Hepatitis A and Viral Diarrhoea

• The text is regarding enteric hepatotropic viral infections and viral diarrhoea, with a focus on Hepatitis A and E, Rotavirus, Norovirus, Sapovirus, and Adenovirus infections

Hepatitis A (HAV) Infection

• Hepatitis A, known as infectious jaundice, is caused by HAV that transmits via the fecal-oral route often through contaminated food.
• HAV is an enterically transmitted virus.
• The Hepatitis A virus is an unenveloped, single-stranded RNA virus with cubic symmetry, measuring 27 nm in diameter, classified as a hepatovirus within the picornavirus genus.
• HAV accounts for ~40% of acute hepatitis cases, making it the most common viral hepatitis form.
• It's prevalent in economically developing regions of Africa, Asia, and Latin America, where sanitation and hygiene are poor.

About HAV Structure and Classification

• HAV belongs to the Picornaviridae family, previously known as Enterovirus 72, and now assigned to the Heparnavirus (Hepatovirus) genus.
• HAV is a 7.48kb RNA virus, encapsidated within an icosahedral capsid, lacking an envelope, making it a naked RNA virus.
• Its Genome is single-stranded positive sense RNA (+ss RNA).
• The 3' end of its RNA is polyadenylated, and the 5' end has the viral protien VPg.
• VP1, VP2, VP3, and VP4 are the viral proteins with VP1 and VP3 as major antibody binding sites.
• The virus is small and spherical in shape, with the capsid an icosahedral

Hepatitis A Transmission & Incubation

• The human is the only known reservoir.
• HAV main transmission route occurs via the fecal-oral route.
• It can also spread with direct person to person contact.
• Transmission may occur via food handlers and children.
• Once the virus is ingested it travels to the liver via the intestinal epithelium, is uptaken by hepatocytes, replicates and then is excreted into bile and shed in stool.
• Lacking a lipid envelope, HAV is stable in bile which is an important factor in fecal-oral transmission.
• Incubation period lasts 2-6 weeks.

Pathogenesis of HAV

• HAV, after ingestion and survival of gastric acid, traverses the small intestinal mucosa, reaches the liver via the portal vein, and is taken up by hepatocytes.
• HAV attaches to liver cells via cellular receptors, entering the cell through receptor-mediated endocytosis.
• Inside the endosome, the virus releases VPg protein, which creates pores on the endosomal membrane releasing the viral genome into the host's cytoplasm which damages hepatocytes.
• The virus multiplies in hepatocytes and Kupffer's cells, resulting in mononuclear infiltrate, ballooning degeneration of hepatocytes, and acidophilic bodies.
• Newly synthesized viruses are shed into bile ducts and excreted in faeces, with a usual incubation period of 14-28 days.
• Liver damage stems from the immunological response of cytotoxic T cells, and not directly due to HAV.

Clinical Manifestation of HAV

• HAV infection’s clinical manifestations vary from asymptomatic to fulminant hepatitis, acute liver failure and the need for transplant.
• Age significantly impacts disease manifestation.
• Children are more frequently asymptomatic, with clinical disease developing in approximately 30% of cases, versus over 70% in adults.
• In children under 6 years of age, >90% display asymptomatic manifestation.
• In Children from 6-14 years of age, 40-50% display asymptomatic manifestation.
• Adults and children over 14 years, 70-80% display symptomatic manifestation.

Signs and Symptoms of HAV Infection

• Symptoms of HAV infection typically has an abrupt onset.
• Initial Symptoms include fever, malaise, anorexia, nausea, vomiting, abdominal discomfort and headache are non-specific.
• Symptoms of cholestasis progress over days to weeks, including:
  • dark urine
  • pale stools
  • jaundice
  • pruritus
  • hepatomegaly
• Extrahepatic manifestations like skin rash and arthralgia can be observed.

Hepatic Complications From HAV

• Hepatic complications from HAV infection encompass fulminant hepatitis, chronic cholestasis, and relapsing hepatitis.
• In less than 1% of patients, HAV causes fulminant hepatitis which has a 70% spontaneous survival rate.
• The remaining 30% results in liver transplantation or death.
• Fulminant hepatitis is associated with advanced age, pre-existing liver injury (non-alcoholic liver disease or alcoholic liver steatohepatitis), and host response.

