Streptococcus suis (S. suis) expresses a specific immunoglobulin M (IgM) protease, designated IdeSsuis. Vaccination with recombinant IdeSsuis elicits protection against S. suis serotype 2. This study was initiated by the finding that the isogenic deletion mutant ΔideSsuis shows a hypervirulent phenotype in 4-week-old piglets, presumably in association with maternally derived antibodies against IdeSsuis. This prompted us to conduct a field study to test the working hypothesis that maternal αIdeSsuis IgG antibodies are biologically relevant. Investigations in one herd with autogenous S. suis vaccination pre-farrowing showed a significant correlation of IgG levels against IdeSsuis in serum of 2-week-old-piglets and levels in colostrum. These antibody levels declined over the subsequent weeks of life. Levels of IgM binding to S. suis in sera of 2-week-old piglets did not correlate with respective levels in colostrum but with the amount of colostrum taken up. Bactericidal assays with wild type (wt) and ideSsuis mutants demonstrated that expression of functional or nonfunctional full-length IdeSsuis results in increased killing of S. suis serotype 2 in the blood of 2-week-old piglets. This phenotype disappeared as piglets aged. Linear mixed-effects models confirmed that serum IgG against IdeSsuis exerts a significant, time-independent effect on survival of S. suis wt and ∇ideSsuis_C195S, expressing a nonfunctional variant of IdeSsuis, but not ΔideSsuis. Furthermore, IgM binding to S. suis wt influenced survival of wt and ∇ideSsuis_C195S in a time-dependent manner. This is in line with the concept that αIdeSsuis IgG are protective through induction of fragment crystallizable (Fc)-mediated opsonophagocytosis rather than neutralization of the IgM protease, at least in suckling piglets.

Phocine herpesvirus-1 (PhHV-1) can cause acute pneumonia and hepatitis with high morbidity and frequently fatal outcomes in young harbour seals (Phoca vitulina) and, occasionally, in grey seals (Halichoerus grypus). Here, we report the virological and pathomorphological findings of a PhHV-1 infection in 10 out of 90 investigated young harbour seals, collected between January 2020 and December 2021 from the Dutch North Sea coast, found either dead or suffering from severe respiratory distress resulting in euthanasia. Macroscopic findings included poor nutritional condition, poorly deflated and slightly consolidated lungs, as well as a friable and pale liver parenchyma. Moreover, six seals showed several co-morbidities such as septicaemia, pancreatitis and pneumothorax. Microscopic investigation revealed predominantly a non-suppurative peribronchitis and necrotizing bronchitis. Multifocal to coalescing necrotizing hepatitis and non-suppurative inflammation of the liver were the most striking lesions. Eosinophilic intranuclear inclusion bodies were seen in bronchial epithelial cells and hepatocytes in three and six cases, respectively. Using a monoclonal anti-PhHV-1 glycoprotein B antibody, viral antigen was detected in situ, specifically intra- and perilesional, in the lung and/or liver of eight seals. Electron microscopy of two selected cases demonstrated numerous intranuclear viral capsids and, within the cytoplasm, enveloped mature virions. A pan-Herpesviridae polymerase chain reaction using a degenerative primer set was used to confirm PhHV-1 infection. Genome fragments were detected in lung and liver samples. Collectively, these data indicate that PhHV-1 infection was the most likely cause of disease in these 10 animals, although several co-morbidities were also present. This indicates that monitoring of PhHV-1 infection status in harbour seals, especially juvenile animals, is an integral part of population health surveillance of susceptible phocid populations.

