The Geohelminths

Question 1

types of geohelminths

Answer 1

• ascaris lumbricoides: large roundworm
• necator americanus: hookworm
• ancylostoma duodenale: hookworm
• trichuris trichiura: whipworm
• stronglyoides stercoralis

Question 2

what type of cell is c. elegans?

Answer 2

metazoan, multicellular parasite

Question 3

developmental stages of phylum nematoda

Answer 3

egg -> L1 -> L2 -> L3 -> L4 -> adult

four moults; L = larvae

Question 4

where is more prevalent ascaris lumbricoides?

Answer 4

in tropical and subtropical regions and areas with inadequate sanitation

Question 5

how long can ascaris egg can survive in soil?

Answer 5

for 7 years

Question 6

why can the egg survive so long in soil?

Answer 6

it has a hard coat - they are highly robust

they stop development at L3 and wait to infect a new person

Question 7

what does ascaris lumbricoides infect?

Answer 7

the human intestine

Question 8

how many eggs does a female may produce?

Answer 8

200,000 eggs per day

Question 9

cycle of infection of ascaris

Answer 9

1. eggs swallowed
2. larvae hatch
3. invade the intestinal mucosa
4. carried via the portal
5. goes to systemic circulation to the lungs

Question 10

action of the ascaris in lungs

Answer 10

1. they mature further in the lungs (10 to 14 days)
2. penetrate the alveolar walls
3. ascend the bronchial tree to the throat
4. larvae are swallowed

Question 11

how long do worms live?

Answer 11

1 to 2 years

Question 12

what activates the eggs?

Answer 12

digestive enzymes

Question 13

which two places if infected by the worms can cause death?

Answer 13

• in gut - they rupture the gut walls
• bile duct/ pancreatic duct - blocks them and kills the host
• lungs

Question 14

classes of people more likely to die from ascaris?

Answer 14

people with high IgE and eosinophils

Question 15

why is there a higher incidence of infections in areas where there are periodic rains?

Answer 15

because the rain liberates the worms from the soil, hence increase the infections

Question 16

what type of disease is Löffler’s syndrome?

Answer 16

a type I immune hypersensitivity - similar to an allergic reaction

Question 17

what type of antibodyis associated with Löffler’s syndrome?

Answer 17

IgE, also associated with natural immunity and protection system against macroparasites

Question 18

human species of hookworms

Answer 18

nectar americanus

ancylostoma duodenale

Question 19

hookworm cycle

Answer 19

1. eggs in faeces (diagnostic stage)
2. rhabditiform larva hatches
3. filariform larva
4. filariform larva penetrates skin (infective stage)
5. adults in small intestine

Question 20

development of hookworm infection

Answer 20

1. eggs hatch in 1 to 2 days ( L1) - they are ready to hatch as soon as they are laid
2. after 5 to 10 days they become infective - L3
3. infective larvae can survive 3 to 4 weeks
4. penetrate the skin -> heart -> lungs -> pharynx -> intestine
5. most adult worms eliminated in 1 to 2 years, but can survive for several years

Question 21

where does the hookworms breed?

Answer 21

in the stomach

Question 22

why do the infected person may die from bleeding?

Answer 22

because the worm moves from side to side and everywhere they go, they bite. hosts then loses blood every time the worm bites them.

Question 23

how do pigs and humans get infected by trichinella spiralis?

Answer 23

pigs - ingestion of meat scraps or animals

humans - ingestion of undercooked meat (esp. pork)

Question 24

where does the trichinella spiralis live inside the body?

Answer 24

in the gut, but the superficial layer - doesn’t go to tissues

Question 25

cycle of trichinella spiralis

Answer 25

1. ingestion of undercooked meat
2. larva released in the small intestine
3. adults in small intestine
4. larva deposited in mucosa
5. encysted larva in started muscle - larva in a capsule and can’t get rid of it

Question 26

how does trichinella spiralis kill the cells?

Answer 26

it enters the cell, then the nucleus degrades and the cell finally disappears