The Effects of Capillaria-Hepatica (Nematoda) on Natality and Survival to Weaning in Balb/C Mice

Pathogenicity of the nematode Capillaria hepatica was assessed in female BALB/c mice in terms of the parasite's effect on natality and on survival of young to weaning. C. hepatica infection in female BALB/c mice maintained under standard laboratory conditions resulted in: a significant delay in production of second litters; a significant reduction in the number of live young born and in the number of live young weaned per female over a 90-day breeding period; a significant reduction in the number of live young weaned per litter; but no marked difference in the number of live young born per litter. Demographic studies and computer simulation models infer that 'mouse plagues' can be suppressed if productivity is maintained below an attainable threshhold. The magnitude of the reduction in 'productivity' caused by C. hepatica, and the slight variation in susceptibility of mouse strains to such infection, support the proposal that strategic use of C. hepatica may prevent formation of 'mouse plagues'. This postulate stems from carefully controlled laboratory studies but now requires confirmation from field studies.