Schüpbach, Hans Ulrich. Life-history responses, transmission dynamics and epidemiology in a terrestrial gastropod infected with parasitic mites. 2010, PhD Thesis, University of Basel, Faculty of Science.
Official URL: http://edoc.unibas.ch/diss/DissB_8979
In the present thesis we investigated the impact of Riccardoella limacum, a parasitic mite of terrestrial gastropods, on life-history of Arianta arbustorum, a common host of R. limacum. Furthermore, we examined the transmission dynamics of R. limacum. Data on parasite-induced life-history responses in A. arbustorum and on parasite transmission were then combined in mathematical models, in order to predict the epidemiology and to assess disease relevant parameters, which may help to predict the course of R. limacum infections in A. arbustorum populations.
In order to assess the impact of R. limacum on the life-history of A. arbustorum, we quantified the reproductive output (number of eggs), the hatching success of the eggs and the activity of naturally infected snails. The reproductive output was reduced in infected snails, whereas the hatching success of the eggs was slightly increased in infected snails compared to parasite-free snails. Snail behavior differed between infected and parasite-free snails by a reduced activity of parasite infected snails. Furthermore, in 2 out of 3 A. arbustorum populations and in experimentally infected snails winter survival was reduced in infected snails compared to uninfected snails.
In order to quantify the additive genetic variation in parasite load and winter mortality, every second snail of 15 lab bred snail families was experimentally infected with R. limacum. Parasite load of infected snails showed high heritable variation among snail families, suggesting additive genetic variation in parasite resistance in A. arbustorum. Furthermore, parasite load increased with increasing snail size within snail family, which suggests that the proliferation of R. limacum is limited by resources provided by A. arbustorum.
Furthermore, the transmission route of R. limacum was investigated. Parasite transmission also occurred without physical contact from mite-infected to parasite-free snails. The investigation of the off-host locomotion of R. limacum revealed that mites prefer to move on fresh mucus. Apart from the transmission during long-lasting courtship and mating of the host, R. limacum is also transmitted via soil and may use fresh snail mucus a cue to locate new host.
Further transmission experiments revealed that transmission of R. limacum occurs for the most part during host contacts. Using experimentally assessed transmission probabilities per host contact and contact frequencies of A. arbustorum, we developed mathematical models based on contact frequencies and transmission probabilities of A. arbustorum. Data on parasite-induced life-history responses were used to assess the basic reproductive ratio (R0; expected number of secondary infections originated by an infected individual introduced into a susceptible population) and host threshold density for parasite persistence in three A. arbustorum populations. The models revealed that the population with the highest density showed larger R0-values (16.7–22.95) compared to populations with intermediate (2.72–7.45) or low population density (0.75–4.10). Host threshold population density for parasite persistence ranged from 0.35 to 2.72 snails per m2. The thesis shows that the incorporation of the disease-relevant biology of organisms may improve models of host-parasite dynamics. This approach may help to predict the epidemiology of host-parasite systems.
|Committee Members:||Erhardt, Andreas|
|Faculties and Departments:||05 Faculty of Science > Departement Umweltwissenschaften > Institut für Natur- Landschafts- und Umweltschutz > Naturschutzbiologie (Baur)|
|Bibsysno:||Link to catalogue|
|Number of Pages:||84 S.|
|Last Modified:||30 Jun 2016 10:41|
|Deposited On:||07 May 2010 07:10|
Repository Staff Only: item control page