Equine grass sickness

Equine grass sickness (a multiple systems neuropathy) is associated with alterations in the gastrointestinal mycobiome

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.

Equine grass sickness in italy: a case series study

BACKGROUND

Equine grass sickness (EGS) has been reported in several European and extra-European countries. Despite this, no scientific paper about clinical cases of EGS in Italy has been published. EGS is a disease affecting almost exclusively horses kept on pasture, characterized by clinical signs related to lesions in autonomic nervous system (ANS), particularly in the enteric nervous system (ENS). According to clinical presentation, acute, subacute and chornic syndromes can be observed, with various sympthoms including dullness, anorexia, dysphagia, drooling of saliva, tachycardia, ptosis, patchy sweating and muscle fasciculations. In horses affected by acute forms, mild to moderate abdominal pain and large volumes of nasogastric reflux can be observed. The etiology is still speculative and many hypothesis have been proposed to explain the pathogenesis.

CASE PRESENTATION

The present study describes four cases of EGS (one subacute and three chronic forms) occurred in Central Italy during early spring. In all the cases included in the study, the prognosis was poor and the horses were euthanized. The diagnosis was confirmed by histological examination of ANS or ENS. In two cases, in vivo diagnosis was obtained by histological examination of enteric bioptic samples collected during laparoscopy.

CONCLUSIONS

EGS in Italy could be underdiagnosed and incidence understimated. Greater awareness should be applied in Italy for the inclusion of EGS in differential diagnosis for horses presenting clinical signs of abdominal pain associated or not with gastric reflux and muscular fasciculation. All the cases in this study concerned horses kept in the same pasture, confirming a possible premise-linked and management-linked factors on the ethiopathogenesis of EGS. The age of horses ranged from 2 to 6 years, that is consistent with the risk factor age for EGS (from 2 to 7 years of age). Previous suspected EGS diagnosis in the same livestock and recent cool dry weather were considered additional potential risk factors.

Potential applications of aptamers in veterinary science

Aptamers are small nucleic acids that fold in a three-dimensional conformation allowing them to bind specifically to a target. This target can be an organic molecule, free or carried in cells or tissues, or inorganic components, such as metal ions. Analogous to monoclonal antibodies, aptamers however have certain advantages over the latter: e.g., high specificity for their target, no to low immunogenicity and easy in vitro selection. Since their discovery more than 30 years ago, aptamers have led to various applications, although mainly restricted to basic research. This work reviews the applications of aptamers in veterinary science to date. First, we present aptamers, how they are selected and their properties, then we give examples of applications in food and environmental safety, as well as in diagnosis and medical treatment in the field of veterinary medicine. Because examples of applications in veterinary medicine are scarce, we explore the potential avenues for future applications based on discoveries made in human medicine. Aptamers may offer new possibilities for veterinarians to diagnose certain diseases—particularly infectious diseases—more rapidly or “at the patient’s bedside”. All the examples highlight the growing interest in aptamers and the premises of a potential market. Aptamers may benefit animals as well as their owners, breeders and even public health in a “One Health” approach.

Diagnostic and Clinical Course of Small Colon Recurrent Impaction Associated with Severe Myenteric Ganglionopathy in A Mare

A 10-year-old Koninklijk Warmbloed Paardenstamboek Nederland (KWPN, Netherlands-based organization for registration of the Dutch Warmblood horses) mare was evaluated three times over four months because of recurrent colic. At every referral, a physical examination revealed a small colon impaction, which partially responded to food deprivation and oral administration of water and magnesium sulphate. Due to the recurrent nature of the small colon impaction, several differential diagnoses were considered: inflammatory bowel disease (IBD), chronic salmonellosis and myenteric ganglionopathies. At first admission, an exploratory laparotomy was proposed, but the owner declined. On the second hospitalisation, the mare underwent a standing exploratory laparoscopy, but no abnormality related to the small colon was detected and resolved with a soap-based enema. At the third hospitalisation, the owner agreed to the exploratory laparotomy, which allowed surgical biopsies of the caecum and the large and small colon. Lymphomonocytic enteritis and mild myenteric ganglionitis were diagnosed. After laparotomy, the mare regularly fed and defecated, but a few days later, tachycardia, fever and abundant gastric reflux occurred. As the clinical condition rapidly deteriorated, the owner elected for euthanasia. A post-mortem histological examination showed severe chronic lymphocytic enterocolitis and typhlitis associated with the marked depletion of myenteric ganglion bodies. Small colon impaction is a very common disorder of the small colon in horses. In the presence of myenteric ganglionopathies, this case proposes the controversial matter of primary or secondary disorders of enteric neuromuscular function as the base of repeated small colon impactions of the horse. In this mare, recurrent small colon impaction was considered secondary to severe myenteric ganglionopathy associated with chronic intestinal pseudo-obstruction.

