Parasitism in Extensively Farmed Livestock

Question 1

What are the important internal parasites in grazing animals?

Answer 1

Nematodes
Liver fluke
Lungworm
Coccidia

Question 2

What is the basic nematode LC?

Answer 2

Ingested larvae develop to adults in the GIT which produce eggs. Eggs excreted in the faeces. The PPP is 3 weeks. Larvae can survive freezing (but not dessication) and develop best when weather is warm & moist.

Question 3

What is the intermediate host of the liver fluke?

Answer 3

The mud snail. (Galba (Lymnaea) truncatula)

Question 4

Why might growing grass on infected pasture reduce parasite burdens?

Answer 4

Majority of the parasite population (95%) live in the bottom inch of the herbage.

Question 5

What is ‘targeted collective treatment’?

Answer 5

Treating the animals that are most effective/likely to spread. n.b. that 80% of eggs past are in 20% of the animals.

Question 6

In which months are infections of the following likely to be seen?

a) N. battus
b) Ostertagia
c) Haemonchus
d) Trichostrongylus
e) Fluke

Answer 6

a) April-June
b) May -November
c) July - November
d) September - December
e) Acute: September - December
Chronic: December - March

Question 7

What are the sub clinical signs of parasitis?

Answer 7

Reduced weight gain

Less than optimal productivity (LOP)

Question 8

What is the main way nematodes cause LOP?

Answer 8

• Reduced appetite
• Change in GIT S&F
• Immune/inflammatory responses (n.b. this will also have an energy cost)
• Malabsorption

Question 9

What is the pathogenesis of protein loss in PGE?

Answer 9

• Mucus and IgA secreate d and mucosal permeability increases.
• Local vasodilation
• Increased mucosal cell turnover.

Question 10

What test can be used to look for Haemonchus in a herd and how can this be used?

Answer 10

FAMACHA test assessed MM colour. Can be used to give targetted anthelmintic treatment.

Question 11

What is the main source of parasites in the spring?

Answer 11

Overwintered larvae on pasture. Not much from adult animals. This is due to the weather warming up.

Question 12

Why is acute fasciolosis such an issue in the autumn?

Answer 12

This is when there are millions of metececaria on the pasture. n.b. development of metecercaria resumes when weather is warm enough (around July) so they are shed around august.

Question 13

What are some principles of endoparasite control?

Answer 13

• Use Anthelmintics to break LC
• Safe pasture
  a) alternate spp.
  b) Grass length
  c) Hay/silage aftermath
• Minimise numbers of susceptible animals?

Question 14

Which animals are most susceptible to parasitism?

Answer 14

Young
Post parturient
Goats