Trichostrongyle nematodes in ruminants and Teladorsagia

Question 1

Trichostrongyle nematodes have a similar lifecycle and eggs in ruminants. What is a defining feature of trichostrongyle nematodes?

Answer 1

Undergo hypobiosis

Paused stage in development during harsh conditions e.g. cold weather

Question 2

Which species are exceptions to the similar lifecycles most trichostrongyle nematodes have?

Answer 2

Nematodirus battus

Haemonchus contortus

Question 3

Is a typical trichostrongyle life cycle direct or indirect?
Do they have an intermediate host?
Do they have a free living stage on pasture?

Answer 3

Direct lifecycle
Intermediate host
Free living stage

Question 4

Define prepatent period

Answer 4

Time taken from infection (ingesting L3) to detecting infection (detecting eggs in faeces)

Question 5

Define patent infection

Answer 5

Infection that can be detected e.g. by eggs in faeces

Question 6

Describe the typical Trichostrongyle lifecycle from egg laying to adult growth

Answer 6

Female mates with male in abomasum and lays eggs
Eggs excreted out of body in faeces and develop into L1
L1 feeds on bacteria in faeces to develop into L2 and L3
L3 released from faeces by rain splash
L3 free living on soil to be ingested
L3 burrow into gastric glands of abomasum to develop into L4 and L5
L5 emerge from gastric mucosa, mature in abomasa lumen and repeat

Question 7

How many Trichostrongyle developing larvae are needed to be associated with disease?

Answer 7

Around 40,000

L4-L5

Question 8

How do Trichostrongyle larvae cause damage to sheep? What does this result in?

Answer 8

L3 burrowing and L5 emerging from gastric glands
Epithelial cells replace parietal cells - less acid, increased pH, less pepsinogen to pepsin, increased mucosa permeability

Question 9

What are the subclinical signs of a Trichostrongyle infection?

Answer 9

Poor weight gain

Question 10

What are the clinical signs of a Trichostrongyle infection?

Answer 10

Weight loss
Diarrhoea
Inappetance
Dehydration 
Death

Question 11

What stage larvae hypobiose and what stimulates them to do so?

Answer 11

L3 - detect drop in temperature over Winter

Cause hypobiosis once ingested

Question 12

Which species of the Trichostrongyle family is the biggest cause of PGE in sheep?

Answer 12

Teladorsagia circumcincta

Question 13

Where is telodorsagia circumcincta found in the GI of sheep?

Answer 13

Abomasum only

Question 14

How long is teladorsagia circumcincta in length?

Answer 14

1cm

Question 15

Describe the morphology of teladorsagia

Answer 15

1cm 
Brown/pink
Slender
Tiny cervical papillae
Males have bursa and spicules