Diarrheal disease caused by Bacillus cereus is driven by pore-forming enterotoxins, with hemolysin BL (Hbl) and non-hemolytic enterotoxin (Nhe) as major virulence factors. Toxin structure and mode of action are well described, while especially human intestinal epithelial responses remain incompletely characterized. With the co-culture system of Caco-2 and mucus-producing HT29-MTX cells (9:1), this study describes a suitable model for investigating enterotoxin effects. Cell line-, dose- and enterotoxin-dependent changes in cell viability were detected. Undifferentiated Caco-2 generally showed higher susceptibility than HT29-MTX cells. Twenty-four-hour co-cultures were more susceptible than 28-day co-cultures but displayed partial recovery after toxin removal. Enterotoxin exposure caused a time-dependent decline in transepithelial electrical resistance, consistent with barrier dysfunction. In Ussing chamber experiments, enterotoxin-containing supernatants, especially Nhe+Hbl, increased short-circuit currents, indicating altered electrogenic ion transport consistent with pro-secretory phenotypes relevant to diarrhea. Transcriptome analyses demonstrated a pronounced time- and dose-dependent response toward Nhe+Hbl. Two-hour sublethal enterotoxin exposure elicited few transcriptional changes, whereas lethal enterotoxin exposure rapidly suppressed proliferation- and cell-cycle-associated programs. Pathway analyses consistently highlighted TNFα/NF-κB-driven inflammation, MAPK-associated stress signaling, and p53/apoptosis pathways; metabolic remodeling and senescence-/autophagy-related processes became more apparent at longer exposure (8 h) and/or higher toxin levels. Dose-dependent caspase-3/7 activation, LDH release, and minimal caspase-1 activation were also consistent with early inflammatory response, apoptotic cell death and membrane damage. Collectively, this study integrates barrier function, ion transport, cell viability, and transcriptomics to define host intestine epithelial response programs triggered by B. cereus enterotoxins and to connect toxin exposure to barrier dysfunction and diarrheal pathophysiology.

Human noroviruses (HuNoV) are the most common cause of viral gastroenteritis worldwide, causing sporadic cases and outbreaks. Noroviruses that infect wild and domestic animals, including pigs and dogs, are genetically related to human noroviruses, increasing the potential for cross-species transmission. To investigate the potential of noroviruses to cross the species barrier, we used porcine, canine, and avian precision-cut intestinal slices. We show that human norovirus virus-like particles (VLPs) bind to pig and dog intestinal tissue and are taken up with a similar efficiency as the porcine and canine noroviruses, respectively. In contrast, no binding or internalization of human, porcine, or canine noroviruses was detected in chicken tissue. We further showed that human norovirus replicates in pig intestinal tissue. In contrast, while animal noroviruses attached to human intestinal cells, intracellular uptake was limited. This suggests that human-to-animal transmission is more likely than animal-to-human transmission and that viral uptake likely presents a species barrier.

Congenital deformities of the tibia are rare conditions in animals as well as in humans. The cause is often unknown. Although congenital defects in South American Camelids are more frequent than in other species, to our knowledge, there are no previous reports of congenital tibia deformities in alpacas (Vicugna pacos). Both unrelated presented crias showed a caudal curvature of the tibial diaphysis of either one or both legs soon after birth. Radiographs revealed a focal circumferential endosteal and intramedullary, increased mineralization in the curvature area of the diaphysis of one or both legs. One cria suffered a spontaneous fracture in this area. A histological examination, which was carried out only on the second cria, identified a circumscribed osteosclerosis in the affected region. Descriptions of tibial deformities in various animal species and in humans show similarities but do not fully correspond to the changes we observed in the crias. Whether the described congenital deformities are of hereditary origin can only be clarified through further future investigations.

Live trapping is a common method in wildlife research and management, yet it poses inherent risks to animal welfare. This study systematically evaluated injury incidence and severity in coypus (Myocastor coypus) and raccoons (Procyon lotor) captured using three commercially available live trap types: a standard wooden box trap (WBT), a metallic, sheet metal trap (SMT), and a wire grid trap (WGT). A total of 55 coypus and 45 raccoons were examined following a trap confinement duration of a maximum of six hours. Injuries were assessed using standardized necropsy protocols and categorized by anatomical location, severity, and presumed cause. Results showed species-specific injury patterns, with raccoons exhibiting more frequent and severe injuries than coypus. Raccoons primarily sustained skin lesions and dental trauma, consistent with their manipulative, escape-oriented behavior, while coypu injuries were predominantly localized to the snout and incisors. Although not statistically significant, trap design influenced injury profiles: the WBT was associated with severe injuries in raccoons, particularly to the forelimbs and dentition, while the WGT prompted intense escape behaviors without a proportional increase in trauma. The SMT resulted in fewer external injuries but did present species-specific risks, such as claw-abrasion and tail entrapment. Approximately 93% of raccoons and 55% of coypus exhibited external injuries, including 14 severe cases and 5 confirmed fractures. These findings underscore the importance of species-specific trap assessment and design optimization to mitigate animal suffering. Given the limitations of traditional injury scoring systems and behavioral indicators when applied to wild animals, this study highlights the need for integrated, evidence-based welfare assessments in field settings. Future research should prioritize refinement of trapping methods and standardized welfare evaluation frameworks to support ethical and effective wildlife management.

