Background – The identification of the activation of the mammalian target of rapamycin (mTOR) signalling pathway as a frequent molecular event in canine cutaneous papillomas (CPs) has provided the rational foundation to explore novel molecular-targeted therapies. Recent evidence indicates that metformin reduces the size of CPs in mice by inhibiting the mTOR signalling pathway. These effects require the expression of the organic cation transporter 3 (OCT3/SLC22A3), a well-known metformin uptake transporter. Hypothesis/Objectives – The aim of the present study was to characterise the expression pattern of the metformin uptake transporter OCT3 in canine samples of CP that have shown activation of the mTOR signalling pathway in order to predict if this hyperplastic epidermal lesion is potentially sensitive to metformin. Conclusions and Clinical Relevance – These results show that canine CPs exhibit the expression of surrogate markers that suggest sensitivity to metformin, such as upregulated OCT3 and pS6 expression. Taken together, these findings provide the rationale for the early assessment of the use of metformin as a mechanism-based therapeutic approach for treating canine patients with persistent or multiple CPs.

Background – Epicutaneously house dust mite-sensitised (HDM-S) healthy dogs are commonly used as canine atopic dermatitis (cAD) models; however, the exact mechanisms of HDM-induced AD immune activation in HDM-S and HDM-nonsensitised (NS) dogs remain unclear. Objectives – To characterise the inflammatory and pruritogenic transcriptome of acute epicutaneous HDM-induced skin lesions at 6 h and 24 h in HDM-NS and HDM-S dogs; untreated skin at 0 h from each dog served as control. Conclusions and Clinical Relevance – Taken together, we establish that epicutaneous HDM patch application induces immune changes in HDM-NS dogs with Th2 dominance and activates several itch-promoting pathways.

Background – Itch is a common symptom in skin disorders. While the neural pathways of itch transmission from the skin to the brain are well-understood in rodents, the same pathways in dogs remain unclear. The knowledge gap hinders the development of effective treatments for canine itch-related disorders. Hypothesis/Objectives – This study aimed to investigate the differential gene expression in the dorsal root ganglia between healthy and atopic dogs to identify specific molecules potentially involved in itch signalling and neuroinflammation in canine atopic dermatitis (cAD). Conclusions and Clinical Relevance – Our study suggested that dysregulation of neuroinflammatory pathways might play a role in the pathomechanism of canine AD as in humans.

Background – Canine auricular cholesteatoma (more appropriately named tympanokeratoma) is an epidermoid cyst whose aetiopathogenesis remains poorly recognised in veterinary medicine. There are a few reports published, possibly because it may be underdiagnosed. Objectives – To characterise the clinical aspects of dogs with tympanokeratoma, to describe the otoendoscopic, advanced imaging and histopathological findings of tympanokeratoma and to report the best approach to diagnose canine auricular tympanokeratoma in a retrospective study. Conclusions and Clinical Relevance – Tympanokeratoma should be suspected in brachycephalic dogs with otitis externa and peripheral vestibular syndrome, and samples of keratinous material from the middle ear associated with histopathological results may be the best approach for the diagnosis.

Background – Early and accurate diagnosis of otitis externa is crucial for correct management yet often can be challenging. Artificial intelligence (AI) is a valuable diagnostic tool in human medicine. Currently, no such tool is available in veterinary dermatology/otology. Objectives – As a proof-of-concept, we developed and evaluated a novel YOLOv5 object detection model for identifying healthy ear canals, otitis or masses in the canine ear canal. Conclusions and Clinical Relevance – This novel AI object detection model has the potential for application in the field of veterinary dermatology. An external validation study is needed before clinical deployment.

Background – In humans, food allergies (FAs) are divided into those with immunoglobulin (Ig) E-mediated (immediate FA), cell-mediated (delayed FA) or both mechanisms (mixed FA). In dogs, lymphocyte stimulation tests have the highest concordance with oral food challenges (OFCa). Objectives – To report the evaluation of a lymphocyte proliferation test (LPT) in dogs with FA and delayed reactions (≥6 h) after OFC. Conclusions and Clinical Relevance – FAs with delayed reactions after OFC—those suspected of having a cell-mediated mechanism—seem to be the most common type of FA in dogs. The LPT is helpful in identifying such cases.

Background – Allergen immunotherapy is used as aetiological treatment for canine atopic dermatitis (cAD). Objective – To assess the anti-inflammatory agent-sparing effect over 1 year of immunotherapy using pullulan-conjugated recombinant Der f 2 (rDf2-P). Conclusions and Clinical Relevance – Der f 2-P immunotherapy can lead to a rapid reduction in anti-inflammatory drug use and serve as an effective proactive therapy for cAD.

