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what is the most common sertype of salmonella to infect the horse?
S. typhimurium (no enteric host adapted species in horse)
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Salmonella has zoonotic potential, 1 in 17 healthy horses are shedding, and it has established resistant infections in hospitals. which horses are more susceptible to infection?
- young (foals more likely to become septic)
- old and sick
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what is pathophysiology of disease caused by salmonella?
bacteria invade mucosa - engulfed by macrophages - prod. toxin that damages mucosal barrier and Na/Cl secrete into lumen - inflammatory response and can be absorbed into blood stream
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what are the most common signs associated w/salmonellosis?
- fever
- endotoxemia
- diarrhea (may be absent or in small amounts)
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how is salmonella diagnosed? when is horse considered unlikely to be shedding?
- PCR of feces, tissue or body fluid (blood in foals)
- bacterial culture
- 5 neg fecal cultures or 3 neg PCRs taken 24 hr apart
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what worsens prognosis for salmonella patient?
- prolonged diarrhea or sepsis
- fibrin formation - adhesions - irreversible/poor absorption/damaged mucosal barrier
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what are signs a patient being kept in hospital has developed salomella infection?
- decr. appetite and attitude
- elevated PCV w/low TP (PLE and dehydration)
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what kind of bacteria is clostridium? which species are problematic in the horse? when?
- gram +, spore forming rod, anaerobic (normal intestinal flora)
- C. perfringens and C. difficile (when stressed, immunosuppressed, Ab-induced)
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which antibiotics are more likely to cause diarrhea/disrupt intestinal flora? which Ab should NEVER be used in horses?
- erythromycin, neomycin
- TMS
- ceftiofur
- ampicillin
- never use Lincomycin
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any antibiotic can cause diarrhea in horses so what are signs that problems are arising?
- decr. appetitie/attitude
- mild fever
- decr. water intake
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how do you test for clostridium? what type of diarrhea is often seen w/clostridium infection?
- ELISA for c. difficile toxins A and B
- PCR, cytotoxin assay
- culture from feces (inferior test)
- hemorrhagic diarrhea
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how is clostridium treated? prognosis?
- metronidazole
- DTO-smectite/biosponge (binds toxins)
- laminitis prophylaxis
- high mortality
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what is causative agent of Potomac Horse Fever? which cells does it infect? which seasons are associated w/disease?
- neorickettsia risticii - carried by aquatic flukes
- late summer, early fall (warm water)
- trophism for monocytes and enterocytes
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clinical signs of PHF are similar to salmonella and clostridium, but what other sign can be noted in late disease?
abortion
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how is PHF diagnosed? treatment?
- PCR on blood or feces; paired serology titer
- Oxytetracycline (dilute/NO bolus- avoid chelation of Ca - heart stop)
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what are the 2 most common complications associated with PHF? is there a vaccine available?
- laminitis and abortion
- vaccine exists but don't use it, not efficacious
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what is cause of cantharidin toxicosis?
- blister beetles contain this toxin; often encountered in alfalfa hay - mucosal irritant
- 4-5 beetles = signs within hours
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what other organ system is affected by blister beetles?
- GI + *renal* (hematuria, stranguria) + oral ulceration (salivation)
- myocarditis may also be present
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what is the most distinguishing feature of blood work of cantharidin toxicosis patient?
- *hypOcalcemia* (and hypomagnasemia) so incr. TPR
- synchronous diaphragmatic flutter/thumps
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what is treatment and prognosis for cantharin toxicity?
- no specific antidote, supportive care
- mineral oil to help evacuate
- poor; mortality >50% (if survive first couple days, prog. improves)
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how does grain overload cause colitis?
not enough amylase to digest high CHO load - undigested CHO reaches colon - bacillus/lactobacillus/strep proliferation - prod. lactate and proprionate - acidic pH - decr. fermentation/motility and laminitis
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what are presenting signs of grain overload?
- severe colic pain
- endotoxemia
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what is treatment for grain overload?
- gastric lavage if caught early
- mineral oil via NGT
- anti-endotoxemic therapy; laminitis prophy
- trocharize cecum to relieve distention (right side)
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feeding how many kg of oats/day will increase risk? what is recommended amount to feed per meal?
- >2.7kg of oats/day
- feed <2g/kg of body weight per meal
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Horse in Michigan is seen laying down more and passing normal consistency feces then watery diarrhea. What is likely diagnosis? what do you expect peritoneal fluid to be?
- sand enteropahty
- normal fluid; careful not to penetrate colon when collecting!
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what would US show with sand colitis?
stretched colon so loss of haustra
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how is sand colic treated if only mild signs present?
- over hydrate w/oral and IV fluids
- NSAIDs + analgesia
- psyllium (metamucil) to encourage movement over time
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what should be done for sand colic patient that is not responding to therapy?
- surgery to remove sand - pelvic flexure enterotomy
- cecal trochar prior to sx to improve respiration/venous return
- (if sand in R dorsal colon, cant exteriorize, more difficult)
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what is the difference between cox 1 and cox 2?
- cox 1: consistently being produced; maintain mucosa
- cox 2: inducible during pain/injury - inflamm. mediators
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where is NSAID damage most likely to occur? what dose is considered excessive? which NSAID in particular is dangerous?
- right dorsal colon
- >8.8 mg/kg/day in face of water deprivation (lesser doses can cause problems too)
- phenylbutazone
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what is diet treatment for right dorsal colitis?
- pelleted feed, no long stem fibers
- corn oil
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what other supportive care things can be done to treat right dorsal colitis?
- may require colloids
- synthetic prostaglandins
- psyllium to promote movement of ingesta
- opioids + Lidocaine CRI
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Cyathostomes infect the large intestine. What is their life cycle?
- ingest L3 - migrate into cecal/colonic mucosa - go back into lumen as L4 after 5-6 weeks
- OR L3 can encyst in mucosa for months - when excyst release inflammatory products (end winter/early spring)
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what are clinical signs of acute cyathostome infection?
severe diarrhea, rapid wt. loss and marked hypoproteinemia; passing larva in feces
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what are clinical signs of chronic cyathostome infection?
- *wt. loss*
- chronic diarrhea (so no CV deterioration or volume depletion)
- intermittent colic
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cyathastomes have resistance to which drug?
benzimidazoles
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what are the 2 licensed products for treatment of cyathastomes? how is successful treatment determined?
- fenbendazole (power pack)
- moxidectin (quest)
- >90% reduction in FEC after 1 wk therapy
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what drug can be given to PREVENT mucosal invasion of cyathastomes?
daily pyrantel tartrate
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