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describe a complete history for adult horse diarrhea
vaccination
deworming
drug administration
presence of other clinical cases on the farm
previous cases of Salmonella or PHF
types of feeds
changes of feed
duration of signs
what are the common clinical signs that go with diarrhea
remember that severe acute diarrhea is a medical emergency
lethargy
fever
colic
anorexia/hyporexia
clinical signs of endotoxemia → tachycardia, tachypnea, abnormal MM
deydration
abnormal GI auscultation
how is colic described generally
inflammatory mediators associated with colitis can stimulate pain receptors
some horses with diarrhea can develop ileus, may cause intestinal distension with fluid and can lead to NG reflux
abdominal discomfort in a diarrhea case is usually transient, pain gives way to profuse diarrhea
describe the possible clinical signs with colitis
typical = fever, depression, and signs of endotoxemia usuall precede diarrhea by 2-5 days
sometimes diarrhea never occurs in colitis patients that have minimal damaged mucosa
in a few severe cases, severe acute shock and death occur before clinical signs in diarrhea are seen, called colitis X
what diagnostics should all acute diarrhea cases hav
CBC
chem
venous blood gas
blood lactate as prognostic indicator
abdominal ultrasound
fecal testing
what diagnostics may be used in select cases of acute diarrhea
abdominocentesis if peritonitis is suspected
NG intubation if abdominal pain
rectal palpation if horses is distended and painful
how does colitis present on CBC
increased PCV
neutropenia that may be followed by neutrophila
left shift and toxic changes
fibrinogen mild hyper with severe colonic inflammation
how does colitis present on chemistry
hyponatremia
hypochloremia
hypokalemia
hypocalcemia
metabolic acidosis
how does azotemia present with colitis
pre-renal azotemia in most cases due to dehydration and hypovolemia
renal azotemia caused by acute hemodynamic renal failure
-can occur with prolonged entotoxemic hypotension and hypovolemia, esp if patient has received NSAIDs or aminoglycosides
how does total protein change with colitis
normal = fluid losses are absent or minor
increased when fluid losses only
decreased when substantial colon damage causes protein loss, with acute diarrhea indicates a guarded prognosis
how is abdominal ultrasound used for colitis
examine the large intestines for edema and thickness
evaluate motility
-fluid filled colon and cecum typically noted
eamine peritoneal fluid quality and quantity
what are infectious causes of colitis in adult horses
salmonella
clostridium
Neorickettsia risticii
parasites (strongyles)
coronavirus
what are non-infectious causes of colitis in adult horses
toxic (NSAIDs, cantharadin, heavy metals)
nutritional (carbohydrate overload, lush forage, sudden change in diet composition)
sand enteropathy
IBD, neoplasia, organ dysfunction
how is chronic diarrhea defined
diarrhea of greater than 2 weeks duration
results from disease of the large intestines, though many also affect small intestines resulting in weight loss
greater diagnostic challenge
usually fluid and electrolyte loss less of a problem
what is the organism that causes equine salmonellosis
THE most important infectious cause of colitis in horses
family Enterobacteriacae
gram negative facultative anaerobic rod
flagella = motile
surface pilli = adheres to surfaces
what are the four syndromes caused by equine salmonellosis
severe acute diarrhea
mild infections
bacteremia/septicemia
asymptomatic +/ shedding
after infection, horses shed for 3 weeks to months
what is meant by salmonella being invasive
causes severe mucosal and interstitial damage
attaches to intestinal epithelial cells
injects signaling proteins into cell causing forced entry
escapes destruction once inside the cell
invades intestinal macrophages to be spread systemically
what are the toxins of salmonella
cytotoxin- damages cells and alters permeability
exotoxin- causes intestinal hypersecretion
endotoxin- severe intestinal inflammation
what are the risk factors for equine salmonellosis
age- neonates
stress such as prolonged transport, heat exposure, abdominal surgery
alterations in enteric microflora such as antibiotics, diet changes, fasting, colic
other disease, especially respiratory disease where antibiotics may be used
how is salmonella diagnsed
5 fecal cultures all 24hrs apart from each other is the gold standard, but is slow
fecal PCR is more rapid but risk of false positive and cannot rune sensitivity
how is C. difficile in horses generally defined
can be cultured in healthy horses without disease
important cause of antibiotic-associated diarrhea
ANY antibiotic use can cause this kind of colitis
what is the pathogenesis of C. difficule
toxin producing strains, A and B
mucosal damage causing necrosis, intestinal inflammation
what are the risk factors for C. difficile
mare with a foal being treated with antibiotics for R. equi
hospitalization, including exposure to contaminated environment, change in diet, surgical fasting, antibiotic therapy
how is C. difficile diagnosed
fecal toxin detection
fecal PCR
NO CULTURE
what are the important types of C. perf in horses
Type A
Type C
