Equine Diarrhea Flashcards
What is diarrhea?
Passage of unformed feces with increased water content and increased frequency of defecation
What are the pathophysiological mechanisms associated with diarrhea in the horse?
Hypersecretion
Motility Alterations
Malabsorption
GIT inflammation
Osmosis
Pressure alterations
What is a rare process that can be associated with diarrhea in foals?
Sepsis - septicemia –> secondary foal diarrhea
What is the primary site of water absorption in the adult horse? What other functions does this site perform?
Large Intestine (Colon)
Microbial digestion of carbohydrate and protein/non-protein nitrogen
What is the difference between adult and foal large intestine?
Foal LI not as well developed due to all milk diet
Which part of the intestines can be responsible in adult horses vs. foals?
Adult horses - large intestine
Foals - Large or small intestine
What are the common causes of neonatal foal diarrhea (<1 month of age)
- Foal heat diarrhea
- Rotavirus, Salmonellosis, Clostridiosis
- Neonatal Septicemia
What is foal heat diarrhea?
Foals are not systemically ill
Diarrhea occurs in foals <6d days of age, during the time when mare enters her first heat cycle after foaling
Foals eat mare’s feces during this time, could be the cause of changing GI flora (rapid increase in bacteria which digests cellulose). –> diarrhea
Is rotavirus, salmonella, and clostridiosis contagious in foals?
Salmonella - very contagious (zoonotic)
Clostridiosis - not contagious
Rotavirus - contagious
What are some uncommon causes of neonatal foal diarrhea?
Necrotizing enterocolitis
Strongyloides westeri
Dietary intolerances
Cryptosporidium
What are the predisposing factors for foal septicemia?
Difficult birth
Failure to receive an adequate quality and quantity of colostral antibodies
Gestational age of the foal (prematurity)
Poor health and condition of the dam
Presence of new disease-causing agents in the environment against which the mare has no antibodies
Unsanitary environmental conditions
What are the early warning signs of a foal with neonatal septicemia?
The earliest sign may be that the foal is slightly depressed or does not act as lively as other foals. This progresses to a foal that will not eat and lies down frequently. The mare’s udder is often distended with milk, indicating that the foal is not nursing with normal frequency.
What is the treatment protocol for foals with neonatal septicemia?
Broad-spectrum antibiotics
Plasma transfusions (replace antibodies not received in colostrum)
IV fluids (counter the effects of bacterial toxins and infection)
+/- sugar solution (many septic foals hypoglycemic)
Nutritional support VERY important
How do you distinguish Clostridial vs. Salmonella diarrhea?
Clinically indistinguishable
Both causes severe abdominal pain (colic), diarrhea, etc.
Salmonella can be cultured/identified using PCR
For Clostridiosis you need to demonstrate bacterial toxins in feces (ELISA or toxin gene PCR) and culture anaerobically
What are the predisposing factors for Clostridial diarrhea?
ANTIMICROBIAL USE,food deprivation, stressors –> overgrowth of C. perfringens/C. difficile –> GI disease.
What are the common causes of weanling foal diarrhea (10-12 months)
Larval cyathostominosis
Proliferative enteropathy (Lawsonia)
What is larval cyathostominosis and how does it cause diarrhea? What is the treatment?
Emergence of encysted cyathostomin larvae from the large intestinal walls –> acute, generalized typhlocolitis (inflammation of cecum/colon) –> profuse, watery diarrhea +/- ventral edema
Treatment - Macrolytic Lactones (Moxidectin)
How do you diagnose larval cyathostominosis?
Cyathostomin LARVAE in feces (fecal egg counts often negative)
Serological tests which detects IgG Ab specific to larval cyathostomins
What kind of organism is Lawsonia? How does it cause diarrhea?
Lawsonia intracellularis - obligate intracellular organism
Causes diarrhea in foals (weanlings)
Lawsonia causes proliferation of infected enterocytes –> thickening of small intestinal epithelium –> fever, lethargy, peripheral edema, diarrhea, colic, weight loss.
How do you treat EPE/Lawsonia?
