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Helminth egg excretion with regard to age, gender and management practices on UK Thoroughbred studs

  • V. E. RELF (a1), E. R. MORGAN (a2), J. E. HODGKINSON (a3) and J. B. MATTHEWS (a1)

Few studies have described the combined effect of age, gender, management and control programmes on helminth prevalence and egg shedding in grazing equines. Here, fecal samples collected from 1221 Thoroughbred horses, residing at 22 studs in the UK, were analysed. The distribution of strongyle eggs amongst individuals in relation to age, gender and management practices was investigated. Fecal worm egg counts (FWECs), described as the number of eggs per gramme (epg) of feces, were determined using a modification of the salt flotation method. The FWEC prevalence (mean%) of strongyles, Parascaris equorum, tapeworm spp. and Strongyloides westeri was 56, 9, 4 and 8%, respectively. Strongyle, P. equorum, tapeworm spp. and S. westeri infections were detected on 22 (100%), 11 (50%), 9 (41%) and 8 (36%) of studs, respectively. Within all age and gender categories, strongyle FWECs were highly over-dispersed (arithmetic mean = 95 epg, aggregation parameter k=0·111) amongst horses. Animal age, last anthelmintic type administered and management practices (for example, group rotation on grazing) most strongly influenced strongyle prevalence and level of egg shedding (P < 0·05). Overall, 11% of equines (range: 234–2565 epg) were responsible for excreting 80% of the strongyle eggs detected on FWEC analysis. The results confirm that the judicious application of targeted treatments has potential to control equine strongyle populations by protecting individual horses from high burdens, whilst promoting refugia for anthelmintic susceptible genotypes.

Corresponding author
* Corresponding author: Moredun Research Institute, Pentlands Science Park, Midlothian EP26 0PZ, UK. Tel: +44 131 445 5111. Fax: +44 131 445 6235. E-mail:
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This list contains references from the content that can be linked to their source. For a full set of references and notes please see the PDF or HTML where available.

A. M. Becher , M. Mahling , M. K. Nielsen and K. Pfister (2010). Selective anthelmintic therapy of horses in the Federal states of Bavaria (Germany) and Salzburg (Austria): An investigation into strongyle egg shedding consistency. Veterinary Parasitology 171, 116122.

J. H. Boersema , M. Eysker , J. Maas and W. M. van der Aar (1996). Comparison of the reappearance of strongyle eggs on foals, yearlings and adult horses after treatment with ivermectin or pyrantel. Veterinary Quarterly 18, 79.

A. Bouman , M. J. Heineman and M. M. Faas (2005). Sex hormones and the immune response in humans. Human Reproduction Update 11, 411423. doi: 10.1093/humupd/dmi008.

D. G. Bucknell , R. B. Gasser and I. Beveridge (1995). The prevalence and epidemiology of gastrointestinal parasites of horses in Victoria, Australia. International Journal for Parasitology 25, 711724.

D. Döpfer , C. M. Kerssens , Y. G. M. Meijer , J. H. Boersema and M. Eysker (2004). Shedding consistency of strongyle-type eggs in Dutch boarding horses. Veterinary Parasitology 124, 249258.

M. Eysker , J. Bakker , M. van den Berg , D. C. K. van Doorn and H. W. Ploeger (2008). The use of age-clustered pooled faecal samples for monitoring worm control in horses. Veterinary Parasitology 151, 249255.

M. Eysker , J. H. Boersema and F. N. J. Kooyman (1992). The effect of ivermectin treatment against inhibited early third stage, late third stage and fourth stage larvae and adult stages of the cyathostomes in Shetland ponies and spontaneous expulsion of these helminths. Veterinary Parasitology 42, 295302.

B. Fritzen , K. Rohn , T. Schnieder and G. Von Samson-Himmelstjerna (2010). Endoparasite control management on horse farms – lessons from worm prevalence and questionnaire data. Equine Veterinary Journal 42, 7983. doi: 10.2746/042516409x471485.

W. D. Hamilton and M. Zuk (1982). Heritable true fitness and bright birds: a role for parasites. Science 218, 384387.

R. P. Herd and K. L. Willardson (1985). Seasonal distribution of infective strongyle larvae on horse pastures. Equine Veterinary Journal 17, 235237. doi: 10.1111/j.2042-3306.1985.tb02481.x.

