An approach to the teaching of host/parasite population modelling

1989 ◽  
Vol 19 (4) ◽  
pp. 451-455 ◽  
Author(s):  
David A. Wharton ◽  
Graham Webb
Keyword(s):  
Parasite Population ◽  
Population Modelling ◽  
Host Parasite

Heterogeneity in helminth infections: factors influencing aggregation in a simple host–parasite system

Parasitology ◽  
2019 ◽  
Vol 147 (1) ◽  
pp. 65-77 ◽  
Author(s):  
Richard C. Tinsley ◽  
Hanna Rose Vineer ◽  
Rebecca Grainger-Wood ◽  
Eric R. Morgan
Keyword(s):  
Post Infection ◽  
Evolutionary Biology ◽  
Negative Binomial ◽  
Parasite Population ◽  
Trout Population ◽  
Helminth Infections ◽  
Transmission Period ◽  
Binomial Parameter ◽  
Host Parasite ◽  
Direct Life Cycle

AbstractThe almost universally-occurring aggregated distributions of helminth burdens in host populations have major significance for parasite population ecology and evolutionary biology, but the mechanisms generating heterogeneity remain poorly understood. For the direct life cycle monogenean Discocotyle sagittata infecting rainbow trout, Oncorhynchus mykiss, variables potentially influencing aggregation can be analysed individually. This study was based at a fish farm where every host individual becomes infected by D. sagittata during each annual transmission period. Worm burdens were examined in one trout population maintained in isolation for 9 years, exposed to self-contained transmission. After this year-on-year recruitment, prevalence was 100% with intensities 10–2628, mean 576, worms per host. Parasite distribution, amongst hosts with the same age and environmental experience, was highly aggregated with variance to mean ratio 834 and negative binomial parameter, k, 0.64. The most heavily infected 20% of fish carried around 80% of the total adult parasite population. Aggregation develops within the first weeks post-infection; hosts typically carried intensities of successive age-specific cohorts that were consistent for that individual, such that heavily-infected individuals carried high numbers of all parasite age classes. Results suggest that host factors alone, operating post-infection, are sufficient to generate strongly overdispersed parasite distributions, rather than heterogeneity in exposure and initial invasion.

scholarly journals Rapid change in parasite infection traits over the course of an epidemic in a wild host-parasite population

Oikos ◽  
2013 ◽  
Vol 123 (2) ◽  
pp. 232-238 ◽  
Author(s):  
Stuart K. J. R. Auld ◽  
Philip J. Wilson ◽  
Tom J. Little
Keyword(s):  
Rapid Change ◽  
Parasite Infection ◽  
Parasite Population ◽  
Wild Host ◽  
Host Parasite

scholarly journals Diversity patterns in parasite populations capable for persistence and reinfection with a view towards thehuman cytomegalovirus

2019 ◽  
Author(s):  
Cornelia Pokalyuk ◽  
Irene Görzer
Keyword(s):  
Balancing Selection ◽  
Parasite Population ◽  
Substantial Fraction ◽  
Diversity Patterns ◽  
Coding Regions ◽  
Evolutionary Advantage ◽  
Parasite Reproduction ◽  
Host Parasite ◽  
Parasite Populations ◽  
High Diversity

AbstractMany parasites like thecytomegalovirus, HIVandEscherichia coliare capable to persist in and reinfect its host. The evolutionary advantage (if so) of these complicated mechanisms have not been quantitatively analyzed so far. Here we take a first step by investigating a host-parasite model for which these mechanisms are driving the evolution of the parasite population. We consider two variants of the model. In one variant parasite reproduction is directed by balancing selection, in the other variant parasite reproduction is neutral. In the former scenario reinfection and persistence have been shown to sustain the maintenance of diversity in the parasite population in certain parameter regimes (Pokalyuk and Wakolbinger, 2018). Here we analyse the diversity patterns in the latter, neutral scenario. We evaluate the biological relevance of both model variants with respect to thehuman cytomegalovirus(HCMV), an ancient herpesvirus that is carried by a substantial fraction of mankind and manages to maintain a high diversity in its coding regions.

