EQUINE VETERINARY EDUCATION Equine vet. Educ. (2018) 30 (5) 247-254 doi: 10.1111/eve.12726


Case Report


Caecal intussusceptions and typhlocolitis in horses with severe Gastrodiscus aegyptiacus infestation


Z. Gratwick†*, C. Donnellan‡, P. C. Page†, A. Viljoen†, J. Williams§ and C. H. Lyle† †Department of Companion Animal Clinical Studies, University of Pretoria, Onderstepoort, South Africa; ‡Blue Cross Veterinary Hospital, Cape Town, South Africa; and §Department of Paraclinical Studies, University of Pretoria, Onderstepoort, South Africa. *Corresponding author email: zoe.gratwick@gmail.com


Keywords: horse; Gastrodiscus aegyptiacus; caecal intussusception


Summary The intestinal trematode


Antemortem diagnosis currently depends on identification Gastrodiscus aegyptiacus


(G. aegyptiacus) has been recognised in equids around the world formany years, but its pathogenicity is yet to be confirmed. This report describes seven cases of severe G. aegyptiacus infestation, including six cases of caecal intussusception.


Introduction


Gastrodiscus aegyptiacus (G. aegyptiacus) is an amphistome fluke capable of parasitising the intestine of horses, donkeys, zebras, pigs and warthogs (Bracegirdle 1973; Azzie 1975; Applewhaite and Ruiz 1983; Boomker et al. 1991; Wells et al. 1998; Ayele et al. 2006; Malik et al. 2006; Opara et al. 2006; Ohaeri and Okoro 2012; Van Laaren 2014). This parasite has been reported in a number of countries in Africa, Asia and South America (Bracegirdle 1973; Azzie 1975; Applewhaite and Ruiz 1983; Malik et al. 2006). Its life cycle is incompletely described, but is known to involve a number of stages including ova, miracidia, rediae, cercariae, metacercariae and adult forms (Malek 1971). Equids become infested via ingestion of metacercariae, often encysted on blades of grass (Malek 1971). Planorbid snails of the Bulinus genus primarily act as intermediate hosts, although outbreaks have occurred in areas where this host is not endemic (Malek 1971). A number of other snail species are susceptible to G. aegyptiacus infestation under experimental conditions, and may play a role in some natural infestations (Mukaratirwa et al. 2004). Bulinus are freshwater snails, found in lakes and residual pools of seasonally flowing rivers and streams (Curtis et al. 2010). Infestation of the horse with G. aegyptiacus is thought to be associated with grazing wet pastures or drinking from natural water sources. The fluke measure 12– 18 9 10–14 mm and are dorsoventrally flattened (Fig 1). They have a narrow anterior conical part and a rounded posterior part, giving them a ‘tennis racket’ appearance (Malek 1971). The operculate ova measure 140–170 9 90–100 lm(Fig 2). These parasites are usually found in the caecum and ascending colon, but have been identified in all parts of the equine gastrointestinal tract (Azzie 1975). Their prevalence in most countries is unknown, but reports in Ethiopia, Burkina Faso, South Africa and Pakistan describe a prevalence of 4– 63% (Vercruysse et al. 1986; Wells et al. 1998; Ayele et al. 2006; Malik et al. 2006), with the particularly high prevalence of 63% representing the prevalence in donkeys in one area of South Africa. The relative prevalence in each area has not been compared for horses vs. donkeys.


of parasite ova using a faecal sedimentation test (Visser and Pitchford 1972). The sensitivity of this test is unknown. Treatment options include oral administration of either oxyclosanide or resorantel (Roberts et al. 1975). There are many reports of G. aegyptiacus in the absence of clinical disease and the parasite was originally considered nonpathogenic. This is now considered likely to be untrue and cases of recurrent colic, lethargy and diarrhoea have been described (Azzie 1975; Roberts et al. 1975; Applewhaite and Ruiz 1983; Van Laaren 2014). However in these reports, cases were isolated and other potential causes of the described symptoms were not considered. This case series describes horses infested with G. aegyptiacus, showing colic (predominantly associated with caecal intussusception), weight loss and diarrhoea between 2001 and 2016 at an equine hospital in South Africa. Intussusception involving the equine caecum is generally


rare (Edwards 1986; Owen et al. 1989), although a higher regional incidence was recently reported in New Zealand (Bell and Textor 2010). The pathophysiology underlying caecal intussusception in the horse is poorly understood. It has been suggested that intussusceptions are due to dysmotility, in particular different relative motility of one section of gut relative to an adjacent section. Local inflammation is considered to have a detrimental effect on gastrointestinal motility (Kalff et al. 1998; Bauer et al. 2002). It is therefore possible that any factor leading to intestinal inflammation may lead to altered intestinal motility and potential caecal intussusception. Parasites including Anoplocephala perfoliata (A. perfoliata) and cyathostomin species have been seen in conjunction with caecal intussusception and published case series suggest their possible association (Barclay et al. 1982; Mair et al. 2000). Myenteric ganglionitis has been suggested as a specific mechanism for compromised motility in parasitic infestations (Pavone et al. 2011). Typhlocolitis has been reported both on its own and in conjunction with caecal intussusception (Mair et al. 2000; Smith et al. 2015). There are a number of potential causes of typhlocolitis in the horse, including cyathostomins, Salmonella, Clostridia and acorn consumption (Mair et al. 2000; Johns 2010; Smith et al. 2015).


Case details


Case 1 An 11-year-old Boerperd mare was presented at the Onderstepoort Veterinary Academic Hospital (OVAH) with a 3 week history of weight loss and poor appetite. The mare


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