Family aggregation analysis shows a possible heritable background of equine grass sickness (dysautonomia) in a Hungarian stud population

Equine grass sickness (also known as dysautonomia) is a life-threatening polyneuropathic disease affecting horses with approx. 80% mortality. Since its first description over a century ago, several factors, such as the phenotype, intestinal microbiome, environment, management and climate, have been supposed to be associated with the increased risk of dysautonomia. In this retrospective study, we examined the possible involvement of genetic factors. Medical and pedigree datasets regarding 1,233 horses with 49 affected animals born during a 23-year period were used in the analysis. Among the descendants of some stallions, the proportion of animals diagnosed with dysautonomia was unexpectedly high. Among males, the odds of dysautonomia were found to be higher, albeit not significantly, than among females. Significant familial clustering (genealogical index of familiality, P = 0.001) was observed among the affected animals. Further subgroups were identified with significant (P < 0.001) aggregation among close relatives using kinship-based methods. Our analysis, along with the slightly higher disease frequency in males, suggests that dysautonomia may have a genetic causal factor with an X-linked recessive inheritance pattern. This is the first study providing ancestry data and suggesting a heritable component in the likely multifactorial aetiology of the disease.

Factors Influencing Equine Gut Microbiota: Current Knowledge

Gastrointestinal microbiota play a crucial role in nutrient digestion, maintaining animal health and welfare. Various factors may affect microbial balance often leading to disturbances that may result in debilitating conditions such as colic and laminitis. The invention of next-generation sequencing technologies and bioinformatics has provided valuable information on the effects of factors influencing equine gut microbiota. Among those factors are nutrition and management (e.g., diet, supplements, exercise), medical substances (e.g., antimicrobials, anthelmintics, anesthetics), animal-related factors (breed and age), various pathological conditions (colitis, diarrhea, colic, laminitis, equine gastric ulcer syndrome), as well as stress-related factors (transportation and weaning). The aim of this review is to assimilate current knowledge on equine microbiome studies, focusing on the effect of factors influencing equine gastrointestinal microbiota. Decrease in microbial diversity and richness leading to decrease in stability; decrease in Lachnospiraceae and Ruminococcaceae family members, which contribute to gut homeostasis; increase in Lactobacillus and Streptococcus; decrease in lactic acid utilizing bacteria; decrease in butyrate-producing bacteria that have anti-inflammatory properties may all be considered as a negative change in equine gut microbiota. Shifts in Firmicutes and Bacteroidetes have often been observed in the literature in response to certain treatments or when describing healthy and unhealthy animals; however, these shifts are inconsistent. It is time to move forward and use the knowledge now acquired to start manipulating the microbiota of horses.

A study of residual lesions in horses that recovered from clinical signs of chronic equine dysautonomia

BACKGROUND

Equine dysautonomia (ED) causes degeneration and loss of autonomic neurons. Approximately 50% of chronic cases recover, but it is unclear how they survive neuronal loss.

OBJECTIVES

To assess lesions, autonomic neuron numbers, interstitial cells of Cajal (ICC), and neurodegeneration in recovered cases.

ANIMALS

Thirteen cases (group ED), euthanized 10.3 ± 5.2 (1-16) years from diagnosis and 6 age-matched controls (group C).

METHODS

Prospective, case control; routine post mortem examination, neuron counts in peripheral and enteric ganglia and immunohistochemical assessment of neural networks (Protein gene product [PGP] 9.5), ICC (c-kit), and neurodegeneration (beta-amyloid precursor protein and ubiquitin) in intestine.

RESULTS

Postmortem findings in group ED were small intestinal dilation (4/12, 33%) and muscular hypertrophy (4/12, 33%), and gastric mucosal hypertrophy (3/11, 27%) and ulceration (4/11, 36%). Neuron density was lower in group ED (mean 39% lower for cranial cervical ganglion [P < .001], median 44% lower in celiacomesenteric ganglion [P = .01]). In intestine, neuronal depletion was worst in ileum (median 100% lower in submucosal plexus [P < .001], 91% lower in myenteric plexus [P = .004]). Group ED had less PGP 9.5 staining in ileal myenteric plexus (mean 66% lower [P = .04]) and circular muscle (median 75% lower [P = .006]). In ileum, there was less c-kit staining in myenteric plexus (median 57% lower [P = .02]) but not muscularis externa. Beta-amyloid precursor protein and ubiquitin results were not indicitive of neurodegeneration.

