Disease of the equine neonate pt 4 Flashcards
Infectious Diarrhea - Foals
- common agents
l Rotavirus
l Salmonellosis
l Clostridiosis
l Cryptosporidiosis
l Septicemia
l Rhodococcus equi
l Lawsonia intracellularis
l Strongyloides westeri
l Most common viral cause of diarrhea in foals
Rotavirus
pathogenesis of rotaviral diarrhea
Small intestine: invades villus epithelial cells → villus atrophy → crypt cell proliferation → ↑fluid secretion, malabsorption, maldigestion → diarrhea
rotavirus morbidity, mortality
l High morbidity, low mortality, farm outbreaks
- rotavirus affects foals of what age?
- Dx?
- how common in diarrheic foals?
- vaccine?
- Reported in foals 5-35 days of age, but older (>1mo) foals may be at increased risk
- Diagnosis by immunoassay or electron microscopy of feces
- Can be isolated in 20-40% of diarrheic foals
- Vaccine available – efficacy against field strains?
Salmonellosis - Foals
- how common?
- generally what type of syndrome?
- what type is problematic?
- shedding increased in what animals?
- Common pathogen in foals with GI disease
- More likely sepsis syndrome vs purely diarrhea
- Enteroinvasive Salmonellas (ie S. typhimurium) carry higher risk for bacteremia and sepsis
- Shedding is significantly increased in hospitalized foals with GI disease compared to hospitalized adult horses with GI disease (Ernst et al 2004)
Clostridiosis
- type of bacteria, characteristics, where found
l Gram positive bacilli
l Obligate anerobe to aerotolerant
l Spore-forming
l Spores are ubiquitous in environment
Clostridiosis
- most common types implicated
- common associations
- normal inhabitants of where?
- C. difficile and C.perfringens most common, but C. septicum, C. cadaveris, C. sordelli have also been isolated from horses with colitis
- Commonly associated with anti-microbial administration or nosocomial
- Normal inhabitants of GI tract in low numbers and non-toxin producing
Clostridiosis - Foals
- only found in sick?
- primary pathogen or opportunist
- type of C. perfringens most common? mortality rate?
- C. difficile prevalence?
- Can be isolated from both healthy and sick/diarrheic foals
- Can act as primary pathogen in foals
- C. perfringens – types A & C most common, C has significantly higher mortality rate
- C. difficile prevalence in healthy foals reportedly higher than adult horses
C. perfringens
- types and their toxins, what they do?
Types A, B, C, D, & E (classified by exotoxin)
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* A → α-toxin (phosphlipase C), disrupts glucose uptake/energy production & activates AA pathway in enterocytes
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* B & C → β-toxin (cytotoxin), enterocyte necrosis/ulceration
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* A & C → enterotoxin (cytotoxin), membrane pores in enterocytes, altered permeability, enterocyte necrosis, desquamation/inflammation etc
C. difficile
l 3 large toxins, what they do
- A → enterotoxin, recruitment/activation of PMNs → vasodilation, secretory, inflammatory response
<><> - B → cytotoxin (in vitro), interacts with toxin A
<><> - Binary toxin (cdT) → ADP-ribosylation, cytotoxic
<><><><> - Varying toxin profiles exist in pathogenic strains
Clostridiosis - Epidemiology
- risk factors
- spores
l Antimicrobials
l Hospitalization, stress, withholding roughage l +/-PPIs
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Spores are very persistent in environment
> 16.7% in veterinary hospitals
> more common on breeding farms vs. farms with only mature horses (Baverud 2002)
Clostridiosis - Diagnosis for C. perfringens
– fecal culture, enterotoxin ELISA (CPE), PCR for toxin production
Clostridiosis - Diagnosis for C. difficile
- what are the best tests?
– fecal culture, cytotoxicity tissue culture assay, toxin ELISA, PCR
- Approx 25% of isolates are non-toxin producing
- Cytotoxicity assay is gold standard
- PCR higher Sn & Sp than ELISA
Cryptosporidiosis
- agent characteristics
- symptoms
- apthogenesis
- shedding
- Dx
- Non-host specific protozoa, zoonotic
- Causes diarrhea in many species
- Invades enterocytes of distal SI → villus atrophy & fusion → malabsorption → diarrhea
- Oocyst shedding concurrent with diarrheic phase
- Diagnosis – sucrose wet mount of feces to identify oocysts
Cryptosporidiosis
- significance in foal diarrhea
- when is it found?
- Questionable role in foal diarrhea
- Has been isolated with similar frequency in healthy and diarrheic foals
- Co-infection with other putative diarrheal pathogens in foals with GI disease (Slovis et al 2013)
- More studies needed
Rhodococcus equi
- agent characteristics
- where its found, type of pathogen
- affects what age
- primary disease caused
- Gram positive pleomorphic coccobacillus
- First described (pneumonia) in foals in 1923
- Endemic in environment, opportunistic pathogen
- Affects foals 1-6 months of age
- Primarily bronchopneumonia, but extrapulmonary disease occurs in up to 74% of foals
Rhodococcus equi
- how often detected in diarrhea from foals?
- treatment connection with diarrhea?
- Variable detection in feces of healthy and diarrheic foals (8-14% in one study, Slovis et al 2013)
- Treatment with a macrolide & rifampin may also cause diarrhea
<><><><> - Role as a causative agent of diarrhea alone (without pulmonary signs)?
Proliferative enteropathy
- agent
- pathogenesis
- age affected
- Lawsonia intracellularis – obligate intracellular bacterium
- Apical cytoplasm of proliferative crypt epithelial cells in intestinal mucosa → chronic thickening and malabsorption with protein loss → diarrhea
- Foals affected at 3-7 months of age, onset of clinical signs has been associated with recent weaning
Proliferative enteropathy
- clinical signs
- Dx, ante and post mortem
- Depression, ill thrift, weight loss, edema, diarrhea, rough hair coat, potbelly appearance
- Severe hypoproteinemia/hypoalbuminemia, anemia, leukocytosis
- Antemortem diagnosis by fecal PCR, serology, signalment and clinical signs, exclusion of other causes of diarrhea
- Post-mortem diagnosis by silver stain of intracellular bacteria in crypt epithelial cells
Strongyloides westeri
- what is it?
- transmission?
- age affected?
- signs?
- Tx
- Common parasitic infection of foals
- Transmammary transmission
- Patent infection in foals by 8-12 days of age
- Generally mild diarrhea
- Treatment – deworming with benzimidazole or ivermectin
Strongylus vulgaris
- pathogenesis?
- when it causes problems
- Tx
- 4th stage larvae may cause diarrhea/colic in foals
- Migration through arterioles of cecum & descending colon
- Pre-patent period 6 months – not a cause of diarrhea in neonatal foals
- Treatment – appropriate deworming
Non-infectious Diarrhea - Foals
- causes, generally
- Foal heat diarrhea
- Antimicrobial-associated
- Nutritional causes
- Gastric ulcers
Foal heat diarrhea
- what does it look like? what age?
- coincides with what
- etiology
- should look for what?
- Mild, self-limiting diarrhea in foals 5-14 days of age
- Coincides with mare’s foal heat
- Etiology remains unknown
- Foals are not sick – if not nursing, dehydrated, etc another cause should be investigated for diarrhea
