Abstract:
Vectored immunocontraception is a novel technology and simple models aredescribed to help predict whether, and how, it might work. That is, given thatan effective immunocontraceptive agent can be produced, and given that it canbe inserted into a microparasitic or macroparasitic infective vector, wouldthe vector persist and reach a high prevalence in the host and, if so, wouldit sterilize a sufficient proportion of the host breeding population tosignificantly reduce its density? Both conditions are necessary for success.The first question is an epidemiological one, relating solely to disseminatingsystems and differing according to whether the vector itself is newlyintroduced or pre-existing. If it is newly introduced, the assumption is thatit is present in some other geographical areas occupied by the same targetspecies, or is found in closely-related species. If the vector already existsin the population, the issue is one of competition between the engineered andwild-type vectors.The second question is an ecological one, common to both non-disseminating anddisseminating systems. Whatever level of sterilization the immunocontraceptionprovides must translate into a significant reduction in population density,having regard to the nature and extent of compensatory, density-dependencemechanisms in the population.These two questions, together with other more minor issues, are addressed inturn with particular reference to models for immunocontraception of brushtailpossums (Trichosurus vulpecula)in New Zealand.