Parasites Flashcards
Difference between parasites and bacteria/viruses?
Nucleus and mroe complicated cell structure
Can be single-celled or multicellular
Protozoan vs helminths?
Single celled vs multicellular
Which major global parasitic infections have been prevented by vaccines?
None - possibly due to evolution allowing them to hide from immune response, possibly from lack of research
Where are most parasitic locations? WHy?
Africa and south Asia due to poverty levels
% of deaths from infectious disease in developped vs developping
5% in developped, 50% in developping
Prevalence and at risk population of Ascariasis
807 million, 4.2 billion
Prevalence and at risk population of Trichuriasis
604 million, 3.2 billion
Prevalence and at risk population of Hookworm
576 million, 3.2 billion
Prevalence and at risk population of Schistomiasis
207 million, 1.3 billion
Prevalence and at risk population of lymphatic filariasis
120 million, 1.3 billion
Prevalence and at risk population of onchoceriasis
37 million, 90 million
Length, lifespan and eggs per day of Ascaris
20cm, 1 year, 200,000 eggs per day
Length, lifespan and eggs per day of trichuris
5cm, 2 year, 5000 eggs per day
Length, lifespan and eggs per day of hookworm
15mm, 5 year, 10,000 eggs per day
What helminths fall into the category of STH (soil transmitted helminths) // how much of the world is at risk
Ascaris, Trichuris, Hookworm - 1/3
Where do STH reside, how are they transmitted
gastrointestinal tract, transmitted into soil via eggs that are excreted in the feces (Ascaris and Trichuris - contamination of water, food) or by penetration of the larvae through the skin (hookworm)
Effects of STH // deaths per year
malnutrition, growth stunting, cognitive defects and can suppress immune system
50,000 deaths per year
Life cycle of Ascaris
- small intestine (d)
- fertilized eggs in feces contaminate environment (d) (unfertilized are not infectious)
- larvae develop to infectivity (i)
- ingestion
- larvae hatches in small intestine
- detour to lungs
- back to GI tract
Hookworm lifecycle
- eggs in feces (d)
- rhabditiform larva hatches
- filaform larva
- skin penetration (i)
- travel to GI via lungs
Conditions favoring STH
Poverty, poor water filitration, muddy/wet roads and infrastructure
Measuring intensity of infection?
of eggs per gram of feces (microscopically analyzed)
STH treatment (goal, drug types)
Treatment removes adult worms - reduces worm burden, although reinfection is almost inevitable
Regular treatment in schools (age 5-12)
Drugs: Benzimadoles & ivermectin
Lymphatic filariasis: alternate name, life cycle
Elephantiasis: blocks flow of lymphatic fluid (swelling in feet)
1. L3 larvae enter skin from mosquito
2. adults in lymphatics
3. produce microfilariae into lymph and blood (d)
4. ingested by mosquito
5. develop into larvae
Onchocerciasis: alternate name, transmission
River blindness: transmitted by blackflies, microfilaria accumulate in eye causing blindness (destroys retina)
