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Infectious disorders

Infectious disorders-general


Hanni Gulwani, M.B.B.S.

Last author update: 1 August 2012
Last staff update: 20 September 2024

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PubMed Search: Infectious disorders small bowel

Hanni Gulwani, M.B.B.S.
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Table of Contents
Anisakis | Bacterial enterocolitis | Cryptosporidium | Cyclospora (pending) | Entamoeba histolytica | Giardia lamblia | Isospora belli | Microsporidia | Rotavirus | Salmonella | Strongyloides stercoralis | Vibrio cholerae (pending) | Whipple disease | Board review style question #1 | Board review style answer #1
Cite this page: Gulwani H. Infectious disorders-general. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/smallbowelinfectiousdisordersgen.html. Accessed December 19th, 2024.
Anisakis
Definition / general
  • Larvae of ascarids (Anisakidae) are found in sea animals
  • After ingesting contaminated raw fish or other sea food, larvae attach to mucosa of stomach or small intestine and cause ulceration, penetration or perforation

Diagrams / tables

Images hosted on other servers:

Life cycle



Case reports

Clinical images

Images hosted on other servers:

Larvae in terminal ileum

Larvae in fish

Larvae in a herring



Gross images

Contributed by Bobbi Pritt, M.D.

Most likely a
type I Anisakis or
Pseudoterranova



Microscopic (histologic) description
  • Serositis, mucosal edema, submucosal abscess with eosinophils surrounding parasite with unpaired excretory gland (renette cell), Y shaped lateral epidermal cords, no apparent reproductive system and a ventriculus (glandular esophagus)
  • No lateral alae, no ventricular appendage, no intestinal cecum

Microscopic (histologic) description

Contributed by Bobbi Pritt, M.D.
 

Most likely a type I Anisakis or Pseudoterranova: anterior boring tooth (left); mucron (terminal spicule-like structure) (right)



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Larva in submucosa with eosinophils and lymphocytes

Larva in jejunum



Additional references
Bacterial enterocolitis
Definition / general
  • Bacterial related disease due to either ingestion of preformed toxin (Staphylococcus aureus, Vibrio cholera, Clostridium perfringens), infection by toxigenic organisms or infection by enteroinvasive organisms which invade and destroy mucosal epithelium cells (eMedicine: Bacterial Gastroenteritis [Accessed 7 September 2023])
  • Bacterial adhere to mucosal epithelial cells, elaborate enterotoxins, have capacity to invade
  • Adhere by plasmid mediated adhesins (E. coli, V. cholera), fimbriae or pili
  • Adhesion destroys microvilli brush border

Clinical features
  • Complications due to massive fluid loss and loss of mucosal barrier include dehydration, sepsis, perforation
  • Salmonella: invades via transcytosis with minimal epithelial damage
  • Yersinia enterocolitica: penetrates ileal mucosa, multiplies in Peyer patches and regional lymph nodes
  • Insidious infection: Yersinia and Mycobacterium tuberculosis
  • Cytotoxins: Shiga toxin, enterohemorrhagic E. coli
  • Enterotoxins:
    • Bind to cell membrane, enter cell, activates massive electrolyte secretion (cholera toxin, E. coli heat labile and heat stable toxins produce traveler's diarrhea)
    • No white blood cells in stool
  • Bacterial invasion:
    • Enteroinvasive E. coli and Shigella have plasmid that mediates epithelial cell invasion via microbe simulated endocytosis; then intracellular proliferation, cell lysis, cell to cell spread
  • Patients ingest preformed toxins:
    • Symptoms within hours
    • Explosive diarrhea and acute abdominal distress
    • 1 - 2 days
    • C. botulinum may produce rapid, fatal respiratory failure
  • Infection with enteric pathogens:
    • Incubation of hours - days
    • Diarrhea and dehydration (secretory enterotoxin) or dysentery (cytotoxin or enteroinvasive)
  • Traveler's diarrhea:
    • Fecally contaminated water / food
    • Begins abruptly, subsides in 2 - 3 days

Microscopic (histologic) description
  • Decreased epithelial cell maturation, increased mitotic figures, hyperemia and edema of lamina propria, variable neutrophils, modest villus blunting of small bowel
  • Late: lymphocytes, plasma cells, regenerative change

