Protozoal and Helminthic Infections

Question 1

What are is the life cycle of Giardia lambila

Answer 1

Trophozoite - Flagellated, binuclear. It adheres to the brush boarder of the upper small intestine.
Cyst - It has a resistant wall which is formed in a large intestine and passed out in the faeces.

Question 2

Describe the pathogenesis of Giardia lamblia

Answer 2

The protozoa attaches to the wall of the upper small intestines via ventral sucker. It causes villous atrophy and therefore malabsorption. The cysts can remain viable for 24-48 days and can gain access to biliary system and reside in the gall bladder.

Question 3

Describe the clinical presentation of giardia lamblia

Answer 3

• Self-limiting diarrhoea which can be foul-smelling and fatty stool. In immunocompromised individuals chronic infection can occur.

Question 4

Describe features cryptosporidium parvum

Answer 4

It is a spore-forming single celled intracellular parasite which is naturally resistant to chlorination. It causes 25-30liters of watery diarrhoea a day which can be life threatening in children and immuno-compromised however otherwise it is a self limiting illness.

Question 5

Briefly describe the life cycle of cryptosporidium parvum

Answer 5

It is complex. First sporulated oocytes are ingested from the environment. The sporozoites attach to the surface of the intestinal epithelium and enters the cell. After sexual phase, oocytes are released in the faeces

Question 6

Describe the pathogenesis of Entamoeba histolytics

Answer 6

• Cysts ingested undergo excystation in terminal ileum and adhere to epithelial cells of large intestine. There is then enzymatic penetration into blood vessels. Trophozoites ‘feed’ off lysed cells which causes bloody diarrhoea. Resistant cysts pass out in stool

Question 7

Describe the clinical manifestation of entamoeba histolytics

Answer 7

Spectrum of clinical presentation from small superficial ulcers causing mild diarrhoea to severe ulceration of colonic mucosa causing amoebic dysentery. Some trophozoites may spread to the liver and cause an abscess.

Question 8

What are the different divisions of helminths

Answer 8

Nematodes, crestodes and tremtodes.

Question 9

Describe the transmission of nematodes

Answer 9

• Often via soil. It can spread by swallowing infective eggs. The larval skin migrates through lung to intestine. It is diagnosed by stool microscopy

Question 10

Describe pathogenesis of strongyloides stercoralis

Answer 10

• It causes disruption of intestinal mucosa which causes villous atrophy. It is once of the only nematodes to exhibit auto-infection.

Question 11

Describe the clinical presentation of stringyloides stercoralis

Answer 11

• Diarrhoea, malabsorption, anal pruritis, dehydration

Question 12

Describe how trichuris trichiura is acquired and how it manifests

Answer 12

Acquired through ingesting eggs and it manifests as;

• Asymptomatic if mild infection,
• Abdominal pain,
• Nausea,
• Bloody Diarrhoea,
• Rectal prolapse

Question 13

Describe how is at highest risk of developing ascaris lumbricoides and how it manifests

Answer 13

Higher risk - countries with poor sanitation and unwashed fruit and veg. Manifestation;

• Asymptomatic if mild,
• Allergic reactions,
• Intestinal obstruction,
• Malnutrition,
• Loffler’s syndrome (esosinophils accumulating in lungs)

Question 14

Describe features of enterobius vermicularis

Answer 14

• Females migrate to anus at night and lays 1000s of eggs. It causes intense itching, inflammation, diarrhoea and eosinophilia

Question 15

Describe features of Ancyclostoma duodenale

Answer 15

The larvae penetrates skin, enters the blood stream and migrates to the gut where it attaches to the small intestine and females lay eggs.
It causes iron deficiency anaemia due to blood loss.

Question 16

How does taenia solium manifest?

Answer 16

Abdominal pain/cramps, nausea, diarrhoea, +/- weight loss