A Yorkshire Vet Through the Seasons

I hadn’t had a very good week. Monday and Tuesday had seen me blood testing a flock of six hundred sheep to check them for a viral infection called Maedi Visna. The flock had been accredited free of this disease, but the last routine flock test had flagged up two positive cases. This was disastrous. They had lost their accreditation. As the animals were a high quality, high pedigree flock, it was crucial to be free of Maedi Visna. To restart the process of becoming disease-free and accredited as such, every adult animal needed to be tested and all the results had to be negative.

Testing six hundred sheep was a long job, partly because they were scattered around several holdings in the area. By halfway through Monday morning, I had finished the first batch and made a start on the second, which was at the main farm. The system there was very good and the handling facilities were excellent, which made the undertaking very much easier than it often was. There were plenty of assistants on hand to catch and hold each animal, so my job was simply to take blood from the jugular vein of each of my woolly patients and write its ear tag number in a book, alongside the number from the side of the tube containing the blood sample. In this way each sample could be matched to the appropriate sheep.

The handling pen was the same area in which the sheep would have been dipped in years gone by, to prevent sheep scab (a nasty skin disease caused by a mite) and to limit the effects of blowfly strike during the summer. The dipping of sheep is not really practised any more. The strong chemicals that were used have now been banned (unless you hold a specific licence) and it is very difficult to dispose of them correctly. Other, safer methods of control have been developed, but the long and deep troughs, which were previously used to submerge each sheep, still exist at the site of most sheep-handling facilities. Here, the dip was just on the other side of a wooden gate close to where I was working. It had long since fallen into disuse, but had not been drained of the noxious fluid. Layers of dead leaves had fallen onto the surface of the liquid and, partly decomposed, had formed a large and thick mat covering the whole of the dipping area. The recent fall of autumn leaves, made worse by heavy rain, had caused the edges to merge with the surrounding ground and the fetid liquid underneath was perfectly disguised.

It could not have been a more brilliantly conceived trap and it is not difficult to imagine what happened when I leapt over the gate so I could deposit my first polystyrene box of fifty blood-filled glass tubes safely on the passenger seat of my car. I always liked to put a full box of tubes out of the way to avoid the risk of them being knocked over and smashed. I hurdled the gate and both my feet landed on what I thought would be solid ground. Then, everything happened in slow motion. I plunged, without warning, up to my neck in the foul-smelling black soup of sheep dip and rotting leaves, which bore little resemblance to anything I had been submerged in before. I clambered out, soggy and smelly, to peals of laughter from everyone standing nearby.

‘Oh yes, I was just about to say,’ the farmer called from the other side of the gate.

‘Watch out for the sheep dip. You’d never know it was there, hidden under all those leaves – which reminds me, we really must sort that out!’

More sheep took up the second part of my week and more testing was required. Wayne, a young farmer who I knew well, had found a couple of dead sheep in one of his fields during the weekend. He had put these deaths down to pneumonia, brought on by the bad weather that had recently affected the area. Heavy rain and strong winds had caused flooding in parts of North Yorkshire. Sheep can easily tolerate cold weather, with their thick woolly fleeces, but they detest rain, in particular persistent, heavy rain, which can permeate their lanolin-coated wool, leaving them cold and miserable. But, when he found another half dozen dead a few days later, Wayne was worried. He usually had a keen attention to detail but he couldn’t work out what was going wrong, so he asked me to have a look at the flock.

The affected sheep were from a batch of weaned lambs that had been born in the springtime. They were now about six months old and had grown big and strong, on a combination of their mothers’ milk and the summer grass that grew thick and green in the pastures along the side of the River Swale. A farmer who had a holding just three miles downstream from Wayne’s farm had once told me that this land was some of the best farming land in the country. The mineral-rich water that came down from the hills at the top of Swaledale, around Muker, Keld, Reeth and other such lovely places, brought vitality to the fields along the length of the river. In the autumn lamb sales at Thirsk Auction Mart, Wayne’s sheep would always be amongst the best.

When I arrived, he and his father had already gathered the young sheep into a small paddock adjacent to a holding pen, which would enable me to examine the affected animals and take any samples that I deemed necessary. His lambs did not look as they usually did – some were healthy, but about a third of them were thinner than they should have been and eight out of the group of three hundred had died. The sales were coming up, but it was looking unlikely that any of the lambs would be achieving the top prices to which Wayne was accustomed.

