BIOL334- Cryptosporidiosis

Question 1

What is Cryptosporidium?

Answer 1

• A protozoan parasite

Question 2

Which species of Cryptosporidium genus causes Cryptosporidiosis?

Answer 2

• Cryptosporidium parvum

Question 3

Where is Cryptosporidium found?

Answer 3

• Municipal (cities, towns, urban) water supplies

Question 4

What does the pathogenic form of C.parvum look like?

Answer 4

• An oocyst

- 3 micrometres in diameter (half the size of a blood cell)

Question 5

What is the reservoir for Cryptosporidium?

Answer 5

• Hosts are animals (mainly livestock) and humans

Question 6

What type of disease is Cryptosporidiosis

Answer 6

• Zoonotic disease (travel from animals to humans)

Question 7

Which hosts does C.hominis impact?

Answer 7

HUMANS ONLY

Question 8

Describe the lifecycle of Cryptosporidiosis

Answer 8

1. Following ingestion by a suitable host excystation occurs (escapes cyst stage)
2. The sporozoites are released and parasitise the epithelial cells of the GI tract.
3. In these cells, the parasites undergo asexual and sexual multiplication producing microgamonts (male) and macrogamonts (female)
4. Zygotes form and give rise to thick walled and thin walled oocysts
5. Thick-walled oocysts are secreted into the environment (by the host) where as thin walled oocysts are involved in the internal autoinfective cycle.
6. Oocysts are infectious upon excretion thus enabling direct and immediate faecal oral transmission.

Question 9

Cryptosporidium virulence factors

Answer 9

• Cyst- excystation into trophozoite form= adhesion and locomotion genes ( a whole range including P23 and P30).
• Invasion: virulence factors Cpa2 and phospholipase
• Intracellular multiplication and survival: lots of genes such as CpATPases

Question 10

How does Cryptosporidium cause its symptoms?

Answer 10

1. Glucose coupled Na+ absorption is decreased and Cl- secretion is increased (osmotic effect)
2. Associated with this is disruption of the intestinal epithelial cell function- blunting of microvilli and crypt hyperplasia
   - Infection of epithelial cells with C.parvum damages intestinal cells and eventually leads to their death
   - This leads to cell division (hyperplasia) in the crypt region to replcace damaged cells
3. The combination of destruction of absorptive cell tips of the microvilli and increased Cl- secreting crypt cells leads to enhanced secretion
4. In addition, an increased intracellular permeability and inflammation in the submucosal layer is associated with C. parvum infection
5. Secretion generally associated with bacterial enterotoxins characterised by diahorrea.

Question 11

Cryptosporidiosis symptoms

Answer 11

• Some individuals asymptomatic
• Incubation period 2-10 days
• Stomach cramps/pain, watery diahorrea, dehydration, weight loss, fever
• Immunocompromised patients experience the symptoms for longer

Question 12

How do we treat Cryptosporidiosis?

Answer 12

• No effective therapy
• Immuno-competent individuals will recover with fluid and electrolyte replacement (recover 1-2 weeks) (standard treatment for diahorrea- rehydration)
• AIDs patients: anti-retroviral therapy will reduce oocyst excretion and decreases diahorrea

Question 13

Control Methods for Cryptosporidiosis

Answer 13

• Routine testing United Utilities (use 1 micron filter to filter water, boil water)
• Drink bottled water when abroad
• Educate public
• Wash hands frequently
• Livestock control, management and practices