Cold air-induced late-phase bronchoconstriction in horses

Towards personalized medicine for the treatment of equine asthma

Although horses with asthma share similar clinical signs, the heterogeneity of the disease in terms of severity, triggering factors, inflammatory profile, and pathological features has hindered our ability to define biologically distinct subgroups. The recognition of phenotypes and endotypes could enable the development of precision medicine, including personalized, targeted therapy, to benefit affected horses. While in its infancy in horses, this review outlines the phenotypes of equine asthma and discusses how knowledge gained from targeted therapy in human medicine can be applied to evaluate the potential opportunities for personalized medicine in equine asthma and to suggest avenues for research to advance this emerging field.

Respiratory oscillometry testing in relation to exercise in healthy and asthmatic Thoroughbreds

BACKGROUND

Racehorses may experience exercise-induced bronchodilation or bronchoconstriction, with potential differences between healthy and asthmatic individuals.

OBJECTIVES

To identify exercise-related lung function variations by oscillometry in racehorses, compare lung function between healthy and mild equine asthma (MEA) horses, assess oscillometry's potential as a predictor of racing fitness.

STUDY DESIGN

Prospective case-control clinical study.

METHODS

Fourteen Thoroughbred racehorses (5 healthy, 9 MEA) underwent a protocol including respiratory oscillometry at rest, exercise with fitness monitoring, oscillometry at 15 and 45 min post-exercise, and bronchoalveolar lavage fluid (BALf) cytology. Oscillometry parameters (resistance [Rrs] and reactance [Xrs]) were compared within and between healthy and MEA groups at different timepoints. Associations between Rrs and Xrs at rest and 15 min post-exercise and BALf cytology and fitness indices were evaluated.

RESULTS

MEA horses showed higher Rrs at 15 min post-exercise (0.6 ± 0.2 cmH2 O/L/s) than healthy horses (0.3 ± 0.1 cmH2 O/L/s) (p < 0.01). In healthy horses, Rrs decreased at 15 min post-exercise compared with resting values (0.5 ± 0.1 cmH2 O/L/s) (p = 0.04). In MEA horses, oscillometry parameters did not vary with time. Post-exercise Xrs inversely correlated with total haemosiderin score (p < 0.01, r2  = 0.51). Resting Rrs inversely correlated with speed at 200 bpm (p = 0.03, r2  = -0.61), and Xrs with maximum heart rate (HR) during exercise (p = 0.02, r2  = -0.62). Post-exercise Rrs inversely correlated with mean (p = 0.04, r2  = -0.60) and maximum speed (p = 0.04, r2  = -0.60), and HR variability (p < 0.01, r2  = -0.74).

MAIN LIMITATIONS

Small sample size, oscillometry repeatability not assessed, potential interference of upper airway obstructions, external variables influencing fitness indices.

CONCLUSIONS

Oscillometry identified lung function differences between healthy and MEA horses at 15 min post-exercise. Only healthy horses exhibited exercise-induced bronchodilation. Oscillometry showed potential in predicting subclinical airway obstruction.

Suspected Frostbite Injuries in Coypu (Myocastor coypus)

Native to South America, the coypu (Myocastor coypus) is an invasive alien species (IAS) of Union concern. It was introduced to Germany a hundred years ago and is considered established in all German federal states. Between January and February 2021, ground temperatures below -10° Celsius were recorded in Lower Saxony, Germany, for approximately two consecutive weeks. Five male and five female coypus, harvested between 23 February and 31 March 2021, received a post-mortem examination. Nutritional status was poor in six cases, moderate in three and good in one case. Pregnancy was observed in two females. In all the animals, lesions were predominantly found on the distal limbs (n = 7) and/or tail (n = 10), involving the skin and soft tissue with occasional exposure or loss of bones. The histological findings consisted of chronic, ulcerative to necrotizing dermatitis and occasional ulcerative-suppurative dermatitis, necrotizing myositis, thrombosis, granulation tissue, fibrosis and intralesional dystrophic mineralization. Intralesional bacteria were present in six and fungal spores in one animal. Determination of the exact cause was not possible; however, considering the local weather conditions and the distribution of lesions, frostbite injuries have to be considered as the most likely cause. The intralesional bacteria and fungal spores most likely represent secondary contaminants. Interestingly, lesions of this kind have not been reported in coypus in Germany so far. Therefore, frostbite should be considered as a potential cause of disease in coypus, warranting further investigation.

