Pathology of the intestines Flashcards
Enteritis
Inflammation of the intestines
Typhlitis or cecitis
Inflammation of the caecum
Colitis
Inflammation of the colon
Proctitis
Inflammation of the rectum
What effects does enteritis have?
Loss of fluid and electrolytes from body.
Malabsorption – due to effect on epithelial cells.
Osmotic effect - produces diarrhea;
Weight loss.
Types of enteritis
Catarrhal
Ulcerative
Haemorrhagic
Fibrinous
Necrotic
Proliferative
Lymphoplasmacytic
Eosinophilic
Catarrhal Enteritis
Initially hyperaemia of gut may be visible through the serosa.
Blood vessels obvious and whole bowel appears red looking, wet shiny and oedematous (no external damage).
Internally mucosa is oedematous, with mucoid appearance.
Initially contents are thin watery / serous.
As condition progresses exudate becomes more mucoid and cellular.
Mucous coats epithelial surface of gut.
Bowel contents may appear quite opaque as polymorphs enter it (i.e. may become mucopurulent).
In older cases of catarrhal enteritis villi become stubby due to loss of epithelial cells and mucosa may appear quite shiny.
Parasitic enteritis
Pre-patent period of 7-10 days then develops greenish diarrhoea.
In young animals can cause serious disease and die.
Gut filled with greenish soupy material.
Oedema and hyperaemia of mucosa.
Aetiology of viral enteritis
Coronavirus
Parvovirus
Rotavirus
Adenovirus
Herpesvirus
Calicivirus
Norovirus
Circovirus
Feline infectious enteritis / feline panleucopenia
Feline panleucopaenia virus (FPLV) (felids, mink, ferrets, raccon).
Uncommon now, as vaccine is available.
<6months old
Primarily in cat over last 10/15 years but now also seen in dog (canine parvovirosis).
Clinical signs of feline infectious enteritis
Seen in cats under 6 months age mostly and is common in groups of unvaccinated cats producing big outbreaks with vomiting and pyrexia.
Severe vomiting, severe thin watery foul smelling diarrhoea may be blood-tinged.
Usually die from dehydration despite treatment. May also die from other infections. Virus shed from urine and faeces for up to 6 weeks.
White blood cell count drops very low (almost non-existent from 10000 / mL to 1/ mL if lucky) - panleucopaenia.
Pathology of feline infectious enteritis
In cat thickened, turgid and swollen intestine, dull mottled appearance, pale.
Contents rather dry - gets worse lower down gut.
In upper small bowel see areas of depression in the mucosa due to destruction of tissue overlying Peyer’s patch (GALT).
Lower down see haemorrhagic enteritis (dog) or fibrinous (cat).
Inflammation sometimes doesn’t appear very severe.
Lesions may be very few and usually need histology for diagnosis.
If is a radiomimetic virus (has similar effect to radiation poisoning) as affects all rapidly dividing cells and destroys them - e.g. epithelium in the base of the crypts of small intestine are killed.
Histology of feline infectious enteritis
Complete necrosis of crypt lining cells with very little inflammation.
Collapse of villous architecture.
Submucosa not affected and lamina propria left intact.
If survives for more than a few days then see cyst-like structures histologically in deepest parts of glands of intestinal mucosa.
Flattened epithelial cells line these cystic glands and are enterocytes trying to repair the damage.
May see intranuclear inclusion bodies (but very hard to find).
May get lymphocyte invasion of mucosa.
Lymph nodes appear pale, oedematous, aplastic almost.
Bone marrow - pale and fatty looking, depleted of cells.
Canine parvovirosis
New disease but virus closely related to feline virus.
Canine parvovirus-2 (CPV-2).
DNA 98% homologous to virus of cat.
Canine virus does not cause disease in cats.
Clinical signs of canine parvovirosis
Virus shed only during clinical disease 7-10 days.
Enteritis in dogs > 6 weeks old, - myocarditis in puppies (uncommonly nowadays).
Rottweilers and Doberman pinschers at increased risk for parvovirus.
Vaccines very effective, but virus is hardy and survives in environment.
Microscopic lesions of canine parvovirosis
Villi atrophy
Crypt necosis
Submucosal oedema
Diagnosis of canine parvovirosis
Look for viral antigen in faeces by red cell agglutination test.
Immunoflurescence
ELISA
Serology - need caution.
Aetiology of bacterial enteritis
Colibacillosis
Clostridiosis
Salmonellosis
Colibacillosis
Only a few strains of this organism cause disease – identified by their serotypes.
Young animals are at highest risk for coliform diarrhoea.
Intrinsic and extrinsic factors act together to produce infection.
Shiga-toxin producing E. coli
- Verotoxin-IL-8
Pathogenesis of colibacillosis
Three mechanisms by which coliform organisms cause diarrhoea.
* Enterotoxigenic E. coli
* Enteroinvasive E. coli
* Enteropathogenic (attaching an effacing)
Can cause systemic infections
Enterotoxigenic E. coli
Calves: Enterotoxigenic E. coli (ETEC)- only seen in animals 4-5 days possibly up to 1 week. If older than 1 week not ETEC.
ETEC’s need two qualities -
○ adherence factors
○ heat stable toxins
Death is from dehydration and electrolyte loss.
Control of Enterotoxigenic E. coli
Management factors such as hygiene, good colostral intake, etc.
Enteroinvasive E. coli
These strains (O101) act like Shigella or Salmonella, penetrating enterocytes, invading lamina propria and spreading to lymph nodes and beyond.
Toxin damages enterocytes leading to villus blunting, elongation of crypts and sometimes mucosal ulceration.
Not common in animals.
Enteropathogenic E. coli (EPEC)
Organisms penetrate glycocalyx, adhere closely to mucosal cell surface and destroy microvilli.
Cause blunting of villi, crypt hypertrophy and inflammatory cells in lamina propria.
Colon often more severely affected than intestine.
