Clinical findings and outcome predictors for multinodular pulmonary fibrosis in horses: 46 cases (2009-2019).

BACKGROUND: Prognostic indicators for equine multinodular pulmonary fibrosis (EMPF), an interstitial fibrosing lung disease, are poorly described. HYPOTHESIS/OBJECTIVES: Describe diagnostic findings and outcome predictors for EMPF. ANIMALS: Forty-six adult horses with EMPF. METHODS: Retrospective multicenter case series from 2009 to 2019. Radiographic (n = 27) and ultrasonographic studies (n = 19) from EMPF horses and bronchoalveolar lavage fluid (BALF) cytology from 6 EMPF and 13 asthma cases were independently reviewed and blinded to diagnosis and outcome. Associations between predictor variables and survival were assessed by predictor screening followed by Fisher's exact and Wilcoxon rank sum tests. RESULTS: Primary clinical findings were weight loss (36/46, 78%), increased respiratory effort (33/46, 72%), tachypnea (32/46, 70%), and fever (18/46, 39%). Macrophage atypia was seen in more EMPF than asthmatic horse BALF (67% vs. 8%; P = .02). Equine herpesvirus 5 (EHV-5) was detected in 24 of 30 (80%) and hyperfibrinogenemia in 25 of 28 (89%) cases. Twenty-seven of 46 horses (59%) and 11 of 45 (24%) survived to discharge and to 3 months, respectively. Three-month survival was associated with lower median (range) respiratory rates (30 [24-36] vs. 41 [30-60] breaths per minute; P = .04), and higher BALF lymphocyte:neutrophil ratios (4.7 [1.4-22] vs. 0.47 [0.11-1.9]; P = .01) and blood lymphocyte counts (1.25 [0.93-2.55] vs. 0.90 [0.70-1.24] × 109/L; P = .03). Imaging findings, EHV-5 detection, and corticosteroid treatment were not associated with survival. CONCLUSIONS AND CLINICAL IMPORTANCE: Fever is not a sensitive clinical sign of EMPF. Diagnostic testing should be pursued for horses with increased respiratory rate and effort and weight loss. The prognosis for EMPF horses is poor. Corticosteroid treatment does not improve 3-month survival.

Equine gamma herpesvirus presence and viral load are not associated with equine glandular gastric disease.

OBJECTIVE: To investigate the role of equine herpesvirus-2 (EHV-2) and equine herpesvirus-5 (EHV-5) in equine glandular gastric disease (EGGD) by visualizing and quantifying these gamma herpesviruses in EGGD-affected and normal glandular gastric mucosa of horses. A secondary objective was to describe the histopathological abnormalities in the equine gastric glandular mucosa in horses with EGGD. ANIMALS: 29 horses (n = 21 postmortem and 8 gastroscopy) categorized as normal (11), EGGD (12), or both EGGD and equine squamous gastric disease (6). METHODS: Glandular gastric mucosal samples were collected from horses by gastroscopy or postmortem. Histopathology and in situ hybridization targeting EHV-2 and EHV-5 were performed on grossly normal and abnormal glandular gastric mucosa. The number of in situ hybridization-positive cells per millimeter squared of tissue was calculated. Evaluators were blinded to groups. RESULTS: Glandular gastric tissues from horses without EGGD had higher viral loads in the mucosa than normal or abnormal tissues from EGGD horses. There was no difference in viral loads for EHV-2 or EHV-5 between grossly or endoscopically normal to abnormal gastric tissues within horses with EGGD. Lymphocytic plasmacytic gastritis was the most common histopathological abnormality, with only 3 horses having mucosal disruption (glandular ulcer or erosion). CLINICAL RELEVANCE: Equine gamma herpesviruses are unlikely to play a role in the pathophysiology of EGGD. EGGD is frequently inflammatory with occasional mucosal disruption (ulcer or erosion).

Naturally acquired equine parvovirus-hepatitis is associated with a wide range of hepatic lesions in horses.

