Inflammatory markers in bronchoalveolar lavage fluid of standardbred racehorses with inflammatory airway disease: response to interferon-alpha

The Effect of Race Training on the Basal Gene Expression of Alveolar Macrophages Derived From Standardbred Racehorses

Mild-to-moderate equine asthma is prevalent in young racehorses, particularly early in their training period. Although the precise etiopathogenesis remains undetermined, it is possible that the susceptibility of this population might partly reflect an exercise-associated immune derangement at the level of the airway. We performed a genome-wide basal gene expression scan on alveolar macrophages (AMs) isolated from Standardbred racehorses before and after commencement of competition race training with a view to identifying any exercise-associated gene expression modulation consistent with functional alterations, which might reflect training-associated immunological derangement. Microarray technology was used to analyze the basal gene expression profiles of bronchoalveolar fluid-derived AMs, harvested from six systemically healthy Standardbred racehorses before (T0) and after (T1) entry into training. In addition, AM lipopolysaccharide (LPS)-induced TNF-α and IL-10 release at T0 and T1 was assessed. Although the data revealed significant interhorse heterogeneity in relation to the magnitude of individual gene expression at each timepoint, within each horse, several inflammatory-related genes [e.g., chemokine ligands, interferons, and nuclear factor kappa-light-chain-enhancer of activated B cells (NFKB)] declined in expression from T0 to T1. Entry into training did not significantly alter AM LPS-induced TNF-α or IL-10 release. The data support a direct effect of training on AM basal gene expression, particularly with respect to immune-related genes. The pattern of training-associated differential gene expression may indicate relative downregulation of inflammatory-related genes, consistent with an immunosuppressive effect of training and an increased susceptibility to opportunistic pathogens.

Inflammatory Airway Disease of Horses--Revised Consensus Statement

The purpose of this manuscript is to revise and update the previous consensus statement on inflammatory airway disease (IAD) in horses. Since 2007, a large number of scientific articles have been published on the topic and these new findings have led to a significant evolution of our understanding of IAD.

Inflammatory airway disease, nasal discharge and respiratory infections in young British racehorses

REASONS FOR PERFORMING STUDY

Respiratory disease is important in young Thoroughbred racehorses, but the variation in the rates of occurrence between different ages and training groups has not been characterised.

OBJECTIVES

To determine the rates of respiratory disease, particularly inflammatory airway disease (IAD), as well as evidence of infection, and their variation between age and group.

METHODS

Horses were examined monthly in 7 British flat training yards over a 3 year period. IAD was defined as increased mucus in the trachea with increased proportions of neutrophils in tracheal wash samples. Frequencies of disease outcomes were estimated from the data.

RESULTS

The prevalence of IAD was 13.8% and the incidence was 8.9 cases/100 horses/month. Rates varied with training and age groups, decreasing in older animals. The prevalence of nasal discharge (ND) was 4.1%. Rates of bacterial isolation were more common than viral infections. The incidence and prevalence of several bacterial species decreased with age.

CONCLUSIONS

IAD and ND were common in young racehorses, varying significantly between training groups and decreasing with age, consistent with infection playing a role in aetiology.

POTENTIAL RELEVANCE

The high prevalence of IAD in 2-year-old horses in Britain suggests that routine endoscopic examination may be helpful in providing early diagnosis and appropriate therapy. The transmission of bacteria and viruses within and between groups of young animals and the role of infection, stable environment and factors inherent to each horse, including their genetic make-up, in the multifactorial aetiology of the disease all merit further study.

A case-control study of respiratory disease in Thoroughbred racehorses in Sydney, Australia

In order to investigate the role of infectious agents in the aetiology of lower respiratory tract disease in Thoroughbred racehorses, a matched case-control study was conducted. Cases were identified by the presence of coughing, and were compared to a control population matched on time of sample collection and location within the same training establishment. Tracheal wash samples were collected from 100 cases and 148 controls. Case horses were more likely than controls to have endoscopic and cytological evidence of airway inflammation. There was no significant association between serological evidence of infection by commonly implicated respiratory viruses and coughing. Similarly, mycoplasma were rarely isolated and were not associated with disease. In contrast, there was a strong association between isolation of greater than a total of 10(3) colony-forming units/ml of tracheal wash and coughing. Individual bacterial species associated with disease included Streptococcus zooepidemicus, Streptococcus pneumoniae, Streptococcus suis, Streptococcus sanguis, Pasteurella spp and Bordetella bronchiseptica. This study provides evidence of the role of bacterial infection in the aetiology of lower respiratory tract inflammation in racehorses. However, in 58% of cases, few or no bacteria were isolated. Hence, at the time of identification of disease, there was no evidence of viral, bacterial or mycoplasmal infection in the majority of coughing horses. The aetiology of the signs observed in these horses requires further investigation.

Attitudes of Australian veterinarians about the cause and treatment of lower-respiratory-tract disease in racehorses

A questionnaire was administered to members of the Australian Equine Veterinary Association to investigate their attitudes and behaviours regarding the cause, diagnosis and treatment of lower-respiratory-tract disease in racehorses. The most-important perceived risk factors related to the level of exposure and resistance to infectious agents, whereas factors associated with racing and climatic factors were lower ranked. By far the most-commonly implicated primary cause of disease was respiratory viruses. However, specific diagnostic tests (such as viral serology or virus isolation) were rarely performed. By far the most-common diagnostic procedure was auscultation (without a rebreathing bag). The relative importance of diagnostic procedures was influenced by the proportion of total workload comprising horse work. Many respondents believed that bacteria become secondarily involved in disease; accordingly, antibiotic therapy was the most-commonly reported therapy. However, bacteriology of lower-airway-fluid samples was not commonly performed. The most-commonly used antibiotics were the potentiated sulphonamides (either alone or in combination with mucolytics or bronchodilators), followed by procaine penicillin and penicillin combined with gentamicin. Mainly, treatment would appear to be based on empirical beliefs rather than exhaustive investigation of individual cases.

Equine respiratory pharmacology

Differentiation of diseases of the equine respiratory tract is based on history, clinical signs, auscultation, endoscopy, imaging, and sampling of airway exudate. Upper respiratory therapies include surgical correction of airway obstructions; flushing of localized abscesses (strangles), guttural pouch disease, or sinusitis; and oral or parenteral antibiotic and anti-inflammatory therapy if deemed necessary. Pneumonia usually is treated with antimicrobials, anti-inflammatories, and bronchodilators. Pleural drainage is indicated if significant pleural effusion is present. The most commonly used therapies for early inflammatory and chronic allergic obstructive conditions include bronchodilators and anti-inflammatories. Acute respiratory distress, particularly acute pulmonary edema, is treated with diuretics (usually furosemide), intranasal oxygen, bronchodilators, corticosteroids, and alleviation of the underlying cause. Furosemide also had been used in North America as a race-day preventative for exercise-induced pulmonary hemorrhage (EIPH), but recent data have shown that furosemide may be a performance-enhancing agent itself.

Dermatologic tumors (excluding sarcoids)

Cutaneous neoplasia represents a clinical problem with which veterinarians are commonly challenged. This article addresses equine cutaneous squamous cell carcinoma, squamous cell papilloma, melanoma, mastocytosis, and lymphosarcoma. Current concepts regarding the origin, pathogenesis, diagnosis and treatment of each neoplasm is emphasized.