Factors regulating tapeworm populations: estimations of the build-up and dispersion patterns of eggs after the introduction of dogs infected with Taenia hydatigena.

The build-up of the eggs of Taenia hydatigena was measured on a pasture following the introduction of infected dogs. Susceptible lambs grazed on the pasture beforehand showed that only small numbers of randomly dispersed infective eggs were present. Two dogs each with four patent T hydatigena were chained to kennels placed in the middle of the pasture. The build-up of eggs was determined by grazing further tapeworm-free lambs there for 10-day periods. High cyst counts were obtained in some of these lambs grazed within 10 days of the introduction of the infected dogs. The mean cyst counts remained at a similar level during the 85-day investigation. This indicated that at least part of the pasture became virtually saturated with eggs shortly after the dogs were introduced and remained so while the dogs were there. Some animal management practices that favour this 'epidemic' pattern and lead to a 'cysticercosis storm' are discussed.