Identification of Infective Dictyo-Caulus Viviparus Larvae Isolated from Herbage By the Bile-Agar Technique

Abstract

A morphological description was given of the infective stage of the cattle lungworm Dictyocaulus viviparus. The larvae were stained with iodine and examined under an ordinary microscope after isolation with the bileagar technique used for processing herbage samples. Under these conditions the internal structures appeared of limited value to the identification. The larvae were characterized by their measurements as well as by their shape and profile. A comparison between larvae isolated from the field and larvae harvested from faecal cultures revealed that field larvae were smaller and more uniform in size. Of the reported characteristics the typical profile, the comparatively small size (range 305–400 µm), and the retaining of iodine stain were found most useful in routine recognition of D. viviparus infective larvae in isolates from herbage samples containing free living nematode species as well as infective stages of parasitic species.

Sammendrag

Der gives en morfologisk beskrivelse af det infektive stadium af kvægets lungeorm Dictyocaulus viviparus. Larverne blev farvet med jod, hvorefter de blev underkastet mikraskopisk undersøgelse efter at vaere isoleret med galdeagar-teknikken til undersøgelse af grsesprøver. Larvernes indre struktur viste sig af begraenset værdi til identifikation under disse forhold. Der blev givet en karakteristik af larverne ved hjælp af deres mål, form og profil. En sammenligning mellem larver isoleret fra henholdsvis mark og faeceskulturer viste, at larver fra graesmarker var mindre og mere ensartede i størrelse. Af de nævnte karakteristika viste den typiske profil, deres relativt lille størrelse (305–400 µm), samt deres bibeholdelse af jodfarven sig mest anvendelige til screening for infektive D. viviparus larver af isolater fra grassprøver indeholdende både fritlevende nematodearter og infektive stadier af parasitære arter.