Cryptosporodosis

Question 1

What is Cryptosporidium?

Answer 1

= coccidian protozoan parasite

= zoonotic disease and can travel from animals to humans (directly / via environment)

Source / Reservoir = infected animals (sheeps/cows) and infected humans

Associated with municipal water supplies = causes Diarrhea

= one of most common causes of waterborne illness

= zoonotic disease

Pathogenic form = oocyst

e.g. Cryptosporidium parvum
(recognised as human pathogen since 1976, wide host range including humans)
e.g. Cryptosporidium hominis
(almost exclusively parasite of humans)

Most famous outbreak
= Milkwaukee, Wisconsin = 403,000 infected

Question 2

What is the lifecyle?

Answer 2

1. Sporozites pentrate host cells and develop into trophozoites within parasitophorous in mucosal epithelium
2. Trophozoites undergo asexual division to form merozoites
3. Invasive merozoites (released from meronts) enter adjacent host cells = form type I (reinvade) and II
4. Type II enter host cells to form sexual stages (microgamont and macrogamont)
5. Fertilised to form zygote
   80% = develop into thick walled oocysts = form sporulated oocysts = contain sporozoites
   20% = develop into thin-walled oocyst = autoinfective life cycle

Question 3

What is the site of infection? How does cell death occur?

Answer 3

Brush border epithelial cells of small intestine (jejunum)

Cell membrane envelops them
= BUT they are intracellular / extracytoplasmic

Other affected tissues
= respiratory tract tissues , conjunctiva of the eye

Infectious dose
= <10 organsisms
= only need 1 to initiate

Cell death direct result of parasite invasion, multiplication + extrusion

OR cell death could occur through
= T cell mediated inflammation, producing microvilli death + cryptosporidium excess growth

Question 4

What are some Cryptosporidium virulence factors?

Answer 4

Excystation
= serine protease, aminopeptidase

Adhesion / locomotion
= CSL, Gp900, P23, P30 (+ more)

Invasion
= Phospholipase, Cp2, Cpa135 (+ more)

Intracellular multiplication / survival in the host
= Cysteine protease, Acetyl-co-synthetase, HSP70 (+ more)

Question 5

What is the mechanism of action of infection (Diarrhoea)?

Answer 5

= aspects of Diarrhoea

Osmotic
= characterised by enterocyte malfunction
= ↓ Na+ absorption
= ↑ Cl- secretion

Inflammatory
= generally associated with invasion of the mucosa inflammation of the lamina propria leukocytes in the stools

Secretion
= generally associated with bacterial entertoxins characterised by watery diarrhoea

Question 6

What are the symptoms?

Answer 6

Some individuals asymptomatic

Incubation: 2-10 days

= stomach cramps, pain, watery diarrhoea, dehydration, weight loss, vomiting, fever

Immunocompetent = 1-2 weeks

Immunocompromised = can be months / years

Question 7

What are the treatment options?

Answer 7

No effective therapy

Immuno-competent individuals recover with fluid and electrolyte replacement

Standard treatment of diarrhoea

AIDS patients = anti-retroviral therapy will reduce oocyst excretion and decreases diarrhoea

Question 8

What are some control methods?

Answer 8

Routine testing by Utilities
= use of 1 micron filter to remove cysts
= boil water

Drink bottled water when travelling abroad

Educate public

Wash hands frequently

Livestock control, management + practices