Lab Investigations for HAV

• To test for Hep A a liver Function Test is done in lab.
• Alanine (ALT) and Aspartate aminotransferase enzymes increase by 4-100 times in Hepatitis patients versus normal patients.
• A rapid increase of ALT with short duration (4–20 days) suggests a HAV infection.
• Serum bilirubin and globulin levels will increase and serum albumin levels will decrease during testing.
• For Serology, antibody detection exists where a rapid kit detects anti-HAV IgM.
• Anti HAV-IgM appears in blood at the onset of symptoms.
• Detection of hemagglutination antigen or virus particle in faeces is key to determining an antigen detection for Hepatitis A in addition to HAV Serology.
• Detecting HAV via virus culture, is long and difficult; it can take up to 4 weeks to get result.
• In cell line culture, the virus has low replication over a long time.
• Molecular Diagnosis is possible through Electron Microscopy and RT-PCR.

Markers of Hepatitis A Infection

• A positive anti-HAV IgM test indicates an acute infection.
• Fecal shedding decreases as the IgM titer increases.
• A positive anti-HAV IgG result signifies resolved or past infection.

HAV Treatment

• Treatment is limited to supportive care given HAV cases are self-limited and there is available treatment for infections to support symptomatic aspects of hepatitis.
• A full recovery after symptoms may be slow and several weeks or months.
• Hospitalization is unnecessary in the absence of acute liver failure.
• It is key to maintain comfort and adequate nutritional balance via supportive therapy by replacing the fluids lost from vomiting and diarrhea.

Prevention of Hepatitis A

• To prevent Hepatitis A, general hygeine is the most important action.
• Mandatory hygiene practices include hand-washing, cooking food properly, and potable water.
• Vaccinations for high-risk categories can help to prevent Hepatitis A and reduce infection risk.
• Infection risk can be reduced on an individual level by:
  • maintaining hygienic practices such as hand-washing with safe water before handling food.
  • avoiding consumption of water and/or ice of unknown purity.
• Prevention of HAV at the population level includes:
  • maintaining quality standards for public water supplies.
  • establishing proper disposal systems for human feces.

HAV Vaccine

• Types of vaccines available include Inactivated vaccines (USA and Europe), and Live, attenuated vaccines (China, Bangladesh, Guatemala, Philippines, Thailand and India).
• Vaccination is recommended by the CDC for children between 12 to 23 months with a second dose needed at least 6 months after the first and or in individuals between 2 to 18 years old who have not received vaccination
• Vaccines are also indicated for, illicit drug users, people experiencing homelessness, people with chronic liver disease, HIV-positive people and pregnant women at a high risk of severe hepatitis A.
  • No vaccine is licensed for children younger than 1 year of age.
• Nearly 100% of vaccinated people develop protective antibody levels within 1 month of a single dose.

Hepatitis E Virus (HEV)

• HEV is a 32-34nm unenveloped RNA virus in the Hepeviridae family.
• It is known to cause epidemic hepatitis in resource-limited countries who have limited access to water and sanitation.
• Transmission and clinical outcomes mirror those of HAV infection.
• Hepatitis E location of prevalence are East and South Asia.

HEV Transmission and Mortality

• Typically occurring via the faeco-oral route such as through contaminated water.
• Person-person contact is rare.
• HEV Symptoms mirror hepatitis A, however HEV can be fulminant in some patients, particularly pregnant women.
• Mortality rate reaches 30% in pregnant women in their respective trimester of pregnancy.
• Death in pregnant women may stem from complications of obstetric, hemorrhage, or eclampsia.

Introduction to Viruses Causing Diarrheal Diseases

• The presentation is on viruses in diarrheal diseases.
• Diarrheal diseases affect the Upper and Lower Gastrointestinal Tract (GIT)

The Human Gastrointestinal Tract

• The GIT is responsible for digestion (upper GIT) and absorption (lower GIT) of ingested molecules.
• Parts of the Upper GIT is responsible for Digestion:
  • Mouth
  • Oesophagus
  • Stomach
  • Duodenum
• Parts of the Lower GIT is responsible for Absorption:
  • Small Intestine is made up of Duodenum, Jejunum, Ileum
  • Large Intestine is made up of Caecum, Auxiliary Colon, Ascending Colon, Descending Colon, and Anus
  • Absorption deficiencies due to infectious agents of viral origin highlights Lower GIT

GIT Wall

• Mucosa is the absorptive and secretory layer made of epithelium and connective tissue.
• A specialized goblet cells secrete mucus, and on the mucosal layer are villi and micro villi.
• Sub-mucosa (vascularised) is thick and vascular and absorbs elements from the mucosa.
• The sub-mucosa also has glands and nerve plexuses.
• Muscularis performs contractions and movement in the Gl tract composed by of circular and longitudinal smooth muscle.
• This propels food and mixes it with digestive enzymes.
• Serosa (outer protective layer) consists of connective tissue and squamous epithelium.
• It secretes lubricating serous fluid.

