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Single cell RNA sequencing (scRNA-seq) can be used to resolve the cellular and molecular heterogeneity within a tissue by identifying cell populations with an unprecedented granularity along with their transcriptional signatures. Yet, the single cell gene expression profiles of cell populations in the healthy canine lung tissue remain unexplored and such analysis could reveal novel cell populations or markers lacking in dogs and facilitate comparisons with lung diseases. Using fresh healthy lung biopsies from four dogs, we conducted droplet-based scRNA-seq on 26,278 cells. We characterized 46 transcriptionally distinct cell subpopulations across all lung tissue compartments including 23 immune, 13 mesenchymal, five epithelial and five endothelial cell subpopulations. Of note, we captured rare cells such as unconventional T cells or Schwann cells. Differential gene expression profiles identified specific markers across all cell subpopulations. Fibroblasts clusters exhibited a marked transcriptional heterogeneity, some of which might exert immune regulatory functions. Finally, the integration of canine lung cells with an annotated human lung atlas highlighted many similarities in gene expression profiles between species. This study thus provides an extensive molecular cell atlas of the healthy canine lung, expanding our knowledge of lung cell diversity in dogs, and providing the molecular foundation for investigating lung cell identities and functions in canine lung diseases. Besides, the occurrence of spontaneous lung diseases in pet dogs, with phenotypes closely resembling those in humans, may provide a relevant model for advancing research into human lung diseases.

Background Comparison of clinical findings, chest radiographs (CXR), lung ultrasound (LUS) findings, and C‐reactive protein (CRP) concentrations at admission and serial follow‐up in dogs with aspiration pneumonia (AP) is lacking. Hypothesis Lung ultrasound lesions in dogs with AP are similar to those described in humans with community‐acquired pneumonia (comAP); the severity of CXR and LUS lesions are similar; normalization of CRP concentration precedes resolution of imaging abnormalities and more closely reflects the clinical improvement of dogs. Animals Seventeen dogs with AP. Methods Prospective observational study. Clinical examination, CXR, LUS, and CRP measurements performed at admission (n = 17), 2 weeks (n = 13), and 1 month after diagnosis (n = 6). All dogs received antimicrobial therapy. Lung ultrasound and CXR canine aspiration scoring systems used to compare abnormalities. Results B‐lines and shred signs with or without bronchograms were identified on LUS in 14 of 17 and 16 of 17, at admission. Chest radiographs and LUS scores differed significantly using both canine AP scoring systems at each time point (18 regions per dog, P < .001). Clinical and CRP normalization occurred in all dogs during follow up. Shred signs disappeared on LUS in all but 1 of 6 dogs at 1 month follow‐up, while B‐lines and CXR abnormalities persisted in 4 of 6 and all dogs, respectively. Conclusion and Clinical Importance Lung ultrasound findings resemble those of humans with comAP and differ from CXR findings. Shred signs and high CRP concentrations better reflect clinical findings during serial evaluation of dogs.

Bronchiectasis (BE) and bronchomalacia (BM) are chronic respiratory diseases in dogs, yet their combined occurrence (BEBM) is not well studied. This retrospective study analyzed 65 dogs diagnosed via endoscopy with BE, BM, or BEBM (E-BE, E-BM, E-BEBM) to identify clinical and pathological differences and assess how imaging results (radiography and computed tomography (CT)) align with endoscopic findings. Clinical symptoms like coughing, dyspnea, and exercise intolerance were similar across all groups, except lung crackles, which were more common in E-BEBM. Inflammation seen during bronchoscopy and bronchoalveolar lavage fluid results, including neutrophil counts, showed no significant differences between groups. Bacterial infections were present in 15% of dogs with no difference among groups. Diagnostic agreement between radiography and endoscopy was low: 18.1% for E-BE, 10.5% for E-BM, and 38.4% for E-BEBM. CT results matched endoscopic findings in all E-BE cases but only in half of E-BM and 40% of E-BEBM cases. The bronchial-to-arterial ratio, a benchmark for BE diagnosis, did not align with CT findings. Overall, the study found limited clinical or pathological differences between BE, BM, and BEBM and limited concordance between imaging and endoscopic findings, emphasizing the need for further research to clarify potential implications for treatment strategies.

