Viral Enteric & Hepatic Infections

  • The enteric viruses we’ll learn about are naked capsids that can withstand harsh stomach acids.
  • When symptomatic, illness is characterized by diarrhea and vomiting.
  • Outcomes are often worse for children and infants, due to malnutrition and dehydration stemming from fluid and electrolyte loss.
  • The causative viruses are transmitted via the fecal/oral route.
  • Hepatic viruses cause tissue damage and trigger inflammatory responses that produce the symptoms of infection.

Enteric Viruses

  • Cause acute gastroenteritis and are typically ingested via contaminated food and water.
    – Vomiting and diarrhea.
    – Other symptoms include possible fever, nausea, abdominal pain or cramping, and myalgia and malaise.
    – Rehydration and electrolyte therapy are common treatments.
  • Key viral causes of gastroenteritis:
    –  Norovirus is a leading cause of gastroenteritis in all age groups in the United States; outbreaks have been associated with contaminated shellfish.
    –  Adenovirus accounts for approximately 15% of hospitalized gastroenteritis cases, especially in infants. Recall that adenovirus also causes respiratory and ocular infections.
    – Astrovirus causes mild, watery diarrhea, most commonly in children.
    However, extra-intestinal infections can occur in immune-compromised patients; some viral genotypes, for example, have been associated with central nervous system infections.
    – Rotavirus is the leading cause of severe diarrhea worldwide in children under five years old; in premature neonates, rotavirus can manifest as necrotizing enterocolitis or hemorrhagic gastroenteritis.
    Because of the high morbidity and mortality associated with rotavirus, vaccination is recommended for all infants.
  • In immune compromised patients, particularly AIDS patients and transplant recipients, cytomegalovirus (CMV) and Epstein-Barr Virus are associated with gastroenteritis.
  • For a list of bacterial pathogens that induce enteric illnesses, see here.

Hepatic Viruses: Hepatitis Viruses A, B, C, D, and E,

  • Hepatitis is characterized by inflammation of the liver.
    – Acute hepatitis = Inflammation that lasts less than 6 months
    – Chronic hepatitis = Inflammation that lasts 6 months or longer
    – In some cases, hepatitis can lead to fulminant liver failure; write that this is characterized by rapid, acute livery injury with hepatic encephalopathy.
  • Vaccine availability varies for the hepatitis viruses, and there is no vaccine for Hepatitis C virus due to its heterogeneous nature.

Acute hepatitis

  • Hepatitis A, B, C, D, and E can cause acute hepatitis.
  • Symptoms include: Jaundice, nausea and vomiting, abdominal pain, dark urine, and joint pain, as well as low or no appetite and fatigue.
    – Liver failure is possible with acute hepatitis, but rare.
  • General features of acute hepatitis histopathology:
    – Ballooning degeneration: hepatocytes are unusually large, with a “whispy” look
    – Spotty necrosis throughout the liver tissue
    – Mononuclear cell infiltrate
    – Councilman bodies, which are shrunken, acidophilic cells.
  • Hepatitis A and E only cause acute hepatitis, not chronic.
    – Both viruses are transmitted via the fecal-oral route, often via contaminated water.
    – No carrier state for these Hepatitis viruses.
    – Both typically cause mild and self-limiting acute hepatitis; fulminant liver failure is possible but rare.
    – An important exception is that Hepatitis E infection has high mortality rates in pregnant women, especially during the third trimester.

Chronic hepatitis

  • Caused by Hepatitis BD, and C.
  • Chronic infections can lead to scarring, cirrhosis, and cancer.
    – Smoking, alcohol use, age, sex, and population seem to increase the risk of disease progression.
  • Hepatitis viruses B, D, and C are transmitted via body fluids
    – Carrier states exist
    – Hepatitis B can be transmitted from mother to neonate during childbirth.
    – Hepatitis C often produces extra-hepatic effects, including cryoglobulinemia vasculitis and B-cell non-Hodgkin’s lymphoma, and other immune mediated and inflammation mediated diseases.
    – Hepatitis D is often called the “Delta agent”; though infection with Hepatitis D, alone, does not produce illness, when combined with Hepatitis B, it makes infection worseand increases the risk of Fulminant liver failure.
  • Hallmarks of Hepatitis B and C histopathology:
    – Hepatitis B often produces “ground glass” hepatocytes; the tiny grains in the cytoplasm are from viral protein accumulation.
    – Hepatitis C infection is characterized by lymphocyte aggregates and follicles, especially around the portal tracts;
    bile ducts are often damaged, and, steatosis (also called fatty change) can also occur.

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