Dysautonomia in a six-year-old mule in the United States

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.

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.

Equine grass sickness

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.

A nationwide surveillance scheme for equine grass sickness in Great Britain: results for the period 2000-2009

REASONS FOR PERFORMING STUDY

Equine grass sickness (EGS) remains a frequently fatal disease of equids in Great Britain (GB). The first nationwide surveillance scheme for EGS was developed to obtain information on the occurrence of EGS and to help facilitate future proposed intervention studies, such as vaccine trials.

OBJECTIVES

To collect both retrospective and prospective data on cases of EGS occurring in GB since 2000 and to assess potential risk factors for categories of EGS and survival after chronic EGS.

METHODS

Prospective data were collected using a nationwide surveillance scheme for EGS that was developed and initiated in 2007. Data were collected by means of postal and online questionnaires documenting both retrospective premises-level and prospective case-level information. Data on outcomes of EGS category and survival after chronic grass sickness (CGS) were analysed using univariable logistic regression.

RESULTS

Descriptive data for 1410 EGS cases occurring in GB in the decade between the beginning of 2000 and the end of 2009 are presented. Univariable logistic regression analyses identified that CGS cases in Scotland were significantly more likely to survive than those occurring elsewhere in GB. There was no relationship between case details and the category of EGS or the outcome among CGS cases.

CONCLUSIONS

EGS affected equids throughout England, Scotland and Wales. Although an overall average of 141 cases were reported to the nationwide surveillance scheme annually, this number of cases was not consistent between years. Around 50% of CGS cases survived, although regional differences in survival rates existed, probably due to variation in expertise of care and/or disease severity.

POTENTIAL RELEVANCE

This study provides information on the spatiotemporal occurrence of EGS in GB during the last decade. Data from the nationwide surveillance scheme can be used in developing protocols for future intervention studies such as Clostridium botulinum vaccine trials.