gastrointestinal

Colitis and typhlitis are diagnosed in donkey populations. Precise clinical presentations vary, depending on whether acute or chronic, a single individual or a number of animals in a group outbreak situation. The common feature, irrespective of circumstance, is that of a dull donkey and consequently, in the initial stages can be challenging to differentiate from the many other potential causes of dullness. Typically, donkeys present as inappetent, or only picking at feed, behaviour is depressed and they may distance themselves from companions. It is vital that owners and vets are aware that this likely constitutes a medical emergency and a clinical exam should be performed without delay. In acute cases, the donkey may be tachycardic, tachypnoeic, pyrexic, have congested mucous membranes with delayed capillary refill time and significantly reduced borborygmi. However, many cases can initially present with relatively normal parameters, yet progress to a peracute presentation and become moribund within hours. A salient point is the lack of diarrhoea in most donkeys with colitis. Ventral or limb oedema is not a consistent finding. Overt demonstrations of abdominal pain, such as rolling or kicking at the abdomen are uncommon in donkeys but if present are likely to indicate severe pain.

Thorough history taking is essential to guide diagnosis. Risk factors for colitis in donkeys include stressors such as recent movement, management or dietary change, alongside ingestion of toxic feed substances, infectious aetiologies, endoparasite infestation and recent anthelmintic or antimicrobial use. Right dorsal colitis does not appear to be common in donkeys, irrespective of short or long-term NSAID treatment at standard maintenance doses. Dysbiosis, secondary to any of the previously listed stressors, may be a significant factor in the development of colitis. Toxic and infectious causes are higher up the differential list in an outbreak situation. In chronic cases, insidious weight loss may be noted and intermittent episodes of dullness and colic.

Common differentials include hyperlipaemia, hepatopathies, other forms of colic including impaction or sand and any systemic inflammatory process causing pain and discomfort. Co-morbidities of any of these with typhlocolitis are not uncommon and can complicate diagnosis and treatment.

In addition to the basic clinical exam, vets should perform a rectal examination where possible. The aim is two-fold – to establish the presence of intestinal distension, displacement or impaction and to obtain a faecal sample for subsequent analysis. Testing for Salmonella, C.difficile and C.perfringens (including toxins) and Coronavirus alongside worm egg counts are recommended. Additional tests may be advised for foals. A blood sample should be obtained for routine biochemistry and haematology alongside inflammatory markers and, essentially, serum triglyceride concentrations. Feed samples can be collected for analysis if ingested toxins are suspected. Passage of a nasogastric tube is useful to assess for the presence of reflux. Transcutaneous ultrasonographic abdominal examination is ideal for further assessment, including measurement of intestinal wall thickness but may not be available in the field. Owners should be counselled as to the guarded prognosis and potential costs involved. Referral to a clinic setting should be considered for donkeys in need of intensive care but the risks of stress induced by movement will need to be taken into account.

Initial treatment in an ambulatory setting and whilst awaiting results of initial diagnostics centres on stabilising the donkey, restoring fluid and energy deficits and relieving pain. Unless there is gastric reflux and/or complete ileus, if the donkey is not voluntarily eating, nasogastric intubation of a water/electrolyte combination (the average standard size donkey stomach will hold approximately 3 litres of fluid) with dextrose or glucose powder and oat-based cereal (fine milled porridge cereals) should be given. If an infectious or toxic aetiology is suspected, enteral adsorbants such as smectites may be given down the stomach tube. Severely hypovolemic donkeys, or those with total ileus may require intravenous fluid boluses in the field before being stable enough to transport to a clinic. Analgesia is essential, usually flunixin meglumine at 1.1mg/bwt BID i.v providing the donkey is sufficiently hydrated, otherwise anti-endotoxic doses can be given and/or paracetamol at 20-25mg/kg p.o BID. Alpha-2 agonists and opioids may be required for multimodal analgesia, again extrapolating from standard equine doses. Use of corticosteroids in the acute phase is often debated and should be subject to a risk benefit analysis -the merits of potent anti-inflammatory activity versus worsening of systemic infection for example. Decision making for administration of other medications, such as anthelmintics, antimicrobials, gastroprotectants, pro-kinetics and other anti-inflammatory and anti-endotoxin therapies follow the same rationale as for horses and there are no peer-reviewed donkey specific guidelines. In our Donkey Sanctuary population, post mortem data of non-survivors indicates that very sick donkeys with colitis may be predisposed to gastric glandular ulceration.

If the donkey is worsening or failing to respond to treatment and intensive care is an option then remember to hospitalise companions with the patient, to reduce further distress. As for horses, strict biosecurity measures should be adhered to until infectious causes can be ruled out. In a donkey with severe hypoalbuminaemia, colloid fluid therapy may be indicated. Severe mural oedema has been identified at post-mortem in the intestines of donkeys subjected to aggressive crystalloid therapy and this likely worsens ileus. Other conspicuous findings of non-survivors in our population at post-mortem have included focal or diffuse severe necrotisation and encysted cyathostome burdens

Vets and owners should establish clear end points for treatment, if the donkey is responding poorly. Repeated transabdominal ultrasound, blood work including lactate quantification and results of abdominocentesis may be used to guide decision making. There are donkey specific biochemical and haematology parameters [1] but normal intestinal wall thicknesses

and lactate reference ranges have not been established. For patients that are responding favourably, provision of their normal diet and good nursing care are essential for recovery. Like horses, donkey colitis patients may be prone to laminitis. Transfaunation using faeces from another donkey is a valid consideration in the recovering patient. Note that the donkey gut microbiome is not the same as that of the horse [2] and therefore horse-specific probiotics are unsuitable.

References:

[1] The Donkey Sanctuary (2020). Parameters for Haematology and Biochemistry. Available at: https://www.thedonkeysanctuary.org.uk/research/sites/uk/files/2020-02/parameters-for-haematology-and-biochemistry.pdf

[2] Edwards, J.E., Schennink, A., Burden, F. Long S., van Doorn D.A., Pellikaan W.F., Dijkstra J., Saccenti E., Smidt H.. (2020) Domesticated equine species and their derived hybrids differ in their fecal microbiota. Anim Microbiome 2(1):8