Year: 2015
Type: dissertation
Abstract: Parasite community dynamics is one of the central themes in contemporary parasitology. While between-host dynamics has been studied for a long time, within-host dynamics is less well studied. My aim was to identify which factors affect the parasite community during the lifetime of individual hosts by following longitudinally several individuals from a long-living species. Specifically, I was interested in how the dynamics of infra- and component communities differ from one another and which traits explain the variation in infracommunities. I studied rufous mouse lemur (Microcebus rufus), which is a primate living in the eastern montane rainforests of Madagascar. Mouse lemur is a well-suited study species as it can live for up to ten years in the wild. Due to its small size, the population density is high and trapping straightforward. Nematodes are the most common helminths found in mouse lemurs, but their identification is difficult. Typically, the nematodes are identified from adult specimens, but for longitudinal studies, this is not possible, as we cannot dissect the host individuals. In addition, morphological differences between species are small and we expected to encounter previously undescribed species. These difficulties led to the development of a new method, based on metabarcoding, to identify parasitic nematodes from fecal samples. The method I developed encompasses all steps from fieldwork to sequence analysis. Despite numerous confounding factors, the method managed to amplify and analyze half of the samples collected. Whilst there is room for further improvements, the main advantage is that the method works well for different host species, for example mouse lemurs and gastropods. In principle, this method works for all species of nematode, including free-living soil nematodes. Nevertheless, the resolution of identification do not allow for species-level identification. The variation in the parasite community inside individual hosts was extensive, but at the population level remained stable. Most of the parasites belonged to the putative species thought to be Strongyloides sp. The reason for this species success might be its lifecycle, the parasite can live in the intestine or as a free-living form in the soil. Due to the limited number of samples, the factors affecting the dynamics in individual mouse lemurs are difficult to analyze. It appears that sex and age do not have an effect on either parasite load or variation in parasite dynamics. Nevertheless, body condition appears to bear a consequence with the individuals in better condition having more parasite species in addition to higher fecal egg loads. The reason may be that those individuals are able to sustain larger populations of parasites, or that they are more tolerant to parasites. Hibernation could lead to the extinction of the nematode community, whereas higher precipitation appeared to lead to higher prevalences. This work gives insights into the dynamics of parasite communities both at the host individual and population level. It highlights the need for longitudinal studies as parasite community dynamics in host individual-level cannot be inferred from the host population-level The method I have developed can be used to perform more efficient and faster surveys of previously unknown parasite communities, though further development is necessary for better reliability.
Source: Työväentutkimus Vuosikirja
Author: Tuomas Aivelo
Language: Italian
Subfield: Parasitology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2178536977