The influence of environmental temperature on the rate of development of Ascaris suum eggs in Great Britain.

The rate of development of Ascaris suum eggs was recorded during 18 months in England. Every second or third week unembryonated eggs were placed in an unheated animal house and their development was observed at weekly intervals. Eggs underwent no development during November to May. Embryonation was most rapid during June, July and August. The shortest time for eggs to reach the infective stage was two weeks in 1976 and four weeks in 1977. A relationship was apparent between the rate of development of eggs and the seasonal occurrence of pigs in chronic focal interstitial hepatitis, a condition associated with infection by A suum larvae.