CONCLUSIONS AND CLINICAL IMPORTANCE

Intact ICC in muscularis externa might help maintain motility after neuronal loss. Treatment supporting ICC function warrants investigation.

Ganglion Cytology: A Novel Rapid Method for the Diagnosis of Equine Dysautonomia

Equine dysautonomia (grass sickness) is characterized by autonomic neuronal degeneration and is often fatal. As outbreaks occur, rapid diagnosis is essential but confirmation currently requires histological examination. This study evaluated diagnostic accuracy of cytological examination of cranial cervical ganglion (CCG) scrapings for dysautonomia diagnosis. CCG smears from 20 controls and 16 dysautonomia cases were stained with May-Grünwald Giemsa (MGG), hematoxylin and eosin (HE), and cresyl fast violet (CFV), with HE-stained histological sections of CCG as gold standard for diagnosis. Examining all 3 stains together, the sensitivity and specificity were 100%. Occasional individual smears (4/107, 3.7%) were nondiagnostic due to low cellularity, and in a few individual smears the final diagnosis was correct but more tentative (CFV: 5/33 [15.1%], HE: 2/34 [5.9%], and MGG: 4/36 [11.1%]), due to low cellularity or suboptimal cell morphology. CCG cytology was considered reliable for rapid postmortem diagnosis of equine dysautonomia, particularly using MGG.

Equine Dysautonomia

Equine dysautonomia (ED; also known as equine grass sickness) is a neurological disease of unknown cause, which primarily affects grazing adult horses. The clinical signs reflect degeneration of specific neuronal populations, predominantly within the autonomic and enteric nervous systems, with disease severity and prognosis determined by the extent of neuronal loss. This review is primarily focused on the major clinical decision-making processes in relation to ED, namely, (1) clinical diagnosis, (2) selection of appropriate ancillary diagnostic tests, (3) obtaining diagnostic confirmation, (4) selection of treatment candidates, and (5) identifying appropriate criteria for euthanasia.

Development of a clinical prediction score for detection of suspected cases of equine grass sickness (dysautonomia) in France

Equine grass sickness (EGS) (equine dysautonomia) is a neurodegenerative condition of grazing equines. Pre-mortem diagnosis of EGS is a challenge for practitioners as definitive diagnosis requires ileal/myenteric lymph node biopsies. This study aimed to develop a clinical score that could be used by practitioners to improve the detection of acute or subacute EGS cases in the field. Suspected EGS cases were declared by veterinary practitioners. A case was classified as confirmed positive if ileal or rectal biopsy samples showed neuronal degeneration typical of EGS. A semi-quantitative scoring system, including epidemiological and clinical data, was created to attempt to classify suspected EGS horses into confirmed positive or negative cases. Each variable was weighted based on a boosted regression trees model, while taking into account its clinical relevance. Twenty-eight EGS cases were confirmed by biopsy during the entire study period. The best cut-off value for the score to have a high sensitivity while maximizing specificity was 8, with a sensitivity of 100% and a specificity of 53%. In our dataset, 77% of animals would be correctly classified with this cut-off value of 8. Highest sensitivity was chosen in order to detect the highest number of potential cases. Our score represents an inexpensive and useful tool to aid in the identification of suspected EGS cases in the field and selection for further diagnostics procedures to confirm or rule out the disease. Application of the score to larger populations of animals would be required to further adapt and refine the score.

Histological assessment of β-amyloid precursor protein immunolabelled rectal biopsies aids diagnosis of equine grass sickness

BACKGROUND

An accurate, minimally invasive, ante-mortem diagnostic test for equine grass sickness (EGS) is currently lacking. Although histological examination of haematoxylin and eosin-stained rectal biopsies for chromatolytic neurons is insensitive as a diagnostic test for EGS, we hypothesised that its diagnostic accuracy could be improved by immunolabelling for β-amyloid precursor protein (β-APP), which has increased expression in cranial cervical ganglia (CCG) neuronal perikarya in EGS.

OBJECTIVES

To develop a grading scheme for assessing the distribution and intensity of β-APP immunoreactivity within individual rectal submucosal neurons and subsequently to determine the value of the distribution of different grades of neurons in EGS diagnosis.

STUDY DESIGN

Retrospective case-control diagnostic accuracy study.

