Dissertação
Diversidade genética e estrutura populacional de Fasciola hepatica (Linnaeus, 1758): o papel dos hospedeiros definitivos
Fecha
2020-02-21Autor
Schwantes, Jéssyca Bressan
Institución
Resumen
Fasciola hepatica is a flatworm of the Trematoda Class, and is responsible for the
disease called fasciolosis. This parasite is cosmopolitan and has heteroxenic cycle
being dependent on two hosts to complete its life cycle: an mollusc of the Lymnaeidae
family as intermediate host; and domestic (cattle, sheep, goats) or wild vertebrates as
definitive hosts. In the American continent, Fasciola hepatica was introduced together
with domestic animals at the beginning of European colonization, and since then, it
was reported at least 14 South America native species to being infected, one of them
is the capybara (Hydrochoerus hydrochaeris), which due to its semi-aquatic life habits
has become an important reservoir of the parasite. This work aims to genetically
characterize different populations of Fasciola hepatica in Brazil in different hosts
(bovine and capybara). For that, adult parasites and feces from infected animals were
collected for egg isolation in the states of Rio Grande do Sul and Paraná, and we used
two fragments of the mitochondrial genes COI and NAD1 for genetic analysis.
Nucleotide and haplotype diversity and number of haplotypes were evaluated. The
haplotype relationship and the frequency of the haplotypes were calculated and
haplotype networks were built by Median-joining. We performed the AMOVA test and
calculated the fixation index (FST) to evaluate population structure. The genetic
distance between parasites encountered on different hosts was calculated within each
sampled host group and between host groups. Our results showed that the genetic
structure of Fasciola hepatica, whether from domestic or wild animals, depends more
on geographic aspects on than the host in question, in a way that the parasites of wild
animals share the same gene pool as those from domestic animals from the same
region. However, the high transit of domestic animals within the and the border control
between Brazilian states lead to genetic homogeneity among populations within states
and genetic structure between states. In the same way, when comparing the different
hosts, wild animals from South America share the same population of parasites among
them, and have parasites more genetically distant from those encountered in wild
animals from the Old World. Therefore, the implementation of management plans on
domestic and wild hosts must be carried out for the epidemiological control of Fasciola
hepatica within the states of Rio Grande do Sul and Paraná, as well as the control of
intermediate hosts, especially in the regions highly susceptive to the disease and with
high potential to new definitive hosts.