The dung in the photo below is from a two year old warmblood gelding called Eric, after he was wormed with a 5-day fenbendazole treatment in April 2024. That's a rather alarming amount of redworm but his story isn't uncommon in his age group and so we thought you'd be interested to know more about his story and the approach we're taking to his treatment.
Eric lived the first two years of his life at the stud where he was foaled, hanging out with other youngsters and enjoying life, a great start for his development but high risk for parasite infection as we know youngsters are so much more susceptible to worms. In December 2023 Eric had a moxidectin + praziquantel wormer for the possibility of encysted small redworm and tapeworm.
In April 2024 as a two year old, he moved from the stud to start his new life, into a field with two other horses that is regularly poo picked which makes for a lower risk environment.
One of first things his owner did was to carry out a worm egg count. The test came back as a high count of 1250 epg for redworm. As he was last treated with moxidectin and the stud are known to have relied quite heavily on this chemical for their worming treatments, we advised a 5 fenbendazole with a reduction test. The worm egg count had reduced to 50 epg so this had been effective.
Eric's age and results make him high risk for parasite infection so we recommended testing again in 8 weeks time. A worm egg count on 21st June came back higher at 2,300 epg. This was most likely amplified due to a combination of residual untreated larvae in the gut, the stress of the move impacting his immune system as well as the possibility of reinfection. He was treated with an ivermectin and a reduction test of <50 epg showed that too had been effective. He'll have another worm egg count 8 weeks on in mid August to check progress.
We're happy to report that Eric's new owner is thrilled with him. She says he 'looks amazing, has put loads of condition on and grown in four months'. Untreated parasite infections can and do stunt growth and certainly prevent a horse from reaching its full potential. Good worm control is an important consideration at such a critical time of development.
Conclusions to note:
Eric had recently come from a stud, where the risks of infection and potential resistance are greater due to the higher number of young stock on the premises and therefore the need to target a wider range of parasites more frequently. This favours faster development of a resistant population and horses that go onto new homes then carry these strains with them
A reduction test, 10-14 days after each treatment to check the wormer has done it's job is really important. If we hadn't done the reduction test in April it would have been easy to say the fenbendazole treatment hadn't been effective but the reduction test proved otherwise. Worm egg counts carried out every 8 weeks, using further reduction tests as needed, will then help us know which parasites/chemicals are affected on the grazing and so be more targeted in the management advice and treatment choices.