Regulation and Stability of Host-Parasite Population Interactions: II. Destabilizing Processes

10.2307/3934 ◽  
1978 ◽  
Vol 47 (1) ◽  
pp. 249 ◽  
Author(s):  
Robert M. May ◽  
Roy M. Anderson
Keyword(s):  
Parasite Population ◽  
Population Interactions ◽  
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.

Population interactions between a parasitic castrator, Probopyrus pandalicola (Isopoda: Bopyridae), and one of its freshwater shrimp hosts, Palaemonetes paludosus (Decapoda: Caridea)

Parasitology ◽  
1979 ◽  
Vol 79 (3) ◽  
pp. 431-449 ◽  
Author(s):  
J. T. Beck
Keyword(s):  
Host Population ◽  
Acartia Tonsa ◽  
Parasite Control ◽  
Freshwater Shrimp ◽  
Free Swimming ◽  
Host Parasite Interactions ◽  
Population Interactions ◽  
Parasitic Castrator ◽  
Host Parasite ◽  
And Control

SUMMARYFreshwater shrimp, Palaemonetes paludosus, infected by the bopyrid isopod, Probopyrus pandalicola, occurred as far as 33 km upstream in many coastal rivers and canals throughout Florida. Free-swimming isopod larvae and the intermediate copepod host, Acartia tonsa, were collected in the plankton of the Wakulla River, and it appeared that cryptoniscus larvae swam at least as far as 13 km upstream to infect the definitive shrimp host after leaving the copepod in brackish water. In the Wakulla River infection levels ranged from 87·5 to 100%. In contrast, at McBride's Slough infection levels fluctuated from 0·9 to 93·2%. In the St Marks River the frequency of infected shrimp gradually increased from 0% upstream to 96%, 6 km further downstream. A significantly greater percentage of female than male hosts were infected, but only females of size classes less than 31 mm long had a greater frequency of infection. Female P. pandalicola were greatly under-dispersed (coefficient of dispersion (s2/x¯) less than 1) throughout the host population; 99·6% of the infected hosts carried only 1 female parasite. Control of P. pandalicola at the infrapopulation level is probably accomplished by some mode of intraspecific competition, and control at the suprapopulation level occurs through an upstream limitation of the transmission range of the cryptoniscus larval stage. Host–parasite interactions appear to be unstable.

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
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