| dc.description.abstract | It is known that tropical regions of the globe are those that concentrate the greatest
biodiversity on the planet, which includes trematodes, parasites with complex life cycles,
involving a wide range of intermediate and definitive hosts. Despite the medical,
veterinary, and ecosystem importance of these parasites, there is still a large gap in
knowledge about their interactions with their hosts and the environment, especially in
Brazil. In order to contribute to the knowledge of the taxonomy and biology of trematodes
found in Brazil, malacological surveys, experimental studies, and the evaluation of some
domestic and wild vertebrate were carried out at a lake located at Minas Gerais State
Administrative Center, in the State of Minas Gerais, Belo Horizonte, MG, Brazil, between
January 2017 and May 2019. The taxonomic identification of the trematodes, at the lowest
taxonomic levels possible, was based on morphological and/or molecular analyzes
[ribosomal (28S and ITS) and mitochondrial (Cox-1 and Nad-1) markers]. In the
malacological survey, 9.508 gastropods belonging to five species (Melanoides
tuberculata, Biomphalaria straminea, Pomacea sp., Physa acuta, and Pseudosuccinea
columella) were collected, of which the first three were found infected with larval
trematodes. Among the vertebrates studied, three species of domestic Anseriformes
[ducks, Cairina moschata domestica (N= 47), mallards, Anas platyrhynchos domesticus
(N= 8), and geese, Anser cygnoides domesticus (N= 6)] occurring at the locality were
evaluated in vivo through direct ophthalmic examination and coproparasitological
analysis. In addition, wild animals found death at the locality [waterfowl, Gallinula
galeata (N=1), capybara, Hydrochoerus hydrochaeris (N=2) and six species of fish,
“acará”, Australoheros sp. (N = 38), trahira, Hoplias malabaricus (N = 5), guppies,
Poecilia reticulata (N = 9) and tilapia fry, Oreochromis niloticus (N = 6)], were
necropsied for helminth research. Among the parasites found, seven species [Cotylurus
sp., Crassiphialinae gen. sp., Drepanocephalus sp., Hysteromorpha sp., Diplostomidae
gen. sp., Spirorchiidae gen. sp. in B. straminea, and Renicola sp. in M. tuberculata] were
identified only in mollusks. Experimental infection performed with cercariae of the
Megalurous type found in M. tuberculata made it possible to recover, in Gallus gallus
domesticus, eye worms identified as Philophthalmus gralli, and studies aiming to
standardize the diagnostic and treatment techniques were performed. The experimental
approach carried out from cercariae of the Amphistome type emerged from B. straminea
made it possible to obtain, in Mus musculus, adult parasites identified as Zygocotyle
lunata. Phylogenetic studies carried out for the first time with this species confirmed the
inclusion of the species in the family Zygocotylidae as well as its wide distribution in the
American continent. In fish, metacercariae of Apharyngostrigea sp. and Centrocestus
formosanus were recovered from P. reticulata, with cercariae of the latter also identified
in M. tuberculata. Metacercariae of Clinostomum sp. were obtained from Australoheros
sp. and the morphological and molecular data revealed to be dealing with a species
distinct from others reported in the American continent. In H. malabaricus, metacercariae
of Tylodelphys sp. were recovered, a species that in the phylogenetic study grouped with
other American isolates of the genus, but proved to be a distinct species. Among the birds
evaluated, four species, P. gralli, Typhlocoelum cucumerinum, Z. lunata and an
unidentified species, were found in domestic anseriformes. Of these, P. gralli and T.
cucumerinum were molecularly associated with larval forms obtained from M.
tuberculata and B. straminea, respectively, resulting in new information on the epizooty
of these avian diseases in an urban center. In the specimen of G. galeata, in addition to
P. gralli, Cyclocoelum mutabile, and Echinostoma sp. Molecular data confirmed the wide
distribution of C. mutabile, a species found in the Americas and Europe, and revealed that
Echinostoma sp., not identified at a specific level due to the loss of collar spines belongs
to the revolutum group. In H. hydrochaeris, it was identified Fasciola hepatica, Taxorchis
sp. and Hippocrepis hippocrepis. The finding of F. hepatica in this urban center points to
the risk of transmission of this anthropozoonotic agent. Although Taxorchis sp. could not
be identified at specific level due the lack of fully developed specimens, the molecular
data obtained represent the first sequences and phylogenetic analysis involving
mammalian cladorchiids. As for H. hippocrepis, the molecular approach enabled to link
this parasite and the cercaria of the Monostome type frequently recovered from B.
straminea, besides to evaluate its phylogenetic position in relation to other members of
the superfamily Notocotyloidea. With the use of an integrative taxonomic approach in the
study of trematodes in this lake, it was possible to identify 21 species. The elucidation of
aspects of the life cycle of some of these and several of the observed biological
interactions are recorded for the first time in the country. | |