B. Hinney , N. Wirtherle , M. Kyule , N. Miethe , K.-H. Zessin and P.-H. Clausen (2011). Prevalence of helminths in horses in the state of Brandenburg, Germany. Parasitology Research 108, 10831091. doi: 10.1007/s00436-011-2362-z.

R. M. Kaplan (2002). Anthelmintic resistance in nematodes of horses. Veterinary Research 33, 491507.

R. M. Kaplan (2004). Drug resistance in nematodes of veterinary importance: a status report. Trends in Parasitology 20, 477481.

S. L. Klein (2004). Hormonal and immunological mechanisms mediating sex differences in parasite infection. Parasite Immunology 26, 247264. doi: 10.1111/j.0141-9838.2004.00710.x.

S. Kornas , J. Cabaret , M. Skalska and B. Nowosad (2010). Horse infection with intestinal helminths in relation to age, sex, access to grass and farm system. Veterinary Parasitology 174, 285291.

T. A. Kuzmina and V. O. Kharchenko (2008). Anthelmintic resistance in cyathostomins of brood horses in Ukraine and influence of anthelmintic treatments on strongylid community structure. Veterinary Parasitology 154, 277288.

N. C. Kyvsgaard , J. Lindbom , L. L. Andreasen , L. A. Luna-Olivares , M. K. Nielsen and J. Monrad (2011). Prevalence of strongyles and efficacy of fenbendazole and ivermectin in working horses in El Sauce, Nicaragua. Veterinary Parasitology 181, 248254.

R. Lamason , P. Zhao , R. Rawat , A. Davis , J. Hall , J. Chae , R. Agarwal , P. Cohen , A. Rosen , E. Hoffman and K. Nagaraju (2006). Sexual dimorphism in immune response genes as a function of puberty. BMC Immunology 7, 2.

M. Larsen , S. Lendal , M. Chriel , S. Olsen and H. Bjorn (2002). Risk factors for high endoparasitic burden and the efficiency of a single anthelmintic treatment of Danish horses. Acta Veterinaria Scandinavica 43, 99106.

D. M. Leathwick , C. M. Miller , D. S. Atkinson , N. A. Haack , T. S. Waghorn and A. M. Oliver (2008). Managing anthelmintic resistance: Untreated adult ewes as a source of unselected parasites, and their role in reducing parasite populations. New Zealand Veterinary Journal 56, 184195. doi: 10.1080/00480169.2008.36832.

E. O. Lind , J. Höglund , B. L. Ljungström , O. Nilsson and A. Uggla (1999). A field survey on the distribution of strongyle infections of horses in Sweden and factors affecting faecal egg counts. Equine Veterinary Journal 31, 6872. doi: 10.1111/j.2042-3306.1999.tb03793.x.

S. Love , D. Murphy and D. Mellor (1999). Pathogenicity of cyathostome infection. Veterinary Parasitology 85, 113122.

E. T. Lyons , J. H. Drudge and S. C. Tolliver (1973). On the life cycle of Strongyloides westeri in the equine. Journal of Parasitology 59, 780787.

E. T. Lyons and S. C. Tolliver (2004). Prevalence of parasite eggs (Strongyloides westeri, Parascaris equorum and strongyles) and oocysts (Emeria leuckarti) in the feces of Thoroughbred foals on 14 farms in central Kentucky in 2003. Parasitology Research 92, 400404. doi: 10.1007/s00436-003-1068-2.

E. T. Lyons , S. C. Tolliver , J. Harold Drudge , D. E. Granstrom and S. S. Collins (1993). Natural infections of Strongyloides westeri: prevalence in horse foals on several farms in central Kentucky in 1992. Veterinary Parasitology 50, 101107.

J. B. Matthews (2008). An update on cyathostomins: Anthelmintic resistance and worm control. Equine Veterinary Education 20, 552560. doi: 10.2746/095777308x363912.

M. W. Mfitilodze and G. W. Hutchinson (1989). Prevalence and intensity of non-strongyle intestinal parasites of horses in northern Queensland. Australian Veterinary Journal 66, 2326. doi: 10.1111/j.1751-0813.1989.tb09708.x.