I launched into my usual questioning, probing for clues. In the recent heavy rain, the pastures close to the river had flooded, necessitating a temporary move for the lambs. However, once the floodwaters had subsided, Wayne had moved the flock back to the riverside. I pressed him for more details on the condition of the fields. They were not waterlogged, he reported, and the floodwater had receded several days before the sheep had been moved back onto them. The land had drained well and was not at all boggy. This was a crucial piece of information, because parasitism by liver fluke was at the top of my list of ideas. Sheep can acquire this nasty parasite from grazing on waterlogged fields, especially in autumn, and we had seen a sharp increase in cases in recent years. In fact, until recently we never really saw cases of liver fluke on the eastern side of the Pennines. However, the increasingly wet weather in summer and autumn, attributed to global warming and climate change, has meant that the condition has now become quite common, rather than a rarity.

I examined a few of the thinnest animals, but there wasn’t much to see. The next step towards an accurate diagnosis was quite obvious. A post mortem examination was required. I phoned the lab to let them know that Wayne was on his way with three of the recently deceased lambs. We were both anxious to get the answer as soon as possible. We didn’t want any more deaths.

Later that afternoon, I received a phone call. It was Gary from the lab again, full of the excitement that I had come to expect from this pathologist when he was on the trail of a diagnosis.

‘Hello, Julian!’ he said cheerfully. ‘It looks like acute pasteurellosis! The lungs are purple with haemorrhage. Have these lambs had any vaccines?’

I confirmed that yes – they had received the correct vaccinations, at the correct time. Wayne was as diligent as any farmer I knew.

‘Hmm, well.’ This had put a slight damper on Gary’s excitement. ‘Sometimes disease can break through against a vaccinal titre. It has been awful weather recently. I think I might have developed pneumonia if I’d been out in weather like this! We’re running some more tests, just to confirm. I’ll keep you posted … Oh, another thing – the livers were all clear. Not a trace of fluke, so we’re clear on that one!’

I wasn’t convinced by the diagnosis of pasteurellosis, although Gary clearly was. He had seen the lungs though, and that was his job, after all. I called Wayne to check the vaccine history again. He confirmed that not only had the vaccines been done, as always, at the correct time, but the sheep had also received an extra dose only three weeks previously, in anticipation of the weather. This ‘back end’ had been a wet one so far! I advised him to give a precautionary course of antibiotics to any sheep that looked poorly and also to move them onto another pasture. The second part of this advice was risky – moving sheep from place to place can precipitate disease crises through stress. Pasteurellosis – our ‘working’ diagnosis – could even be triggered by moving sheep from one field to another. Wayne also knew this, but we both agreed it would be sensible, just in case the grazing itself was the cause of the problem.

Three days later, Wayne had done all he had been advised. He had moved the lambs and injected about a hundred sheep with antibiotics in a bid to prevent them from getting any worse, but there had still been more deaths. We had been in contact twice a day by telephone, while we awaited the final test results from the lab. The phone call came halfway through Monday morning, and changed our diagnosis immediately.

Toxicological testing on the kidneys and liver had revealed dangerously high levels of the heavy metal in the organs of each of the three lambs sent in. The fax confirming this quickly followed the phone call. Despite the relief of having a definitive diagnosis, the gloomy headings on the top of each page did nothing to lighten my mood.

Lamb 1: Lead poisoning with secondary pneumonia.

Lamb 2: Lead poisoning, minimal secondary pneumonia and

nephrosis.

Lamb 3: Lead poisoning, mild secondary nephrosis.

Diagnosis: LEAD POISONING.

How had these lambs, grazing the fertile fields alongside the Swale, been exposed to lead? I did some more research before calling Wayne with the news, and what I discovered was more a lesson in geology than in veterinary epidemiology. In years gone by, the landscape of parts of the Dales was not only rural but also industrial. The scattered ruins of lead mines can still be seen in many places. The recent heavy rain had resulted in large quantities of water washing through the lead seams of upper Swaledale, from where the River Swale originated. This water, contaminated by high levels of the toxic mineral, in the form of silt containing lead ore, ran off the hills and into the river. As the river burst its banks further downstream, the silt that had been held in the current was deposited onto the fields where Wayne’s sheep had been grazing. The hungry lambs, cropping the grass short and therefore taking in silt as well, had eaten sufficient quantities to damage their internal organs and destroy their blood cells.

