A multidisciplinary approach to reduce and refine antimicrobial drugs use for diarrhoea in dairy calves

This study evaluated the impact of a multidisciplinary intervention to reduce and refine antimicrobial drug use for treatment of diarrhoea in dairy calves. The intervention consisted of modification of management practices for disease prevention, health evaluation training of farm staff, implementation of an algorithm directed at antimicrobial therapy for diarrhoeic calves, and monthly farm visits. A combination of retrospective (before intervention period [BP], 1 year) and prospective (immediately after intervention period [AP], 1 year) cohorts were used. Health outcomes measured included incidence of diarrhoea and overall mortality. Antimicrobial treatment rates for diarrhoea and total mass of antimicrobial drugs used at the calf and farm level were also evaluated. Outcomes were assessed using the χ² or Fisher's exact test, and odds ratios and 95% confidence intervals (95% CI) were calculated. Records of 2049 and 2251 calves from 10 farms were available in the BP and AP, respectively. Reduced antimicrobial treatment rates occurred on seven farms (P < 0.01), but not on three farms in the AP. A total of 85% (1303/1573) and 18% (310/1698) of diarrhoeic calves were treated with antimicrobial drugs in the BP and AP (P < 0.001), respectively. There were no differences in the incidence of diarrhoea or mortality between periods. In the AP, the use sulfamethazine and trimethoprim decreased on eight farms, one farm discontinued use of lincomycin and spectinomycin, while two farms discontinued use and one reduced use of cephalosporins. This multidisciplinary approach was effective in reducing antimicrobial drug use for calf diarrhoea on dairy farms without negative impacts on calf health.

Detection of Bovine Coronavirus in Healthy and Diarrheic Dairy Calves

Background

BCoV is identified in both healthy and diarrheic calves, complicating its assessment as a primary pathogen.

Objectives

To investigate the detection rates of bovine coronavirus (BCoV) in feces of healthy and diarrheic calves and to describe the usefulness of a pancoronavirus reverse transcriptase (RT) PCR (PanCoV‐RT‐PCR) assay to identify BCoV in samples of diarrheic calves.

Animals

Two hundred and eighty‐six calves <21 days. Calves with liquid or semiliquid feces, temperature >39.5°C, and inappetence were considered as cases, and those that had pasty or firm feces and normal physical examination were designated as controls.

Methods

Prospective case–control study. A specific BCoV‐RT‐PCR assay was used to detect BCoV in fecal samples. Association between BCoV and health status was evaluated by exact and random effect logistic regression. Fecal (n = 28) and nasal (n = 8) samples from diarrheic calves were tested for the presence of BCoV by both the PanCoV‐RT‐PCR and a specific BCoV‐RT‐PCR assays. A Kappa coefficient test was used to assess the level of agreement of both assays.

Results

BCoV was detected in 55% (157/286) of calves; 46% (66/143), and 64% (91/143) of healthy and diarrheic calves, respectively. Diarrheic calves had higher odds of BCoV presence than healthy calves (OR: 2.16, 95% CI: 1.26 to 3.83, P = 0.004). A good agreement between PanCoV‐RT‐PCR and BCoV‐RT‐PCR to detect BCoV was identified (κ = 0.68, 95% CI: 0.392 to 0.967; P < 0.001).

Conclusions and Clinical Importance

BCoV was more likely to be detected in diarrheic than healthy calves. The PanCoV‐RT‐PCR assay can be a useful tool to detect CoV samples from diarrheic calves.

Characterization of the Fecal Bacterial Microbiota of Healthy and Diarrheic Dairy Calves

BACKGROUND

Neonatal diarrhea accounts for more than 50% of total deaths in dairy calves. Few population-based studies of cattle have investigated how the microbiota is impacted during diarrhea.

OBJECTIVES

To characterize the fecal microbiota and predict the functional potential of the microbial communities in healthy and diarrheic calves.

METHODS

Fifteen diarrheic calves between the ages of 1 and 30 days and 15 age-matched healthy control calves were enrolled from 2 dairy farms. The Illumina MiSeq sequencer was used for high-throughput sequencing of the V4 region of the 16S rRNA gene (Illumina, San Diego, CA).

RESULTS

Significant differences in community membership and structure were identified among healthy calves from different farms. Differences in community membership and structure also were identified between healthy and diarrheic calves within each farm. Based on linear discriminant analysis effect size (LEfSe), the genera Bifidobacterium, Megamonas, and a genus of the family Bifidobacteriaceae were associated with health at farm 1, whereas Lachnospiraceae incertae sedis, Dietzia and an unclassified genus of the family Veillonellaceae were significantly associated with health at farm 2. The Phylogenetic Investigation of Communities Reconstruction of Unobserved States (PICRUSt) analysis indicated that diarrheic calves had decreased abundances of genes responsible for metabolism of various vitamins, amino acids, and carbohydrate.

CLINICAL RELEVANCE

The fecal microbiota of healthy dairy calves appeared to be farm specific as were the changes observed during diarrhea. The differences in microbiota structure and membership between healthy and diarrheic calves suggest that dysbiosis can occur in diarrheic calves and it is associated with changes in predictive metagenomic function.

Comparison of manual and suction pump aspiration techniques for performing bronchoalveolar lavage in 18 dogs with respiratory tract disease

Background

Different aspiration techniques to retrieve bronchoalveolar lavage fluid (BALF) affect sample quality in healthy dogs. Studies evaluating these techniques in dogs with respiratory disease are lacking.

Objectives

To compare sample quality of BALF acquired by manual aspiration (MA) and suction pump aspiration (SPA).

Animals

Eighteen client‐owned dogs with respiratory disease.

Methods

Randomized, blinded prospective clinical trial. Manual aspiration was performed with a 35‐mL syringe attached directly to the bronchoscope biopsy channel and SPA was performed with a maximum of 50 mmHg negative pressure applied to the bronchoscope suction valve using the suction trap connection. Both aspiration techniques were performed in each dog on contralateral lung lobes, utilizing 2 mL/kg lavage volumes per site. Samples of BALF were analyzed by percentage of retrieved infusate, total nucleated cell count (TNCC), differential cell count, semiquantitative assessment of slide quality, and diagnosis score. Data were compared by paired Student's t‐test, Wilcoxon signed‐rank test, chi‐squared test, and ANOVA. Cohen's kappa coefficient was used to assess agreement.

Results

The percentage of retrieved BALF (P = .001) was significantly higher for SPA than MA. Substantial agreement was found between cytologic classification of BALF obtained with MA and SPA (kappa = 0.615). There was no significant difference in rate of definitive diagnosis achieved with cytologic assessment between techniques (P = .78).

Conclusions and Clinical Importance

Suction pump aspiration, compared to MA, improved BALF retrieval, but did not significantly affect the rate of diagnostic success of bronchoalveolar lavage (BAL) in dogs with pulmonary disease.

