EQ GI

3 common serovars of salmonella

S. Typhimurium
S. Dublin (cattle)
S. Choleraesuis (horses)

Lawsonia intracellularis

Gram negative
Aerobe

Equine proliferative enteropathy (EPE)

Lawsonia intracellularis infection
Generally post-weaning foals (2-8 mths)

Porcine proliferative enteropathy (PPE)

Lawsonia intracellularis infection
Causes porcine intestinal adenomatosis, necrotic enteritis, and proliferative haemorrhagic enteropathy

Signs of lawsonia intracellularis infection

Rapid decrease in BCS, anorexia
Hypoproteinaemia
Peripheral oedema
Fever, lethargy
Colic, diarrhoea
Secondary bacteraemia

Virulence factors of lawsonia intracellularis

Inhibition of enterocyte differentiation \= impaired absorption \= osmotic/malabsorptive diarrhoea
Induction of enterocyte proliferation

Diagnosis of lawsonia intracellularis

ELISA for antibodies (exposure)
PCR of faeces (active infection)
Gross PM findings
Immunohistochemistry

Rhodococcus equi

Causes suppurative bronchopneumonia in foals
Can also cause ulcerative colitis (due to swallowing of respiratory exudate)

Clostridia

Gram positive
Anaerobe

3 main types of clostridia causesing enteric disease

C. perfringes \= enterotoxaemia
C. difficile \= entero-typhlo-colitis
C. piliform \= Tyzzer's disease

Mechanisms of Clostridial enteric disease

Local effects \= haemorrhage, fibrinous/necrotising enteritis
Secretory effects \= diarrhoea, minor mucosal lesions
Systemic effects \= absorption of enterotoxins

Extra-intestinal lesions of Clostridial enteric disease

Lungs \= congestion, haemorrhage, thrombosis
Heart \= subepicardial and subendocardial haemorrhage
Visceral organs and serosal surfaces \= congestion and
haemorrhage
Mesenteric LNs \= oedema, congestion, haemorrhage
Kidneys \= tubular degeneration and necrosis

Extra-intestinal lesions causes by Cl. perfringes type D

Focal symmetrical encephalomalacia

Potomac Horse Fever/Equine Monocytic Ehrilichiosis

Neorickettsia risticii
Fibronecrotic to ulcerative colitis
Signs: colic, diarrhoea, systemic signs, laminitis, s/c oedema, abortion, leukopaenia

Equine Adenovirus (EAdV)

EAdV 1 \= URT infection in foals
EAdV2 \= GIT infection (SI villous atrophy, necrosis/ulceration of distal oesophagus and non-glandular gastric mucosa, adenoviral intranuclear inclusions)

What parts of the ANS are affected in Equine Grass Sickness

Post-ganglionic sympathetic and parasympathetic neurons
Prevertebral and paravertebral ganglia
Cranial nerve nuclei of the brainstem

Risk factors for equine grass sickness

Grazing
Recent move to new pasture
2-7 years old
Spring/early summer

Acute/subacute equine grass sickness

1-2/2-7 days
Progressive, severe tympany
Painful swallowing \= drooling
Distended stomach (with pale tan mucinous fluid) (rupture possible)
Excess SI fluid
LI compacted with dry material
Faecal pellets small and dry (can have blackened surface due to bleeding)

Chronic equine grass sickness

\>7 days
Decreased stomach contents
Hypertrophy of intestinal musculature

ANS lesions associated with equine grass sickness

Chromatolysis (dispersion/loss of Nissl substance)
Cytoplasmic swelling/vacuolation
Peripheral displacement of nucleus

Causes of gastric dilation in the horse

Primary dilation:
Excess fermentable CHOs
Sudden access to lush pasture
Excessive water intake
Secondary dilation:
Intestinal obstruction
Equine grass sickness

Volvulus

Twisting of intestines along mesenteric axis

Intestinal loop herniation through Foramen of Winsow/epiploic foramen

Intestine trapped though epiploic foramen in the horse \= compression of vessels \= impaired venous drainage \= severe congestion and haemorrhagic infarct

Intestinal intussusception

Due to intestinal irritation and hypermobility(e.g. enteritis, foreign bodies, parasites, neoplasia)
Damage to both the trapped and trapping portions

Equine nematodes

Parascaris equorum
Strongylus vulgaris
Cyathostomins
Strongyloides westeri
Oxyuris equi
Dctyocaulus arnfeldi

Parascaris equorum: disease

Foals, weanlings and yearlings
Larvae migrate to liver then lungs and then trachea to SI
Larval migration \= liver fibrosis and cough
Adults in SI \= ill thrift, colic (obstruction)

