EQUINE VETERINARY EDUCATION Equine vet. Educ. (2020) 32 (11) 603-610 doi: 10.1111/eve.13129
Review Article
Non-strangulating intestinal infarction in horses in the UK: A review of 15 cases
J. A. Spanton* , T. S. Mair, C. E. Sherlock and D. Fews Bell Equine Veterinary Clinic, Maidstone, UK
*Corresponding author email:
spanton_4@hotmail.co.uk J. A. Spanton's present address: House and Jackson Veterinary Clinic, Blackmore, Essex, CM4 0LE, UK. D. Fews's present address: Finn Pathologists, One Eyed Lane, Weybread, Diss, Norfolk, IP21 5TT, UK
Keywords: horse; non-strangulating intestinal infarction; colic; diarrhoea; peritonitis
Summary The clinicopathological features of 15 horses diagnosed with non-strangulating intestinal infarction (NSII) based on identification of focal areas of intestinal necrosis without mesenteric strangulation were reviewed. The mean age at presentation was 16.3 years, median 13 years, and there was no age, sex, or breed predilection. The major presenting clinical signs included: acute colic ≤ 24 h duration in nine horses; diarrhoea, depression, and inappetence in four horses; and low-grade chronic or recurrent colic, depression, and inappetence in two horses. One horse presented with both acute colic and diarrhoea. Predisposing diseases included colitis or typhlocolitis in five horses and an initial strangulating small intestinal obstruction in three horses, but in seven horses no underlying or predisposing disease was identified. Four cases were managed medically and 11/15 were managed surgically. The most useful diagnostic test was exploratory celiotomy and the only successful treatment was complete resection of the necrotic intestine. Prognosis for survival was poor with a survival rate of only 1/15 (7%). Among the 15 horses, both single and multiple NSII lesions were seen, and they occurred in both the small intestine and large intestines. There was no evidence of Strongylus vulgaris infestation in any of the affected horses.
Introduction
Non-strangulating intestinal infarction (NSII; intestinal infarction not associated with a strangulating lesion) in the horse has been reported in association with thromboembolism secondary to Strongylus vulgaris larval migration, severe colitis, and coagulopathies (White 1981; Mair and Pearson 1995; Martin- Cuervo et al. 2013; Pihl et al. 2018). The larval stages of the helminth parasite S. vulgaris migrate in the cranial mesenteric artery and their presence can result in the generation of thrombi that can subsequently occlude arterioles supplying the intestine resulting in focal areas of intestinal infarction (Enigk 1951; Duncan and Pirie 1975). The caecum and ascending colon are the most commonly affected areas of the intestine in parasite-associated thromboembolic colic (Duncan and Pirie 1975), with the small intestine and descending colon affected less frequently (Pihl et al. 2018). Modern parasite control methods, including interval treatments with anthelmintic drugs, have reduced the prevalence of S. vulgaris (Herd 1990; Love 1992) and this is also believed to have been responsible for a decreased prevalence of NSII (White 1981; Hardy 2008;
Proudman 2017). However, the use of selective anthelmintic therapy programmes implemented in some European countries, such as Denmark, since 1999 as a consequence of a prescription-only anthelmintic policy have more recently been associated with an increased prevalence of S. vulgaris and an increased incidence of NSII cases (Nielsen et al. 2012; Nielsen et al. 2016; Pihl et al. 2018). In the United Kingdom (UK), anthelmintic drugs are
classified as POM-VPS (prescription only medicine – veterinarian, pharmacist, SQP) which means that veterinary surgeons, pharmacists, and suitably qualified persons should have sufficient information about the animal and the condition to be treated to enable them to prescribe and supply the appropriate drug. Although regular interval treatments with anthelmintics are still carried out by some horse owners in the UK, targeted anthelmintic treatments based on the results of regular faecal worm egg counts and the administration of a cyathostomin larvicidal treatment (usually moxidectin) in late autumn/early winter are currently recommended (Matthews 2008). Recent studies in the UK have revealed no evidence of any increase in S. vulgaris prevalence (Tzelos et al. 2017), presumably as a result of the continued widespread use of anthelmintics at least once a year in most horses. The clinical presentation of horses affected by NSII is
variable. Older reports describe acute colic pain of variable severity followed by depression, endotoxaemia, shock, and death (Gerber et al. 1971; White 1981). More recently, Pihl et al. (2018) reviewed 30 horses with NSII associated with S. vulgaris larval migration in Denmark; although all of these horses had a prior history of colic, clinical signs at admission to the hospital were characterised by depression and anorexia, with either no or only mild colic, and no signs of shock. The objectives of this study were to retrospectively review
the clinical features, management, underlying aetiologies, and outcomes of cases of NSII diagnosed at one equine hospital in the UK in the recent past. In particular, the importance (or lack thereof) of S. vulgaris-associated disease was assessed.
Materials and methods
Computerised records at the Bell Equine Veterinary Clinic were searched for cases of NSII that had been diagnosed at either exploratory celiotomy or post-mortem examination between 2005 and 2017. Non-strangulating intestinal infarction was diagnosed on the basis of one or more well-defined focal areas
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