Lecture 8 Flashcards
1
Q
Another name for roundworms?
A
Nematodes
2
Q
How many nematode species?
A
Estimated 1 million
3
Q
Nematode apperance?
A
- Cylindrical worms with thick cuticle
- Separate sexes
4
Q
Repeated moults during development of Nematodes
A
- Larval Stage 1 (L1)
- Larval Stage 2 (L2)
- Larval Stage 3 (L3)
- Larval Stage 4 (L4)
- Adult
5
Q
Gastrointestinal Nematodes (GIN) of sheep, goats and cattle?
A
- Direct life cycle
- Larvae present on the grass cause infection
6
Q
What is the infection with GIN called?
A
Parasitic Gastroenteritis (PGE)
7
Q
Parasitic Gastroenteritis (PGE) results?
A
- Reduced feed intake
- Inefficient digestion of ingested protein
- Loss of protein due to damage to the epithelial barrier
- Diversion of available proteins to immune/inflammatory responses
8
Q
PGE symptoms
A
- Diarrhoea
- Loss of appetite
- Dehydration
- Anaemia
- Bottle jaw
- Weight loss
9
Q
Bovine PGE
A
- Ostertagia ostertagi and Cooperia spp.
- Calves, first grazing season most affected
- Older cattle may serve as a source of infection
- Disease mostly due to the presence of worms in the abomasum
10
Q
Ovine PGE
A
- Many species
- Lambs generally more affected than adult sheep
- Peri-paturient rise in egg output
- Disease due to worms in the abomasum and the small intestine
11
Q
Seasonality of PGE
A
- Eggs and larvae affected by environmental conditions
-> No development under 10 degrees, die off under 0 degrees
-> Mild winters = high survival on pasture = reservoir of infection
-Develop in Spring (warm and wet conditions)
-Gradual build-up of eggs/larvae on pasture during the grazing season (extent depending on stocking density)
- Hypobiosis in some spp:
-> Larvae on pasture that have been exposed to falling temperatures; more likely to undergo arrested development
-> Emergence of large numbers of larvae from glands/mucosa into limen in late winter/early spring can cause severe disease
-Build up of infective larvae on pasture during the summer
- Greatest disease risk mid-summer to autumn
12
Q
When is PGE mostly observed?
A
- Spring born calves and lambs in their first grazing season (6-8 months old): Due to their exposure to large numbers of L3 on pasture
- Calves and lambs in late winter/early spring following first grazing season (yearlings): Due to mass emergence of hypobiotic larvae
13
Q
What animals are less likely to get PGE?
A
- Older animals: Protected against clinical disease
- They can contribute to pasture contamination particularly ewes around parturition
14
Q
Host Immunity against GIN
A
- Regular exposure to GIN results in the development of immunity
- Immunity to Teladorsagia circumcinta can take 10-12 months to develop while it develops more rapidly to Nematodirus battus
- Immune/ Resistant hosts can:
-Prevent worm migration and
establishment- Halt development at a less
harmful stage - Reduce the size and fecundity of
the worms
- Halt development at a less
- Adults that have developed immunity can ingest large amounts of larvae without developing clinical signs
- However, pregnant ewes can produce large numbers!
15
Q
Nematodirus Battus
A
- Larvae develop to L3 stage inside the eggs
- Eggs are resistant to freezing
- Freezing temperatures followed by rise in temperatures (>10 degrees) stimulates synchronous hatching
- Mass hatching in Spring!
