.jpg){kind=logo}
WORMING
It’s getting to the time of year where national hunt is hugely underway. This generally means the temperatures are beginning to get very chilly, therefore, it is also time to think about encysted redworm…
Unlike most other infectious diseases in horses (strangles or influenza) which infect only a small amount of the population at once, worms are present in most horses, all of the time. Sadly, this means it's almost impossible to get rid of them, therefore, effective worm management is pretty essential.
The threat to racehorse performance caused by intestinal worms is not one to be overlooked. For many years, very regular anthelmintic (deworming) treatments were performed which has now inadvertently led to widespread resistance to these wormers and negatively impacted their effectiveness. Bearing this in mind, it is important to consider how best we can control worms, whilst protecting the efficacy of the wormers we have remaining. In summary, this consists of drug and non-drug control measures.
Which worms are the problem:
Worming is hugely confusing as they go by many names, all of which go through different life cycles and are also treated with different products at different times; all with varying degrees of resistance! Very briefly, horses can be infested with… large red worms, small red worms, roundworms, pinworms, threadworms, tapeworms, lungworms and bots. The main worms we are concerned about are strongyles (large and small red worms), roundworms and tapeworms. Redworms are the most relevant worms in race yards so the majority of this information will focus on them.
So, what are encysted redworm and why an Equest Pramox strictly after the first frost?! Specifically, this is due to the lifecycle of the redworm.
Redworms (also known as small strongyles or cyathostomins) are worms that are ingested by horses at pasture when they are in the larval (egg) stage. Following this, they reach the large intestine where they burrow into the deeper layers of the gut and become “encysted” (usually when the temperatures drop consistently below 6 degrees and it is not favourable for them to live on pasture).
These encysted redworms are at the highest risk to the horse when they re-emerge and mature into adults in the large intestine - typically occurring in the spring. This can lead to a physical blockage of the large intestine and damages the intestinal wall lining, often leading to clinical signs such as diarrhoea or colic. Longer term, small redworm infestation can cause chronic damage to the intestinal wall and reduce the horse's ability to absorb nutrients. It is worth noting that the worst affected horses are usually under 5 years of age.
Symptoms of redworm infestation:
· Loss of condition
· Weight loss
· Distended stomach
· Colic
· Diarrhoea
· Chronic “bad doer”
· Hypoproteinaemia (low blood protein)
· Peripheral oedema (swelling)
Know at risk horses and identify high shedders
As previously mentioned, most horses will have a worm burden of some kind, however, the adult worm burden and the number of worm eggs shed is much higher in young horses. Horses below 5 years of age are at greater risk as there is believed to be a degree of age-related immunity involved.
Methods of testing / prevention =
Regular faecal egg counts (FEC) are a method of telling you what worms are present in your horses’ faeces but also how many eggs per gram of faeces
Regular FECs will enable you to build up a picture of the high shedders and target treatment towards them rather than treating the whole yard
It is worth noting that encysted redworm cannot be detected using a worm egg count - this is why we routinely treat for encysted redworm once a year). Faecal egg counts only detect egg-laying adult worms, therefore, blood tests for red worm can now be performed to identify antibodies to red worm (and tapeworm)
Faecal egg count reduction tests (FECRT) = This follows on after a horse has been identified to have a high worm burden and has been treated, another FEC is performed 10-14 days later and the percentage reduction in egg numbers is calculated - can be used to test the effectiveness of the wormer
Tapeworm = Blood or saliva test 6-12 monthly depending on level of risk
Methods of Treatment =
Whilst it seems that there is a huge range of deworming products, the number of active ingredients in these products that are not facing resistance is very limited. Below are the treatment options:
Redworm = Fenbendazole, pyrantel, ivermectin + moxidectin
Pitfall = Resistance to fenbendazole and pyrantel
Encysted Redworm = Moxidectin or 5-day course of fenbendazole
Tapeworm = Double dose of pyrantel
Roundworm = Fenbendazole or pyrantel
Bio-security measures
One of the challenges posed to racing yards is the high turnover of horses with many leaving for rest/recovery and others returning or new horses joining. In an ideal world, when a new horse joins, they should be isolated, tested and treated prior to integration. This is because this horse could be carrying new or resistant parasites and their worming history is unknown. Also, although not always practical, poo picking (the worst job ever) and grazing rotation with other animals is beneficial.
Take home messages =
Encysted redworm won’t show up in a faecal worm egg count
Treat horses for encysted redworm once a year - ideally when temperatures are consistently low using wormer containing moxidectin (equest or equest Pramox)
Carry out worm egg counts over the spring summer to assess requirement for wormers rather than blanket / over worming. The aim here is to leave individuals with low WECs untreated to encourage non-resistant worms.
Even better - a faecal egg count reduction test during the grazing season is the best way to ensure the wormers are working properly
Finally, you may think this all sounds a little like hard work and extra admin but, it was recently shown that the use of worm egg counts in a targeted worming strategy actually reduces (!!) the cost of de-worming compared with intensive interval treatment protocols…you would be surprised that worming the whole yard routinely is often surplus to requirements!
Any questions please let us know!
Thanks,
Molly & team
Want more of these? Then register to our newsletter on www.guascoandassociates.com
Comments