MICRO: Global health priorities and brain worms Flashcards
What did the Alma Ata Declaration 1978 reinstate?
Reinstated the definition of health: a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity
What two factors does DALY encompass?
Morbidity and mortality
DALY = YLL + YLD
- YLL= No of deaths * standard life expectancy at time of death
- YLD=No of incident cases * disability weight * average duration of case
What does 1 DALY mean?
1 DALY = 1 lost year of healthy life lost
What is a QALY?
- Measure of disease burden
- Includes both quantity and quality of life lived
- Used in assessing the value of a medical intervention
- Based upon the number of years of life that would be added by the intervention
What is 1 QALY?
A year in the hypothetical state of “perfect health” is worth 1 QALY.
Being deceased is worth 0 QALYs.
Other health states fall between 0 to 1
How are standard and new treatments comapred in terms of benefit to the quality of life?
Patients receiving standard treatment will live for 1 year and quality of life will be 0.4 (0 = worst possible health/death, 1= perfect health)
Patients receiving new drug will live for 1 year 3 months (1.25 years), with a quality of life of 0.6.
The new treatment is compared with standard care in terms of the QALYs gained:
- Standard treatment: 1 (year’s extra life) x 0.4 = 0.4 QALY
- New treatment: 1.25 (1 year, 3 months extra life) x 0.6 = 0.75 QALY
Therefore, the new treatment leads to 0.35 additional QALYs (that is: 0.75 -0.4 QALY = 0.35 QALYs).
The cost of the new drug is assumed to be $10,000, standard treatment costs $3000.
The difference in treatment costs ($7000) is divided by the QALYs gained (0.35) to calculate the cost per QALY. The new treatment would cost $20,000 per QALY.
Why is QALY debated?
- What is perfect health? Not patient-centric
- There may be a health state worse than death
3 helminths families
cestodes - tapeworms
trematodes - flukes
nematodes - roundworm
what is a hydatid?
dog/fox tapeworm
human’s are accidental hosts - cysts form in organs e.g. liver
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
What is the source of Taenia solium cysticercosis?
Pork tapeworm larvae - common in all non-Muslim developing countries
beef tapeworm can’t infect humans as intermediate host
how do you get the tapeworm vs cysticiccosis
cysticocossis - human is the intermediate host (where the pig would be in lifecycle) - so you get it from contaminated vegetables
tapeworm - from eating infected pork)
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 tineasis?
- 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.
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 tinea solerium 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
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 contamintated with faeces so vegetarians and meat eaters can all be affected
What sites are infected by cysticercosis?
ALL tissues in the body canbe affecte (incl. muscle and heart)
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 staten
- also stroke, blindness, spinal disease
How do neurocysticercosis parasites surive in the body?
Evade and suppress inflammation by…
- sequestration/fibrous encapsulation
- concomitant immunity
- molecular mimicry/masking
- modulation of host immunity
What is likley to be happening if you get symptoms with neurocysticercosis?
- Usually, living cysts are asymptomatic
- Symptoms mark cyst degeneration
- Associated with eosinophilic cellular influx
What is the management of neurocysticercosis?
Anticonvulsant therapy
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
- partial effect for cyst degeneration/cestocidal therapy
- inadequate for: chronic granulomatous inflammation
- heavy infections – cestocidal therapy without steroids may be fatal
