to reduce stress for all aspects of a veterinary examination and treatment.
HUMAN BODY LANGUAGE
Correct approach to an equine patient is vital to minimise stress and to prevent a flight response. Equines are sensitive animals who can detect very subtle body language signals. The body language and behaviour of the veterinary surgeon and animal handler can influence the animal’s behaviour; approach with calm, relaxed body language and allow the animal the opportunity to investigate you.
A relaxed, calm approach:
• Rounded shoulders
• Relaxed muscle tone, gentle movements
• No direct eye contact
• Indirect approach from the animal’s shoulder
• Allowing time for the animal to investigate
PRACTICAL APPLICATION
Using a stethoscope
• Allow the animal the chance to have a look at your equipment
• Introduce the stethoscope to the animal’s body gradually, starting in an area that is not too sensitive
• Stroke or scratch the animal to provide reassurance as you work
Taking a rectal temperature
• Help the animal to relax by approaching steadily from the side
• Scratch the animal along his body and on either side of his tail to encourage relaxation
• Do some gentle lifts of the tail before lifting to insert the thermometer
LESS IS MORE
When considering methods of restraint for veterinary examination consider that often ‘less is more’. Distressed and fearful animals are more likely to display erratic behaviours and become more likely to cause injury to themselves or their handlers (2). If calm, consistent handling is not sufficient to keep an equine calm during examination, and restraint is required, the least invasive and minimally aversive restraint options, such as a head hold or the raising of one leg, should be attempted first.
Ear twitches should not be used on equines; a recent study (3) found a significant increase in sympathetic tone and salivary cortisol levels when an ear twitch is applied and it also led to the development of avoidance behaviour indicating the aversive-ness of this procedure. Equines can become sensitised to aversive events or procedures after very few exposures (4) therefore aversive procedures should be avoided wherever possible and stress experienced during veterinary procedures must be kept to an absolute minimum.

The above was presented as a poster

Donkey skin: the invisible fur trade

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Date presented: 
Wednesday 26 July 2017
Abstract

Increased levels of personal wealth in China is fuelling demand for luxury products including ejiao, a product made using donkey skin. A traditional medicine, ejiao’s popularity is largely due to its reported ‘anti-aging’ properties. Demand for donkey skins to produce ejiao is conservatively estimated at 4 million per year. This represents a significant proportion of the global donkey population of 44 million. China’s own donkey population has nearly halved in the last 20 years and entrepreneurs are now looking worldwide to satisfy a growing demand.

Despite their essential role in livelihoods and community resilience donkeys are largely invisible in livestock policies, livelihoods and humanitarian projects. It is therefore unsurprising that the emerging trade in skins is also invisible. Donkeys are frequently stolen from owners across Africa and illegally slaughtered in the bush; only the skins are removed and carcasses left to rot. In other areas, donkeys are bought at less than current market value and are transported in inhumane conditions to recently built ‘legal’ slaughterhouses. The invisibility of the legal and illegal markets is compounded by illegitimate export practices and criminal gangs. Due to the lucrative market for skins intensive farms are present in China and are likely to expand to other countries, such rearing creates significant welfare concerns for a species poorly adapted to intensive practices. Even if awareness of this trade improves, in the short term donkey owners are facing donkey prices that have increased up to tenfold within a few years and they are without the means to replace animals they depend on.

This emerging trade is, essentially, a fur trade with animal skins being sourced for human beauty. However while furs are visible, the role of donkey skins in ejiao products is invisible to the end user, mirroring the invisibility of the trade and donkeys themselves.

Equine Cyathostominae can develop to infective third-stage larvae on straw bedding

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Sandy Love, Faith A. Burden, Eoghan McGirr, Louise Gordon, Matthew Denwood. August 2016. Equine Cyathostominae can develop to infective third-stage larvae on straw bedding. Parasites and Vectors.

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Publication date: 
31 August 2016
DOI number: 
10.1186/s13071-016-1757-1
Abstract

Background
Domesticated grazing animals including horses and donkeys are frequently housed using deep litter bedding systems, where it is commonly presumed that there is no risk of infection from the nematodes that are associated with grazing at pasture. We use two different approaches to test whether equids could become infected with cyathostomines from the ingestion of deep litter straw bedding.

