Viral + Protozoal Infections

Question 1

Name 2 viral and 3 parasitic/ protozoan causes of Gastroenteritis

Answer 1

Viral;

• Rotavirus
• Norovirus

Parasitic/ protozoal;

• Cryptosporidium
• Giardia
• Entamoeba

Question 2

Describe Rotavirus and state 3 symptoms

dsDNA, Treatment: Manage dehydration

Answer 2

• Very common under 5 years of age (adults rarely infected due to immunity buildup)
• Very small dose needed for infection
• Initially, Vomiting with fever
• Diarrhoea follows (lasting up to a week)

Question 3

How does Rotavirus cause Diarrhoea in 3 ways?

Answer 3

1. Cl secretion;
   - Increase in cAMP opens CFTR protein, so more Cl enters gut lumen
2. SGLT1 disruption;
   - Reduced Na/ glucose movement into enterocyte, so increased osmosis of water into gut
3. Brush border dysfunction;
   - General malabsorption

Question 4

Describe Norovirus/ Norwalk Virus

Most common cause of non-bacterial gastroenteritis globally

Answer 4

• Can affect any age (No immunity as many strains)
• Small dose needed to get infected
• Virus resistant to cleansing
• Incubation: 1-2 days, Symptoms last 1-3 days
• Infects SI and damages microvilli

Question 5

Lis 3 symptoms of Norovirus infection

How is it treated?

Answer 5

• Vomiting (due to delayed gastric emptying)
• Fever
• Watery Diarrhoea

Oral rehydration therapy

Question 6

Compare the mobility of the 3 common Protozoa that cause Gastroenteritis

Answer 6

Cryptosporidium;
- Is a sporozoan, so non-motile

Giarda;
- Flagellate, so is motile

Entamoeba;
- Motile, by extension of cytoplasmic projections

Question 7

How is Cryptosporidium spread?

Answer 7

• Faecal oral route

- Via bodies of water infected by animal faeces

Question 8

Describe the pathophysiology of Cryptosporidium infection

Answer 8

• Ingestion of an Oocyst containing the parasite
• Parasite reproduces inside SI’s epithelial cells
• Oocysts excreted in faeces

Question 9

How is infection by Cryptosporidium treated?

What kind of diarrhoea does it present with?

Answer 9

• Supportive treatment (fluids)
• Anti-parasitic treatment in some people (E.g AIDS)

Watery diarrhoea

Question 10

Most Giardia infections are asymptomatic but symptoms are more common in children.

How is it spread?

State the incubation period and 2 possible symptoms

Answer 10

Faecal oral route, with water supplies often affected

After 10 days,;

• Diarrhoea (Commonly causes persistent diarrhoea)
• Ab cramping (for up to 6 weeks)

Question 11

Describe the 2 stages of the Life Cycle of Giardia

Answer 11

1. Cyst ingested;
   - HCl + Pancreatic enzymes release parasite from cyst
   - Multiplies in and damages SI (Incubation period of 1-2 days)
   - Villous atrophy occurs
2. Parasite returns to cyst stage in colon;
   - Excreted to repeat cycle

Question 12

How is Giardia infection treated?

What is a common consequences of Giardia infection?

Answer 12

Antibiotics and fluid rehydration therapy

Post infection, Lactase deficiency is common-> Lactose intolerance

Question 13

Infection by Entamoba is mostly asymptomatic, suggest 2 symptoms

How is it spread?

Suggest a group of people likely to be affected OTHER than those in poor sanitary conditions

Answer 13

• Diarrhoea (bloody)
• Liver abscess (infection spread to liver, rare)
• Spread by faecal-oral route
• Men who have sex with men

Question 14

Describe the pathophysiology of infection with Entamoeba

Answer 14

• Ingestion of cyst
• Excystation in colon, where trophozoites invade mucosa (bloody diarrhoea + inflammation), can spread to liver
• Cysts then pass out with faeces

Question 15

State the treatment of infection with Entamoeba

Answer 15

• Anti protozoals (metronidazole)

- Severe colitis/ toxic megacolon may need surgery

Question 16

Symptoms for more than how long make bacteria less likely to be the cause of diarrhoea?

Which Blood group increases risk of diarrhoea?

Answer 16

14 days

Blood group O