Antimicrobials and supportive therapy
What are some uncommon causes of diarrhea in weanling foals?
- Sand enteropathy (foals this age love to eat sand, abrasive → diarrhea)
- Salmonellosis, Clostridiosis
- Rhodococcus equi enterocolitis (bacteria that causes pulmonary abscesses, sometimes causes enterocolitis)
What are some common causes of adulte horse diarrhea (over 12-24 months of age)
- Larval cyathostomiasis
- Clostridiosis, Salmonellosis
- Carbohydrate overload/Dietary
- Sand Enteropathy
- Antimicrobial Associated Diarrhea (AAD)
- NSAID Induced ulcerative right dorsal colitis
- Inflammatory Bowel Disease
- Undiagnosed/Idiopathic
What are some uncommon causes that you should always consider when diagnosing an adult horse with diarrhea?
- Equine coronavirus
- GI neoplasia
- Potomac horse fever
- Peritonitis
- Plant toxicosis
- Blister beetle poisoning (eaten by horses)
What is Potomac Horse Fever caused by? Where is it most common? What are the symptoms? Prevention/Treatment? Is this contagious?
Bacterial disease caused Neorickettsia risticii
Horse eats aquatic insect/flatworm carrying bacteria
Symptoms (range from mild to severe) - fever, lethargy, poor appetite, diarrhea, mild colic, and laminitis (can infrequently cause abortion)
Common in US
Prevention - Vaccine
Treatment - IV abx/supportive care
Not contagious from horse to horse
Is acute or chronic diarrhea more of a medical emergency? Why?
Acute - Diarrhea is severe and clinical progression is rapid
Which signs do horses with acute diarrhea show?
Abdominal pain
Dehydration
Cardiovascular shock
Define acute diarrhea
Life threatening disorder characterized by hypersecretion of fluid, motility disturbances and an impaired mucosal barrier that results in absorption of endotoxin (causes severe systemic disease)
Define chronic diarrhea
Diarrhea is usually mild and will often have persisted for months
Horses with CHRONIC diarrhea are BAR and able to maintain their hydration without additional supportive care!
Is larval cyathostominosis a cause of chronic or acute diarrhea?
Both!
What are the causes of chronic diarrhea?
What are the causes of acute diarrhea?
What are the risk factors which predispose a horse to having diarrhea?
Young, performance horses
Previous Abx/NSAID administration
Stressors or concurrent illness (transport, exhaustion, hospitalization, temperature changes)
Recent deworming
Exposure to other horses with diarrhea (salmonella)
Poor foaling hygiene
Failure of passive transfer
Is it always important to make a diagnosis when it comes to the cause of diarrhea?
Kind of - treatment is usually the same regardless of the cause, but if you highly suspect something contagious or zoonotic then you might want to know exactly what it is to inform treatment, control and prevention measures
What are the 2 strains of Salmonella that cause diarrhea in horses?
S. typhimurium
S. anatum
What are the 2 strains of Clostridium which cause diarrhea in horses?
C. perfringens Type A
C. difficile
How do you test for Salmonella? How do you prove negative disease status?
Fecal PCR or Culture
At least 3-5 negative samples (both culture and PCR) required to determine negative disease status
Are asymptomatic carriers of salmonella normal/common in the horse population? Are these horses at risk?
Asymptomatic carriers exist in NORMAL horse population (as high as 10-20% of population)
- These horses are probably not a risk unless “in contact” horses are immunocompromised
How do you test for clostridiosis? What makes diagnosis challenging?
Clostridium is a gram negative anaerobe that is a normal commensal of the GIT, meaning it can appear on culture in a normal animal
Need to demonstrate TOXINS in stool to point to clostridium as the diagnosis for diarrhea
How do you test for rotavirus?
Fecal Electron Microscopy, ELISA, PCR
How do you test for coronavirus?
PCR
How do you test for cyathostominosis? Is an egg count helpful?
LARVAE in feces
Paired with evidence of poor deworming history
Egg counts often negative
Serological test that detects IgG Ab specific to larval cyathostomins
How do you calculate fluid deficit?