Wayne immediately made sure all his lambs were safely inside, away from the dangerous grass. There was no practical cure that could be administered to the lambs. The only drug that might have been helpful needed to be injected intravenously every day, into every sheep, for about five days, which was completely unfeasible given the size of the flock. Wayne and his lambs would just have to sit it out and wait for the lead to leach out of both the lambs and the grass.

The disaster had been contained, although it took many more tests and was quite some time before the lambs were safe for human consumption. The farm next to the River Swale would not be grazing sheep on recently flooded fields again.

It did not take long before I was drawing upon my newfound knowledge elsewhere. Only two miles downstream and two weeks later, I found another case of lead poisoning, this time in a herd of Simmental cattle.

The sight in Gordon’s fold yard was a sorry one. It was full of about forty year-old store cattle. Gordon had purchased them from nearby hill farms, where they had been overwintered on barley. He fattened these animals on the plentiful grass in the fields around the confluence of Cod Beck with the Swale. The cattle, which were usually a picture of health, with white and deep tan markings, did not look so good. Gordon pointed out about six who were standing, ears down, staring into space and not moving at all. It was otherwise a beautiful autumn afternoon. The sun was doing its best to provide some end-of-season warmth before it slipped out of sight. Gordon explained all, pre-empting my questions. The Simmentals had arrived about three weeks before. The weather was still good and, in the autumn sun, the land nearby his farm had dried out after the recent flooding. The cattle had enjoyed an Indian summer – admittedly one punctuated by an Indian-style monsoon – finishing off the last of the grass. They had obviously tucked into it with some enthusiasm as it would have been vastly superior to anything they had experienced before, coming as they did from upland farms.

‘It was just this morning that I didn’t think they looked quite right. So I spent an hour or so getting ’em all in, so I could have a closer look.’ Gordon was tense. ‘It’s just those six really. I’d be hard pushed to say that there is much wrong with the others. I thought you’d better come and have a look. You’re the vet, you should know what’s up wi’ ’em. I don’t want to lose any – they cost me a fortune. Stores like this are not ten a penny. If I lose any, well, it’s my profit gone, you see.’

The more Gordon spoke, the more I felt the pressure rising. I thought I had better interject.

‘Well, everywhere really. All those fields down there.’ As we stood on a mound just outside the farmhouse, Gordon pointed out the extent of the grazing which, luckily for me and my diagnosis, included large tracts of land right along the banks of the river. And yes, they too, had been completely flooded about four weeks before.

‘The flooding’s been bad here,’ he explained. ‘You see, where Cod Beck joins the Swale, the water sort of backs up and it goes everywhere. Especially if it’s been over-wet in the Hambleton Hills as well as the Dales.’

We went back inside to have a closer look at the sick animals. In contrast to lead poisoning in sheep, which usually manifests itself as sudden death, in cattle the disease progresses more slowly. The affected animals develop neurological signs, most frequently characterized by loss of vision. Sure enough, on close examination, these Simmentals were following the textbook perfectly. They were all blind. I confidently pronounced my diagnosis of lead poisoning. It did not impress Gordon as much as I had hoped. The farmer was sceptical.

‘Well, we’ve had this farm for generations and I’ve never heard of anything like this before. Could it not be pneumonia?’

I explained the signs and my theory, as we examined each blind animal. There was nothing to suggest it might be pneumonia, but there was also no definitive test, other than post mortem examination, to confirm that it was lead poisoning. There were no suitable candidates for post mortem at the moment, and to wait until there was one might be leaving it too late for the possibility of curing the others. Gordon’s mood and his confidence in my diagnosis were lifted slightly when I explained that treatment might be feasible for this small number of beasts, if we gave it straight away. We would need to inject a drug called calcium edetate intravenously, every day for about five days. Gordon’s demeanour drooped again. Five daily visits from the vet and probably lots of bottles of medicine sounded expensive. I felt somewhat despondent. I had made a pretty good diagnosis (without the need for any expensive lab tests), offered a treatment that would very likely save the lives of all his animals (which he had already pointed out were very valuable and that he couldn’t afford to lose) and I had offered to treat them every day until they were cured. I didn’t know what more I could do.

I explained it all again and Gordon wandered off into the corner of the fold yard to contemplate the situation. After what seemed like an hour, he stomped back to the cattle crush where I was waiting, and nodded his head.

And so I sprung into action, injecting the life-saving medicine into each of the stricken animals. This was what being a vet was all about for me – making a diagnosis and administering a cure. I was in my element. It was so much better than falling into a sheep dip!