L9: Ruminant Diarrheal GI Disease (Sanchez) Flashcards
Mechs of diarrhea
1) malabsorption (osmotic diarrhea)
2) hypersecretion
3) exudation (increased permeability)
4) Hypermotility
Risk factors of diarrhea
1) host (low birth weight, prematurity, FPT)
2) environment (sanitation, pop. Density, feeding system)
3) agent (virulence, load)
Most common reported causes of diarrhea in young and old ruminants
Young (30 days): salmonella, coccidia, rumen acidosis
Dx of ruminant diarrhea
- etiology not essential for tx but useful in control/prevention strategies
- lab data:
- metabolic acidemia (HCO3 loss)
- hyponatremia, hypoCl, HyperK
- hypoglycemia
- CBC: hemoconcentration or leukopenia
Enterotoxigenic E. Coli (ETEC): populations affected
-major cause of diarrhea in calves
ETEC pathophys.
- encapsulated bacteria
- fimbrial antigen F5 allows attachment and colonization in distal SI (binds on immature epithelial cells)
- older calves: comorbidity can cause villous atrophy
- produces heat stable toxins which bind to endothelial receptors and cause hypersecretion of Cl, Na, H2O, and other electrolytes
CS/labwork of ETEC
- watery diarrhea (rapid onset)
- not usually febrile
- hypothermic if in hypovolemic shock
- acidemia with decreased Na, Cl, K, glucose
Dx/Tx/Prevent of ETEC
Dx: fecal PCR, ELISA
Tx: same for diarrhea in general
Prevent: give dry cows F5 vaccine, give oral F5 vaccine in outbreaks
Attaching and Effacing E. Coli
EPEC: intimin gene
STEC: shiga-toxin producing
EHEC: both
- common in calves 2-21 days up to 4 months
- diarrhea can be bloody
- attachment in colon, SI, or both
- Dx: PCR
Rotavirus general chars.
- most common viral cause of diarrhea*
- short incubation (12-24 hrs)
- stable in environment
- affects calves
Rotavirus pathophys.
- small intestine
- malabsorptive diarrhea that causes villous atrophy but spares the crypts
- causes secretory diarrhea
- mixed infection with ETEC or Crypto is common
- morbidity high, mortality low to variable
CS of rotavirus
- lethargy, dehydration
- anorexia
- low grade fever
- watery yellow diarrhea
Dx of rotavirus
- electron microscopy (gold standard)
- PCR (high sensitivity, specificity)
- ELISA (fast, good agreement)
Tx/Prevent of Rotavirus
- Tx: supportive
- Phenol-based disinfectants
- vaccination of dry cows
- oral calfhood vaccination (caution: can bind to colostral Ab)
coronavirus most common at what age
2-24 days of age
Clinical course: 3-6 days
Coronavirus implicated in what diseases?
Respiratory disease, winter dysentery
Pathophys. Of coronavirus
- affects all SI, colon
- Colon: affects villi and crypts
- SI: affects villous enterocytes
- causes malabsorption and maldigestion
- more severe disease, higher mortality than rotavirus
CS of coronavirus
Watery diarrhea +/- mucus
Severe lethargy
Dx/Tx/Prevent of coronavirus
Dx: EM, ELISA; shedding drops quickly in course of dz
Tx/prevent same as for rotavirus
Clostridium perfringens affects what age?
Most common type of Clostridium perfringens
Type C
CS of Clostridium perfringens
- Acute, hemorrhagic enteritis (typically fatal)
- bloody d, neuro signs
- Type A –> hemorrhagic abomasitis, abomasal ulceration
Dx/Tx/prevent of C. Perfringens
Dx: Toxin ID. Type A can be normal flora
Tx: fluids, abx (penicillin), flunixin
Prevent: type C and D toxoid prior to calving. Antitoxin?
Cryptosporidum affects what age?
C. Parvum:
Most or 2nd most commonly isolated GI pathogen
Cryptosporidium
Crypto morbidity/mortality?
High morbidity, low mortality
-not host specific
Pathophys. Of crypto
- oocysts excyst following exposure to gastric acid and bile salts
- sporozoites infect enterocytes from abomasum to colon but mostly in the SI
- infective oocytes passed in feces
- villous atrophy, fusion, crypt hyperplasia and inflammation –> malabsorptive diarrhea
Peak shedding age of cryptospordium
- 7-14 days (up to 1 month)
- CS usually 7 days (single infections)
CS of crypto
-diarrhea, decreased appetite, dehydration
Morbidity of crypto
Up to 100% of dairy calves, less than 5% of beef calves
Dx/Tx of crypto
- floatation, direct exam, acid-fast stain
- PCR, ELISA: variable sensitivity/specificity
Tx: supportive only
Prevent of crypto
- highly resistant organism
- practical disinfectant not available
- environmental hygeine: calf hutches, separate feeding supplies for calves
2 main causes of Salmonellosis
1) Salmonella enterical serovar Typhimurium
2) “ “ serovar Dublin
Pathophys. Of salmonellosis
- fecal-oral transmission predominates (also URT and conjunctiva)
- invasion through M-cells, enterocytes, tonsilar lymphoid tissue and dissemination through mononuclear cells
- distal SI, cecum, colon affected:
-causes hemorrhage, necrosis, mesenteric lymphadenopathy, pseudomembrane formation, and fibrin plugs in GB
Age most affected by salmonellosis
1-4 months (as early as 3 days)
CS and lab findings in Salmonellosis
CS: diarrhea +/- blood or mucus, fever, lethargy, ill thrift
Lab: hypoproteinemia, neutropenia w/ toxicity if acute, leukocytosis if chronic
High morbidity/mortality in outbreaks
Dx/Tx/prevent of Salmonellosis
Dx: fecal culture, PCR
Tx: supportive, abx, NSAIDs
Prevent: environmental hygiene, biosecurity, colostrum management, +/- vaccines
Salmonellosis risk factors
- prophylactic antimicrobial use
- co-use of maternity, hospital pens
- open herds
Importance of neonatal diarrhea
1 cause of neonatal death
-difficult to control/treat
>$120 mil/year economic impact
