A mathematical model of the population biology ofOstertagia ostertagiin calves and yearlings

Abstract

A mathematical model of the population biology of Ostertagia ostertagi is described. The model assumes that the natural control and regulation of parasite numbers is mediated by four processes: the effect of climate on the development and survival of the free-living stages; changes in the rate of establishment of the infective larvae, and density-dependent variations in parasite survival and fecundity. The model is used to compare the course of the infection in two groups of calves. One group is assumed to have been reared under conditions typical of S.E. England and the other under conditions typical of Louisiana, USA. The more general behaviour of the model is discussed in the context of sensitivity analysis. The model is an excellent mimic of the epidemiology of bovine ostertagiasis. It can be used as a simple screening procedure to help determine which of many possible anthelmintic control strategies should be selected for more detailed examination in the field, and it provides a theoretical framework within which ideas concerning the epidemiology of parasitic gastroenteritis can be assessed and refined.

The dynamics of nematode infections of farmed ruminants

“…Despite its lack = Q("0)+ goats. Simulation models must be tailored to a particular system and invariably contain many more parameters (see for example Grenfell et al (1987); Barnes & Dobson (1990) and and references therein). The simple model used here has been shown to display dynamical behaviour that is qualitatively correct (Roberts, 1994 b ;Roberts & Grenfell, 1991 ;1992).…”

Cattle and Nematodes Under Global Change: Transmission Models as an Ally

“…What exactly demonstrates a model's validity is a matter of discussion and is rather related to the intended applications and users of the model than to the model itself [30]. The model of Grenfell et al [31], for example, was not validated against any observations. Later on, the authors argued that whether 'a model is able to generate patterns that would be regarded as typical for a specific region by an experienced field worker', should be a criterion for validity of GIN models [32,33].…”

Exploiting parallels between livestock and wildlife: Predicting the impact of climate change on gastrointestinal nematodes in ruminants

“…immune response e.g. Singleton et al, 2011) is often represented implicitly by decreasing establishment rate as a function of the duration of infection (Grenfell et al, 1987), or explicitly as a single measure of resistance that increases and decays as a function of the duration of, or magnitude of exposure to, infective stages (Anderson and May, 1985; Roberts and Grenfell, 1991; Grenfell et al, 1995; Roberts and Heesterbeek, 1995). However, it is unclear to what extent the potential application of acquired immunity functions based on livestock ruminants can be extended to free-ranging ruminants.…”