A new method for culture of larvae used in diagnosis of ruminant gastrointestinal strongylosis: comparison with fecal cultures.

A study was carried out in order to compare two techniques for culture of strongyle larvae: the usual fecal culture and a new one where eggs were extracted from feces and larvae were grown in a more defined medium (agar plate fortified with Earle's medium and yeast extract). The efficiency of "on-agar" cultures was better than that of the fecal cultures with a difference of 26% for Trichostrongylus colubriformis and 32% for Ostertagia circumcincta. The variability observed between the number of larvae collected from each culture was low (8% on average) in comparison with that of fecal cultures (15% on average) thus demonstrating a better reproducibility. On the other hand growth of the larvae was similar to that obtained in fecal medium. This new technique avoids the difficulty of controlling the conditions found in fecal cultures (particularly moisture) and could become a more accurate method for diagnosis than the conventional methods. A morphometric study of infective larvae derived from the two methods of culture was carried out. Despite the more defined conditions of development in the "on-agar" cultures, it was not possible to obtain sufficiently homogeneous populations with regard to their measurements so as to distinguish larvae merely with the help of these criteria.