Ascaris suum: seasonal egg development rates in a Saskatchewan pig barn

This study investigated the effects of seasonal temperature variations on t he rate of development to infectivity of Ascaris suum eggs under western Ca nadian climatic conditions, masks containing a suspension of A. suum eggs w ere placed inside a pig barn located near Saskatoon, Saskatchewan, Canada, at monthly intervals from July 1997 to July 1998. Eggs from each flask were monitored weekly for development to the infective larval stage. Infectivit y of eggs was confirmed using a mouse bioassay. Development to the infectiv e stage took three to four weeks in summer when in-barn temperatures were s imilar to the external ambient temperature. Fall, winter and early spring e gg development took longer as in-barn temperatures were cooler. Mid-winter egg development took as long as 11-12 weeks. The in-barn mean temperature d uring this period was approximately 17 degrees C, close to the development threshold of A. suum eggs. These data are discussed in relation to similar studies from northern Europe and to potential control measures. (C) 1999 El sevier Science B.V. All rights reserved.