Parasite resistance is becoming more of a problem over time
Definitely now that the grazing season is in full swing, gut and stomach worms are going to start building up.
It’s a good time, six to eight weeks after turnout, to do a faecal egg count for calves that are raised without a dam, such as dairy beef animals, said veterinary epidemiologist Dr Natascha Meunier from Animal Health Ireland, speaking to Catherine Egan on a recent edition of Teagasc’s The Beef Edge podcast.
The level of parasite infestation can be assessed via the test. “Suckler calves probably don’t need to be monitored too closely until the end of the season, as we’re coming into autumn."
“Definitely now that the grazing season is in full swing, gut and stomach worms are going to start building up”, Dr Meunier said.
“You wouldn’t necessarily be needing something that’s targeting fluke at this time of year; it would be something that was targeting more gut and stomach worms”.
Products chosen to treat parasites depend on the disease history on the farm, and advice from one’s vet can be helpful in this respect.
“Resistance is becoming more of a problem over time, and more widespread,” Dr Meunier said. Resistance means the product is not killing the parasite as effectively as it should, whether worms, flies, lice, mites or other parasites.
Farmers should particularly note the active ingredient in a product if they feel its effectiveness is reduced, since any alternate product purchased should contain a different active ingredient.
There are only three broad classes of medicines that are available to treat worms in cattle, so it can sometimes be difficult to determine which product will work best in particular circumstances.
“For cattle, the three broad classes that we have are the white drenches, the yellow drenches and the clear drenches and which one we use depends on what’s working on the farm,” Dr Meunier said.
Any of those should be effective against gut worms, but if one knows there has been a problem with one of those types of drenches previously, then the farmer needs to switch to an alternative, seeking perhaps the advice of their vet.
The degree of resistance will depend on the proportion of the population of gut worms that are carrying resistant genes. The resistance is within the worms, not the animal carrying them. It is only when a significant proportions of the worms are resistant that the wormers noticeably stop working.
“It’s much better to try and catch it early before you’re noticing any problems with the effectiveness of the medicines themselves because then there are still steps to be taken to slow it down,” Dr Meunier said.
Once certain medicines no longer work, that becomes a permanent issue on that farm, and since one has only three options with which to work, for worms, it is far better to prevent resistance becoming established.
When drugs no longer work, pasture management, lower stocking rates, and other strategies need to be employed.
In any case, to reduce the number of treatments needed against parasites, an integrated strategy is best adopted.
The Targeted Advisory Service on Animal Health (TASAH) can be consulted by farmers to determine whether resistance is a growing issue on their farm. “It’s essentially an opportunity to get your vet out on the farm to advise on parasite control,” Dr Meunier said.
This is a free service available to all cattle and sheep farmers in Ireland. The purpose of the parasite-control TASAH is to facilitate discussions and planning between farmers and a trained participating vet on best parasite-control practices, with the long view of minimising development of anthelmintic resistance.
The TASAH will fund a veterinary farm visit and two faecal egg count tests for roundworms (stomach or gut worms). “That can also be used to test whether the medicines are still effective on the farm, using a drench test,” Dr Meunier said.
The farmer will nominate the trained vet to carry out a herd or flock visit to look at parasite control. Farmers who participated in the scheme last year will remain registered for 2023 and can book another vet visit prior to the programme closing date of October 31. Those who wish to register for the first time can do so via the Animal Health Ireland website.
Farmers can check if their vet is listed amongst those trained and participating in TASAH. If they are not, they should be able to advise if another vet in their practice, or nearby, is in the scheme. The vet will be able to advise on the best time to take faecal egg count tests, depending on the particular farm situation.
"If you want to test whether your drench is still working effectively, if you think it’s maybe not working as well as it used to, then I would suggest chatting to your vet or adviser on the protocols for that. It needs two samples, before and after treatment, and your vet can advise on the timing, depending on which drug you’re using,” Dr Meunier said.
Any treatments of yearlings would depend on the farm.
Weanlings may have built up some immunity to some worms, others might need treatment. Lungworm, with characteristic coughing, can become a major issue, particularly towards the end of the season. Lungworm is not readily detected in advance by faecal egg count analysis.
In other parasite advice, Dr Meunier said coccidiosis may have been an issue on farms, and now is the time to thoroughly disinfect any sheds, using a disinfectant that is effective against coccidia.
Flies are becoming a problem and can spread summer mastitis or pinkeye.
Ticks can also be a problem, in certain areas, spreading the parasite which causes redwater.
