Principles of control of Ostertagia in cattle

Question 1

What are three uses of anthelmintics as part of a control program?

Answer 1

• Treatment of individual animals with the disease
• Metaphylaxis: timely mass medication of a group of animals to prevent or minimise an expected outbreak of disease
• Prophylaxis: prevention of disease

Question 2

What are the primary and secondary species of nematodes that need to be controlled in cattle?

Answer 2

Primary = Ostertagia ostertagi
Secondary = Trichostrongylus spp and Cooperia spp

Question 3

Why is management important as part of a control program?

Answer 3

Do not want to get to a point where drugs are no longer working so also need good, effective management

Question 4

Compare a clean vs a safe pasture

Answer 4

Clean = not grazed by any cattle in the last 12 months, all overwintered larvae have died out
Safe = Used the pervious year but safe by the beginning of June. Should have very low levels of L3

Question 5

What are the 3 drug classes licenced for cattle?

Answer 5

• Benzimidazoles
• Imidathiazoles
• Macrocytic lactones

Question 6

What is the colour of the drench for the following:

• Benzimidazoles
• Imidathiazoles
• Macrocytic lactones

Answer 6

• White
• Yellow
• Clear

Question 7

What is meant by a drugs residual activity?

Answer 7

The amount of activity a drug displays after its been given

Question 8

Which of the 3 drug category’s have no residual activity?

Answer 8

Benzimidazoles

Imidithiazoles

Question 9

If ivermectin is picked for treatment, what doing frequency do you need to give and why?

Answer 9

• Every 5 weeks

- ivermectin kills all stages of Ostertagia in the animal and has a 2 week residual activity

Question 10

If animals were turned out on the 1st May, when would you give 3 treatments of Ivermectin?

Answer 10

Dose 3, 8 and 13 weeks after turnout (21st May, 26th June, 31st July)
- 3 weeks after turnout before they can produce eggs and shed them onto pasture

Question 11

What is being prevented when treating animals with 3 doses of ivermectin?

Answer 11

Eggs going out onto pasture to be a new source of infection

Question 12

Which nematode has built up resistance to MLs?

Answer 12

Cooperia spp

Question 13

What can be used to treat cows as a pour on?

Answer 13

Eprinomectin

Question 14

What are the main benefits of pour on eprinomectin?

Answer 14

• no withdrawal period because it doesn’t get into the milk

- easy to administer

Question 15

Why is it unlikely that eprinomectin would be used for treatment?

Answer 15

• Not common to treat dairy cows as they have resistance

- Giving sub-efficacious levels can also increase the parasites resistance to the drug

Question 16

Do you need to treat a beef suckler herd with spring calving?

Answer 16

Might not need to do anything at all – spring born calves, mothers are immune, calves are still sucking and by the time they start grazing they’ll have missed the period of risk

Question 17

Why is a small amount of infection in calves okay?

Answer 17

Help them build resistance