Eamon O’Connell: How roughage or a dosing gun can mean the end of healthy sheep

That’s partly because we don’t have nearly as many sheep as cows in this part of the country, but it could also be because a former boss of mine might have a more apt view – a sick sheep is a dead sheep.

His opinion was formed by his experience in treating ewes and lambs, which were often too advanced in their various disease processes for treatment to save.

We are now often asked to hypothesize the cause of death of a ewe or lamb rather than being given a chance to treat it. Sheep are very good at hiding the fact that they are sick, so they often present themselves as “suddenly” very sick or, even more suddenly, very dead.

This week we’ve seen a few such cases. I received a call from a very good farmer who was disgusted that he had found a purebred Texel ram dead in the field.

The nine-month-old lamb appeared to be in good shape up until the previous day, so the scene he was presented with when he arrived at the paddock with his meal was not what he expected. As with any case like this, my advice was to take the lamb to the nearest regional veterinary lab for a full autopsy.

The veterinary laboratories provide an absolutely brilliant service, especially with autopsies. In the case of this particular lamb, the results came back extremely quickly. The lamb arrived at the lab at 11am and we had a diagnosis that same afternoon.

We were told that the condition the lamb succumbed to was ‘Texel throat’. This is the slang term for laryngeal chondritis — a bacterial infection of the larynx (throat area) characterized by swelling, abscess formation, and eventual blockage of the air inlet, causing suffocation and death.

The Texel breed seems more likely to develop this condition than other breeds. This is thought to be due to their short head and neck, which affects the anatomy of the area around the larynx.

The area must be initially irritated for the condition to develop, so rough feeding or previous pneumonia can trigger the condition. It can sometimes be traced back to dosing a week or two earlier, where someone being a bit too rough with a dosing gun hurts the lamb’s throat.

Early diagnosis of this condition can give time for treatment, but success can be rare, particularly in Texels, as the infection is ’embedded’ and difficult to penetrate with antibiotics and anti-inflammatory drugs. However, as I said before, most of the time we only see these conditions when we are looking at a dead lamb.

It is always worth looking into the feed if there is a lot of roughage in it, which can lead to throat irritation. An interesting case, but unfortunately a dead lamb nonetheless.

Thankfully, we’re able to keep some of the sheep we see alive, thanks in no small part to the increasing emphasis placed on the responsible use of anti-parasitic drugs.

Resistance to dewormers has long been a problem in sheep herds, but by and large it has been in the face of ostrich treatment – head in the sand and hope the problem goes away.

But it didn’t go anywhere. In fact, it’s gotten a lot worse. A farmer brought us some faecal samples last week from a group of lambs that were just “not feeling well”.

They had received a white dose a few times, as well as various other drenches and injections at various times in the recent past. When we analyzed the samples on our in-house fecal sample analyzer, the results were remarkable, but unfortunately not surprising.

The average worm count of the group was 5,000 EPG. EPG stands for eggs per gram of feces. It’s exactly what it sounds like – how many worm eggs are there in every gram of fecal material. 500 EPG is usually the cut-off point when a worm dosage is recommended, so these lambs had 10x the recommended amount of worms.

The problem on this farm is that we had no idea which class of dewormers wasn’t working properly as these lambs were literally having the kitchen sink thrown at them.

We have therefore decided to carry out a faeces-egg reduction test for each of the three different classes of dewormers. We divided the lambs into three groups.

We sampled 10 lambs in each group and then administered the designated dewormer to each group. We then came back to each group (on different days depending on which dose was used) and sampled the same lambs again.

The reduction in the number of worm eggs per gram tells us whether the dose is either fully effective, partially effective, or not at all effective.

Fortunately, in this case we found that the third group of dewormers (which include ivermectins) were still fully effective. The other two groups were not effective at all. From now on we will work very closely with this farmer in relation to the dosage, since resistances to all anthelmintic groups are within reach in the case of errors.

We’re starting to see some positive leech samples arriving as well lately, which is worth keeping an eye on, especially for early lambing ewes who will be under enough stress without adding leeches to the mix.

I won’t start with the crib donkey. The fact that mine recently ate a recently planted hedge means it’s in the bad books, at least for a while.

​Eamon O’Connell is a Veterinarian at Summerhill Vet Clinic, Nenagh, Co. Tipperary.