Pathogens (Fritz Lecture 4 - Tapeworms)

Question 1

What is (Neuro)cysticercosis?

Answer 1

Parasitic tissue infection caused vy larval cysts of the tapeworm taenia solium

Question 2

Cysticercosis is the most common parasitic infection of what?

Answer 2

The CNS

Question 3

What are the symptoms of neuro cysticercosis?

Answer 3

• Commonest cause of adult-onset epilepsy in endemic areas
• can cause seizures and headaches
• may cause confusion, difficulty balancing, brain swelling, stroke (less common)

Question 4

What is Taeniasis?

Answer 4

Parasitic infection of tapeworms of the genus Taenia

Question 5

How does Taeniasis by Taenia solium occur?

Answer 5

• Ingestion of poorly cooked pork meat
• Attaches to the mucosa of small intestine
• Usually asymptomatic

Question 6

What is the life cycle of Taenia solium?

Answer 6

• 2-3 months after human infection, gravid proglottids detach and release eggs
• Eggs in human faeces ingested by pigs (intermediate host)
• Oncospheres hatch in pig intestine, migrate to muscle, develop into cysticerci
• Humans consume cysticerci in undercooked pork

Question 7

How does Human Cysticercosis occur?

Answer 7

Ingestion of T solium eggs from human faecal contamination

Question 8

How do the tapeworm cysts (eggs) cause Neurocysticercosis?

Answer 8

• Cysts lodge in capillaries (brain or eye) and mature (3 months)
• Protected from immune cells by blood-brain barrier
• Cyst death causes inflammatory response causing oedema and then calcification

Question 9

What are the physical manifestations of neurocysticercosis?

Answer 9

• Obstruction due to parasite
• Inflammatory response (oedema)
• Scarring (calcification)

Question 10

Neurocysticercosis is classified by 4 locations and 4 stages. What are they?

Answer 10

Locations:

• parenchymal
• subarachnoidal space
• intraventricular
• spinal

Stage:

• vesicular
• colloidal
• granular
• calcified

Question 11

What are the 3 main methods used to diagnose neurocysticercosis?

Answer 11

1) Serology (diagnostic examination of blood serum)
2) PCR
3) Imaging

Question 12

What is done in serology diagnosis? Should it be used on its own? If no, what other technique should be used?

Answer 12

Enzyme-linked immunoblot assay (ELISA) of either serum or CSF

• CSF ELISA more senstivie
• Should be used in conjunction with imaging

Question 13

How is imaging used to diagnose Neurocysticercosis?

Answer 13

CT scans can show stage of disease based on several parameters

Question 14

How is PCR used to diagnose NC?

Answer 14

Based on amplification of repetitive pTsol-9 DNA fragment in CSF
- Correct identification in 29/30 cases