Differential diagnosis
Cryptosporidium
Definition / general
  • Acid fast protozoa which causes self limited disease in immunocompetent but severe watery diarrhea resistant to most therapy in immunocompromised (J Biomed Res 2012;25:1)

Diagnosis
  • Acid fast infective oocyst in stool

Microscopic (histologic) description
  • 2 - 5 micron basophilic spherical structures attached to microvillus surface of epithelium
  • Variable villus abnormality, may have eosinophils infiltrating mucosa

Microscopic (histologic) images

Images hosted on other servers:

Small round blue organisms at the luminal border

Cryptosporidium



Positive stains

Differential diagnosis
Cyclospora (pending)
[Pending]
Entamoeba histolytica
Definition / general
  • Dysentery causing protozoa that can also cause fulminant colitis; causes up to 100,000 deaths per year (Trop Biomed 2011;28:194)
  • Increased incidence in homosexual men and AIDS patients

Pathophysiology
  • Fecal oral spread
  • Amoeba invade colonic crypts, burrow into lamina propria, create flask shaped ulcer with broad base
  • 40% invade portal vessels, embolize to liver and cause abscesses up to 10 cm
  • May activate apoptosis in target cells (Trends Parasitol 2011;27:254)
  • Rare abscesses in lung, heart, kidneys, brain

Diagrams / tables

Images hosted on other servers:

Life cycle



Microscopic (histologic) images

Contributed by Hanni Gulwani, M.D.
Amoebic colitis, numerous trophozoites of amoeba are noted   Amoebic colitis, numerous trophozoites of amoeba are noted

Amoebic colitis, numerous trophozoites of amoeba are noted

Amoebic colitis, PAS stain   Amoebic colitis, PAS stain

Amoebic colitis, PAS stain



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Ulcer seen in amebic colitis

Mice deficient for leptin or the functional leptin receptor

Giardia lamblia
Isospora belli
Definition / general
  • Coccidian parasite that infects epithelial cells of small intestine
  • Causes chronic diarrhea and acalculous cholecystitis in AIDS patients (Indian J Med Res 2011;134:878)

Diagnosis
  • Cysts in stool, biopsy (H&E or EM)

Case reports

Microscopic (histologic) description
  • Cysts present in parasitophorous vacuole in lamina propria (Hum Pathol 2001;32:500)
  • Ovoid developmental forms are identified in and beneath epithelial cells near villus tip

Microscopic (histologic) images

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Oocyst of C. belli in epithelial cells of mammalian host



Positive stains
Microsporidia
Definition / general
  • Caused by Enterocytozoon bieneusi, an obligate intracellular protozoan that affects only enterocytes and Encephalitozoon intestinalis, which infects macrophages, fibroblasts, endothelial cells, enterocytes
  • Both cause chronic diarrhea in patients with immunosuppression, HIV

Diagnosis
  • Stool examination, PCR

Case reports

Treatment
  • Albendozole for E. intestinalis, nothing for E. bieneusi

Microscopic (histologic) description
  • Minimal / no changes in mucosa but can find development spores as 1.5 mm dots in enterocytes
  • May be surrounded by halos
  • Also nucleated sporont present as 3 - 5 micron, rounded, basophilic structure often surrounded by a halo

Microscopic (histologic) images

Images hosted on other servers:
 

Various images



Positive stains

Electron microscopy description
  • Often helpful for diagnosis
Rotavirus
Definition / general
  • Primarily diarrheal illness caused by infection with rotavirus

Essential features
  • Rotavirus is a segmented, nonenveloped double stranded RNA virus
  • It is ubiquitous and infection is essentially universal first occurring in early childhood
  • Transmission is fecal oral either via direct contact with stool or via fomites
  • In the developed world, the vast majority of infections cause self limited diarrheal illness or in subsequent infections and vaccinated populations, are asymptomatic
  • Most cases in the developing world are similar; however, the World Health Organization estimates that in 2013 ~215,000 children under 5 years old died from rotavirus infection (WHO: Rotavirus [Accessed 7 September 2023])
  • Live attenuated vaccines are available and their use has resulted in a dramatic worldwide decrease of severe disease
  • Intestinal intussusception is a rare but well recognized potential complication of vaccination

