Helminths and Arthropods (Lec. 13)

Question 1

Define parasitology

Answer 1

The branch of science concerned with the study of parasitic organisms

Question 2

Define protozoa

Answer 2

A phylum of the kingdom Protista

Question 3

Define helminth

Answer 3

A parasitic worm: the adult form is often visible to the naked eye but the eggs are microscopic and are the infectious/diagnostic form

Question 4

Define dioecious

Answer 4

Having the male and female reproductive organs in separate individuals

Question 5

Define monoecious

Answer 5

Having both the male and female reproductive organs in the same individual

Question 6

Define arthropod

Answer 6

An invertebrate animal of the phylum Arthropoda (insects, arachnids, and crustaceans). Have segmented bodies, hard external skeletons, and jointed legs.

Question 7

Define scolex

Answer 7

The head of the worm

Question 8

Define proglottid

Answer 8

An individual hermaphroditic reproductive segment which, when they mature, fall off the tail of the cestode and dissolve, and the eggs inside are released.

Question 9

Define strobila

Answer 9

The entire body of a cestode

Question 10

Define ectoparasite

Answer 10

A parasite that lives on the outside of its host (e.g. fleas)

Question 11

List the distinguishing characteristics of helminths

Answer 11

Large multicellular organisms usually visible to the naked eye in the adult stage. Can have elongated, flat, or round bodies.

Question 12

List the distinguishing characteristics of nematodes.

Answer 12

Nematodes aka roundworms are round and non-segmented. Have complete digestive systems and are dioecious.

Question 13

List the distinguishing characteristics of cestodes

Answer 13

Cestodes are tapeworms, which are a type of flat worms, and are flat and segmented. They’re monoecious and typically found in the digestive system.

Question 14

List the distinguishing characteristics of trematodes

Answer 14

Trematodes are flukes, and are flat and non-segmented. They absorb food through a cuticle.

Question 15

Describe a parasitic infection in which humans serve as a definitive host

Answer 15

A cestode called Taenia solium (pork tapeworm); the infective stage is the eggs, and the larvae hatch in the intestine and bore into the intestinal wall. They can produce tissue cysts called cysticerci.

Question 16

Describe a parasitic infection in which humans serve as an intermediate host

Answer 16

Toxoplasmosis: humans are infected after consuming cysts or oocysts from contaminated food or water. Cats are the definitive host.

Question 17

Describe a parasitic infection in which humans serve as both a definitive and an intermediate host

Answer 17

Dirofilaria immitis: larvae can travel by mosquito and into a human, where the human becomes the definitive host, or another mosquito can bite that human and pick up the larvae, which can then mean the human is the intermediate host.

Question 18

Which group of medically relevant helminths is the genera Paragonimus in?

Answer 18

Trematodes (aka flukes)

Question 19

Which group of medically relevant helminths is the genera Taenia in?

Answer 19

Cestodes (aka tapeworms)

Question 20

Which group of medically relevant helminths is the genera Enterobius in?

Answer 20

Nematodes (roundworms)

Question 21

Which group of medically relevant helminths is the genera Dirofilaria in?

Answer 21

Nematodes (roundworms)

Question 22

List the methods commonly used to identify helminths in the lab

Answer 22

Cannot be cultured.
Gross examination of macroscopic morphology for adults, microscopic morphology for larvae and ova. Typical patient samples are stool, blood, sputum, or tissue biopsies.

Question 23

Define and identify arthropod vectors

Answer 23

Arthropods that carry pathogenic microorganisms. Arachnida (spiders, mites, ticks), Insecta (bees, flies, mosquitoes, lice), and Crustacea (crabs, crayfish).