Trichostrongyloidea

PARASITES NEMATODES

General Appearance

• Bursate.
• Most members of this superfamily will look like short lengths of cotton (typically 0.5-2cm).
• The spicules of each species have a characteristic shape.
• The heads have no distinct features.

General Life-Cycle

• The egg is approximately 80µm long, oval, thin-shelled, contains 4-16cells (i.e. it is a typical strongyle egg).
• Egg → L1 → L2 → L3 (this occurs on the ground).
• The L1 and L2 feed on bacteria.
• The L3 is the infective stage.
• The L3 is ensheathed (i.e. the L2 cuticle is retained after moulting as an "outer skin").
• The L3 cannot feed, but has a finite amount of food stored to provide energy for movement.
• Infection is by ingestion of the L3.
• L3 → L4 → adult (this occurs in the stomach or small intestine).
• Parasitic development initially occurs in gastric glands or intestinal crypts (depending on species).
• Adults are on the mucosal surface.
• The prepatent period is typically about 3weeks.

Nematodirus

• Dictyocaulus viviparus causes parasitic bronchitis
• Dictyocaulus arnfieldi causes cough in horses