Terminology
  • Rotavirus is a genus of the Reoviridae family

ICD coding
  • ICD-10: A08.0 - rotaviral enteritis

Epidemiology
  • Rotavirus is ubiquitous and infection is essentially universal in childhood in all socioeconomic groups
  • Transmission is fecal oral either via direct contact with stool or via fomites
  • Infection generally first occurs around 6 months of age as the gastrointestinal tract matures and passive immunity from breast milk wanes
  • Infection may occur earlier in infants fed formula and in parts of India, Asia and sub-Saharan Africa where protection from maternal antibodies appears to be less effective
  • Reinfection occurs throughout life and in most children older than 2 years and adults infection is minimally symptomatic or asymptomatic due to immunity either from prior infections or vaccination
  • In the developed world, disease was more common in winter and spring; however, whether this pattern is still valid with widespread vaccination is unclear
  • Transmission in the daycare and hospital setting is common
  • Viral particles are hardy and resistant to chlorinated drinking water although they are vulnerable to alcohol based hand sanitizer and spray disinfectants
  • The World Health Organization estimates that in 2013 ~215,000 children under 5 years old died from rotavirus infection, overwhelmingly in the developing world compared to 528,000 in 2000 (WHO: Global Illness and Deaths Caused by Rotavirus Disease in Children [Accessed 7 September 2023])
  • According to the CDC in the United States rotavirus causes over 400,000 doctor visits, 200,000 emergency room visits, 55,000 to 70,000 hospitalizations and from 20 to 60 deaths each year (CDC: Rotavirus in the U.S. [Accessed 7 September 2023])
  • Serologically rotavirus is classified into serogroups, subgroups and G and P serotypes
  • Genotypically, it is classified into electropherotypes, genogroups and G and P genotypes
  • There is a substantial geographic and temporal variation in strain distribution and antigenic drift as well as introduction and reassortment with animal viruses which increases genetic diversity
  • Epidemiologically nucleic acid testing is increasingly replacing serologic testing
  • Further information is available from the Rotavirus Classification Working Group's database (RotaC v2.0: Classification Tool for Rotaviruses Group A [Accessed 7 September 2023])

Sites
  • Infection occurs in the small intestine

Pathophysiology
  • Pathophysiology is complex and not fully understood
  • Enterocytes at villous tips are initially infected; the virus binds surface carbohydrates and penetrates the cell membrane leading to transcription of viral RNA
  • Damage to the mucosa leads to malabsorption
  • Activity of disaccharidases and peptidases in the brush border is decreased and osmosis from unabsorbed nutrients contributes to the diarrhea
  • Glucose cotransport of electrolytes is decreased but oral rehydration solutions are still affective (see Treatment below)
  • Mature enterocytes are lost and initially replaced by immature secretory cells
  • There is net secretion of water in part mediated by the enteric nervous system
  • Clearance of infection is complex and involves overlapping elements of innate, cellular and humoral immunity
  • Virus is usually shed for 6 to 10 days after patients become symptomatic

Clinical features
  • There is an incubation period of 1 - 3 days
  • Illness in infants and young children usually starts with vomiting and fever lasting 2 - 3 days, progressing to 4 - 5 days of profuse watery diarrhea
  • In symptomatic older children and adults there is 1 - 4 days of diarrhea with anorexia, crampy abdominal pain and low grade fever
  • Chronic infections may occur in immunosuppressed patients excepting HIV; isotonic dehydration and metabolic acidosis occur in severe cases
  • Viremia is uncommon; extraintestinal manifestations are rare and described in the liver and kidney
  • Intestinal intussusception is a rare but well recognized potential complication of vaccination
  • Prior intussusception is a contraindication to vaccination
  • Patient deaths are due to dehydration and electrolyte abnormalities that lead to cardiac failure or less commonly seizures or aspiration pneumonia

Diagnosis
  • Enzyme immunoassay and PCR are the mainstays
  • Latex agglutination is often used in resource poor areas
  • Viral culture and electron microscopy are largely of historical interest
  • Microbiologic diagnosis is rarely required

Laboratory
  • Severe disease may cause metabolic acidosis and high urine specific gravity
  • Mild elevation of transaminases and uric acid may occur
  • Leukocytosis is rare and stool is usually negative for white blood cells and blood

