Resistance to antiparasitic drugs, such as those used to combat sheep scab and liver fluke, was described as a major problem by a veterinary sheep scientist at a recent Farmers’ Union of Wales animal health and welfare committee meeting.
During discussions, former president of the Sheep Veterinary Society and of the South Wales division of the British Veterinary Association Kate Hovers, from Trecastle, Brecon, told delegates many parasites are now becoming resistant to treatment partly due to medicines being inadvertently used inappropriately.
A misdiagnosis of the cause of ill-health also often leads to the animal not being treated correctly, Ms Hovers said. This makes it vitally important that farmers have an effective parasite control plan in place, preferably agreed in conjunction with a veterinary surgeon.
“We know anthelmintic resistance is present and common in some parasites, and most will have some resistance to the BZ (white) drenches,” she said.
“Every time such a drench is used the proportion of resistant worms on the grazing and in the flock increase until eventually it affects production and becomes noticeable in your cash flow.”
The committee heard that the overuse of products will always speed up the time to resistance, especially for worm drenches, ectoparasite treatments and antibiotics and that this is very important when treating, for example, sheep scab.
Ms Hovers said farmers need to be aware that every time an injectable is used for scab control it also worms the sheep.
“Overuse will cause resistance to these products over time, and while that may not be evident in many flocks now, it will likely affect the next generation, leading to problems fattening lambs,” she added.
FUW animal health and welfare committee chairman Catherine Nakienly said: “There are many reasons for the apparent lack of effectiveness of a treatment so advice should be sought both on a routine plan and on monitoring the products used for effectiveness and possible resistance problems.
“We need to raise awareness in the industry that many parasites in sheep are now becoming resistant to some of the products used and that treatments should be appropriate and only carried out when needed.
“There are so many benefits to the effective control of parasites and we would urge farmers to discuss a plan with their veterinarian,” added Dr Nakienly.