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 tenuis, a pathogen of red grouse, to survive the winter in significant numbers, the temperatures prevailing during the autumn, winter and spring of 1991–1992 on the North Yorkshire moors were simulated in an incubator into which replicate cultures of T tenuis eggs were placed at intervals. September and early October eggs developed into larvae which survived over winter and were infective the following spring. Few November to February eggs survived to become larvae but early March eggs were reasonably successful. Continuous temperatures of −15°C were lethal to infective larvae within 12 days, but significant numbers of larvae survived temperatures of −10°C or higher for up to three weeks and remained infective.