Effects of chronic acetazolamide administration on gas exchange and acid-base control in pulmonary circulation in exercising horses

REASONS FOR PERFORMING STUDY

Carbonic anhydrase (CA) catalyses the hydration/dehydration reaction of CO(2) and increases the rate of Cl(-) and HCO(3)(-) exchange between the erythrocytes and plasma. Therefore, chronic inhibition of CA has a potential to attenuate CO(2) output and induce greater metabolic and respiratory acidosis in exercising horses.

OBJECTIVES

To determine the effects of Carbonic anhydrase inhibition on CO(2) output and ionic exchange between erythrocytes and plasma and their influence on acid-base balance in the pulmonary circulation (across the lung) in exercising horses with and without CA inhibition.

METHODS

Six horses were exercised to exhaustion on a treadmill without (Con) and with CA inhibition (AczTr). CA inhibition was achieved with administration of acetazolamide (10 mg/kg bwt t.i.d. for 3 days and 30 mg/kg bwt before exercise). Arterial, mixed venous blood and CO(2) output were sampled at rest and during exercise. An integrated physicochemical systems approach was used to describe acid base changes.

RESULTS

AczTr decreased the duration of exercise by 45% (P < 0.0001). During the transition from rest to exercise CO(2) output was lower in AczTr (P < 0.0001). Arterial PCO(2) (P < 0.0001; mean ± s.e. 71 ± 2 mmHg AczTr, 46 ± 2 mmHg Con) was higher, whereas hydrogen ion (P = 0.01; 12.8 ± 0.6 nEq/l AczTr, 15.5 ± 0.6 nEq/l Con) and bicarbonate (P = 0.007; 5.5 ± 0.7 mEq/l AczTr, 10.1 ± 1.3 mEq/l Con) differences across the lung were lower in AczTr compared to Con. No difference was observed in weak electrolytes across the lung. Strong ion difference across the lung was lower in AczTr (P = 0.0003; 4.9 ± 0.8 mEq AczTr, 7.5 ± 1.2 mEq Con), which was affected by strong ion changes across the lung with exception of lactate.

CONCLUSIONS

CO(2) and chloride changes in erythrocytes across the lung seem to be the major contributors to acid-base and ions balance in pulmonary circulation in exercising horses.

Effect of frusemide on transvascular fluid fluxes across the lung in exercising horses

REASONS FOR PERFORMING STUDY

Frusemide (Fru) is widely prescribed for management of racehorses experiencing EIPH. The effect of Fru in the lung appears to be a reduction in transcapillary pressures and inhibition of the erythrocyte anion exchange, which may lead to attenuation of transpulmonary fluid fluxes during exercise.

HYPOTHESIS

Treatment with Fru will attenuate transpulmonary fluid fluxes in horses during high intensity exercise.

METHODS

In a crossover study, 6 race-fit Standardbred horses were treated with 250 mg of Fru i.v. (FruTr) or placebo (Con) 4 h before exercise on a high speed treadmill until fatigue. Arterial and central mixed venous blood, as well as CO(2) elimination and O(2) uptake, were sampled. Volume changes across the lung and transvascular fluid fluxes were calculated from changes in haemoglobin, packed cell volume, plasma protein and cardiac output (Q).

RESULTS

During exercise, Q increased in both Con and FruTr, with Q being significantly lower in FruTr (mean ± s.e. 301.8 ± 8.5 l/min at fatigue) compared to Con (336.5 ± 15.6 l/min) (P<0.01). At rest frusemide had no effect on erythrocyte (J(ER)) and transvascular (J(V-A)) fluid fluxes across the lung. Exercise had a significant effect on J(ER) and J(V-A) (P ≤ 0.02). During exercise, J(ER) (at fatigue 14.6 ± 2.3 l/min and 11.6 ± 2.2 l/min in Con and FruTr, respectively) and J(V-A) (at fatigue 14.9 ± 2.3 l/min and 12.0 ± 2.2 l/min in Con and FruTr, respectively) were not significantly different between Con and FruTr (P = 0.6 and P = 0.8 for J(ER) and J(V-A), respectively).

CONCLUSIONS AND CLINICAL IMPORTANCE

Fru does not have a measurable effect on J(ER) and J(V-A). Cardiac output was reduced in FruTr, suggesting that there were also smaller changes in the capillary recruitment and transvascular transmural hydrostatic pressures; however, this did not effect J(V-A). Therefore, Fru at the dose of 250 mg does not appear to be an effective treatment for regulating pulmonary transvascular forces during exercise in horses.

Immunohistochemical identification of collagen in the equine lung

Recurrent airway obstruction (RAO) in the horse is a disease characterized by reversible bronchoconstriction and by mucus and neutrophil accumulation in the airways. It has been hypothesized that in horses with RAO, remodeling changes occur that are similar to those described in humans with asthma. Although collagen fibrils are present surrounding normal airways, they are a prominent feature of airway remodeling in human asthma with evidence of enhanced collagen III and I fibril deposition. An immunolabeling method was developed to identify collagen I and III in equine lung and to describe the collagen fiber type and distribution within the walls of the noncartilagenous bronchioles. The health status of 14 horses was characterized by clinical respiratory exam, bronchoalveolar lavage cytology, and pulmonary function tests. Following postmortem examination and histological assessment, horses were divided into RAO-affected (n = 4) and nonaffected (n = 10) groups. Eight sections per horse from all lung regions were evaluated histologically. Results of the study showed that collagens I and III were present in the lamina propria and adventitial area of the noncartilaginous bronchioles. There was clear staining differentiation between collagen I or III, airway smooth muscle, and the airway epithelium. Collagen I and III were present in the lamina propria and adventitial areas of the noncartilaginous bronchioles of horses, and there was no significant difference in the relative amount of collagen I and III between this group of RAO-affected and nonaffected horses.

Clara cell secretory protein is reduced in equine recurrent airway obstruction

Horses are prone to recurrent airway obstruction (RAO), an inflammatory lung disease induced by repeated exposure to environmental mold, dust, and bacterial components. Active disease manifests with mucus hyperproduction, neutrophilic inflammation, bronchoconstriction, and coughing. Chronically affected animals have lung remodeling characterized by smooth muscle hyperplasia, collagen deposition, lymphoid hyperplasia, and impaired aerobic performance. Clara cell secretory protein (CCSP) counters inflammation in the lung, hence we hypothesized that CCSP depletion is a key feature of RAO in horses. Recombinant equine CCSP and specific antiserum were produced, and percutaneous lung biopsies were obtained from 3 healthy horses and from 3 RAO-affected horses before and after induction of RAO. CCSP relative gene expression in tissue, as well as protein concentration in lung lavage fluid, was determined. Immunocytochemical analysis, using both light and immunogold ultrastructural methods, demonstrated reduced CCSP staining in lung tissue of animals with RAO. Immunogold label in Clara cell granules was less in animals with chronic RAO than in normal animals, and absent in animals that had active disease. Median lung lavage CCSP concentration was 132 and 129 ng/ml in healthy horses, and 62 and 24 ng/ml in RAO horses before and after challenge, respectively. CCSP lung gene expression was significantly higher in healthy animals than in animals with chronic RAO. Together, these preliminary findings suggest that reduced production of CCSP and subcellular changes in Clara cells are features of chronic environmentally induced lung inflammation in horses.

