Blood biomarkers found for asthma in horses

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Researchers have identified blood biomarkers they say may be useful in diagnosing equine asthma.

Asthma in horses is associated with nonspecific respiratory clinical signs and may appear only as exercise intolerance.

Its diagnosis relies on the use of a bronchoscope, which is passed into the lungs. Fluid is squirted into a small part of the lung and then collected to be examined under a microscope for compatible clinical signs.

University of Montreal researcher Clementine Gy and her colleagues said that identifying blood biomarkers for asthma would help diagnose the condition in the field, because there are areas where bronchoalveolar lavage – the lung-wash procedure – is not routinely performed in clinical practice.

For their study, they used 14 horses diagnosed with asthma on the basis of increased neutrophil numbers in their lung wash. For comparison, they also used nine healthy control horses, and 10 horses with other unrelated health conditions.

Each horse underwent a physical examination, clinical score, blood work, and bronchoalveolar lavage.

Serum concentrations of surfactant protein D, haptoglobin, and secretoglobin were measured.

Surfactant protein is a protein that plays an important role in protecting the lungs against various inflammatory processes.

Haptoglobin is an acute phase protein produced by the liver, which increases in serum in response to inflammatory stimuli.

Picture taken with an endoscope of the bronchi of a horse with recurrent airway obstruction or asthma. Note how due to bronchoconstriction the diameter of the bronchi is narrower in this image compared to the image below.
Picture taken with an endoscope of the bronchi of a horse with recurrent airway obstruction or asthma. Note how due to bronchoconstriction the diameter of the bronchi is narrower in this image compared to the image below.

Secretoglobin is a small anti‐inflammatory protein mainly secreted by the mucosal cells of the lungs.

Concentrations of each protein above certain levels were generally found to differentiate horses with asthma from those who were healthy or had other unrelated conditions.

However, they proved much better at identifying asthma-affected horses when the levels of all three were considered together for each horse.

“Haptoglobin, secretoglobin, and surfactant protein D and their combination are potential diagnostic aids for the diagnosis of neutrophilic asthma in horses,” the researchers concluded in the Journal of Veterinary Internal Medicine.

“More studies are needed to correlate biomarkers with the phenotype of asthma and potentially develop specific treatments for mild to moderate asthma.”

Endoscopic picture of the bronchi of a horse without recurrent airway obstruction or asthma.
Endoscopic picture of the bronchi of a horse without recurrent airway obstruction or asthma.

The researchers said a significant difference was found in blood leukocyte and neutrophil counts between asthmatic and healthy horses.

“These results suggest systemic inflammation, but it remains to be determined if it represents a spillover of lung inflammation into the bloodstream or an intrinsic feature of the disease as suggested for horses with severe asthma.”

The full study team comprised Gy, Mathilde Leclere, Amandine Vargas, Carolyn Grimes, and Jean‐Pierre Lavoie, all with the Faculty of Veterinary Medicine at the University of Montreal.

Investigation of blood biomarkers for the diagnosis of mild to moderate asthma in horses
Clementine Gy, Mathilde Leclere, Amandine Vargas, Carolyn Grimes, Jean‐Pierre Lavoie.
16 May 2019 https://doi.org/10.1111/jvim.15505

The study, published under a Creative Commons License, can be read here

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