Parasitology

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

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

Parasitology. 2019 Sep 06;:1-13

Authors: Tinsley RC, Rose Vineer H, Grainger-Wood R, Morgan ER

Abstract
The 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.

Glossaire technique

Composé de 2 parties
Catégorie systématique groupant plusieurs ordres ayant des caractères...
Manifestation pathologique due à l'action des microbes.
Organisme qui vit aux dépens d'un autre organisme et qui est souvent...
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