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Flashcards in Nematode General Information Deck (28):
1

What are the general characteristics of nematodes?

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

2

Some nematodes are pathogenic...?

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).

3

General anatomy of nematodes:
They are called?

Roundworms.
-bodies look round in diameter (actually oval).

4

General anatomy of nematodes:
Bodies are?

Long and thin.
-1 mm or less, to 1 m in length.
-Most are small, hard to see.

5

General anatomy of nematodes:
Digestive system?

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

6

General anatomy of nematodes:
What do they eat?

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.

7

Nematode Reproduction
Male

Testes produce sperm.

8

Nematode Reproduction
Female

Ovaries, oviducts, uterus, eggs.

9

Nematode Reproduction
Most nematodes are (relating to m/f)?

Dioecious: male and female in different bodies.

10

Nematode Reproduction
Most have sexual?

Dimorphism (male and female look different)
-Females are usually larger than male.
-Sometimes males have coiled tails.
-Some males have copulatory bursa.

11

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

Monoecious (male and female in the same body).

12

Nematode Reproduction
Most are (relating to eggs)?

Oviparous
-eggs hatch outside the body.

13

Nematode Reproduction
A few are (relating to eggs)?

Oviviparous
-eggs hatch inside the body.

14

General Life Cycle of Nematodes (dioecious)
What are the 7 steps of the life cycle?

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.

15

General Life Cycle of Nematodes (dioecious)
What happens after the zygote is formed?

-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.

16

General Life Cycle of Nematodes (dioecious)
Stages of Development

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.

17

General Life Cycle of Nematodes (dioecious)
Developmental Arrest

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.

18

General Life Cycle of Nematodes (dioecious)
Which stage is the infectious stage?

Usually a J3.
*occasionally a J2, or J4.

19

General Life Cycle of Nematodes (dioecious)
What stages are parasitic?

J3, J4, J5

20

General Life Cycle of Nematodes (dioecious)
What stages are pre-parasitic (outside of host)?

J1, J2, some J3

21

General Life Cycle of Nematodes (dioecious)
What is the diagnostic stage?

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

22

Life Cycle Variations
What are the 2 types of life cycles in nematodes?

1. Direct
2. Indirect

23

Life Cycle Variations
Direct Life Cycle

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.

24

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

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

25

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

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.

26

Life Cycle Variations
Indirect Life Cycle

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.

27

Life Cycle Variations
What happens when the definitive host ingests the intermediate host?

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

Example: Parelaphostrongylus tenuis

28

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

Infective stage enters definitive host's bloodstream.

Example: Dirofilaris immitis (heartworm)