Joanne Hewson

Thoracic Ultrasonography and Bronchoalveolar Lavage Fluid Analysis in Holstein Calves with Subclinical Lung Lesions

Background Thoracic ultrasonography (US) and bronchoalveolar lavage fluid (BALF) analysis are antemortem methods used to identify the lung lesions associated with bovine respiratory disease (BRD). Accuracy of US and the cell distributions in BALF have not been characterized in calves with subclinical disease. Objectives To evaluate the accuracy of US and BALF and describe BALF characteristics in calves with subclinical lung lesions. Animals Twenty‐five Holstein calves, 1–12 weeks old. Methods In this prospective study, calves with low respiratory scores underwent US, BALF and postmortem examination (normal US, n = 5; comet‐tails, n = 5; consolidation, n = 15). Bronchoalveolar lavage fluid was collected and analyzed for total and differential cell counts. Lung lesions were assessed by gross and histopathologic examination. Data were analyzed using nonparametric methods and relative risk analysis. The accuracy of US and BALF were estimated relative to postmortem examination. Results The sensitivity and specificity of US for detecting lung lesions was 94% (95% CI, 69–100%) and 100% (95% CI, 64–100%), respectively. A cut‐point of ≥4% BALF neutrophils was associated with the highest BALF sensitivity and specificity, 81% (95% CI, 56–94%) and 75% (95% CI, 36–95%). The presence of consolidation on US increased the risk of having a BALF neutrophil proportion ≥4% (RR, 3.9; 95% CI, 1.13–13.45; P = .003). Conclusions and Clinical Importance Ultrasonography accurately detects lung lesions in calves with subclinical disease. Clinicians should use a cut‐point of ≥4% BALF neutrophils to diagnose subclinical respiratory disease.

Development of a live, attenuated, potential vaccine strain of R. equi expressing vapA and the virR operon, and virulence assessment in the mouse.

Pneumonia caused by Rhodococcus equi remains a significant problem in foals. The objective of this study was to develop a safe and efficacious attenuated strain of R. equi for eventual use in oral immunization of foals. The approach involved expression of vapA in a live, virulence plasmid-negative, strain of R. equi (strain 103-). PCR-amplified fragments of the vapA gene, with and without the upstream genes virR, orf5, vapH, orf7 and orf8 (orf4-8), were cloned into a shuttle vector pNBV1. These plasmids, named pAW48A and pAWVapA respectively, were electroporated into strain 103-. The presence of the recombinant vectors in the attenuated strain (103-) and the integrity of the inserted genes were confirmed, and both constructs expressed VapA. The virulence of the two strains was compared to that of wild type R. equi 103+ and negative controls by their intravenous inoculation into mice, followed by examination of liver clearance 4 days later. Mice inoculated with R. equi 103-, 103-/pAWVapA and 103-/pNBV1 completely cleared infection, whereas strain 103-/pAW48A persisted in 47% of mice.

Characteristics of respiratory tract disease in horses inoculated with equine rhinitis A virus.

OBJECTIVE To develop a method for experimental induction of equine rhinitis A virus (ERAV) infection in equids and to determine the clinical characteristics of such infection. ANIMALS 8 ponies (age, 8 to 12 months) seronegative for antibodies against ERAV. PROCEDURES-Nebulization was used to administer ERAV (strain ERAV/ON/05; n = 4 ponies) or cell culture medium (control ponies; 4) into airways of ponies; 4 previously ERAV-inoculated ponies were reinoculated 1 year later. Physical examinations and pulmonary function testing were performed at various times for 21 days after ERAV or mock inoculation. Various types of samples were obtained for virus isolation, blood samples were obtained for serologic testing, and clinical scores were determined for various variables. RESULTS ERAV-inoculated ponies developed respiratory tract disease characterized by pyrexia, nasal discharge, adventitious lung sounds, and enlarged mandibular lymph nodes. Additionally, these animals had purulent mucus in lower airways up to the last evaluation time 21 days after inoculation (detected endoscopically). The virus was isolated from various samples obtained from lower and upper airways of ERAV-inoculated ponies up to 7 days after exposure; this time corresponded with an increase in serum titers of neutralizing antibodies against ERAV. None of the ponies developed clinical signs of disease after reinoculation 1 year later. CONCLUSIONS AND CLINICAL RELEVANCE Results of this study indicated ERAV induced respiratory tract disease in seronegative ponies. However, ponies with neutralizing antibodies against ERAV did not develop clinical signs of disease when reinoculated with the virus. Therefore, immunization of ponies against ERAV could prevent respiratory tract disease attributable to that virus in such animals.