Canine idiopathic pulmonary fibrosis (CIPF) is an interstitial lung disease reported in West Highland white terriers (WHWTs). B-mode ultrasonography (US) is used in human medicine as an adjunct tool for interstitial lung disease, including idiopathic pulmonary fibrosis. In veterinary medicine, thoracic US has been described as helpful for the diagnosis of various pulmonary diseases. The aim of this study was to describe the thoracic B-mode US findings in CIPF WHWTs, compared with those in control WHWTs. Twenty-seven WHWTs, including CIPF and control WHWTs, were prospectively enrolled. Standardised thoracic B-mode US was performed. The presence of an irregular pleural surface, ring-down artefact and peripheral nodules was assessed and scored for each location. An overall cumulative score was calculated by adding the individual scores of each location. WHWTs affected with CIPF had significantly higher overall scores compared to the control group. The ring-down artefact score was significantly higher in the CIPF group compared to the control group. No preferential location for the lesions was observed. A cut-off value of 15 ring-down artefacts for the entire thorax predicted CIPF in WHWTs with a sensitivity of 76.5% and a specificity of 80% (AUC 0.815). The present study describes B-mode US findings in CIPF WHWTs.

Background Extrinsic and intrinsic factors have been shown to influence nasal microbiota (NM) in humans. Very few studies investigated the association between nasal microbiota and factors such as facial/body conformation, age, and environment in dogs. The objectives are to investigate variations in NM in healthy dogs with different facial and body conformations. A total of 46 dogs of different age, living environment and from 3 different breed groups were recruited: 22 meso−/dolichocephalic medium to large breed dogs, 12 brachycephalic dogs and 12 terrier breeds. The nasal bacterial microbiota was assessed through sequencing of 16S rRNA gene (V1-V3 regions) amplicons. Results We showed major differences in the NM composition together with increased richness and α-diversity in brachycephalic dogs, compared to meso−/dolichocephalic medium to large dogs and dogs from terrier breeds. Conclusion Healthy brachycephalic breeds and their unique facial conformation is associated with a distinct NM profile. Description of the NM in healthy dogs serves as a foundation for future researches assessing the changes associated with disease and the modulation of NM communities as a potential treatment.

Background Evidence regarding optimal treatment duration in dogs with aspiration pneumonia (AP) and the role of thoracic radiographs (TXR) and lung ultrasonography (LUS) in the long‐term follow‐up of affected dogs is lacking. C‐reactive protein (CRP) is a reliable acute phase protein to monitor bacterial pneumonia in dogs. Hypothesis Investigate the safety of antimicrobial discontinuation based on clinical improvement and serum CRP normalization, as well as the usefulness of TXR and LUS for follow‐up. Animals Dogs diagnosed with AP and treated with antimicrobials. Methods Prospective observational study. Antimicrobials were discontinued based on clinical improvement and serum CRP normalization after 1, 3, or 5 weeks. At each consultation, a quality‐of‐life questionnaire, physical examination, serum CRP, TXR, and LUS were assessed. Short‐ (2 weeks) and long‐term (>1 month) follow‐ups after treatment discontinuation were performed to monitor for possible relapses. Results Seventeen dogs were included. Antimicrobials were discontinued after 1 week in 12 dogs (70.6%) and 3 weeks in the remaining 5 dogs (29.4%). Short‐term relapse was not observed in any dog and long‐term relapse was diagnosed in 3 dogs. Thoracic radiographs and LUS were useful for diagnosis, but did not add additional information during follow‐up, because image normalization lagged behind clinical improvement and serum CRP normalization. Conclusion and Clinical Importance Dogs with AP can be safely and effectively treated using a short‐term antimicrobial regimen discontinued after clinical improvement and serum CRP normalization. Imaging might still be useful for complicated cases with a less favorable response to treatment.

Background Pathogenesis of canine fungal rhinitis is still not fully understood. Treatment remains challenging, after cure turbinate destruction may be associated with persistent clinical signs and recurrence of fungal rhinitis can occur. Alterations of the nasal microbiota have been demonstrated in dogs with chronic idiopathic rhinitis and nasal neoplasia, although whether they play a role in the pathogenesis or are a consequence of the disease is still unknown. The objectives of the present study were (1) to describe nasal microbiota alterations associated with fungal rhinitis in dogs, compared with chronic idiopathic rhinitis and controls, (2) to characterize the nasal microbiota modifications associated with successful treatment of fungal rhinitis. Forty dogs diagnosed with fungal rhinitis, 14 dogs with chronic idiopathic rhinitis and 29 healthy control dogs were included. Nine of the fungal rhinitis dogs were resampled after successful treatment with enilconazole infusion. Results Only disease status contributed significantly to the variability of the microbiota. The relative abundance of the genus Moraxella was decreased in the fungal rhinitis (5.4 ± 18%) and chronic idiopathic rhinitis (4.6 ± 8.7%) groups compared to controls (51.8 ± 39.7%). Fungal rhinitis and chronic idiopathic rhinitis groups also showed an increased richness and α-diversity at species level compared with controls. Increase in unique families were associated with fungal rhinitis (Staphyloccaceae, Porphyromonadaceae, Enterobacteriaceae and Neisseriaceae) and chronic idiopathic rhinitis (Pasteurellaceae and Lactobacillaceae). In dogs with fungal rhinitis at cure, only 1 dog recovered a high relative abundance of Moraxellaceae. Conclusions Results confirm major alterations of the nasal microbiota in dogs affected with fungal rhinitis and chronic idiopathic rhinitis, consisting mainly in a decrease of  Moraxella . Besides, a specific dysbiotic profile further differentiated fungal rhinitis from chronic idiopathic rhinitis. In dogs with fungal rhinitis, whether the NM returns to its pre-infection state or progresses toward chronic idiopathic rhinitis or fungal rhinitis recurrence warrants further investigation.

