Prevalence of fungal detection
A large number of fungal genera were identified in this study,
with Aspergillus sp. and Penicillium being the most
commonly found in respiratory fluids. While similar genera have
been reported in previous studies,10,25 up to 5
different genera or up to 5 different species ofAspergillus sp. could be concomitantly identified in the airways
of a single horse. It has previously been documented thatPenicillium , Aspergillus sp., and Muroraceaegenera were airborne, ubiquitous and frequently found in the air
of stables26 while Aspergillus sp. is the most
commonly isolated fungi in hay.12,27 Detection of
these fungal elements in the airways may simply reflect the environment
in which the horse was located before and during sample
collection.10,21,28 Indeed, the authors of a recent
publication identified the fungal microbiota present along the upper and
lower respiratory tract of healthy horses, and showed that fungal
microbiota of the pharynx was similar to that of the trachea in healthy
horses, indicating that the pharynx is potentially a major source of
microbes that translocate to the lower respiratory
tract.25 Even though an association between fungal
content in hay samples and fungal elements in the airways of horses has
not been identified,12 other sources of contamination
in horses’ stables remain to be investigated.
In the current study, the genus Aureobasidium sp. was found in
BALF only (and not in TW) of 10 horses (9 MA, 1 CTL). In horses, few
anecdotal studies reported the detection of Aureobasidium sp. in
fungal microbiota of the conjunctiva of clinically healthy
horses,29 in paranasal sinus of healthy and diseased
horses30 and through ITS2 gene sequencing (mycobiota)
in BALF of horses.31 However, the existence of an
immune-mediated hypersensitivity reaction leading to interstitial
pneumonitis due to Aureobasidium pullulans has been reported in
the human literature.32 Further studies are required
to confirm the possible pathogenicity of Aureobasidium sp. and
determine whether specific genera would present more risk than
others for the development of equine asthma.