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Anthelmintic resistance

Anthelmintic resistance: a population of worms which survive a correctly applied anthelmintic treatment


Roundworms are resistant to anthelmintics ———- sheep carry these resistant roundworms


Key points to remember:

  • It is the worms that are resistant to the anthelmintic, NOT the sheep
  • Resistance develops to the group, not the individual product

Resistant worms produce resistant offspring

  • Leaving some sheep untreated can dilute worms which survived treatment as untreated sheep will be putting out susceptible worms too