Long-term persistent measles virus (MeV) infection of the central nervous system (CNS) can result in subacute sclerosing panencephalitis (SSPE), an invariably fatal late neurological complication of measles. Analogous SSPE-like chronic diseases have also been reported in adult dogs, cetaceans, and more recently harbor seals following infection by canine distemper virus (CDV), dolphin morbillivirus (DMV), and phocine distemper virus (PDV), respectively. Here, we characterize different animal morbilliviruses (CDVlynx, PDV2001, PDV2014, and DMV232-18) that persisted in the CNS of their respective host species for several years after the initial infections. The CDVlynx and DMV232-18 strains encode nonfunctional matrix proteins and hyperfusogenic fusion proteins which are hallmark features of SSPE MeV strains. The complex mutational profile apparent in the PDV2001 strain also has parallels with MeV strains from SSPE cases. In contrast, the PDV2014 strain encodes for a nonfunctional matrix protein but an unmodified F protein supporting the evolutionary precedence of M protein changes in facilitating long-term morbillivirus infections of the CNS. Consequently, our findings show that similar evolutionary pathways across different animal species drive morbilliviruses to evolve analogous mechanisms favoring virus persistence in the CNS and the development of chronic neurological disease. Such naturally occurring chronic animal morbillivirus infections of the CNS provide natural analogues for studying the evolutionary trajectory and molecular basis of the pathogenesis of SSPE in humans. This may pave the way for developing early diagnostics and intervention strategies.

Neoplasia in free ranging wildlife remains poorly documented, particularly in non-human primates. An adult free ranging female mantled howler monkey (Alouatta palliata) was found conscious but non-ambulatory on a country road in northwestern Costa Rica. Following admission to a wildlife rescue center, euthanasia was elected due to poor prognosis and body condition. At necropsy, three firm, gritty, white masses were identified on the inner surface of the parietal bones. Histopathologic examination revealed a well-circumscribed, moderately cellular, encapsulated neoplastic proliferation arising from the dura mater and compressing the cerebral cortex while sparing the leptomeninges. Neoplastic cells were arranged in whorls and occasional interlacing streams, with sporadic psammoma bodies. A diagnosis of transitional meningioma was made. Immunohistochemically, neoplastic cells were positive for S100 and negative for pan-cytokeratin, vimentin, and E-cadherin. Reports of meningiomas in non-human primates, particularly in free ranging individuals, are scarce. This case contributes to the limited knowledge of neoplasia in wildlife and underscores the value of documenting neoplasia in free ranging primates.

Mycobacterium avium is a slow-growing non-tuberculous mycobacterium. While its medical importance is increasing, its virulence is only poorly characterized. A highly virulent M. avium strain ATTC25291 (MAA25291) has been shown to cause severe disease in mice by survival and growth in nitric oxide (NO) producing, immune suppressive monocytic-MDSC (M-MDSC). The induction and persistence of MAA25291 in M-MDSC is still unresolved. In the present study, we were interested in the role of M-MDSC in mice infected with MAA25291 at infection doses that led to the manifestation of clinical disease (high dose) or subclinical disease (low dose). Flow cytometry revealed the presence of M-MDSC in both infection groups, however, this infiltration was significantly lower after low dose infection. Histopathology showed lower infiltration of NOS2 expressing cells in spleen and liver correlated with high CD3+ T cell numbers after low dose infection, whereas high dose infection of mice led to T cell losses in the tissues. This study highlights that the infection dose significantly affects M-MDSC induction and their immune regulatory roles. Furthermore, it suggests that the induction and persistence of MAA25291 in M-MDSC relies on the amount of NO production.