Equine parvovirus-hepatitis (EqPV-H) is the causative agent of Theiler's disease, or severe acute hepatic necrosis, in horses. However, it is poorly understood whether EqPV-H is associated with other histologic findings in horses with clinical liver disease. The objective of this study was to examine the prevalence and severity of EqPV-H infections in diagnostic liver samples. Archived formalin-fixed, paraffin-embedded (FFPE) liver samples (n = 98) from Cornell University and University of California, Davis, collected between 2007 and 2022 were evaluated for 15 individual histologic features and by EqPV-H in situ hybridization. EqPV-H was detected in 48% (n = 47) of samples. The most common histologic features of EqPV-H-positive samples included individual hepatocyte death (n = 40, 85%), lobular infiltrates (n = 38, 80%), portal infiltrates (n = 35, 74%), and ductular reaction (n = 33, 70%). Centrilobular necrosis, portal infiltrate, and individual hepatocyte death were positively associated with high viral load. Neutrophil infiltrates, bridging fibrosis, and portal edema were negatively associated with a high viral load. Only 4 of 49 tested samples were positive for equine hepacivirus by polymerase chain reaction (PCR), but the PCR assay was unreliable for FFPE tissues. In summary, this study demonstrates that EqPV-H is common in a variety of liver pathologies and should be considered as a differential diagnosis in cases of hepatitis other than Theiler's disease.

Peripheral Nerve Matrix Hydrogel Promotes Recovery after Nerve Transection and Repair.

BACKGROUND: Nerve transection is the most common form of peripheral nerve injury. Treatment of peripheral nerve injury has primarily focused on stabilization and mechanical cues to guide extension of the regenerating growth cone across the site of transection. The authors investigated the effects of a peripheral nerve matrix (PNM) hydrogel on recovery after nerve transection. METHODS: The authors used rodent models to determine the effect of PNM on axon extension, electrophysiologic nerve conduction, force generation, and neuromuscular junction formation after nerve transection and repair. The authors complemented this work with in vivo and in vitro fluorescence-activated cell sorting and immunohistochemistry approaches to determine the effects of PNM on critical cell populations early after repair. RESULTS: Extension of axons from the proximal stump and overall green fluorescent protein-positive axon volume within the regenerative bridge were increased in the presence of PNM compared with an empty conduit ( P < 0.005) 21 days after repair. PNM increased electrophysiologic conduction (compound muscle action potential amplitude) across the repair site ( P < 0.05) and neuromuscular junction formation ( P = 0.04) 56 days after repair. PNM produced a shift in macrophage phenotype in vitro and in vivo ( P < 0.05) and promoted regeneration in a murine model used to characterize the early immune response to PNM ( P < 0.05). CONCLUSION: PNM, delivered by subepineural injection, promoted recovery after nerve transection with immediate repair, supporting a beneficial macrophage response, axon extension, and downstream remodeling using a range of clinically relevant outcome measures. CLINICAL RELEVANCE STATEMENT: This article describes an approach for subepineural injection at the site of nerve coaptation to modulate the response to injury and improve outcomes.

Prevalence and pathology of equine parvovirus-hepatitis in racehorses from New York racetracks.

BACKGROUND: Theiler's disease, a.k.a. equine serum hepatitis, is a devastating, highly fatal disease of horses. Equine parvovirus-hepatitis (EqPV-H) has been identified as the likely cause of this disease. While the incidence of Theiler's disease is low, the prevalence of EqPV-H DNA in horses is high, with up to 37% in some regions, suggesting that subclinical or persistent infection is common. METHODS: To determine the prevalence and pathogenicity of EqPV-H infection at New York racetracks, DNA was extracted from archived formalin-fixed, paraffin-embedded liver tissues from racehorses submitted for necropsy to the Animal Health Diagnostic Center as part of the New York State Gaming Commission-Cornell University postmortem examination program. A total of 191 liver samples from horses between 2 and 13 years old were evaluated. Extracted DNA was tested for EqPV-H using PCR and gel electrophoresis. PCR-positive samples were further assessed for tissue morphology using histology and detection of viral nucleic acid using in situ hybridization. RESULTS: Forty-two samples were PCR positive (22%). Of those, 31 samples had positive viral nucleic acid hybridization in hepatocytes with 11 samples showing positive hybridization in necrotic hepatocytes associated with inflammatory cells, indicating active hepatitis. Both individual hepatocyte necrosis and hepatitis were positively associated with EqPV-H detection (p < 0.0001 and p = 0.0005, respectively). CONCLUSION: These findings indicate that presence of EqPV-H in the liver and parvoviral-associated hepatitis are prevalent in racehorses from New York racetracks, thus warranting additional studies examining potential associations between EqPV-H infection and racehorse performance.

