Adapted faecal clinical scoring systems for post-weaning diarrhea due to enterotoxigenic Escherichia coli and swine dysentery due to Brachyspira hyodysenteriae
Authors: Vangroenweghe Frédéric , Hammer James 
Published: November 2024

Swine production globally still has major challenges with swine intestinal disease, which might be provoked by post-weaning diarrhea or growing pig diarrhea. The major etiological agent of post-weaning diarrhea is enterotoxigenic Escherichia coli, characterized by the presence of both fimbriae (adhesins; mainly F4 (previously known as K88) and F18) and the presence of enterotoxins (thermostable toxin a and b; thermolabile toxin). Piglets affected with post-weaning diarrhea have mild to severe watery diarrhea, dehydration, and retarded growth which may lead to mortality. In contrast, growing pig diarrhea has, besides several viral and parasitic causes, three major bacterial causes, namely Lawsonia intracellularis, Brachyspira species or Salmonella species. Swine dysentery is provoked by Brachyspira hyodysenteriae and leads to mild to severe diarrhea which can be associated with addition of mucus, fibrin, necrotic material, or blood into the faeces. Ileitis caused by Lawsonia intracellularis causes mild to severe diarrhea with or without melena. Depending on the clinical presentation, low mortality with sudden death may be observed. In contrast, Salmonella is ubiquitous and clinical signs may be different depending on serotype or caused by dysbiosis. Both under field and experimental conditions, the assessment of severity of swine intestinal disease remains a challenge. Many studies only report presence or absence of diarrhea without further differentiation of specific severity ranging from mild to severe faecal appearance. Therefore, a need for standardized scoring to evaluate and analyze results of treatment and prevention is crucial. Based on three published field studies, we discuss the importance of a standardized faecal clinical scoring system adapted to a specific pathogenic challenge, namely enterotoxigenic Escherichia coli or Brachyspira hyodysenteriae. For enterotoxigenic Escherichia coli, a post-weaning diarrhea faecal clinical scoring based on a score grid from 0 to 4 is applied, to differentiate between normal, pasty, mild, moderate, and severe diarrhea. For Brachyspira hyodysenteriae, Lawsonia intracellularis and Salmonella species a more differentiated approach is necessary considering the different possible faecal additions (mucus, blood, fibrin, necrotic material). The swine dysentery faecal clinical scoring system, therefore, includes 3 sub criteria shape-consistency, colour, and additions, which are scored separately and subsequently combined into a total faecal score. Using both scoring systems, several statistical analyses can be performed ranging from kinetics over time, area under the curve, days to maximum score, and in case of individual piglet faecal clinical scoring number of piglets with diarrhea on a particular observation day can be assessed. These analyses are used to compare different intervention strategies in 3 field experiments. They are vaccination against enterotoxigenic Escherichia coli using an oral live avirulent Escherichia coli F4/F18 vaccine in the prevention of post-weaning diarrhea due to enterotoxigenic Escherichia coli, inclusion of a β-mannanase enzyme to degrade β-mannans in the diet, and therapeutic treatment with an oral Zn-chelate product to treat clinical signs of swine dysentery. In conclusion, adapted faecal clinical scoring systems for different swine intestinal diseases or phases of production can be an important tool in both field and experimental studies to objectively assess the severity of swine intestinal disease and make an evidence-based evaluation of clinical effects following therapeutic or preventive interventions.