describe C. perf type A in horses
predominant type ID in normal and diarrheic horses
alpha toxin with potent hemolytic properties
causes bloody diarrhea, rapid death without outward diarrhea
Beta-2 toxin and CPE toxin ma also play a role
describe C. perf type C in horses
can cause severe diarrhea, sepsis and death in newborn foals
some foals die before onset of diarrhea
beta toxin is necrotizing that forms membrane pores in GI cells
causes necrotizing enterocolitis
can cause death from absorption of toxins from intestines into the blood
ho is C. perf diagnosed
fecal toxin detection
Fecal PCR panel to detect toxin producing genes
NO CULTURE
describe the organism that causes Potomac horse fever
Neorickettsia risticii
gram negative rickettsial bacteria
obligate intracellular organism
complex life cyctle
infe ts colonic macrophages and monocytes
what is the epidemiology of Potomac Horse fever
serology is not reliable
seasonal- May to november, peaks mid to late summer
generally describe N. risticii
definitive host thought to be trematode flukes
infected flukes parasitize many different intermediate hosts such as snails, insects, insectivores, non-equine mammals
describe the transmission and pathophysiology of N. risticii
ingestion of insects, snails, or trematodes harboring the organism
patho is poorly understood, but has predilection for the cecum and large colon, direct contact with contaminated feces not likely a major route of transmission
how do you diagnose Potomac Horse fever
PCR is test of choice, but must be collected BEFORE antibiotics
-fecal sample may be fridge not frozen
-post mortem = fresh or formalin fixed colon tissue
serology is not reliable
generally describe equine coronavirus
RNA virus
sporatic cause of diarrhea in adult horses
fecal oral
disease usually occurs during cool months
what are the clinical signs of equine coronavirus
usually resolve in 2-4 days
anorexia, lethargy, fever most common
colic, diarrhea, neurological signs
how is equine coronavirus diagnosed
fecal PCR is test of choice, 4 days after infection,duration of shedding 11 days
chemistry for hyperammonemia iin horses with neurological signs
what antibiotics should NEVER be given to adult horses
Clindamycin
Macrolides
Lincomycin
what is the pathophysiology and diagnosis of antimicrobial associated diarrhea
disruption of normal intestinal microflora
allows pathogens to overgrow
dx with history of antibiotic therapy
how is NSAID associated colitis defined
one of the clinical syndromes of NSAID toxicity
all NSAIDs are capable of causing colitis, Phenylbutazone most likely
overdose most common in ponies and foals
define right dorsal colitis
unknown why NSAIDs have preference for this spot
high or low doses, long or short term use
what are the clinical signs of right dorsal colitis
lethargy
decreased appetits
colid
diarrhea
± tachycardia, tachypnea, dehydration, weight loss
ulceration throughout GI tract, mouth, esophagus and or right dorsal colon
how is right dorsal colitis diagnosed
often presumptive based on history
bloodwork may show anemia, hypoproteinemia, hypoalbuminemia, hypocalcemia
ultrasound
how does parasitism typically present
chronic weight loss or chronic diarrhea
L3 larva can damage the intestinal all and cause intestinal inflammation
what are possible causes of parasitism in horses
Cyathostomes (small strongyles) are more common due to resistance
large strongyles are less common and largely eradicated by ivermectin
describe larval encysting in parasitism
some L3 larva that penetrate the gut wall encyst → hypobiosis
encysted larvae can simultaneousl mature and emerge from the colon at once with certain environmental cues
leads to massive release of inflammatory mediators → acute diarrhea/colitis
how is parasitism diagnosed
no antemortem method to diagnose encysted cyathostomes
fecal egg counts may or may not be increased
do fecal egg counts as a part of herd parasite program
-if 10% of herd >200epg → indicate a high level of pasture contamination
what is the pathogenesis of cathardin GI tox
toxic to mucosal cells of the intestine
excreted by the kidney and damages kidney and mucosa of bladder an urethra
what are the clinical signs of cantharidin tox
gastroenteritis causing colic and severe diarrhea
oral ulceration
AKI
mycardial necrosis causing arrhythmia
ulcerative cystitis causing hematuria
synchonous diaphragmatic flutter due to low calcium
how is canthardidin tox diagnoed
chemistry will show azotemia, extremely decreased calcium, decreased magnesium, decreased protein
UA shows hematuria
tox testing
examine hay source
describe carbohydrate overload
sudden increase in consumption of readily digestible CHO, accidental or intentiona
leads to change in colonic microflora
-CHO fermentation in the hindgut → osmotic diarrhea
-increases lactic acid producing bacteria in the large intestine
-lactic acid decreases GI pH which also damages colonic epithelium and leads to mucosal inflammation
what is sand enteropathy
horses consuming small amounts of sand over a long period of time and accumulates in the colon
can cause impaction and chronic diarrhea
how do you diagnose sand enteropathy diagnosis
auscultation for sand sounds
abdominal rads
fecal sand test in rectal sleeve
rule out