We lost our beloved ewe, Mocha, last Friday, but she taught us a valuable lesson on the way out. Mocha was our first Moorit (recessive brown) Romney ewe, after breeding efforts over several years. She wasn’t just beautiful in her coloring, she had a huge personality, forward and talkative from the time she was a lamb. She was determined to learn how to drive that ATV that brought the food every day.
Mocha was a single lamb, and her mother, Aulait, raised her well. She was the largest lamb in her class, and we decided to breed her because she had reached nearly her expected adult weight. She was pregnant with twins according to Dr Dotti’s ultrasound, due in early March.
Then last Thursday, just a week or two before her due date, Mocha seemed “off” one day, slow to come to eat her dinner. Friday morning she was totally off her feed and seemed depressed, but her temperature was normal. We brought her into the barn and consulted our vet. It didn’t seem like pregnancy toxemia, which usually presents with a subnormal temperature, or an infection, which would generally produce a fever. She had a tiny amount of pinkish discharge, never a good sign, and we figured maybe she was aborting. We gave her supportive treatments, vitamin B complex to boost her appetite, and energy supplements to give her electrolytes and energy, since she was not eating. There was not much else to do but watch her. We did notice a hint of a foul smell around her, and I was worried she may have rotten lambs, lambs that have died and decomposed in utero, which happened to us once before in 2011.
Mocha died Friday night. The next day the smell was very strong, and I decided we needed a necropsy to understand what had happened and whether we had a flock-health problem.
Dr Jasperse at Cotati Large Animal Hospital found that Mocha indeed had rotten lambs. They were close to term, so had died recently, but were extremely decomposed. I had always thought that rotten lambs occur when the fetuses die for some reason like a detached placenta, and then bacteria are somehow introduced and decompose the dead fetuses. But it turns out that most cases of rotten lambs occur when the ewe becomes infected with Clostridium sordellii, one of many Clostridial bacteria that can infect sheep. This strain of Clostridium kills the fetuses and then multiplies in the uterus, rapidly decomposing the fetuses.
Tetanus is the most well-known clostridial infection, but there are a number of others. What they have in common is that the bacteria are common in the environment, infect animals at random and relatively rarely, but when they do, they multiply extremely fast and are virtually always fatal. Most shepherds vaccinate their flocks against clostridial infections. We use Covexin-8, a vaccine against 8 clostridial strains.
But what I learned last weekend in my research is that Covexin-8 does not protect against C. sordellii! Even without vaccine protection against C. sordellii, we have had only two cases of rotten lambs in 15 years, and I am not worried that we are about to have an epidemic of rotten lambs, because that is not how clostridial infections generally emerge. They come individually, but their deadliness means there is nothing you can do when they strike.
We are so sad to have lost Mocha, who was a very special ewe. But grateful on behalf of the rest of the flock for the lesson we learned about the cause of rotten lambs, and what we can do to prevent it. I learned there is a newer vaccine than Covexin-8, called Cavalry-9, which protects against all the strains included in Coven-8, PLUS C. sordellii. From now on we will vaccinate our flock with Cavalry-9, and rest a bit easier as lambing-time approaches.