Arterial calcification in race horses

Calcification of large arteries has been sporadically reported in horses. The pathogenesis is still unknown, but recent studies in humans suggest that this is a regulated biomineralizing process. This study surveyed the prevalence, distribution, and severity of vascular calcification in Thoroughbred and Standardbred racehorses. Histopathologic, ultrastructural imaging, and energy dispersive X-ray elemental analyses were used to examine the lesions. Calcification of the tunica media, predominantly the pulmonary artery, was found in 82% of horses (83/101). Young adult horses (mean [SD] age in years, 4.44 +/- 2.17) of both breeds and sexes were similarly affected. Lesions appeared as white-to-yellowish, hard, and gritty plaques of variable size. On microscopic examination, elastic fibers within the tunica media were thinned, fragmented, and calcified, and surrounded by dense collagen matrix. Elemental analysis showed distinct peaks for calcium and phosphorus, consistent with hydroxyapatite mineral. The frequent occurrence of calcification in the tunica media of large pulmonary arteries of young racing horses indicates the need to investigate its pathogenesis and potential clinical implications.

Effects of chronic acetazolamide administration on fluid flux from the pulmonary vasculature at rest and during exercise in horses

REASONS FOR PERFORMING STUDY

Horses develop high pulmonary pressures during exercise, which force fluid out of pulmonary capillaries. Specific airway diseases in horses, especially those associated with hypoxaemia, hypercapnoea and acidosis may influence pulmonary haemodynamics and pulmonary interstitial fluid equilibrium.

OBJECTIVES

This study was designed to determine fluid flux (J(V-A) l/min) across the lung in exercising horses treated chronically with acetazolamide.

METHODS

Six horses were exercised on a treadmill until fatigue without (Con) and with chronic carbonic anhydrase (CA) inhibition (AczTr) and associated hypercapnoea and acidosis. Carbonic anhydrase inhibition was achieved with administration of acetazolamide (Acz). Arterial and mixed venous blood were sampled, and VCO2 and VO2 measured. Blood volume changes across the lung (deltaBV%) were calculated from changes in plasma protein, haemoglobin and packed cell volume (PCV). Cardiac output (Q) was calculated using Fick principle. J(V-A) across the alveolar-capillary barrier was then quantified based on Q and deltaBV. Variables were analysed using 2-way repeated-measures ANOVA (P<0.05). A significant F ratio was further analysed using Tukey post hoc analysis.

RESULTS

Treatment had a significant effect on J(V-A) (P = 0.002). At rest there was no J(V-A) in Con (0.63 +/- 0.6 l/min) and AczTr (0.84 +/- 0.3 l/min). During exercise Con fluid moved from the pulmonary circulation into the pulmonary interstitium (mean +/- s.e. J(V-A) 9.4 +/- 2.4 l/min). This was different from AczTr (mean +/- s.e. J(V-A) 1.8 +/- 1.9 l/min), where no transvascular fluxes from pulmonary circulation were present during exercise (P = 0.008).

CONCLUSIONS

Chronic Acz treatment with associated hypercapnoea and acidosis affects J(V-A) in lungs of exercising horses. Lung fluid dynamics adapted to hypercapnoea and acidosis with reduction of fluid flow from the pulmonary circulation.

POTENTIAL RELEVANCE

The current data provide comprehensive evidence of in vivo fluid homeostasis in lungs of exercising horses without and with CA inhibition.

Effects of pulmonary abscesses on racing performance of horses treated at referral veterinary medical teaching hospitals: 45 cases (1985-1997)

OBJECTIVE

To determine whether results of physical or radiographic examination or biochemical analyses in adult racehorses with primary lung abscesses were associated with ability to race following treatment.

DESIGN

Multiple-center retrospective study.

ANIMALS

25 Standardbreds and 20 Thoroughbreds.

PROCEDURE

Medical records of horses with a primary lung abscess that were admitted to any of 4 veterinary teaching hospitals were reviewed. Results of physical examination, laboratory testing, and thoracic radiography were reviewed. Racing performance after treatment was compared with performance before illness and with performance of the general population of racehorses of similar age, sex, and breed.

RESULTS

23 of 25 Standardbreds and 13 of 20 Thoroughbreds raced after diagnosis and treatment of a lung abscess. Most horses had a solitary abscess in the dorsal to caudodorsal lung fields. Results of initial physical examination, biochemical analyses, and culture and identification of the microbial isolate were not associated with whether a horse returned to racing. For horses that had raced prior to the illness, race performance after treatment of the lung abscess was not significantly different from performance before the illness.

CONCLUSIONS AND CLINICAL RELEVANCE

On the basis of racing performance in those horses that resumed racing after treatment, long-term residual lung damage did not develop in horses with primary lung abscesses that were treated appropriately. It is not known whether horses that recovered would be more likely to bleed from the site of a prior infection when resuming strenuous exercise and whether lung abscesses contributed to a failure to resume racing.

Bovine herpesvirus 1 (BHV1) seroprevalence in the breeding cattle population of the Veneto region: prospects for the implementation of a control programme

The results of a serological survey for bovine herpes virus (BHV1) antibodies in the breeding cattle population of the Veneto region are presented. The data do not support the hypothesis of an high prevalence of BHV1; on farms where vaccination was not carried out most animals were seronegative, and seropositive animals were generally older. Therefore, when drawing up the guidelines for a control programme, systematic immunization (with glycoprotein E-deleted vaccines) should be restricted only to farms with a high prevalence of BHV1 antibodies and/or with a high risk of BHV1 occurrence; in most unvaccinated farms a 'test and removal' policy appears to be more appropriate in order to rapidly eradicate BHV1 from the entire stock.

In vitro allergen-induced degranulation of pulmonary mast cells from horses with recurrent airway obstruction (heaves)

OBJECTIVE

To determine the capacity of pulmonary mast cells (PMC) to degranulate in response to various potential allergens and other secretagogues in horses with recurrent airway obstruction (heaves) and clinically normal horses before and after exposure to moldy hay.

ANIMALS

5 horses with heaves and 5 clinically normal horses.

PROCEDURES

Heaves was characterized as an increased clinical respiratory score and maximum change in transpulmonary pressure of > 20 cm H2O after exposure. Bronchoalveolar lavage was performed during each period. Washed and resuspended cells were exposed for 20 minutes at 37 C with whole reconstituted freeze-dried preparations of Aspergillus fumigatus, Alternaria tenuis, and Ambrosia elatior, fungal extracts of Aspergillus fumigatus, Alternaria tenuis, and Micropolyspora faeni; A23187; and compound 48/80. Histamine release (HR) was used as a marker of degranulation.

RESULTS

Compared with clinically normal horses, HR was significantly greater from PMC from horses with heaves during remission and exacerbation in response to whole preparations and extracts of Aspergillus fumigatus and whole preparations of Alternaria tenuis. Extracts of Alternaria tenuis caused significantly greater HR from PMC from horses with heaves during exacerbation. Histamine was also released from PMC in response to A23187 and to changes in osmolality of the medium, but only as a result of cell lysis by compound 48/80.