scholarly journals Biological control in a disturbed environment

1997 ◽  
Vol 352 (1364) ◽  
pp. 1935-1949 ◽  
Author(s):  
Simon Gubbins ◽  
Christopher A. Gilligan
Keyword(s):  
Biological Control ◽  
Alternative Hypothesis ◽  
Model Fitting ◽  
The Other ◽  
Parasite Population ◽  
Analysis Model ◽  
Interacting Populations ◽  
Predicted Values ◽  
Host Parasite ◽  
Disturbed Environment

Most ecological and epidemiological models describe systems with continuous uninterrupted interactions between populations. Many systems, though, have ecological disturbances, such as those associated with planting and harvesting of a seasonal crop. In this paper, we introduce host—parasite—hyperparasite systems as models of biological control in a disturbed environment, where the host—parasite interactions are discontinuous. One model is a parasite—hyperparasite system designed to capture the essence of biological control and the other is a host—parasite—hyperparasite system that incorporates many more features of the population dynamics. Two types of discontinuity are included in the models. One corresponds to a pulse of new parasites at harvest and the other reflects the discontinuous presence of the host due to planting and harvesting. Such discontinuities are characteristic of many ecosystems involving parasitism or other interactions with an annual host. The models are tested against data from an experiment investigating the persistent biological control of the fungal plant parasite of lettuce Sclerotinia minor by the fungal hyperparasite Sporidesmium sclerotivorum , over successive crops. Using a combination of mathematical analysis, model fitting and parameter estimation, the factors that contribute the observed persistence of the parasite are examined. Analytical results show that repeated planting and harvesting of the host allows the parasite to persist by maintaining a quantity of host tissue in the system on which the parasite can reproduce. When the host dynamics are not included explicitly in the model, we demonstrate that homogeneous mixing fails to predict the persistence of the parasite population, while incorporating spatial heterogeneity by allowing for heterogeneous mixing prevents fade–out. Including the host's dynamics lessens the effect of heterogeneous mixing on persistence, though the predicted values for the parasite population are closer to the observed values. An alternative hypothesis for persistence involving a stepped change in rates of infection is also tested and model fitting is used to show that changes in some environmental conditions may contribute to parasite persistence. The importance of disturbances and periodic forcing in models for interacting populations is discussed.

Behavioral stabilization of host-parasite population dynamics

1992 ◽  
Vol 42 (3) ◽  
pp. 308-320 ◽  
Author(s):  
Marc Mangel ◽  
Bernard D. Roitberg
Keyword(s):  
Population Dynamics ◽  
Parasite Population ◽  
Host Parasite

HOST LARVAL MORTALITY IN AN EXPERIMENTAL HOST–PARASITE POPULATION

1964 ◽  
Vol 42 (5) ◽  
pp. 745-765 ◽  
Author(s):  
T. Burnett
Keyword(s):  
Larval Mortality ◽  
Trialeurodes Vaporariorum ◽  
Parasite Population ◽  
Rapid Decline ◽  
Encarsia Formosa ◽  
Host Protection ◽  
Host Mortality ◽  
Host Parasite ◽  
Parasite Populations ◽  
Two Populations

Two populations of Trialeurodes vaporariorum (Westw.) and its chalcid parasite Encarsia formosa Gahan were reared on tomato plants in the greenhouse at 72–76 °F for 26 weeks. Although the abundance of both species fluctuated with peaks of increasing amplitude, the population that was initially larger remained so throughout the period of sampling because the parasite inflicted similar rates of mortality in both cases. The fluctuations of the two separate populations were synchronized throughout the period of propagation. Host mortality, which resulted either from almost immediate killing of host scales following attack by adult parasites or from death of host larvae following parasitization and development of parasite progeny, was determined by parasite density, host size, and possibly by a number of other factors such as the age structure of host larval populations, age of adult parasites, and succulence of leaves on which the host larvae developed. The interaction of host and parasite produced cycles in the age structures of host and parasite populations that, in turn, influenced the interaction of the two species. The death of host larvae following attack by adult parasites was a form of host protection, as it ensured the rapid decline in the abundance of the parasite population and was, therefore, the primary factor in the maintenance of the host–parasite system.

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