Porcine circovirus type 3 (PCV3) has been recently described as a potential cause of abortions and systemic vasculitis in pigs. Although the virus has been detected by real-time PCR in several porcine tissues from countries worldwide, PCV3-associated diseases have not been satisfactorily clarified. The objective of this study was to investigate the association between the presence of PCV3 mRNA detected by in situ hybridization (ISH) within histological lesions and PCV3 DNA detected by real-time PCR in naturally infected pigs. A total of 25 PCV3 PCR-positive cases were analyzed. Formalin-fixed tissues from these cases were evaluated for histologic lesions and for ISH-RNA positive signals for PCV3. The most frequent tissue type with histopathologic lesions was heart, 76.2%, with lymphoplasmacytic myocarditis and epicarditis as the most frequent lesions observed. Lymphoplasmacytic interstitial pneumonia was also a frequent finding, 47.6%. There were also lesions in kidney, liver, spleen and lymph nodes. PCV3-ISH-RNA positive signals were mostly observed in association with lymphoplasmacytic inflammatory infiltrate in various tissues, including arteries. Based on our results, the minimum set of specimens to be submitted for histopathology and mRNA in situ hybridization to confirm or exclude a diagnosis of PCV3 are heart, lung and lymphoid tissues (i.e., spleen and lymph nodes), especially for differential diagnosis related with PCV2-associated diseases.

Porcine reproductive and respiratory syndrome virus (PRRSV) remains a major concern for swine health. Isolating PRRSV is essential for identifying infectious viruses and for vaccine formulation. This study evaluated the potential of using tongue fluid (TF) from perinatal piglet mortalities for PRRSV isolation. Four collection protocols were tested: extracting TF from fresh tissues using phosphate-buffered saline (PBS group), extracting TF from fresh tissues using virus transportation medium (VTM group), extracting TF from freeze-thawed tissue (freeze-thaw group), and using tissue homogenates (homogenate group). Two cell lines (ZMAC and MARC-145) and primary alveolar macrophages (PAM) were evaluated for their effect on successful PRRSV isolation. An eligible PRRSV-positive unstable breeding herd in Midwestern USA was chosen for the study. Tongues were collected in 20 batches (~30 mortalities per batch). Within each batch, each tongue tissue was cut into four quarters, with each quarter randomly assigned to one of the four collection protocols and RT-qPCR tested. Virus isolation (VI) was attempted on 10 batches. The mean RT-qPCR cycle threshold (Ct) values for the PBS, VTM, freeze-thaw, and homogenate groups were 21.9, 21.8, 22.6, and 24.8, respectively. The VI success rate was 22.6%, 12.1%, 2.8%, and 2.8% in the PBS, VTM, freeze-thaw, and homogenate groups, respectively. The probability of successful VI was 3.1% and 21.0% in the MARC-145 and ZMAC cell lines, respectively, and 4.8% in the PAM cells. TF from perinatal mortalities is an option for PRRS VI, aiding in PRRSV monitoring and control programs.

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Escherichia coli –associated diseases continue to be a significant concern in swine health. Disease may occur when E. coli strains harbor specific virulence factors. The combination of virulence factors detected in a single isolate forms a virotype, which can be grouped into pathotypes based on mechanisms of pathogenicity. This study compiled E. coli polymerase chain reaction (PCR) sample‐level data from six major U.S. veterinary diagnostic laboratories (VDLs) to evaluate trends in E. coli virulence factors, virotypes, and pathotypes from porcine cases. The dataset contained diagnostic results for E. coli virulence factors detected by PCR, including attachment genes (fimbriae and adhesins) and toxin genes (heat‐labile, heat‐stable, and Shiga‐like toxins). Between 2008 and 2025, major shifts were observed in the detection of key E. coli virulence factors. Temporal trend analysis using the Mann–Kendall test showed increasing detection of the virulence factors F18, F41, STa, Stx2, and Stx2e, while F4, AIDA, Paa, and EAST1 decreased over time. Similar patterns were observed among isolates classified as potentially pathogenic, with increases in F18, F41, STa, Stx2, and Stx2e and decreases in F4, AIDA, Paa, and EAST1 detection. Among pathotypes, Hybrid enterotoxigenic E. coli (ETEC)/STEC had an increase in detection over time, whereas ETEC, STEC, and isolates classified as not potentially pathogenic decreased. This large‐scale diagnostic dataset reveals a notable shift in the E. coli pathogenic profile in swine over the past decade, characterized by an increasing detection of the hybrid ETEC/STEC pathotype and evolving virotype compositions.