Here, the parameter space is four-dimensional, so we cannot plot the confidence region. Since we are interested in determining the parameters directly influencing FIV prevalence in females, we simply plot the projection of the confidence region in the female transmission rate (b F , e F ) parameter space (Fig. 5) . 5 shows that there is an important dependency between b F and e F . Increasing the value of e F increases the mean prevalence in females and so the parameter b F must be decreased in order to explain the observed data. As a first approximation, the confidence region can be characterized by the relationship 0:015ƒb F z3:46e F ƒ0:11.