Nasal transmission of equine parvovirus hepatitis.

BACKGROUND: Equine parvovirus hepatitis (EqPV-H) is highly prevalent and causes subclinical to fatal hepatitis, which can occur in outbreaks. Whereas iatrogenic transmission is well documented, the mode of horizontal transmission is not known. The virus is shed in nasal, oral and fecal secretions, and PO transmission has been reported in a single horse. HYPOTHESIS/OBJECTIVE: Investigate the efficiency of PO and nasal transmission of EqPV-H in a larger cohort. METHODS: Prospective experimental transmission study. Eleven EqPV-H-negative horses were inoculated with 5 × 106 genome equivalents EqPV-H. Serum PCR and serology for EqPV-H were performed weekly and monthly, respectively. Horses first were inoculated PO, and then intranasally 8 weeks later. RESULTS: No horse became viremic or seroconverted within 8 weeks after PO inoculation. After intranasal inoculation, 5 horses became viremic within 6 to 12 weeks and seroconverted within 10 to 19 weeks. After a period without monitoring from 12 to 19 weeks postinoculation, another 5 horses were found to be viremic at 19 to 22 weeks. The second set of 5 horses could have been infected by horizontal transmission from the first 5 because of cohousing. CONCLUSIONS AND CLINICAL IMPORTANCE: We demonstrated that EqPV-H can be transmitted nasally. The prolonged eclipse phase before detectable viremia indicates biosecurity measures to control spread could be impractical.

The history of Theiler's disease and the search for its aetiology.

Theiler's disease (serum hepatitis) may occur in outbreaks or as single cases of acute hepatitis and is often associated with prior administration of equine-origin biologics approximately 4-10 weeks before the onset of clinical signs. Cases have also been described without any prior administration of blood products. The clinical disease has a low morbidity but high mortality and only adult horses are affected. The course of the disease is short, with horses either dying or completely recovering in a few days. Pathology in affected horses is predominantly centrilobular hepatocyte necrosis with mononuclear cell infiltration of the lesser affected periportal regions of the liver. Subclinical cases of the disease also occur. Based on the epidemiology and pathology of the disease, a viral cause, similar to hepatitis B in humans, has long been suspected. This paper reviews both historical and recent findings on Theiler's disease. Reported epidemics of Theiler's disease in the early 1900s are reviewed, along with their similarities to outbreaks of serum hepatitis in humans following yellow fever virus vaccinations in the 1930s and 1940s. Recent metagenomics-based studies to determine the aetiology of Theiler's disease are discussed, along with both clinical and experimental findings supporting equine parvovirus-hepatitis (EqPV-H) as the likely cause of this 100-year-old disease.

Collection and administration of blood products in horses: Transfusion indications, materials, methods, complications, donor selection, and blood testing.

