EQUINE | Equine Disease Update
EQUINE | Equine Disease Update
sonography may allow detection of small lesions , providing the opportunity for early intervention . Stem cell therapy seems to be promising .
Reproduction
Ultrasonography has changed equine reproduction over recent decades and Dr Jonathan Pycock stated that currently one of the most promising areas is the use of colour Doppler imaging . This has the potential to provide information on the status and future success of an embryo [ 20 ] and the measurement of blood flow in the follicular wall is a useful means to forecast when ovulation is going to occur [ 21,22 ] in addition to being an early indicator of the future position of the embryo proper [ 23 ]. This will hopefully lead to the ability to predict embryonic death and , when evaluating twin pregnancies , may allow for determination of which embryo should be terminated .
Early embryonic death ( EED ) remains a major concern in the equine breeding industry due to the resultant economic losses . Factors influencing EED can be divided into external ( nutrition , transport , sire effects etc .) and maternal ( hormone deficiencies and imbalances , uterine environment , age and lactation ). It is often assumed that the most common cause of EED is a lack of progesterone brought about by luteal insufficiency but it remains debatable whether exogenous progesterone or progestogens are effective in preventing EED .
Dr Pycock recommended that progesterone therapy be used in mares with marked uterine oedema and an irregular corpus luteum at the time of first examination for pregnancy ( 15 days ) [ 24 ]. The gonadotropin-releasing hormone ( GnRH ) agonist buserelin has yet to be evaluated in a large study . Buserelin has been shown to increase pregnancy rate [ 24 – 26 ] but its exact pharmacological action is unknown . Stout et al . [ 27 ] reported that treatment with buserelin on day 10 after ovulation did not significantly affect peripheral plasma progesterone concentrations or the luteolytic drive in non-pregnant or pregnant mares .
Endometrosis is defined as a chronic degenerative process characterised by fibrosis in the stromal and periglandular components of the endometrium . This condition , however , rarely occurs by itself but endometrosis may increase the risk of persistent breeding-induced endometritis , lowering pregnancy rates and increasing risk of EED and abortion . Endometrosis is best diagnosed via a biopsy of the endometrium . There is a close relationship between the mare ’ s ability to become pregnant and maintain a healthy pregnancy until term and the extent of endometrosis present . Recent research , is showing promising results from stem cell therapy [ 28 , 29 ]. Currently studies are small and thus it is too early to tell if it will be successful in the long term .
Cardiology
Physiological mitral and tricuspid regurgitation , have been shown to have no association with race performance [ 30 ] while pathological mitral regurgitation is a progressive disease [ 31 ]. There is a need , however , to perform more epidemiological studies on the impact of specific forms of valvular regurgitation and pathology in subpopulations of horses across the range of equestrian disciplines . Atrial fibrillation remains an area of interest particularly with the realisation that , in paroxysmal atrial fibrillation , 90 % of horses are able to selfconvert . For the remainder of horses that do not convert themselves , treatment may be required [ 32 ]. Treatments include medical use of quinidine or electrical cardioversion [ 33 ]. Some work has been done to show that atrial fibrillation may be a heritable trait in Standardbred pacers [ 34 ]. Prof Celia Marr also discussed novel echocardiographic techniques for assessing regional , circumferential and longitudinal ventricular function , 2-dimensional strain imaging [ 35 – 37 ] and tissue Doppler imaging [ 38 ]. These newer tools allow the clinician to assess diastolic function more readily than conventional 2-dimensional
10 • Equine Health Update •