CONCLUSIONS

Increased degranulation of PMC after antigenic challenge may contribute to the pathogenesis of heaves in horses.

CLINICAL RELEVANCE

Strategies for prevention and treatment that attenuate degranulation of PMC may assist in the clinical management of horses with heaves.

Associations between physical examination, laboratory, and radiographic findings and outcome and subsequent racing performance of foals with Rhodococcus equi infection: 115 cases (1984-1992)

OBJECTIVE

To determine whether physical examination, laboratory, or radiographic abnormalities in foals with Rhodococcus equi infection were associated with survival, ability to race at least once after recovery, or, for foals that survived and went on to race, subsequent racing performance.

DESIGN

Retrospective study.

ANIMALS

49 Thoroughbreds and 66 Standardbreds admitted to 1 of 6 veterinary teaching hospitals between 1984 and 1992 in which R equi infection was positively diagnosed.

PROCEDURE

Results of physical examination, laboratory testing, and thoracic radiography were reviewed. Indices of racing performance were obtained for foals that recovered and eventually raced and compared with values for the US racing population.

RESULTS

83 (72%) foals survived. Foals that did not survive were more likely to have extreme tachycardia (heart rate > 100 beats/min), be in respiratory distress, and have severe radiographic abnormalities on thoracic radiographs at the time of initial examination than were foals that survived. Clinicopathologic abnormalities were not associated with whether foals did or did not survive. Forty-five of the 83 surviving foals (54%) eventually raced at least once, but none of the factors examined was associated with whether foals went on to race. Racing performance of foals that raced as adults was not significantly different from that of the US racing population.

CLINICAL IMPLICATIONS

R equi infection in foals is associated with a decreased chance of racing as an adult; however, foals that eventually go on to race perform comparably to the US racing population.

Pulmonary eosinophilia associated with increased airway responsiveness in young racing horses

Horses are known to acquire small airway disease (SAD), an allergen-induced naturally occurring syndrome of reversible obstructive lung disease accompanied by airway hyperresponsiveness and increased inflammatory cell numbers on bronchoalveolar lavage (BAL). This disorder has received scant attention in young racehorses. The purpose of the present report was to examine the effect of BAL eosinophilia in young racehorses on clinical examination, BAL, hematology, airway responsiveness, and on pulmonary function at rest and after a standardized exercise challenge. Five (3 males, 2 females; age 2.6 +/- 0.9 years) with a history of respiratory compromise and BAL eosinophil differential count > 5% and 6 controls (4 males, 2 females; age 3.5 +/- 1.0 years) training and performing to expectation with normal BAL cell differential (eosinophils < 1%) were studied. Respiratory system clinical examination was performed and expressed as a clinical score. Arterial blood gas measurements, CBC, and pulmonary function testing were performed at rest. Pulmonary mechanics measurements were repeated 1 hour and 20 hours after a standardized treadmill exercise challenge. Incremental histamine inhalation challenge was performed and the concentration of histamine effecting a 35% decrease in dynamic compliance (PC35CDyn) was determined. Significant differences were noted between and controls with regard to clinical score (P = .01), blood eosinophils (P = .04), BAL cell count (P = .04), BAL macrophage differential (P = .04), PC35CDyn (P = .008), and tidal volume and respiratory rate at 20 hours following exercise challenge (P = .05). We conclude that pulmonary eosinophilia and airway hyperresponsiveness are manifest in some young horses without overt airway obstruction at rest. We speculate that these may be early events in the natural progression of heaves.

Evaluation of an in vitro degranulation challenge procedure for equine pulmonary mast cells

Pulmonary mast cells (PMC) are important components of the inflammatory process in equine allergic lung diseases such as heaves. Very little, however, is known of the degranulation kinetics of these cells and thus, their pathophysiologic role remains largely speculative. The purpose of this study was to develop a repeatable protocol for in vitro equine PMC degranulation. Five mature horses (sex: 2 M, 3 F; age: 8.8 +/- 6.5 y), historically free of pulmonary disease and normal on clinical respiratory examination, arterial blood gas analysis, pulmonary mechanics testing and histamine inhalation challenge, were studied. Bronchoalveolar lavage was performed on 4 separate occasions, at least 2 d apart, in a different lung lobe on each occasion. The lavage fluid was concentrated by centrifugation. Cells were resuspended in modified HEPES/Tyrode, assessed for viability by Trypan blue exclusion, and PMC concentration determined. Cell inocula containing 30,000 PMC were incubated with 10(-8) to 6 x 10(-5) M A23187. Cells were then separated by centrifugation and histamine release (HR) was determined by fluorometric assay. The procedure was readily performed and yielded sufficient PMC for 30 to 60 inocula per lavage. Maximal HR (34.4 +/- 16.1%) was obtained with 10(-5) M A23187. The degranulation process was largely complete by 20 min but cell lysis was negligible. The challenge was repeatable within horse and produced a mean coefficient of variability of 23.0% following 20 min incubation with 10(-5) M A23187. We conclude that equine PMC degranulation can be repeatably performed in vitro and speculate that this protocol may be useful in further studies on the pathophysiology and treatment of equine allergic lung diseases.

Pathogenesis and clinical signs of equine herpesvirus-1 in experimentally infected ponies in vivo

Equine herpesvirus-1 (EHV-1) causes respiratory disease, neonatal death, abortion and neurologic disease. The main purpose of this study was to identify viral antigen in respiratory tract samples by immunoperoxidase staining. Six pony foals were selected on the basis of demonstrating seronegativity to EHV-1 by virus neutralization and housed in isolation. They were infected experimentally by administering EHV-1 nebulized ultrasonically through a face mask. Successful infection was clinically apparent as each of the foals had febrile responses, nasal discharge, and enlarged submandibular lymph nodes. Sporadic coughing was also heard. EHV-1 was isolated from nasopharyngeal swabs of 4/6 ponies and seroconversion was demonstrated in all foals. Bronchoscopic examination of the large airways revealed hyperemia. The incidence of recovery of Actinobacillus suis from nasopharyngeal swabs increased initially, with recovery of Streptococcus zooepidemicus isolates predominating at 3 wk post-infection. Cytology brushes were used to sequentially sample the respiratory tract of the infected ponies at the nasopharynx, mid-trachea and the mainstem bronchus. Bronchoalveolar lavage provided lung cells. Immunocytochemistry techniques were applied to both types of samples to locate EHV-1 antigen. Indirect immunoperoxidase staining of samples utilizing monoclonal antibodies specific for EHV-1 demonstrated viral antigen associated with cellular debris, primarily in the nasopharyngeal samples on days 3-9 post-infection.