BACKGROUND: Blood transfusion is a lifesaving treatment for horses with acute hemorrhage and other causes of anemia. Transfusions improve oxygen delivery to the tissues via increased blood volume and hemoglobin concentration. Certain aspects of equine blood transfusion are challenging, especially in the field situation, and practitioners may be unfamiliar or feel overwhelmed with the process. An understanding of the indications, materials, methods, and techniques as well as donor selection and possible complications will help practitioners successfully implement blood transfusion in clinical practice. PROCEDURES: Blood transfusion involves several steps including appropriate donor selection, cross-matching, blood collection, and administration, as well as monitoring and handling of transfusion reactions. Guidance for each of these steps are detailed in this review. SUMMARY: Blood transfusion is an effective and often lifesaving treatment for managing diseases of blood loss, hemolysis, and decreased RBC production. Equine practitioners require a thorough understanding of the indications for blood transfusion, the immunological principles behind compatibility testing and transfusion reactions, and the technical skills to aseptically collect and administer blood products KEY POINTS: Equine practitioners require a thorough understanding of the indications for blood transfusion, the immunological principles behind compatibility testing and transfusion reactions, and the technical skills to aseptically collect and administer blood products. Because there are over 400,000 possible equine RBC phenotypes, no universal donor exists, and some blood type incompatibilities are likely between any donor and recipient. Therefore, prior to any blood transfusion, donor and recipient blood should be cross-matched Inadequate delivery of oxygen (Do2 ) to the tissues, resulting from low hemoglobin (Hb) concentration, is the most important indication for blood transfusion Neonatal isoerythrolysis most commonly occurs following an anamnestic response in late gestation; it rarely occurs following a primary exposure because the immune response is not strong enough to produce clinically significant alloantibody titers.

Small but mighty: old and new parvoviruses of veterinary significance.

In line with the Latin expression "sed parva forti" meaning "small but mighty," the family Parvoviridae contains many of the smallest known viruses, some of which result in fatal or debilitating infections. In recent years, advances in metagenomic viral discovery techniques have dramatically increased the identification of novel parvoviruses in both diseased and healthy individuals. While some of these discoveries have solved etiologic mysteries of well-described diseases in animals, many of the newly discovered parvoviruses appear to cause mild or no disease, or disease associations remain to be established. With the increased use of animal parvoviruses as vectors for gene therapy and oncolytic treatments in humans, it becomes all the more important to understand the diversity, pathogenic potential, and evolution of this diverse family of viruses. In this review, we discuss parvoviruses infecting vertebrate animals, with a special focus on pathogens of veterinary significance and viruses discovered within the last four years.

Pathogenesis, MicroRNA-122 Gene-Regulation, and Protective Immune Responses After Acute Equine Hepacivirus Infection.

BACKGROUND AND AIMS: Equine hepacivirus (EqHV) is phylogenetically the closest relative of HCV and shares genome organization, hepatotropism, transient or persistent infection outcome, and the ability to cause hepatitis. Thus, EqHV studies are important to understand equine liver disease and further as an outbred surrogate animal model for HCV pathogenesis and protective immune responses. Here, we aimed to characterize the course of EqHV infection and associated protective immune responses. APPROACH AND RESULTS: Seven horses were experimentally inoculated with EqHV, monitored for 6 months, and rechallenged with the same and, subsequently, a heterologous EqHV. Clearance was the primary outcome (6 of 7) and was associated with subclinical hepatitis characterized by lymphocytic infiltrate and individual hepatocyte necrosis. Seroconversion was delayed and antibody titers waned slowly. Clearance of primary infection conferred nonsterilizing immunity, resulting in shortened duration of viremia after rechallenge. Peripheral blood mononuclear cell responses in horses were minimal, although EqHV-specific T cells were identified. Additionally, an interferon-stimulated gene signature was detected in the liver during EqHV infection, similar to acute HCV in humans. EqHV, as HCV, is stimulated by direct binding of the liver-specific microRNA (miR), miR-122. Interestingly, we found that EqHV infection sequesters enough miR-122 to functionally affect gene regulation in the liver. This RNA-based mechanism thus could have consequences for pathology. CONCLUSIONS: EqHV infection in horses typically has an acute resolving course, and the protective immune response lasts for at least a year and broadly attenuates subsequent infections. This could have important implications to achieve the primary goal of an HCV vaccine; to prevent chronicity while accepting acute resolving infection after virus exposure.

