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Biomedical subjects

F van den Bosch

Publications and source records attributed to F van den Bosch.

7 recordsLinked to original sources
PubMed2007

Disease control and its selection for damaging plant virus strains in vegetatively propagated staple food crops; a theoretical assessment.

Viral diseases are a key constraint in the production of staple food crops in lesser developed countries. New and improved disease control methods are developed and implemented without consideration of the selective pressure they impose on the virus. In this paper, we analyse the evolution of within-plant virus titre as a response to the implementation of a range of disease control methods. We show that the development of new and improved disease control methods for viral diseases of vegetatively propagated staple food crops ought to take the evolutionary responses of the virus into consideration. Not doing so leads to a risk of failure, which can result in considerable economic losses and increased poverty. Specifically in vitro propagation, diagnostics and breeding methods carry a risk of failure due to the selection for virus strains that build up a high within-plant virus titre. For vegetatively propagated crops, sanitation by roguing has a low risk of failure owing to its combination of selecting for low virus titre strains as well as increasing healthy crop density.

Animals↗
PubMed2004

Transmission rates and adaptive evolution of pathogens in sympatric heterogeneous plant populations.

Diversification in agricultural cropping patterns is widely practised to delay the build-up of virulent races that can overcome host resistance in pathogen populations. This can lead to balanced polymorphism, but the long-term consequences of this strategy for the evolution of crop pathogen populations are still unclear. The widespread occurrence of sibling species and reproductively isolated sub-species among fungal and oomycete plant pathogens suggests that evolutionary divergence is common. This paper develops a mathematical model of host-pathogen interactions using a simple framework of two hosts to analyse the influences of sympatric host heterogeneity on the long-term evolutionary behaviour of plant pathogens. Using adaptive dynamics, which assumes that sequential mutations induce small changes in pathogen fitness, we show that evolutionary outcomes strongly depend on the shape of the trade-off curve between pathogen transmission on sympatric hosts. In particular, we determine the conditions under which the evolutionary branching of a monomorphic into a dimorphic population occurs, as well as the conditions that lead to the evolution of specialist (single host range) or generalist (multiple host range) pathogen populations.

Adaptation, Physiological↗
PubMed2002

Quasi-steady state approximation to a fungal growth model.

In a previous paper, we proposed a fungal growth model (Lamour et al., 2001 IMA J. Math. Appl. Med. Biol., 17, 329-346), describing the colonization and decomposition of substrate, subsequent uptake of nutrients, and incorporation into fungal biomass, and performed an overall-steady-state analysis. In this paper we assume that where nutrient dynamics are much faster than the dynamics of fungal biomass and substrate, the system will reach a quasi-steady-state relatively quickly. We show how the quasi-steady-state approximation is a simplification of the full fungal growth model. We then derive an explicit fungal invasion criterion, which was not possible for the full model, and characterize parameter domains for invasion and extinction. Importantly, the fungal invasion criterion takes two forms: one for systems where carbon is limiting, another for systems where nitrogen is limiting. We focus attention on what happens in the short term immediately following the introduction of a fungus to a fungal-free system by analysing the stability of the trivial steady state, and then check numerically whether the fungus is able to persist. The derived invasion criterion was found to be valid also for the full model. Knowledge of the factors that determine invasion is essential to an understanding of fungal dynamics. The simplified model allows the invasion criterion to be tested with experimental data.

Carbon↗
PubMed2001

Mathematical conservation ecology: a one-predator-two-prey system as case study.

A method is presented to analyse the long-term stochastic dynamics of a biological population that is at risk of extinction. From the full ecosystem the method extracts the minimal information to describe the long-term dynamics of that population by a stochastic logistic system. The method is applied to a one-predator-two-prey model. The choice of this example is motivated by a study on the near-extinction of a porcupine population by mountain lions whose presence is facilitated by mule deer taking advantage of a change in land use. The risk of extinction is quantified by the expected time of extinction of the population.

Animals↗
PubMed1997

Insect-pathogen dynamics: stage-specific susceptibility and insect density dependence.

The control of insect pests by using insect pathogens as dynamic biological control agents is a recent effort. Model studies on insect-pathogen relations can help in the development of biocontrol programs. Except for the work of Briggs and Godfray [1], insect-pathogen models ignore the stage-specific susceptibility of insects. Moreover most models do not incorporate insect self-regulation. We develop stage-structured models of insect-pathogen relations incorporating insect-density dependence and disease transmitted through direct contact between susceptible and infective individuals. The models are analyzed by using steady-state and stability analysis. Numerical solutions are used as sources of further insight into the dynamics of the insect-pathogen systems. It is shown that there are major differences in the dynamics of adult- and juvenile-infecting diseases. Moreover, the interplay between insect-density dependence and stage-specific susceptibility has important consequences for the dynamics of insect-pathogen systems.

Agriculture↗
PubMedDate not supplied

An algorithm for drug waste reduction using pharmacokinetic principles.

When delivering several intravenous drug doses from a single bag, it is generally necessary to throw away any drug that remains in the bag, if the amount is insufficient to deliver the next dose. An algorithm has been developed to allow all of the drug in a bag to be used. Based on standard pharmacokinetic equations, the algorithm calculates the time when the remainder should be given, so that a desired peak serum drug concentration is achieved on the next dose. The algorithm requires as inputs the time limit on the bag, the dosing interval and the size of the dose. This algorithm applies only to drugs that obey single compartment, first-order linear kinetics (e.g. aminoglycosides), but is easily modified for other situations. In conjunction with computer-assisted infusion, use of the algorithm may potentially reduce the cost of aminoglycoside administration by reducing clinical drug waste.

Algorithms↗