Post-Weaning Diarrhea in Piglets: Clinical Recognition and Diagnostic Approaches

Post-weaning diarrhea (PWD) remains a frequent challenge in pig production, particularly during the early period after weaning when piglets experience significant nutritional, environmental, and physiological changes. Because multiple factors contribute to disease development, successful control begins with early recognition of clinical signs and establishing an accurate diagnosis before implementing corrective measures. 

A structured approach combining clinical evaluation, disease history, and appropriate laboratory testing helps veterinarians distinguish PWD from other enteric disorders and supports more targeted herd health interventions. 

Recognizing Clinical Presentation of Post-Weaning Diarrhea 

PWD commonly develops soon after weaning. During this vulnerable period, careful monitoring of recently weaned groups is important for early identification of affected piglets. 

Clinical evaluation should focus on key indicators such as: 

• Watery diarrhea

• Dehydration

• Reduced feed intake

• Reduced growth performance

In severe situations where enterotoxigenic Escherichia coli (ETEC) plays a major role, diarrhea outbreaks can result in significant morbidity and mortality, emphasizing the importance of early diagnosis and intervention¹. 

Building an Accurate Diagnosis 

Diagnosis begins with recognition of clinical signs and interpretation of these findings along with disease history and recent changes affecting the piglets. Since PWD may share clinical similarities with other enteric disorders, confirmation through laboratory investigation is important. 

Confirmation of PWD may involve isolation of Escherichia coli from fecal samples followed by identification of enterotoxigenic strains using primers targeting heat-labile (LT) and heat-stable (ST) toxin genes². 

Role of Molecular Diagnostics in PWD Identification 

Molecular diagnostic methods have expanded the ability to characterize PWD-associated pathogens. Multiplex PCR enables simultaneous detection of important fimbrial genes such as F4 and F18 together with toxin genes including STa, STb, and LT^1,3.

Additional laboratory approaches include bacteriological culture, MALDI-TOF identification, whole-genome sequencing, and high-throughput real-time PCR for quantifying fimbrial gene copies⁴. 

These diagnostic tools allow more detailed identification of pathogen characteristics and support a clearer understanding of the infectious agents involved in diarrhea cases. 

Considering Other Enteric Pathogens 

Although ETEC is considered a major pathogen associated with PWD, diagnostic evaluation should also consider other possible contributors. Rotavirus type A has shown a significant association with diarrhea when molecular testing is incorporated into diagnostic investigations¹. 

A broader diagnostic approach helps veterinarians avoid focusing on a single pathogen and supports more accurate interpretation of disease patterns within affected piglets. 

Practical Clinical Insights 

For practicing veterinarians, accurate diagnosis of PWD requires combining clinical findings with laboratory confirmation rather than relying on a single assessment method. 

Visual evaluation of feces, fecal consistency scoring, dry matter estimation, fecal pH, and soiling scores can provide supportive diagnostic information; however, these parameters have recognised limitations and variable sensitivity and specificity. 

During herd investigations, veterinarians should interpret clinical observations alongside laboratory findings to improve diagnostic confidence. Identifying the pathogens involved and understanding the clinical presentation provide a stronger foundation for developing targeted control strategies and improving piglet health outcomes. 

References 

1. Iribagiza A, Nimbona C, Hanyurwumutima E, Mvuyekure E, Hakizimana E, Nzeyimana MC, Irakoze S. Post-Weaning Diarrhea in Piglets: Causes, Risk Factors, and Management Strategies. Open Journal of Animal Sciences. 2025 Oct 29;15:369-81. https://hal.science/hal-05512666/document 

2. Nuntapaitoon M, Tummaruk P. Factors influencing piglet pre-weaning mortality in 47 commercial swine herds in Thailand. Tropical animal health and production. 2018 Jan;50(1):129-35. https://www.academia.edu/download/87732622/s11250-017-1412-720220619-1-ula9iv.pdf 

3. Zhang C, Li S, Upadhyay I, Vakamalla SS, Lauder KL, Hansen C, Massey KA, Hayes C, Herndon NL, Zhang W. Heterologous prime-boost immunization of two-component vaccine candidate PWDVax protected pigs against F18 enterotoxigenic Escherichia coli post-weaning diarrhea. Infection and immunity. 2025 Apr 8;93(4):e00406-24. https://journals.asm.org/doi/pdf/10.1128/iai.00406-24 

4. Eriksen EØ, Kudirkiene E, Barington K, Goecke NB, Blirup-Plum SA, Nielsen JP, Olsen JE, Jensen HE, Pankoke K, Larsen LE, Liu G. An observational field study of porcine post-weaning diarrhea: clinical and microbiological findings, and fecal pH-measurements as a potential diagnostic tool. Porcine Health Management. 2023 Jul 11;9(1):33. https://link.springer.com/content/pdf/10.1186/s40813-023-00325-x.pdf