Exam 3 - Equine Colitis Flashcards
what are the 6 mechanisms of diarrhea?
- hypersecretion
- malabsorptive
- inflammatory/exudative
- osmotic
- deranged motility
- increased oncotic pressure
T/F: equine diarrhea is generally related to the large intestines
true
what is free fecal water syndrome?
not actually diarrhea - excess water is seen at the beginning or after defecation with an otherwise healthy horse
unknown cause - may be diet related
what specific diagnostic tests can be used to identify the cause of diarrhea?
PCR/culture
imaging, ultrasound, & biopsy
what non-specific diagnostics can be used for medical management of equine diarrhea?
cbc - look for leukopenia/leukocytosis, elevated PCV, & elevated/decreased TP
biochem - fluid loss, expect low Na, K, Cl, azotemia, & albumin/globulins (oncotic pressure)
regardless of etiology, treatment of equine colitis relies on what?
supportive care - anti-inflammatories (pepto), IVF, etc
why do you see clinical signs in endotoxemia from colitis?
the body responds to the endotoxin from the cell wall of gram negative bacteria (LPS)
what clinical signs are associated with endotoxemia related to colitis?
tachycardia, pyrexia, dull/lethargy, hyperemic mucus membranes/toxic line
how can you prevent further absorption of endotoxin in equine colitis?
remove the injured intestines & use a bio sponge
what treatment is used in endotoxemia from colitits that binds to the endotoxin to prevent its action?
polymixin b & plasma
what medication is given in endotoxemia that reduces the production of inflammatory mediators?
NSAIDS
why provide hoof support/ice therapy to horses with endotoxemia?
they are at risk for developing laminitis
what are the most-common non-infectious causes of equine colitis?
- dietary change
- grain overload
- antibiotic associated
- NSAID toxicity
- sand enteropathy
- blister beetle ingestion
what are the clinical signs associated in colitis caused by dietary change/grain overload? clin-path abnormalitis?
soft-liquid feces, mild colic-abdominal distension, endotoxemia, & laminitis
dehydration, elevated lactate/anion gap
what is the treatment used for dietary change/grain overload equine colitis?
supportive care, decrease concentrate or access to rich grass/hay, slow diet alterations, & increase fiber in the diet
how is antibiotic associated colitis diagnosed?
history of antibiotics & diagnosis of exclusion
why do antibiotics cause colitis?
disrupt the normal gut flora
what is the treatment for antibiotic associated colitis?
stop the antibiotics, give oral probiotics, transfaunation, & supportive care
what are the clinical signs of antibiotic associated colitis?
mild to severe colitis
what is the typical history of a horse with sand impaction?
possible or obvious exposure to sand, sandy environment, or eating off the ground
what clinical signs are associated with sand impaction? clin path abnormalities?
colic - may result in colonic inflammation, obstruction, or rupture
diarrhea, weight loss, anorexia
lab work - mild inflammatory signs & decreased albumin
how is sand impaction diagnosed?
radiography!!! most sensitive & gold-standard
xiphoid auscultation, glove test (low sensitivity/specificity)
what is seen on this rad of an equine abdomen?
sand colic
what is the treatment & prevention of sand impaction?
psyllium mucilloid (metamucil, sand clear) - 1 gram/kg via NGT quickly SID for 3-5 days
epsom salts - 1 gram/kg via NGT with psyllium SID 3-5 days
elevate food off of the ground
why do we see right dorsal colitis with NSAIDS in horses?
there is a relatively narrow therapeutic range for nsaids & excessive dosing can cause toxicosis in a couple days
COX1 & COX 2 - selective but may be slightly less toxic to git but not kidneys
if using the recommend dosing of NSAIDS, when can you expect toxicosis to occur?
days to weeks
risks of developing right dorsal colitis from NSAIDS are exacerbated by what?
dehydration, sepsis
how is right dorsal colitis from NSAID toxicity diagnosed & treated?
history, ultrasound, & diagnosis of exclusion
misoprostol & sucralfate, change the diet to a low bulk food (eliminate hay), corn, oil, psyllium
what are the 2 most common lab abnormalities seen in blister beetle toxicosis?
hypocalcemia & hypomagnesemia
what are the clinical signs of cantharidin toxicity?
ulcerations through out the gi tract, synchronous diaphragmatic flutter, muscle contraction/3rd eyelid protrusion, usually more than 1 horse affected
fatality of 50% or higher
how is cantharidin toxicity treated?
