ISSN 2398-2993      

Strongyloides spp


Ash Phipps

Andrew Forbes




  • Phylum: Nematoda.
  • Class: Secernentea.
  • Order: Rhabditida.
  • Superfamily: Strongyloidea.
  • Family: Strongyloidea.
  • Genus: Strongyloides.
  • Species: S. papillosus.

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Clinical Effects



  • Parasitic adults inhabit the small intestine.
  • The free-living adults live in organic matter outside the host.
  • Eggs of parasitic phase are passed in the feces.
  • L3 inhabit the feces and surrounding herbage.


  • Prepatent period = approximately 1-2 weeks.
  • Unique lifecycle; parasitic and free-living reproductive cycles.
  • Female worms are parasitic.
  • Adult female worms produce larvated eggs by parthogenesis (development from an unfertilized egg).
  • The larvated eggs are passed in the feces of cattle and from the free-living phase, into the environment.
  • L1 hatch from the eggs within the feces and may develop into infective L3 or become free-living males or females.
  • The free-living males and females live in organic matter and produced fertilized eggs that hatch and develop in to the infective form L3.
  • Cattle ingest the L3 from the pasture or the L3 penetrate the skin of the host.
  • In adult cattle, the L3 accumulate in subcutaneous tissues and migrate to the mammary gland once lactation commences. This allows neonates to become infected by ingestion via the milk.
  • In young animals where skin penetration occurs, they travel via the blood to the respiratory system where they puncture the alveoli and ascend the upper respiratory tract where they are then swallowed.
  • The L3 travel to the small intestine and develop into adults.


  • Ingestion of infective larval stage or percutaneous infection of the infective larval stage.

Pathological effects

  • Diarrhea, reduced growth rates and dullness are common clinical sign observed in young animals.
  • Dermatitis with pruritus may be observed in any animal with many infective larvae present in the subcutaneous tissues.
  • Migrating larvae (particularly through the respiratory system) can induce coughing. Severe burdens may result in deaths in calves.
  • In bulls, balanoposthitis Balantis, posthitis and balanoposthitis has been recorded.


Control via animal

  • Treatment of adult female cattle to prevent the transmission of infective larvae via milk to calves.

Control via chemotherapies

  • Numerous broad spectrum anthelmintic are effective against adult worms and larvae. The products available will vary depending on the country.

Control via environment

  • Avoid overstocking pens and paddocks.
  • Reduce areas of damp litter or bedding in the calf rearing facilities.


  • No vaccine currently available.


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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Van wyk J A & Mayhew E (2013) Morphological identification of parasitic nematode infective larvae of small ruminants and cattle: A practical lab guide. Onderstepoort J Vet Res 80 (1), 1-14 PubMed.

Other sources of information

  • Junquera P (2018) Strongyloides spp, parasitic threadworms of horse, cattle, sheep, goats and pigs and poultry. Biology, prevention and control. Strongyloides papillosus, Strongyloides ransomi, Strongyloides avium. [online]. Website: Last accessed 28 January 2018.
  • Parkinson T J, Vermunt J J & Malmo J (2010) Diseases of cattle in Australasia: a comprehensive textbook. New Zealand veterinary association foundation for continuing education. pp 155.
  • Anderson D E & Rings M (2008) Current veterinary therapy: food animal practice. Elsevier health sciences. pp 82.
  • Radostits O M, Gay C C, Hinchcliff K W & Constable P D (eds) (2006) Veterinary medicine: a textbook of the diseases of cattle, horses, sheep, pigs and goats. Elsevier health sciences. pp 1562-1563.
  • Foreyt W (2001) Veterinary parasitology reference manual. 5th edn. Blackwell publishing company. pp 82.
  • Urquhart G, Armour A, Duncan J, Dunn A & Jennings F (1996) Veterinary parasitology. 2nd edn. Blackwell publishing company. pp 65-67.

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