Small airway disease as a vanguard for chronic obstructive pulmonary disease

Equine allergic small airway disease is a highly prevalent respiratory condition among the stabled horse population. With the assistance of new diagnostic tools such as bronchoalveolar lavage, the condition can be recognized in young performing horses. The pathophysiological and clinical features resemble an earlier stage of chronic obstructive pulmonary disease as determined by the appearance of specific inflammatory cells. Although environmental management is paramount in controlling the disease, proper selective therapeutic regimens are as important to reduce the concurrent inflammation and to reduce exacerbations of the disease.

Techniques for sampling the respiratory tract of horses

Field diagnostic tests for respiratory diseases are constantly evolving. With each new application, equine patients with sinusitis, acute and chronic bacterial and fungal pneumonia SAID, chronic obstructive pulmonary disease, pleuropneumonia or poor performance are managed with greater proficiency. All of these problems can be investigated adequately in the field. This article is a guide to sampling techniques relevant to the ambulatory clinician.

Study of the duration and distribution of equine influenza virus subtype 2 (H3N8) antigens in experimentally infected ponies in vivo

The purpose of this experiment was to study the duration and distribution of equine influenza virus in actively infected ponies over a 3 wk period. Pony foals (6-8 mo old) were infected experimentally by nebulizing equine influenza subtype-2 virus ultrasonically through a face mask. Successful infection was clinically apparent as each of the foals (n = 6) had a febrile response, a deep hacking cough and mucopurulent nasal discharge for 7 to 10 d. The virus was isolated from nasopharyngeal swabs of all the ponies 3 and 5 d after infection and all the ponies seroconverted to the virus. Samples were taken from the nasopharynx, mid-trachea and the mainstem bronchus with cytology brushes through an endoscope as well as from bronchoalveolar lavage fluid. On days 3 to 7 post-infection, ciliacytophtorea (the presence of cilia and ciliated plates separated from columnar epithelial cells) was recognized on routine cytological stain. Indirect immunoperoxidase staining utilizing polyclonal antibodies demonstrated viral antigen in intact and fragmented ciliated epithelial cells and in fragments of ciliated plates. The infected cells and cell fragments were particularly evident on days 3 and 5 post-infection in the nasopharynx, mid-trachea and mainstem bronchus and on days 3 to 7 post-infection in the bronchoalveolar lavage samples. On days 7 and 21 post-infection, viral antigen was identified in vacuoles of alveolar macrophage-like cells collected by bronchoalveolar lavage. It can be concluded from this study that equine influenza virus can infect not only the upper airways but also the bronchial epithelium and that viral antigen can persist up to 21 d post-infection.

Frequency dependence of forced oscillatory respiratory mechanics in horses with heaves

The effect of measurement frequency on respiratory mechanics was investigated in six horses with reversible allergic airway disease. Total respiratory impedance was measured at 1.5, 2.0, 3.0, and 5.0 Hz by using the forced oscillation technique with the horses in remission, after acute antigenic challenge producing clinical heaves, and with heaves but after the administration of 2 mg fenoterol by inhalation. The slopes of the magnitude (magnitude of Zrs) and real part (R) of total respiratory impedance over the frequency range 1.5-3 Hz changed significantly after antigenic challenge and fenoterol. The ratio of R at 2 Hz to R at 3 Hz, however, discriminated better among the three conditions. Compliance and resonant frequency (calculated by using a three-element model) changed significantly after antigenic challenge and fenoterol, but inertance did not. We concluded that horses with heaves showed frequency dependence of R and (magnitude of Zrs) at frequencies up to 3 Hz and that parameters derived from a three-element model were useful indicators of small airway obstruction in the horse.

Use of a virulence-associated protein based enzyme-linked immunosorbent assay for Rhodococcus equi serology in horses

An enzyme-linked immunosorbent assay (ELISA) was developed against Rhodococcus equi using Triton X-114 detergent extracted whole cell material, in which the virulence associated protein (VapA) predominated. Enzymelinked immunosorbent assay titres corresponded to antibody reacting with VapA on Western blots. There was considerable variation in antibody titres of nonimmunised mares and in the time when the colostrally derived antibody of their foals had declined to low or undetectable titres. In general, antibodies in foals declined to their lowest levels at age 4-8 weeks. Seroconversion occurred in foals age 8-10 weeks, but the precise time depended on maternal titre and the month in which the foal was born. Foals reaching age 8 weeks in late summer showed more marked seroconversion than foals born earlier. The ELISA was used to follow the response to immunisation with the same Triton X-114 extracted material. Six mares immunised before parturition with the antigen in aluminium hydroxide adjuvant developed high titres, up to > 102,400 and transferred them to their foals through colostrum. Their foals responded to immunisation with 0.5-1.0 mg antigen 3, 5, 7 and 9 weeks after birth. Antibody titres following immunisation with similar dosage reached up to > 102,400 in a separate group of foals of nonimmunised mares. Nonvaccinated control foals seroconverted at age 6-8 weeks. The VapA based ELISA is useful to follow the course of natural infection with R. equi or immunisation with VapA based antigen.

Pulmonary function measurements during repeated environmental challenge of horses with recurrent airway obstruction (heaves)

OBJECTIVES

To evaluate the degree of reproducibility in clinical variables, blood gas measurements, and lung function variables, and the changes in these variables caused by exposure to moldy hay in naturally sensitized and control horses.

PROCEDURE

The magnitude of variation in arterial blood gas and pulmonary function measurements were evaluated in a model of naturally acquired heaves. Horses with heaves and similarly aged control horses were studied prior to moldy hay challenge and again after the horses with heaves manifested clinical signs of airway obstruction. This cycle of testing was repeated 3 times to determine the variation of the before and after challenge measurements. Variables evaluated for repeatability included: clinical score; arterial O2 and CO2 tensions; pulmonary function variables, such as breathing rate (f), tidal volumes, and flow rates; lung resistance (RL); dynamic compliance; and work of breathing (Wb).

RESULTS

Before challenge, significant differences observed between control horses and horses with heaves included clinical score, expiratory flow rate at near-end expiration, RL, and Wb. After exposure to moldy hay, variables measured in control horses were largely unchanged. However, in the afflicted horses, significant changes were observed for clinical score, arterial O2 and CO2 tensions, breathing rate, peak tidal inspiratory and expiratory flow rates, dynamic compliance, RL, and Wb, compared with prechallenge values and with control horses' postchallenge values. Analysis of the data revealed few statistically significant differences between repeats of challenges.

CONCLUSION

Horses afflicted with heaves manifest airway obstruction that can be measured in repeatable fashion.

Effect of 5-hydroxytryptamine type-2 receptor blockade on pulmonary function in calves with experimentally induced Pasteurella haemolytica pneumonia

OBJECTIVE

To evaluate a 5-hydroxytryptamine type-2 receptor antagonist, metrenperone (MET), in alleviating respiratory distress associated with experimentally induced Pasteurella haemolytica pneumonia in feedlot calves.

DESIGN

Double-blind controlled clinical trial.

ANIMALS

30 healthy 6- to 8-month-old Hereford-type calves (250 to 450 kg).

