Where does enterocyte proliferation occur?
In the Crypts
What are 2 compensatory reaction to enterocyte loss?
1. Flattening of remaining enterocytes
2. Increased Mitotic rate of crypt epithelial cells
The mucosal phase of digestion is mediated by WHAT?
The delivery phase of digestion involves what?
Lymphatics and Blood
The mucosal phase of digestion involves what?
Surface (microvilli) and Cellular (enterocytes)
The intraluminal phase of digestion involves what?
Pancreatic and Biliary: break down food
What are some causes of secretory diarrhea?
Bacterial Exotoxins, Inflammatory Mediators (prostaglandins, eiconsinoids, histamine, kinins, cytokines-->influence enteric nerve reflexes)
How does bacterial exotoxins cause secretory diarrhea?
They affect secretion/ absorption (active cAMP and gAMP) of Na+, Cl- and therefore water
What is the most common cause of diarrhea in neonatal calves?
T or F
ETEC destroys enterocytes while it causes disease
FALSE, ETEC uses pili (fimbrae) to attach to the enterocytes (apical) and secrete exotoxins that cause secretory diarrhea
Why does ETEC only infect neonates in the first week of their lives?
Because ETEC needs the receptors involved in colostrum absorption (FcRN) in order to attach to the enterocytes and these receptors go away quickly after the neonate is born.
Why do animals die from ETEC infection?
Because of the HYPERsecretory diarrhea which results in DEHYDRATION, electorlyte imbalances, and acidosis.
Where does ETEC attach or infect?
ON the apical portion of the microvilli at the FcRN receptors (think passive transfer receptors)
What are two effects of enterotoxins from ETEC?
1. inhibits coupled Na-CL uptake and water absorption in the villi-cGMP pathway
2. Stimulates secretion of Cl- in crypts-cAMP pathway
Where does rotavirus and coronavirus set up shop?
they infect, proliferate in, and DESTROY Mature Villous enterocytes
Leads to villous atrophy-->malabsorptive (osmotic) diarrhea
Enterocyte damage-->exudative diarrhea
How does Rota and Corona viruss cause diarrhea? What type of diarrhea is it?
Villi become denuded, contracted, and may fuse (villous atrophy)-->malabsorption (osmotic diarrhea)
Enterocyte Damage-->exudative diarrhea
How do villi compensate for enterocyte damage from rota and corona viruses?
Crypt (immature) enterocytes proliferate in response-->villi will be normal again in ~7 days
When would you see Rotavirus in calves?
Between 0-2 weeks of age
When would see coronavirus in calves?
Between 0-3 weeks
T or F
Coronavirus and Rotavirus desrupt the crypts in the small intestine
FALSE, They attack mature enterocytes on the apical portion of the villi, thus the crypt cells remain intact
What cells does rotavirus and coronavirus attack and where?
They attack MATURE enterocytes in the Small intestine leading to osmotic (loss of absorptive surface area) and exudative diarrhea (mucosal damage)
What is specific to rotavirus that corona virus does not do?
Rotavirus additionally impairs disaccharidases in the brush border-->leading to maldigestion of carbohydrates
T or F
Cats can be infected with parvovirus
TRUE, but it is called panleukopenia, cat distemper, or feline enteritis.
What are clinical signs of parvo infection?
Diarrhea-Bloody, Fetid (FOUL smelling)
Something smelling extremely unpleasant
What cells does parvovirus infect?
Rapidly DIVIDING cells
Where does parvovirus first repicate?
In the lymphoid tissue of the oropharynx-->viremia-->dissemination to rapidly dividing cells of GI tract, bone marrow
Parvo infection leads to loss of enterocytes. What three events occur because of this damage?
1. loss of absorptive surface area-->malabsorption--> osmotic diarrhea
2. loss of fluid, electrolytes, plasma proteins into the lumen--> exudative diarrhea
3. loss of mucosal barrier (ulceration)-->secondary bacteremia, endotoxemia
Parvo infections in young animals can lead to additional lesions, what are they?
Puppies infected at <2week old: Myocarditis (+/- lesions in the liver, kidney, lung, blood vessels
Kittens infected in Utero: congenital cerebellar hypoplasia
T or F
With parvo infection you will see defined crypts
False, parvo attacks the rapidly dividing cells found in the crypts leading to diffuse villous atrophy and crypt dropout
What will you see grossly with parvo infection?
The small intestine will be segmentally dark red
what will you see microscopically with parvo infection?
Severe villous atrophy
Coccidiosis is an intracellular or extracellular parasite?
What type of enterocolitis do you see in calves, kittens, puppies, lambs, kids, piglets and poultry with coccidiosis?
Calves, Kittens, puppies-->hemorrhagic enterocolitis
Lambs, kids-->proliferative enterocolitis
RARE in horses
What 3 things help determine the severity of coccidiosis disease?
1. Infective dose
2. Host immune status
3. site of development (species virulence)
-villi vs. crypts