Single-cell resolution landscape of equine peripheral blood mononuclear cells reveals diverse cell types including T-bet+ B cells.

BACKGROUND: Traditional laboratory model organisms represent a small fraction of the diversity of multicellular life, and findings in any given experimental model often do not translate to other species. Immunology research in non-traditional model organisms can be advantageous or even necessary, such as when studying host-pathogen interactions. However, such research presents multiple challenges, many stemming from an incomplete understanding of potentially species-specific immune cell types, frequencies, and phenotypes. Identifying and characterizing immune cells in such organisms is frequently limited by the availability of species-reactive immunophenotyping reagents for flow cytometry, and insufficient prior knowledge of cell type-defining markers. RESULTS: Here, we demonstrate the utility of single-cell RNA sequencing (scRNA-Seq) to characterize immune cells for which traditional experimental tools are limited. Specifically, we used scRNA-Seq to comprehensively define the cellular diversity of equine peripheral blood mononuclear cells (PBMC) from healthy horses across different breeds, ages, and sexes. We identified 30 cell type clusters partitioned into five major populations: monocytes/dendritic cells, B cells, CD3+PRF1+ lymphocytes, CD3+PRF1- lymphocytes, and basophils. Comparative analyses revealed many cell populations analogous to human PBMC, including transcriptionally heterogeneous monocytes and distinct dendritic cell subsets (cDC1, cDC2, plasmacytoid DC). Remarkably, we found that a majority of the equine peripheral B cell compartment is comprised of T-bet+ B cells, an immune cell subpopulation typically associated with chronic infection and inflammation in human and mouse. CONCLUSIONS: Taken together, our results demonstrate the potential of scRNA-Seq for cellular analyses in non-traditional model organisms and form the basis for an immune cell atlas of horse peripheral blood.

Equine pegiviruses cause persistent infection of bone marrow and are not associated with hepatitis.

Pegiviruses frequently cause persistent infection (as defined by >6 months), but unlike most other Flaviviridae members, no apparent clinical disease. Human pegivirus (HPgV, previously GBV-C) is detectable in 1-4% of healthy individuals and another 5-13% are seropositive. Some evidence for infection of bone marrow and spleen exists. Equine pegivirus 1 (EPgV-1) is not linked to disease, whereas another pegivirus, Theiler's disease-associated virus (TDAV), was identified in an outbreak of acute serum hepatitis (Theiler's disease) in horses. Although no subsequent reports link TDAV to disease, any association with hepatitis has not been formally examined. Here, we characterized EPgV-1 and TDAV tropism, sequence diversity, persistence and association with liver disease in horses. Among more than 20 tissue types, we consistently detected high viral loads only in serum, bone marrow and spleen, and viral RNA replication was consistently identified in bone marrow. PBMCs and lymph nodes, but not liver, were sporadically positive. To exclude potential effects of co-infecting agents in experimental infections, we constructed full-length consensus cDNA clones; this was enabled by determination of the complete viral genomes, including a novel TDAV 3' terminus. Clone derived RNA transcripts were used for direct intrasplenic inoculation of healthy horses. This led to productive infection detectable from week 2-3 and persisting beyond the 28 weeks of study. We did not observe any clinical signs of illness or elevation of circulating liver enzymes. The polyprotein consensus sequences did not change, suggesting that both clones were fully functional. To our knowledge, this is the first successful extrahepatic viral RNA launch and the first robust reverse genetics system for a pegivirus. In conclusion, equine pegiviruses are bone marrow tropic, cause persistent infection in horses, and are not associated with hepatitis. Based on these findings, it may be appropriate to rename the group of TDAV and related viruses as EPgV-2.

First report of equine parvovirus-hepatitis-associated Theiler's disease in Europe.

