Academic literature on the topic 'Free-living protozoa'

ABSTRACTThe introduction and survival of zoonotic bacterial pathogens in poultry farming have been linked to bacterial association with free-living protozoa. To date, however, no information is available on the persistence of protozoan communities in these environments across consecutive rearing cycles and how it is affected by farm- and habitat-specific characteristics and management strategies. We therefore investigated the spatial and temporal dynamics of free-living protozoa in three habitats (pipeline, water, and miscellaneous samples) in three commercial poultry houses across three rearing cycles by using the molecular fingerprinting technique denaturing gradient gel electrophoresis (DGGE). Our study provides strong evidence for the long-term (ca. 6-month) persistence of protozoa in broiler houses across consecutive rearing cycles. Various free-living protozoa (flagellates, ciliates, and amoebae), including known vectors of bacterial pathogens, were observed during the down periods in between rearing cycles. In addition, multivariate analysis and variation partitioning showed that the protozoan community structure in the broiler houses showed almost no change across rearing cycles and remained highly habitat and farm specific. Unlike in natural environments, protozoan communities inside broiler houses are therefore not seasonal. Our results imply that currently used biosecurity measures (cleaning and disinfection) applied during the down periods are not effective against many protozoans and therefore cannot prevent potential cross-contamination of bacterial pathogens via free-living protozoa between rearing cycles.

ABSTRACT Vibrio parahaemolyticus is a food-borne pathogen that naturally inhabits both marine and estuarine environments. Free-living protozoa exist in similar aquatic environments and function to control bacterial numbers by grazing on free-living bacteria. Protozoa also play an important role in the survival and spread of some pathogenic species of bacteria. We investigated the interaction between the protozoan Acanthamoeba castellanii and the bacterium Vibrio parahaemolyticus. We found that Acanthamoeba castellanii does not prey on Vibrio parahaemolyticus but instead secretes a factor that promotes the survival of Vibrio parahaemolyticus in coculture. These studies suggest that protozoa may provide a survival advantage to an extracellular pathogen in the environment.

ABSTRACT Free-living protozoan communities in water supplies may include hosts for Legionella pneumophila and other undesired bacteria, as well as pathogens. This study aimed at identifying free-living protozoa in two unchlorinated groundwater supplies, using cultivation-independent molecular approaches. For this purpose, samples (<20°C) of treated water, distributed water, and distribution system biofilms were collected from supply A, with a low concentration of natural organic matter (NOM) (<0.5 ppm of C), and from supply B, with a high NOM concentration (7.9 ppm of C). Eukaryotic communities were studied using terminal restriction fragment length polymorphism and clone library analyses of partial 18S rRNA gene fragments and a Hartmannella vermiformis-specific quantitative PCR (qPCR). In both supplies, highly diverse eukaryotic communities were observed, including free-living protozoa, fungi, and metazoa. Sequences of protozoa clustered with Amoebozoa (10 operational taxonomic units [OTUs]), Cercozoa (39 OTUs), Choanozoa (26 OTUs), Ciliophora (29 OTUs), Euglenozoa (13 OTUs), Myzozoa (5 OTUs), and Stramenopiles (5 OTUs). A large variety of protozoa were present in both supplies, but the estimated values for protozoan richness did not differ significantly. H. vermiformis was observed in both supplies but was not a predominant protozoan. One OTU with the highest similarity to Acanthamoeba polyphaga, an opportunistic human pathogen and a host for undesired bacteria, was observed in supply A. The high level of NOM in supply B corresponded with an elevated level of active biomass and with elevated concentrations of H. vermiformis in distributed water. Hence, the application of qPCR may be promising in elucidating the relationship between drinking water quality and the presence of specific protozoa.

ABSTRACT Despite stringent biosecurity measures, infections by bacterial food pathogens such as Campylobacter are a recurrent problem in industrial poultry houses. As the main transmission route remains unclear, persistence of these infections has been linked to bacterial survival and possibly multiplication within protozoan vectors. To date, however, virtually no information is available on the diversity and occurrence of free-living protozoa in these environments. Using a combination of microscopic analyses of enrichment cultures and molecular methods (denaturing gradient gel electrophoresis [DGGE]) on natural samples, we show that, despite strict hygiene management, free-living protozoa are common and widespread throughout a 6-week rearing period in both water and dry samples from commercial poultry houses. Protozoan communities were highly diverse (over 90 morphotaxa and 22 unique phylotypes from sequenced bands) and included several facultative pathogens and known bacterial vectors. Water samples were consistently more diverse than dry ones and harbored different communities, mainly dominated by flagellates. The morphology-based and molecular methods yielded markedly different results: amoebic and, to a lesser degree, ciliate diversity was seriously underestimated in the DGGE analyses, while some flagellate groups were not found in the microscopic analyses. Some recommendations for improving biosecurity measures in commercial poultry houses are suggested.

