16 October 1998

Now, flukicide fear

RESISTANCE to the most effective flukicide is an increasing concern with the first reported case of failure of the drug in Britain.

In a letter in Vet Record (October 3, 1998) George Mitchell, Scottish Agricultural College vet science division, and others report the first case of failure of Fasinex (triclabendazole) in a flock in Argyllshire.

The case was found in a flock of 105 Blackface x Cheviot ewes and tups. Even after repeated dosing under vet supervision some animals remained infected.

Lynda Maris of Novartis Animal Health, the drug manufacturer, who was involved in the case, explains that the producer had been dosing four times a year for the last six years, perhaps giving rise to poor product efficacy. "Normal dosing patterns for producers are pre-tupping, pre-lambing and perhaps another one in midwinter," she says.

Roundworm resistance to some products is increasing, highlighting the problems of inaccurate and haphazard dosing.

However, this is the first case of resistance to flukicide, says David Barber, regional manager of SACs vet science division. "We dont know whether this is the beginning of a problem as its too early to tell. I would have expected more reported cases in Argyllshire were this to be the case."

Fasinex is the most effective treatment for all three stages of fluke and is therefore frequently used, says Mr Barber. "Lots of worm programmes are haphazard. Often, in fluke areas, a combined wormer and flukicide is used."

Producers might be able to reduce resistance concerns and save money by more judicious treatment, he says. "We advise producers to look at drug use with an advisor they trust, either the local vet or a specialist, and work out a health plan rather than treating animals when convenient."

Epidemiological studies will be conducted this winter by SAC and Novartis to see whether further cases emerge.