Worm control and Anthelmintic resistance Flashcards Preview

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Flashcards in Worm control and Anthelmintic resistance Deck (27):
1

The main nematode species causing disease (PGE) in British sheep are ____

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

2

less important worms in sheep

Nematodirus spp
Oesophagostomum venulosum
Chabertia ovina
Bunostomum trigonocephalum
Strongyloides papillosus

3

main worm in cattle

Ostertagia ostertagi

4

other worms in cattle

Cooperia spp.
Trichostrongylus spp
Nematodirus helvetianus

5

lungworm in cattle

Dictyocaulus viviparus

6

most important horse worm

strongyles ("redworms")

7

2 groups of strongyles

non/migratory

8

migratory strongyles

large
Strongylus vulgaris; Strongylus edentatus;
Strongylus equinus

9

non-migratory strongyles

Triodontophorus, spp. (Large)
Cyathostomins (or trichonemes) - includes 4 genera and over 40 species (Small)
Poteriostomum, Oesophagodontus (Small)

10

treatment failures

under dosing - Underestimation of bodyweight
Inadequate maintenance of equipment
Poor treatment techniques
Failure to follow manufacturer’s instructions
Use of incorrect drug for target worms
Re-introduction of animals onto heavily contaminated pasture
ANTHELMINTIC RESISTANCE

11

anthelminitic resistance

the parasite can tolerate anthelmintic doses which are normally lethal
the ability to do so is heritable

12

how does resistance appear

resistance alleles pre-exist in most worm populations even before anthelmintics are ever used
when the anthelmintic is used worms with resistance alleles are favoured
resistance develops slowly at first, then more rapidly as allele freq increases

13

resistance in sheep nematodes

reported worldwide
BZ resistance widespread in UK
some "triple" resistant Teladorsagia circumcincta

14

resistance in horses

Benzimidazole resistance now widespread in cyathostomins
Resistance to pyrantel and macrocyclic lactones still uncommon
Large strongyles (Strongylus spp.) are now rarely found and so little or no resistance reported

15

clinical failure due to resistance

unlikely to be clinical failure of the anthelmintic until thev allele frequency approaches 50% and the frequency of resistant parasites is > 20%

16

drench test

A quick indicator of anthelmintic efficacy
FEC on 10 faecal samples post treatment
The time after treatment depends on the anthelmintic used

17

Faecal Egg Count Reduction Test

Estimation of efficacy by comparing FEC before and after treatment with untreated controls
Resistance indicated if treatment does not reduce FEC by >95%

18

SCOPS guidelines

1. Work out a control strategy with your vet or advisor
2. Use effective quarantine strategies
3. Test for AR on your farm
4. Administer anthelmintics effectively
5. Use anthelmintics only when necessary
6. Select the appropriate anthelmintic for the task
7. Adopt strategies to preserve susceptible worms
8. Reduce dependence on anthelmintics

19

1. Work out a control strategy with your vet or advisor

cost effective, reliable and sustainable plan

20

2. Use effective quarantine strategies

Treat with two products in different groups sequentially (not together)
Hold off pasture for 24-48 hours
Turn out on to dirty pasture

21

3. Test for AR on your farm

Test particularly where pour-on products are used
Use either post treatment Wormer Test (WT) or Faecal Egg Count reduction Test (FECRT)
Larval identification to determine species involved

22

4. Administer anthelmintics effectively

Weigh or dose for the heaviest in the group
Check the dosing/pour-on gun
Use correct techniques especially with pour-on products

23

5. Use anthelmintics only when necessary

Dosing of adult cows is not normally required
Indoor calves are usually worm-free at turnout
Provide low risk pasture at the start of grazing season
use strategic preventative treatments if pasture infectivity is high risk
Move mid season to low risk pastures
Monitor by FEC to optimise timing of treatments

24

6. Select the appropriate anthelmintic for the task

Use narrow spectrum products where possible
Avoid ‘off-target’ use such as combination products
Rotate products where appropriate

25

7. Adopt strategies to preserve susceptible worms

Reduce selection pressure and preserve wormer susceptibility
Leave some calves undosed
Dose on contaminated pasture and delay the move to clean pasture

26

8. Reduce dependence on anthelmintics

Use grazing management to reduce the parasite challenge
Alternation of cattle and sheep grazing
Use of new leys and aftermaths

27

resistance in cattle nematodes

resistance much less common than with sheep nematodes
most ML-resistance in cooperia spp.
few reports in UK