Methods
Two herbage plot studies were performed in horticultural incubators set up to simulate three straw bedding scenarios and one grass turf positive control. Faeces were placed on 16 plots, and larval recoveries performed on samples of straw/grass substrate over 2- to 3-week periods. Within each incubator, a thermostat was set to maintain an environmental temperature of approximately 10 °C to 20 °C. To provide further validation, 24 samples of straw bedding were collected over an 8-week period from six barns in which a large number of donkeys were housed in a deep litter straw bedding system. These samples were collected from the superficial bedding at 16 sites along a “W” route through each barn.

Results
No infective larvae were recovered from any of the plots containing dry straw. However, infective cyathostomine larvae were first detected on day 8 from plots containing moist straw. In the straw bedding study, cyathostomine larvae were detected in 18 of the 24 samples. Additionally, in the two barns which were sampled serially, the level of larval infectivity generally increased from week to week, except when the straw bedding was removed and replaced.

Conclusions
We have demonstrated that equine cyathostomines can develop to infective larvae on moist straw bedding. It is therefore possible for a horse or donkey bedded in deep litter straw to become infected by ingesting the contaminated straw. This has implications for parasite control in stabled equids and potentially in housed ruminants, and further investigation is required in order to establish the relative infective pressure from pasture versus straw bedding.

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Echocardiographic reference ranges for sedentary donkeys in the UK

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Susan L. Roberts, Joanna Dukes-McEwan. August 2016. Echocardiographic reference ranges for sedentary donkeys in the UK. The Veterinary Record.

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Publication date: 
18 August 2016
DOI number: 
10.1136/vr.103734
Abstract

The aim of this study was to provide two-dimensional (2D) and M-mode echocardiographic reference ranges from a sample of the UK population of donkeys including geriatrics (>30 years), owned by The Donkey Sanctuary, and to assess the influence of gender, weight and age on these variables. A total of 36 donkeys with no clinical or echocardiographic evidence of cardiovascular disease were examined; 24 geldings and 12 females, aged 3–45 years old, weighing 130–262 kg. Left atrial to aortic ratio was larger in geldings (P=0.004). There was no significant difference for left ventricular M-mode diastolic diameter between females and geldings (P=0.121) after exclusion of one heavy female outlier. 2D measurements significantly increased with bodyweight including maximal left atrial diameter (R2=0.112; P=0.046), aortic diameter at various levels (e.g. annulus: R2=0.35; P<0.001) and the pulmonary artery diameter (R2=0.124; P=0.035). M-mode measurements were not significantly influenced by weight other than the left ventricular free wall in systole (R2=0.118; P=0.041). Age and heart rate did not have any significant effect on echocardiographic variables. This is the first UK study to report on echocardiographic reference ranges of sedentary donkeys across a wide age range and shows differences compared with reference ranges from working donkeys.

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Assessment of cardiovascular disease in the donkey: clinical, echocardiographic and pathological observations

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Susan L. Roberts, Joanna Dukes-McEwan. August 2016. Assessment of cardiovascular disease in the donkey: clinical, echocardiographic and pathological observations. The Veterinary Record.

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Publication date: 
17 August 2016
DOI number: 
10.1136/vr.103733
Abstract

The Donkey Sanctuary (DS) owns 3500–4000 donkeys, estimated to be about 35 per cent of the UK population. Although postmortem surveys suggest a high prevalence of cardiovascular disease in donkeys, there is sparse clinical information about cardiovascular examination findings and echocardiographic findings in health and disease. In this cross-sectional study, auscultation findings were recorded, and in a subset of donkeys, echocardiography was used to screen for structural and functional cardiac disease. 202 donkeys were examined; 117 geldings and 85 females. Heart sounds S1 and S2 were detected in all donkeys, but none had audible S3. S4 was detected in nine (4.5 per cent; significantly older than those without S4; P<0.001). A heart murmur was detected in four donkeys. Echocardiography identified these to be due to a ventricular septal defect in one, and aortic regurgitation in three. An additional 43 donkeys had echocardiography. A further 10 donkeys were identified to have aortic insufficiency, but no other valvular regurgitation. 76/202 donkeys subsequently underwent postmortem examination. Three showed degenerative aortic valve changes. One donkey had nodular lesions in the intima of proximal aorta and sinus of Valsalva. Histopathology showed multifocal chronic nodular eosinophilic arteritis, consistent with verminous arteritis. The DS pathology database identified other similar cases.

