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McGorum BC, Chen Z, Glendinning L, Gweon HS, Hunt L, Ivens A, Keen JA, Pirie RS, Taylor J, Wilkinson T, McLachlan G. Equine grass sickness (a multiple systems neuropathy) is associated with alterations in the gastrointestinal mycobiome. Anim Microbiome 2021; 3:70. [PMID: 34627407 PMCID: PMC8501654 DOI: 10.1186/s42523-021-00131-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Accepted: 09/14/2021] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Equine grass sickness (EGS) is a multiple systems neuropathy of grazing horses of unknown aetiology. An apparently identical disease occurs in cats, dogs, rabbits, hares, sheep, alpacas and llamas. Many of the risk factors for EGS are consistent with it being a pasture mycotoxicosis. To identify potential causal fungi, the gastrointestinal mycobiota of EGS horses were evaluated using targeted amplicon sequencing, and compared with those of two control groups. Samples were collected post mortem from up to 5 sites in the gastrointestinal tracts of EGS horses (EGS group; 150 samples from 54 horses) and from control horses that were not grazing EGS pastures and that had been euthanased for reasons other than neurologic and gastrointestinal diseases (CTRL group; 67 samples from 31 horses). Faecal samples were also collected from healthy control horses that were co-grazing pastures with EGS horses at disease onset (CoG group; 48 samples from 48 horses). RESULTS Mycobiota at all 5 gastrointestinal sites comprised large numbers of fungi exhibiting diverse taxonomy, growth morphology, trophic mode and ecological guild. FUNGuild analysis parsed most phylotypes as ingested environmental microfungi, agaricoids and yeasts, with only 1% as gastrointestinal adapted animal endosymbionts. Mycobiota richness varied throughout the gastrointestinal tract and was greater in EGS horses. There were significant inter-group and inter-site differences in mycobiota structure. A large number of phylotypes were differentially abundant among groups. Key phylotypes (n = 56) associated with EGS were identified that had high abundance and high prevalence in EGS samples, significantly increased abundance in EGS samples, and were important determinants of the inter-group differences in mycobiota structure. Many key phylotypes were extremophiles and/or were predicted to produce cytotoxic and/or neurotoxic extrolites. CONCLUSIONS This is the first reported molecular characterisation of the gastrointestinal mycobiota of grazing horses. Key phylotypes associated with EGS were identified. Further work is required to determine whether neurotoxic extrolites from key phylotypes contribute to EGS aetiology or whether the association of key phylotypes and EGS is a consequence of disease or is non-causal.
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Affiliation(s)
- Bruce C McGorum
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, EH25 9RG, UK.
| | - Zihao Chen
- Ashworth Laboratories, University of Edinburgh, Edinburgh, EH9 3FL, UK
| | - Laura Glendinning
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, EH25 9RG, UK
| | - Hyun S Gweon
- School of Biological Sciences, University of Reading, Reading, RG6 6EX, UK
| | - Luanne Hunt
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, EH25 9RG, UK
| | - Alasdair Ivens
- Ashworth Laboratories, University of Edinburgh, Edinburgh, EH9 3FL, UK
| | - John A Keen
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, EH25 9RG, UK
| | - R Scott Pirie
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, EH25 9RG, UK
| | - Joanne Taylor
- Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh, EH3 5LR, UK
| | - Toby Wilkinson
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, EH25 9RG, UK
| | - Gerry McLachlan
- Royal (Dick) School of Veterinary Studies and The Roslin Institute, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, EH25 9RG, UK
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Pirie RS, Jago RC, Hudson NPH. Equine grass sickness. Equine Vet J 2014; 46:545-53. [PMID: 24580639 DOI: 10.1111/evj.12254] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 02/18/2014] [Indexed: 11/30/2022]
Abstract
Equine grass sickness (EGS; equine dysautonomia) is a polyneuronopathy affecting both the central and the peripheral nervous systems of horses. As the name implies, EGS almost exclusively affects grazing horses, resulting in the development of a characteristic array of clinical signs, most of which can be attributed to neuronal degeneration in the autonomic and enteric nervous systems. Varying disease severities occur, largely determined by the extent of neuronal degeneration in the myenteric and submucous plexuses of the enteric nervous system. Extensive neuronal degeneration, as seen in acute and subacute forms of EGS, results in intestinal dysmotility, the severity of which is incompatible with survival. In comparison, a proportion of chronic forms of EGS, characterised by less severe neuronal degeneration, will survive. Despite extensive research efforts since EGS was first reported over 100 years ago, the precise aetiology remains elusive. This article reviews much of the scientific literature on EGS, covering epidemiology, pathology, diagnosis, treatment and aetiological hypotheses.