PROCEDURE

Initial measurements were made of rectal temperature (RT), arterial blood gas (ABG) tensions, and pulmonary mechanics. Calves were then infected with P haemolytica in logarithmic phase of growth by intratracheal inoculation. 18 hours later, determination of RT and ABG tensions, and pulmonary function testing were repeated and calves were selected for inclusion in the study on the basis of having 2 of the following: respiratory rate > 50 breaths/min, RT > 40 C, or PaO2 > 20 mm of Hg below the baseline value. MET (0.1 mg/kg of body weight, IM) or an equivalent vehicle dose was then administered. RT, ABG, and pulmonary mechanics measurements were repeated at 0.5, 1, 2, 3, 4, 6, 12, and 24 hours after treatment. Calves were then euthanatized, and gross necropsy scoring and histologic examination were performed on the lungs.

RESULTS

Infection with P haemolytica caused significant increases in RT and respiratory rate, and reduction in PaO2, PaCO2, and tidal volume 18 hours after inoculation. MET-treated calves and significantly reduced rectal temperature between 1 and 12 hours, compared with vehicle-treated calves. In addition, MET-treated calves had reduced respiratory rate with concomitantly increased tidal volume between 0.5 and 2 hours after treatment, compared with vehicle-treated calves. Necropsy revealed acute lobar bronchopneumonia in all 30 calves, but there was no difference in necropsy score between treatment groups.

CONCLUSIONS AND CLINICAL RELEVANCE

MET may have an antipyretic effect on calves with pneumonia caused by P haemolytica. Its influence on pulmonary mechanics was minimal however, and it did not induce lung lesions in the short term.

Effect of sodium cromoglycate on light racehorses with elevated metachromatic cell numbers on bronchoalveolar lavage and reduced exercise tolerance

Some young horses with clinical signs of small airway disease demonstrate increased metachromatic cell numbers on bronchoalveolar lavage. The purpose of this study was to determine the effect of sodium cromoglycate treatment on clinical signs, bronchoalveolar lavage cytology and bronchoalveolar lavage histamine parameters in these horses. Twelve racehorses (age: 3.4 +/- 1.6 years) with a history of respiratory embarrassment at exercise, clinical signs of obstructive airway disease and bronchoalveolar lavage metachromatic cell differential greater than 2% were selected. Horses were randomly assigned to receive either 200 mg sodium cromoglycate or saline placebo nebulized twice daily for 7 days. A clinical respiratory score was assigned and bronchoalveolar lavage was performed on each animal on days 0 and 7. Measurements were made of the following bronchoalveolar lavage fluid parameters: total nucleated cell concentration, differential cell percentage and concentration, supernatant and lysate histamine concentration, lysate: supernatant histamine ratio and metachromatic cell histamine content. Between the two evaluation periods, sodium cromoglycate treated horses demonstrated an improvement in respiratory score (P = 0.01) and a stabilizing of metachromatic cell histamine content (P = 0.04) when compared with placebo treated horses. We concluded that sodium cromoglycate is effective for the treatment of small airway disease in this population of young racehorses although the pharmacodynamics of this drug in the horse require further investigation.

The rapid and effective administration of a beta 2-agonist to horses with heaves using a compact inhalation device and metered-dose inhalers

The purpose of the study was to administer therapeutic aerosol generated by metered-dose inhalers to horses exhibiting clinical signs of heaves using a compact inhalation device developed for human medicine. It was fitted to a custom face mask in order to study the effect of an inhaled beta 2-agonist, fenoterol. Pulmonary function testing was performed on six horses following an acute exacerbation of heaves, characterized by tachypnea, wheezes, crackles, and spasmodic cough. Horses inhaled fenoterol in 1 mg increments administered as one 200 microgram puff every 5-10 s with the recording of data 5 min after the cessation of drug inhalation. A significant effect of fenoterol was shown for maximum change in transpulmonary pressure, dynamic compliance, lung resistance, and work of breathing, and the wheezes and crackles disappeared when auscultation was performed at the end of the test. This study demonstrates a novel, highly effective method for the rapid administration of inhaled medication in horses.

Sensitivity and specificity of bronchoalveolar lavage and protected catheter brush methods for isolating bacteria from foals with experimentally induced pneumonia caused by Klebsiella pneumoniae

One indication for referral of horses to veterinary hospitals is for diagnosis of the microbiologic cause of pneumonia, particularly when the initial treatment fails. Although endoscopic methods have long been available for microbiologic sample collection, accuracy of these methods under these conditions have not been studied in detail. We compared the bacteria isolated from samples obtained by bronchoalveolar lavage (BAL) with those obtained by protected catheter brush (PCB) from foals with unilateral pneumonia induced by inoculation with Klebsiella pneumoniae. As part of previously described clinical trials, foals were administered antimicrobial therapy IM (n = 15) or vehicle IM (n = 7), and collection of distal airway secretion samples was conducted during the treatment period. Sensitivity and specificity of the sample collection methods were assessed by comparison of the isolates from BAL or PCB samples with isolates from tissue of the inoculated lung lobe, which was the most severely affected lung region. Sensitivity and specificity of BAL for recovery of K pneumoniae (challenge strain) and Streptococcus zooepidemicus (common secondary pathogen) was 90 and 69%, respectively, compared with 76 and 85%, respectively, for the PCB method. Sensitivity was significantly (P = 0.03) higher for BAL (100%) than for PCB (69%) for recovery of K pneumoniae (P = 0.03) from lungs. However, difference in the sensitivity of these methods for recovery of S zooepidemicus was not significant. In conclusion, BAL was a more reliable method for recovery of bacteria from the lungs in chronically infected foals that received antimicrobial treatment.

Microbiologic changes during antimicrobial treatment and rate of relapse of distal respiratory tract infections in foals

Despite the high incidence of distal respiratory tract infection of undetermined cause on farms, to our knowledge, the microbiologic effects of conventional antimicrobial treatment for this condition have not been studied. We evaluated the possible pathogenic role of bacterial isolates from the distal airways of foals with clinical respiratory tract disease, by correlating changes in their numbers (increase or decrease) with clinical, endoscopic, and pulmonary cytologic signs of disease resolution during treatment with antimicrobial drugs. We also determined qualitative changes in in vitro antimicrobial susceptibility of bacterial isolates after 7 days of treatment and relapse rate of foals. Significant (P < 0.05) decrease in the numbers of an isolate in the airways was considered strong evidence of a pathogenic role in this disease syndrome. Foals with endoscopically confirmed distal respiratory tract infection (DRTI; n = 65) were selected at random for treatment (n = 56) or nontreatment (n = 9), and bronchial lavage specimens were cultured and evaluated cytologically before and after 7 days of treatment with trimethoprim-sulfamethoxazole (TMS) and a beta-lactam drug (penicillin, ampicillin, or sulbactam-ampicillin), the standard treatment in all foals. The effect of treatment was to abruptly reduce the clinical (nasal discharge, cough, adventitious lung sounds) and cytologic signs of airway infection. Severity of disease in nontreated foals, however, did not change or did worsen over time. Reduction in the frequency and numbers of Streptococcus zooepidemicus isolated during treatment supported a causal role for this organism in the clinical syndrome observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical and endoscopic study to estimate the incidence of distal respiratory tract infection in thoroughbred foals on Ontario breeding farms