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Papaya latex supernatant has a potent effect on the free-living stages of equid cyathostomins in vitro

Citation

Laura Peachey, Gina L. Pinchbeck, Jacqui. B. Matthews, Faith A. Burden, J.M. Behnke, Jane Hodgkinson. August 2016. Papaya latex supernatant has a potent effect on the free-living stages of equid cyathostomins in vitro. Veterinary Parasitology.

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Publication date: 
1 August 2016
DOI number: 
10.1016/j.vetpar.2016.07.036
Abstract

The control of equid gastrointestinal nematodes in developed countries, in particular the cyathostomins, is threatened by high levels of anthelmintic resistance. In recent years, there has been increasing interest in the evaluation of traditional ‘ethnoveterinary’ medicines as alternatives to chemical anthelmintics. The cysteine proteinases (CPs), a group of enzymes derived from fruits such as papaya (Carica papaya), pineapple (Ananas comosus) and figs (Ficus spp.), have shown good efficacy against adult stages of a range of parasitic nematodes, in vitro and in vivo. The efficacy of CPs against cyathostomins remains to be explored. In this study, the efficacy of a crude preparation of CPs, papaya latex supernatant (PLS), against the free-living stages of cyathostomins was evaluated using two in vitro tests, the egg hatch test (EHT) and the larval migration inhibition test (LMIT). It was demonstrated that PLS had a potent effect in the EHT, with EC-50 values in the range of 0.12-0.22 μM. At concentrations above 6.25 μM the eggs did not develop, below this concentration the L1 developed but they lost integrity of the cuticle upon hatching. These effects were inhibited by pre-incubation of PLS with the CP inhibitor L-trans-epoxysuccinyl-L-leucylamido-(4-guanidino butane) (E64), indicating that CPs were responsible for the anti-parasitic activity. A dose-dependent inhibition of migration of third stage larvae (L3) in the LMIT was demonstrated at higher concentrations of PLS, with EC-50 values in the range of 67.35-106.31 μM. Incubation of PLS with E64 prior to use in the LMIT did not reverse the anti-migratory effect, suggesting that CPs were not responsible for the reduced migration of cyathostomin L3 and that PLS also contains an additional active compound. This is the first report of PLS and/or CPs showing activity against the free-living stages of a parasitic helminth. In addition, it suggests that cyathostomins are highly sensitive to the effects of CPs and further evaluation of their efficacy against parasitic stages and in vivo are strongly indicated.

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Anaerobic fungi are a key unexplored taxa for optimizing lignocellulosic fibre utilisation in equines.

Citation

Joan E Edwards, David A van Doorn, Wilbert F Pellikaan, Jan Dijkstra, Henk Everts, Faith A. Burden, Hauke Smidt. Anaerobic fungi are a key unexplored taxa for optimizing lignocellulosic fibre utilisation in equines.. Presented at INRA-Rowett 2016 Symposium.

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Date presented: 
Tuesday 21 June 2016
Abstract

The hindgut microbiota of equines enables them to utilize forage/grazing based diets which contain a substantial proportion of lignocellulosic fibres. These fibres are a structural barrier that gut bacteria need to overcome when accessing plant nutrients, as well as being a challenging and structurally complex substrate that can be utilized. The limited dietary energy available from these ‘natural’ diets however means that many equines are supplemented with energy-dense concentrate feeds in order to fulfil their dietary energy requirements. Use of energy-dense concentrate feeds however can change the equine hindgut microbiome, and lead to the development of gut-mediated diseases (i.e. fermentative acidosis, laminitis, colic and stomach ulcers). There is therefore a clear need to optimize the utilization of lignocellulosic fibres in the equine hindgut in order to minimize the need for dietary supplementation. The most effective of the fibre-degrading gut microbes, anaerobic fungi (phylum Neocallimastigomycota), are known to be a normal member of the equine gut microbiota. Despite this however, they have been largely overlooked in equine gut microbiology studies to date. Research being conducted within the EU funded EQUIANFUN project will therefore establish baseline knowledge of the phylogeny, community structure, physiology and nutritional impact of anaerobic fungi in the equine hindgut. The insights gained will inform the development of novel strategies to promote indigenous anaerobic fungal communities in the equine hindgut, enabling optimization of the use of dietary forage as an energy source in equids. Reduction of the use of energy–dense diets and applying targeted nutritional strategies for optimizing microbial health may counteract processes in the gastrointestinal tract that have been associated with disease. Anaerobic fungi therefore offer the potential to enable significant advances to be made in the optimisation of the nutrition, health and welfare of all domesticated equids.

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