BACKGROUND:Assessment of alkaline phosphatase (ALP) activity in cytologic smears is used as a phenotyping tool for hematopoietic and solid tissue neoplasms in dogs. Different procedures that vary in substrate-dye combinations, fixative, incubation times, and nuclear counterstains are available for detection of ALP activity. It is unknown if these procedures provide comparable results for phenotyping tumors in the same animal. OBJECTIVE:To compare results obtained with three ALP cytochemical procedures in blasts in blood and tissue aspirate smears from dogs with previously diagnosed leukemia: naphthol-AS-MX phosphate/fast blue (fast blue), 5-bromo-4-chloro-3-indoxyl-phosphate/nitroblue tetrazolium (BCIP/NBT), and naphthol-AS-BI-phosphate/fast red violet LB (fast red). METHODS:Smears of blood, bone marrow, and lymph node from 54 dogs prospectively enrolled in a multi-institutional study on acute leukemia were stained and assessed. One observer counted the percentage of positive blasts and quantified staining intensity on a scale of 1-3. Cases were classified as acute myeloid leukemia, lymphoblastic leukemia/lymphoma, acute leukemia of ambiguous lineage, or acute lineage-negative leukemia based on flow cytometric analysis and myeloperoxidase cytochemical staining. RESULTS:The fast blue procedure yielded a significantly higher median percentage of ALP-positive blasts (48%) than the BCIP/NBT (46%) or fast red (42%) procedure despite similar median staining intensities. The proportion of samples that would have been classified as ALP-positive was similar (40/54 fast blue, 39/54 BCIP/NBT, and 37/54 fast red). CONCLUSIONS:Our results indicate that the three procedures can be used interchangeably for determining ALP activity in blasts of dogs with leukemia.

The objective of this study was to evaluate the effect of different fixatives and demineralizers on immunohistochemical (IHC) detection of antigens in bone marrow (BM). Sternal BM samples were collected within 24 hours of death from dogs with spontaneous disease, fixed with acetic acid-zinc-formalin (AZF) or 10% neutral-buffered formalin (NBF) for 24 hours, and decalcified with formic acid, hydrochloric acid, or ethylenediaminetetraacetic acid (EDTA) for 1, 12, or 24 hours, respectively. Immunohistochemical sections for CD3, CD20, CD34, CD204, FLT3, and factor VIII-related antigen (FVIII-rAG) were scored for background, signal intensity, and percent positive cells by 4 independent raters. Some endothelial but not hematopoietic cells were CD34 immunopositive, precluding further assessment. Immunopositive BM cells ranged from 1.3% to 18.3% (CD3), 1.3% to 22.3% (CD20), 0.5% to 22.5% (CD204), and 0% to 17.6% (FLT3). Background scores were similar for all antigens and fixatives except for CD3, for which NBF yielded lower scores than AZF. The signal intensity for all IHC assays was similar for AZF and NBF. The percentage of FLT3- and FVIII-rAG-immunopositive cells was slightly higher in AZF- than NBF-fixed samples. Different demineralizers yielded similar results for all IHC assays except higher background for CD20/EDTA. Signal intensity was higher for CD204 in samples demineralized with EDTA rather than acids. Higher percentages of CD204 and FLT3 immunopositive cells were noted with EDTA relative to acid demineralization. Overall, with the use of stringently standardized pre-analytic and processing protocols, all IHC assays yielded acceptable results, and differences between protocols were considered minor.