Comparison of continuous infusion with intermittent bolus administration of cefotaxime on blood and cavity fluid drug concentrations in neonatal foals

Healthy neonatal foals were treated with cefotaxime by bolus (40 mg/kg i.v. q6h for 12 doses; n=10) or by infusion (loading dose of 40 mg/kg i.v. followed by continuous infusion of a total daily dose of 160 mg/kg per 24 h for 3 days; n=5). Population pharmacokinetics was determined, and concentrations in cavity fluids were measured at steady state (72 h). Highest measured serum drug concentration in the bolus group was 88.09 μg/mL and minimum drug concentration (C(min)) was 0.78 μg/mL at 6-h postadministration (immediately before each next dose), whereas infusion resulted in a steady-state concentration of 16.10 μg/mL in the infusion group. Mean cefotaxime concentration in joint fluid at 72 h was higher (P=0.051) in the infusion group (5.02 μg/mL) compared to the bolus group (0.78 μg/mL). Drug concentration in CSF at 72 h was not different between groups (P=0.243) and was substantially lower than serum concentrations in either group. Insufficient data on pulmonary epithelial lining fluid were available to compare the methods of administration for cefotaxime in this cavity fluid. Results support continuous drug infusion over bolus dosing in the treatment for neonatal foal septicemia to optimize time that cefotaxime concentration exceeds the minimum inhibitory concentration of common equine pathogens.

Laboratory and Postmortem Diagnosis of Bovine Respiratory Disease

Pathologic and laboratory investigations are essential when identification of the specific cause of bovine respiratory disease is needed. Considerations for planning a diagnostic investigation include the goals of the inquiry, the potential impact of the diagnosis, the plausible causes based on the clinical and epidemiologic appearance, and the relative merits of the available diagnostic strategies. This review uses 4 cases to outline different approaches to laboratory diagnosis. The postmortem examination is described, along with the patterns and gross appearance of lesions, considerations for effective sampling from appropriately selected animals, and reasons for discrepant or negative laboratory test results.

Impact of isoflupredone acetate treatment on clinical signs and weight gain in weanling heifers with experimentally induced Mannheimia haemolytica bronchopneumonia

OBJECTIVE To characterize the impact of Mannheimia haemolytica infection on feed intake and weight gain in feedlot heifers and to evaluate the clinical efficacy of isoflupredone acetate administered in combination with oxytetracycline. ANIMALS 96 weanling heifers in a research feedlot facility. PROCEDURES Bronchopneumonia was induced by intrabronchial infusion of M haemolytica. Control heifers underwent a sham procedure. Infected heifers were treated with oxytetracycline alone or in combination with isoflupredone acetate (OXY-ISO) or with nothing. Clinical variables were recorded daily for 7 days following disease induction, and feedlot performance indices were measured over a 12-week period. RESULTS Infection caused a reduction in dry-matter intake and average daily gain (ADG) in heifers that received no treatment. Oxytetracycline treatment alone did not prevent reductions in feed intake and ADG during the first week after infection was induced, whereas OXY-ISO treatment did prevent these reductions. Treatment with OXY-ISO also resulted in faster clinical improvement. No significant differences were evident between the oxytetracycline and OXY-ISO groups with respect to dry-matter intake or ADG throughout the study period. CONCLUSIONS AND CLINICAL RELEVANCE Isoflupredone acetate appeared to be a useful clinical adjunct to treatment with oxytetracycline in cattle with acute M haemolytica bronchopneumonia.

Gelatinous Marrow Transformation and Hematopoietic Atrophy in a Miniature Horse Stallion

Gelatinous marrow transformation, or serous atrophy of bone marrow fat, has been noted in livestock, laboratory animals, and wildlife in association with an inadequate plane of nutrition, inanition, or intoxication. This is a report of gelatinous marrow transformation and hematopoietic marrow atrophy in a 5-year-old miniature horse stallion. The horse had oral malformations leading to poor food assimilation and emaciation. A bone marrow biopsy obtained to investigate persistent anemia and leukopenia showed hematopoietic atrophy and replacement of fat with a granular extracellular substance, which stained with alcian blue, consistent with acidic mucopolysaccharide content. Surgical correction of the dental abnormalities resulted in improved food assimilation, weight gain, and resolution of cytopenias. In humans, gelatinous bone marrow transformation and hematopoietic atrophy are commonly associated with malnutrition from anorexia nervosa and other causes. The cause of hematopoietic atrophy is unknown but may relate to a nonsupportive marrow microenvironment and inadequate hematopoietic substrate availability. Similar pathogenic mechanisms were suspected in this horse.

