Environmental tolerance of free-living stages of the poultry roundworm Ascaridia galli

The poultry roundworm Ascaridia galli is re-emerging in laying hens in many European countries due to the increase in non-caged housing. A series of in vitro experiments was carried out to study the in ova larval development (embryonation) under different environmental conditions. Between 83% and 96% of the eggs developed to L-3 within 7-21 days of incubation in water between 20 and 30 degrees C. Twenty-six percent completed development at 33 degrees C and 4% at 35 degrees C after 31 days. At 15 degrees C parasite egg development was low with 8% L-3 after 56 days. In another trial larval development occurred, when parasite eggs were exposed to freeze-thaw cycle (30' to 12 h) followed by incubation for 2 weeks at 25 degrees C. Alkaline and acidic conditions in the range of pH 2.5-12.5 had no adverse effect on development. Oxygen and relative humidity above 70% were necessary for development to occur. Thus, some A. galli eggs may complete development at conditions prevailing in poultry barns in temperate climate zones throughout the year. Although exposure to a 1% or 2% dilution of the broad-spectrum disinfectant chlorocresol for 4 h or longer was ovicidal, further work is required to improve the method of application in the field. (C) 2015 Elsevier B.V. All rights reserved.