Systematic review of gastrointestinal nematodes of horses from Australia

Muhammad A Saeed,Charles El-Hage,Brett Tennent-Brown,Caroline Jacobson,Lucy Cudmore,Jenni Bauquier,Martin K Nielsen,Lisa Walter,Edwina Wilkes,John Hurley,Anne Beasley,Ryan O’Handley,Abdul Jabbar,Kris J Hughes,Ian Beveridge,Ghazanfar Abbas,Peter Carrigan

doi:10.1186/s13071-019-3445-4

Abstract

BackgroundEquine gastrointestinal nematodes (GINs) have been the subject of intermittent studies in Australia over the past few decades. However, comprehensive information on the epidemiology of equine GINs, the efficacy of available anthelmintic drugs and the prevalence of anthelmintic resistance (AR) in Australasia is lacking. Herein, we have systematically reviewed existing knowledge on the horse GINs recorded in Australia, and main aspects of their pathogeneses, epidemiology, diagnoses, treatment and control.MethodsSix electronic databases were searched for publications on GINs of Australian horses that met our inclusion criteria for the systematic review. Subsets of publications were subjected to review epidemiology, diagnoses, pathogeneses, treatment and control of GINs of horses from Australia.ResultsA total of 51 articles published between 1950 to 2018 were included. The main GINs reported in Australian horses were cyathostomins (at least 28 species), Draschia megastoma, Habronema muscae, H. majus, Oxyuris equi, Parascaris equorum, Strongyloides westeri and Trichostrongylus axei across different climatic regions of Queensland, New South Wales, Victoria, and Western Australia. Nematodes are diagnosed based on the traditional McMaster egg counting technique, though molecular markers to characterise common GINs of equines were characterised in 1990s. The use of anthelmintic drugs remains the most widely-used strategy for controlling equine GIN parasites in Australia; however, the threshold of faecal egg count that should trigger treatment in horses, remains controversial. Furthermore, anthelmintic resistance within GIN population of horses is becoming a common problem in Australia.ConclusionsAlthough GINs infecting Australian horses have been the subject of occasional studies over the past few decades, the effective control of GIN infections is hampered by a generalised lack of knowledge in various disciplines of equine parasitology. Therefore, coordinated and focused research is required to fill our knowledge gaps in these areas to maximise equine health and minimise economic losses associated with the parasitic infections in Australia.

Highlights

Equine gastrointestinal nematodes (GINs) have been the subject of intermittent studies in Australia over the past few decades
About 45 nematode species have been reported in horses from various regions of Australia, of which approximately two-thirds belong to cyathostomins (Table 1)
GINs infecting Australian horses have been the subject of occasional studies over the past few decades, the effective control of GIN infections is hampered by a generalised lack of knowledge in various disciplines of equine parasitology, including (i) the current nation-wide prevalence and abundance status of equine GINs; (ii) the effect of biotic/abiotic epidemiological factors on GIN prevalence in horses; (iii) economic losses associated with clinical and subclinical GIN infections in horses; and (iv) the current status of anthelmintic resistance (AR) in nematode populations infecting horses

Summary

Introduction

Equine gastrointestinal nematodes (GINs) have been the subject of intermittent studies in Australia over the past few decades. We have systematically reviewed existing knowledge on the horse GINs recorded in Australia, and main aspects of their pathogeneses, epidemiology, diagnoses, treatment and control. Gastrointestinal nematodes (GINs) occur ubiquitously in horses (Equus caballus) and present a major veterinary concern throughout the world including in Australia. Due to conducive climatic conditions, GINs have been widely reported in horses from different agroclimatic regions across Australia [3, 4, 6–8]. These parasites have been associated with a variety of clinical signs, including unthriftiness, reduced stamina, retarded growth, abdominal distension (‘pot-belly’), diarrhea, abdominal pain and death, especially in young and immunocompromised horses [9–11]. Encysted cyathostomins cause larval cyathostominosis, a condition characterised by synchronous emergence of parasitic larvae from the large intestinal mucosa that can result in acute or chronic diarrhea, weight loss and, in some cases, death [4, 12–14]

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