7.1.3: Mild colic and grass sickness Flashcards
A horse presents with colic and pyrexia. What are your differentials?
- Peritonitits
- Colitis
- Enteritis
- Non GI causes: pleuropneumonia and other infections
You are considering a diagnosis of peritonitis. What findings might you see on haematology?
- Leukopaenia
- Haemoconcentration/azotaemia/acidosis
- Increased acute phase proteins
You are considering a diagnosis of peritonitis. What findings might you see on abdominocentesis?
- TNCC greater than 5 x 10⁹
- Supportive cytological findings: neutrophils, macrophages, lymphocytes
- Lactate >2mmol/L
- Glucose <2 mmol/L
- Culture and sensitivity
What treatment would you administer to a horse with peritonitis?
- Antibiotics: penicillin and gentamycin
- IV fluids
- ± Abdominal lavage/drainage
What factors affect the prognosis of a horse with peritonitis?
- Depends on the source of contamination
- If GI rupture -> poor prognosis
- If after abdominal surgery -> guarded prognosis
- If peritonitis occurs without GI rupture -> generally good prognosis
Which equids are affected by grass sickness?
- Horses
- Ponies
- Donkeys
What are some risk factors for grass sickness?
- Being out at pasture
- Being on pasture that has a history of grass sickness cases
- Presence of domesticated birds on the field
- Stress
- The horse being in good-fat BCS
- Cool dry weather with temp. between 7-11C
- Frequent worming
What is equine grass sickness and what is causal agent?
- Equine grass sickness: a dysautonomia affecting primarily the enteric nervous system. There is a decrease in GI motility with a decrease in GI secretions. It is mainly the PSNS affected.
- Causal agent unknown, likely associated with levels of some toxin.
What clinical sign of equine grass sickness is shown here?
“Greyhound abdomen” - the horse is extremely tucked up with pain
How can we categorise equine grass sickness cases?
- Acute - these cases die rapidly
- Subacute - these horses survive >2 days
- Chronic - these horses survive >7 days
What are the clinical signs of acute grass sickness?
- Severe gut paralysis leading to signs of acute colic
- Difficulty swallowing
- Drooling saliva
- Nasogastric reflux
- Mucus-coated, hard droppings (evidence of slow passage through the GIT)
- Muscle tremors and patchy sweating
- Tachycardia (60-80bpm)
These horses usually die or are euthanised within 2 days of clinical signs.
What are the clinical signs of subacute grass sickness?
- Similar to the signs for acute but less severe
- Difficulty swallowing
- Mild-moderate colic
- Sweating and muscle tremors
- Weak with low head carraige, standing with legs underneath them (“elephant on a barrel”)
- Rapid weight loss
- May eat small amounts of food
May die or be euthanised within 1 week of clinical signs.
What are the clinical signs of chronic grass sickness?
- More insidious than signs of acute and subacute
- Mild or intermitten colic
- Reduced appetite
- May have some difficulty eating, but salivation/gastric reflux/ileus are not a major feature
- Rapid and severe weight loss/emaciation
- Triangular, tucked up “greyhound” abdomen
Some of these horses may recover.
What diagnostic tests could you perform to investigate equine grass sickness?
- Ileal biopsy
- Rectal biopsy
- Phenylephrine
- Oesophageal endoscopy
What is considered the best diagnostic test for equine grass sickness? Why might you choose not to perform it?
- Best diagnostic test = ileal biopsy
- However, this requires laparotomy (either flank or midline) which is associated with decreased survival
- Therefore, by chasing diagnosis with an ileal biopsy, we may be decreasing the horse’s chance of survival
What findings would you see on ileal biopsy of a horse with grass sickness?
- Neuronal degeneration within the autonomic ganglia
- There is depletion of the autonomic ganglia in other parts of the body
- There is vacuolation of cells
In chronic equine grass sickness, pathology is localised to the ileum. In acute disease, there is generalised intestinal pathology.
What are the benefits and limitations of rectal biopsy for diagnosis of equine grass sickness?
- 71% sensitivity, 100% specificity
- Negative result doesn’t rule out disease
- Can be carried out in standing horses
How does the phenylephrine test work for equine grass sickness?
- Horses with EGS show ptosis
- Topically apply 0.5% phenylephrine drops to one eye
- Examine 30 mins later
- Positive test = reversal of ptosis in that eye.
- This test is useful in supporting defective smooth muscle activity associated with EGS (which is temporarily overcome by the phenylephrine when administered)
- Need compatible clinical signs to make a diagnosis
- False positives can be seen
True/false: almost all horses with equine grass sickness have linear oesophageal ulcers due to reflux due to dysfunction of lower oesophagal sphincter. Therefore, oesophageal endoscopy is a good diagnostic test for equine grass sickness.
False
Oesophageal endoscopy may reveal findings as described.
However, many horses with EGS do not have oesophageal ulcers.
Treatment of equine grass sickness
- Symptomatic therapy for each individual problem
- Analgesia to promote voluntary feeding
- Acid suppression and sucralfate for oesophageal/gastric ulceration
- Small feeds every 30-60 mins (hand feeding, try varied diets)
- Appetite stimulants e.g. diazepam 0.02mg/kg - variable efficacy
- Prokinetics: cisapride (no longer available), neostigmine
- Steam and mucolytics for the rhinitis
- Nursing: grooming, access to other horses (within sight, sound)
What is the prognosis for equine grass sickness cases?
- No evidence that acute and subacute cases will survive; euthanasia probably best
- Chronic cases may recover but it will take time (mean 9 months to return to normal bodyweight, mean 12 months to return to normal work)
Prevention of equine grass sickness
- Cause not yet known
- In areas where disease is prevalent: stabling animals during spring and early summer will reduce likelihood of disease
- Associated with weather (stable horses when dry 7-11C has persisted for 10 consecutive days)
- If certain fields are bad for disease, they can be grazed by other stock especially in spring and summer
- If a case occurs amongst a group of horses, probably best to move the others out of the field provided this does not cause stress/issues with mixing horses
