Harmful algal blooms (HABs) are becoming more prevalent throughout the world’s aquatic systems. These blooms have been the subjects of numerous studies because they can cause human health issues and economic impact through fish kills, contaminated shellfish and decreased tourism. Much research has focused on the “bottom-up” aspect of these blooms; namely, the potential role of increased nutrient input into coastal waters from anthropogenic sources causing increased growth in harmful algal species. However, there are also potential “top-down” controls affecting the rate at which harmful algal species are consumed by grazers. The aim of this project was to determine protozoan grazer population fluctuations and their grazing impact on HAB species through field monitoring and laboratory grazing experiments. Protozoan grazers were chosen because their growth rates could potentially keep up with those of HAB species. Declines in grazer populations before the onset of a bloom could be indicative of a release of the HAB from a “top-down” grazing control. Field samples taken during bloom and non-bloom events helped elucidate any microplankton community changes. After establishing that there appear to be changes to the grazer population before and after a bloom, ingestion experiments including direct epifluorescence microscopy and DNA analyses were conducted to determine if it is possible that a chosen protozoan grazer can ingest a HAB species. Finally, experiments were conducted to determine whether the HAB species was a favorable food source for the grazer. Population growth experiments in which grazers are fed a HAB species, 50:50 mixture, or normal culture food source were used to determine the survival and growth rate of the grazer. Although certain ciliates and heterotrophic dinoflagellates were found to feed on HAB species in the lab and in natural bloom samples, the HAB species as a food source produces lower grazer growth rates than on control food. Protozoan grazers may be a more effective control during bloom initiation than after the bloom has been established. / text

In this study, we determined the immunogenicity of CWP2 and its potential as a vaccine candidate against giardiasis. CWP2 was expressed as a recombinant protein with an hexa-histidine affinity tag and was isolated from inclusion bodies. When BALB/c mice were immunized with CWP2, a specific IgA was detected in the feces. When mice were immunized with CWP2 + cholera toxin, as an adjuvant, IgA in the feces, and IgA, IgG1, and IgG2a in the serum, all specific to CWP2, were detected. Also, CD-1 mice were infected with G. muris and presence of specific IgA antibodies to CWP2 were detected in the feces. This result indicated that CWP2 was recognized by the immune system in a natural infection. IL-4 and IL-5 were released from Peyer's patches (PP) and mesenteric lymph nodes (MLN) cells when stimulated with concanavalin A. In spleen cells, IFN-gamma, IL-4, and IL-5 were released when stimulated with concanavalin A. However, in PP, MLN and spleen cells, the levels of cytokines were barely detectable when stimulated with CWP2. The presence of IgG2a (Th1), IgA and IgG1 (Th2) as the production of IFN-gamma (Th1), IL-4 and IL-5 (Th2) confirmed that CWP2, when presented orally to mice, stimulates both a Th1 and Th2 type immune response, locally and systemically.

Thesis (Ph.D.)--Murdoch University, 2002. / Thesis submitted to the Division of Veterinary and Biomedical Sciences. Bibliography: leaves 237-283.

M.Sc. / In this research project, a variety of sites and ecosystems were studied. These ranged from tropical coral reefs (north-eastern Coast of Australia), to warm temperate intertidal pools (South Coast of South Africa, SA) and sub-tropical estuaries (East Coast of SA). The overall aims of the thesis were to examine the haematophagous gnathiid ectoparasites and blood protozoans of some host teleosts found in these systems, and to some extent to investigate the role gnathiids might play as vectors of the protozoans. Gnathiid research in Australia on the Great Barrier Reef (GBR) focuses mainly on gnathiid ecology and not taxonomy. This is not the case in SA, where gnathiid taxonomy is researched more regularly and gnathiid ecology has received little attention. In this thesis, two new gnathiid species, Gnathia aureamaculosa and Gnathia sp. B, were described from a number of teleost fishes of the GBR and several morphological features, including live colouration patterns, were highlighted as useful in future gnathiid identification and discrimination. The feeding ecology of Gnathia africana from SA was also examined and this feeding study was based on similar work done on coral reef gnathiids in Australia. Gnathiids of the GBR are mainly nocturnal due to cleaner fish predation during the day, whereas G. africana was found to have a preference for dawn/early morning/midday feeding on an intertidal teleost, Clinus superciliosus. Gnathia africana‟s behaviour/feeding patterns, especially of its different juvenile stages, are therefore determined by time of day, and likely by locality and predation by other organisms, such as fishes, though probably not by cleaner fish. Gnathiid feeding behaviours/patterns are thus, it seems, determined by environmental and biological factors, and these vary according to the type of ecosystem studied. Several gnathiids and fish blood protozoan species are known from the South Coast of SA, but the East Coast has remained largely unexplored. Sampling along the East Coast yielded the first records of haemogregarines from the blood of fishes in this region, in particular new hosts and locality records probably for both probable Haemogregarina bigemina and a Haemogregarina quadrigemina – like haemogregarine. However, both haemogregarines displayed unusual features compared with the original species descriptions, in size, development patterns, or effect on host cells. Limited data suggested that juveniles of Gnathia pilosus were possible haematophagous vectors of these haemogregarines, but further studies are required to confirm this.

