Differentiating Major Causes of Piglet Diarrhoea: Practical Diagnostic Clues for Accurate Field Diagnosis

Piglet diarrhoea is one of the most frequently encountered clinical problems in swine practice, but determining its underlying cause can be challenging because bacterial, viral, and parasitic pathogens often produce similar clinical signs. An accurate diagnosis relies on evaluating the age of affected piglets, herd history, clinical presentation, pathological findings, and laboratory investigations together rather than depending on a single observation¹. Recognising disease-specific patterns allows veterinarians to prioritise differential diagnoses and select the most appropriate confirmatory tests. 

Age of Onset Can Guide the Initial Diagnosis 

Knowing when diarrhoea develops is often the first step in narrowing the list of possible causes. 

• Enterotoxigenic Escherichia coli (ETEC): Commonly affects piglets during the first four days of life. Post-weaning diarrhoea usually develops two to three weeks after weaning^1,2. 

• Clostridium perfringens type C: Most commonly affects piglets within the first three days of life but may occur up to three weeks of age^1,3,4. 

• Clostridioides difficile: Disease is typically seen in piglets between one and seven days old⁵. 

• Coccidiosis (Cystoisospora suis): Usually develops during the second week of life¹. 

• Rotavirus: Field outbreaks are more common in pigs between two and six weeks of age, although neonatal piglets can also be affected¹. 

• Porcine enteric coronaviruses (PECs): Pigs of all ages are susceptible, but neonatal piglets are at greatest risk because of immature intestinal function, slower enterocyte replacement, and an underdeveloped immune system¹. 

Clinical Signs Help Differentiate Common Enteric Diseases 

Although diarrhoea is the hallmark clinical sign, accompanying findings often provide valuable diagnostic clues. 

Neonatal colibacillosis (ETEC)¹ 

• Watery to creamy white or yellow diarrhoea 

• Depression and reduced appetite 

• Dehydration with sunken eyes in severe cases 

• Rough, wet hair coat 

• Rapid deterioration, with death possible within 12–24 hours after diarrhoea begins 

Clostridium perfringens type C^1,3,4 

• Haemorrhagic diarrhoea 

• Weakness and hypothermia 

• Severe dehydration 

• Sudden death in acute cases 

• Chronic cases may develop non-haemorrhagic mucoid diarrhoea, poor growth, and emaciation 

Clostridioides difficile⁵ 

• Early diarrhoea 

• Mild abdominal distension 

• Scrotal oedema 

• Sudden death 

• Some affected piglets may have normal faeces or even constipation 

Coccidiosis¹ 

• Yellowish-grey pasty faeces that become more fluid as disease progresses 

• Reduced weight gain 

• Variable severity among piglets within the same litter 

• Clinical disease may occur alongside asymptomatic animals 

Rotavirosis^1,6 

• Profuse yellow-white watery diarrhoea containing undigested milk 

• Vomiting 

• Lethargy and anorexia 

• Rapid weight loss and poor average daily gain 

Porcine enteric coronaviruses^1,7,8 

• Severe watery diarrhoea 

• Vomiting 

• Dehydration due to malabsorption 

• Highest mortality occurs in neonatal piglets 

Pathological Findings Strengthen the Diagnosis¹ 

Gross and microscopic lesions help distinguish diseases that present with similar clinical signs. 

• ETEC: Dilated stomach containing clotted milk or feed, hyperaemic small intestine, enlarged mesenteric lymph nodes, and bacterial adherence to intestinal epithelium with mild villous atrophy. 

• C. perfringens type C: Segmental necro-haemorrhagic or fibrino-necrotic enteritis is highly suggestive. 

• C. difficile: Marked oedema of the mesocolon is the characteristic gross lesion, while histopathology may reveal the characteristic "volcano lesion". 

• Coccidiosis: Non-haemorrhagic enteritis involving the jejunum and ileum, villous atrophy, villous fusion, crypt hyperplasia, and necrotic enteritis.. 

• Rotavirus and PECs: Villous atrophy, reduced villous-to-crypt ratio, and crypt hyperplasia are common findings, making laboratory confirmation essential for differentiation. 

Laboratory Confirmation Remains Essential¹ 

Because multiple pathogens can produce similar lesions, laboratory testing should always complement clinical and pathological findings. Depending on the suspected disease, diagnostic confirmation may involve: 

• Bacteriology 

• PCR or RT-PCR 

• RT-qPCR 

• Histopathology 

• Immunohistochemistry 

• Antigen detection assays 

• Toxin detection 

• Faecal flotation and oocyst quantification for coccidiosis 

Clinical Pearl 

Piglet diarrhoea should always be investigated as a syndrome rather than a single disease. Age of onset, clinical presentation, pathological findings, and appropriate laboratory testing together provide the most reliable pathway to differentiating bacterial, viral, and parasitic enteric diseases. Integrating these diagnostic clues improves confidence in case investigation and supports more informed herd-level decision-making while reducing the risk of misdiagnosis. 

References 

1. Luppi A, D’Annunzio G, Torreggiani C, Martelli P. Diagnostic approach to enteric disorders in pigs. Animals. 2023 Jan 18;13(3):338. https://www.mdpi.com/2076-2615/13/3/338 

2. Luppi A. Swine enteric colibacillosis: diagnosis, therapy and antimicrobial resistance. Porcine health management. 2017 Aug 8;3(1):16. https://link.springer.com/content/pdf/10.1186/s40813-017-0063-4.pdf 

3. Uzal FA, Songer JG. Clostridial diseases. Diseases of swine. 2019 Jun 3:792-806. https://www.academia.edu/download/60674736/Diseases_of_Swine__11th_Edition_VetBooks.ir20190922-31639-a6z8g5.pdf#page=816 

4. Posthaus H, Kittl S, Tarek B, Bruggisser J. Clostridium perfringens type C necrotic enteritis in pigs: diagnosis, pathogenesis, and prevention. Journal of veterinary diagnostic investigation. 2020 Mar;32(2):203-12. https://journals.sagepub.com/doi/pdf/10.1177/1040638719900180 

5. Weese JS. Clostridium (Clostridioides) difficile in animals. Journal of veterinary diagnostic investigation. 2020 Mar;32(2):213-21. https://journals.sagepub.com/doi/pdf/10.1177/1040638719899081 

6. Shepherd FK, Freeman MJ, Culhane MR, Marthaler DG. Reoviruses (rotaviruses and reoviruses). Diseases of swine. 2019 Jun 3:715-27. https://www.academia.edu/download/60674736/Diseases_of_Swine__11th_Edition_VetBooks.ir20190922-31639-a6z8g5.pdf#page=739 

7. FENNER F, BACHMANN PA, GIBBS EP, MURPHY FA, STUDDERT MJ, WHITE DO. Coronaviridae. Veterinary Virology. 2014 Jun 27:505. https://pmc.ncbi.nlm.nih.gov/articles/PMC7149976/pdf/main.pdf 

8. Chen F, Knutson TP, Rossow S, Saif LJ, Marthaler DG. Decline of transmissible gastroenteritis virus and its complex evolutionary relationship with porcine respiratory coronavirus in the United States. Scientific reports. 2019 Mar 8;9(1):3953. https://www.nature.com/articles/s41598-019-40564-z.pdf