M. W. Mfitilodze and G. W. Hutchinson (1990). Prevalence and abundance of equine strongyles (Nematoda: Strongyloidea) in tropical Australia. Journal of Parasitology 76, 487494.

R. V. Monteiro , J. M. Dietz , B. B. Beck , A. J. Baker , A. Martins and A. M. Jansen (2007). Prevalence and intensity of intestinal helminths found in free-ranging golden lion tamarins (Leontopithecus rosalia, Primates, Callitrichidae) from Brazilian Atlantic forest. Veterinary Parasitology 145, 7785.

E. R. Morgan , L. Cavill , G. E. Curry , R. M. Wood and E. S. E. Mitchell (2005). Effects of aggregation and sample size on composite faecal egg counts in sheep. Veterinary Parasitology 131, 7987.

E. R. Morgan and R. Wall (2009). Climate change and parasitic disease: farmer mitigation? Trends in Parasitology 25, 308313.

M. K. Nielsen , N. Haaning and S. N. Olsen (2006). Strongyle egg shedding consistency in horses on farms using selective therapy in Denmark. Veterinary Parasitology 135, 333335.

M. K. Nielsen , R. M. Kaplan , S. M. Thamsborg , J. Monrad and S. N. Olsen (2007). Climatic influences on development and survival of free-living stages of equine strongyles: Implications for worm control strategies and managing anthelmintic resistance. The Veterinary Journal 174, 2332.

E. O. Lind , J. Höglund , B. L. Ljungström , O. Nilsson and A. Uggla (1999). A field survey on the distribution of strongyle infections of horses in Sweden and factors affecting faecal egg counts. Equine Veterinary Journal 31, 6872. doi: 10.1111/j.2042-3306.1999.tb03793.x.

C. J. Proudman and G. B. Edwards (1992). Validation of a centrifugation/flotation technique for the diagnosis of equine cestodiasis. Veterinary Record 131, 7172. doi: 10.1136/vr.131.4.71.

C. Reinemeyer (2009). Diagnosis and control of anthelmintic-resistant Parascaris equorum. Parasites and Vectors 2(Suppl. 2), S8.

V. E. Relf , E. R. Morgan , J. E. Hodgkinson and J. B. Matthews (2012). A questionnaire study on parasite control practices on UK breeding Thoroughbred studs. Equine Veterinary Journal 44, 466471. doi: 10.1111/j.2042-3306.2011.00493.x.

D. J. Shaw and A. P. Dobson (1995). Patterns of macroparasite abundance and aggregation in wildlife populations: a quantitative review. Parasitology 111(Suppl. S1), S111-S133.

D. J. Shaw , B. T. Grenfell and A. P. Dobson (1998). Patterns of macroparasite aggregation in wildlife host populations. Parasitology 117, 597610.

C. H. Stratford , B. C. McGorum , K. J. Pickles and J. B. Matthews (2011). An update on cyathostomins: Anthelmintic resistance and diagnostic tools. Equine Veterinary Journal 43, 133139. doi: 10.1111/j.2042-3306.2011.00397.x.

P. R. Torgerson , M. Paul and F. I. Lewis (2012). The contribution of simple random sampling to observed variations in faecal egg counts. Veterinary Parasitology 188, 397401.

P. R. Torgerson , M. Schnyder and H. Hertzberg (2005). Detection of anthelmintic resistance: a comparison of mathematical techniques. Veterinary Parasitology 128, 291298.

D. Traversa , T. R. Klei , R. Iorio , B. Paoletti , R. P. Lia , D. Otranto , O. A. E. Sparagano and A. Giangaspero (2007). Occurrence of anthelmintic resistant equine cyathostome populations in central and southern Italy. Preventive Veterinary Medicine 82, 314320.

J. van Dijk , N. D. Sargison , F. Kenyon and P. J. Skuce (2010). Climate change and infectious disease: helminthological challenges to farmed ruminants in temperate regions. Animal 4, 377392.

A. N. Vidyashankar , R. M. Kaplan and S. Chan (2007). Statistical approach to measure the efficacy of anthelmintic treatment on horse farms. Parasitology 134, 20272039.

G. von Samson-Himmelstjerna (2012). Anthelmintic resistance in equine parasites – detection, potential clinical relevance and implications for control. Veterinary Parasitology 185, 28.

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