Antibiotic prophylaxis of lower respiratory tract contamination in horses confined with head elevation for 24 or 48 hours

Objective To evaluate the administration of procaine penicillin prior to or during confinement with head elevation as a means of reducing the associated accumulation of inflammatory lower respiratory tract secretions and increased numbers of bacteria within the lower respiratory tract of confined horses. Design and Procedure Two experiments were conducted to evaluate the efficacy of different dose rates and dosing frequencies. In experiment A a single low dose (15,000 IU/kg) of procaine penicillin was administered to four horses immediately prior to confinement with head elevation for 48 hours. The systemic leucocyte response, gross and cytologic characteristics of transtracheal aspirate and bacterial numbers in lower respiratory tract samples were compared with corresponding samples from two horses confined with heads elevated but not given penicillin. The efficacy of higher dose rates (20,000 IU/kg and 40,000 IU/kg) given before and during confinement with heads elevated for 24 hours was evaluated in experiment B. Results Treatment with procaine penicillin had no effect on the systemic leucocyte response or on the accumulation of inflammatory lower respiratory tract secretions at any of the dosing schedules evaluated. The number of bacteria isolated from trans-tracheal samples was reduced at 12 hours for treated horses in experiment A and at 24 hours for experiment B. β-haemolytic Streptococcus spp were not isolated from treated horses in either experiment. Bacterial species isolated from treated horses were predominantly Pasteurella and/or Actinobacillus spp, however, members of the family Enterobacteriaceaé and a Staphylococcus sp were isolated from treated horses. One treated horse in experiment A developed clinically apparent pulmonary disease. Conclusions The prophylactic administration of penicillin before or during confinement did not reliably reduce bacterial numbers or prevent the accumulation of purulent lower respiratory tract secretions in horses confined with their heads elevated. Numbers of β-haemolytic Streptococcus spp were reduced following treatment, suggesting that the repeated administration of procaine penicillin may have some merit as part of a strategy to prevent transport-associated respiratory disease. However, methods directed at minimising the duration of confinement with head elevation, augmentation of the clearance of accumulated secretions and prompt identification of animals in which airway inflammation has extended to the pulmonary parenchyma remain the best ways of minimising transport-associated respiratory disease.     

Bacterial infection of the lower respiratory tract in 34 horses

OBJECTIVE: To investigate associations between the bacteriology and aspects of history, clinical presentation, outcome and pathology of lower respiratory tract disease of 34 horses. PROCEDURE: Detailed aerobic and anaerobic bacteriological investigations were performed on clinical specimens from horses with pneumonia, lung abscessation and necrotic pneumonia with or without pleurisy in an attempt to identify those bacteria that might contribute to the initiation and progression of infection. RESULTS: Bacteria were cultured from 33 of the 34 horses. In ten cases, only aerobic/facultatively anaerobic isolates were cultured while aerobic/facultatively anaerobic bacteria and obligately anaerobic bacteria were isolated in the other 23 cases. Moderate to large numbers of anaerobic bacteria were isolated only when the estimated duration of illness was at least five days. Bacteria were not cultured from 12 of the pleural fluid samples but were always cultured from pulmonary samples (either transtracheal aspirates from live horses or pulmonary lesions at necropsy). Streptococcus equi subsp zooepidemicus was isolated in the three cases where only one bacterial species was cultured. In the other 30 cases, multiple species were isolated. These included most often and in greatest numbers, Streptococcus equi subsp zooepidemicus, Pasteurellaceae, Escherichia coli, anaerobic cocci, Eubacterium fossor, Bacteroides tectum, Prevotella heparinolytica, Fusobacterium spp, and pigmented members of the genera Prevotella and Porphyromonas. Aerobic/facultatively anaerobic organisms were isolated from 97% of horses, while obligately anaerobic organisms were cultured from 68% of horses. CONCLUSION: There was no association between the isolation of any specific bacterium and the outcome of disease. However, obligately anaerobic bacteria (such as anaerobic cocci, Bacteroides tectum, P heparinolytica and Fusobacterium spp) and the facultatively anaerobic species Escherichia coli, were recovered more commonly from horses that died or were euthanased than from those that survived. There was an association between failure of horses to recover from pleuropneumonia and delay in diagnosis and initiation of treatment.     

