Population
Population summary is presented in Table 1. On average 60 harness
racehorses present each year at the Norwegian University of Life
Sciences for HSTE using our standardised protocol. This represents
approximately 1080 horses during the study period between 2005 and 2022.
Of these, eighteen harness racehorses were diagnosed with compression of
the base of the epiglottis during periods of poll flexion and met the
inclusion criteria, giving an estimated prevalence rate of 1.7%. Of
these eighteen horses, 11 were NSCTs and 7 were STBs. There were 50%
(9/18) mares, 39% (7/18) stallions and 11% (2/18) geldings. The horses
as a group presented at a mean ± SD age of 4.7 ± 2.0 years. The STBs
presented at 4.0 ± 0.8 years (range 3-5 years) and the NSCTs at 5.1 ±
2.4 years (range 3-10 years). The presenting complaint was poor
performance alone in 44.4% (8/18), abnormal respiratory noise alone in
33.3% (6/18) and both abnormal respiratory noise and poor performance
in 11.1% (2/18). One horse (5.6%) presented due to physical collapse
during a race and one horse (5.6%) presented for a routine fitness
test. Three horses had abnormal respiratory noise mostly evident when
driven on the bit (horse nr. 6, 9 and 15).