Equine Med- Acute diarrhea

wilsbach's version from 2016-02-22 17:45

Intro, Colitis (general)

Question Answer
what is the 1* sign of LI dz?DIARRHEA!
diarrhea occurs when the normal balance of...Normal balance of secretion & absorption in Large Intestines is disturbed--> inc water content in feces
how worried should you be about acute diarrhea?considered an ER!!!
what is Colitis?Active inflammation of the colon wall
what is the Cardinal sign of colitis?diarrhea BUT not all patients with colitis have diarrhea
Effector cell in acute colitis is?PMN (neuts)... Inflammatory mediators bring PMN to site of bacterial infiltration --> diarrhea
Colitis: Clinical presentation?Diarrhea!*, Colic / Fever, Dehydration / hypovolemia, Abdominal distention, Depression, +/- anorexia, Injected mucosal membranes, Endotoxemia, LAMINITIS
how will colitis present with rectal exam?fluid in colon
how will colitis appear on US?swirling fluid within colon/cecum
what are the 4 MAJOR HINTS that you are probably looking at colitis on your bloodwork?Neutropenia with left shift, Hypoproteinemia (inflamed wall), metabolic acidosis (bc hyperlactatemia), Hyponatremia
what will colitis look like on the CBC?Increased PCV, Neutropenia with left shift (bc acute-- not that many neutrophils avail, and all young neutrophils ), Hypoproteinemia (inflamed colon wall), Hyperlactatemia (poor perfusion)--> metabolic acidosis
what is biochem like for colitis?Hyponatremia, Hypokalemia, Hypochloremia, azotemia
6 major DDX for Acute Diarrhea?Salmonella spp (acute and chronic), Clostridium spp., Antimicrobial associated, Potomac Horse Fever, Blister Beetle Toxicosis, Grain Overload
7 (4 we care about and are gonna talk about) DDX for chronic diarrhea?Salmonella spp (acute and chronic), Sand enteropathy, NSAID toxicosis, Parasites, (IBD, Neoplasia, periotnitis)
how can you get a definitive diagnosis for colitis?May be difficult to achieve.. can try: Fecal bacterial cultures, look for Presence of bacterial toxins in feces, do PCR. (Use of Signalment / History / Time of the year!!!)
why do colitis cases have an acidosis?poor perfusion to gut--> produce lactate--> dec pH
what should you in your fluid therapy plan for a colitis case?Dehydration, electrolyte loss & acidosis, Crystalloid + colloid /plasma in case of hypoproteinemia
what are three options you can choose for Anti-endotoxemic therapy?“NSAIDs” (flunixin pretty sure), Equine Plasma, Polymixin B
you should be careful using polymixin B as anti-endotoxemic therapy because _________can hurt horse kidneys
how do you provide laminitis prophylaxis for a horse with colitis?cryotherapy (laminitis risk with possible endotoxemia/ inflammation)
what are some Oral anti-diarrheal agents you might consider for a horse with colitis?Bismuth subsalicylate, DTO-Smectite, Probiotics, Psyllium
3 major complications of colitis?(1) Laminitis (bc endotoxemia) (2) Thrombophlebitis (bc gonna be using catheters) (3) Coagulopathy (prolly something to do with inflammatory factors)
Treatment of Acute Colitis?Discontinue current antibiotic treatment! Then start Metronidazole, as well as Additional supportive care (fluid therapy) and Prophylaxis therapy for laminitis (cryotherapy), an NSAIDs, plasma, Polymixin B (to tx for possible endotoxemia)

Acute diarrhea- Salmonella, Clostridium spp, Antimicrobial associated diarrhea

Question Answer
Salmonellosis--> which serovar is most common in horses?S. Typhimurium most common in horses
how does salmonella affect the cells of the GI? (3 things and their direct effects)(1) Alters mucosal cell function--> Morphological damage & altered permeability. (2) Enterotoxin--> Secretory component through cAMP. (3) Intestinal wall inflammation--> edema, migration of neutrophils
how does the enterotoxin of salmonella affect the GI?causes Secretory component through cAMP
what might bloodwork look like with a salmonella infection?severe neutroPENIA (remember this is acute so the WBCs all go to that site and arent in the blood)
what is the fastest and most sensitive way to dx salmonella?PCR of the feces
what must you keep in mind if you want to do a fecal culture for salmonella? Or testing the feces in general?(remember that PCR is the fastest and most sensitive way) Need to take >5 samples taken 24h apart or 3 PCRs negative (increases sensitivity) (so to be sure have neg or pos horse, need to take mult samples if you wanna do a culture. if first few samples neg, doesnt mean horse is neg, bc not always excreted. so at least 5 samples 24hr apart and THEN thats neg then you can exclude salmonella )
what is a Nosocomial infection? Who is most at risk for this? Implications?aka infection you get in a (veterinary) hospital. Salmonella most common in horses and presents a huge biosecurity risk: isolation!
what are some risk factors for the horse to develop salmonellosis?stress, hospitalization, diet change, sx, general anesthesia, antimicrobial use, small colon impactions
what are the two sp of clostridium which usually affect horses?Clostridium perfringens / difficile
what kinda organisms are Clostridium perfringens / difficile? Where are they usually found? Gram + spore-forming anaerobe. Part of normal intestinal flora / ubiquitous in environment
If clostridium are normal flora, why are they causing problems?Take advantage of an imbalanced gut: overgrow & colonize (imbalance usually from stress, immunosuppression, or ABX therapy which alter normal flora.)
what is the main thing clostridium sp do to cause acute diarrhea?(perfringens and difficile) Produce toxins--> hypersecretory diarrhea
what kinda diarrhea is caused by clostridium?hypersecretory (toxin)
which kinda diarrhea is caused by salmonella?secretory (enterotoxin)
so if clostridium is always around in the gut, how do we know if the clostridium is causing the problem, or if it is something else?try to detect the TOXINS which are causing the problem which are produced by the clostridium
what is happening in Antimicrobial associated diarrhea? Antimicrobials can disrupt the normal intestinal flora
please don't forget where diarrhea comes from in horsescolon not sm int
what are the antimicrobials most associated with colitis in adult horses? (and what routes?)(1) MACROLIDES: Erythromycin / Azythromycin / Clarithromycin po (famous for causing diarrhea in horses). (2) TMPS po (3) Ceftiofur iv (4) Oxytetracycline / Doxycycline (5) Neomycin………
what is interesting about the distribution of what drugs cause Antimicrobial associated diarrhea?There is a wide and distinct geographic distribution of what drugs cause a problem
what two PE findings might give you an indication its clostridium thats causing the acute diarrhea? Sight & smell
do you want to culture clostridium as a possible cause of diarrhea?eehhhh... Difficult and time consuming, Presence of bacteria is only suspect for cause of disease (they are normal flora!)
how can you Identify toxins from clostridium in the feces? (2 ways)(1) ELISA for enterotoxin A (so test directly) (2) PCR for genes that induce toxin A&B (test indirectly for genes)