ABSTRACT Background Acute myeloid leukemia (AML) is difficult to distinguish from lymphoblastic leukemia or lymphoma (LL) on morphologic features alone. Therapeutic approaches for AML versus LL differ, and immediate therapy is often needed due to patient illness and rapid disease progression. Immunophenotyping is required for the distinction of AML from LL but is often not rapidly available. Hence, a routinely available method for distinguishing AML from LL at the time of diagnosis, such as myeloperoxidase (MPX) activity in tumor cells, is desirable. Objectives To determine whether MPX activity on the ADVIA peroxidase cytogram differentiates AML vs LL, as judged by a lower angle of a line intersecting the large unstained cell (LUC) cluster and the x‐axis on the ADVIA 2120 MPX cytogram (MPX LUC angle). Methods Dogs with suspect acute leukemia were prospectively enrolled, and ADVIA‐based hematology, flow cytometry, and cytochemical staining were performed in a multi‐institutional study. An observer blinded to sample identity determined the MPX LUC angle with Fiji software. Results Forty‐four cases met the inclusion criteria and were grouped as AML ( n = 30) or LL ( n = 14). No significant difference in the mean MPX LUC angle was identified between AML and LL ( p = 0.9). MPX cytochemical staining did not correlate with MPX LUC angle (Rsp = 0.004, p > 0.9). Conclusions The angle of the LUC population on the ADVIA MPX cytogram cannot be used as a rapid test to differentiate AML from LL.

Macrophage populations in the lung, including resident alveolar macrophages (AMs) and recruited monocyte-derived macrophages (MDMs), recognize the inhaled particulates in barn dust that cause severe equine asthma and orchestrate an immune response though the cytokines they produce. Despite their importance, the specific contributions of these macrophage subsets to lower airway inflammation remain poorly understood. This exploratory in vitro study investigated the likely contributions of AMs and MDMs from healthy horses to the early inflammatory response using RNA-seq. If biologically important contrasts were identified, future studies to elucidate differences in AM and MDM function in severely asthmatic horses could be undertaken. AMs and MDMs from six healthy female Standardbred horses were exposed for 6 h to a mixture of fungal spores, lipopolysaccharide, and silica microspheres (FLS), which represents the major components of barn dust, with serum-free cell culture medium as the control. Equine AMs and MDMs exposed to FLS showed broadly similar transcriptional responses, with cytokine signalling emerging as the dominant biological theme in both cell types. At an exploratory FDR threshold of 0.25, gene set enrichment analysis indicated that “JAK-STAT/IL-15 signalling pathway”, “NOD-like receptor signalling pathway”, and “infection/C-type lectin receptor” had greater enrichment in FLS-exposed MDMs than AMs. These exploratory data indicate that equine AMs and MDMs mount largely overlapping cytokine responses to the elements that contribute to exacerbation of severe equine asthma, but also exhibit cell-type specific pathway differences. This work establishes the baseline for future studies testing the hypothesis that in horses with severe equine asthma, AMs and MDMs each have altered function that contribute uniquely to disease pathogenesis.

BACKGROUND:An 8.8-year-old male neutered Persian cat was presented with a history of recent intermittent mild lethargy, hyporexia, and weight loss. Physical examination revealed pale mucous membranes, an enlarged right mandibular lymph node, and organomegaly suspected to be an enlarged spleen. A CBC showed an extreme leukocytosis composed almost exclusively of small lymphocytes and a moderate, microcytic, slightly regenerative anemia. OBJECTIVES:We aimed to diagnose the cause of the extreme leukocytosis, to classify the circulating leukocytes, and to determine the response to therapy. METHODS:Blood film review, biochemical and iron analysis, abdominal ultrasound, flow cytometric evaluation of leukocytes, serum and urine protein electrophoresis, and polymerase chain reaction for antigen receptor rearrangement (PARR) were performed. RESULTS:Leukocytes were mostly small lymphocytes with scant pale basophilic cytoplasm, and round or convoluted nuclei with coarse to finely clumped chromatin. There was hyperglobulinemia and iron deficiency. Imaging showed splenomegaly and multiple enlarged abdominal lymph nodes. On flow cytometry, the lymphocytes were positive for CD18, CD21, and MHC II, consistent with B-cell lymphocytic leukemia. The cat had mild hyperglobulinemia and 2+ proteinuria, and serum electrophoresis results were interpreted as a polyclonal gammopathy. PARR showed clonal rearrangement of IGH2 and IGH3 loci. Treatment with oral prednisolone and chlorambucil resulted in resolution of the clinical signs and reduction in the leukocytosis. CONCLUSIONS:B-cell chronic lymphocytic leukemia (B-CLL) was diagnosed, which in cats is much less frequent than T-CLL. There was a favorable response to alkylating therapy, and the cat survived for 19 months.

