Horses:

ONCHOCERCA SPECIES

General

  • One species, O. cervicalis (= O.reticulata).
  • Large filarial nematode (<30cm); ligamentum nuchae (and limb connective tissue).

Life-Cycle

  • Indirect LC, similar to that fo cattle Onchocerca (which are different species).
  • Intermediate host = midge (Culicoides species).

Pathogenicity

  • Limited significance.
  • Localised hypersensitivity (oedematous) reaction - to dead/dying microfilariae along ventral abdominal midline (sometimes occurs after ivermectin treatment for general worm control).
  • Corneal opacity (very rare in UK) - associated with microfilariae.