Lecture 17: Viral Enteric Pathogens

Question 1

Enteric Pathogens: Bacteria

Answer 1

Salmonella spp.
Shigella spp.
E. coli
Campylobacter spp.
Yersinia spp.
Clostridium difficile

Question 2

Enteric Pathogens: Viruses

Answer 2

Rotavirus
Norovirus
Astrovirus
Adenovirus
Enterovirus

Question 3

Enteric Pathogens: Parasites

Answer 3

Entamoeba histolytica
Giardia lamblia
Cryptosporidium

Question 4

Viral Gastroenteritis

Answer 4

• Nov-Feb in Canada
• 1-3 days of duration
• Acute nausea and vomiting
• 2nd to upper resp infections
• Most common in 1-10yrs

Question 5

Viral Gastroenteritis Syndromes

Answer 5

Biggest issue = dehydration
- Make sure to eat electrolytes
- Mild afebrile illness with watery diarrhea
- More severe febrile illness with watery diarrhea, vomiting, headache, and constitutional symptoms

Question 6

Established Pathogens

Answer 6

• Norovirus
• Rotavirus (Infantile gastroenteritis)
• Astrovirus - can give you conjunctivitis, pharyngitis, gastroenteritis all at the same time (enteric types)
• Caliciviruses (other than noro)

Question 7

Likely and emerging pathogens

Answer 7

• Coronaviruses
• Enteroviruses - can lead to meningitis
• Torovirus
• Picornaviruses
• Pestiviruses

Question 8

Norovirus

Answer 8

• Nonenveloped
• SS positive-sense RNA genome
• Member of Caliciviridae family
• Airborne and vomitus transmission
• 18-72 hrs of incubation
• Virus shedding in stool

Question 9

Noro Epidemiology

Answer 9

• Outbreaks common in closed settings (Hospitals, nursing homes, ships, military, uni res)
• Outbreaks terminate spontaneously after 1-2 weeks
• Transmission also from food that have been in contact with contaminated water

Question 10

Noro signs and symptoms

Answer 10

• Gradual or abrupt onset of illness
• 1st complain of ab cramps and/or nausea
• Usually vomiting and diarrhea occurs with vomiting being the prominent feature
• Fever with 4-8 non-bloody stools/day

Question 11

What is significance of blood in stool

Answer 11

Invasion of GI mucosa } viruses usually don’t do this -> bacteria does

Question 12

Treatment/Hospital Control Measures for Noro

Answer 12

• Oral fluid replacement with isotonic liquids
• Symptomatic treatment
• No antibiotics!!
• Stabilize + rehydrate patient!!

Question 13

Rota

Answer 13

• Reoviridae family
• ONLY double stranded RNA genome
• Non-enveloped
• Not deadly but vaccine is given bc country loses billions a year w employees being sick

Question 14

Rota Serogroups

Answer 14

A, B, C - human and non-human disease
a= most important clinically; endemic gastroenteritis in kids
b+c= associated w epidemic gastroenteritis affecting all ages
d->g= non-human disease

Question 15

Rota epidemiology

Answer 15

• Cause severe, dehydrating gastroenteritis in < 5 yr olds in all socioeconomic groups worldwide
• Peak severe disease 6 months - 2yrs
• Kids acquire serum antibody in first 2-3 yrs of life
• Africa, SE Asia, S America

Question 16

Rota Transmission

Answer 16

• Fecal-oral transmission
• Virus detected in still 4-10 days after sympt.
• Outbreaks in daycare, playgroups, families, nursing homes, and hospitals

Question 17

Rota Pathogenesis

Answer 17

• Not understood
  Potential roles of: malabsorption related mucosal damages and depression of disaccharides, shortened and blunted villi in duodenum with crypt hypertrophy and mononuclear infiltration
  Comes in, infects, lytic, replicates, then your over it

Question 18

Rota signs and symptoms

Answer 18

DEHYDRATION = biggest risk
- Begin w vomiting and fever 2-3 days
- Progress to profuse watery diarrhea for 4-5 days
- Sympt range
- Most severe symptom w dehydration compared to other enteric pathogens and infants and young children

Question 19

Rota Treatment

Answer 19

• Rehydration, restoration of electrolytes
• Oral rehydration solutions preferred for mild or moderate cases
• IV for severe cases
• NO antibiotics

Question 20

Rota Control of transmission

Answer 20

• Hardy virus - non enveloped virus
• able to survive on fomites for up to 2 days at RT 85% humidity
• 10 days at 4oC at 25-50% humidity
• Handwashing, contact precautions till symptoms resolve
• Sick employees should NOT come to work

Question 21

Lab Diagnosis for Enteric Viruses

Answer 21

• Neither virus can be propagated in vitro
• High viral loads in stool enables - Electron-microscopy for virus diagnosis
• PCR is the mainstay of diagnosis now
• Antigen detection is also available