MICRO: Global health priorities and brain worms Flashcards
Case:
- 42 year old man originally from Ecuador
- 1 month occipital headache
- 3 generalised tonic-clonic seizures, spontaneous recovery
- 1 previous seizure in Ecuador 1985, no medications
- Works as a cleaner
- Lives with wife & 3 sons, 1 of whom has epilepsy (age 19)
- 5 cigarettes/week, occasional alcohol
Cystic lesion seen below.
Calcification is also seen (reverse) in the brain.
Cyst + calcification = Taenia solium cysticercosis
How would we manage this patient?
Epilepsy
- Anticonvulsants - phenytoin
- Advised not to drive
Cerebral inflammation and oedema
- Corticosteroids - dexamethasone
Kill viable cysticerci
- Cestocidal drugs - albendazole
Family screening
What is the source of Taenia solium cysticercosis?
Pork tapeworm larvae - common in all non-Muslim developing countries
What is Taenia solium cysticercosis often misdiagnosed as?
Commonest cause of adult-onset epilepsy in many countries, causes 20-30% of adult-onset epilepsy in Peru
What two tapeworms can cause intestinal infection/taeniasis in humans? How severe is taniasis?
- Intestinal infection with adult stage of large tapeworms
- T. solium
- T. saginata
- Generally non-fatal - usually asymptomatic, may live for many years and grow up to 30m.
- Eggs released intermittently - need 3 stool microscopies
What tapeworm causes cysticercosis? How severe is the infection?
Tissue infection with larval stage of T. solium
- Serious disease that usually involves the CNS. Infection may be fatal
How do pig get infected with porcine cysticercosis? What type of Taenia solium infection is caused by eating infected under-cooked pork?
Pig infection by:
- Pigs ingest tapeworm eggs in human faeces
- Parasites migrate to tissues & encyst - measly pork (“measly” = cystic)
Humans eating pigs only causes intestinal tapeworms.
Describe the life cycle of Taenia solium infections.
It is caught from other humans (faeces/GI spread) and cysticercosis is a dead end for the spread of the disease
What is the route of infection for human cysticercosis?
Ingestion of tapeworm eggs - in food contaminated with faeces
Usually travelling in non-Muslim areas
So vegetarians and meat eaters can all be affected
What sites are infected by cysticercosis?
ALL tissues in the body can be affecte (incl. muscle and heart, BRAIN)
Still a possible cause if it is endemic in the area where you live, despite you being vegan/vegetarian/never eating pork
What are the clinical features of neurocysticercosis?
Brain cysticerci are the most frequent cause of symptomatic disease
Clinical features depend on the immune response, number & site of cysts e.g.
- 65% epilepsy
- 24% raised intra-cranial pressure
- 22% headache
- 14% altered mental state
- Also stroke, blindness, spinal disease
How do neurocysticercosis parasites survive in the body?
Evade and suppress inflammation by…
- Sequestration/fibrous encapsulation
- Concomitant immunity
- Molecular mimicry/masking
- Modulation of host immunity
What is likely to be happening if you get symptoms with neurocysticercosis?
- Usually, living cysts are asymptomatic
- Symptoms mark cyst degeneration
- Associated with eosinophilic cellular influx
Death of cyst causes symptoms
What is the management of neurocysticercosis?
Anticonvulsant therapy e.g. phenytoin
Ventriculo-peritoneal shunt (if hydrocephalus occurs)
Cestocidal drugs (albendazole or praziquantel)
- Accelerate disappearance of viable cysticerci
- Cause transient inflammation around viable cysticerci
- Randomised trials suggest clinical benefit
Steroids for inflammation around dying cysts before / during / after treatment
- Partial effect for cyst degeneration/cestocidal therapy
- Inadequate for: chronic granulomatous inflammation
- Heavy infections – cestocidal therapy without steroids may be fatal