Objectives Kidney injury molecule 1 (KIM-1) is a transmembrane glycoprotein on proximal renal tubular epithelial cells that is increased in the urine of cats with acute kidney injury. The utility of measuring urine KIM-1 in cats with chronic kidney disease (CKD) and the relationship with International Renal Interest Society (IRIS) stage are unknown. The objectives of this study were to determine the distribution of KIM-1 concentrations in cats with different stages of CKD and investigate the relationship between urine KIM-1 and urine specific gravity (USG), urine protein and serum urea, creatinine, phosphorus, potassium and symmetric dimethylarginine concentrations. Methods A total of 74 cats with CKD were recruited prospectively from a first-opinion feline-only practice. Blood and urine samples were collected from all cats. The stage of CKD was determined as per IRIS guidelines. Urine KIM-1 concentration was determined with a previously validated lateral flow assay. KIM-1 was reported as a test:control ratio. The distribution of KIM-1 values in cats with CKD was determined, and the correlation between KIM-1 and other determinants of renal function was calculated. Urine KIM-1 was normalized to a USG of 1.035 and the analysis was repeated. Results Cats with CKD had a median urine KIM-1 value of 0.1544 (range 0.038–0.540). The median KIM-1 values in cats with IRIS stage 1, 2, 3 and 4 CKD were 0.152 (range 0.113–0.512), 0.165 (range 0.038–0.540), 0.150 (range 0.037–0.448) and 0.140 (range 0.067–0.448), respectively. There were no differences in urine KIM-1 values relative to IRIS stage. Urine KIM-1 values were correlated with USG ( r 2 = 0.482; P = 0.005). An analysis of KIM-1 values normalized to USG resulted in similar findings. Conclusions and relevance Urine KIM-1 values in cats with CKD were similar to those previously described in healthy cats. There was a moderately strong correlation between urine KIM-1 concentration and USG. Sequential measurement of KIM-1 in cats with progressive CKD may be informative.

Introduction: Acute leukemia represents a heterogeneous group of aggressive hematopoietic malignancies in humans, broadly encompassing myeloid (AML) and lymphoid (ALL) subtypes. Advances in human AL therapy have been driven by molecular profiling and the development of targeted treatments. However, preclinical models that capture disease heterogeneity and recapitulate the tumor microenvironment remain limited. Pet dogs spontaneously develop acute leukemias that share many clinical, biologic, and therapeutic features with their human counterparts, providing an opportunity to use dogs as a robust comparative and translational model. Despite this potential, the molecular drivers of canine acute leukemia are poorly defined. Methods: We extracted DNA from blood, bone marrow or lymph node aspirates and buccal swabs (as a germline control) from 33 dogs prospectively recruited for a study on acute leukemia. Using a flow cytometric-based antibody panel against lineage-associated antigens, leukemias were categorized as AML (only expressing myeloid antigens), ALL (only expressing lymphoid antigens), acute leukemia of ambiguous lineage (ALAL, expressing myeloid and lymphoid antigens), and acute lineage negative leukemia (ALNL, lacking lineage-associated markers). Extracted DNA was submitted for whole-exome (200x) or whole-genome sequencing (50-100x). Somatic variant calling was performed following GATK best practices, using Mutect2 in tumor–normal mode with a canine panel of normals (n = 77) and a curated germline variant database (n = 722). Candidate variants were filtered to those predicted to have moderate-to-high functional impact in known cancer-associated genes and excluded splice site mutations. Results: On flow cytometric analysis, 23, 2, 2 and 6 cases were classified as AML, ALL, ALAL and ALNL, respectively. Somatic mutations were identified in 31 of 33 (93.9%) tumor samples. Of the samples with identified variants, at least one somatic mutation in the RTK–RAS pathway (e.g., NRAS, KRAS, PTPN11, FLT3, KIT) was detected in 71% of cases, paralleling human AL where this pathway is a major driver. NRAS was the most frequently mutated gene (23%), with recurrent hotspots (G12, G13, Q61) shared with human leukemia. Additional pathway alterations were identified in Hippo (23), NOTCH (23%), and PI3K/WNT (10). Mutations in epigenetic modifiers, including KDM5C (10%), KAT6B (10%), and EZH2 (10%), were also common. In contrast, canonical human AL drivers DNMT3A and NPM1 were absent, and recurrent mutations were also seen in MED12 (13%), TPR (13%), CLIP1 (10%) , FAT3 (10%) and MAML2 (10%). Most variants were missense mutations, with a median of six variants per sample. Conclusions: Our results demonstrate that canine acute leukemia harbors both conserved and unique mutational events compared to humans. The high frequency of RTK–RAS pathway alterations highlight the potential of dogs as a spontaneous, immunocompetent model for dissecting leukemogenic mechanisms and advancing the development of pathway-targeted therapies.

