United Kingdom

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

Citation

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

Citation

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

Citation

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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Presentation details
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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Reference intervals for biochemical and haematological parameters in mature domestic donkeys (Equus asinus) in the UK

Citation

Faith A. Burden, Mulugeta Getachew, Elizabeth Hazell-Smith, Valerie Patrick, Ryan Trawford, Harriet Brooks Brownlie. November 2015. Reference intervals for biochemical and haematological parameters in mature domestic donkeys (Equus asinus) in the UK. Equine Veterinary Education.

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Publication date: 
18 November 2015
DOI number: 
10.1111/eve.12512
Abstract

Reference intervals (RIs) for haematology and serum biochemistry for donkeys in a temperate climate have been previously published using blood sample results from the resident population of a large donkey shelter in the UK. Periodic review of reference intervals is recommended to ensure their applicability to the patient population and changes in laboratory methods and technologies. The current study aimed to revise the previously published haematology and serum biochemistry values for the adult domestic donkey (Equus asinus) in the UK in the light of a change in analytical equipment at the Donkey Sanctuary laboratory, but also to refine the demography of the sample population with respect to age, physiology and clinical history. Clinical pathology results from 138 clinically healthy mature (4–24 years inclusive) female and castrated male donkeys selected from the resident population of the Donkey Sanctuary, were analysed retrospectively. The animals were blood sampled during the period February 2008 to June 2011 as part of a routine health screen prior to rehoming. Results for a total of 38 biochemical and haematological parameters were analysed including 3 previously unreferenced parameters in addition to those assessed in the previous study. The new reference intervals and median values show very poor transferability with recently derived reference intervals for non-Thoroughbred horses and only limited transferability with reference intervals previously published for donkeys in the UK. Of particular note is a marked reduction in the upper reference limit for triglycerides of 2.8 mmol/l (from 4.3 mmol/l) since this parameter is used to decide when donkeys are at risk of developing hyperlipaemia. This study demonstrates the value of intermittent review of reference intervals and refinement of study populations. Notwithstanding the caution with which reference interval data from different laboratories should be compared, the lack of transferability of results between donkeys and horses highlights the importance of use of species-appropriate reference intervals for clinical decision-making.

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Residual and ovicidal efficacy of essential oil-based formulations in vitro against the donkey chewing louse Bovicola ocellatus.

Citation

Bryony Sands, Lauren Ellse, Richard Wall. November 2015. Residual and ovicidal efficacy of essential oil-based formulations in vitro against the donkey chewing louse Bovicola ocellatus.. Medical and Veterinary Entomology.

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Publication date: 
2 November 2015
DOI number: 
10.1111/mve.12148
Abstract

Essential oils have shown good experimental potential as novel veterinary ectoparasiticides. However, if they are to be used as veterinary products, they must be available in formulations that are suitable for practical application against specific ectoparasites. Here, the efficacies of formulations containing 5% (v/v) lavender or tea tree oil, in combination with two emulsifiers [a surfactant, 5% (w/v) N-lauroylsarcosine sodium salt (SLS), and a soluble polymer, 5% (w/v) polyvinylpyrrolidone (PVP)], with or without 10% coconut oil, were tested in contact bioassays against the donkey chewing louse Bovicola ocellatus (Piaget) (Phthiraptera: Trichodectidae). Residual activity was quantified in open and closed containers; ovicidal efficacy was also examined. Exposure to either of 5% (v/v) lavender or tea tree oils with SLS or PVP resulted in louse mortality of 100%, but when coconut oil was included as an excipient, significantly lower efficacy was recorded. However, the formulations became significantly less effective after 2 h in open containers and 40 h in closed containers. The results confirm that the residual activity of essential oils is relatively transitory and the addition of 10% coconut oil does not prolong the period of insecticidal activity by slowing essential oil evaporation. Too short a period of residual activity is likely to be a significant impediment to the effective practical use of essential oils. However, unlike many synthetic pediculicides, the essential oils tested here were highly ovicidal, which suggests that prolonged residual activity may not be essential to kill newly hatched nymphs after treatment.

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Development of the larval migration inhibition test for comparative analysis of ivermectin sensitivity in cyathostomin populations

Citation

Claire McArthur, Ian G Handel, Ailie Robinson, Jane Hodgkinson, Barend MdeC Bronsvoort, Faith A. Burden, Ray Kaplan, Jacqui. B. Matthews. June 2015. Development of the larval migration inhibition test for comparative analysis of ivermectin sensitivity in cyathostomin populations. Veterinary Parasitology.

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Publication date: 
20 June 2015
DOI number: 
10.1016/j.vetpar.2015.06.019
Abstract

Cyathostomins are the most prevalent parasitic pathogens of equids worldwide. These nematodes have been controlled using broad-spectrum anthelmintics; however, cyathostomin resistance to each anthelmintic class has been reported and populations insensitive to more than one class are relatively commonplace. The faecal egg count reduction test (FECRT) is considered the most suitable method for screening anthelmintic sensitivity in horses, but is subject to variation and is relatively time-consuming to perform. Here, we describe a larval migration inhibition test (LMIT) to assess ivermectin (IVM) sensitivity in cyathostomin populations. This test measures the paralysing effect of IVM on the ability of third stage larvae (L3) to migrate through a pore mesh. When L3 from a single faecal sample were examined on multiple occasions, variation in migration was observed: this was associated with the length of time that the L3 had been stored before testing but the association was not significant. Half maximal effective concentration (EC50) values were then obtained for cyathostomin L3 from six populations of horses or donkeys that showed varying sensitivity to IVM in previous FECRTs. Larvae from populations indicated as IVM resistant by FECRT displayed significantly higher EC50 values in the LMIT than L3 from populations classified as IVM sensitive or L3 from populations that had not been previously exposed to IVM or had limited prior exposure. The analysis also showed that EC50 values obtained using L3 from animals in which IVM faecal egg count reduction (FECR) levels had been recorded as <95% were significantly higher than EC50 values obtained using L3 from animals for which FECR was measured as >95%. For one of the populations, time that had elapsed since IVM administration had an effect on the EC50 value obtained, with a longer time since treatment associated with lower EC50 values. These results indicate that the LMIT has value in discriminating IVM sensitivity amongst cyathostomin populations, but several factors were identified that need to be taken into account when executing the test and interpreting the derived data.

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