Experimental Embryonation and Survival of Eggs of Capillaria-Hepatica (Nematoda) Under Mouse Burrow Conditions in Cereal-Growing Soils

Abstract

The apparent absence of the nematode Capillaria hepatica in mice from regions of south-eastern Australia where plagues occur may be due to constraints on embryonation and survival of eggs in the mouse burrow, where C. hepatica is thought to be transmitted. Excavation of mouse burrows in the mallee wheatlands indicated that nest chambers generally were at depths of 200-400 mm. At these depths minimum and maximum weekly soil temperatures during the main period of mouse breeding ranged from 15 to 36.5°C and soil moisture contents were 14.5-32.8%. Embryonation and survival of C. hepatica eggs were assessed in the laboratory in three types of soil over these ranges of soil temperature and soil moisture content, emulating conditions of the mouse burrow. Two of the soil types, Walpeup sandy loan and Deniliquin riverine clay, are representative of the light and heavy soils, respectively, where mouse plagues occur in south-eastern Australia. The third type of soil was a potting mixture previously used experimentally and known to support a high rate of transmission of C. hepatica. Eggs were able to embryonate, and embryonated eggs to survive for 30 days, in each type of soil across the ranges of temperature and moisture content. The results further support the potential of C. hepatica to be used tactically in suppressing mouse numbers in the cereal-growing regions of south-eastern Australia.