Anthelmintic resistance Flashcards Preview

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Flashcards in Anthelmintic resistance Deck (19):
1

What are the main species that cause ostertagiosis in sheep in the UK?

Teladorsagia circumcincta
Trichstrongylus spp.
Nematodirus battus
Haemonchus contortus
Cooperia spp.

2

What are the main species that cause ostertagiosis in cattle in the UK?

Ostertagia ostertagi

3

What are the most important horse worms?

'Redworms' Strongyles

4

How are strongyles divided?

Size (small vs. large)
Life cycle (migratory vs. non-migratory)

5

What are the main reasons for anthelmintic treatment failures?

Normally through user error. e.g.
UNDER DOSING
-Underestimation of BWT
-Equipment maintainance
-Poor dosing technique
-Failure to follow manufacturer instructions
INCORRECT DRUG USAGE
RE-INTRO ONTO CONTAMINATED PASTURE
ANTHELMINTIC RESISTANCE

6

Is anthelmintic resistance conferred by environmental factors?

No it is heritable

7

What is the state of anthelmintic resistance for sheep and cattle parasites in the UK?

Sheep - widespread resistance to BZs. Reports of 'triple' resistant Teladorsagia circumcincta.

Cattle - much less. treatment failures more likely due to under dosing.

8

What is meant by triple resistance?

Parasite resistant to the 3 main anthelmintics.

9

What is the state of resistance to anthelmintics in horse parasites?

BZ resistance widespread in cyathostomins
Pyrantal and ML resistance uncommon
Large strongyles are uncommon so resistance not really reported.

10

When is clinical failure of the anthelmintic likely, with regard to allele frequency, and how does this relate to when resistance is detectable?

Clinical failure is only really detectable when a population has 20% resistance and allele frequency is >50%.

Testing can detect resistance when allele freq. is >25% and >5% of the population is resistant.

11

What are the types of in vivo tests used to test for resistance?

The drench test and the faecal egg count reduction test.

12

How long after treatment should faecal samples be taken for the drench test?

LV - 7 days
BZ & ML - 14 days

13

When is resistance indicated by a FECRT?

When the egg count is not reduced by >95%

14

What are the key SCOPs guidelines ?

Work out a control strategy with vet/advisor
Quarantine effectively
Test for AR on the farm
Effectively administer anthelmintics
Use only when necessary
Select appropriate anthelmintic
Preserve susceptible worms
Reduce dependence on AH.

15

When should AR be tested for in particular?

Where pour-on products are used.

16

How can wormers be delivered effectively?

Dose to heaviest animal in group
Use correct technique.

17

How can indoor calves be prevented from becoming infected?

Provide low risk pasture at beginning of grazing season.
Use strategic prophylaxis is infectivity high risk
Move mid-season to low-risk pastures.

18

How can selection pressures for AR be reduced?

By using narrow spec when possible
Avoid combination products
Rotate products where necessary

19

How can a 'refugia' population of susceptible worms be preserved?

Leave some calves undosed
Dose on contaminated pasture and delay move to infected pasture to allow low level infection of susceptible pasture to develop.