Metabolic byproducts in the breath of horses could be used to identify those with equine airway disease, according to researchers in Italy.
Scientists who undertook the University of Camerino study found differences between the metabolites in the breath of healthy horses and those with equine asthma.
Marilena Bazzano and her colleagues, writing in the journal BMC Veterinary Research, noted the increasing scientific interest in the analysis of respiratory biofluids in human and veterinary lung research.
Equine asthma affects about 14% of adult horses and is considered an animal model for human disease.
For their study, the study team investigated the metabolic byproducts found in bronchoalveolar lavage fluid and exhaled breath condensate in 12 horses — six healthy controls and six diagnosed with severe asthma.
A bronchoalveolar lavage involves a bronchoscope being passed through the mouth or nose into the airways of the lungs. A measured amount of fluid is introduced and then collected for examination
The researchers identified 12 metabolites in the lavage fluid and seven in the breath condensate.
In the lavage fluid, there were differences in the profiles of myo-inositol, formate, glycerol and isopropanol between the healthy horses and the asthmatic horses.
In the breath condensate, higher levels of methanol and ethanol were found in the asthmatic group.
The higher methanol concentrations indicate the active inflammatory status of airways in horses affected by asthma, they say.
The significant increase in ethanol concentrations among the asthmatic horses might be related to the presence of pulmonary disease. “This metabolite was found to be higher in the exhaled breath of patients suffering from pulmonary cystic fibrosis compared to healthy subjects,” they said.
The authors say the possibility of non-invasively collecting biological samples of respiratory origin in standing non-sedated horses without coercion represents the major advantage of using breath condensate.
“Notwithstanding this considerable advantage, the lack of standardized collection methods represents a major limitation in the use of this specimen for diagnostic purpose in clinical practice.”
The study team also noted the absence of commercially available devices for its collection. There is also little known about how environmental and animal factors might affect collection.
The high variability in sampling procedures across studies should be taken into account when interpreting breath-condensate results, they say.
The authors acknowledged the limited number of subjects enrolled in the study. However, there is no doubt that the analysis of metabolites has great potential to better explain the disordered processes involved in equine asthma.
“Further studies are necessary to investigate the role of these metabolites, allowing researchers to adopt novel diagnostics and therapeutic strategies to treat the disease.”
Bazzano, M., Laghi, L., Zhu, C. et al. Respiratory metabolites in bronchoalveolar lavage fluid (BALF) and exhaled breath condensate (EBC) can differentiate horses affected by severe equine asthma from healthy horses. BMC Vet Res 16, 233 (2020). https://doi.org/10.1186/s12917-020-02446-9