BACKGROUND: Equine parvovirus-hepatitis (EqPV-H) has been proposed as the aetiological cause of Theiler's disease, also known as serum hepatitis. EqPV-H-associated Theiler's disease has not been previously reported in Europe. OBJECTIVES: To determine whether EqPV-H infection was associated with a 2018-2019 outbreak of Theiler's disease in four horses on a studfarm. STUDY DESIGN: Descriptive case series. METHODS: The medical records of four horses from the same farm diagnosed with fatal Theiler's disease were examined retrospectively. Information collected included a clinical history, physical examination findings, tetanus antitoxin exposure, serum biochemistry and necropsy reports. Liver tissue from all four horses was tested for EqPV-H using PCR and in situ hybridisation (ISH) assays. RESULTS: Three of the horses had a history of recent (7-11 weeks) tetanus antitoxin administration. Liver tissue from all four horses tested positive for EqPV-H with PCR. In situ hybridisation revealed a widespread distribution of viral nucleic acid in hepatocytes in one case, and a more sporadic distribution in the remaining three cases. MAIN LIMITATIONS: Case controls were not available from the farm in question given the retrospective nature of analysis. CONCLUSIONS: This case series documents the first reported EqPV-H-associated Theiler's disease in Europe and the first use of ISH to visualise the viral nucleic acid in liver tissues of horses with Theiler's disease.

Agreement of stall-side and laboratory major crossmatch tests with the reference standard method in horses.

BACKGROUND: Crossmatching is used to prevent life-threatening transfusion reactions in horses. Laboratory methods are laborious and technically challenging, which is impractical during emergencies. HYPOTHESIS/OBJECTIVES: Evaluate agreement between a stall-side crossmatch kit (KIT) and a laboratory method (LAB) in horses with known and unknown blood types. ANIMALS: Twenty-four blood-typed and alloantibody-screened healthy adult horses (Aim 1) and 156 adult horses of unknown blood type (Aim 2). METHODS: Prospective, blinded study. Expected positive (n = 35) and negative (n = 36) crossmatches among 24 antibody and blood-typed horses were used to determine sensitivity and specificity of KIT and LAB against the reference method. Agreement in 156 untyped horses was evaluated by reciprocal crossmatch (n = 156). RESULTS: Sensitivity (95% confidence interval [CI]) for LAB and KIT compared with expected reactions was 77.1% (59.9%-90.0%) and 91.4% (77.0%-98.2%), and specificity 77.8% (60.9%-89.9%) and 73.5% (55.6%-87.1%), respectively. The KIT was 100% sensitive for Aa reactions; LAB was 100% sensitive for Qab; and both were 100% sensitive for Ca. Cohen's κ agreement for LAB and KIT with expected positive and negative reactions (n = 71) was moderate (0.55 [0.36-0.74]) and substantial (0.65 [0.47-0.82]), respectively. Agreement was fair comparing LAB with KIT in Aim 1 (0.30 [0.08-0.52]) and in untyped horses in Aim 2 (0.26 [0.11-0.41]). CONCLUSIONS AND CLINICAL IMPORTANCE: Agreement between KIT and LAB with expected reactions was blood type dependent. Performance of both methods depends on blood type prevalence.

Evaluation of two methods to isolate Schwann cells from murine sciatic nerve.

BACKGROUND: Schwann cells (SC) and macrophages play key roles in the response to peripheral nerve injury (PNI). Accurate isolation of such cells is essential for further analyses that can lead to better understanding of the repair process after PNI. Separation of live SC from the injury site without culture enrichment is necessary for targeted gene expression analysis. NEW METHODS: Two flow cytometric techniques are presented for rapid enrichment of live SC and macrophages from injured murine peripheral nerve without the need for culture. RESULTS: SC were isolated by fluorescent activated cell sorting (FACS) using transgenic expression of eGFP in SC, or by exclusion of other cell types collected from the injury site. COMPARISON WITH EXISTING METHOD(S): Gene expression analyses of peripheral nerve repair have commonly used whole nerve lysates. Isolating SC allows more accurate understanding of their specific role in repair. SC are commonly enriched from nerve by culture, however this changes gene expression patterns and limits the utility for transcriptomic analysis. The surface marker p75-NTR has variable expression in different SC phenotypes and during the course of injury and repair. Using p75-NTR for SC isolation might enrich only a subset of SC. More stably expressed lineage markers for SC are intracellular and not suitable for sorting for gene expression. The methods used here avoid the requirement for surface marker labeling of SC. CONCLUSION: Gene expression analysis of sorted cells from both methods showed successful enrichment of SC. Lineage markers such as Map1b, p75-NTR and S100b were enriched in the sorted SC population. SC sorting by eGFP expression showed improved enrichment, particularly of mature myelinating genes, although this could represent sampling of a subset of SC.