Prognostic factors
  • Disease is most severe in infants and young children
  • Immunosuppressed patients often suffer from more severe disease and cannot receive the live attenuated vaccine although patients infected with HIV do not suffer more severe disease and should be vaccinated
  • Infection in the developing world is more likely to lead to severe illness or death; this is related to less access to health care, malnutrition, the presence of other infections and possibly larger inoculums

Case reports

Treatment
  • Mild to moderate disease: oral rehydration
  • Severe disease: intravenous lactated ringers or normal saline until oral rehydration can be tolerated
  • Infants: return to breast feeding or formula as soon as it can be tolerated
  • In the developing world, zinc supplementation and some probiotics in children older than 6 months may reduce disease duration
  • Diosmectite, a type of aluminum magnesium clay silica, is available in parts of Europe and controls gastroenteritis
  • Oral immunoglobulins have a possible role in chronic disease and for high risk patients where vaccination is unlikely to be effective (premature infants) or is contraindicated
  • Antibiotics are not indicated
  • Vaccination is recommended to commence at 2 months of age

Microscopic (histologic) description
  • Biopsy is rarely performed
  • Findings are nonspecific; villi are shortened, blunted and lined by cuboidal cells
  • There is crypt hyperplasia and increased mononuclear cells within the lamina propria
  • Apoptotic epithelial cells may be present
  • Disease may be patchy in distribution
  • Viral inclusions are not present

Electron microscopy images

Images hosted on other servers:
Missing Image

Multiple
rotavirus
particles



Differential diagnosis
  • Other causes of infectious gastroenteritis and enterocolitis

Additional references
Salmonella
Definition / general
  • Bacterial causing food poisoning and typhoid fever (S. typhi)
  • Typhoid fever: systemic dissemination with bacteremia, fever, chronic infection of joints, biliary tree, bones and meninges
  • From contaminated milk, eggs, beef, poultry
  • Usually affects terminal ileum

Gross images

Case #362
 



Microscopic (histologic) description
  • Ulcers overlying Peyer patches with minimal inflammatory cells, chiefly mononuclear (plasma cells, histiocytes and lymphocytes)
  • Often histiocytes with erythrophagocytosis
  • May lead to perforation or toxic megacolon

Microscopic (histologic) images

Case #362
     


     

Strongyloides stercoralis
Definition / general
  • Nematode with complex life cycle that alternates between free living and parasitic cycles, with potential for autoinfection and multiplication within host

Life cycle
  • Larvae burrow into mucosa of duodenum and jejunum, where they mature into adults
  • Females lay eggs, which develop into larvae that pass into stool, where they mature and become infective
  • Infective larvae in soil penetrate intact skin, usually through feet
  • Larvae enter circulatory system, are transported to lungs, enter alveolar spaces, are carried to trachea and pharynx, are swallowed and enter intestinal tract, where process is repeated
  • If larvae become infective before leaving body, they may invade intestinal mucosa or perianal skin, causing autoinfection

Diagrams / tables

Images hosted on other servers:

Life cycle



Clinical features
  • Symptoms: none, diarrhea, malabsorption
  • Severe / fatal infections in immunocompromised, due to worms moving from GI tract into other organs (WormBook 2007:1)

Diagnosis
  • Larvae in stool
  • Adult female or eggs in small bowel mucosa, often with eosinophilic or granulomatous inflammation

Case reports

Treatment

Microscopic (histologic) images

Contributed by Josehp Christopher Castillo, M.D. and Case #133
 

Small intestine

   

Various images



Contributed by @liverwei on Twitter
Strongyloides stercoralis   Strongyloides stercoralis   Strongyloides stercoralis

Strongyloides stercoralis



Additional references
Vibrio cholerae (pending)
[Pending]
Whipple disease
Board review style question #1
What is true regarding rotavirus?

  1. Characteristic viral inclusions are diagnostic
  2. Incidence has increased
  3. Infection typically affects the sigmoid colon and rectum
  4. Intussusception is a rare but recognized complication associated with vaccination
  5. Most deaths occur in the elderly
Board review style answer #1
D. Intussusception is a rare but recognized complication associated with vaccination. However, there is broad agreement that the benefits of vaccination greatly exceed the risk.

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