Question Answer
Potomac Horse Fever is aka??Equine Monocytic Ehrlichiosis
what causes Potomac Horse Fever and how do horses get it?caused by Neorickettsia risticii an obligate intracellular bacterium. Carried by flukes that infect aquatic insects: usually affects horses grazing near fresh water during warm seasons
what is early versus late dz like for potomac horse fever?(1) Early dz: Infects and lives in monocytes. Causes morphologic damage in LI due to Mononuclear infiltration in lamina propria . (2) LATE dz: Fibrinous necrotizing typhlocolitis --> Severe mucosal ulceration
what is a common sequelae to PHF? Severe LAMINITIS
neorickettsia risticii first goes into ____ to do ___ to the GI, and then eventually _________ happensin early dz infects monocytes---> infiltrates lamina propria. Then eventually there is Fibrinous necrotizing typhlocolitis--> severe mucosal ulceration
what are the clinical signs you can see with PHF? Infections may be subclinical!! You can see: Diarrhea 60% cases, Laminitis 30% cases, Abortion syndrome
what are three ways to dx PHF?(1) Presumptive in endemic areas (areas surrounding the Potomac River northwest of Washington, D.C) (2) serology (3) PCR ( (4) culture is possible but difficult)
how can you use serology to dx PHF? Paired titers (2 weeks apart) , seroconversion (4 fold increase)
if you want to look for PHF with PCR, what samples do you wanna look at? antigen in blood / feces (makes sense, in monocytes and in GI)
can you culture PHF?possible but difficult
**how do you tx PHF?INTRACELLULAR BACT= OXYTETRACYCLINE ( 6.6mg/kg IV q 24 hours x 5 days, 100mg/ml solution, Dilution required)-- also Additional supportive care & prophylaxis for laminitis
what are the 2 most common complications of a PHF infection?Laminitis / abortion most common complications
what might help in the prevention of PHF? Decrease standing water may help
is there vx for PHF? Several vaccines available but Poor efficacy bc of antigenic variation
prog of PHF? Case fatality rates= 5-30%
Pic of what blister beetles look like
CANTHARIDIN TOXICOSIS is aka?Blister Beetle Toxicity
what kinda horse food are blister beetles attracted to-- how do they end up in the food? Blister Beetles attracted to alfalfa plants --> Get baled in hay and crushed during crimping
what is the blister beetle toxin?cantharidin
how many beetles need to be eaten for CSs to show?4 beetles enough to cause clinical signs
once ingested, what is the pathophys of blister beetle toxin?(cantharidin).. Absorbed by GI tract, excreted in urine. Acts as mucosal vesicant (blister causing agent)
what are the clinical signs of CT?Clinical signs reflect mucosal irritation--> Oral (salivation), GI (Colic & diarrhea), Urinary tract (hematuria, stranguria) ulceration, Significant decrease in Ca++ & Mg++. (GI bc ingested and urinary bc excreted through kidneys.)
dx of CT? Identify beetles in hay, HPLC (High-performance liquid chromatography) ID of the toxin (urine or gastric content)


Question Answer
which things get digested where in the equine GI tract?
In essence, grain overload is because of ... (explain pathophys)Inappropriate pre-cecal digestion: They eat a BUNCH of grain, so then Not enough amylase production in SI to break it all down, so Too much CHO passed to cecum--> Proliferation of certain microflora populations--> those microflora create products which dec cecal pH--> Altered pH impairs normal microflora!!!!
what are the microflora that really like grain, and what are their products which drop the pH of the cecum?MICROFLORA: Bacillus / Lactobacillus / Streptococcus. PRODUCTS: Lactate / Proprionate---> these drop the pH and impair normal flora from working, making a vicious cycle
what is the end results of grain overload?(bc of drop in pH) Decreased fermentation, Cecal / colonic dysmotility --> gas distention, Colic pain + laminitis
what are the clinical signs of grain overload?Colic, Gas distention / bloat, GI ileus, Endotoxemia, diarrhea
what can you do to tx grain overload in the early stages? later stages?If early enough, gastric lavage. Otherwise, Mineral oil / charcoal (via NGT), Anti-endotoxemic therapy, ***** Laminitis prophylaxis, Severe gas distention may lead to dyspnea, in which case Cecal trocharization may be performed