Equine entero- typhlo-colitis pt 1 Flashcards
what is the volume of the equine stomach?
length and volume of small intestine?
length and volume of cecum?
length and volume of large colon?
stomach: 8-16L
small intestines: 50-80L, 25-30m
cecum: 30L, 1.5-2m
large colon: 80-120L, 3-4m
enteritis / typhlitis / colitis
- clinical signs, general
- Lethargy
- Inappetence
- Colic
- Fever
- Diarrhea
enteritis / typhlitis / colitis
- general diagnostic tests
- Bloodwork
- US
- Transrectal palpation
- Pathogen testing
diarrhea leads to fluid loss
- what are 3 consequences of this?
- Dehydration
- Hypovolemia
- Decreased blood pressure
diarrhea leads to electrolyte loss
- what are 3 consequences of this?
Arrhythmia
Weakness
Ileus
colon inflammation leads increased capillary permeability, which leads to protein loss
- what are some consequences of protein loss
- Edema (internal and external)
- Catabolic State
colon inflammation leads increased capillary permeability, which leads to bacterial translocation
- what problems can this cause?
Laminitis
Thrombosis
Fever
Ileus
Sepsis
Endotoxemia
minimum amount of fluid loss for clinical signs
Dehydration – minimum of 5% to have clinical signs
general signs of >5% dehydration?
Tachycardia
Dry, pale mucus membranes
Prolonged CRT
Lethargy
Cold extremities
Poor peripheral pulse quality
Prolonged jugular refill
Prolonged skin tent
Sunken eyes
Reduced urine output
what will edema due to colitis look like grossly and on ultrasound?
- External or internal
- Thickened colon wall on ultrasound
- Ventral edema
- Preputial edema
- Rectal prolapse
acute colitis venous blood gas results?
- ↑ Lactate
- ↓pH
- ↓ Sodium
- ↓ Chloride
- ↓ Potassium
- ↓ Calcium
acute colitis CBC results?
- Leukopenia – neutropenia (Except Potomac Horse Fever)
- Left shift
- Hemoconcentration
acute colitis biochem results?
- Azotemia
- Hypoproteinemia
bacterial agents that can cause colitis
Salmonella
Clostridium difficile
Clostridium perfringens
Neorickettsia risticii
parasitic agents that can cause colitis
Larval cyathostomiasis
toxic agents that can cause colitis
- NSAID use: extra dose or extended therapy
- Antibacterial therapy
- Cantharidin
dietary factor that can cause colitis
Carbohydrate overload
- cost of an acute colitis case?
- % referred?
- % undifferentiated?
- % mortality
- Cost: 4-6.000$
- 10% referred
- 60-80% undifferentiated
- 30% mortality
the one bacterial agent that causes a colitis with neutrophilia in the horse
Neorickettsia risticii
Potomac Horse Fever
- agent, disease description
- bacteria characteristics
- incubation
Neorickettsia risticii (formerly Ehrlichia risticii)
* Equine monocytic erlichiosis
Family Rickettsia
Gram-negative intracellular bacteria Incubation period: 10-14 days
PHF – Clinical signs
In order of importance / frequency:
1. Lethargy
2. Anorexia
3. Fever
4. Diarrhea
5. Laminitis > 30-40%
6. Colic
PTH transmission
trematode egg eaten by freshwater snail
> trematode egg develops into cercariae
> leaves snail, moves into aquatic insect, becomces a metacercaria
> aquatic insect with bacteria-containing trematode metacercaria is ingested accidentally by the horse, while it is eating or drinking (usually in a swampy area)
> natural life cycle would be insect ingestion from bird
PHF - pathogenesis
- what cells and what anatomic locations are affected?
- Following ingestion of aquatic insect:
- N. risticii multiplies within:
monocytes
macrophages
mast cells
intestinal epithelial cells of the horse - Colon, small intestine
PHF – risk factors, geography
- Seasonal distribution (June-September)
- Horses grazing pastures bordering waterways (freshwater rivers, lakes, creeks, irrigation ditches)
<><> - Geographical distribution:
Canada, USA, Brazil, Uruguay, France, The Netherlands, India
PHF – diagnostics? which is best?
PCR
- can use blood or feces (prefer both due to different timelines)
> detectable in blood 10-25d post infection
> detectable in feces 13-28d post infection
<>
* Culture (we don’t do this)
> Requires special culture techniques
> Takes weeks
<>
Indirect fluorescent antibody assay (also don’t do this)
- Antibody level rises early in disease
- Difficult to get an early 1st sample
- Single sample not regarded as diagnostic
PHF - treatment
- Oxytetracycline: IV q12-24h 3-5 days
EARLY cases: respond within 12h
Does not interfere with antibody production
<><> - IV fluids
- IV plasma
- NSAIDs (e.g. flunixin – careful for AKI!)
<><> - Laminitis prevention (ice boots, etc.)
PHF - vaccination
- type and schedule
- effectiveness
- Inactivated (killed) vaccine
- Early spring or summer
<><>
AAEP - Primary vaccination: 2 doses 3-4 weeks apart
- Revaccinate at 3-4 month intervals
- Peak protection 3-4 weeks
<><> - Experimental results with vaccine were mixed
- Duration of immunoprophylaxis was very
limited - Different strains
PHF - prevention strategies
- Vaccinate (consult your veterinarian)
- Decrease exposure to aquatic insects
> Especially June-August
> Keep horses in barn at night
> Restrict grazing near creeks, rivers - Turn off barn lights in peak insect season
- Keep hay and water covered at night
If a horse has diarrhea on TMS (or any antibiotic) what should we do?
- discontinue immediately, and then make a plan
Antimicrobial associated diarrhea
- cause?
- what pathogens may contribute?
- Not as clear cut as in humans – lack of case definition
<> - Pathogens may contribute – subdivision
> C. difficile (up to 25% in humans)
> C. perfringens
> Salmonella
<> - 22-94% of colitis cases depending on studies
Antimicrobial associated diarrhea
- do we know if some antimicrobials are riskier than others?
- which ones?
- which have been experimented with?
- route of admin matter?
- No studies of relative risks of certain classes of antimicrobials, BUT
> we know which have an effect: - Depends on effect on enteric anaerobes:
- Little effect: TMS, Fluorquinolone, Aminoglycoside
- Big effect: Lincosamide, macrolide, beta lactam
> In mares with foals treated with macrolides!
<><> - Used experimentally to induce colitis: clindamycin, lincomycin, oxytetracycline, erythromycin
- Equal or increased association with parenteral antibiotics
possible sequelae of antimicrobial induced diarrhea
Case from PM at OVC:
- death most likely due to the compromise of the colic wall resulting in the release of feed material to the peritoneum and causing septic peritonitis and adhesions
