Exam 3: Diarrhea in Horses

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52 Terms

1

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

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2

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

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3

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

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4

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

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5

what diagnostics should all acute diarrhea cases hav

  • CBC

  • chem

  • venous blood gas

  • blood lactate as prognostic indicator

  • abdominal ultrasound

  • fecal testing

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6

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

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7

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

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8

how does colitis present on chemistry

  • hyponatremia

  • hypochloremia

  • hypokalemia

  • hypocalcemia

  • metabolic acidosis

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9

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

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10

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

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11

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

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12

what are infectious causes of colitis in adult horses

  • salmonella

  • clostridium

  • Neorickettsia risticii

  • parasites (strongyles)

  • coronavirus

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13

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

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14

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

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15

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

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16

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

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17

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

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18

what are the toxins of salmonella

  • cytotoxin- damages cells and alters permeability

  • exotoxin- causes intestinal hypersecretion

  • endotoxin- severe intestinal inflammation

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19

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

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20

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

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21

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

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22

what is the pathogenesis of C. difficule

  • toxin producing strains, A and B

  • mucosal damage causing necrosis, intestinal inflammation

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23

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

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24

how is C. difficile diagnosed

  • fecal toxin detection

  • fecal PCR

  • NO CULTURE

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25

what are the important types of C. perf in horses

  • Type A

  • Type C

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26

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

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27

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

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28

ho is C. perf diagnosed

  • fecal toxin detection

  • Fecal PCR panel to detect toxin producing genes

  • NO CULTURE

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29

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

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30

what is the epidemiology of Potomac Horse fever

  • serology is not reliable

  • seasonal- May to november, peaks mid to late summer

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31

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

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32

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

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33

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

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34

generally describe equine coronavirus

  • RNA virus

  • sporatic cause of diarrhea in adult horses

  • fecal oral

  • disease usually occurs during cool months

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35

what are the clinical signs of equine coronavirus

  • usually resolve in 2-4 days

  • anorexia, lethargy, fever most common

  • colic, diarrhea, neurological signs

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36

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

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37

what antibiotics should NEVER be given to adult horses

  • Clindamycin

  • Macrolides

  • Lincomycin

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38

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

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39

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

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40

define right dorsal colitis

  • unknown why NSAIDs have preference for this spot

  • high or low doses, long or short term use

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41

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

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42

how is right dorsal colitis diagnosed

  • often presumptive based on history

  • bloodwork may show anemia, hypoproteinemia, hypoalbuminemia, hypocalcemia

    • ultrasound

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43

how does parasitism typically present

  • chronic weight loss or chronic diarrhea

  • L3 larva can damage the intestinal all and cause intestinal inflammation

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44

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

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45

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

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46

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

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47

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

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48

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

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49

how is canthardidin tox diagnoed

  • chemistry will show azotemia, extremely decreased calcium, decreased magnesium, decreased protein

  • UA shows hematuria

  • tox testing

  • examine hay source

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50

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

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51

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

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52

how do you diagnose sand enteropathy diagnosis

  • auscultation for sand sounds

  • abdominal rads

  • fecal sand test in rectal sleeve

  • rule out

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