Inflammation is a critical defense against pathogens but can impair iron metabolism and erythropoiesis, potentially causing or exacerbating anemia during infection. However, the ecological and evolutionary relevance of this trade-off remains poorly understood. Naturally co-evolved host–parasite systems offer a unique opportunity to explore how inflammatory responses balance the benefits of pathogen control against potential physiological costs. We examined how systemic inflammation affects recovery from hookworm-associated anemia in South American fur seal (Arctocephalus australis) pups, aiming to determine whether inflammation facilitates recovery or imposes hematological constraints. We longitudinally monitored 83 pups over approximately 3 months on Guafo Island, Northern Chilean Patagonia, measuring hookworm burden, hematological parameters, iron concentration, and blood cytokines. Seventy-two percent of the pups developed clinical hookworm infection, and 47% of these became anemic. Among anemic pups, 54% recovered from anemia 2 months after infection. Changes in inflammatory markers, but not hookworm burden, iron concentration, or body condition, predicted recovery outcome. Sustained increases in IFN-γ and neutrophils reduced the likelihood of recovery, while increased IL-10 concentration favored recovery. These effects were independent of plasma iron concentration, although IL-6 was negatively correlated with lower plasma iron. Our findings show that prolonged systemic inflammation impairs recovery from anemia in a wild marine mammal, highlighting a physiological cost of inflammation in early life as a key ecological trade-off between immune defense and hematological resilience in natural host–parasite systems.

Immune-mediated hematologic diseases (IMHD) including immune-mediated hemolytic anemia (IMHA) and immune thrombocytopenia (ITP) can cause severe disease in dogs. The underlying immune system abnormalities associated with these conditions is not known. The hypotheses of this study were that dogs with IMHD would have increased frequencies of CD4+ and CD8 + lymphocytes, decreased frequencies and numbers of T regulatory cells, and increased frequencies of interleukin (IL)-17 + lymphocytes. Fifteen dogs with newly diagnosed IMHA or ITP and 15 healthy control dogs were recruited for this prospective study. Flow cytometry was used to enumerate CD4 + lymphocytes, CD8 + lymphocytes, T regulatory (CD4 + CD25 + Foxp3+) cells, and lymphocytes secreting IL-17 in dogs with IMHD at diagnosis, then 2 and 4 days after starting immunosuppressive treatment. Median proportion of CD4+ (Day 0: 3.4%, Day 2: 3.3%) and CD8+ (Day 0: 1%, Day 2: 0.6%) cells was lower in dogs with IMHD compared to control dogs (CD4 + 22.8%, CD8 + : 13.6%; P < 0.0001 for each). Additionally, T regulatory cells were reduced in IMHD dogs at Day 0 (0.2% versus 0.6% of total lymphocytes, P = 0.0025). Dogs with IMHD had a higher proportion of lymphocytes positive for IL-17 at Day 2 (1.3%) compared to control dogs (0.4%, P = 0.0024). Dogs with IMHD have immune system alterations at diagnosis and during early treatment characterized by a deficiency in T regulatory cells and an increase in IL-17 + lymphocyte. These changes might contribute to the pathogenesis of IMHA and ITP.