Acanthamoeba causes Granulomatous Amoebic Encephalitis (GAE) and Amoebic Keratitis (AK) in humans and in its cystic form is resistant to extreme environmental conditions. Both human pathogenic water-borne viruses and free-living protozoa share the same aquatic environment. This study set out to test the ability of both Acanthamoeba and Tetrahymena to internalise and protect enteric viruses; coxsackievirus (B3, B5), poliovirus (PV) and rotavirus (RV) following co-culture. Viral uptake was assessed by infection of cultured mammalian cells, by indirect immunofluorescence (IF), and by reverse transcriptase-polymerase chain reaction (RT-PCR). The results showed that none of the free suspended viruses were internalised in Acanthamoeba or Tetrahymena. However, both coxsackievirus B3N and rotavirus Wa could be detected within Acanthamoeba by IF and confirmed by RT-PCR when the amoebae were co-cultured (fed) with virally infected mammalian cells. The co-cultured amoeba was allowed to encyst but following this procedure no viruses were detected either by cell culture or RT-PCR. In a second series of experiments, the efficacy of solar disinfection (SODIS) against viruses either alone or when co-cultured with Acanthamoeba was assessed. SODIS reduced the viral infectivity by over 3log10 after 1 h for CVB3N and over 2log10 for PV after 2 h. Repeating these experiments in the presence of riboflavin, a 6log10 reduction was observed for CVB3N after 1 h of light exposure and 6log10 after 6 h for all other viruses tested. The results suggest that Acanthamoeba does not internalise or protect viruses in suspension. However, if a virus is located with an infected mammalian cell then it may be internalised; a new potential mechanism for virus dissemination in the environment. Secondly, solar disinfection is an effective treatment method for water contaminated with viruses which is further enhanced by the addition of riboflavin. This study provides a practical example of low technology methods which could be utilised to provide safe drinking water in various circumstances.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The vast hidric wealth of Brazil gets its watersheds more susceptible to impacts that compromise the water quality, affecting the ecosystem stability of aquatic environments. The decrease in the quality of water resources also results in a decrease of its multiple uses, especially in tourist areas of the coast, where the continuous flow of people to these sites increases even further the probability of inappropriate behavior of both tourists and local residents. Studies regarding the microbiological communities are still scarce, especially on the free-living protozoa that play unique roles in the food chain of aquatic ecosystems. Due to the large role played by this group of microorganisms in aquatic environments, the present study aimed at identifying the genus and species of free-living protozoa present in two sections of the Pium River, east coast of Rio Grande do Norte, making an association between the its occurrence and trophic conditions of the environment in which they are, also checking the bioindicator capacity of these organisms in water quality. It also aimed to conduct a survey with students to identify the main difficulties regarding the knowledge of free-living protozoa and hydric transmission diseases in two public schools near the river studied in the Pium district, county of Parnamirim. The survey was analyzed by means of questionnaires at both schools. Students identified several activities developed Pium river, highlighting its multifunctionality and importance to the region. A total of 76 taxa of free-living protozoa was recorded, of these, 33 were ciliates, 19 flagellates and 24 sarcodia. The spatial and temporal patterns of these organisms to both points studied revealed the bioindicator potentiality of some effective species identified. However, knowledge about the free-living protozoa proved quite lagged, presenting misconceptions that show them as pathogenic organisms exclusively, totally disregarding their ecological role. In order to remedy the flaws existing in students in relation to the functional role of protozoa, workshops were planned on these microorganisms while also addressing issues related to hydric transmission diseases through lectures, recreational activities and interactive presentations. These practical activities of Science Education had the goal of bringing students the context of local water resources, aiming to promote a greater clarification regarding of the functional role of free-living protozoa in aquatic environments