Flexural limb deformities are a widespread condition in foals. Oxytetracycline is a common conservative treatment option with relaxing effects on the muscle-tendon-unit, potentially mediated through a matrix-metalloproteinase (MMP)-inhibitor mechanism. Its high therapeutic dose for this indication, potential negative side effects, and the guidelines for prudent use of antimicrobials make investigating alternatives desirable. In this study, the influence of substances with potentially similar mechanisms of action, however without antimicrobial properties, on viability and proliferation of juvenile myofibroblasts was assessed in vitro. Myofibroblasts from forelimb superficial digital flexor tendons and accessory ligaments of the deep digital flexor tendon from 6 foals, euthanized for reasons unrelated to this study, were cultured and characterized. The myofibroblasts were incubated with oxytetracycline, the MMP-inhibitors incyclinide, ilomastat, aprotinin, pentoxifylline, the lathyrogenic agent β-aminopropionitrile fumarate and Dulbecco’s modified eagle medium as control. Colorimetric cell viability (MTS) and crystal violet assays assessed their viability and proliferation capacities. The morphology and immunohistochemistry profile of the cultured cells was consistent with tendon and ligament myofibroblasts. All test substances were biocompatible, shown by the absence of significant differences with cells incubated with medium, demonstrating the absence of cytotoxic or anti-proliferative effect on juvenile myofibroblasts in the tested concentrations in this preliminary study.

Respiratory viral infections continue to cause pandemic and epidemic outbreaks in humans and animals. Under steady-state conditions, alveolar macrophages (AlvMϕ) fulfill a multitude of tasks in order to maintain tissue homeostasis. Due to their anatomic localization within the deep lung, AlvMϕ are prone to detect and react to inhaled viruses and thus play a role in the early pathogenesis of several respiratory viral infections. Here, detection of viral pathogens causes diverse antiviral and proinflammatory reactions. This fact not only makes them promising research targets, but also suggests them as potential targets for therapeutic and prophylactic approaches. This review aims to give a comprehensive overview of the current knowledge about the role of AlvMϕ in respiratory viral infections of humans and animals.

Since the first emergence of the Bluetongue virus (BTV) in 2006 in Northern Europe, there has been a reported association between BTV Serotype 8 (BTV-8) and brain malformations in calves. The first BTV-3 outbreak in Germany was registered in October 2023. Since then, numbers have increased steadily. In a suckler cow herd in the Lower Saxony region, two Angus calves with clinical signs of diffuse encephalopathy, including ataxia, abnormal gait, and central blindness, were born in autumn 2024. Both calves were submitted for Magnetic Resonance Imaging (MRI) and pathological examination, revealing hydranencephaly and internal hydrocephalus, respectively. BTV-3 was detected in blood and tissue samples of both calves using BTV-specific real-time PCR. The presented findings demonstrate that there seems to be an association between transplacental BTV-3 infections and congenital malformations in calves, as previously reported for BTV-8 and -10.

Canine distemper virus (CDV, species Morbillivirus canis) is a highly contagious pathogen with a broad host range among carnivores. In common with measles virus, alveolar macrophages (AMs) are among the first target cells of infection in the respiratory tract. Therefore, in vitro infections of primary canine AMs were performed with the attenuated Onderstepoort (Ond) and field R252 strain of CDV over a period of 6 days. This showed that AMs are permissive to CDV infection and that such infections are productive with respect to the release of new virus particles. Phenotypic differences were observed over the entire course of the experiment, as higher levels of infection and virus production were observed in CDV R252-infected AMs, while infection with CDV Ond resulted in more prominent cytopathic effects, including syncytium formation. Transcriptome analyses of samples from 1 day post-infection via total RNA sequencing demonstrated further marked differences with respect to the pro-inflammatory response and cell death pathways. CDV Ond-infected AMs exhibited robust induction of pro-inflammatory mediators including type I interferon-related signaling pathways, whereas CDV R252-infected cells showed much weaker expression of these pathways. These transcriptomic differences were further highlighted by the detection of the highest rates of cell apoptosis and lactate dehydrogenase activity in the supernatants of CDV Ond-infected AM cultures over the entire course of the experiment. In addition, transcriptome differences indicate disturbances of homeostatic AM functions associated with CDV infection. These results provide insights into early events in the pathogenesis of CDV infection and mechanisms underlying vaccine strain attenuation.IMPORTANCEMorbilliviruses, including canine distemper virus (CDV) and human measles virus, cause severe systemic disease with respiratory distress, immunosuppression, and neurologic signs. While natural infection in dogs has become rare due to efficient vaccination, outbreaks in wildlife populations can be devastating, and concerns about zoonotic potential of CDV have been raised. The impact of CDV infection on the transcriptome of alveolar macrophages has not been elucidated thus far. Knowledge about early events in CDV pathogenesis and phenotypic consequences of vaccine attenuation is therefore necessary to protect endangered wildlife populations and might furthermore serve as a model for human measles. This study presents the first transcriptomic analyses of primary AMs during the initial phase of morbillivirus infection. These results provide insights into early events in the pathogenesis of CDV infection and mechanisms serving to restrict the spread of an attenuated virus strain.

