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EQUINE VETERINARY EDUCATION
Equine vet. Educ. (2022) 34 (11) 600-606 doi: 10.1111/eve.13562
Review Article Diagnosis and management of sand enteropathy in the horse K. Niinist€
o† and B. W. Sykes‡,*
†Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland; and ‡School of Veterinary Sciences, Massey University, Palmerston North, New Zealand *Corresponding author email:
b.sykes@
massey.ac.nz
Keywords: horse; sand; geophagia; colic; diarrhoea
Summary Sand enteropathy is an important disease condition in the horse, particularly in geographically predisposed regions. The reasons why some horses eat sand, or why some horses accumulate sand when exposed and others do not are poorly understood. Weak evidence exists that deficiencies in iron or copper may play a role in geophagia, while factors such as the provision of supplemental feeding while at pasture, or the role of an individual animal within a herd hierarchy, may influence an individual animals’ disease risk. Diagnosis in the field is challenging. Current evidence does not support the use of the faecal glove sedimentation test for screening horses at risk of sand accumulation as it lacks both the sensitivity and specificity to accurately diagnose sand accumulation under field conditions. Instead, ultrasound is a useful screening test under field conditions, especially in ruling out sand accumulation. In contrast, ultrasound appears to be of limited value in the assessment of sand accumulations in acute disease and radiography remains the reference standard for diagnosis. Current evidence does not support the feeding of psyllium for the removal of sand accumulation. Instead, daily administration of psyllium and MgSO4, both at 1 g/kg bwt once a day via nasogastric tube, has been reported to be effective in removing the majority of sand accumulations over a 3–7 day period in a number of studies. Prevention remains challenging in horses at risk due to ongoing exposure to sandy pastures but, based on epidemiological evidence, small management changes may be beneficial in reducing disease risk.
Introduction
Disease related to sand accumulation in the equine gastrointestinal tract has been described for over a century (McIntyre, 1917), but evidence-based medicine recommendations particularly focussed on diagnosis and treatment have been scarce until recently. The purpose of this study is to review the current literature with a particular focus on the aetiology, epidemiology, diagnosis and treatment of sand enteropathy in the horse.
Aetiology
The deliberate consumption of soil (geophagia) is not unique to horses, but has been reported in many species including humans, various ruminants, monkeys and dogs (Abrahams, 2012). In nonequine species, many factors, such as age, gender and time of year, affect the deliberate consumption of soil (Abrahams, 2012; Kreulen & Jager, 1984). An age predilection exists with young dogs more prone to pica
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(Houpt, 1982), and in humans, the female gender is associated with increased geophagia and pica (Vermeer & Frate, 1979). Geophagia can be useful, or even necessary in some
species. Sheep have been shown to obtain up to 50% of their daily intakes of copper, iron, iodine, manganese, sodium and selenium from involuntary soil ingestion (Abrahams, 2012) and consumption of less than 20 g of soil a week prevented copper deficiency in sheep in one study (Rigg & Askew, 1934). Involuntary soil consumption with vegetables or cereals, especially in developing countries, has been shown to be a dietary source of minerals to people (Hallberg & Bjorn, 1981), and in birds, geophagia is a method of calcium ingestion (Abrahams, 2012). The reasons why horses practise geophagia are unknown
although both wild and domesticated horses choose certain sites to ingest soil (Abrahams, 2012; McGreevy et al., 2001). Contrary to many other species, horses do not regulate the intake of most minerals other than sodium (Ralston, 1986), evidenced in part by the finding that ponies with calcium deficiency do not develop a preference for calcium supplementation (Schryver et al., 1978). In a study of 30 horses, 15 geophagic horses showed no difference from controls in haematological or biochemical values, but they had lower serum iron concentrations and lower serum copper/zinc ratios (Aytekin et al., 2011). Similarly, no difference existed in zinc or phosphorus concentrations of the soil between preferred and nonpreferred geophagia sites, but concentrations of iron and copper were higher in the soil of geophagic sites than in adjacent control samples of soil (McGreevy et al., 2001). Iron deficiency may play a role in geophagia in people, although there is debate as to whether low concentrations of iron in blood are a cause or consequence of geophagia (Abrahams, 2012; Gardner & Tevetolu, 1957; Hooda et al., 2002). It has also been proposed that copper may be important as it is a cofactor in the regulation of serum iron concentrations (Aytekin et al., 2011). It is sometimes assumed that geophagic horses would prefer coarse soil, but in one study, soil textures were similar to control samples that the horses were not prone to consuming (McGreevy et al., 2001). Overall, the reasons why some horses are geophagic and others are not well understood. Some horses practise geophagia, while others ingest soil
or sand accidentally when trying to reach all their food (McIntyre, 1917; Niinist€
o et al., 2019). Underfeeding or
inadequate roughage has also been suggested to predispose horses to accidentally eating sand (Ferraro, 1973; Hanson, 2002; Rollins & Clement, 1979). It is common for horses on sandy pastures to consume sand (Filgueiras et al., 2009), but why some horses exposed to sand ingestion
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