A vasta riqueza h?drica do Brasil deixa suas bacias hidrogr?ficas mais suscet?veis a impactos que comprometam a qualidade da ?gua, afetando a estabilidade ecossist?mica dos ambientes aqu?ticos. A diminui??o da qualidade dos recursos h?dricos resulta tamb?m na diminui??o dos seus usos m?ltiplos, principalmente em regi?es tur?sticas do litoral, onde o fluxo cont?nuo de pessoas a esses locais aumenta ainda mais a probabilidade de comportamentos inadequados tanto dos turistas quanto dos residentes locais. Os estudos a respeito das comunidades microbiol?gicas ainda s?o escassos, principalmente as de protozo?rios de vida livre, que desempenham fun??es singulares dentro da cadeia alimentar dos ecossistemas aqu?ticos. Devido ao grande papel desempenhado por este grupo de microrganismos nos ambientes aqu?ticos, o presente estudo teve por objetivo identificar os protozo?rios de vida livre, em g?nero e esp?cie, presentes em dois trechos do Rio Pium, litoral leste do Rio Grande do Norte, fazendo uma rela??o entre a ocorr?ncia e as condi??es tr?ficas do ambiente em que se encontram. Tamb?m se objetivou realizar uma sondagem junto aos alunos para identificar as principais dificuldades quanto ao conhecimento dos protozo?rios de vida livre e doen?as de veicula??o h?drica em duas escolas p?blicas pr?ximas ao rio estudado, no distrito de Pium, munic?pio de Parnamirim. A sondagem foi analisada por meio de question?rios aplicados em ambas as escolas. Foi registrado um total de 76 t?xons de protozo?rios de vida livre, destes, sendo 33 ciliados, 19 flagelados e 24 sarcod?neos. Os padr?es espaciais e temporais desses organismos nos dois pontos estudados revelaram a potencialidade bioindicadora eficaz de algumas esp?cies identificadas. Os alunos identificaram diversas atividades desenvolvidas no Rio Pium, destacando sua multifuncionalidade e import?ncia para a regi?o. Por?m, o conhecimento sobre os protozo?rios de vida livre mostrou-se bastante defasado, apresentando concep??es alternativas que os evidenciam como organismos exclusivamente patog?nicos, desconsiderando totalmente seu papel ecol?gico primordial. Com o prop?sito de minimizar os poss?veis equ?vocos existentes nos alunos em rela??o ao papel funcional dos protozo?rios, foram planejadas oficinas did?ticas sobre estes microrganismos, abordando tamb?m temas relacionados a doen?as de veicula??o h?drica por meio de palestras, atividades l?dicas e apresenta??es interativas. Estas atividades pr?ticas de Educa??o em Ci?ncias tiveram o intuito de aproximar os alunos do contexto dos recursos h?dricos locais, almejando-se promover um maior esclarecimento sobre o papel funcional dos protozo?rios de vida livre nos ambientes aqu?ticos

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Water is considered an essential right to life, besides being a determinant of economic development and social welfare, represented by both the quantity available, and the quality. In semi-arid Northeast, droughts occurring on a regular basis combined with human activities, aggravate the situation regarding the conservation of water resources in this area. To alleviate this condition is common to construction of artificial reservoirs, such as reservoirs and dams. As in natural aquatic environments, these reservoirs are potential sites for the proliferation, growth and development of diverse biological communities, whether of animals, plants and microorganisms. Research on the composition and ecology of these communities, especially microbial, are still restricted. One of the least studied groups in these environments are free-living protozoa, which over time have been neglected and after discoveries about its various functions in the aquatic ecosystem are beginning to receive more attention from scholars. They are, in quantitative terms, the most important consumers of microorganisms (mainly bacteria and algae) in aquatic environments, and therefore control the abundance of these. They may therefore influence the structure of the aquatic food chain in terms of species composition, abundance, biomass and biodiversity. Despite the recognition of the importance of protozoa in the final of the trophic transfer in aquatic environments, there are few data and, in general, are still precarious knowledge of them. Given the importance of protozoa in aquatic environments and the paucity of research on this group, especially in the state of Rio Grande do Norte, the present study aimed at identifying the genus and species of free-living protozoa that are present in the Armando Ribeiro Gon?alves Dam as well as to relate the occurrence and dynamics of the trophic conditions in the environment in which they are inserted, in order to support the hypothesis that species that are in these environments can serve to indicate the water quality. We observed the presence of 65 taxa of free-living protozoa, of which 29 were identified at the species level. There was a similarity space in taxonomic composition of protozoa, suggesting a possible regulation of this type of community for limnological