IVF with calcium
charcoal or biosponge
gastroprotectants
what are the 4 bacterial infectious causes of diarrhea in horses?
- salmonella
- clostridial - perfringens & difficile
- potomac horse fever
- lawsonia intracellularis - younger horses
what is the most common viral infectious cause of diarrhea in horses?
coronavirus
what is the most common infectious parasitic cause of diarrhea in horses?
small strongyles
what is the most frequent isolate of salmonella in horses?
salmonella enterica serovar typhimurium
T/F: horses aren’t considered to be carriers of salmonella, but asymptomatic shedders can shed a very small amount
true
why do teaching hospitals carry the greatest risk of salmonella outbreaks?
the horses are stressed & potentially immunocompromised - colic & antibiotic use, so some horses may shed it
what are the biggest components of clinical signs of salmonella in horses?
gi problems 35-60%
lameness 17%
asymptomatic 1-5%
what is the pathogenesis of salmonella?
the animal ingests the organism & mucosal invasion & adhesion occurs (enterotoxins released)
intestinal fluid secretions, activation of local inflammation, LPS systemic responses, malabsorption, & bacteremia
what clinical signs are associated with salmonella?
asymptomatic!!!!
colic, enterocolitis, pyrexia, & endotoxemia
what would you expect to see on lab work of a horse with salmonella?
leukopenia characterized by a neutropenia with a toxic left shift
dehydration, hypoproteinemia, electrolyte derangements with fluid loss
how is salmonella diagnosed?
multiple fecal samples on all horses with diarrhea
3-5 samples all 12-24 hours apart (liquid samples less likely to be positive), shedding is intermittent
fecal or reflux culture
PCR - good screening tool, if positive, culture recommended for serotyping
why do you run so many fecals when looking to discharge a salmonella horse from the hospital?
they can shed it for 4-6 weeks up to several months after clinical signs have resolved - you must isolate them for 6 weeks or until you have 5 negative tests
T/F: you must isolate a salmonella horse for 6 weeks or until you have 5 negative tests before considering them cleared of the infection
true
how is salmonella treated?
supportive care, manage endotoxemia (endoserum/plasma), antibiotics (enrofloxacin) but may prolong illness, consider bacterial translocation in very sick animals
transfaunation & probiotics to support colonic microbes
how is salmonella prevented/controlled?
good biosecurity, isolation of infected individuals, & screening in some hospitals
what toxins are associated with clostridium difficle?
toxins A & B
what toxins are associated with clostridium perfringens?
toxins A & C
what are the clinical signs of clostridial infections in horses?
similar to salmonella, perfringens especially in foals may be hemorrhagic, & may cause sudden death
what is the common history of horses with clostridial infections?
often associated with antibiotic use
how are clostridial infections diagnosed?
identify toxins with PCR or ELISA
organisms are apart of the normal microbiome - culture doesn’t tell you much
what is the treatment for clostridial infections in horses?
metronidazole or penicillin, bio sponge, antidiarrheal, & something to bind exotoxins
what is the etiology of potomac horse fever?
neorickettsia risticii
what is the pathogenesis of potomac horse fever?
agent infects peripheral monocytes & macrophages, colonic & small intestinal epithelial cells, & colonic mast cells
what are the clinical signs associated with potomac horse fever?
febrile, poor appetite, mild to severe gi signs, laminitis in 30% of cases
what clin path abnormalities would you expect in a horse with potomac horse fever?
