Association between fungal detection and other infectious
agents
To our knowledge, this is the first study to record detection of
multiple types of infectious agents (bacterial, viral, fungal andMycoplasma spp) in both TW and BALF, and to examine their
associations with equine asthma. Isolation of bacteria in TW has
previously been associated with lower airway
inflammation.33–36 However, due to a very low
prevalence of positive bacterial samples in the present study, it was
not possible to confirm this association with moderate or severe equine
asthma. Alternatively, frequent co-detection of fungal elements and
other infectious agents such as viruses or mycoplasms has been
highlighted in this study. Mycoplasma spp were recently found to
be detected in 19.4% of TW samples from horses with respiratory
diseases,37 although their detection in TW was not
significantly different between groups (CTL, MA, SA) in the current
study. The potential implication of mycoplasms in equine asthma remains
to be determined, especially by quantitative investigation as per other
bacteria in TW.
Our results indicated a significant positive association between fungal
detection by culture in BALF and detection of EHV-2 in BALF. So far, the
evidence of a potential role of respiratory viruses is controversial;
some studies report an association between MA and genome detection by
PCR for EHV-2, EHV-5 and ERBV,18,38 while others do
not.39,40 There has been speculation that these
viruses may act as immunosuppressive agents, predisposing to other
infections,41 or may be involved in persistent,
chronic fatigue syndromes.42 Larger multicentric
studies would be required to determine the possible synergy between
viruses, bacteria, fungi, particles etc. (interactome) in the
pathophysiology of equine asthma.