Diarrhoea in horses and foals Flashcards
Function of colon - adults and foals
ADULT: water reabsorption and microbial digestion (carbohydrate and protein/non-protein nitrogen)
FOAL: large colon not as well developed as in adults so bacterial pipulation less and less important for fluid absorption. Milk diet.
Where is the problem causing diarrhoea located in adults vs foals?
Adult - LI only
Foal - LI or SI
How to narrow down the list of DDx for equine diarrhoea - 3
- Age of animal?
- Duration of clinical signs?
- History - presence of risk factors?
DDx - neonates - commonest (4) and others (5)
COMMONEST: foal heat diarrhoea, viral (esp rotavirus), salmonella, clostridia
OTHERS: necrotising enterocolitis, sepsis, nutritional diarrhoea, parasitic diarrhoea (Strongyloides westeri), gastroduodenal ulceration.
DDx - older foals (up to 10-12 months) - commonest (4) and others (7)
COMMONEST: parasitic (strongyloides vulgaris, cyathostomins), proliferative enteropathy (Lawsonia intracellularis), Salmonella, Clostridia
OTHERS: crytosporidiosis, Rhodococcus equi colotis, viral (especially rotavirus), sepsis, nutritional diarrhoea, gastroduodenal ulceration, parasitic (Strongyloides westeri)
What is foal heat diarrhoea?
Nothing to do with the mare’s first heat cycle after parturition but an adaptation/change of the foal’s bacterial population in GIT.
DDx - adult equine diarrhoea - common (3) and others (9)
COMMON: Salmonellosis and clostridiosis, or often undiagnosed
OTHERS: parasite, antimicrobial-associated, NSAID, sand enteropathy, carbohydrate overload, inflammatory or infiltrative, dietary (abnormal fementation) neoplasia (lymphoma), peritonitis, abdominal absecessation
Differentiate acute and chronic diarrhoea
- ACUTE - acute onset, febrile diarrhoea, clinical signs of hypovolaemia, endotoxaemia
- CHRONIC: if more than 2 weeks duration
- The DDx for acute and chronic actually overlap quite a lot (e.g. salmonellosis, parasitism (larval cyathostominosis, strongylosis), NDSAID toxicity, sand enteropathy and carbohydrate overload can all be either acute or chronic).
What are ‘risk factors’ for equine diarrhoea - 4
- NSAID treatment
- anthelmintic history?
- antibiotic treatment?
- contact with other horses/foals with diarrhoea?
Is it important to make a definitive diagnosis?
Probably not but you should try because:
- contagious +/- zoonosis
- some specific treatments may work better
n.b. always test an equine diarrhoea case for salmonella
3 principles of therapy = ?
- address fluid loss
- address inflammation and endotoxaemia
- address specific cause
Principles of fluid therapy?
Mild dehydration seen with 5% fluid loss, sever dehydration with 10% fluid loss. For a 500kg racehorse, figures can be the following:
-deficits - 50L
-maintenance - 48L (2-4ml/kg/hr)
-ongoing losses - 50L
TOTAL = 150L. I/V fluids for this can cost £750 a day!
What is an endotoxin?
Part of OM of gram - bacteria. Released during cell death or rapid growth. Horse FIT normally has large numbers of gram negative bacteria but the normal mucosal barrier prevents access to circulation. Endotoxaemia is a complicating factor in many GIT diseases.
Why worry about endotoxaemia?
Endotoxin within circulation –> interacts with cells (e.g. macrophages) –> initiates systemic inflammation –> clinical signs of endotoxaemia –> CV and GIT dysfunction, shock, organ failure and death
Clinical signs - endotoxaemia - 7
- depression
- tachycardia
- tachypnoea
- fever
- colic
- diarrhoea
- hyperaemic ‘toxic’ mucous membranes
Diagnosis - endotoxaemia
Clinical signs
Low WBC count, low neutrophil count, immature ‘band’ neutrophils
Treatment - endotoxaemia
- prevent movement of endotoxin into the circulation (hard to do)
- neutralise endotoxin before it interacts with inflammatory cells
- prevent synthesis/release/action of inflammatory cells
- Prevent endotoxin-induced cellular activation
What drugs can be used in endotoxaemia? 4
Polymixin b (directly binds endotoxin)
Pentoxyfilline - less effective than polymixin b
Flunixin - blocks prostaglandin production
Hyperimmune plasma (USA) - neutralises endotoxin
How is endotoxaemia different in foals? - 4
Similar effects as in adult horses but usually associated with bacteriaemia/sepsis (unlike adults).
- Large colon less well developed therefore gram negative population may be smaller?
- Concern of nephrotoxicity (foal kidney less well developed) of certain drugs (polymixin B or flunixin)
- Treatments = plasma or ABs
Can you treat diarrhoea at home or do you need to refer? 4
- Most diagnostic tests/treatments don’t require hospitalisation
- Keeping up with fluids may be challenging (volume and frequency required). If a horse/foal can keep up with fluid requirements by drinking then it is probably okay to treat at home.
- best to be over cautious with foals as they can deteriorate very rapidly
- consider possibility of contagious agent? other animals nearby? (isolation facilities can be provided at a hospital)
Considerations - foals on fluids
- volumes required aren’t as large a adults so may be possible to give intermittent but frequent boluses OR
- separate mare and foal for continuous fluids but this is labour intesive!
