Virulence and pathogenicity of parasites

Question 1

Three groups of eukaryotic organisms that afflict the health and well being of animals

Answer 1

Protozoa (single cell, nucleated)
Helminths (worm like animals showing differentiation. These include nematode, or roundworms, cestode, or tapeworms/flatworms, and trematode, or flukes.
Arthopods (arachnids and insects; ectoparasites)

Question 2

What is an ectoparasite?

Answer 2

Parasite that lives ON the host and causes infestation

Question 3

What is an endoparasite?

Answer 3

Parasite that lives IN the host and causes infection

Question 4

What is a definitive host?

Answer 4

A host that harbors adult/sexual stage of a parasite

Question 5

What is a intermediate host?

Answer 5

A host that harbors larval/asexual stage of a parasite

Question 6

What is a paratenic host?

Answer 6

Also known as a transfer host, harbors the parasite but the parasite does not undergo any further development inside

Question 7

What is a reservoir?

Answer 7

An animal (definite) host that serves to maintain the parasite’s life cycle in an environment

Question 8

What is an incidental host?

Answer 8

An unusual host that is unnecessary for the maintenance of the parasite in nature.

Question 9

What is host specificity?

Answer 9

Parasites that have a specificity for particular definitive and intermediate hosts as its life cycle can often only be completed in a specific host

Disease manifestation may be different depending on what kind of host is harboring a parasite.

Question 10

What are the common routes of parasite entry?

Answer 10

Ingestion
Skin/mucosal penetration
Transplacental (prenatal)
Arthropod bites
Sexual contact

Question 11

What is the infective dose of protozoa?

Answer 11

Just a few would be needed as they can reproduce in the host.

Question 12

What is the infective dose of helminths?

Answer 12

The severity depends on the initial worm load introduced in the host as the adult worms do not multiply in the definitive host.

Question 13

What are the different types of mechanical attachments by a parasite?

Answer 13

• Oral cavity (capsule)
• Attachment organs
• Suction disk
• Biting mouthparts
• Direct penetration

Question 14

What are the different types of molecular attachments by a parasite?

Answer 14

• Fibronectin and receptors (targeting fibroblasts)
• Major surface protease (MSP63) and CR 2 (targeting macrophages)
• C3b receptor (targeting red blood cell)
• Lectin and manose-6-phosphate adherence molecule 1 on disk (targeting duodenal and jejunal epithelium)

Question 15

What are some examples of mechanical tissue damage?

Answer 15

• Blockage of internal organs
• Pressure atrophy
• Migration through tissues

Question 16

What are the different types of toxic parasite products?

Answer 16

• Destructive enzymes
• Amoebic pore
• Endotoxins
• Catabolites
• Toxic secretions

Question 17

How do parasites cause lost of nutrients?

Answer 17

• Competes with the host for nutrients (in the case of Diphyllobothrium latum)
• Interferes with nutrient absorption (in the case of Giardia duodenalis &Strongylodies stercoralis)
• Nutrient loss (in the case of hookworms

Question 18

What is natural or innate immunity?

Answer 18

• A defense mechanism that does not depend upon prior?
exposure to the invader.
•Involves cytokines and their receptors, antimicrobial molecules and pattern recognition receptors, and phagocytosis

Question 19

What is acquired immunity?

Answer 19

Conferred by a host’s specific immunity response developed as a result of a previous parasitic infection.

Question 20

What is premunition?

Answer 20

Resistance to reinfection dependent on retention of the infectious agent

Question 21

What is concomitant immunity?

Answer 21

The survival of some cells or organisms with the immune
destruction of other cells or organisms of the
same line