LIMITATIONS
Fungal detection in BALF was performed on pooled BALF only, and not on
individual right and left BALF, which could have led to an overall lower
prevalence of fungal detection by culture in BALF. In a previous study,
while 100% of horses with “positive” pooled BALF were also positive
in left and/or right BALF, 14.6% of horses with “negative” pooled
BALF were positive in left and/or right BALF.12
Beyond detection of fungi in TW or BALF, quantification of the fungal
load in the airways also needs to be further investigated. Cytological
investigations of fungal elements were limited to qualitative dichotomy
(presence or absence) only. Quantification of fungal-like intracellular
particles by cytology or total fungal load quantification by qPCR assay
(18S rRNA gene) have recently been proposed, but these methods are yet
to be validated.23 Absolute quantification by
successive dilutions (as performed for bacteria in TW for
instance)16 were laborious, unrepeatable (data not
shown) and ultimately unsuccessful for fungal cultures. However,
establishment of a “pathological” cut-off, possibly through molecular
biology, could however help in the future for differentiating true
fungal infection from environmental contamination.
This study focused on fungi detection in airways samples, while ambient
airborne samples or component of horses’ environment (bedding, food)
were not collected. No association between fungal content in hay samples
and fungal elements in the airways of horses was detected in a previous
study.12 It would however have been interesting to
collect respirable and inhaled particulate samples in the horse’s
breathing zone, as previously described.47,48 The
relevance of such sampling, factually excluding horses referred to the
hospital for consultation, is however limited to field studies only,
most frequently focusing on MA rather than SA.