leukopenia & hypoproteinemia
what is the treatment used for PHF?
oxytetracycline - 6.6mg/kg IV, clinical signs typically improve within 48 hours
protect their feet!!!
what prevention is used for PHF?
insect control (aquatic snails)
vaccine isn’t great but may be useful in endemic areas
when are horses typically affected by coronavirus?
winter - fecal oral transmission
what are the clinical signs of coronavirus in horses?
generally self limiting with clinical signs for 7-10 days & shedding up to 25 days
leukopenia or leukocytosis on labs
asymptomatic, encephalopathy secondary to hyperammonia in miniature horses, fever, lethargy, anorexia, enterocolitis/colic, co-infection in foals with rotavirus or c. perfringens
what are some chronic causes of colitis (diarrhea) causing weight loss?
parasites, sand enteropathy, chronic salmonella, & inflammatory/infiltrative bowel disease or alimentary lymphoma
what classifies as chronic diarrhea in horses?
duration greater than 3-4 weeks - feces may be normal, soft, or liquid
can be inflammatory or physiologic
what is the typical history of an animal with chronic diarrhea & weight loss from parasites?
small strongyles - poor parasite control, anthelmintic resistance, & PPID horses
what may you see on lab work of a horse with chronic diarrhea & weight loss from parasites?
low albumin & mild anemia
what clinical signs are associated with small strongyles causing chronic diarrhea?
weight loss, diarrhea, colic, & edema
what is the pathophysiology of small strongyles?
adult parasites feed on cecal & colonic mucosa causing irritation/hemorrhage
ingested L3 larvae migrate in the wall of the cecum/colon & encyst to induce inflammatory response
encysted larvae emergence - acute signs
how are small strongyles diagnosed? how are they treated?
fecal egg count
fenbendazole & moxidectin
what are the 4 types of inflammatory bowel disease?
- granulomatous enteritis
- eosinophilic enteritis
- lymphoplasmacytic enteritis
- lymphoma
how is IBD diagnosed?
diagnosis of exclusion - horse with a history of chronic weight loss with diarrhea/colic for weeks to months
may have a ravenous appetite & rectal exam may reveal thickened colon or enlarged lymph nodes
what may be seen on lab work of an IBD horse?
mild anemia, hypoproteinemia, peripheral lymphocytosis is rare
what may be seen on ultrasound of a horse with IBD?
thickened intestinal walls, increased peritoneal fluid, & enlarged lymph nodes
what are the pros & cons of using a rectal biopsy to diagnose IBD?
pros - easy to do
cons - low sensitivity, just because you don’t see it doesn’t mean it’s not present
what is the treatment used for IBD?
steroids - may relapse when discontinued
eventual euthanasia
a 5 y/o QH gelding broke into the feed shed & engorged himself on the mare/foal feed bag, eating almost all of it. now he has diarrhea, and you are icing the feet to prevent laminitis. which of the following is the most likely explanation for why this horse developed colitis?
a. clostridial difficile overgrowth
b. salmonella infection
c. colonic pH is acidotic
d. colonic pH is alkaline
c. colonic pH is acidotic
which diagnostic result listed below would be the most supportive of sand enteropathy in an adult horse?
a. history of living in a sandy environment
b. auscultation of the xiphoid & feeling like you’re at the beach
c. sand sedimentation seen in a fecal float within a rectal sleeve fingertip
d. abdominal radiographs with evidence of opaque material ventrally
d. abdominal radiographs with evidence of opaque material ventrally
how much water is secreted daily by the equine gi tract?
40% of body weight
what is the pathophysiology of grain overload causing diarrhea?
high carb load overwhelms the small intestines ability to process/absorb them so an increased amount enters the large intestines
increase in the growth rate of the lactic acid producing bacteria and a dying off of gram-negative bacteria releasing endotoxins due to the overwhelming acid environment - causes acidotic pH in colon
