Lecture 27 4/3/25 Flashcards by Danika Boltz

Why is diarrhea in calves a big deal?

-affects 50% of dairy calves and 20% of beef calves
-can cause high numbers of deaths among calves under 500 lbs

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What are the etiologic classifications of calf diarrhea?

-bacterial
-viral
-protozoan
-nutritional

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What are the big 7 causes of diarrhea in calves?

-enterotoxigenic E. coli
-rotavirus
-coronavirus
-Cryptosporidium parvum
-Salmonella
-coccidiosis
-Clostridium perfringens

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What is the timeframe for ETEC diarrhea?

0 to 5 days old

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What is the timeframe for rotavirus, coronavirus, and crypto diarrhea?

1 to 4 weeks old

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What is the timeframe for Clostridium diarrhea?

5 days to adulthood

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What is the timeframe for salmonella diarrhea?

2 weeks to adulthood

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What is the timeframe for Coccidiosis diarrhea?

3 weeks to 1 year old

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What are the characteristics of ETEC diarrhea in calves?

-affects calves less than 5 days old
-can only invade when the receptors for colostrum are present at very young age
-adult cattle asymptomatically shed pathogen while infected calves amplify environmental contamination

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What are the characteristics of the K99 antigen?

-antigen that allows for ETEC adhesion
-the epithelium becomes more resistant to this antigen with age

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What are the characteristics of ETEC heat stable toxin (STa)?

-secreted in response to bacterial attachment
-binds to specific receptor on enterocyte surface

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What are the clinical signs of ETEC diarrhea?

-calf “born with diarrhea”
-profuse, watery, hypersecretory diarrhea
-weakness
-depression
-dehydration

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What are the signs referable to hypovolemic shock in ETEC diarrhea calves?

-hypothermia
-tachycardia
-tachypnea
-slow or weak peripheral pulses
-acute death if fluids are not replaced

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What can be seen on necropsy in ETEC diarrhea calves?

edema within the intestinal tissues

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How is ETEC diarrhea diagnosed?

-dip sticks
-ELISA
-PCR for K99 genes
-E. coli adjacent to microvilli brush border on histopath.

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What are the characteristics of rotavirus?

-most common cause of calf diarrhea
-worldwide dist.
-shed in feces; allows for effective horizontal transmission
-typically occurs around 5-9 days of age with waning of maternal antibodies

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What are the two mechanisms of rotaviral diarrhea?

-rotavirus replicates in tip of villus and leads to malabsorptive diarrhea
-rotavirus gets into cells and begins to replicate and produce proteins, leading to hypersecretory diarrhea

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What determines the severity of rotaviral diarrhea?

strain virulence; more virulent strains replicate more quickly, affect a larger epithelial area, and cause more severe dz

What are the clinical signs of rotaviral diarrhea?

-diarrhea that is generally mild and short term
-dehydration
-weakness
-depression
-hypovolemic shock

How is rotavirus diagnosed?

-fecal antigen ELISA
-fecal PCR

What are the characteristics of coronavirus?

-epidemiology overlaps significantly with rotavirus
-shed in feces and resp. secretions, allowing for effective horizontal transmission
-dz is not typically very severe

How does coronavirus lead to diarrhea?

coronavirus replicates within entire villus, leading to loss of villus/blunted villus and diarrhea that may be more severe than rotavirus

What is important about coronavirus clinical signs, clinical pathology, and diagnosis?

they are the same as rotavirus; exception is that coronavirus affects entire villus and can cause more severe signs

What are the characteristics of cryptosporidium parvum?

-seen in calves less than 3 mo. old; most commonly around 2 weeks
-transmission can be calf-to-calf or indirectly via contaminated environments and fomites
-not host-specific; possible to get it from other sources
-ZOONOTIC!!!!

What is the pathogenesis of crypto diarrhea?

-protozoa destroys entire villus, causing a malabsorptive diarrhea -protozoa can infect downstream villi once released, leading to an auto-infective, enteroinvasive dz -production of the protozoa leads to an inflammatory-mediated dz of the intesines

How is crypto diagnosed?

-fecal float with Sheather's soln -acid-fast staining -PCR (esp. for environment)

What is the treatment for crypto?

supportive care only; nothing labelled for tx

What are the calf-adapted strains of Salmonella?

-Salmonella Dublin -Salmonella Newport

What are the generalist strains of Salmonella?

-Salmonella Typhimurium -Salmonella Montevideo

How does the Salmonella strain vary with age at infection?

-host-adapted strains typically infect animals closer to 4+ weeks of age, after maternal antibodies wane -generalist strains can infect earlier, around 2 weeks of age

What type of pathophysiology occurs with Salmonella diarrhea?

inflammatory mediated/enteroinvasive

What are the clinical signs of Salmonellosis?

-diarrhea that is foul smelling and contains blood and mucosal casts -fever -depression -anorexia -septicemic shock -peracute septicemia -dyspnea -sudden death

What are the clin path findings in Salmonellosis?

-neutrophilia/neutropenia -hypoproteinemia due to bowel damage -hemoconcentration -hypocalcemia

How is Salmonellosis diagnosed?

-culture on feces, blood, or tissues (bile) -PCR on feces, blood, or tissues -findings of thickened and hemorrhagic mucosa and sheets of fibrin on necropsy

Why is Salmonellosis treated with antibiotics?

due to the risk of sepsis and secondary invaders

What are the characteristics of coccidiosis?

-one of the most important causes of diarrhea in older calves -Eimeria has 21 day PPP; can only occur in calves this old or older -Eimeria bovis and Eimeria zurneii are host-specific -stress is an important predisposing factor

What type of diarrhea is caused by Eimeria?

enteroinvasive

What are the clinical signs of coccidiosis?

-diarrhea that is profuse, watery, and sometimes bloody -dehydration -tenesmus +/- rectal prolapse if chronic -fever -inappetance -poor growth -potential for neuro. signs

How is Eimeria diagnosed?

fecal float, but presence of oocysts is not a compelling dx since most animals have them

What are the coccidiocidal treatment options?

-sulfadimethoxine -amprolium (with thiamin supp.)

Why should TMS not be used as a coccidiocidal when possible?

-the rumen inactivates the trimethoprim component -if it must be used it must be dosed only on the "sulfa" component

What are the coccidiostat treatment options?

-monensin -lasalocid -decoquinate

What is important about coccidiostats?

-they are antibiotics that select for specific antimicrobials -they are not medically important for humans and are allowed to be used w/o prescription -they are VERY toxic to monogastric species