The effect of previous cold storage on the subsequent recovery of infective third stage nematode larvae from sheep faeces.

An investigation undertaken to determine the effect of previous cold storage on the recovery of third stage larvae of gastrointestinal nematodes of sheep, showed that increasing periods of exposure of faeces to 4 degrees C resulted in decreasing numbers of larvae subsequently recovered from them. Differences in the abilities of the eggs of the various genera, to survive such treatment, were found to lead to significant changes in the percentage generic compositions of their third stage larvae--in some cases following the prior refrigeration of faecal samples for as little as 24 h. These results suggest that where larval cultures are intended to provide estimates of the proportions of the various worm eggs in the faeces of sheep harboring mixed gastrointestinal nematode burdens, they should be performed only on freshly collected samples.