METHODS

Initially, a standardised grading scheme was developed and β-APP immunoreactivity in individual neuronal perikarya and axons was compared in sections of CCG and ileum from EGS and control horses. The grading scheme was then refined before being blindly applied to submucosal neurons in rectal biopsies derived from 21 EGS and 23 control horses.

RESULTS

β-APP immunoreactivity was increased in neuronal perikarya and axons in sections of CCG, ileum and rectum from EGS horses compared with controls. For rectal biopsies, a mean immunoreactivity grade exceeding 1.1 was 100% specific and sensitive for EGS, and the presence of at least one neuron with diffuse labelling of the entire cytoplasm (grade 3) was 95% sensitive and 100% specific for EGS.

MAIN LIMITATIONS

Although the diagnostic criteria facilitated the discrimination of the EGS and control biopsies evaluated in this study, further prospective validation using a larger sample set is required.

CONCLUSIONS

Histological assessment of β-APP immunolabelled rectal biopsies is more sensitive than conventional histological examination in EGS diagnosis. Further validation is required before this technique can be advocated for use in clinical decision making.

Alterations in amino acid status in cats with feline dysautonomia

Feline dysautonomia (FD) is a multiple system neuropathy of unknown aetiology. An apparently identical disease occurs in horses (equine grass sickness, EGS), dogs, rabbits, hares, sheep, alpacas and llamas. Horses with acute EGS have a marked reduction in plasma concentrations of the sulphur amino acids (SAA) cyst(e)ine and methionine, which may reflect exposure to a neurotoxic xenobiotic. The aim of this study was to determine whether FD cats have alterations in amino acid profiles similar to those of EGS horses. Amino acids were quantified in plasma/serum from 14 FD cats, 5 healthy in-contact cats which shared housing and diet with the FD cats, and 6 healthy control cats which were housed separately from FD cats and which received a different diet. The adequacy of amino acids in the cats’ diet was assessed by determining the amino acid content of tinned and dry pelleted foods collected immediately after occurrences of FD. Compared with controls, FD cats had increased concentrations of many essential amino acids, with the exception of methionine which was significantly reduced, and reductions in most non-essential amino acids. In-contact cats also had inadequate methionine status. Artefactual loss of cysteine during analysis precluded assessment of the cyst(e)ine status. Food analysis indicated that the low methionine status was unlikely to be attributable to dietary inadequacy of methionine or cystine. Multi-mycotoxin screening identified low concentrations of several mycotoxins in dry food from all 3 premises. While this indicates fungal contamination of the food, none of these mycotoxins appears to induce the specific clinico-pathologic features which characterise FD and equivalent multiple system neuropathies in other species. Instead, we hypothesise that ingestion of another, as yet unidentified, dietary neurotoxic mycotoxin or xenobiotic, may cause both the characteristic disease pathology and the plasma SAA depletion.

Designing a field trial of an equine grass sickness vaccine: A questionnaire-based feasibility study

Without an experimental model of equine grass sickness (EGS), a randomised controlled field trial (RCT) represents the only method of evaluating the efficacy of Clostridium botulinum type C vaccination in preventing naturally occurring disease. Clinical trial feasibility is an important aspect of preliminary work undertaken prior to initiating RCTs, estimating parameters that are important for study design. This cross-sectional study aimed to assess the feasibility of conducting a nationwide RCT of a candidate vaccine for EGS based on responses from a sample of British equine veterinary practices (n = 119/284). Seventy-three percent of practices had attended ≥1 EGS case within the preceding 2 years (median four cases), and 51.3% regularly attended recurrently affected premises. Veterinary surgeons had greater confidence diagnosing acute/subacute EGS based solely on history and clinical signs compared to chronic EGS. Ninety-one percent of respondents (n = 103/113) considered the proposed RCT to be important/very important to equine veterinary research. Ninety-one percent of respondents (n = 102/112) indicated preparedness to assist in owner recruitment and 92.9% (n = 104/112) indicated willingness to participate in a RCT. The most frequent reasons for practices declining to participate were low incidence of EGS (n = 4), did not believe clients would wish to participate (n = 3) and amount of paperwork/data collection involved (n = 2). There was considerable support amongst participating veterinary practices for a RCT evaluating the efficacy of Clostridium botulinum vaccination for the prevention of EGS in Britain. Substantial proportions of participating practices would be prepared to participate in the RCT and regularly attended EGS-affected premises that would meet trial inclusion criteria.

