Issue |
Vet. Res.
Volume 31, Number 1, January-February 2000
|
|
---|---|---|
Page(s) | 149 - 150 | |
DOI | https://doi.org/10.1051/vetres:2000064 | |
How to cite this article | Vet. Res. (2000) 149-150 |
Modelling pseudorabies virus infection supports eradication
A. Van Nesa, M.C.M. De Jongb and J.H.M. Verheijdenaa Department of Farm Animal Health, Utrecht University, 7 Yalelaan, 3584 CL Utrecht, The Netherlands
b Department of Immunology, Pathobiology & Epidemiology, Epidemiology, Statistics, and Modelling group, ID-DLO, Lelystad, The Netherlands
Abstract -
Mathematical methods benefit the interpretation of results from experiments and
observations under field conditions and thus enhance our understanding of the spread of
infections within and between herds. Moreover, a mathematical model quantifies the impact
of risk factors
and thus determines whether or not the risk factor is a jeopardy for eradication. In this
paper, we used a stochastic SIR model. The reproduction ratio between pigs
can be calculated from
this model. This reproduction ratio is defined as the mean number of pigs that is infected
by one typical infectious pig. When
, infection fades out and eradication will succeed, when
an infection can spread. Hence, eradication is certain if
is smaller than 1. However,
when
is larger than 1, eradication can still succeed when R between herds
is below 1. Of
course, when
, eradication will be more rapid than when
and
.
Measures to eradicate PRV aim to reduce
or
to below 1. The following conclusions can be drawn
from our experiments, observations and modelling with pseudorabies virus (PRV): -
Experimentally, it was shown that the number of pigs in a population (with a constant
density of pigs per
m
2) did not influence the reproduction ratio of PRV. There was, however, a significant
difference in transmission between vaccinated not maternally immune SPF pigs and vaccinated maternally
immune conventional pigs. Earlier experiments had already shown that transmission in
maternally immune SPF pigs, which were vaccinated twice, was below one.
Corresponding author: A. Van Nes Tel.: (31) 30 2531248; fax: (31) 30 2521887;
e-mail: A.vanNes@vet.uu.nl
© INRA, EDP Sciences 2000