Daniela Denk

Rapid, practical diagnostic approaches are essential for effective fish health management, yet cytological wet mount assessment of internal organs remains underused and inconsistently described in peer‐reviewed aquatic veterinary literature. Organ wet mount (squash preparation) cytology offers a simple, low‐cost method for immediate evaluation of fresh tissues. Unlike impression smears and aspirates, in which cells are assessed largely in isolation, squash preparations retain structural relationships within the tissue, providing tissue‐level information at the point of examination that would otherwise await histopathology. The technique is widely applicable and requires minimal equipment, but guidance on its application beyond gill, skin, and fin samples is limited. A survey of fish health professionals confirmed that internal organ preparations are used less than external wet mounts. This review outlines the use of organ squash preparations during fish necropsy, emphasising technique, interpretation, and recognition of common findings rather than a comprehensive overview of disease. Key limitations, such as post‐mortem changes, are discussed, as is the role of targeted special stains and follow‐up diagnostics. Greater awareness and more consistent use of organ squash cytology have the potential to improve early detection of disease and support more targeted diagnostic decision‐making in fish health investigations.

Rapid and accurate diagnosis of infectious diseases in aquaculture is essential for preventing major economic and ecological losses. Traditional culture-based methods focus on isolation of individual pathogens, and often are burdened with extended processing times, particularly during investigations of polymicrobial infections. Application of Oxford Nanopore Technologies (ONT) sequencing offers a rapid, culture-independent workflow for the identification of bacterial and fungal pathogens directly from fish tissues. Swab and organ samples from four cases (1: Salmo spp.; 2: Cyprinus carpio; 3: Salvelinus fontinalis; 4: Heniochus acuminatus) were analyzed using ONT long-read sequencing for metagenomic screening and bioinformatic classification. The results revealed case-, species-, and tissue-specific microbial profiles, with external tissues showing higher microbial diversity and internal organs enriched in pathogenic taxa. Dominant pathogens included Streptococcus iniae, Aeromonas hydrophila, Pseudomonas spp., and Saprolegnia parasitica, alongside opportunistic zoonotic bacteria such as Escherichia coli and Acinetobacter baumannii. We demonstrate the potential for diagnostic application of ONT sequencing in investigations and detection of multi-pathogen infections, including assessments of microbial community structure changes during disease outbreaks in aquatic species. The presented workflow enables rapid, cost-effective, and comprehensive pathogen profiling, supporting early disease surveillance and improved management in aquatic veterinary practice.

The European Society of Veterinary Pathology (ESVP) and the European College of Veterinary Pathologists (ECVP) DEI Task Force (DEITF) was established to assess and advance diversity, equity, and inclusion (DEI) initiatives within the European veterinary pathology community. To gain a baseline understanding of DEI challenges and perceptions, an online survey was conducted in March 2024. 208 responses were collected and analyzed alongside feedback from interactive DEI sessions at the annual congress (2024, San Lorenzo de El Escorial, Spain). The results indicated a predominantly female respondent group (66%), an overrepresentation of experienced pathologists (58.7%), and limited ethnic diversity, with 85.6% identifying as White/Caucasian. Key DEI challenges included workplace discrimination, financial disparities in residency programs, language barriers for non‐native English speakers, limited neurodiversity accommodations, and a lack of LGBTQIA+ inclusivity. In response, the DEITF has developed a comprehensive set of recommendations outlining actionable strategies for ESVP/ECVP, training centers, and event organizers. These efforts focus on gender identity recognition, neurodiversity and accessibility, and residency experience improvements. Additionally, the DEITF is committed to implementing regular DEI‐focused education, workshops, and policy recommendations. Future goals include the development of mentorship programs, the implementation of recommendations for equitable accessibility to professional opportunities, the establishment of DEI‐focused scholarships, the integration of inclusive curricula, and advocacy for structural changes within training centers and professional societies to promote standardized policies supporting underrepresented groups. The DEITF actively welcomes collaboration and input from other DEI‐focused groups within the field, emphasizing the importance of proactive engagement in fostering a more inclusive, diverse, and supportive veterinary pathology profession.

Polyglucosan bodies are accumulations of insoluble glucose polymers and proteins that form intracytoplasmic inclusions in the brain, large numbers of which can be indicative of neurodegenerative diseases such as Lafora disease. Montserrat orioles ( Icterus oberi ) are an icterid passerine endemic to Montserrat with conservation populations maintained in captivity abroad. We demonstrate that polyglucosan bodies are unusually abundant in the cerebellar molecular and Purkinje cell layers and cerebellar peduncles of captive-bred and wild-caught Montserrat orioles. The bodies are periodic acid-Schiff positive and diastase resistant and label with concanavalin A and for ubiquitin, consistent with those seen in humans. We found no association of the polyglucosan bodies with concurrent neurological lesions or clinical signs, nor with EPM2 A and EPM2B gene mutations associated with Lafora disease. We conclude that an abundance of cerebellar polyglucosan bodies may be a normal finding in aged Montserrat orioles and not a threat to the captive breeding population.

The count of mitotic figures (MFs) observed in hematoxylin and eosin (H&E)-stained slides is an important prognostic marker as it is a measure for tumor cell proliferation. However, the identification of MFs has a known low inter-rater agreement. Deep learning algorithms can standardize this task, but they require large amounts of annotated data for training and validation. Furthermore, label noise introduced during the annotation process may impede the algorithm's performance. Unlike H&E, the mitosis-specific antibody phospho-histone H3 (PHH3) specifically highlights MFs. Counting MFs on slides stained against PHH3 leads to higher agreement among raters and has therefore recently been used as a ground truth for the annotation of MFs in H&E. However, as PHH3 facilitates the recognition of cells indistinguishable from H&E stain alone, the use of this ground truth could potentially introduce noise into the H&E-related dataset, impacting model performance. This study analyzes the impact of PHH3-assisted MF annotation on inter-rater reliability and object level agreement through an extensive multi-rater experiment. We found that the annotators' object-level agreement increased when using PHH3-assisted labeling. Subsequently, MF detectors were evaluated on the resulting datasets to investigate the influence of PHH3-assisted labeling on the models' performance. Additionally, a novel dual-stain MF detector was developed to investigate the interpretation-shift of PHH3-assisted labels used in H&E, which clearly outperformed single-stain detectors. However, the PHH3-assisted labels did not have a positive effect on solely H&E-based models. The high performance of our dual-input detector reveals an information mismatch between the H&E and PHH3-stained images as the cause of this effect.

Background: Oral cavity squamous cell carcinomas (OCSCCs) are relatively common in multiple non‐human primate species but are poorly documented in Goeldi's monkeys.Methods: Four Goeldi's monkeys with OCSCC, from three zoological collections, underwent necropsy with cytology, histopathology, immunohistochemistry, and pan‐herpesvirus PCR analysis.Results: All animals were euthanised and exhibited poor‐to‐emaciated body condition. Three OCSCCs arose from the maxillary oral mucosa and a single OCSCC was primarily mandibular, with bone invasion evident in three cases. Histologically, one OCSCC in situ was diagnosed, whilst the rest were typically invasive OCSCCs. Neoplastic cells were immunopositive for pancytokeratin and E‐cadherin. All examined cases were negative for regional lymph node (RLN) and/or distant metastases, cyclooxygenase‐2 (COX‐2) immunoexpression, and panherpesvirus PCR expression.Conclusions: OCSCCs in Goeldi's monkeys may be deeply invasive, but not readily metastatic. No herpesvirus‐association or COX‐2 expression was evident; the latter suggesting that NSAIDs are unlikely to be a viable chemotherapeutic treatment.