We have received several lamb and calf cases recently with post mortem samples from animals with diarrhoea. Here are some recommendations to ensure you get the most out of your cases, especially when sacrificing an animal for histological sampling of the gut.
1. Immerse your samples of gut into formalin as soon as possible – within minutes, especially in a sacrificed animal. Make sure the formalin bathes the mucosa. Long tubes of gut without contact with formalin will keep autolysing. We want the autolysis process to be arrested immediately.
2. Sample throughout the GI tract – take large intestine, small intestine, abomasum, and forestomach.
3. For abomasum take your samples from the body of the stomach, not the pylorus. We can’t assess for metaplastic change due to parasites in the abomasum if the sample is from the pylorus.
4. Take multiple samples of small or large intestine. Lesions of some diseases can be multifocal and a single piece of small intestine may miss lesions of yersiniosis, for example. How do we know? We often see cases of yersiniosis where multiple samples of small or large intestine have been taken and some of those samples do not have characteristic lesions.