Each year, around late winter and early spring, we get the odd case of yersiniosis coming through our labs. The seasonal conditions this year are, so far at least, more favourable for this disease - ie the conditions are right for it to be a more significant problem over the next few months. Prevention is better than cure, so the following may be of use for hobby farmers or anyone else who has sheep or goats and not a lot of experience.
Yersiniosis is a gastro disease. In healthy sheep/goats that are not under stress, it is usually subclinical (ie it is mild and you won't see the signs). In stressed sheep and goats, the signs are very similar to worms - ill thrift and scours, particularly in young stock (3-18 months of age) . If you get a poor response from drenching, it may be yersiniosis.
Yersiniosis is invariably triggered by a combination of contaminated paddocks, cold, wet and windy weather and stress associated with nutrition, worms and/or weaning, yarding, shearing etc. Prevention involves uncontaminated paddocks (not easy this time of year and especially difficult while it is so wet out there) and good nutrition. But other contributing factors can be managed more easily. Maintain good nutrition, keep on top of the worms and coccidia and also, if you have to yard your animals off feed, do so for the shortest time possible.
Yersiniosis usually responds well to antibiotic treatment. Unfortunately the disease tends to roll sequentially through a mob so that treatment is often not practical for large numbers. So, if you see ill thrift and/or diarrhoea in your sheep or goats and you get a poor response from a drench, you should contact your vet.
It is possible for a human to become infected with yersiniosis, but practising good hygiene when handling livestock should avoid that problem.
If you are a relatively new sheep and goat owner, I encourage you to visit and bookmark the Wormboss website. It has a lot of very useful information for both experienced and novice sheep and goat owners, including some minivids about how to count worm eggs. They even have an online song about internal parasites in sheep!