GIT infection part B Flashcards
What is viral diarrhoea?
- Non-bacterial gastroenteritis usually caused by viruses
- Major disease burden around the world
- Major cause of infant death in underdeveloped countries
- Transmission through faecaloral route
What is the rota virus? Discuss its viral structural features, pathogenesis, clinical features
Family: Reoviridae
Genus: Rotavirus
- Non-enveloped double stranded RNA virus
- Cause of severe diarrhoea in infants and children
- Strains G1-4, G9 are most common strains
- Very stable and may remain visible for weeks or months if not disinfected
- Transmission: Faecal-oral route
Rotavirus Pathogenesis
- Replicates in the epithelium of small intestine
- Infection leads to isotonic diarrhoea
- Single infection may not give protective immunity
Rotavirus: clinical features
- Major cause of severe dehydrating gastroenteritis in both developed and developing countries
- Short incubation period (usually less than 48 hours)
- Symptoms can begin abruptly – often vomiting happens before diarrhoea
- Symptoms can vary from asymptomatic to severe dehydrating diarrhoea with fever and vomiting •
- Common cause of hospitalisation for gastroenteritis
- Gastrointestinal symptoms generally resolve in 3 to 7 days
Rotavirus: Epidemiology
Before vaccine = 1 death to rota virus each year in australia (50% of hospitalisation for acute gastroenteritis)
After vaccine (2007) = decline in hospitalisations and ED presentations
Rotavirus Vaccination
- Two oral live attenuated rotavirus vaccines are available in australia
What is hepatitis?
Hepatitis = inflammation of the liver
Causes
- viral infection, bacterial or protozoal disease, toxins e.g. ethanol drugs
Symptoms
- Fever, GI abnormalities like nausea and vomiting, jaundice and enlargement of the liver
- Jaundice –.> yelllow hue to the skin and eyes
> Inability of the liver to eliminate billirubin (breakdown product of haemoglobin) –> becomes deposited in the skin giving it a yellow hue
What is Hepatitis A virus? Describe its viral structural features, clincal features, epidemiology and vaccine
- Hepatitis A virus is a picornavirus ▪ i.e. Related to poliovirus
- Single-stranded RNA genome
- Naked virus – no envelope –> like rota virus
- Only one serotype known
- Heat and acid stable and may last for long periods at room temperature
- Destroyed by autoclaving, UV, formalin or chlorine but infected patients require special caution
Clinical Features
Children: infection usually mild (often subclinical)
- Jaundice uncommon
- Can have flu like symptoms + diarrhoea
Adults: more sever disease
- 2/3 have jaundice but diarrhoea is less common
- post hepatitis - weakness or lethargy, alcohol intolerance and prolonged jaundice
- Hepatitis A does not give rise to chronic carriers or chronic liver disease
Transmission and epidemiology
- Transmission by faecal-oral route + contaminated food and water
- HA is prevalent in poor environmental sanitation and hygiene places
- If live in australia, and go to endemic area = very susceptible to infection
Hepatitis A vaccines
- Inactivated (killed viruses) –> prepared from virus grown in human cell cultures
- Hep A vaccine on its own or with Hep B vaccine
- Hep A vaccine not broadly required in aussie population –> for abos and travellers to endemic countries
What is Hepatitis B virus? Describe its viral structural features, clincal features, serology, epidemiology and vaccine
- HBV is an Hepadnovirus (dsDNA)
- Circular double-stranded DNA genome
- Enveloped
- Numerous antigenic components
- Humans are only host
Hepatitis B virus Infection
- Cause of chronic hepatitis and cirrhosis
Hepatitis B clinical features
- Incubation period –> (average 120 days)
- Nonspecific prodromal symptoms: malaise, fever, headache, myalgia i.e. symptoms not specific for hepatitis B
- At least 50% of infections asymptomatic
Complications
- hospitilzation - recovery can take weeks to months
- Chronic Hep B virus infection –> cirrhosis, hepatocellular carcinoma, death
- Overall risk 5 percent among adults
- Often asymptomatic but infectious
Hepatitis B Serology
- Hep B serologic testing involves measurement of several hepatitis B virus (HBV) –> specific antigens and antibodies
- Different serological markers are used to determine whether patient has acute or chronic HBV infection, is immune to HBV as a result of prior infection or vaccination, or is susceptible to infection
