Visualising blood flagellates infections in transparent zebrafish

Trypanosomes of the Trypanosoma genus are blood flagellates, and important causative agents of diseases of humans, livestock and cold-blooded species. Numerous in vitro studies and infection studies in mice contributed enormously to the insights into the biology of trypanosomes, their interaction with and evasion of the host immune system, as well as into various aspects related to vaccine failure and (uncontrolled) inflammation. A tight regulation of the early innate immune response to trypanosome infections was shown to be critical to obtain a balance between parasite control and inflammation-associated pathology. Trypanosome morphology was observed to be essential for their motility, the adaptation to their host’s environment and pathogenesis. One of the best-studied non-mammalian trypanosomes is Trypanosoma carassii, which presents many morphological similarities to mammalian trypanosomes. T. carassii is regularly observed co-infecting fish with Trypanoplasma spp such as T. borreli. Currently, few or no in vitro studies have been performed to unravel the swimming behaviour and host-pathogen interaction of Trypanoplasma species. For both trypanosomes and trypanoplasma, in vivo studies to visualise the parasite motility and host immune response have not been reported so far.     In this thesis we describe for the first time blood flagellate infections in vivo in the natural environment of a vertebrate host (zebrafish). We did this by studying the parasite motility in vitro and in vivo and the kinetics of innate immune responses in vivo. The T. carassii and T. borreli zebrafish infection models are promising complementary models to existing (mammalian) animal models, and can contribute to fundamental mechanistic insights into host-parasite interactions

Visualizing trypanosomes in a vertebrate host reveals novel swimming behaviours, adaptations and attachment mechanisms.

Trypanosomes are important disease agents of humans, livestock and cold-blooded species, including fish. The cellular morphology of trypanosomes is central to their motility, adaptation to the host's environments and pathogenesis. However, visualizing the behaviour of trypanosomes resident in a live vertebrate host has remained unexplored. In this study, we describe an infection model of zebrafish (Danio rerio) with Trypanosoma carassii. By combining high spatio-temporal resolution microscopy with the transparency of live zebrafish, we describe in detail the swimming behaviour of trypanosomes in blood and tissues of a vertebrate host. Besides the conventional tumbling and directional swimming, T. carassii can change direction through a 'whip-like' motion or by swimming backward. Further, the posterior end can act as an anchoring site in vivo. To our knowledge, this is the first report of a vertebrate infection model that allows detailed imaging of trypanosome swimming behaviour in vivo in a natural host environment

Visualizing trypanosomes in a vertebrate host reveals novel swimming behaviours, adaptations and attachment mechanisms.

Trypanosomes are important disease agents of humans, livestock and cold-blooded species, including fish. The cellular morphology of trypanosomes is central to their motility, adaptation to the host's environments and pathogenesis. However, visualizing the behaviour of trypanosomes resident in a live vertebrate host has remained unexplored. In this study, we describe an infection model of zebrafish (Danio rerio) with Trypanosoma carassii. By combining high spatio-temporal resolution microscopy with the transparency of live zebrafish, we describe in detail the swimming behaviour of trypanosomes in blood and tissues of a vertebrate host. Besides the conventional tumbling and directional swimming, T. carassii can change direction through a 'whip-like' motion or by swimming backward. Further, the posterior end can act as an anchoring site in vivo. To our knowledge, this is the first report of a vertebrate infection model that allows detailed imaging of trypanosome swimming behaviour in vivo in a natural host environment

Contribution to the discussions on the origin of the cerrado biome: Brazilian savanna

Theories that attempt to explain the origin of the cerrado biome are mostly based on the isolated action of three major factors: climate, fire and soil. Another factor that has been mentioned is that of human interference. We hypothesise that the evolutionary origin of this biome resulted from the complex interaction of climate, fire and soil, with climate being the triggering agent of this assumed interaction. Fire, as well as acid and dystrophic soils, would be factors involved in the selection of savanna species throughout climatic events, during the Tertiary and the Quaternary, e.g. Pliocene and Pleistocene. The genesis of the physiognomies that would give rise to cerrado sensu lato, rather than forest formations, could have occurred due to the strong pressure exerted by the reduction in water availability, and the selection of the species adapted to the new conditions imposed by the environment. The characteristics of cerrado sensu lato soil, originated from edaphic impoverishment caused by lixiviation and successive past fires, would remain, even after hydric availability increased following the Pleistocene glaciations