Morphological differentiation from Onchocerca volvulus of first stage larvae of an unknown filarial species commonly found in Simulium sanctipauli s.l. in Liberia.

A filarial species of unknown origin was frequently found in Simulium sanctipauli s.l. in the rain-forest zone of Liberia. After staining the cephalic armature with alcian blue its first stage larvae could be easily distinguished from those of Onchocerca volvulus.