Single-cell mRNA-sequencing (scRNA-seq) is a technique which enables unbiased, high throughput and high-resolution transcriptomic analysis of the heterogeneity of cells within a population. This recent technique has been described in humans, mice and other species in various conditions to cluster cells in populations and identify new subpopulations, as well as to study the gene expression of cells in various tissues, conditions and origins. In dogs, a species for which markers of cell populations are often limiting, scRNA-seq presents with elevated yet untested potential for the study of tissue composition. As a proof of principle, we used scRNA-seq to identify cellular populations of the bronchoalveolar lavage fluid (BALF) in healthy dogs ( = 4). A total of 5,710 cells were obtained and analyzed by scRNA-seq. Fourteen distinct clusters of cells were identified, further identified as macrophages/monocytes (4 clusters), T cells (2 clusters) and B cells (1 cluster), neutrophils (1 cluster), mast cells (1 cluster), mature or immature dendritic cells (1 cluster each), ciliated or non-ciliated epithelial cells (1 cluster each) and cycling cells (1 cluster). We used for the first time in dogs the scRNA-seq to investigate cellular subpopulations of the BALF of dog. This study hence expands our knowledge on dog lung immune cell populations, paves the way for the investigation at single-cell level of lower respiratory diseases in dogs, and establishes that scRNA-seq is a powerful tool for the study of dog tissue composition.

Background In dogs with sinonasal aspergillosis (SNA) the utility of PCR in the diagnosis and monitoring of the disease after treatment has not been assessed. Objectives To evaluate the presence of fungal DNA using quantitative PCR targeting Aspergillus fumigatus (Aspfum) and Aspergillus spp. (PanAsp), and PCR targeting multiple fungal species (PanFun), in samples obtained from nasal cavities of dogs with SNA, other nasal diseases and healthy dogs. Animals Sixty‐two dogs including 20 with SNA, 12 with cured SNA (of which 10 are from the SNA group), 20 dogs with Non‐SNA nasal disease, and 20 healthy dogs. Methods Prospective cross‐sectional study. Aspfum, PanAsp, and PanFun were performed on blindly collected nasal swabs obtained in anesthetized dogs. Results In SNA dogs, Aspfum and PanAsp were positive in 13/20 and 14/20 dogs. In all dogs in the 3 other groups, A. fumigatus DNA was not detected using Aspfum. PanAsp was positive in 3 non‐SNA dogs: 1 with cured SNA and 2 with Non‐SNA nasal disease. A Ct cut‐off value of 33.3 for Aspfum demonstrated 65% sensitivity and 100% specificity. A Ct cut‐off value of 34.5 for PanAsp demonstrated 70% sensitivity and 96.2% specificity. PanFun was positive in 16/20, 12/12, 19/20, and 7/20 dogs in the SNA, cured SNA, Non‐SNA, and healthy groups, respectively. Conclusion and Clinical Importance Aspfum and PanAsp on blindly collected nasal swabs can be useful for the detection of SNA at diagnosis and at cure, especially when more invasive methods are not available.

This review focuses on the role of the lung microbiome in idiopathic pulmonary fibrosis. Although historically considered sterile, bacterial communities have now been well documented in lungs both in healthy and pathological conditions. Studies in idiopathic pulmonary fibrosis (IPF) suggest that increased bacterial burden and/or abundance of potentially pathogenic bacteria may drive disease progression, acute exacerbations, and mortality. More recent work has highlighted the interaction between the lung microbiome and the innate immune system in IPF, strengthening the argument for the role of both host and environment interaction in disease pathogenesis. Existing published data suggesting that the lung microbiome may represent a therapeutic target, via antibiotic administration, immunization against pathogenic organisms, or treatment directed at gastroesophageal reflux. Taken altogether, published literature suggests that the lung microbiome might serve in the future as a prognostic biomarker, a therapeutic target, and/or provide an explanation for disease pathogenesis in IPF.