Antimicrobial therapy in horses (Proceedings)


Antimicrobial therapy in horses (Proceedings)

Case-based presentation
Apr 01, 2008


  • 7 yr, American Saddlebred, Gelding
  • Show horse, pleasure riding. Current light work schedule.
  • Current vaccination for West Nile Virus, EEE, WEE, PHF, Influenza, EHV1 and Tetanus.
  • Ivermectin q8wks for parasite control.
  • Diet: 5lbs 12% sweet feed BID, free choice grass hay
  • Housing: Stall, limited individual pasture turnout
  • 2004: R eye trauma – corneal laceration & perforation, subsequent blindness & pthisis bulbi
  • Intermittent bilateral forelimb lameness associated with foot conformation (club foot L fore) and sole bruising 1gm Phenylbutazone q24h for 6 days prior to presentation
  • No abnormalities noted by the owner the evening prior to presentation
  • 8am: No abnormalities noted, exercise (light riding), groomed, stall confined and fed normal ration.
  • 10am: Found recumbent, depressed, sweating, owners unable to get horse to stand. Referring vet contacted
  • 12pm: Referring vet examination

Referring Vet Examination

  • HR 110, RR 60, Temp 101.5°F
  • MM injected with a toxic line, CRT 3s
  • Sunken L eye, prolonged skin tent test
  • Skin and distal extremities cold to touch
  • Decreased digital pulses in all limbs
  • Decreased gut sounds all quadrants, no gastric reflux, no abnormalities on rectal examination
  • Profuse watery diarrhea

Treatment: Procaine penicillin IM 20000 IU/kg, Gentamicin IV 6.6 mg/kg, lactated Ringer's solution 7L IV

Referred to VTH

Examination at 6pm

  • HR 72, RR 42, Temp 101.4
  • MM purple, tongue cyanotic, CRT 3s
  • Bilateral serous nasal discharge
  • Depressed, sweating
  • Decreased GIT motility all quadrants
  • Profuse watery diarrhea
  • Shifting weight in all limbs, increased digital pulses all limbs
  • Decreased jugular fill
  • Increased thirst, decreased appetite

Abdominal ultrasound:

  • left dorsal colon wall thickness 0.2mm
  • right dorsal colon wall thickness 0.4mm
  • fluid filled colon and small intestine

Nasogastric intubation:

  • no reflux

Problem list:

  • azotemia
  • dehydration
  • hypochloremia, hyponatremia, hypocalcemia,
  • hyperphosphatemia
  • hypoalbuminemia
  • leukopenia, neutropenia
  • diarrhea
  • suspected decrease in blood pressure & peripheral perfusion
  • laminitis

Differential diagnosis:

  • Phenylbutazone associated right dorsal colitis
  • PHF
  • Salmonella
  • Clostridial colitis
  • Endotoxemia