Systematic Review of the Diagnostic Accuracy of Haptoglobin, Serum Amyloid A, and Fibrinogen versus Clinical Reference Standards for the Diagnosis of Bovine Respiratory Disease.

Background Bovine respiratory disease (BRD) is a worldwide animal health concern especially in feedlot, dairy, and veal calves. One of the greatest challenges is the absence of a gold standard for achieving an accurate antemortem diagnosis. Various blood markers, including the acute‐phase proteins (AAP), have been proposed as potential valuable tools for BRD diagnosis. Objectives To perform a systematic review of the literature to assess the accuracy of selected APP (haptoglobin [Hp], serum amyloid A [SAA], and fibrinogen [Fb]) as diagnostic tools for cattle with naturally occurring BRD when compared with clinical reference standards of diagnosis. Methods This review was performed with eligible studies selected from CAB Abstract and MEDLINE from 1946 to 2015, as well as the “gray literature.” Methodological quality of included studies was assessed using the QUADAS‐2 tool developed for diagnostic accuracy studies. The accuracy parameters sensitivity (Se) and specificity (Sp) were obtained from the articles or through contact with the authors when not directly reported. Results A total of 314 studies were identified, from them, 23 met inclusion criteria as diagnostic studies for naturally occurring BRD. Quality of studies showed high risk of bias for case selection (70% of articles) and unclear risk of bias for index test (65%), reference standard (74%), and flow and timing (61%). There were high concerns regarding applicability for case selection (61% of studies) and reference standards used for defining BRD (48%). The concerns regarding index test application were low (83% of the studies). Only 4–8 studies could be included in the meta‐analysis for each APP. No pooled estimates or pooled accuracy measurements were performed due to the low number of studies and multiple differences between studies, including reference standard definitions. Conclusions and Clinical Importance On the basis of these findings, it is not possible to make conclusions regarding the accuracy of APP for BRD diagnosis. The reporting of accuracy of APP for BRD detection is inconsistent among studies. Recommendations to improve capability for future meta‐analyses in this area include reporting studies on diagnostic tests following the Standard for the Reporting of Diagnostic Accuracy Studies (STARD), as well as trying to standardize BRD definition across future studies.

Acute Leukemia in Horses

Leukemia is broadly divided into acute and chronic lymphocytic and myeloid types based on the proportion of blasts, morphology of cells, and expression of specific antigens on neoplastic cells. Classifying leukemia in horses can be challenging if blasts predominate and since few antibodies to identify cell types are available. The objective of this study was to describe in detail the clinical and pathologic features of acute leukemia in horses. Twelve horses ranging from 0.2 to 25.9 years of age were diagnosed with acute leukemia. Six cases were classified as acute lymphocytic leukemia (ALL) based on predominance of blasts, lack of granulocytic or monocytic differentiation, and detection of CD3, CD20, and/or CD79a antigens by immunohistochemistry. Six other cases were classified as acute myeloid leukemia (AML) with myelomonocytic (n = 4), basophilic (n = 1), and eosinophilic (n = 1) differentiation based on > 20% bone marrow blasts and partial leukocytic differentiation. Reactivity with antibodies to Iba-1/AIF-1, CD172a, and CD163 was determined for all cases of AML. Eleven horses had thrombocytopenia, 10 had neutropenia, 8 had anemia, all had blasts on blood films, and none had leukocytosis. Ten horses had increased serum acute phase proteins. Bone marrow cellularity ranged from 30% to 100%, and the proportion of blasts ranged from 80% to 100% and 30% to 60% in ALL and AML, respectively. Horses were severely ill at diagnosis and euthanized within days or weeks. Unique features of acute leukemia in horses compared to other species were variable lymphocyte antigen expression (ALL) and frequent inflammation (ALL and AML).

Respiratory Disease: Diagnostic Approaches in the Horse.

Evaluation of the upper and lower respiratory tract of horses requires strategic selection of possible diagnostic tests based on location of suspected pathologic lesions and purpose of testing and must also include consideration of patient status. This article discusses the various diagnostic modalities that may be applied to the respiratory system of horses under field conditions, indications for use, and aspects of sample collection, handling, and laboratory processing that can impact test results and ultimately a successful diagnosis in cases of respiratory disease.