Atlas of livestock parasites
digitized collection of microscopical preparations

Atlas of Parasites Contents Information sources Glossary Administration

Strongyloides papillosus (ruminants)



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Nematode (order Rhabditida)

"intestinal threadworm"

Distribution: worldwide, especially in warm, humid areas.

Host: Intestinal threadworms damage sheep in several ways and make sheep raising unprofitable in areas of high worm infection. 

Life Cycle:
Life cycle contains two types of adults: in small intestine parasitic and free-living. Parasitic females in the intestine are parthenogenetic (the eggs laid by them hatch and develop without fertilization). Hatched larvae may develop to become infective third-stage larvae which enter animals through ingestion or through skin penetration and become parasitic female worms (homogonic cycle). Hatched larvae, in the heterogonic cycle, develop into free-living male and female adults which grow and mate on pasture, producing eggs that become female infective third-stage larvae. Infective larvae, produced from either cycle, have a prepatent period of 7 to 9 days after entering the sheep by skin penetration. 

Diagnosis: Small, thread-like adults are up to 6 mm long. Only females are parasitic. Small, thin-shelled eggs containing larvae appear in feces.

Size: 47-65 µm x 25-26 µm, broad ellipse, slightly flattened poles, shell thin, colourless, embryonated, L1 larva present Strongyloides papillosus egg.

Clinical features: Adults cause erosion of the intestinal lining; diarrhea, which may be bloody, can follow. This persists and wasting occurs because sheep lose their appetite. Death may follow. Skin penetration causes dermatitis which results in intense itching, especially of feet. Damage incurred by penetrating larvae may predispose sheep to foot rot.

Prevention should include administration of anthelmintics and attempts to keep sheep areas dry and clean. Avoid overcrowding.


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