PARASITOLOGY 1`

Question 1

how are parasites different from bacteria and viruses?

Answer 1

parasites have a nucleus and more complicated cellular structure
parasites can be single celled or multicellular
parasites are also larger

Question 2

what are single celled parasites called?

Answer 2

protozoan

Question 3

what are multicellular parasites called?

Answer 3

helminths

Question 4

in which regions of the world are parasite infections most common?

Answer 4

in the developing world

Question 5

what are the most common helminth infections?

Answer 5

ascariasis
trichuriasis
hookworm

Question 6

where do soil transmitted helminths reside?

Answer 6

in the intestine

Question 7

what is the morphology of ascaris?

Answer 7

length:20cm
lifespan: 1 year
eggs per day:200,000

Question 8

what is the morphology of trichuris?

Answer 8

length:5cm
lifespan: 2 years
eggs per day: 5000

Question 9

what is the morphology of hookworm?

Answer 9

length:15mm
lifespan: 5 years
eggs per day: 10,000

Question 10

how are those worms transmitted?

Answer 10

the adult worms do not replicate inside the host
they produce eggs that are excreted with feces
ascaris and trichuris are transmitted by ingesting eggs and hookworm is transmitted through larvae by skin penetration

Question 11

what is the effect of those soil transmitted helminths? (STH)

Answer 11

major effect on children
malnutrition, growth stunting, cognitive and learning defects
sustains poverty

Question 12

what do helminths do to the immune system?

Answer 12

in order to survive so long in our body (we are the only hosts) they suppress the immune system to other infections like malaria tuberculosis and HIV

Question 13

what is the estimation of deaths per year by STHs?

Answer 13

estimated around 50,000deaths/year

Question 14

what is the life cycle of the ascaris?

Answer 14

1. adult male and female worms reproduce in the intestine
2. eggs are released into the environment by feces (has to be fertilised to go through development)
3. the egg turns into an embryo, which still has its protective coat
4. the embryo is ingested through contaminated food or water
5. the larvae makes a detour by the lungs before settling in the small intestine

Question 15

what is the lifecycle of the hookworm?

Answer 15

1. adults in small intestine reproduce
2. the egg released in the feces hatches to produce a larva
3. the larva enters through the skin in the foot/arm/exposed skin
4. the larva travels through the body and settles in the intestine

Question 16

how is an STH infection diagnosed?

Answer 16

intensity of infection is measured by the number of eggs per gram of feces
this is determined by microscopy
-> take a sample of stool, stain it etc

Question 17

how are STH infections treated?

Answer 17

treatment goal is to remove adult worms from the intestine, the already existing eggs cannot be get rid of
the most common drugs are benzimidazoles and ivermectin (got nobel prize) which paralyze the adult parasite but does not kill the egg
children (ages 5-12) are treated 2-3 times a year in school to reduce the worm burden on health and cognitive development
infected adults are not treated

Question 18

what transmits lymphatic filariasis and what is it caused by?

Answer 18

this disease is caused by wuchereria bancroft transmitted by mosquitoes
the larvae are transmitted through the bite
the disease is also known as elephantiasis

Question 19

what is the life cycle of wuchereria bancroft?

Answer 19

from mosquito to human:
1. larva enters through mosquito bite
2. enters the lymphatic system
3. adult worms block lymphatic flow, which accumulates in the leg and causes the large swelling

from human to mosquito:
1. adults in the lymphatic system produce microfilaria
2. the microfilaria go in the blood and are picked up by the mosquito (they will grow into larvae)

Question 20

what disease is caused by onchocerciasis and how?

Answer 20

river blindness
caused by the blackfly (present near rivers)
microfilaria accumulate in the eye and cause blindness

Question 21

what is a hypothesis as to what the elimination of helminth diseases in the developed world is causing?

Answer 21

there is a negative correlation between helminth infections and autoimmune diseases and allergic diseases
this might be due to the fact that the immune system becomes overexpressed when there are no infections to deal with and attacks the body
possible treatment for autoimmune diseases: get male worms (cannot lay eggs) to reduce the inflammation caused by autoimmune diseases
(cold climate also slows helminths down)