Hepatitis B epidemiology
- Transmission is blood-borne/sexual contact
- Communciability: 1-2 months before and after onset of symptoms –> persons with either acute or chronic HBV infection with HBsAg present in blood
- HBV is worldwide in distribution
HBV vaccination
- Vaccine uses recombinant DNA technology
- HBV is hard to grow in the lab
- Purified HbSaAg protien is adsorbed (contains 1 % yeast)
- Dose at birth followed by 3 doses
- Single vaccine and combo vaccines available (infanrix hexa)
What is Hepatitis C virus? Describe its viral structural features, clincal features,epidemiology, and prevention and control
- HCV is from the family Flaviviridae of the genus hepacivirus
- Single-stranded RNA genome
- HCV displays genomic diversity with different genotypes predominating in different parts of the world •
- It undergoes sequence variation (antigenic drift) during chronic infections
- An individual patient can have numerous variant at one time
Clinical Features of HCV
- HCV is usually clinically mild, with limited to moderate elevation of liver enzymes
- Hospitilisation is unusual (< 25 % of cases)
- About 75% progress to chronic liver disease
- Most patients are asymptomatic until late progression
- Leads to hepatocellular carcinoma (HCC)
HCV transmission and epidemiology
Transmission - blood to blood contact (blood borne), through:
- Re-used of injecting equipment by drug users, 80%
- Haemophiliacs, 10%, Hemodialysis patients, 10%
- High risk sexual practices and mother to infant
Epidemiology
- 3% of whole population infected
- Estimated 130-150 million chronic carriers worldwide
HCV prevention and control
Vaccine: No vaccine for HCV
- HCV is very variable - 6 major types with many subtypes
- No good animal models to study the disease
- There is a lot of geographical variation in the types
Treatment: interferon alpha and anti-viral drugs are used
Current control measures focus reducing risky behaviour
What are protozoas and how are they transmitted?
- Many protozoa live in GI tract; only a few are pathogenic
- Infect average 3.5 billion people worldwide
- Single cell, free-living, eukaryotic organisms
- Life cycle: trophozoite (motile, feeding, dividing) and cyst stages (dormant, usually infective stage)
Protozoa Transmission
- Mostly faecal-oral route
- Different life cycle stages, cysts more stable in environment –> pass into faeces already infective or soon to be
- Cyst appearance can be used to distinguish between Pathogenic and non-patho.
What is Entamoeba histolytica (E.histolytica) Discuss its infection and clincal features
E.histolytica
- Occurs worldwide, mainly in tropical and sub tropical countries
- Trophozoite lives on mucosa of large intestine
- Cyst passes out in faeces –> ineffective
Clinical Symptoms
- Mild diarrhoea due to small locaslised ulcers
- dysentery caused by deep ulcerations of mucosa: blood and mucus in diarrhoea
- Treatment = metronidazole/ tinidazole →trophozoite, to eradicate → antimoebics
What is Giardia intestinalis? (G.intestinalis) Discuss its infection and clinical features
The first intestinal microbe view under a microscope, 1681, van Leeuwenhoek
- Worldwide distribution, Traveller’s diarrhoea
- Life stages: flagellate trophozoite, cyst
- Trophozoite attach to mucosa of upper small intestine, large numbers can cover mucosa
- Transmission – mainly through contaminated drinking water, transmitted sexually
- Clinical symptoms:
>Asymptomatic – self-limiting, 7-10 days ▪
Chronic – can become serious, through inflammatory response, particularly in the immunocompromised •
- Treatment: metronidazole/ tinidazole, among others
What is C.hominis (cryptosporidium infections)? Describe its infection and clinical features
Cryptosporidium hominis – causes human infections
- Life cycle: complex, going through sexual and asexual phases in host - Infection – oocysts shed in faeces, only after microbe sexual reproduction
- Transmission usually through contaminated water
- Clinical features
> causes watery diarrhoea, moderate through to severe in immunocompetent individuals
>in immunocompromised (e.g. AIDS) can become chronic and even life-threatening
- Diagnosis: through facial examination (cyst will be in faeces), conc technique
- Treatment: only in immunocompromised patients