Parascaris equorum: control

Avoid using the same paddock for foals in successive years
Deworm from 1 month of age until 6 months

Parascaris equorum: treatment

Slowly kill worms (as rapid deworming can cause impaction colic) using Fenbendazole

Parascaris equorum: diagnosis

Faecal eggs are diagnostic

Strongus vulgans: disease

Migration through mesenteric arteries \= thrombus/infarctions \= intestinal necrosis \= colic
Adults in caecum and ventral colon

Strongus vulgans: control/treatment

Deworming - very sensitive to most anthelmintics

Strongus vulgans: diagnosis

Eggs in faeces cannot be distinguished from other strongyles

Cyathostomes: disease

Most common nematode pathogen in horses (especially \>5 years)
Adults in caecum and colon don't cause disease
L3 invade mucosal lining forming cysts - L4 erupts from these into the colon
L3 cysts can arrest which allows the infection to build up \= can erupt at the same time \= significant disease \= sudden onset life-threatening diarrhoea and colic in spring

Cyathostomes: treatment

Fluids and colloids
Steroids
Deworming with moxidectin or fenbendazole
Supportive care

Cyathostomes: control

Serum ELISA to assess encysted worm burden
Treat for encysted worms in the winter (moxidectin)

Strongyloides westeri: disease

Nursing foals
Transmammary infection of nursing foals due to mobilisation of arrested larvae from dam's abdominal wall

Strongyloides westeri: treatment

Deworm dam:
Moxidectin 4 weeks prior to parturition
Ivermectin at time of foaling

Oxyuris equi: disease

AKA anal rust, pinworm
Adults live in colon, gravid females migrate to anus and lay eggs
Very itchy

Oxyuris equi: diagnosis

Tape strip and microscopy

Oxyuris equi: control

Environmental decontamination

Oxyuris equi: treatment

Wash perineal area (transient itch relief)
Fenbendazole or Pyrantel

Dictyocaulus arnfieldi: disease

Lungworm
Patent, asymptomatic infection in donkeys
Horses infected by co-grazing with donkeys (not patent infection in horses so difficult to detect)
Causes severe bronchial inflammation

Dictyocaulus arnfieldi: treatment

Ivermectin or Moxidectin

Main equine cestode

Anoplocephala perfoliata

Anoplocephala perfoliata: disease

Ileocaecal junction \= inflammation (affects activity of large area of the intestines) \= colic
IH \= forage mites

Anoplocephala perfoliata: diagnosis

Serum ELISA (eggs difficult to detect)

Anoplocephala perfoliata: treatment

Pyrantel or Praziquantel

Gasterophilus sp.: disease

Eggs laid on coat and hatch on contact with lips
Not generally associated with disease (some can cause rectal prolapse) but are irritating

Gasterophilus sp.: treatment

Use bot knife when grooming in summer to remove eggs
Ivermectin or moxidectin

Pasture management to reduce worm burden in horses

Removal of faeces
Rotation grazing
Mixed grazing
Avoid high density

5 classifications of colic

Simple medical
Obstructive
Non-strangulating infarction
Enteritis/Colitis
False colic

Most common causes of colic in foals

Meconium impaction (

Most common cause of colic in equine weanlings

Ascarid impaction

Most common type of colic in geriatric horses

Strangulating lipoma

Colic history questions

When did it start
Faecal output
Appetite
Management (feeding, exercise, housing)
Worming
Dental history
Previous colic
Recent medications/injuries

What 3 things should be done before sedatives in an equine colic exam

HR
Resp. rate
GI sounds

Indications for equine nasogastric tube when colicing

Reflux seen from nostrils
HR \>60BPM
Gastric dilation seen on U/S

Risks of nasogastric intubation in horses

Aspiration pneumonia
Haemorrhage from ethmoturbinates
Trauma

What would be a normal NET reflux from an equine stomach via NG tube

2L

Treatment for rectal tear during rectal exam in horses

Communicate with client and insurance company
Assess extent of tear
Broad-spectrum Abs
Referral if \>grade 1
Epidural and rectal packing

What to do if you do not have time to do a full clip and scrub for equine abdominal U/S

Soak hair with alcohol

What is equine abdominal U/S good for

SI abnormalities
Liver/spleen/kidney issues
Gastric distension
L dorsal displacement
Colitis
Large colon volvulus
R dorsal displacement