Respiratory diseases and their effects on respiratory function and exercise capacity

Given that aerobic metabolism is the predominant energy pathway for most sports, the respiratory system can be a rate‐limiting factor in the exercise capacity of fit and healthy horses. Consequently, respiratory diseases, even in mild forms, are potentially deleterious to any athletic performance. The functional impairment associated with a respiratory condition depends on the degree of severity of the disease and the equestrian discipline involved. Respiratory abnormalities generally result in an increase in respiratory impedance and work of breathing and a reduced level of ventilation that can be detected objectively by deterioration in breathing mechanics and arterial blood gas tensions and/or lactataemia. The overall prevalence of airway diseases is comparatively high in equine athletes and may affect the upper airways, lower airways or both. Diseases of the airways have been associated with a wide variety of anatomical and/or inflammatory conditions. In some instances, the diagnosis is challenging because conditions can be subclinical in horses at rest and become clinically relevant only during exercise. In such cases, an exercise test may be warranted in the evaluation of the patient. The design of the exercise test is critical to inducing the clinical signs of the problem and establishing an accurate diagnosis. Additional diagnostic techniques, such as airway sampling, can be valuable in the diagnosis of subclinical lower airway problems that have the capacity to impair performance. As all these techniques become more widely used in practice, they should inevitably enhance veterinarians' diagnostic capabilities and improve their assessment of treatment effectiveness and the long‐term management of equine athletes.     

Effect of single bouts of moderate and high intensity exercise and training on equine peripheral blood neutrophil function

The effects of single bouts of moderate (30 to 40 per cent VO(2)max) and high (115 per cent VO(2)max) intensity exercise on equine peripheral blood leucocyte function were evaluated by determining neutrophil phagocytosis and oxidative burst activity before and after treadmill exercise and training. Prior to all exercise tests, the possible effect of diurnal variation was evaluated in samples obtained from four resting horses. Subsequently eight horses underwent moderate and high intensity exercise protocols and then commenced a 17-week training period. High intensity exercise tests were repeated in week 10, after 7 weeks of endurance training, and in week 17, after a further 6 weeks of high intensity training. Time of sampling had a significant effect on neutrophil function for resting, untrained horses. Prior to training, moderate intensity exercise was associated with improved neutrophil phagocytosis and oxidative burst activity. High intensity exercise was associated with transient impairment of these responses. A similar reduction was not demonstrable following high intensity exercise in weeks 10 or 17 of training. Neutrophil function in week 17 was suppressed at all sampling times relative to results obtained in week 10, suggesting that high intensity training may have been associated with a general reduction in neutrophil function.     

Cytology of the lower respiratory tract in horses: An updated review

The diagnosis of respiratory diseases in horses can be difficult due to the nonspecific nature of the clinical signs, which overlap between the different diseases. Cytological examination of the respiratory secretions is a helpful diagnostic tool that, when combined with clinical features and other diagnostic techniques, has the potential to improve diagnostic accuracy significantly. This review article should help readers to become familiar with the cytology of the normal respiratory tract and with the cytopathological abnormalities associated with common respiratory disorders in horses.     

Assessment of dynamic upper respiratory tract function in the equine athlete

Dynamic upper respiratory tract (URT) obstructions occur commonly in the equine athlete. During the past 25 years, veterinary diagnostic capabilities have improved greatly with the ability to perform endoscopy during exercise and thus to visualise upper airway function during various types of exercise. After correctly reproducing and diagnosing an URT obstruction, the veterinary surgeon must consider the functional significance of the endoscopic findings for that individual athlete. This is the third paper in this series and focuses on the diagnosis of URT obstructions, their relationship to the exercise test and their functional significance.     

Evaluation of peripheral blood neutrophil function in tumor‐bearing dogs

Background: Peripheral blood neutrophils of untreated human cancer patients have been shown to have normal, increased, and decreased phagocytic activity, killing capacity, and/or oxidative burst activities. Objectives: The objectives of this study were to evaluate oxidative burst and phagocytic activities of peripheral blood neutrophils from tumor‐bearing dogs before therapy and compare them with neutrophil function of healthy control dogs. Methods: Heparinized whole blood was obtained from dogs with high‐grade lymphoma (n=23), sarcoma (n=13), or carcinoma (n=11), and healthy control dogs (n=11) for flow cytometric evaluation of oxidative burst and phagocytic activities. Percentage of bursting cells and amount of oxidative burst activity were determined after stimulation with phorbol 12‐myristate 13‐acetate (PMA) or Escherichia coli. Percentage of phagocytic cells and amount of phagocytic activity were determined after incubation with fluorescent E. coli. Results: Compared with control dogs, dogs with sarcoma (P=.004) and carcinoma (P=.05) had a lower percentage of neutrophils exhibiting oxidative burst activity after stimulation with PMA. Phagocytic activity was significantly lower in dogs with sarcomas compared with control dogs (P<.0001) and dogs with lymphoma (P=.01). Conclusions: Untreated carcinomas and sarcomas in dogs may suppress the percentage of neutrophils capable of oxidative burst when stimulated by PMA. Furthermore, sarcomas also may suppress the amount of phagocytic activity per neutrophil. Until further studies can be performed, the clinical significance of these findings is unknown.     

