Farm Ireland

Sunday 17 February 2019

'On many farms, wormers are failing to control worms effectively'

FarmIreland Team

FarmIreland Team

Over the past two years, researchers in Teagasc Grange have being testing the effectiveness of various wormers on the market.

In their latest report on their work, researchers Anne Kelleher, Barbara Good and Orla Keane of AGRIC, Teagasc Grange, Co. Meath said a variety of different worm species can infect cattle, but the main species of economic importance are Ostertagia ostertagi, which infects the abomasum, and Cooperia oncophora, which infects the small intestine.

Infection with gut worms reduces feed intake and can cause parasitic gastroenteritis.

"Grazing cattle are continuously exposed to gut worms.

"Calves are most at risk as animals build up immunity over time," they said.

Current methods of gut worm control rely almost exclusively on the administration of broadspectrum anthelmintic products.

There are a wide variety of products on the market for gut worm control but ultimately all belong to one of three classes, each with a unique mode of action:

(i) benzimidazole, commonly known as white wormers;

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(ii) levamisole, commonly known as yellow wormers; or,

(iii) macrocyclic lactones, commonly known as clear wormers (this class includes both ivermectin and moxidectin).

Anthelmintic products have effectively controlled gut worm infections for over 50 years; however, recently anthelmintic resistance has been reported.

Anthelmintic resistance is the ability of a worm to survive a dose that would normally kill it.

It is a heritable trait so resistant worms pass the genes for resistance on to their offspring.

Over the past two years, the researchers have tested the efficacy of benzimidazole (17 farms), levamisole (12 farms), ivermectin (17 farms) and moxidectin (12 farms) on dairy calf to beef farms.

Anthelmintic resistance was found on a number of the farms demonstrating that on many farms, wormers are failing to control worms effectively.

Percentage of farms with resistance:

Benzimidazole: 71%

Levamisole: 25%

Ivermectin: 100%

Moxidectin: 75%

The researchers highlighted that in order to know what products are effective on their farm, beef producers should test the efficacy of their anthelmintic treatments.

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