variables other than those studied in this work (chlorophyll a, pH, temperature). Although it was aimed to analyze the conceptions of teachers and students from nearby towns Dam Armando Ribeiro Gon?alves, on issues relating to water quality and the role of protozoa. For this, we applied questionnaires with teachers and pupils of public schools of San Rafael and Itaj?. It was concluded that teachers and students recognize the multi-dam Armando Ribeiro Gon?alves, although unaware of important aspects of the dynamics and ecology of this environment. Conceptions of teachers and students are matched at various times, especially with regard to waterborne diseases. In an attempt to identify possible misconceptions about the knowledge of the protozoa, assuming that these organisms have neglected their ecological role, and are seen as only, disease, a study was done with teachers and students, following a particular methodology that allowed look so clear and precise results. It was clear that knowledge about the free-living protozoa is still quite limited. The alternative conceptions that were found show a direct relation of protozoans and diseases. From the data obtained by these studies, we planned a series of science communication activities, environmental education and health education in schools close to study environments in order to promote a didactic transposition of accumulated knowledge about these organisms, favoring continuing education of teachers and the increase of information to the local community through the knowledge of biodiversity and ecology of these organisms. Moreover, the results found in this study and reflections on it that led to propose the elaboration of a book Readers with an emphasis on the group of freeliving protozoa in the populations for use in public schools in the region where it was developed the semiarid work
A ?gua ? considerada um bem imprescind?vel ? vida, al?m de ser um fator condicionante do desenvolvimento econ?mico e do bem-estar social, representado tanto pela quantidade dispon?vel, como pela qualidade. No semi?rido nordestino, as secas que ocorrem de forma peri?dica aliada a atividades antr?picas, agravam a situa??o da conserva??o dos recursos h?dricos nessa localidade. Para amenizar essa condi??o ? comum a constru??o de reservat?rios artificiais, como a?udes e barragens. Assim como nos ambientes aqu?ticos naturais, estes reservat?rios s?o locais prop?cios para a prolifera??o, crescimento e desenvolvimento de diversas comunidades biol?gicas, seja de animais, vegetais e de microrganismos. As pesquisas sobre a composi??o e ecologia dessas comunidades, sobretudo as microbianas, ainda s?o restritas. Um dos grupos menos estudados nesses ambientes s?o os protozo?rios de vida livre, que ao longo do tempo foram negligenciados e depois de descobertas sobre suas variadas fun??es no ecossistema aqu?tico come?am a receber mais aten??o por parte dos estudiosos. Eles s?o, em termos quantitativos, os mais importantes consumidores de microrganismos (principalmente algas e bact?rias) nos ambientes aqu?ticos, e, por isso controlam a abund?ncia destes. Eles influenciam, portanto, a estrutura da cadeia alimentar aqu?tica em termos de composi??o de esp?cies, abund?ncia, biomassa e biodiversidade. Apesar do reconhecimento da import?ncia dos protozo?rios no balan?o final das transfer?ncias tr?ficas em ambientes aqu?ticos, existem poucos dados e, de um modo geral, s?o, ainda, prec?rios os conhecimentos sobre eles. Tendo em vista a import?ncia dos protozo?rios em ambientes aqu?ticos e a escassez de pesquisas relacionadas a este grupo, sobretudo no Estado do Rio Grande do Norte, o presente estudo teve - como objetivo identificar os g?neros e esp?cies de protozo?rios de vida livre que est?o presentes na Barragem Armando Ribeiro Gon?alves, bem como relacionar a ocorr?ncia e a din?mica destes com as condi??es tr?ficas do ambiente no qual est?o inseridos, com o intuito de corroborar a hip?tese de que as esp?cies que est?o nesses ambientes podem servir para indicar a qualidade da ?gua. Registrou-se a presen?a de 65 t?xons de protozo?rios de vida livre, dos quais 29 foram identificados em n?vel de esp?cie. Observou-se uma similaridade espacial na composi??o taxon?mica dos protozo?rios, sugerindo-se uma poss?vel regula??o desse tipo de comunidade por outras vari?veis limnol?gicas diferentes daquelas estudadas nesse trabalho (clorofila-a, pH, temperatura). Ainda objetivou-se analisar as concep??es de professores e alunos, das cidades pr?ximas da Barragem Armando Ribeiro Gon?alves, sobre as tem?ticas relativas ? qualidade de ?gua e do papel dos protozo?rios. Para isso, foi aplicado question?rios com professores e alunos de escolas estaduais de S?o Rafael e Itaj?. Concluiu-se que os professores e alunos reconhecem as m?ltiplas funcionalidades da Barragem Armando