C. perfringens and C. difficile (when stressed, immunosuppressed, Ab-induced)
which antibiotics are more likely to cause diarrhea/disrupt intestinal flora? which Ab should NEVER be used in horses?
never use Lincomycin
any antibiotic can cause diarrhea in horses so what are signs that problems are arising?
decr. water intake
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)
how is clostridium treated? prognosis?
DTO-smectite/biosponge (binds toxins)
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
clinical signs of PHF are similar to salmonella and clostridium, but what other sign can be noted in late disease?
how is PHF diagnosed? treatment?
PCR on blood or feces; paired serology titer
Oxytetracycline (dilute/NO bolus- avoid chelation of Ca - heart stop)
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
what is cause of cantharidin toxicosis?
blister beetles contain this toxin; often encountered in alfalfa hay - mucosal irritant
4-5 beetles = signs within hours
what other organ system is affected by blister beetles?
GI + *renal* (hematuria, stranguria) + oral ulceration (salivation)
myocarditis may also be present
what is the most distinguishing feature of blood work of cantharidin toxicosis patient?
*hypOcalcemia* (and hypomagnasemia) so incr. TPR
synchronous diaphragmatic flutter/thumps
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)
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
what are presenting signs of grain overload?
severe colic pain
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)
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
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?
normal fluid; careful not to penetrate colon when collecting!
what would US show with sand colitis?
stretched colon so loss of haustra
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
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)
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
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)
what is diet treatment for right dorsal colitis?
pelleted feed, no long stem fibers
what other supportive care things can be done to treat right dorsal colitis?
may require colloids
psyllium to promote movement of ingesta
opioids + Lidocaine CRI
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)
what are clinical signs of acute cyathostome infection?
severe diarrhea, rapid wt. loss and marked hypoproteinemia; passing larva in feces
what are clinical signs of chronic cyathostome infection?
chronic diarrhea (so no CV deterioration or volume depletion)
cyathastomes have resistance to which drug?
what are the 2 licensed products for treatment of cyathastomes? how is successful treatment determined?
fenbendazole (power pack)
>90% reduction in FEC after 1 wk therapy
what drug can be given to PREVENT mucosal invasion of cyathastomes?