Ascariasis: the development of eggs of Ascaris suum under the conditions prevailing in a pig house.

Eggs were collected from gravid female Ascaris suum in the abattoir. Cultures were prepared with the eggs in 2 to 3 mm depth of 1 per cent sulphuric acid or on the surface of 2% aqueous agar. They were allowed to develop in a piggery, fresh cultures being started at intervals from January to September. Eggs on the surface of agar developed failry uniformly and a high proportion eventually reached L2. In contrast those under 1% sulphuric acid were less uniform, slower in development and generally less successful. Cultures started on agar between January and May, or from September became infective at approximately the same time in July while those started during June and July contained infective eggs in August and September respectively. No recognisable development occurred between October and April. The significance of these findings for the epidemiology of ascariasis is discussed.