DEVELOPMENT AND SURVIVAL AT LOW-TEMPERATURE OF THE FREE-LIVING STAGESOF TRICHOSTRONGYLUS-TENUIS

To test the ability of Trichostrongylus tenuis eggs to survive and dev elop at temperatures similar to those they might experience in late wi nter on a grouse moor, they were exposed in replicate faecal cultures to various low temperature regimes in the laboratory. Yields in experi mental cultures were compared with those in control cultures incubated at 21 to 23-degrees-C. Eggs in caecal faeces were also placed outside on grass plots at intervals through the winter. In addition to this, infective larvae (1,3), also in replicate faecal cultures, were subjec ted to similar low temperature regimes. The results confirm that few, if any, eggs deposited from November to January are likely to develop successfully, but increasing numbers of those deposited from February onwards are likely to do so and to give rise to L3 in May. 1,3 were sh own to have the potential to survive the winter in significant numbers . It is suggested that infection newly acquired during the winter may represent a very significant part of the worm population found in adul t birds in early summer.