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Affiliation(s)
- R S Pirie
- Royal (Dick) School of Veterinary Studies and Roslin Institute, University of Edinburgh, Easter Bush Veterinary Campus, Midlothian, UK
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Mellor NE, Bladon B, Foote AK, O'Meara B. Successful treatment of chronic grass sickness in a donkey. EQUINE VET EDUC 2013. [DOI: 10.1111/eve.12067] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- N. E. Mellor
- Baskerville Horgan and Partners; Buckinghamshire
| | - B. Bladon
- Donnington Grove Veterinary Surgery; Berkshire UK
| | | | - B. O'Meara
- Donnington Grove Veterinary Surgery; Berkshire UK
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Abstract
OBJECTIVE To determine signalment, history, clinical findings, results of autonomic function testing and other antemortem diagnostic tests, and pathologic findings in dogs with dysautonomia. DESIGN Retrospective study. ANIMALS 65 dogs with dysautonomia. PROCEDURE Case records of 68 dogs with a diagnosis of dysautonomia were reviewed; inclusion criteria included histologic confirmation of dysautonomia or clinical signs and results of pharmacologic testing consistent with dysautonomia. RESULTS 65 dogs fulfilled all criteria for dysautonomia. Dogs from rural environments were overrepresented, and cases of dysautonomia were reported for every month, although the highest number of cases was reported in February and March. Vomiting was the most common clinical sign, followed by diarrhea, signs of anorexia and depression, weight loss, and dysuria. The most common physical examination finding was decreased or absent anal tone, followed by absent pupillary light reflexes and elevated nictitating membrane. Results of pharmacologic testing were consistent with dysautonomia, although no single test was 100% sensitive. Histologic lesions consistent with dysautonomia were found in the autonomic ganglia, brainstem nuclei, and ventral horns of the spinal cord. CONCLUSIONS AND CLINICAL RELEVANCE Dysautonomia is an endemic disease in Kansas, and a high index of suspicion of the disease can be made by combining clinical signs, physical examination findings, and results of pharmacologic testing.
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Affiliation(s)
- Kenneth R Harkin
- Department of Clinical Sciences, College of Veterinary Medicine, Kansas State University, Manhattan 66506-5701, USA
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McCarthy HE, Proudman CJ, French NP. Epidemiology of equine grass sickness: a literature review (1909-1999). Vet Rec 2001; 149:293-300. [PMID: 11570789 DOI: 10.1136/vr.149.10.293] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
The geographical spread of grass sickness between 1909 and 1999, particularly in England and Wales, is described, and the experimental investigations to identify a causal agent are summarised. The epidemiological techniques used to investigate grass sickness vary from clinical observations, to more advanced methods such as case-control studies using logistic regression analyses. Several risk factors for grass sickness have been reported consistently (age, time of year and recent movement to new pasture or premises) and several others have been reported for which the findings remain inconsistent (weather, pasture type, breed, supplementary feeding and use of anthelmintics).
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Affiliation(s)
- H E McCarthy
- Department of Veterinary Clinical Science and Animal Husbandry, University of Liverpool, Neston, Cheshire
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