Thomas J. Divers’s research while affiliated with Cornell University and other places

OBJECTIVE Evaluate the incidence of Borrelia burgdorferi in cases of equine nuchal bursitis (NB) and investigate the relationship between elevated serum outer surface protein A (OspA) antibodies and the molecular identification of B burgdorferi in bursal tissue or synovial fluid. Additionally, describe clinical cases and compare the histologic changes in NB with and without detection of B burgdorferi . METHODS This was a retrospective multicenter cohort study (2013 to 2022). Medical records from horses with a diagnosis of NB and B burgdorferi PCR testing on NB tissue or synovial fluid were reviewed. The study population included 11 horses with a postmortem diagnosis of NB, 19 horses from the northeastern US with an antemortem diagnosis of B burgdorferi PCR–positive NB, and 15 healthy controls without evidence of NB and unvaccinated for B burgdorferi . Where serum was available, Lyme multiplex assay results were compared with controls and ELISAs targeting individual B burgdorferi antigens were performed. Histologic findings in nuchal bursa tissue were compared between NB cases with and without B burgdorferi PCR detection. RESULTS Serum OspA antibody values in B burgdorferi –positive NB cases (n = 13) were significantly elevated ( P < .001) compared to controls (15), and OspA was the predominant antigen detected by ELISA (8). Histopathology did not vary between NB cases with (n = 9) and without (6) B burgdorferi PCR detection. CONCLUSIONS The presence of B burgdorferi in the nuchal bursa of horses is associated with increased serum OspA antibodies. CLINICAL RELEVANCE The role of B burgdorferi in equine NB may be underestimated, and targeted therapy requires investigation.

The aim of this consensus statement is to summarize and appraise scientific evidence and combine this with the clinical experience of a panel of experts to optimize recommendations on how to recognize and manage kidney disease in horses.

Antemortem diagnosis of neuroborreliosis in horses has been hindered by both the low sensitivity of PCR testing for Borrelia burgdorferi in CSF and the low specificity of serum:CSF ELISA ratios used to determine intrathecal antibody production against the bacterium. PCR testing of the CSF of an adult horse with acute neurologic disease for the B. burgdorferi flagellin gene was negative. However, we enriched B. burgdorferi DNA through nucleic acid hybrid capture, followed by next-generation sequencing, and identified B. burgdorferi in the CSF of the horse, confirming a diagnosis of neuroborreliosis.

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.

Background High serum γ‐glutamyl‐transferase (GGT) activity syndrome in racehorses has been associated with maladaption to exercise. Investigation of affected horses before and immediately after standard exercise may provide critical insight into the syndrome's pathophysiology. Objectives To investigate blood biomarker changes in actively competing racehorses with high GGT activity associated with an exercise challenge. Study design Case–control study. Methods High GGT case (age: 2–3 years) and normal GGT control (age: 2–7 years) pairs (3 Thoroughbred, 4 Standardbred pairs) at least 3 months into their training/racing season were included. Horses with a recent history of high GGT activity (≥50 IU/L) without additional biochemical evidence of liver disease were identified by veterinarians. Horses were tested again in the week prior to a planned exercise challenge to confirm persistent increases in GGT activity. Controls from the same stable with similar training/racing intensity and serum GGT activity ≤36 IU/L were matched with each case. Blood samples were obtained immediately before, 15 and 120 min after exercise. Pre‐exercise serum samples were analysed for baseline select serum chemistries, selenium and vitamin E concentrations. Cortisol concentration and markers of oxidative status were measured in serum or plasma for all time points. Individual serum bile acid and coenzyme Q10 concentrations, plasma lipid mediator (fatty acids, oxylipids, isoprostanes) concentrations and targeted metabolomics analyses were performed using liquid chromatography‐mass spectrometry. Serum viral PCR for equine hepaci‐ and parvovirus was performed in each animal. Results Cases had higher baseline concentrations of total glutathione, taurocholic acid, cortisol and cholesterol concentrations and higher or lower concentrations of specific oxylipid and isoprostane mediators, but there were no case‐dependent changes after exercise. Main limitations Small sample size. Conclusions Results indicated that glutathione metabolism was altered in high GGT horses. Enhanced glutathione recycling and mild cholestasis are possible explanations for the observed differences.

Regulation of renal blood flow is by both extrinsic and intrinsic systems. Intrinsic regulation occurs via the afferent and efferent arterioles and tubuloglomerular feedback mechanisms with activation of the juxtaglomerular apparatus. Mechanisms of acute kidney injury are frequently associated with changes in renal blood flow. Acute tubular necrosis and apoptosis are common in horses following ischemic or toxic insults and in sepsis-associated acute kidney injury. Sepsis-associated renal injury often has a complex mechanism of disease involving both functional and obstructive changes in intrarenal circulation. Acute interstitial nephritis may occur following Leptospira sp infection or can be secondary to tubular necrosis.

Nephrotoxic and hemodynamically mediated disorders are the most common causes of acute renal failure (ARF) in horses and foals. Leptospira spp. is the most common infectious cause of ARF. Initial treatments for ARF include elimination of nephrotoxic drugs, correction of predisposing disorders, and fluid therapy to promote diuresis. Horses and foals with polyuric ARF often have a good prognosis, while those with oliguric or anuric ARF have a guarded to poor prognosis. When fluid therapy is unsuccessful in improving urine production, various drugs treatments have been used in an attempt to increase urine production, but none are consistently effective in converting oliguria to polyuria.

Background Abdominocentesis is commonly used to evaluate the abdominal cavity of the horse. This technique provides valuable diagnostic information as well as the means to monitor patients with abdominal diseases being managed medically and to determine their need for surgical management. Complications are uncommon and include trauma to the gastrointestinal tract or spleen, septic peritonitis, or abdominal wall infection. Procedures This review describes the indications, utility, patient preparation, and instructions for performing abdominocentesis as well as possible complications reported in horses. Step‐by‐step instructions are provided for the two most commonly used abdominocentesis techniques in horses, which include the use of a needle (18 Ga, 3.8 cm [1.5 in]) and a teat cannula (9.5 cm [3.75 in]). Summary Peritoneal fluid collection and fluid analysis can be used to confirm diagnosis of intraabdominal pathology including inflammatory, infectious, neoplastic, obstructive, and bowel strangulation, leading to additional diagnostic and therapeutic plans. Key points Abdominocentesis is useful as a diagnostic procedure in horses suffering from colic, diarrhea, weight loss, or other conditions involving the abdominal cavity and is an integral component of diagnostic testing for colic at referral institutions or in the field. Abdominal fluid collection using an 18‐Ga, 3.8‐cm (1.5‐in) needle is recommended for adult horses because the needle is long enough to penetrate the peritoneal cavity. The teat cannula technique is recommended for use in adult horses, foals, and miniature horses to reduce the risk of enterocentesis, even though this procedure is more traumatic than using an 18‐Ga, 3.8‐cm needle. Ultrasonography of the abdomen is a valuable tool in the assessment of any horse with signs of colic, but it is not essential for performing an abdominocentesis successfully.

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.