Owner Compliance to an Environmental Management Protocol for Severe Equine Asthma Syndrome

Severe equine asthma (SEA) syndrome is a chronic recurrent respiratory disease, common among adult horses. The disease occurs in genetically susceptible individuals after their exposure to organic dust. Thus, environmental management has proved essential in controlling airway challenge and disease exacerbation. This is a demanding process that can only be achieved through the horse owners' cooperation. One year after initial diagnosis of SEA in a group of 39 horses, owner compliance to an environmental management protocol was evaluated. The overall compliance to the protocol was poor and the horses' clinical health and need for pharmacological management was related to the successful implementation of the environmental recommendations provided on disease diagnosis.

Efficacy of dexamethasone, salbutamol, and reduced respirable particulate concentration on aerobic capacity in horses with smoke-induced mild asthma

Background

Mild asthma in horses decreases racing performance and impairs gas exchange. The efficacy of treatment on performance is unknown.

Hypothesis

Treatment targeting lung inflammation improves V˙O₂peak in horses with mild asthma.

Animals

Thoroughbred polo horses (n = 12) with smoke‐induced mild asthma. Horses were exposed to increased ambient particulate matter (35.51 μg/m³ [PM_2.5]; day mean, centrally measured) from day −33 to 0, from bushfire smoke (natural model).

Methods

Prospective, randomized, placebo‐controlled, double‐blinded clinical trial. All horses completed 3 V˙O₂peak tests, measuring aerobic and anaerobic variables: day 0 ‐baseline; day 16 ‐after dexamethasone (20 mg IM q24h; DEX, n = 6) or saline treatment (SALINE, n = 6), under improved ambient PM_2.5 concentrations (7.04 μg/m³); day 17‐15‐30mins after inhaled salbutamol (1500 μg). Bronchoalveolar lavage and mucus scoring were performed on day −8 and day 20. Linear mixed effects models were used to examine the effects of timepoint and treatment group on BAL differential cell counts, mucus scores, aerobic and anaerobic variables.

Results

Horses’ mucus scores improved significantly from day −8 to 20 by 1.27 ± .38 (P = .01). There was a significant increase in V˙O₂peak of 15.5 ± 4.0 mL(min.kg)⁻¹ from day 0 to 17 (P = .002), representing an average (mean) increase in V˙O₂peak of 13.2%. There was no difference in V˙O₂peak between treatment groups (SALINE versus DEX) at any timepoint.

Conclusions and Clinical Importance

This study highlighted the key role of improved air quality on functionally important airway inflammation. Evidence provided is central to increasing owner compliance regarding improved air quality for the treatment and prevention of mild asthma.

Exercise-induced Pulmonary Hemorrhage: Is It Important and Can It Be Prevented?

Exercise-induced pulmonary hemorrhage (EIPH) occurs commonly in horses undergoing strenuous exercise. Reported risk factors include racing in cold temperatures and wearing of bar shoes. In horses with documented moderate to severe EIPH, increasing the interval between races and adopting a negative race pace strategy may reduce the severity of EIPH in subsequent races. EIPH seems to have an impact on performance only when moderate to severe. This occurs in a small number of starters, approximately 6%. EIPH often is erratic in severity from race to race, although across a population it is weakly progressive over increasing race starts.

A comparison of unheated loose housing with stables on the respiratory health of weaned-foals in cold winter conditions: an observational field-study

Background

Newly weaned horses in Finland are often moved to unheated loose housing systems in which the weanlings have free access to a paddock and a shelter. This practice is considered to be good for the development of young horses. The daily temperatures can stay below − 20 °C in Finland for several consecutive weeks during the winter season. However, the effect of unheated housing in a cold climatic environment on the respiratory health of weanlings under field conditions has not been studied before. This investigation was an observational field-study comprising 60 weanlings among 11 different voluntary participant rearing farms in Finland. Weanlings were either kept in unheated loose housing systems (n = 36) or in stables (n = 24) and were clinically examined on two separate occasions 58 days apart in cold winter conditions.

Results

The odds of clinical respiratory disease were lower in the older foals (log_e days); OR = 0.009, P = 0.044). The plasma fibrinogen concentration was higher when the available space (m²/weanling) in the sleeping hall was smaller (P = 0.014) and it was lower when the sleeping hall was not insulated (P = 0.010). The plasma fibrinogen concentrations at the second examination were lower with a body condition score above 3 (P = 0.070). Standardbreds kept in loose housing systems had a lower body condition score than Finnhorses or Standardbreds kept in stables at both examinations (P = 0.026 and P = 0.007, respectively). Haemoglobin level was lower in weanlings in loose housing systems compared to their counterparts at the first examination (P = 0.037). Finnhorses had higher white blood cell count than Standardbreds at first (P = 0.002) and at the second examination (P = 0.001).

Conclusions

Keeping weanling horses in cold loose housing systems does not seem to increase the occurrence of respiratory disease, but special attention should be focused on ventilation, air quality and feeding-practices. Our field study data suggest it might be advantageous to keep Standardbred foals born late in the season in a stable over the Finnish winter.