Bodyweight change aids prediction of survival in chronic equine grass sickness

REASONS FOR PERFORMING STUDY

Objective criteria for predicting survival of chronic grass sickness cases are currently lacking.

OBJECTIVES

To determine whether the rate and/or magnitude of bodyweight change during hospitalisation of chronic grass sickness cases can provide an objective predictor of survival to discharge from hospital. Clinicians' recorded indication(s) for euthanasia were also reviewed.

STUDY DESIGN

Single centre retrospective observational study.

METHODS

Case records of all horses admitted for management of chronic grass sickness to The Dick Vet Equine Hospital between 1998 and 2013 were analysed. Case background, survival to hospital discharge, indication(s) for euthanasia, disease duration at admission and bodyweight changes during the hospitalisation period were analysed, and data for survivors and nonsurvivors compared. Percentage weight change was calculated for 7 day intervals up to 28 days (0-7, 7-14, 14-21, 21-28 days) and for entire periods from the first weight recorded (0-7, 0-14, 0-21, 0-28 days). These results were used to estimate survival probability conditional on weight change.

RESULTS

The study sample comprised 213 horses, with 114 survivors (53.5%) and 99 (46.5%) nonsurvivors. Compared with nonsurvivors, survivors had significantly lower median maximum bodyweight loss as a percentage of first weight (survivors 5.9%, interquartile range 1.8-13.5; nonsurvivors 12.7%, 6.4-17.3). Throughout all time periods analysed, survivors had significantly lower median bodyweight loss than nonsurvivors, but no specific time period was more predictive of survival. Highest percentages of total bodyweight loss for individual horses were comparable for survivors (36%) and nonsurvivors (37%). Survival prediction curves reporting percentage survival rates for all time periods analysed provided data to aid prediction of chronic grass sickness survival.

CONCLUSIONS

Overall, nonsurvivors had greater bodyweight loss than survivors. Rapidity and magnitude of bodyweight loss were equally predictive of outcome. Percentage survival prediction curves provide objective data to aid discussion of prognosis, but greater predictive specificity with associated sensitivity is required for clinical decision making in individual cases.

Equine grass sickness, but not botulism, causes autonomic and enteric neurodegeneration and increases soluble N-ethylmaleimide-sensitive factor attachment receptor protein expression within neuronal perikarya

REASONS FOR PERFORMING STUDY

Equine grass sickness (EGS) is of unknown aetiology. Despite some evidence suggesting that it represents a toxico-infection with Clostridium botulinum types C and/or D, the effect of EGS on the functional targets of botulinum neurotoxins, namely the soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins, is unknown. Further, while it is commonly stated that, unlike EGS, equine botulism is not associated with autonomic and enteric neurodegeneration, this has not been definitively assessed.

OBJECTIVES

To determine: 1) whether botulism causes autonomic and enteric neurodegeneration; and 2) the effect of EGS on the expression of SNARE proteins within cranial cervical ganglion (CCG) and enteric neuronal perikarya.

STUDY DESIGN

Descriptive study.

METHODS

Light microscopy was used to compare the morphology of neurons in haematoxylin-eosin stained sections of CCG and ileum from 6 EGS horses, 5 botulism horses and 6 control horses. Immunohistochemistry was used to compare the expression of synaptosomal-associated protein-25, synaptobrevin (Syb) and syntaxin within CCG neurons, and of Syb in enteric neurons, from horses with EGS, horses with botulism and control horses. The concentrations of these SNARE proteins in extracts of CCG from EGS and control horses were compared using quantitative fluorescent western blotting.

RESULTS

EGS, but not botulism, was associated with autonomic and enteric neurodegeneration and with increased immunoreactivity for SNARE proteins within neuronal perikarya. Quantitative fluorescent western blotting confirmed increased concentrations of synaptosomal-associated protein-25, Syb and syntaxin within CCG extracts from EGS vs. control horses, with the increases in the latter 2 proteins being statistically significant.

CONCLUSIONS

The occurrence of autonomic and enteric neurodegeneration, and increased expression of SNARE proteins within neuronal perikarya, in EGS but not botulism, suggests that EGS may not be caused by botulinum neurotoxins. Further investigation of the aetiology of EGS is therefore warranted.