What Do We Know About Hepatitis Viruses in Horses?

Theiler disease (serum hepatitis or idiopathic acute hepatic necrosis) has long been suspected to have a viral etiology. Four viruses have been described in association with hepatitis in horses. Further investigation suggests equine pegivirus and Theiler disease-associated virus (a second pegivirus) are neither hepatotropic nor pathogenic. Nonprimate hepacivirus (NPHV) causes subclinical disease in experimental models and has been associated with hepatitis in some clinical cases. Equine parvovirus-hepatitis (EqPV-H) experimentally causes subclinical-to-clinical liver disease and is found in the vast majority of Theiler disease cases. EqPV-H is likely of clinical significance, whereas the significance of NPHV is unknown.

Retrospective evaluation of clinical outcome after chemotherapy for lymphoma in 15 equids (1991-2017).

BACKGROUND: Prognosis associated with lymphoma in horses is poorly characterized, and treatment is often palliative. Long-term outcome after chemotherapy for horses with lymphoma is not well documented. OBJECTIVE: To report long-term outcome of horses with lymphoma treated with chemotherapy. ANIMALS: Fifteen equids. METHODS: Retrospective case series. Medical record search and call for cases on the ACVIM listserv for horses treated with chemotherapy for lymphoma. RESULTS: Fifteen cases with adequate data were identified. Complete remission was achieved in 5 horses (33.3%), partial response was achieved in 9 equids (60%), and stable disease was achieved in 1 horse. Overall response rate was 93.3% (14/15). Overall median survival time was 8 months (range, 1-46 months). Nine horses experienced a total of 14 adverse effects attributable to chemotherapy. Adverse effects were graded according to the Veterinary Cooperative Oncology Group common terminology criteria for adverse events grading system (grade 1 alopecia, n = 2; grade 1 neutropenia, n = 2; grade 1 lymphopenia, n = 3; grade 1 lethargy, n = 1; grade 2 neurotoxicity, n = 1; grade 2 colic, n = 1; grade 1 hypersensitivity, n = 1; grade 2 hypersensitivity, n = 2; grade 5 hypersensitivity, n = 1). Higher grade adverse effects most commonly were associated with doxorubicin administration (n = 4), including 1 horse that died 18 hours post-administration. CONCLUSIONS AND CLINICAL IMPORTANCE: Chemotherapy can be used successfully for treatment of horses with lymphoma. Adverse effects, most commonly mild, occurred in approximately two-thirds of treated horses.

Viral testing of 10 cases of Theiler's disease and 37 in-contact horses in the absence of equine biologic product administration: A prospective study (2014-2018).

BACKGROUND: A novel equine parvovirus (EqPV-H) was recently discovered in the equine liver with Theiler's disease. OBJECTIVES: To determine the prevalence of EqPV-H infection in naturally occurring Theiler's disease cases and in-contact horses in the absence of historical equine biologic product administration. ANIMALS: Ten cases of Theiler's disease from 6 separate properties were included in the study, based on the criteria of acute onset of clinical signs of liver failure with laboratory or histopathologic findings characteristic of Theiler's disease and no history of receiving an equine biologic product within the preceding 4 months. In addition, 37 in-contact horses from 4 of the 6 properties were screened for EqPV-H infection and hepatitis. METHODS: In prospective case series, cases were diagnosed with Theiler's disease by the attending veterinarian and were tested for EqPV-H by PCR of liver or serum. In-contact horses were assessed via serum chemistry and PCR at the attending veterinarian's discretion. Hepatitis was defined as serum gamma-glutamyltransferase activity above reference interval. The association of EqPV-H with hepatitis was determined by Fisher's exact test. RESULTS: Nine of 10 (90%) Theiler's disease cases and 54% of tested in-contact horses were EqPV-H positive. Hepatitis was significantly associated with EqPV-H infection (P = .036). CONCLUSIONS AND CLINICAL IMPORTANCE: Although further study is required to identify EqPV-H as the causative agent of Theiler's disease, EqPV-H appears strongly associated with cases of fatal Theiler's disease and subclinical hepatitis in horses in contact with those cases. The prevalence of EqPV-H infection on affected properties can be high.

