Biomedical subjects

M B Bonsall

Publications and source records attributed to M B Bonsall.

4 recordsLinked to original sources

PubMed2006

Pathogen responses to host immunity: the impact of time delays and memory on the evolution of virulence.

Current analytical models of the mammalian immune system typically assume a specialist predator-prey relationship between invading pathogens and the active components of the immune response. However, in reality, the specific immune system is not immediately effective following invasion by a novel pathogen. First, there may be an explicit time delay between infection and immune initiation and, second, there may be a gradual build-up in immune efficacy (for instance, during the period of B-cell affinity maturation) during which the immune response develops, before reaching maximal specificity to the pathogen. Here, we use a novel theoretical approach to show that these processes, together with the presence of long-lived immune memory, decouple the immune response from current pathogen levels, greatly changing the dynamics of the pathogen-immune system interaction and the ability of the immune response to eliminate the pathogen. Furthermore, we use this model to show how distributed primary immune responses combine with immune memory to greatly affect the optimal virulence of the pathogen, potentially resulting in the evolution of highly virulent pathogens.

Animals↗

PubMed2005

Persistence and coexistence of engineered baculoviruses.

Baculoviruses, and in particular, the nucleopolyhedroviruses infect a wide range of arthropod hosts and have the potential to be used as biopesticides. However, one of the major drawbacks with these pathogens as biocontrol agents is that they have a slow response time. Alterations to the speed of kill and pathogen life history characteristics can influence the competitive outcome and persistence between wildtype and modified strains. Here, we explore, theoretically, how life-history modifications of pathogens can affect the epidemiology and ecology of strain coexistence. In particular, we show how under simple mass action disease transmission, life-history difference between strains are insufficient to allow coexistence. Additional heterogeneities in transmission are shown to be necessary to facilitate coexistence of wildtype and modified pathogen strains. We also illustrate how the patterns of infectivity of wildtype and modified strains can also affect long-term coexistence, and argue that appropriate assessment of genetic modifications must be presented in terms of relevant ecological theory.

Animals↗

PubMed2003

Contrasting dynamics in the same plant-herbivore interaction.

Long-term studies of two-species interactions under field conditions are unusual; most long-term field studies are of single species dynamics (1-6). Concurrent long-term studies on the dynamics of the same two interacting species in different locations are very rare. This result has led to the tacit assumption that different cases of the same two-species interaction would involve essentially quantitative differences (e.g., context-specific differences in the numeric values of demographic parameters like fecundity or death rates). Here, we show that for one of the best-known two-species systems (ragwort and cinnabar moth), this finding does not hold. The interaction between the plant and its herbivore is fundamentally different in coastal dunes in The Netherlands and in grasslands in Southeast England. In the first case, the dynamics are cyclic and the interaction involves both direct and delayed density dependence; in the second case, the insect has little impact on plant dynamics and there are no time lags in density dependence. The difference is caused by differences in the importance of seed-limitation in plant recruitment in the two locations.

Animals↗

PubMed2000

The effects of metapopulation structure on indirect interactions in host-parasitoid assemblages.

The interaction between two species that do not compete for resources but share a common natural enemy is known as apparent competition. In the absence of other limiting factors, such three-species interactions are impermanent, with one species being excluded from the assemblage by the natural enemy. Here, the effects of metapopulation structure are explored in a system of two hosts that experience apparent competition through a shared parasitoid. A coupled-map lattice model is developed and used to explore species coexistence and patterns of patch occupancy at the metapopulation scale. Linking local and regional dynamics favours coexistence by uncoupling the dynamics of the three species in space. Coexistence is promoted by the inferior species being either a fugitive or a sedentary species. The occurrence of these two mutually exclusive mechanisms of coexistence is influenced by the relative dispersal of the inferior apparent competitor.

Animals↗