Proteomic Profiling of Cranial (Superior) Cervical Ganglia Reveals Beta-Amyloid and Ubiquitin Proteasome System Perturbations in an Equine Multiple System Neuropathy

Equine grass sickness (EGS) is an acute, predominantly fatal, multiple system neuropathy of grazing horses with reported incidence rates of ∼2%. An apparently identical disease occurs in multiple species, including but not limited to cats, dogs, and rabbits. Although the precise etiology remains unclear, ultrastructural findings have suggested that the primary lesion lies in the glycoprotein biosynthetic pathway of specific neuronal populations. The goal of this study was therefore to identify the molecular processes underpinning neurodegeneration in EGS. Here, we use a bottom-up approach beginning with the application of modern proteomic tools to the analysis of cranial (superior) cervical ganglion (CCG, a consistently affected tissue) from EGS-affected patients and appropriate control cases postmortem. In what appears to be the proteomic application of modern proteomic tools to equine neuronal tissues and/or to an inherent neurodegenerative disease of large animals (not a model of human disease), we identified 2,311 proteins in CCG extracts, with 320 proteins increased and 186 decreased by greater than 20% relative to controls. Further examination of selected proteomic candidates by quantitative fluorescent Western blotting (QFWB) and subcellular expression profiling by immunohistochemistry highlighted a previously unreported dysregulation in proteins commonly associated with protein misfolding/aggregation responses seen in a myriad of human neurodegenerative conditions, including but not limited to amyloid precursor protein (APP), microtubule associated protein (Tau), and multiple components of the ubiquitin proteasome system (UPS). Differentially expressed proteins eligible for in silico pathway analysis clustered predominantly into the following biofunctions: (1) diseases and disorders, including; neurological disease and skeletal and muscular disorders and (2) molecular and cellular functions, including cellular assembly and organization, cell-to-cell signaling and interaction (including epinephrine, dopamine, and adrenergic signaling and receptor function), and small molecule biochemistry. Interestingly, while the biofunctions identified in this study may represent pathways underpinning EGS-induced neurodegeneration, this is also the first demonstration of potential molecular conservation (including previously unreported dysregulation of the UPS and APP) spanning the degenerative cascades from an apparently unrelated condition of large animals, to small animal models with altered neuronal vulnerability, and human neurological conditions. Importantly, this study highlights the feasibility and benefits of applying modern proteomic techniques to veterinary investigations of neurodegenerative processes in diseases of large animals.

Canine dysautonomia in a litter of Havanese puppies

Canine dysautonomia is a sporadic, generally fatal disease that rarely affects groups of related animals. Four 10-week-old Havanese puppies from a litter of 5 developed clinical signs of canine dysautonomia. The 4 affected dogs were exposed to an outdoor environment, whereas the fifth littermate was not exposed to the outdoors and remained clinically healthy. Clinical signs of dysautonomia developed 10–16 days after going outside the house. An unrelated dog also developed dysautonomia after exposure to 1 of the affected Havanese littermates. All 5 dogs had morphological changes consistent with dysautonomia (widespread neuronal degeneration in autonomic ganglia, select brainstem nuclei, and ventral horn motor neurons). Differential diagnoses were excluded through negative toxicological evaluation, fecal parasite screening, negative Canine distemper virus reverse transcription polymerase chain reaction, fluorescent antibody testing, attempted virus isolation, and electron microscopy. The 5 affected dogs were in the Kansas City, Missouri area, where there is a high incidence of dysautonomia.

Excitatory and inhibitory enteric innervation of horse lower esophageal sphincter

The lower esophageal sphincter (LES) is a specialized, thickened muscle region with a high resting tone mediated by myogenic and neurogenic mechanisms. During swallowing or belching, the LES undergoes strong inhibitory innervation. In the horse, the LES seems to be organized as a "one-way" structure, enabling only the oral-anal progression of food. We characterized the esophageal and gastric pericardial inhibitory and excitatory intramural neurons immunoreactive (IR) for the enzymes neuronal nitric oxide synthase (nNOS) and choline acetyltransferase. Large percentages of myenteric plexus (MP) and submucosal (SMP) plexus nNOS-IR neurons were observed in the esophagus (72 ± 9 and 69 ± 8 %, respectively) and stomach (57 ± 17 and 45 ± 3 %, respectively). In the esophagus, cholinergic MP and SMP neurons were 29 ± 14 and 65 ± 24 vs. 36 ± 8 and 38 ± 20 % in the stomach, respectively. The high percentage of nitrergic inhibitory motor neurons observed in the caudal esophagus reinforces the role of the enteric nervous system in the horse LES relaxation. These findings might allow an evaluation of whether selective groups of enteric neurons are involved in horse neurological disorders such as megaesophagus, equine dysautonomia, and white lethal foal syndrome.