What do tight horizontal bands on equine rectal palpation indicate

Right doral displacement

What causes increased lactate in a horse

Hypovolaemia/dehydration
Devitalised intestines
Anaemia
Hypoxia
Bacteria

What is the earliest indicator of strangulating intestinal lesions in the horse

Red serosanguinous fluid with increased lactate on abdominocentesis

Appearance of abdominocentesis fluid due to septic peritonitis

Decreased glucose
Turbid/cloudy (increased proteins and WBCs)

What is indicated by plant matter or mixed intra and extracellular bacteria on abdominocentesis

Intestinal rupture
Euthanasia

Short acting analgesics for horse

Xylazine
Buscopan
Morphine
Ketamine

Long acting analgesics for horses

Detomidine
Butorphanol
NSAIDs

NSAID side effects in horse

Renal injury
Right dorsal colitis
Delayed mucosal healing

Why should refractory pain after Flunixin administration be investigated

Potent analgesic

Spasmolytic/Buscopan: action

Parasympathetic - blocks muscarinic receptors
Short action (20mins)

Duration of action of xylazine

30-40mins

Duration of action of detomidine

1h

Duration of action of romifidine

60-90mins

Duration of action of ketamine

20mins

Fluid maintenance level in horse

60ml/kg/day

Fluid maintenance level in foal

100ml/kg/day

When is IVFT indicated in horses

Reflux
Hypovolaemia

Enteral fluid therapy in horse

NG tube
1-2L
Isotonic fluid
Repeat every 30min-2h
Walking the horse will speed up gastric emptying

GI impaction treatment in the horse

Soften impaction (high volume fluids)
Increase GI motility (walking, Bethanechol)
Maintain comfort (analgesics - Flunixin)
Withhold feed until cleared
Surgery as a last resort

Left dorsal displacement/nephrosplenic entrapment: treatment in horse

Phenylephrine (a1 agonist)
Rolling (requires GA)
Surgery (good prognosis)
Percutaneous caecal trochorisation (controversial)

Treatment of enteritis in horses

Frequent gastric decompression via NG tube
IVFT
Anti-endotoxic therapy (NSAID)

Treatment for sand impaction in horses

Mild \= psyillium via NGT
Severe \= surgery

Ddx for lack of swallowing in the horse

Mechanical issues:
Persistent epiglottic entrapment
Pharyngeal mass
Tongue FB
Tongue base neoplasia
Severe temporohyoid osteoarthropathy
Anatomical issues
Palatoschisis
Neurological issues
Loss of pharyngeal sensation/co-ordination due to guttural pouch mycosis/neoplasia

Signs of mechanical dysphagia in horses

Gagging and neck stretching when trying to swallow
Nasal regurgitation
Slow feed consumption

Diagnosis of mechanical dysphagia in horses

Oral exam
Palpation of retropharyngeal region and oesophagus
Cannot pass a stomach tube
Endoscopy
Radiography

Glossitis in the horse: management

Debridement and lavage
Topical/systemic metronidazole
Stomach tube for nutritional support

Palatoschisis

Defect in the palate which create an opening between the oral and nasal cavities

What is indicated if there is pain on passing an NGT in a horse

Grass sickness/dysautonomia (due to reverse peristalsis)

Simple oesophageal obstruction (choke) in horses: signs

Just after feeding (especially if just exercised or dry feed)
Bilateral nasal regurgitation
Gagging/retching/stretching neck
Cough
Panic (e.g. rolling)

Simple oesophageal obstruction (choke) in horses: diagnosis

Feed material in nasal discharge
Distended oesophagus
Resistance to NGT and cough

Simple oesophageal obstruction (choke) in horses: management

Mild \= may spontaneously resolve
Sedation and lavage via NGT
Remove food and bedding, then soft diet for 1wk
Broad spectrum antibiotics (aspiration pneumonia is common)
NSAIDs

Ddx for secondary oesophageal obstruction in the horse

Pulsion diverticulum
Traction diverticulum
Strictures
Persistent right aortic arch

Oesophageal stricture in the horse: management

Oesophagotomy
Soft diet for 10d
Monitor for adhesions

Oesophageal rupture in the horse: signs

Swelling/pain
S/c emphysema
Draining tracts
(CVS compromise if mediastinitis develops)

Oesophageal rupture in the horse: diagnosis

Contrast oesophagram

Oesophageal rupture in the horse: management

Drain
Surgical debridement
Place NGT to provide nutrition
Monitor for sepsis
Euthanasia if rupture is in thorax

Clinical signs of chronic gastric distension in the horse

Weight loss and decreased appetite
Increased water intake
Recurrent mild colic
Pendulous abdomen +/- ventral oedema

Clinical signs of chronic gastric inflammation in the horse

Asymptomatic progressing to acute colic
Change in dietary preference