Nematode General Information

Question 1

What are the general characteristics of nematodes?

Answer 1

• One of the most abundant animals on earth.
• Most are free-living.
  
  • non-pathogenic
  • mostly in soil and mud.
• Some are pathogenic.

Question 2

Some nematodes are pathogenic…?

Answer 2

1. In all types of animals.
2. Even for some plants.
3. Every animal has at least one known pathogenic nematode.
4. Oldest known pathogen (egyptian scrolls).

Question 3

General anatomy of nematodes:

They are called?

Answer 3

Roundworms.

-bodies look round in diameter (actually oval).

Question 4

General anatomy of nematodes:

Bodies are?

Answer 4

Long and thin.

• 1 mm or less, to 1 m in length.
• Most are small, hard to see.

Question 5

General anatomy of nematodes:

Digestive system?

Answer 5

1. Mouth opening with lips.
2. Buccal cavity.
   
   • between mouth and esophagus.
3. Esophagus
   
   • muscular, muscle pumps to suck food in.
4. Long intestine
5. Anus

Question 6

General anatomy of nematodes:

What do they eat?

Answer 6

Blood, tissue fluid, tissue cells, intestinal contents of host.
-The intestines of nematodes are very long and inefficient so they need to eat HUGE amounts of food.

Question 7

Nematode Reproduction

Male

Answer 7

Testes produce sperm.

Question 8

Nematode Reproduction

Female

Answer 8

Ovaries, oviducts, uterus, eggs.

Question 9

Nematode Reproduction

Most nematodes are (relating to m/f)?

Answer 9

Dioecious: male and female in different bodies.

Question 10

Nematode Reproduction

Most have sexual?

Answer 10

Dimorphism (male and female look different)

• Females are usually larger than male.
• Sometimes males have coiled tails.
• Some males have copulatory bursa.

Question 11

Nematode Reproduction

Some of them are (relating to m/f)?

Answer 11

Monoecious (male and female in the same body).

Question 12

Nematode Reproduction
Most are (relating to eggs)?

Answer 12

Oviparous

-eggs hatch outside the body.

Question 13

Nematode Reproduction

A few are (relating to eggs)?

Answer 13

Oviviparous

-eggs hatch inside the body.

Question 14

General Life Cycle of Nematodes (dioecious)

What are the 7 steps of the life cycle?

Answer 14

1. Male and female mate.
2. Forms a zygote
3. Egg can hatch outside or inside of new host’s body.
4. Development of the juvenile takes place either inside or outside the egg.
5. Juveniles develop through several stages.
6. Third or forth stage juvenile develops into an adult.
7. Some have developmental arrest.

Question 15

General Life Cycle of Nematodes (dioecious)

What happens after the zygote is formed?

Answer 15

• It may or may not divide to form a morula.
• Either are found in a shelled egg.
• Egg is often the form that is excreted into the environment.

Question 16

General Life Cycle of Nematodes (dioecious)

Stages of Development

Answer 16

1. Often called larval stages.
2. Called either J or L 1, 2, 3, 4
   
   • J5 or L5 is adult
3. Between each stage juvenile molts (getting larger).
   
   • ecdysis (molts) - casts off outer cuticle.

Question 17

General Life Cycle of Nematodes (dioecious)

Developmental Arrest

Answer 17

Hypobiosis: juvenile stops developing at some stage in development.

• this enables the juvenile to survive adverse conditions while waiting to invade a new host, or inside the host (can survive for a whole year).
• Usually occurs in the J3/J4 stage.

Question 18

General Life Cycle of Nematodes (dioecious)

Which stage is the infectious stage?

Answer 18

Usually a J3.

*occasionally a J2, or J4.

Question 19

General Life Cycle of Nematodes (dioecious)

What stages are parasitic?

Answer 19

J3, J4, J5

Question 20

General Life Cycle of Nematodes (dioecious)

What stages are pre-parasitic (outside of host)?

Answer 20

J1, J2, some J3

Question 21

General Life Cycle of Nematodes (dioecious)

What is the diagnostic stage?

Answer 21

The life stage that comes out of the paratenic host (usually in the feces).
*Almost never the adult, usually the egg.

Question 22

Life Cycle Variations

What are the 2 types of life cycles in nematodes?

Answer 22

1. Direct

2. Indirect

Question 23

Life Cycle Variations

Direct Life Cycle

Answer 23

1. No intermediate host.
2. All pre-parasitic phases are found in the environment.
3. Juvenile development may take place inside or outside of the egg.
4. Eggs do not hatch in the environment.
5. Eggs do hatch in the environment.

Question 24

Life Cycle Variations

What happens in the direct life cycle when eggs DO NOT hatch in the environment?

Answer 24

1. Juveniles develop inside the egg.
2. Infective stage is inside the egg when it is ingested.
3. Hatches in new hosts intestine.

Example: Ascaris suum

Question 25

Life Cycle Variations

What happens in the direct life cycle when eggs DO hatch in the environment?

Answer 25

1. J1 hatches from the egg in the environment.
2. Develops into J2 then J3 in environment.
3. J3 is infective stage

Example: Trichostongylus spp.

Question 26

Life Cycle Variations

Indirect Life Cycle

Answer 26

1. Juveniles develop into infective stage inside an intermediate host.
2. Transmitted to the definitive host when:
   a. it ingests the intermediate host.
   b. it is bitten by an arthropod.

Question 27

Life Cycle Variations

What happens when the definitive host ingests the intermediate host?

Answer 27

1. Infective stage enters the host digestive system.
2. May migrate to other parts of the host body.

Example: Parelaphostrongylus tenuis

Question 28

Life Cycle Variations

What happens when the intermediate host is a biting or sucking arthropod?

Answer 28

Infective stage enters definitive host’s bloodstream.

Example: Dirofilaris immitis (heartworm)