Background – Canine atopic dermatitis (cAD) is a chronic, inflammatory, multifactorial and pruritic disease. The presence of skin barrier impairment (e.g. filaggrin alterations), along with abnormal immune responses, can negatively impact cutaneous barrier function. Objectives – To evaluate the filaggrin 2 (FLG2) expression in atopic dogs before and after the administration of oclacitinib maleate. Conclusions and Clinical Relevance – Oclacitinib maleate could have a positive impact on cutaneous barrier structure, improving FLG2 expression by decreasing inflammation and cutaneous trauma.

Background – Canine atopic dermatitis (cAD) is a complex skin disease characterised by barrier dysfunction. Studies regarding the role of skin surface lipids (SSL) in cAD are needed. Objectives/Hypothesis – Evaluate the feasibility of using D-squame tape-stripping for SSL collection and ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry (UHPLC-HRMS) for untargeted lipidomic analysis. A secondary objective was to identify significant differences in SSL between atopic and healthy dogs and between different body sites. Conclusions and Clinical Relevance – Our findings suggest that D-squame tape-stripping combined with UHPLC-HRMS is a feasible method for SSL research in cAD. Lipid species-specific differences and significant regional variations were found, emphasising the importance of considering body sites in future studies. This study underscores the need for further research to understand the role of SSL in cAD and the insights that untargeted lipidomic analysis can provide.

Background – Sporotrichosis is a chronic, mycotic infection caused by fungi of the genus Sporothrix. Zoonotic sporotrichosis occurs mainly through S. brasiliensis transmission, resulting from the organism's traumatic introduction via scratches or bites, or contact with exudate from contaminated cats. The loop-mediated isothermal amplification (LAMP) assay is a viable molecular alternative for detecting Sporothrix in veterinary low-resource settings. Hypothesis/Objectives – To develop a LAMP method for Sporothrix identification using fungal isolates and clinical samples of domestic cats (Felis catus). Conclusions and Clinical Relevance – These findings support a simple and quick LAMP-based screening tool for detecting Sporothrix in isolated and clinical samples. This accessible test can aid in disease management when standard culture analysis is unavailable or impractical.

Background – Antimicrobial resistance is increasing each year. For example, in 2019, it was directly responsible for an estimated >1 million deaths. Additionally, the development of new drugs is much slower, generating enormous concerns about responses to infection in the future health scenario. Therefore, probiotics have emerged as an alternative to antibiotics. Objectives – This study aimed to isolate and identify a Lactobacillus casei from healthy canine skin and investigate its antimicrobial effect on isolates of Staphylococcus pseudintermedius originating from dogs with pyoderma. Conclusions and Clinical Relevance – The study indicates that using commensal bacteria from canine skin, specifically L. casei, to control bacterial infections caused by S. pseudintermedius can be a promising complementary or alternative therapy to antibiotics relevant to animal and human health.

Background – Erythritol, a sugar alcohol, has been reported to suppress the in vitro growth of Staphylococcus pseudintermedius and Staphylococcus coagulans. Objectives – To determine whether erythritol suppresses the growth of Staphylococcus hyicus, a major pathogen causing porcine exudative epidermitis, and to investigate the molecular mechanisms involved in erythritol-induced S. hyicus growth suppression. Conclusions and Clinical Relevance – Erythritol suppresses the in vitro growth of S. hyicus by inhibiting intracellular sugar and arginine metabolisms under aerobic and anaerobic conditions, respectively.

In bearded dragons (Pogona vitticeps), nannizziomycosis can cause skin lesions, ulceration and lethargy. Formally known as yellow fungal disease (YFD), nannizziomycosis has traditionally been attributed to various Nannizziopsis spp. identified via culture and referred to as Chrysosporium anamorph of Nannizziopsis (CANV). However, Nannizziopsis presence does not always lead to nannizziomycosis. Instead, this disease may be caused by multiple pathogens or interactions between microbes (known as the cross-kingdom effect). Using next-generation sequencing (NGS), the bacterial and fungal microbiota of 31 bearded dragons with suspect nannizziomycosis (unhealthy group) and 20 healthy bearded dragons (healthy group) were analysed. One unidentified species within the Nannizziopsis genus (Nannizziopsis sp.) was included in a co-occurrence analysis between 877 bacterial and 78 fungal species in the unhealthy group. Forty-one positive co-occurrences with Nannizziopsis spp. were seen, including Salmonella enterica (p = 0.001), an unidentified species within the Clostridiales order (p < 0.001) and a fungal species from the Cladosporium genus (p = 0.0261). Forty-nine negative interactions with Nannizziopsis spp. were seen, including Bifidobacterium adolescentis (p = 0.0478) and Corynebacterium durum (p = 0.0478). These findings suggest that commensal microbes may change in response to counteract Nannizziopsis, while pathogenic microbes may help facilitate it.

Uveodermatological syndrome and alopecia areata are autoimmune disorders causing ocular and dermatological inflammation and alopecia, respectively, in dogs. This is the first report to document concurrent development of the two diseases in a dog, as has been reported in human patients. Clinical presentation and histopathological diagnosis, treatment and clinical follow-up are described.