Viral testing of 18 consecutive cases of equine serum hepatitis: A prospective study (2014-2018).

BACKGROUND: Three flaviviruses (equine pegivirus [EPgV]; Theiler's disease-associated virus [TDAV]; non-primate hepacivirus [NPHV]) and equine parvovirus (EqPV-H) are present in equine blood products; the TDAV, NPHV, and EqPV-H have been suggested as potential causes of serum hepatitis. OBJECTIVE: To determine the prevalence of these viruses in horses with equine serum hepatitis. ANIMALS: Eighteen horses diagnosed with serum hepatitis, enrolled from US referral hospitals. METHODS: In the prospective case study, liver, serum, or both samples were tested for EPgV, TDAV, NPHV, and EqPV-H by PCR. RESULTS: Both liver tissue and serum were tested for 6 cases, serum only for 8 cases, and liver only for 4 cases. Twelve horses received tetanus antitoxin (TAT) 4-12.7 weeks (median = 8 weeks), 3 horses received commercial equine plasma 6-8.6 weeks, and 3 horses received allogenic stem cells 6.4-7.6 weeks before the onset of hepatic failure. All samples were TDAV negative. Two of 14 serum samples were NPHV-positive. Six of 14 serum samples were EPgV-positive. All liver samples were NPHV-negative and EPgV-negative. EqPV-H was detected in the serum (N = 8), liver (N = 4), or both samples (N = 6) of all 18 cases. The TAT of the same lot number was available for virologic testing in 10 of 12 TAT-associated cases, and all 10 samples were EqPV-H positive. CONCLUSIONS AND CLINICAL IMPORTANCE: We demonstrated EqPV-H in 18 consecutive cases of serum hepatitis. EPgV, TDAV, and NPHV were not consistently present. This information should encourage blood product manufacturers to test for EqPV-H and eliminate EqPV-H-infected horses from their donor herds.

Temporal changes in macrophage phenotype after peripheral nerve injury.

BACKGROUND: Macrophages play a key role in peripheral nerve repair and demonstrate complex phenotypes that are highly dependent on microenvironmental cues. METHODS: We determined temporal changes in macrophage gene expression over time using RNA sequencing after fluorescence-activated cell sorting (FACS) macrophage populations from injured peripheral nerve. We identified key upstream regulators and dominant pathways using ingenuity pathway analysis and confirmed these changes with NanoString technology. We then investigate the effects of extreme polarizers of macrophage phenotype (IL4 and IFNγ) on nerve regeneration. We determined macrophage gene expression in vivo at the site of peripheral nerve injury with NanoString technology, and assessed recovery from sciatic nerve injury by cranial tibial muscle weights and retrograde labeling motor neurons in mice with deletion of IL4 or IFNγ receptors. RESULTS: We demonstrate that IL4R and IFNγR deletions provide complementary responses to polarization, and alter expression of genes associated with angiogenesis and axonal extension, but do not influence recovery from peripheral nerve transection at 8 weeks after repair. CONCLUSIONS: Overall, this study provides a framework to evaluate the phenotype of macrophages over time, and provides a broader and more precise assessment of gene expression changes than has previously been commonly used. This data suggests ways in which polarization may be modulated to improve repair.