褪黑素对内毒素血症山羊肝细胞线粒体呼吸功能的影响

将48只健康山羊随机分为4组：对照组（A组）、内毒素（LPS）组（B组）、内毒素＋褪黑素（LPS＋MT）组（C组）、褪黑素（MT）组（D组）,在处理后第3 h和6 h提取肝细胞线粒体,采用Clark氧电极技术测定线粒体呼吸控制率（RCR）、磷氧比值（P/O）、氧化磷酸化效率（OPR）的变化,探讨了MT对LPS诱导的山羊内毒素血症机体线粒体呼吸功能的影响。结果显示,内毒素组山羊在第3 h和6 h的RCR、P/O、OPR显著低于对照组（P〈0.05）;应用褪黑素后,即内毒素＋褪黑素组第3 h的肝细胞线粒体RCR、P/O、OPR明显升高（P〈0.05）;褪黑素组第3 h的RCR明显高于对照组（P〈0.05）,而褪黑素组第3 h的P/O、OPR与对照组差异不显著（P〉0.05）。证实,山羊内毒素血症时线粒体的呼吸功能明显下降,褪黑素对肝细胞线粒体呼吸功能具有一定的保护作用。     

Histomorphology of the lower respiratory tract in the Indian crested porcupine (Hystrix indica)

The Indian crested porcupine (Hystrix indica) (ICP) is widely distributed in Asia; however, compared with other rodents, little is known about the structures of its respiratory system. The aim of this study was to evaluate the histomorphology of the lower respiratory portion of the ICP to provide a basis for the identification of the normal structure of this organ. The larynx, trachea and lungs of four carcasses of adult Indian crested porcupines (two males and two females) were dissected and fixed in 10% neutral-buffered formalin. The gross anatomy and histology of all specimens were evaluated. A macroscopic evaluation showed unique structures in the ICP respiratory system, including the presence of a chamber-like structure at the origin of the bronchi and a difference in epiglottis shape between males and females. Histologically, the stratified squamous epithelium covered the epiglottis and arytenoid cartilage, and the pseudostratified ciliated columnar epithelium covered the internal part of the thyroid and cricoid cartilages. Histomorphological studies showed a few goblet cells in the tracheal epithelium. In the bronchi and larger bronchioles, pseudostratified ciliated columnar epithelia were observed. Bronchi were surrounded by segments of cartilage. Distal bronchioles had a simple cuboidal/columnar epithelium with club (Clara) cells, lacked cartilaginous tissue in their walls and had a complete smooth muscle layer. These results revealed histomorphological differences between the ICP and other rodents.     

Recovery of Moraxella ovis from the bovine respiratory tract and differentiation of Moraxella species by tDNA-intergenic spacer PCR

The purpose of the present study was to identify Moraxella (M.)—like organisms recovered from calves suffering from respiratory disease down to species level by means of tDNA-intergenic spacer length polymorphism analysis (tDNA-PCR), and to perform antimicrobial susceptibility testing of these isolates using an agar dilution technique. A total of 16 isolates originating from 12 unrelated occasions were identified as Moraxella ovis, and tDNA fingerprinting showed clear delineation from other Moraxella species. The minimal inhibitory concentrations (in μg/mL) for 90% of the investigated isolates were ≤0.03 for ampicillin; 0.25 for ceftiofur; 0.5 for oxytetracycline; 8 for gentamicin; 64 for spectinomycin; 0.5/9.5 for the combination trimethoprim-sulfonamides; 4 for erythromycin; 8 for tilmicosin; 1 for florfenicol and 0.125 for enrofloxacin.     