Dental procedures in cats are routinely performed, with complications rarely reported. However, when complications do occur, they can be severe, potentially resulting in penetrating ocular trauma, often leading to vision loss and subsequent enucleation. This report describes retrobulbar abscessation, ascending bacterial optic neuritis, and bacterial meningoencephalitis as a complication following routine tooth extraction in a cat. A 12-year-old cat was presented six days after a routine dental procedure due to left-sided eye swelling, inappetence, and lethargy. General and ophthalmic examination revealed absent vision, hyphema, and exophthalmos of the left eye, suspected to be secondary to ocular trauma. During hospitalization, the cat’s mental status deteriorated, and a generalized epileptic seizure was observed. Due to the poor prognosis, the owners elected euthanasia. A postmortem MRI of the skull revealed retrobulbar and optic nerve inflammation, meningoencephalitis, and a suspected intracranial abscess potentially associated with the recent dental extraction. Necropsy confirmed a retrobulbar abscess, ascending bacterial optic neuritis, and bacterial meningoencephalitis. Bacterial meningitis and encephalitis should be considered as differential diagnoses in cats presenting with ocular changes and intracranial neurologic signs following routine dental procedures.

IntroductionDiagnosing feline nasal cavity diseases typically involves computed tomography, rhinoscopy, mycological examination, and histopathology. Culture-based bacteriological examination (cBE) is frequently performed, though its diagnostic and therapeutic relevance remains uncertain. Chronic rhinosinusitis (CRS), a diagnosis of exclusion, often responds poorly to standard antibiotics. This retrospective case series aimed to describe the correlation of cBE findings (1) across nasal diseases and (2) treatment responses in CRS cases.MethodsMedical records of 25 cats with confirmed nasal disease using comprehensive diagnostics were reviewed.ResultsIncluded were 11 CRS cats, 7 with mycotic rhinitis, and 7 with nasal neoplasia. In 24/25 cats, cBE was positive, with similar bacterial isolates across all groups. In CRS cats, treatment response did not consistently correlate with cBE results or antimicrobial susceptibility. 5/11 CRS cats showed clinical improvement following a 21-day doxycycline course. The remaining 6/11 CRS cats had not responded to previous targeted antibiotic therapy or empirical doxycycline for potential Mycoplasma species infection. 3/6 cats responded only to immunosuppressive therapy notably cyclosporine in two CRS cats, representing the first report in feline medicine. Non-responders were 3/6 CRS cats with marked turbinate destruction; 2/3 tested positive for feline herpesvirus 1.ConclusionFor diagnosing nasal diseases, cBE showed limited diagnostic relevance. In CRS, observations suggest that cBE may have limited diagnostic and therapeutic utility, leading to a clinical dilemma in interpretation. Empirical doxycycline treatment and immunosuppressive strategies, including cyclosporine, may be beneficial in selected CRS cases. Given the limitations of cBE, PCR testing for Mycoplasma species and viral pathogens may improve clinical decision-making in cats with CRS, both by helping to identify potential candidates for doxycycline treatment, and by assessing the risk of viral reactivation prior to initiating immunosuppressive therapy.