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 4 uppsatser.

Thesis (M.S.)--University of Florida, 2004. / Typescript. Title from title page of source document. Document formatted into pages; contains 79 pages. Includes Vita. Includes bibliographical references.

Protozoan infections such as Malaria, Leishmaniasis, Toxoplasmosis, Chaga’s disease and African trypanosomiasis caused by the Plasmodium, Leishmania, Toxoplasma and Trypanosoma genuses respectively; inflict a huge economic, health and social impact in endemic regions particularly tropical and sub-tropical regions. The combined infections are estimated at over a billion annually and approximately 1.1 million deaths annually. The global burden of the protozoan infections is worsened by the increased drug resistance, toxicity and the relatively high cost of treatment and prophylaxis. Therefore there has been a high demand for new drugs and drug targets that play a role in parasite virulence. Cysteine proteases have been validated as viable drug targets due to their role in the infectivity stage of the parasites within the human host. There is a variety of cysteine proteases hence they are subdivided into families and in this study we focus on the clan CA, papain family C1 proteases. The current inhibitors for the protozoan cysteine proteases lack selectivity and specificity which contributes to drug toxicity. Therefore there is a need to identify the differences and similarities between the host, vector and protozoan proteases. This study uses a variety of bioinformatics tools to assess these differences and similarities. The Plasmodium cysteine protease FP-2 is the most characterized protease hence it was used as a reference to all the other proteases and its homologs were retrieved, aligned and the evolutionary relationships established. The homologs were also analysed for common motifs and the physicochemical properties determined which were validated using the Kruskal-Wallis test. These analyses revealed that the host and vector cathepsins share similar properties while the parasite cathepsins differ. At sub-site level sub-site 2 showed greater variations suggesting diverse ligand specificity within the proteases, a revelation that is vital in the design of antiprotozoan inhibitors.

Orientador: João Aristeu da Rosa / Banca: Vera Lucy de Santi Alvarenga / Banca: Vera Lucia Pagliusi Castilho / Resumo: Blastocystis hominis é protozoário causador da infecção intestinal denominada blastocistose humana, cujo diagnóstico é realizado pelo exame coproparasitológico e por meio de técnicas de colorações permanentes que foram utilizadas neste estudo para avaliar a prevalência de Blastocystis hominis nos espécimes fecais de habitantes na região de Araraquara-SP. Foram estudadas 503 amostras de fezes submetidas às técnicas de exame direto a fresco, de Faust e cols., de Lutz e de Rugai, Mattos e Brisola, além das colorações pela hematoxilina férrica, tricrômio e de Kinyoun modificada. Do total das amostras analisadas 174 (34,6%) apresentaram-se positivas para a presença de parasitas intestinais. O protozoário e helminto mais freqüentes foram respectivamente: Entamoeba coli (14,6%) e Strongyloides stercoralis (6,7%). Blastocystis hominis foi observado em 23 (4,6%) amostras fecais com consistência predominantemente pastosa, não caracterizando quadro diarréico. Apesar da baixa prevalência de Blastocystis hominis encontrada na região de Araraquara, comparativamente a outras regiões brasileiras, é importante a realização do diagnóstico laboratorial desse protozoário. O encontro de Blastocystis hominis em material fecal é indicativo de contaminação de alimentos e água de consumo, desde que se admita a rota de transmissão oral-fecal deste parasita, o que implica na orientação da população sobre as medidas de saneamento básico e higiene como meio para se controlar problemas de saúde ocasionados pelos enteroparasitas. / Abstract: Blastocystis hominis is a protozoan which causes an intestinal infection called human blasticistosis. Its diganosis is perfomed by stool examination and permanent staining techniques. Such methodologies were carried out on the present study in order to evaluate the prevalence of Blastocystis hominis in faecal specimens from the Araraquara region inhabitants. A total of 503 faecal samples were evaluated by the following techniques: examination fo fresh specimens, Lutz, Faust et al. and Rugai et al. besides the iron hemotoxylin, trichrome and modified Kinyon staining. Out of 503 stool samples examined 174 (34,6) were found to be positive for intestinal parasites. The most prevalent protozoan and helminth parasites were Entamoeba coli (14,6%) and Strongyloides stercoralis (6,7%) respectively. Balstocystis hominis was present in 23 (4,6%) stool samples, most of all of soft consistence and without diarrheic reports. Blastocystis hominis laboratorial diagnosis is important althought its prevalence has been low in Araraquara region. Blastocystis hominis findings is faecal specimens indicates the food and water contamination and since the transmission of this parasite is iral-faecal it implies that the population needs orientation about hygiene and basic sanitation conditions in order to control health problems caused by enteroparasites. / Mestre