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accumulate it within their gastrointestinal tract while others freely pass it is not known.
Epidemiology
Sand enteropathy has been reported worldwide but specific geographic predilections exist. In North America, Arizona (Rollins & Clement, 1979), Colorado (Bertone et al., 1988), Michigan (Kaneene et al., 1997; Keppie et al., 2008), California (Ferraro, 1973; Ragle et al., 1989a), Florida (Hart et al., 2013; Specht & Colahan, 1988) and British Columbia (Udenberg, 1979) appear to be over-represented when reviewing reports of sand enteropathy in the horse. In Europe, the Nordic countries (Hukkinen, 2015; Husted et al., 2005; Kaikkonen et al., 2016; Kendall et al., 2008; Korolainen & Ruohoniemi, 2002; Niinist€ Niinist€
o et al., 2014; Niinist€ o et al., 2019; o et al., 2018), Germany (Loschelder & Gehlen, 2017;
Reichelt & Lischer, 2001) and Switzerland (Graubner et al., 2017) are over-represented. Cases of sand enteropathy in Australasia are most commonly reported from Western Australia (Granot et al., 2008). Anecdotally, sand enteropathy is a common problem in Middle Eastern countries and it has been reported in Israel (Granot et al., 2008). The authors believe that limitations of publishing in English likely result in underrepresentation of countries from other geographical regions as there have been sporadic reports from countries such as Brazil (Alonso et al., 2020) that are not represented in the English language literature. Sand accumulation has been reported in multiple horse
breeds. However, some breeds, such as Quarter Horses (Hart et al., 2013; Keppie et al., 2008; Kilcoyne et al., 2017), Shetland Ponies (Graubner et al., 2017), Miniature Horses (Granot et al., 2008; Hart et al., 2013; Keppie et al., 2008; Ragle et al., 1989a, 1992) and Finnhorses (Kaikkonen et al., 2016; Ruohoniemi et al., 2001), appear predisposed. Many of these breeds are known for their voracious appetites and ‘stoic’ natures as they have adapted to cope with adverse environments (Taylor et al., 2002). In contrast, Thoroughbred horses appear to rarely develop sand accumulations within the gastrointestinal tract (Granot et al., 2008; Hart et al., 2013; Kilcoyne et al., 2017; Ragle et al., 1989a), although this may reflect usage type of the horse and, in turn, access to sand, rather than breed. Sex of the horse is not associated with sand enteropathy
(Hart et al., 2013; Keppie et al., 2008; Kilcoyne et al., 2017). Recent research has demonstrated that greedy horses that eat all their roughage are at increased risk of sand accumulation, whereas a dominant position in herd hierarchy is protective (Niinist€
o et al., 2019). Pasture quality has been identified as a risk factor for
increased faecal sand excretion with both short and long grass in combination with sandy soil increasing the risk, while clay soil has the lowest risk for faecal sand excretion (Husted et al., 2005). No apparent explanation for the significantly enhanced risk for long grass on fine sandy soil was found, but the roots of long grass might be less anchored in sandy than clay soils and horses might accidentally ingest more sand when involuntarily picking up these roots. In the same study, feeding directly on the ground was shown to be a risk factor when combined with short (1–5 cm) or no grass (Husted et al., 2005). Lack of supplemental feeding outdoors when horses were kept on pastures with short grass increased the
risk of faecal sand excretion, while it had no effect in paddocks with no grass (Husted et al., 2005).
Diagnosis
The clinical signs of sand enteropathy are varied, and it is important to recognise that the clinical presentation overlaps with a range of other gastrointestinal diseases. Sand accumulations can be present without any clinical signs (Kaikkonen et al., 2016; Kendall et al., 2008; McIntyre, 1917), and the amount of sand accumulation required to cause clinical signs is poorly described, although it has been suggested that it may be dependent on the horse’s size and may vary from individual to individual (Bertone et al., 1988; Hart et al., 2013; Keppie et al., 2008). Acute colic is a well-recognised presentation of sand
enteropathy (Granot et al., 2008; Hart et al., 2013; Kaikkonen et al., 2016; Kaneene et al., 1997; Kilcoyne et al., 2017; McIntyre, 1917; Niinist€
o et al., 2019; Ragle et al., 1989a, 1992;
Rollins & Clement, 1979; Specht & Colahan, 1988). Current reports describe no specific signs that would distinguish sand colic from other types of colic (Graubner et al., 2017; Hart et al., 2013; Kilcoyne et al., 2017). The most common finding in horses with acute ‘sand colic’ is a large colon impaction caused by complete intraluminal obstruction with sand and feed material (Hart et al., 2013; Ragle et al., 1989a; Ruohoniemi et al., 2001; Specht & Colahan, 1988; Udenberg, 1979). In one study, horses that presented for colic in a geographically at-risk region of Sweden had larger sand accumulations than orthopaedic controls supporting the role of sand accumulation as a likely causative factor in colic (Kendall et al., 2008). The reasons why some horses with large accumulations of sand develop colic while others do not are not known. Diarrhoea and unexplained weight loss are commonly
reported presentations of chronic sand enteropathy (Bertone et al., 1988; Graubner et al., 2017; Hart et al., 2013; Kaikkonen et al., 2016; Kilcoyne et al., 2017; Ruohoniemi et al., 2001). However, a recent study did not find a clear relationship between owner reported clinical signs of diarrhoea and the presence of large sand accumulations (Niinist€
Instead, a history of colic or poor performance, or combinations of colic and diarrhoea, poor performance and diarrhoea, colic and hyperaesthesia, or poor performance and colic, as reported by the owner, were most likely to be associated with large accumulations of sand (Niinist€
o et al.,
2019). These findings are consistent with a previous study that demonstrated that the clinical presentation of horses with sand enteropathy, particularly poor performance, may mirror the presentation of horses with Equine Gastric Ulcer Syndrome (EGUS) (M€
onki et al., 2016). As such, sand enteropathy should
be considered as an important differential for the clinical presentation of EGUS in geographically predisposed regions or where horses are turned out in sand yards. Accurate diagnosis of sand enteropathy in the field can
be challenging. Auscultation of the ventral abdomen caudal to the xiphoid process and the characteristic ‘seashell’ sounds is commonly used. Although the test is highly specific, the low sensitivity of the test indicates that it does not identify horses with sand accumulation very well. Experimentally 6.3– 10.5 kg of sand was required before ventral sounds were audible (Ragle et al., 1989b).
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o et al., 2019).
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