MONDAY evening was coming to a gentle close as I headed home to a welcoming dinner. And then the phone rang. It was the office, passing on a fresh call that came in just before they closed for the day. “A yearling with colic, and apparently it’s fairly bad,” was the message.

They always are, those evening calls. It’s usually a horse owner whose work keeps them away from home all day and the poor horses are not seen until late in the evening.

In this case, it was late in the day for the horse’s condition, never mind the hour on the clock. It was a home-bred sport horse yearling that had been part of a group of five other horses of various ages.

The rest looked fine, but this guy was in some sorry state, I can tell you. He was skin-and-bone and had a dirty tail where he had been scouring profusely for quite a few days. With the owner distracted at work and the dark evenings when work finished, it was hard to spot that this horse had not had a normal faeces for quite a while.

The animal staggered a few steps when the owner went to catch him for me in the shed. With that, the horse collapsed and couldn’t get up again no matter how we coaxed him. The inevitable happened and the animal was euthanised on humane grounds.

All very dramatic and all very sad, but we cannot just walk away at this point. We would have to carry out a post-mortem examination on this animal.

There were too many questions and too many concerns for others in the group, never mind the possibility of a disease that could affect man as well as the horse. And thank you again to the men and women who run such an excellent service in the Irish Equine Centre in Co Kildare. A post mortem was arranged and we had the report back in no time at all.

WORM THREAT

This guy had an acute bout of cyathostominosis. A big word for such microscopic worms, but these are microscopic worms with a difference. This condition involves a massive build-up of miniature redworms that develop in the gut in significant numbers over a period of time.

They act in a peculiar way to the normal worms of everyday. Peculiar in the sense that they remind me of the film “Alien” all those years ago.

The worm burrows into the lining of the bowel and forms a cyst that lies dormant in the tissues for a long time ... almost like a state of hibernation.

The numbers of these hibernating cysts build up slowly over the year and then suddenly, they all emerge from the gut wall in one large tsunami, causing untold damage to the lining of the bowel. The bowel is so badly damaged by these emerging worms, that the animal cannot properly absorb any nutrients from its diet.

The horse develops a really bad scour or diarrhoea as the malfunctioning gut cannot make correct use of the contents of the diet. The massive activity of this newly emerged tide of worms now active again in the centre of the intestine, leaves the horse depleted in blood (hence the red in the worm).

It also leaves him depleted in energy and in blood protein as the constituents of the blood seeps out into the lumen of the gut.

WORM DOSING

The horse is simply drained from the inside-out until they collapse in a heap and die. They waste away in a very short time indeed. The condition is thankfully rare, but needs to be recognised early and treated immediately.

Worm dosing is the treatment but it is important to use the correct product at the correct dose as with all medicines in such cases. Your home veterinary surgeon will guide you best on a worm programme that avoids this scenario but there are a couple of important points that we can point out at this juncture.

This condition is a somewhat unusual activity of the everyday parasites that affect our horses throughout the year. The full pathways that cause this winter scour are not yet fully understood but it seems to be a phenomenon seen in young horses in late winter or early spring.

So much so that a drug manufacturing company (Zoetis) has issued a timely warning about keeping an eye out for this condition at this time. They ask horse owners to closely observe their stock, especially their yearlings, two-year-olds etc and especially now as the spring is approaching.

It is thought that the worms’ activity described above, is a method of survival for the worms themselves and a method of hibernating comfortably over the winter. At the end of winter, they suddenly emerge and infect the fresh grass of spring at the beginning of the grazing season. That’s all fine for the parasite but it’s far from fine for the host.

The drug company’s warning is a timely one, and must be seen in the light that the company supplies a worm-product effective in treating this condition. All said, we must recognise the importance of such research and development by the drug manufacturer and be thankful of the investment in bringing such a product to market.

So for that process, we appreciate this timely reminder.

We must be equally cognisant of the need to be prudent in our use of veterinary medicines at all times. Hence best advice involves consulting your veterinary surgeon and going through all the steps involved in the control of worms on your holding. This will vary from paddock rotation, to leader-follower grazing programmes for all young stock, to faecal sampling pre and post-worming in some cases right through to zero worming where a wormer is not required at that particular time.

As it happens, a faecal sample would be of little use in the case of an animal harbouring larval cysts as the hibernating worms shed no eggs during the dormant period.

Control of this parasite involves a well thought out and correctly focused parasite control programme that prevents the build up of these cysts in the first place. The cysts build up when there is a heavy worm burden equally as much as when someone overuses a specific worm treatment. And so lies the conundrum. This unusual pathway in the lifecycle of the worm is an effort by the parasite to react to unsavoury threats to its existence. That could be in the form of a very heavy worm burden when no worm dosing is in place. It is also a threat to the parasite when the worm is exposed to excess worm medicines. It’s almost a case of damned if you do and damned if you don’t. But not quite.

SAMPLING

We should only worm our horses when a wormer is indicated. By that I mean we should send in faecal samples to our veterinary surgeon to have them analysed on a reasonably regular basis. This will help to ensure you only worm when a wormer is indicated. The worms are treated when numbers begin to rise.

We are not aiming at a zero tolerance here. We know that horses build up their own immunity in response to a challenge by the worms. It is important to let that process develop while keeping an eye on the worm numbers to stop the parasite numbers growing out of control.

This sampling process ensures that our young horses do not get overexposed to excess worm medication and the worm numbers do not grow to alarming levels. Then and only then can we control cyathostominosis and hope to prevent its build up in our home stock.

Get out there with the freezer bags. Get the samples in to your veterinary surgeon. Get a programme put in place that is focused where it should be, using only those products that should be in horses that require it for a period that best suits your farm. Resistance to wormers is well described and not the topic of this article. But the mantra still stands.

“Use the appropriate product in the appropriate animal at the correct dosage for the correct period and be brave enough to identify when no product is required at all.”

Then we will always have adequate response to the use of a medicine when we actually really need it.

So happy grazing to all your horses and “sin sin go dtí an chéad uair eile.”

Peadar Ó Scanaill MVB is a member of the Equine Group of Veterinary Ireland and is in practice in Ashbourne, Co Meath

Email: hq@vetireland.ie

Telephone: 01-4577976