Diarrhoea

Diarrhoea is 3 loose, or watery stools per day (WHO). Acute (5-10 days) is different from having Chronic (>10 days). Diarrhoea is often accompanied by abdominal pains, low fever, nausea, and vomiting (Gastroenteritis).

• According to WHO, diarrhea leads to 3.5 million deaths yearly.
• 80% of those deaths occur in children whom are under 5.
• Children are more susceptible to diarrhoea complications which leads to dehydration that results from fluid loss.

Types of Diarrhoea

• Secretory diarrhoea: increase in active secretion, or inhibition of absorption with little structural damage. Cholera toxin increases anion secretion, drawing sodium and water into the lumen. It has isotonic intestinal secretion with plasma, even during fasting.
• Osmotic diarrhoea: an excessive ammount of water drawn into the bowels, often from indigestion leaving nutrients in the lumen to pull in water Can also stem from osmotic laxatives e.g. Gelucyl to alleviate constipation by drawing water into the bowels. Exudative diarrhoea: stools are present with blood and pus. Inflammatory bowel diseases such as Crohn's or colitis, severe infections such as E. coli, and other food poisoning can results in.
• Motility-related diarrhoea: caused by food moving too fast through the intestines (hypermotility) which does not allow enough time to absorb sufficient water and nutrients. It can be caused by diabetic neuropathy, hyperthyroidism or Bowel removal.
• Inflammatory diarrhoea: damage to the mucosal lining or brush border leads to a passive loss of protein-rich fluids, with causative Agents of bacterial, VIRAL, and parasitic infections, autoimmune problems, colon cancer.
• Dysentery blood is visible in the stools. , is an invasion of bowel tissue by Shigella, Entamoeba histolytica, Salmonellae.

Dehydration

• Diarrhoea leads to loosing of water and electrolytes (sodium, chloride, potassium, and bicarbonate) via liquid stools, vomit, sweat, urine, and breathing
• Dehydration ranges in three scales: Severe dehydration indicators are:
• Lethargy/unconsciousness, sunken eyes, inability to drink or poor drinking, and Skin pinch goes back very slowly (≥2 seconds)
• Some dehydration indicators are:
  • Restlessness, irritability, sunken eyes, drinks eagerly, thirsty
• No dehydration indicators: it has some signs, but not enough signs to classify as some or severe dehydration

Clinical Diarrhoea Types per the WHO

• Per the WHO there are three types of diarrhoeal:
  • Acute watery diarrhoea [Acute Gastroenteritis (AGE)] lasts for several hours or days.
    • Cases are caused by viruses (viral gastroenteritis).
  • Acute bloody diarrhoea (dysentery).
  • Persistent diarrhoea which lasts for more than 14 days

Viral Acute Gastroenteritis (AGE)

• Viral gastroenteritis is an infection resulting in vomiting or diarrhoea. It is often confused with the "stomach flu" which is not caused by the influenza viruses. Viral pathogens are the most common cause of gastroenteritis.

Symptoms of viral gastroenteritis

• Common symptoms include:
  • Nausea Vomiting Watery diarrhoea Signs of dehydration: Decreased urine output Dark-colored urine Dry skin Thirst Dizziness
• Other symptoms possible are: Headache Low grade fever Chills Stomach-ache (Abdominal pain)
• Signs of dehydration in young children:
  • Dry diapers (from a lack of urination), Lack of tears, Dry mouth, Drowsiness, and Sunken fontanel (the soft spot on the top of an infant’s head)

Transmission

The oral-fecal route spreads viruses that leads to gastroenteritis through close contact with infected persons & in ingestion of contaminated foods or beverages.

• All ages & Sexes Infants, young children, and the elderly, and immune compromised persons are at risk especially from dehydration stemming from to vomiting or diarrhoea

Reoviridae: Rotavirus

• The Rotavirus relates to Respiratory-Enteric-Orphan Viruses (Reovirus) and its genus are Orthoreovirus, Orbivirus, Rotavirus, Coltivirus.
• Its has a naked icosahedral symmetry that is 70-80 nm and is double shelled. Its Genome: 10 -12 segmented dsRNA causes Re-assortment of gene segments which can create hybrid viruses.
• Rota is the Latin word for wheel, where in human there are A (>90%) and the other is B, C, D, E (found in pigs), F, G, H, I, J.
• Transmission occurs via the faecal-oral spread, contact, and fomites (toys, other environmental surfaces contaminated by stool), contaminated food/water, & respiratory droplets.
• Diagnosis is possible via stool sample by ELISA or immunochromatography plus molecular detection of viral genome (PCR).
• Can also detect antibodies, identification (TEM) and culture of virus in faeces.

