FURTHER-STUDIES ON THE DEVELOPMENT AND SURVIVAL AT LOW-TEMPERATURES OF THE FREE-LIVING STAGES OF TRICHOSTRONGYLUS-TENUIS

To assess the ability of the free living stages of Trichostrongylus te nuis, a pathogen of red grouse, to survive the winter in significant n umbers, the temperatures prevailing during the autumn, winter and spri ng of 1991-92 on the North Yorkshire moors were simulated in an incuba tor into which replicate cultures of T tenuis eggs were placed at inte rvals. September and early October eggs developed into larvae which su rvived over winter and were infective the following spring. few Novemb er to February eggs survived to become larvae but early March eggs wer e reasonably successful. Continuous temperatures of -15 degrees C were lethal to infective larvae within 12 days, but significant numbers of larvae survived temperatures of -10 degrees C or higher for up to thr ee weeks and remained infective.