Fluid Deficit (L) = % dehydration x BWT (kg)
What are the principles for treatment of a horse with diarrhea?
- Biosecurity - prevent spread to other horses
- Fluid and electrolyte therapy
- Treatment of Endotoxemia
- Reestablish normal GI flora
- Nutrition
- Prevent Complications
- Administer specific treatments when needed
Are antimicrobials helpful for horses with diarrhea?
Not really - Horses treated with abx are 4.5x less likely to survive due to disruption of commensal GI flora
When is it appropriate to administer antimicrobials to horses/foals?
Foals with acute diarrhea (systemically ill) should be given abx as translocation can occur (septicemia)
In cases of confirmed clostridial infection give oral Metronidazole
How does treatment of foals compare to treatment of horses with diarrhea? What do you need to always keep in mind?
Same treatment principles, but foals are much less forgiving
Endotoxemia less of a problem, but sepsis due to bacterial translocation more common
When should you refer a horse with diarrhea?
Extensive fluid therapy (huge volume)
Contagious cases (isolation facilities)
What are some basic biosecurity measures you should take if you suspect a horse has contagious diarrhea?
- Isolate horses/foals with acute diarrhea
- Disinfect any personnel or equipment that come into contact with affected horses/foals (Ex. VIRKON)
- Use gloves, gowns, protective footwear, etc.
- Remember that Salmonella is a zoonosis!
How do you estimate an animal’s fluid deficit? Below what % can you not recognize a dehydrated animal? Above what % is dehydration not compatible with life?
What is the aim of resuscitation/rehydration fluid therapy? Which fluid type is the best choice?
- Aim is to restore circulating BV and replace the fluid deficit
- Use polyionic replacement crystalloids (Ex. Ringers lactate)
What is the aim of maintenance/ongoing losses fluid therapy? Which fluid type is the best choice?
- Aim is to meet physiological requirements and ongoing pathological losses
- Maintenance crystalloids ideal (rarely available)
- Most vets use resuscitation crystalloids and supplement with K/Ca
What is the fluid rate for resuscitation/rehydration?
Administer 50% of calculated deficit over 2-4 hours, Remaining fluid deficit should be corrected over next 24 hours
What is the maintenance fluid rate for an adult horse? What about for a foal?
Adult maintenance rate is 40-60mL/kg/day Foal maintenance rate is 80-100mL/kg/day
Example problem - 454kg adult horse with acute diarrhea 8% dehydrated
Fluid deficit = ?
Maintenance= ?
Ongoing losses = ?
How much fluid should you give initially?
Over how much time should you give the rest?
How does diarrhea affect acid/base balance in horses? What do they lose? How can this be corrected?
Horses with acute colitis are often acidotic
Lost HCO3- through damaged colon mucosa
If pH drops below 7.2 administer sodium bicarbonate slowly over period of 24 hrs
When are colloids indicated in horses with diarrhea?
Hypoproteinemia to replace fluid volume
What is endotoxin? How does it get released?
lipopolysaccharide from outer membrane of gram negative bacteria
Released during cell death or rapid growth
Ends up in blood stream
What is endotoxemia very similar to?
Septic shock
What are the early clinical signs of endotoxemia?
- Fever, Tachycardia +/- tachypnea
- Congested, toxic mucous membranes and prolonged CRT
- Inappetance, shivering, reduced intestinal motility, mild colic,
depression
What are the advanced clinical signs of endotoxemia?
- Edema
- Disseminated Intravascular Coagulopathy (DIC) - jugular and
microvascular thrombosis, petechial hemorrhages and prolonged
bleeding from injection sites - Progressive shock and circulatory failure
How do you diagnose endotoxemia?
Toxic changes to neutrophils
Degenerative left shift: Immature band neutrophils > mature segmented neutrophils
(T >38.6C, HR>60BPM, RR>30bmp, WBC>12,500cells/ul or
<4500cells/ul and/or 10% band neutrophils)
How do you treat endotoxemia?
Treatment of Endotoxemia
- Neutralization of circulating LPS
- Inhibition of LPS-induced inflammation
- Modulate coagulation system
- Circulatory support
