Stochastic host-parasite interaction models |
| |
Authors: | Julian Herbert Valerie Isham |
| |
Institution: | (1) Department of Statistical Science, University College London, Gower Street, London WC1E 6BT, UK, GB |
| |
Abstract: | We contribute to the discussion of causes and effects of aggregation (overdispersion) of macroparasite counts, focussing
particularly upon the effects of clumped infections and parasite-induced host mortality. The simple nonlinear stochastic model
for the evolution of the parasite load of a single host, investigated in Isham (1995), is extended to allow three parasite
stages (larval, mature and offspring), and to allow durations of these stages to be non-exponentially distributed. As in the
earlier work, exact algebraic results are possible, providing insight into the aggregation mechanisms, as long as the only
source of interaction between host and parasites is an excess host mortality linearly related to the parasite load. Results
are obtained on the distribution of parasite lad and on host survival. In particular, although parasite-induced host mortality
is usually thought of as a process that reduces parasite aggregation (Anderson and Gordon 1982), it is shown that, for this
model, parasite-induced host mortality cannot cause the index of dispersion to fall below unity. Host heterogeneity and disease
control are also discussed. An approximation based on moment assumptions appropriate to a specially-constructed multivariate
negative binomial distribution is proposed. This approximation, which is applicable to other processes, and an alternative
based on the multivariate normal distribution are compared with exact results.
Received: 17 December 1998 / Revised version: 2 June 1999 |
| |
Keywords: | : Epidemic model Helminths Parasite-induced mortality Macroparasites Moment closure approximations Multivariate negative binomial distribution |
本文献已被 PubMed SpringerLink 等数据库收录! |
|