Early onset airway obstruction in response to organic dust in the horse.

This research study investigates whether exposure to organic dust leads to immediate changes in lung function in horses suffering from Recurrent Airway Obstruction (RAO). The study revealed that unlike human asthmatic patients, horses do not show an early-phase response, however, healthy control horses showed a minor but significant early response to inhaled organic dust, which could act as a protective measure.

Objective of the Study

• The main aim of this research was to determine whether immediate changes in lung function are triggered in RAO-affected horses when they are exposed to organic dust. This is vital in validating the use of RAO as a model for human asthma since the presence or absence of an early-response phase could affect this comparison.

Methodology and Testing

• Twelve horses in total took part in the testing – six of them had diagnosed RAO while the other six formed the healthy control group.
• A nebulizer was used to challenge the horses with a hay-straw dust suspension.
• The scientists measured the total respiratory resistance found in the horses one hour after the nebulization.
• The researchers also tracked the concentration of histamine in bronchoalveolar lavage fluid (BALF) to identify any potential inflammatory response from the horses getting in contact with the organic dust.

Findings from the Study

• The study revealed changes in respiratory resistance and reactance in the control group post-nebulization, though this was not significant in the RAO group.
• Also, the concentration of histamine, which usually signifies an inflammatory response, significantly increased after nebulization in the control group, but remained unchanged in the RAO horses. This implies that inflammation did not prominently occur in the RAO horses.
• The outcome suggests a correlation between the early post-nebulization period and both the pre-treatment BALF mast cell numbers, as well as the peak BALF histamine concentration after nebulization.

Conclusion and Implications

• The authors concluded that unlike human asthmatic patients, horses with RAO do not exhibit an early-phase response to inhaled organic dust.
• However, the observed mild but significant early response in healthy horses may have a protective function by reducing the amount of dust inhaled subsequently. Such a protective mechanism is seemingly compromised in RAO horses.