Life cycle and reproduction of Helminths

Question 1

Name the 3 stages of the Helminth life cycle

Answer 1

egg, larval, and adult stages.
Adults derive nutrients and reproduce sexually in a host’s body

Question 2

Explain how each stage transitions into the next stage

Answer 2

Stage 1- eggs are eaten unknowingly in the farm by the intermediate hosts known as the farm animals (cows &pigs)

Stage 2- Cows and pigs are slaughtered to be consumed by humans. Humans eat the meat that had the eggs of the worm. If meat is cooked at the right temp, larvae dies, if not, larvae lives.
Eggs hatch in the intestine

stage 3- Eggs hatch in the intestine.

Stage 4- Larvae mature into adults within 1 month.

Stage 5- Male and female worms mate.

Stage 6-Female migrate to the anus to deposit eggs. Intense itching ensues.

Eggs are brought back into the environment through the feces

Question 3

Explain what is an intermediate host and a definitive host with examples

Answer 3

Those animals which feed on the eggs of the worms and the eggs develop

The definitive host is when the larvae develops into an adult in the inestins of humans. Humans are the definitive hosts

Question 4

What are the 2 routes of helminth infection in humans?

Answer 4

-oral intake
- penetration of unbroken skin

Question 5

Nematodes, trematodes, cestodes

Answer 5

Nematodes: sexes are separate and different in appearance
Trematodes: sexes can be separate or hermaphroditic
Cestodes: generally hermaphroditic

Question 6

All worms are multicellular, what is the only exception to this?

Answer 6

The eggs. These are unicellular

Question 7

1 route for human infection are

Answer 7

contaminated food, soil, and water or infected animals.

Question 8

second Routes of infection by these worms are by

Answer 8

oral intake or penetration of unbroken skin.

Question 9

Fertilized eggs of helminths are

Answer 9

• Released to the environment
  -Provided with a protective shell and extra food to aid their development into larvae
• Vulnerable to heat, cold, drying, and predators

Question 10

Certain helminths can lay from 200,000 to 25 million eggs a day to assure successful completion of their life cycle.

Answer 10

200,000 to 25 million eggs a day

Question 11

How many species of worms are parisitic?

Answer 11

50

Question 12

Although worms are distributed throughout the world, where do they like to live?

Answer 12

in tropical areas

(Yearly estimate of cases is in the billions and are not confined to developing countries.
Conservative estimate of 50 million helminth infections in North America alone)