Respiratory tract infections are prevalent in foals, yet the frequency with which the distal airways are affected in clinical episodes of respiratory tract disease has not been evaluated to our knowledge. The objective of the study was to determine the incidence of distal respiratory tract infection (DRTI) in foals on a sample of Thoroughbred breeding farms (n = 10) in Ontario. In a pilot study, clinical criteria commonly used to select foals for antimicrobial treatment (detection of abnormal lung sounds, plus nasal discharge, cough, fever, tachypnea, and/or lethargy) were found to segregate foals with and without endoscopically confirmed DRTI. Mucopurulent exudate and bronchial erythema were observed more frequently (P < 0.005), bronchial lavage total cell count and neutrophil concentration were significantly (P < 0.005) higher, and intracellular cocci were recovered significantly (P < 0.01) more often from bronchial lavage samples of affected foals (n = 8) than of controls (n = 8). These clinical criteria were used to identify cases in a cohort of Thoroughbred foals (n = 219) from May 1 to October 30, 1991. Case morbidity adjusted for clustering was 82 +/- 5% (95% confidence limits, 72 to 92%). Most (74%) episodes of clinical DRTI were detected in July and August, and equal numbers were detected before (53%) and after (47%) weaning of foals. Of 178 cases, 66 (48%) were selected at random for endoscopy and bronchial lavage. Grade-II pharyngeal lymphoid hyperplasia was observed commonly (60% of foals); auditory tube diverticulum (guttural pouch) discharge was observed in 18 of 86 (21%) foals, and guttural pouch infection was confirmed in 6 of 7 foals examined endoscopically.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of microbiologic flora with clinical, endoscopic, and pulmonary cytologic findings in foals with distal respiratory tract infection

Undifferentiated distal respiratory tract disease (nasal discharge, cough, pneumonia) in foals (1 to 8 months old) is a burdensome economic problem on breeding farms; yet, the infective agents associated with these episodes have not been well described. Possible causes of these episodes of illness were investigated by culturing specimens of proximal and distal airways of clinically diseased foals (n = 101), prior to any treatment, for aerobic and anaerobic bacteria and viruses (rhinoviruses, equine arteritis virus, equine herpesvirus subtype 1 [EHV-1], influenza virus, and adenovirus). Pairs of sera (n = 47) were examined for antibodies to influenza A virus, equine subtypes 1 and 2, EHV-1, and adenovirus antigens, and sera obtained from foals during acute infection were examined for antibodies (by agar gel immunodiffusion [AGID]) to equi factor antigens of Rhodococcus equi. Viruses were not isolated from the proximal (swab) or distal (bronchial lavage) airway specimens in foals, and only 2 of 47 randomly selected foals seroconverted to EHV-1. Serotiters to the other viruses were low and frequently decreasing between samples, which was compatible with maternally derived antibody. Streptococcus zooepidemicus was the predominant isolate from bronchial lavage specimens (88/101 cases), accompanied by alpha-hemolytic streptococci (8 cases), Bordetella bronchiseptica (13 cases), Staphylococcus epidermidis (9 cases), and other organisms in lesser frequency. Only Str zooepidemicus was recovered significantly (P < 0.05) more often in cases than in controls. The AGID test was found useful to detect foals with presumed exposure to R equi, but positive tests results did not correspond well with bacterial culture results; positive AGID results were recorded in 34% of culture-negative foals.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of exercise on the cardiovascular and respiratory systems of heavy turkeys and relevance to sudden death syndrome

The cardiorespiratory response to walking exercise was studied in 14-to-18-week-old male and female heavy turkeys. Blood pressure, electrocardiograms, respiratory rate, body temperature, blood gases, and electrolytes were measured at rest and after exercise at two different room temperatures. After exercise, systolic, diastolic, and mean blood pressures decreased, and heart rate and body temperature increased, while a severe lactic acidosis developed, in both sexes and at both room temperatures. Fifty-four percent of the turkeys developed arrhythmias, mostly a transient post-exercise sinus arrhythmia of no clinical significance. Changes in electrolytes were clinically insignificant. Blood gases remained within normal limits, demonstrating adequate gas-exchange and pulmonary capability. Within the limits of this study, the cardiac capacity of the heavy turkey in response to exercise appeared very limited. The pathogenesis of sudden death syndrome of turkeys is still unknown, but cardiovascular changes occurring after exercise could be severe enough to cause death.

Effect of exercise on cardiac output and other cardiovascular parameters of heavy turkeys and relevance to the sudden death syndrome

The cardiovascular response to treadmill exercise was studied in 14-to-18-week-old male and female heavy turkeys. Arterial blood pressure, cardiac output, body temperature, and heart rate were measured before and during each period of exercise. Total peripheral resistance, stroke volume, and stroke index were calculated from those parameters. Systolic, diastolic, and mean blood pressures significantly decreased during exercise. Cardiac output increased during exercise in males and females by 64% and 23%, respectively, while total peripheral resistance fell by approximately 40% in both sexes. Exercise had no significant effect on stroke volume and stroke index. The cardiac functional capacity of the heavy turkey in response to mild exercise appears very limited. This failure of the cardiovascular system to adequately respond to increased metabolic needs suggests that hemodynamic failure is a major component in the pathogenesis of sudden death syndrome of turkeys.

Serological titers to bovine herpesvirus 1, bovine viral diarrhea virus, parainfluenza 3 virus, bovine respiratory syncytial virus and Pasteurella haemolytica in feedlot calves with respiratory disease: associations with bacteriological and pulmonary cytological variables

Acute and convalescent serum samples were taken from 59 calves with signs of respiratory disease (cases) and 60 clinically normal animals (controls) during their first month in the feedlot. Sera were analyzed for antibodies to bovine parainfluenza 3 (PI3) virus by hemagglutination inhibition, to bovine viral diarrhea (BVD) virus, bovine respiratory syncytial (BRS) virus and bovine herpesvirus 1 (BHV1) by virus neutralization, and to Pasteurella haemolytica by indirect agglutination (PhIA) and cytotoxin neutralization (PhCN) tests. There was minimal evidence of serological activity to BHV1. Serological activity to the other agents occurred commonly and the prevalence of acute titers and their mean values was similar in case and control groups. Mean convalescent PI3 and P. haemolytica (PhIA) titers were higher in controls than cases (p < 0.01) but, otherwise, convalescent titers did not differ between groups. The incidence of seroconversion was similar in both groups for all agents except for PI3 virus which was more frequent in controls than cases (p < 0.0001). There was a positive association between PhIA and CN seroconversion and isolation of P. haemolytica from bronchoalveolar lavage (BAL) fluid (p < 0.1). The measure of agreement (kappa) between seroconversion with the P. haemolytica PhIA and PhCN tests was 0.51. Bacteriological and cytological evaluations of the respiratory tract were made using BAL. No associations were evident between serological titers and pulmonary cytology. A multivariate logistic analysis was used to evaluate associations between disease status and serological, bacteriological and cytological data. Cases were positively associated with the presence of neutrophils and Pasteurella multocida in BAL fluid and negatively associated with PI3 virus and PhIA seroconversion.