The discovery of several novel hepatovirus species in marine and terrestrial mammals has expanded the recognised members of the genus Hepatovirus and has provided better understanding on the evolutionary origins of human hepatovirus A (HAV). Using high throughput sequencing we detected a seal hepatovirus (SealHAV_NL/PV/21), in liver tissue of a deceased harbor seal (Phoca vitulina) originating from the Dutch North Sea coast. RT-PCR screening of liver samples of 88 harbor seals and 12 grey seals (Halichoerus grypus) from the same region identified seal hepatovirus in nine juvenile harbor seals in which minor sequence variation was observed in the VP1 gene. Whole-genome sequence analysis showed that SealHAV_NL/PV/21 displayed 95.6% nucleotide indentity to New England seal hepatovirus but had a 5′-UTR which contained additional 51 bp. Phylogenetic analysis showed that seal hepatoviruses clustered in a monophyletic group separate from other hepatovirus species that have been identified in terrestrial mammals. Assessment of seal hepatovirus RNA loads in organs of all infected animals showed that the liver had the highest number of RNA copies with up to 107 RNA copies per mg of tissue. Seal hepatovirus RNA was readily detected by in situ hybridization in hepatocytes in the liver but was not associated with pathological lesions. Serological screening of 90 contemporary seal sera using a HAV-based ELISA showed the presence of hepatovirus antibodies in 14 harbor seals and one juvenile grey seal. These findings collectively show that seal hepatovirus is enzootic among seals of the North Sea, causing quiescent infections in young animals.

Congenital melanocytic neoplasia is a rare disease that is described for the pig breeds Duroc, Iberico and Nero Siciliano used in agriculture. The hereditary nature of this neoplastic condition has been substantiated. The clinical course is unpredictable, spanning from complete spontaneous regression of primary tumors and survival of afflicted animals to a fatal progression marked by metastases to internal organs. In contrast to other species, no clinical or histological prognostic criteria for assessing the clinical course of disease exist in pigs. Four cases of cutaneous melanocytic neoplasia are described that occurred concurrently in three small-scale farms in northwestern Germany in 2023. These cases underwent thorough diagnostic evaluation employing a spectrum of modalities including clinical examination, hematological analysis, pathohistological examination, X-ray imaging, broncho-alveolar lavage, computed tomography, and autopsy. The first and the second case deal with two Duroc crossbred littermates with divergent courses of disease: While the black colored piglet had to be euthanized at eight weeks of life due to widespread metastases affecting multiple organs, the neoplastic disease remained localized to the primary tumor in the red-brown colored pig. Broncho-alveolar lavage was utilized in the black colored piglet to identify metastatic lesions of the melanoma within the lung tissue. The third case represents the initial observation of an affected Duroc gilt manifesting generalized leukoderma and leukotrichia during the regression phase of the cutaneous melanocytic tumor. The first observation of a congenital melanoma in a German Saddleback (variety: Husum Red Pied) is described in the fourth case. Notably, the primary tumor exhibited regression over the course of the disease. A higher incidence of this neoplastic disease can be assumed for small-scale farms in northwest Germany compared to professional pig husbandry due to potential inbreeding. No epidemiological or family link could be found between the two cases of affected Duroc pigs. Notably, the endangered Husum Red Pied breed maintains a limited genetic diversity, emphasizing the imperative of integrating considerations of this disease into breeding programs to mitigate the heightened risk of hereditary neoplastic afflictions in subsequent generations.

Human noroviruses are the most common cause of viral gastroenteritis worldwide, causing sporadic cases and outbreaks. Genetically related animal noroviruses infect wild and domestic animals including pigs and dogs. To investigate the potential of noroviruses to jump the species barrier, we used porcine, canine, and avian precision-cut intestinal slices. We show that human norovirus can bind to pig and dog intestinal tissue and be taken up with a similar efficiency as the porcine and canine noroviruses, respectively. In contrast, no binding or internalization of human, porcine, or canine noroviruses was detected in chicken tissue. We further showed that human norovirus can replicate to some degree in pig intestinal tissue, infecting single cells. In contrast, while animal noroviruses attached to human intestinal cells, intracellular uptake was limited. This suggests that human-to-animal transmission is more likely than animal-to-human transmission and that viral uptake likely presents a species barrier. ### Competing Interest Statement The authors have declared no competing interest. Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), 542416050 Nationale Forschungsplattform für Zoonosen (Research Network Zoonotic Infectious Diseases), 01KI2310