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)
Theory concerning helminth infections and autoimmune
May reduce autoimmune disease by reducing the overall inflammation (prolongs survival of helminths in GI, but reduces risk of autoimmune diseases)
DALY?
Disability adjusted life years (healthy years lost)
Where is malaria most common?
Around equator, South America, Africa and South Asia (allows for year round transmission)
Plasmodium: alternate name, life cycle
Malaria:
1.Infection (blood meal)
2. travel through blood to liver -> sporozoites
3. merozoites in RBCs
4. gametocytes (retransfer to mosquitos)
Stops blood flow by increasing blood stickiness, clots in brain kill
Malaria noble prizes
1907: cause (parasite in blood)
1902: transmission (parasite in mosquito)
2015: medicine
Human African Trypanosomiasis: alternate name, distribution, transmission, life cycle
Sleeping sickness, middle of Africa, Tsetse fly
1. injection of T. brucei into blood
2. multiplication by binary fission (blood, lymph, spinal fluid)
3. blood meal
4. multiplication in fly by binary fission
invades CNS, kills via encephalitis
Two strands of trypanosomes: where, why
T. brucei in Africa
T. cruzi in south america
evolved differently, from Pangea
T. cruzi: alternate name, distribution, life cycle
Chagas disease
From South America, migrated via travellers/blood donations
1. trypomastigote (i) transmission by assasin bug
2.replication into amastigote in muscle
3. replicates into trypomastigote, transmits back to assasin bug
muscle weakening until heart attack (disease carried until death)
Forms of Leishmaniasis
Visceral: liver, spleen, bone marrow (deadly without treatment) -> Leishmania Donovani
Cutaneous: face, arms, legs (not deadly, lesions remain, self healing) -> Leishmania Major
Leishmaniasis: distribution, life cycle, treatment
South america / Africa around equator (visceral also in Asia)
1. sandfly transmits promastigote, humans transmit amastigote
2. develops/ replicates in macrophage into amastigote
3. retransmission to sandfly
Treatment by ambisome
Can post kala-azar dermal leishmaniasis be a reservoir for transmission? (also what is it)
leftover of visceral leishmaniasis, unable to confirm (mostly due to a too small sample size.
