Comparison of Two Techniques Used for Quantification of Ovine Gastrointestinal Nematode Larvae in Herbage

Abstract

The assessment of populations of free living stages of gastrointestinal nematodes is important to predict uptake in livestock in relation to time and thus potential risk periods for trichostrongylosis. Several methods are currently used to assess the density of infective larvae (L3) of parasitic nematodes in herbage samples. Larval suspensions obtained by baermannization or similar sedimentation methods often contain considerable amounts of debris that make microscopic examination tedious and time consuming. To overcome this, Jorgensen (1975) developed the agar gel migration technique to obtain a suspension of L3 of Dictyocaulus viviparus free of debris. The migration from the agar film was later evaluated and found suitable for isolation of gastrointestinal nematodes of cattle and sheep (Mwegoha & Jørgensen 1977). The present study compares a Baermann method (Persson 1974) with the agar gel migration method for the isolation of ovine gastrointestinal nematode larvae from naturally contaminated herbage.