Ribeiro Gon?alves, apesar de desconhecerem aspectos importantes da din?mica e ecologia desse ambiente. As concep??es de professores e alunos se igualaram em v?rios momentos, principalmente no tocante ?s doen?as de veicula??o h?drica. Na tentativa de identificar poss?veis concep??es alternativas sobre o conhecimento dos protozo?rios, partindo da hip?tese que esses organismos t?m seu papel ecol?gico negligenciado, e s?o vistos como, somente, transmissores de doen?as, foi feito um estudo com professores e alunos, seguindo determinada metodologia que permitiu analisar de forma clara e precisa os resultados. Ficou claro que o conhecimento sobre os protozo?rios de vida livre ?, ainda, bastante limitado. As concep??es alternativas que foram evidenciadas mostram uma rela??o direta de protozo?rios e doen?as. A partir dos dados obtidos por todos esses estudos, planejou-se uma s?rie de atividades de divulga??o cient?fica, educa??o ambiental e educa??o em sa?de nas escolas pr?ximas aos ambientes de estudo com o intuito de promover uma transposi??o did?tica do conhecimento acumulado sobre esses organismos, favorecendo a forma??o continuada de professores e o incremento de informa??es ? comunidade local por meio do conhecimento da biodiversidade e ecologia desses organismos. Al?m disso, os resultados encontrados neste estudo e as reflex?es feitas sobre ele levaram a que se propusesse a elabora??o de um livro paradid?tico com ?nfase sobre o grupo dos protozo?rios de vida livre para uso junto ?s popula??es de escolas p?blicas da regi?o semi?rida onde foi desenvolvido o trabalho

A parasite is an organism that lives on or in a host and gets its food from or at the expense of its host. Worms or helminths either live as parasites or free of a host in aquatic and terrestrial environments. Parasites and worms are found worldwide but mainly in the tropics. It is estimated that 20% of immigrants from endemic countries may have helminthic infections at their arrival to the UK. These people could be asymptomatic, but tend to present with unexplained symptoms, especially gastrointestinal in nature or eosinophilia. Travellers to endemic countries tend to be newly infected and have greater immune response and pronounced eosinophilia in some but not all parasitic infections. Parasites that can cause disease in humans fall under three classes: protozoa, helminths, and Ectoparasites Protozoa are microscopic, one- celled organisms that can be free living or parasitic in nature. Transmission of protozoa that live in a human’s intestine to another human typically occurs through a faeco-oral route (for example, contaminated food or water, or person- to-person contact). Protozoa that live in the blood or tissue of humans are transmitted to other humans by an arthropod vector (for example, through the bite of a mosquito or sand fly). Helminths are large, multicellular organisms that are generally visible to the naked eye in their adult stages. Like protozoa, helminths can be either free living or parasitic. There are three main groups of helminths that parasitize humans: cestodes, trematodes, and nematodes. These are flat worms that comprise Echinococcus species: intestinal tapeworms and neurocysticercosis (Taenia solium) These are leaf- shaped, and they vary in length from a few millimetres to 8 cm. They include: ■ Liver fluke: Clonorchis sinensis, Fasciola hepatica ■ Intestinal fluke: Fasciola buski, Heterophyes heterophyes, ■ Lung fluke: Paragonimus westernmani ■ Blood flukes: Schistosoma species These are cylindrical in structure. Blood- sucking arthropods such as mosquitoes are considered as ectoparasites because they depend on blood meal for their survival. Narrowly speaking, ectoparasites include organisms like ticks, fleas, lice, and mites (scabies) that attach or burrow into the skin and remain there for relatively long periods of time (e.g. weeks to months).

Parasites are more numerous than non-parasitic species and have evolved in virtually all groups of organisms, such as viruses, prokaryotes (bacteria), protozoa, fungi, nematodes, flatworms, acantocephalans, annelids, crustaceans, and arthropods (crustacea, mites, ticks, insects). These groups have adapted to the parasitic lifestyle in very many ways. Evolution towards parasitism has also followed different routes. Initial steps such as phoresy, followed by later consumption of the transport host, are plausible evolutionary routes. Alternatively, formerly free-living forms have become commensals before evolving parasitism. Complex life cycles with several hosts evolved by scenarios such as upward (adding a new host upwards in the food chain), downward, or lateral incorporation, driven by the advantage of extending growth phases within hosts and increasing fecundity. Examples are digenea; other parasites have added vectors to their life cycle.