An 8-mo-old Mastiff-cross dog with bone pain and lytic-proliferative lesions in the radius, ulna, femur, vertebral spinous processes, and ribs, was diagnosed with lymphoma. The dog also had anemia and thrombocytopenia, and atypical circulating lymphocytes were identified as B cells by flow cytometry. Due to the multicentric, rapidly progressive disease, the dog was euthanized. Postmortem examination confirmed extensive bone replacement by lymphoma, and infiltration of lymph nodes, spleen, and liver. Histomorphology and immunohistochemistry showed a diffuse large B-cell lymphoma that was immunopositive for PAX5 and CD20, and immunonegative for CD3. Lymphoma of bone is rare in dogs and humans, and is most frequently reported in pediatric individuals. Including our case, 7 of 14 reported cases occurred in dogs <2-y-old, and all but 1 had polyostotic disease. Long bones, ribs, and vertebrae were affected most often, and the distal metaphyseal region was targeted in long bones. Visceral and nodal tissue infiltration was common, and all tumors had a diffuse architecture. Most dogs with polyostotic lymphoma were euthanized at the time of diagnosis, and survival was <6 wk in dogs that were treated with chemotherapy or surgery.

Bone marrow (BM) samples in dogs are typically acquired from hematopoietically active trabecular BM at appendicular skeletal sites, such as the proximal humerus and femur, or axial skeletal sites, such as pelvis, sternum, and rib. Suitability for in vivo biopsy varies by site, but equivalency of BM composition at different sites is uncertain. We sought to determine whether the composition of BM is comparable in humerus, ilium, rib, and sternum. Samples from each site were obtained within 24 h after death from 30 dogs with spontaneous disease submitted for postmortem examination. Tissues were fixed in acetic acid-zinc-formalin, demineralized with EDTA, and assessed by 4 independent raters for hematopoietic cellularity, granulocytic:erythrocytic (G:E) cell ratio, megakaryocyte (MKC) number, and presence of hemosiderin. Statistical analysis showed lower cellularity, MKC number, and hemosiderin in ilium than in rib, higher cellularity in rib and sternum than in humerus and ilium, and lower G:E cell ratio in rib than in humerus (p < 0.05). Analysis of covariance indicated that most differences between sites were attributable to individual animal variation rather than site or rater. Differences overall were of small magnitude, and values for each parameter were similar to those reported in healthy younger dogs. We concluded that samples from any of the 4 sites are suitable to approximate composition of BM at the other sites.

BACKGROUND:Spinal neoplasms are sparsely documented in juvenile dogs. Case reports and small case series have described nephroblastomas, primitive neuroectodermal tumours, gliomas, certain sarcomas, and osteochondromas, but round cell sarcomas have not previously been documented. CASE PRESENTATION:This case report describes a 10-week-old female Rottweiler puppy with acute onset of progressive ataxia and pelvic limb lameness. Neurological examination localised a T3-L3 myelopathy and MRI revealed an ovoid, well-marginated mass extending from mid L3 to caudal L4 vertebrae. Post-mortem examination, histopathology, and immunohistochemistry confirmed a round cell sarcoma of extradural origin. CONCLUSION:Our case report stresses the importance of performing MRI even in very young individuals with acute progressive signs of spinal cord lesions. Clinicians should include spinal tumours as a differential diagnosis for juvenile canines with spinal neurological signs. Round cell sarcoma should be added to the list of spinal tumours in young dogs.