Changes in the bacterial flora of the upper and lower respiratory tracts and bronchoalveolar lavage differential cell counts in feedlot calves treated for respiratory diseases

Serial nasopharyngeal swab and bronchoalveolar lavage cultures were used to estimate changes in the bacterial flora of the respiratory tracts of calves during the first month after arrival in the feedlot. Bronchoalveolar lavage (BAL) differential cell counts served to evaluate pulmonary inflammatory changes during this period. Two groups of calves were studied, one consisting of clinically normal controls (n = 60), the other, of cases (n = 59) which received treatment for respiratory disease (penicillin +/- trimethoprimsulfadoxine). A variety of organisms, including Pasteurella multocida, Pasteurella haemolytica, Haemophilus somnus, Mycoplasma bovis and Mycoplasma bovirhinis, were present in the upper and lower airways of both groups during the postarrival period. With the exception of M. bovis, an overall decline in the prevalence of these organisms was observed during the course of the study. In cases, there was a marked decrease in the number of Pasteurella spp. and H. somnus isolates immediately following treatment. For the Pasteurella spp., however, this effect was shortlived as they often appeared to recolonize the respiratory tract within eight days of terminating antimicrobial therapy. Treatment did not appear to affect the frequency of isolating M. bovis. Its prevalence, in both groups of calves, increased to levels approaching 100% during the course of the study. All Pasteurella spp. isolates were tested for susceptibility to several commonly used antimicrobials. Resistance was only evident among P. haemolytica isolated from cases and in every instance this was to a combination of penicillin, ampicillin and tetracycline. Significantly more isolates were resistant after treatment than before. There were BAL differential cell count abnormalities indicative of inflammation in both cases and controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of sulbactam plus ampicillin for treatment of experimentally induced Klebsiella pneumoniae lung infection in foals

Efficacy of sulbactam, a beta-lactamase inhibitor, in combination with ampicillin, was evaluated for treatment of experimentally induced pneumonia caused by beta-lactam-resistant Klebsiella pneumoniae. Infection was experimentally induced in 18 healthy weanling foals that were randomly allocated to 3 treatment groups: sulbactam plus ampicillin (S/A, 3.3 and 6.6 mg/kg of body weight, respectively), ampicillin (6.6 mg/kg), or vehicle only. Foals were treated daily for 7 days; the observer was unaware of treatment status. Compared with ampicillin and vehicle, treatment with S/A resulted in a statistically significant (P less than 0.05) decrease in severity of pneumonia, with regard to bronchoalveolar lavage cytologic findings (decreased total cell and neutrophil numbers, and increased lymphocyte numbers) and extent of macroscopic lesions in lung tissue of the noninoculated regions. Marked trends toward improvement of S/A-treated foals were observed for quantitative results of bacteriologic culture of bronchoalveolar lavage fluid samples (P less than 0.07), macroscopic pathologic features of the whole lung (P less than 0.1), and histopathologic variables (P less than 0.07), compared with ampicillin- and vehicle-treated foals. Treatment effects were not observed for radiographic, hematologic, and blood gas abnormalities that resulted from infection. In conclusion, the combination of sulbactam plus ampicillin was found to have synergistic effects in vivo, to reduce the extent and severity of experimentally induced gram-negative lung infection in foals.

Cytological findings in bronchoalveolar lavage fluid from feedlot calves: associations with pulmonary microbial flora

Samples obtained by bronchoalveolar lavage (BAL) were used to evaluate pulmonary cytology in 59 feedlot calves with clinical signs of respiratory disease (cases) and 60 clinically normal comparison calves (controls). Many calves in both case and control groups had inflammatory changes in the lower respiratory tract, as determined by changes in proportions in the BAL differential cell count. Approximately 35% of cases and 40% of controls showed a normal differential cell count. It therefore appeared that the criteria used to select cases for treatment, which were similar to those often used in the field, were poor predictors of lower respiratory tract disease. A positive association was found between an increased proportion of neutrophils in BAL fluid and isolations of Pasteurella multocida and Mycoplasma bovis from BAL fluid.

The microbial flora of the respiratory tract in feedlot calves: associations between nasopharyngeal and bronchoalveolar lavage cultures

The upper and lower respiratory tracts of 59 feedlot calves with clinical signs of naturally occurring respiratory disease (cases) and 60 comparison (control) animals were cultured before treatment, using nasopharyngeal swabs (NPS) and bronchoalveolar lavage (BAL). The most prevalent organisms were Pasteurella multocida and Mycoplasma bovis. Isolations of P. multocida from NPS and BAL fluid were found to be significantly associated with morbidity (p less than or equal to 0.05), but the frequency with which other organisms were isolated from the nasopharynx and lungs was similar in cases and controls. There was evidence of moderate agreement between NPS and BAL isolates at the individual calf level using the kappa statistic, (range of kappa values = 0.47-0.61) but the variability of the kappa statistics was large. Therefore, in an individual calf NPS cultures did not accurately predict BAL cultures. The NPS and BAL culture results were quite similar at the group level, however.

Evaluation of a guarded bronchoscopic method for microbial sampling of the lower airways in foals

A novel method to reduce contamination of the bronchoscope during microbial sampling of the lower airways of foals was evaluated. Methylene blue (MB) was used as a nasopharyngeal dye marker to assess the relative contamination from the upper airways of bronchoalveolar lavage (BAL) specimens obtained by standard bronchoscopy (SB) and a "guarded" bronchoscopic method (GB). For GB, a clear sterile cellulose sheath was fitted over the bronchoscope in an effort to protect the endoscope tip and channel from contamination. Methylene blue was detected visually in seven of eight BAL samples from foals following SB, but in none of the samples recovered by GB (p less than 0.001). Significantly less MB was detected in BAL by spectrophotometry in the GB group as well (p less than 0.02). The GB was next employed to study the microbial flora in the lower airways of healthy weaned foals (n = 30). Bacteria were isolated from 29 of 30 (97%) BAL samples, and in moderate or large numbers from 26 of 30 (87%) of the foals. Potential pathogens, including Bordetella bronchiseptica, Streptococcus zooepidemicus, Staphylococcus aureus, Mycoplasma felis and Streptococcus pneumoniae, were cultured from the lower airways of foals. In conclusion, the bronchoscope and bronchoalveolar lavage specimens were readily contaminated by a dye marker placed in the nasopharynx of foals, and the degree of contamination was significantly reduced by sheathing the endoscope. This contamination during bronchoscopy may obscure the interpretation of isolates from BAL specimens from foals, which may possess a bacterial flora in the lower airways without cytological evidence of inflammation.

Patent ductus arteriosus in a Holstein calf: A two-dimensional and Doppler echocardiographic study of the ductus arteriosus and validation

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