Rotavirus Diagnosis, Treatment

• There has been 3 classified Serogroups of HRV
• Currently supportive, 3 oral RV vaccines are licensed
• Ecology: very stable and viable (weeks - months if no disinfectant has been used).
  • It has a resistance to heat, organic detergents and non - ionic detergents, but is stable at a wide range of pH.
• It is common to species including cows and monkeys; animal strains are antigenically distinct from human strains.

Pathogenesis of Rotavirus

• The virus is ingested via the faeco-oral route and VP4 spike protein binds to receptors on enterocytes.
• Afterwards VP4 is cleaved by trypsin into VP8 and VP5 to enhance viral entry.
• The virus enters the cell by endocytosis which then replications occurs in viroplasms and synthesizes viral RNA and proteins.
• New virions are assembled and bud into the endoplasmic reticulum and get a temporary envelope that degrades and then form a triple layer.

Rotavirus Diarrhoea

• Causes diarrhoea through:
  • Infected villus enterocytes are destroyed which leads to villous blunting.
  • Results in malabsorption of nutrients and fluids, with NSP4 (Non-Structural Protein 4) acting as enterotoxin.
  • NSP4 stimulates secretion, triggers neural reflexes, increases gut motility & exacerbates fluid loss

Epideminology & Mortality: Rotavirus

• All ages & sexes can get Rotavirus, but it is the leading cause of severe diarrhea worldwide among children aged
• <5 year, the Elderly and people immuno-compromised,
• The Reservoir is in the GIT & the stool of infected humans.
• It is found worldwide, but the vaccine have strains absent in parts of the world. In the tropic: Harmattan, while in the winter: Temperate countries/ regions have outbreaks
• Globally, 185 390 children die annually under age 5,
• The Sub-Saharan Africa is has mortality rate of 66.9/100,000.

Caliciviridae: Norovirus and Sapovirus

• Norovirus is the winter vomiting disease/ small round structured virus (SRSV).
• HNoVs is responsible for 60 to 80% of all human gastroenteritis outbreaks worldwide
• It is an increasing problem in healthcare institutions and results in closed wards.
• Outbreaks of Norovirus are are more prevelant in Temperate Climate during the Winter.

Pathogensis, Treatment, Transmission: Norwalk and Norovirus

• Transmits via the ingestion of gastric acid and bile salts.
• Binding is done by HBGAs (histo-blood group antigens) on small intestinal epithelial cells which promotes attachment and entry.
• Itinfects intestinal enterocytes.
• Inside cytoplasm positive-sense the virus single-stranded RNA occurs Newly produced vitons are released from the gastro tract

Virology occurs via non-enveloped, icosahedral viruses that is composed in ssRNA in occurs by way of family and communities Diagnosis Differential, RT-PCR, ELISA and Immunochromatography; Treatment stems from oral fluid and administering buscopan with vaccines which can be contracted through person to person or from food

Mortality

• 212,000 deaths due to No Virus has been calculated.

Sapovirus

• Saporovirus is a former name and contains ssRNA of about 7,500 necleotides divided in GI-V subtypes where 1-2 and 4-5 are found in animals
  • Humans & swine contact infections, this is only found from sporatic cases for 14% to 17% and it can identified from the hospitals. ships & using ELISA an RT-PCR
• These will be found in greatest outbreaks of children with children affected it

Adenoviridae: Adenovirus strains 40 & 41

• Family: Adenoviridae
• Name origin: Adenoid cells.
• Capsid: medium-sized (90-100 nm); Non-enveloped; Icosahedral symmetry with the -Genome: being dsDNA organized in 7 species (A-G)
• Virus test is performed using a viral isolation

Pathogens

• Transmission: fecal-oral spread, touch & the fomites it can transport through
• Treatment: supportive that does not use a vaccine
• These are resistant to pH as they are hard agents that long after use on the skin.

Astroviridae

• With +ve sense, ssRNA is has a icosahedral that causes 2nd diarrhoea
• Was disovered after 1975 through Madeley & Cosgrove that is passed through transsions
• Is limited to the small intestine-with not affect stomach or the duodenum
• Is treated with : ELISA-PCR and self-limited, plus, it affects the elderly