The majority of canine lymphoma patients treated with the standard of care, the CHOP chemotherapy protocol, initially achieve remission but eventually relapse with a multi-drug-resistant phenotype. This study assesses gene expression profiles of canine lymphoma tumor cell populations using RNA-Seq data from 15 matched patient samples taken prior to treatment and again six weeks into treatment with CHOP. Two distinct clusters were present in the t-SNE dimensionality reduction of the gene expression profiles. There was a significant difference in progression-free survival (PFS) between the cluster groups, with a median of 43.5 days in a group of six patients and 185 days in another group of nine patients. Comparing the group with shorter PFS to the group with longer PFS, we identified 265 significantly enriched GO:BP terms in 3874 significantly up-regulated genes and 740 significantly enriched GO:BP terms in 3236 significantly down-regulated genes. Comparing the six-week timepoint against the initial timepoint, in the group with longer PFS, we identified 277 significantly enriched GO:BP terms in 413 significantly up-regulated genes and 222 significantly enriched GO:BP terms in 267 significantly down-regulated genes. In the group with shorter PFS, we only identified 27 significantly differentially expressed genes, for this comparison. We found DNA damage response genes to be enriched in the down-regulated genes in both comparisons. These results identify and characterize two transcriptionally distinct groups of canine lymphoma patients with significantly different responses to CHOP chemotherapy.

Objectives The aim of the present study was to establish a reference interval (RI) for urine kidney injury molecule-1 (KIM-1) in healthy cats. Methods History, physical examination, blood pressure, and feline immunodeficiency virus and feline leukemia virus serology status were determined. A complete blood cell count, serum biochemical profile, urinalysis and kidney ultrasound were performed, and N-terminal pro-brain natriuretic peptide, total thyroxine (TT4) and urine KIM-1 were measured. An RI was calculated and the effect of age, sex, body condition score (BCS), blood pressure, symmetric dimethylarginine (SDMA), serum creatinine concentration (SCr), phosphorus, TT4, urine specific gravity (USG) and mid-sagittal kidney length on urine KIM-1 was evaluated using a general linear model. Results Of 69 recruited cats, 50 met the inclusion criteria. There were 35 male cats and 15 female cats, with a median age of 4.3 years (range 1.0–12.3), median weight of 5.11 kg (range 2.52–8.45) and median BCS of 6/9 (range 3–8). The median serum concentrations were SDMA 11.0 µg/dl (range 2–14), SCr 88.5 µmol/l (range 47–136), phosphorus 1.41 mmol/l (range 0.8–2.2) and TT4 32.0 nmol/l (range 17–51). Median USG was 1.057 (range 1.035–1.076), mid-sagittal left kidney length was 3.50 cm (range 2.94–4.45) and mid-sagittal right kidney length was 3.70 cm (range 3.06–4.55). The derived RI for urine KIM-1 was 0.02–0.68. USG was a significant ( P <0.001) predictor of urine KIM-1. Individually, age, sex, blood pressure, BCS, SDMA, SCr, phosphorus, TT4 and mid-sagittal kidney length were not significant predictors of urine KIM-1. In a multivariate model, if combined with USG, SDMA concentration was predictive ( P = 0.030) of urine KIM-1. Conclusions and relevance Urine concentration was significantly correlated with urine KIM-1, which will be an important consideration when interpreting findings in cats with potential kidney injury.

Myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) are heterogeneous neoplasms of hematopoietic stem cells that are challenging to diagnose, differentiate, and prognosticate. Cytogenetic and mutational analyses are useful in humans but unavailable for dogs, where diagnosis and classification still rely largely on hematologic and morphologic assessment. The objectives of this study were to apply a classification scheme to myeloid neoplasms and to assess outcome in relation to predictor variables. Keyword search of a laboratory database, application of sequential exclusion criteria, and consensus from 3 reviewers yielded 70 cases of myeloid neoplasia with hematology results, and cytologic (11), histologic (14), or both (45) types of marrow specimens. Based on blast percentage and morphology, 42 cases were classified as MDS and 28 as AML. Dogs with MDS had significantly lower body weights, hemoglobin concentrations and blood blasts, and higher red blood cell size variability and platelet numbers than dogs with AML. Estimates of median survival using Kaplan-Meier curves for dogs with MDS and AML were 384 and 6 days, respectively (P < .001). The instantaneous risk of death for dogs with MDS was approximately 5× lower than that of dogs with AML. Significant predictor variables of survival were body weight, white blood cell count, platelet count, and percent blood blasts (P < .05). Hazard ratios (HRs) derived from best-fitting Cox regression models were 1.043, 0.998, and 1.061 for increased neutrophils, decreased platelets, and increased blood blasts, respectively. Findings from this study suggest that hematologic and morphologic variables are useful to predict outcomes in myeloid neoplasia.