Equitation and exercise factors affecting dynamic upper respiratory tract function: A review illustrated by case reports

The importance of undertaking appropriate exercise tests for the diagnosis of dynamic upper respiratory tract (URT) obstructions has been previously documented. Dynamic URT collapse is usually most severe during peak exercise; however, there are occasions when an URT collapse appears more severe during the immediate recovery period. In addition, equitation factors such as head and neck flexion and factors relating to the bit and bridle may induce or exacerbate dynamic URT collapse. The purpose of this paper was to review the literature and 5 cases within the authors' experience have also been included.     

Effects of recombinant granulocyte-macrophage colony-stimulating factor on bovine peripheral blood and mammary gland neutrophil function in vitro.

Modulation of peripheral blood and mammary gland neutrophil function following in vitro exposure to recombinant bovine granulocyte-macrophage colony-stimulating factor (rBoGM-CSF) was studied. Bovine blood and mammary gland neutrophils were cultured for 9 h in media containing 0.005, 0.05 or 0.5 microgram/mL rBoGM-CSF. Neutrophils treated with rBoGM-CSF exhibited significantly more chemotactic and bactericidal activities and tended to produce more superoxide anion than control cells. The effects of rBoGM-CSF on bovine neutrophil populations appeared to be dose-dependent. The production of superoxide anion and the bactericidal activity of mammary gland neutrophils were consistently higher than blood neutrophils. Only moderate increases in lipopolysaccharide-induced mammary gland neutrophil functions were observed following incubation with rBoGM-CSF which suggests that there may be a threshold of immunomodulation for these prestimulated cells. It may be possible to augment the functional capacity of bovine neutrophil populations in vivo through the therapeutic application of rBoGM-CSF and consequently enhance resistance of dairy cattle to bacterial infections.     

Influence of subclinical inflammatory airway disease on equine respiratory function evaluated by impulse oscillometry

Reasons for performing study: Inflammatory airway disease (IAD) is a nonseptic condition of the lower respiratory tract. Its negative impact on respiratory function has previously been described using either forced expiration or forced oscillations techniques. However, sedation or drug‐induced bronchoconstriction were usually required. The impulse oscillometry system (IOS) is a noninvasive and sensitive respiratory function test validated in horses, which could be useful to evaluate IAD‐affected horses without further procedures. Objectives: To determine the sensitivity of IOS in detecting alterations of the respiratory function in subclinically IAD‐affected horses without inducing bronchoprovocation and to characterise their respiratory impedance according to frequency for each respiratory phase. Methods: Pulmonary function was evaluated at rest by IOS in 34 Standardbred trotters. According to the cytology of bronchoalveolar lavage fluid (BALF), 19 horses were defined as IAD‐affected and 15 horses were used as control (CTL). Total respiratory resistance (Rrs) and reactance (Xrs) from 1–20 Hz as well as their inspiratory and expiratory components were compared between groups. Results: A significant increase of Rrs at the lower frequencies (R_{1–10 Hz}) as well as a significant decrease of Xrs beyond 5 Hz (X_{5–20 Hz}) was observed in IAD compared to CTL horses. IOS‐data was also significantly different between inspiration and expiration in IAD‐affected horses. In the whole population, both BALF eosinophil and mast cell counts were significantly correlated with IOS measurements. Conclusions: Functional respiratory impairment may be measured, even in the absence of clinical signs of disease. In IAD‐affected horses, the different parameters of respiratory function (Rrs or Xrs) may vary depending on the inflammatory cell profiles represented in BALF. Potential relevance: Impulse oscillometry could be used in a routine clinical setting as a noninvasive method for early detection of subclinical respiratory disease and of the results of treatment in horses.     

Effects of low-dose G-CSF formulation on hematology in healthy horses after long-distance transportation

The present study evaluated the effects of single-dose filgrastim on hematology in 16 healthy horses after long-distance transportation. Horses were assigned to receive filgrastim (0.23 µg/kg, SC, once; G-CSF group; n=8) or saline (0.9% NaCl) solution (0.3 ml, SC, once; control group; n=8) ≤ 1 hr before transportation. Horses were transported 2,530 km using commercial vans over the course of approximately 44 hr. Clinical examinations and hematologic analyses were performed on all horses before and after transportation. Because the post-transportation white blood cell counts and bacillary neutrophil to segmented neutrophil ratio were significantly higher in the G-CSF group, filgrastim may have promoted the mobilization of neutrophils from marrow. Filgrastim deserves a further study for efficacy in preventing horse shipping fever.