Equis ISSN 2398-2977

Strongyle infestation: large

Synonym(s): Redworms Cyathostome

Contributor(s): Roberta Baxter, Melissa Kennedy, Craig Reinemeyer

Introduction

  • This is the most potentially pathogenic endoparasitic disease of horses.
  • Cause: a variety of species of equine redworms, divisible into large and small strongyles.
  • Signs: ill thrift, diarrhea, colic, and can be serious or even fatal.
  • Disease is seen in animals of all ages but may be particularly severe in young animals.
  • Diagnosis: clinical signs and presence of strongyle eggs in feces. See also:
  • Treatment: endoparasiticides are used, and good pasture management is also necessary for control.

Pathogenesis

Etiology

Large strongyles

  • Strongylus vulgaris- common.
  • Strongylus edentatus- common.
  • Strongylus equinus- rare.

Small strongyles

Predisposing factors

General
  • Overstocking.
  • Poor pasture management.

Pathophysiology

  • Adult worms in large intestine feed by permanent attachment and can cause loss of protein and blood, as well as changes in gut motility.
  • Large strongyle larve migrate through the body potentially causing damage to gut walls, arteries and other tissues, eg liver, brain.
  • Small strongyle larve become encysted in the gut wall causing damage and inflammation, particularly when they emerge in large numbers from the cysts.
Large strongyles
  • Adults in large intestine consume protein and cause bowel wall damage, anemia and hypoproteinemia, and can cause a direct effect on bowel motility by release of certain chemicals.
  • Eggs are passed in feces and develop on pasture to infective larve, particularly in autumn and spring, and during summer months. A percentage of infective larve can survive the winter on pasture.
  • Horses ingest infective larve; these migrate from the gut through the submucosal arterioles and into the arterial system. In the case ofStrongylus vulgaristhey migrate via the cecal, colic, and cranial mesenteric arteries. This migration causes inflammation within the blood vessels which can result in vascular occlusions and aneurysms, and thus inflammation, ischemia and infarction, particularly of the distal small colon, cecum and ventral colon. This can cause colic due to loss of blood supply to portions of bowel, and blood loss through damaged arteries may occur.Strongylus edentatusmigrate via the portal vein, liver and peritoneum. Hepatitis and peritonitis can also result in the case ofS. edentatus.
  • Larve then return to the gut where they develop to adults.

Small strongyles

  • Adults live in the large intestine, cause inflammation and damage and pass eggs in the horse's feces.
  • These develop into infective larve on pasture.
  • The horse ingests infective larve, and they migrate from the gut lumen into the gut wall where they become encysted, causing gut wall damage via damage to the lamina of the tubule glands and inflammation and goblet cell hypertrophy. They can overwinter in this state.
  • Emergence of large numbers of larve from the gut wall in spring leads to further inflammation (eosinophilic) of the gut wall and often diarrhea.

Timecourse

  • Prepatent period ofS. vulgarisis 6 months; that ofS. edentatusis 11 months and that ofS. equinusis 9 months.
  • Prepatent period of small strongyles is 6-12 weeks.

Epidemiology

  • Strongyles have direct life cycles - no intermediate host is needed for transmission.
  • Overwintering of infective larve can occur to a limited extent on pasture, larve can survive up to 2 years. Small strongyles can overwinter as encysted larve.
  • Emergence of large numbers of infective larve in spring can lead to severe disease.
  • Infection levels vary with location and season. Highest numbers in Spring and Autumn. Also high risk during Summer (Northern US) and Winter (Southern US).

Diagnosis

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Treatment

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Prevention

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Outcomes

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kaplan R M, West E M, Norat-Collazo L M & Vargas J (2014)A combination treatment strategy using pyrantel pamoate and oxibendazole demonstrates additive effects for controlling equine cysthostomins.Equine Vet Educ26(9), 485-491WileyBlackwell
  • Conwell R (2009)A case of larval cysthostominosis.UK Vet14(4), 4-8 WileyBlackwell.
  • Lloyd S (2009)Effects of previous control programmes on the proportion of horses shedding small numbers of strongyle-type eggs.Vet Rec164(4), 108-111 PubMed.
  • Schumacher J, Livesey L, DeGraves F, Blagburn B, Ziska S, Caldwell M & Brock K (2009)Efficacy of moxidectin against cyathostomins after long-term use in a large herd of draught horses with a high stocking density.Vet Rec164(21), 652-654 PubMed.
  • Molento M B, Antunes J, Bentes R N & Coles G C (2008)Anthelmintic resistant nematodes in Brazilian horses.Vet Rec162(12), 384-385 PubMed.
  • Roetting A K, Freeman D E, Constable P D, Moore R M, Eurell J C, Walling M A & Hubert J D (2008)The effects ofStrongylus vulgarisparasitism on eosinophil distribution and accumulation in equine large intestinal mucosa.Equine Vet J40(4), 379-384 PubMed.
  • Bairden K, Davies H S, Gibson N R, Hood A J O & Parker L D (2006)Efficacy of moxidectin 2 per cent oral gel against cyathostomins, particularly third-stage inhibited larvae, in horses.Vet Rec158(22), 766-768 PubMed.
  • Kaplan R M & Little S E (2000)Controlling equine cyathostomes.Comp Cont Educ Pract Vet22(4), 391-395 VetMedResource.
  • Fernandez Set. al(1999)A new isolate of the neamtophagous fungusDuddingtonia flagransas biological control agent against free-living larvae of horse strongyles.Equine Vet J31(6), 488-491 PubMed.
  • Lind O E, Hoglund J, Liungstrom B L, Nilsonn O & Uggla A (1999)A field study on the distribution of strongyle infections of horses in Sweden and factors affecting fecal egg counts.Equine Vet J31(1), 68-72 PubMed.
  • Proudman C J (1999)The role of parasites in equine colic.Equine Vet Educ11(4), 219-224 VetMedResource.
  • Craven J, Bjorn, Henriksen S A, Nansen P, Larsen M and Lendal S (1998)Survey of anthelmintic resistance on Danish horse farms, using 5 different methods of calculating fecal egg count reduction.EVJ30(4), 289-293 PubMed.
  • Duncan J L, Bairden K & Abbott E M (1998)Elimination of mucosal cyathostome larvae by five daily treatments with fenbendazole.Vet Rec142(11), 268-271 PubMed.
  • Thamsborg S M, Leifsson P S, Groendahl C, Larsen M & Nansen P (1998)Impact of mixed strongyle infections in foals after one month on pasture.Equine Vet J30(3), 240-245 PubMed.
  • Murfy D and Love S (1997)The pathogenic effects of experimental cyathostome infections in ponies.Vet Parasitol70(1-3), 99-110 PubMed.
  • Herd R P and Coles G C (1995)Slowing the spread of anthelmintic resistant nematodes of horses in the United Kingdom.Vet Rec136(19), 481-485 PubMed.
  • Van Loon G, Deprez P, Muylle E and Sustronck B (1995)Larval cyathostomiasis as a cause of death in two regularly dewormed horses.Zentralbl Veterinarmed A42(5), 301-306 PubMed.
  • Herd R P (1986)Epidemiology and control of equine strongylosis at Newmarket.Equine Vet J18(6), 447-452 PubMed.

Other sources of information

  • Rose R J & Hodgson D R (1993)Manual of Equine Practice.Saunders. ISBN 0 7216 3739 6.
  • Urqhart G M, Armour J, Duncan J L, Dunn A M & Jennings F W (1988)Veterinary Parasitology.Longmann Scientific and Technical. ISBN 0 5824 0906 3.


ADDED