Acute myeloid leukemia (AML) can infiltrate extramedullary tissues, such as the liver, spleen, and lymph nodes and can be difficult to differentiate from lymphoma in cytologic and histologic specimens. Our goal was to identify cytologic features that would support a diagnosis of AML in peripheral lymph node aspirates, for which we used the term extramedullary AML (eAML). Medical records of 23 dogs with a diagnosis of AML and archived lymph node aspirate smears from 2016 to 2024 were reviewed across 4 institutions. Inclusion criteria included ≥50% myeloid blasts plus differentiating myeloid cells in lymph node smears, confirmation of myeloid lineage by flow cytometric analysis, and complete medical records. Peripheral lymphadenopathy was the reason for presentation (9/23, 39%) or was found incidentally on physical examination (14/23, 61%). Most dogs were bi- or pancytopenic (18/23, 78%), with blasts identified in blood smears of 18 dogs (78%). Initial lymph node aspirate interpretations included hematopoietic neoplasia (8/21, 38%), AML (6/21, 29%), lymphoma (5/21, 24%), lymphoid hyperplasia (1/21, 5%), and granulocytic precursor infiltrates (1/21, 5%). On lymph node smear review, cytologic features supporting an eAML were differentiating granulocytes, blasts with myeloid features or promonocytes, dysplastic changes in myeloid cells, and retention of residual lymphocytes. The median survival was 22 days (range = 1-360 days), and 69% of 16 dogs given chemotherapy or glucocorticoids lived for 30 days or more. Our study highlights the importance of hemogram results and lymph node aspirate smear examination for morphologic features of myeloid differentiation to help diagnose eAML in lymph node smears.

Abstract Background The primary objective of this cross-sectional study, conducted in Québec and Bristish Columbia (Canada) between February 2021 and January 2022, was to measure the prevalence of viral RNA in oronasal and rectal swabs and serum antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) amongst cats living in households with at least one confirmed human case. Secondary objectives included a description of potential risk factors for the presence of SARS-CoV-2 antibodies and an estimation of the association between the presence of viral RNA in swabs as well as SARS-CoV-2 antibodies and clinical signs. Oronasal and rectal swabs and sera were collected from 55 cats from 40 households at most 15 days after a human case confirmation, and at up to two follow-up visits. A RT-qPCR assay and an ELISA were used to detect SARS-CoV-2 RNA in swabs and serum SARS-CoV-2 IgG antibodies, respectively. Prevalence and 95% Bayesian credibility intervals (BCI) were calculated, and associations were evaluated using prevalence ratio and 95% BCI obtained from Bayesian mixed log-binomial models. Results Nine (0.16; 95% BCI = 0.08–0.28) and 38 (0.69; 95% BCI = 0.56–0.80) cats had at least one positive RT-qPCR and at least one positive serological test result, respectively. No risk factor was associated with the prevalence of SARS-CoV-2 serum antibodies. The prevalence of clinical signs suggestive of COVID-19 in cats, mainly sneezing, was 2.12 (95% BCI = 1.03–3.98) times higher amongst cats with detectable viral RNA compared to those without. Conclusions We showed that cats develop antibodies to SARS-CoV-2 when exposed to recent human cases, but detection of viral RNA on swabs is rare, even when sampling occurs soon after confirmation of a human case. Moreover, cats with detectable levels of virus showed clinical signs more often than cats without signs, which can be useful for the management of such cases.