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Query: UMLS:C0017536 (giardiasis)
 1,714 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The accurate identification of a parasite at the species and/or genotype level has major implications for various aspects of human and veterinary parasitology, including the diagnosis, the taxonomy, the treatment and the control. The advent of molecular techniques, in particular those based on the in vitro amplification of nucleic acids, has dramatically improved our ability to detect infections caused by parasites. To illustrate the progress in molecular diagnostics, Cryptosporidium and Giardia are used here as examples of parasites for which both the diagnosis and the taxonomy have traditionally been problematic. These protozoan parasites, while very different for many aspects of their biology, shares a complex series of transmission routes, including anthroponotic and zoonotic transmission, as well as waterborne and foodborne transmission. The resistant stages produced by Cryptosporidium and Giardia (oocysts and cysts, respectively) are remarkably stable, and can survive for weeks to months in the environment. Further, the infective dose is low, and infectious dose studies and models suggest that even a single oocyst or cyst carries some probability of causing an infection. Finally, most faeces that contain (oo)cysts end up in the environment and can be spread to foods by irrigation or by direct contact, and can persist in the water, as routine treatments eliminate only a fraction of these stages. This situation explains the growing interest towards the development of methods that allows such stages to be detected with the highest sensitivity and specificity. A variety of Polymerase Chain Reaction (PCR) assays have been described for both Cryptosporidium and Giardia. The choice of a particular assay mainly depends on the amount of information carried by the genetic locus under analysis. Indeed, some assays can be used to identify the different species within a genus, while others allowed to distinguish between isolates of the same species (genotypes), and some can even be used for both purposes. Post-PCR analyses are usually based on the direct sequencing of the amplification products, or on the digestion with endonucleases followed by gel electrophoresis of the restriction fragments. In the last few years, the molecular characterization of a large number of isolates, collected from infected hosts and from the environment, has considerably changed our view of the epidemiology of cryptosporidiosis and giardiasis. Indeed, several species/genotypes have been established as human pathogens, and the nature of the parasites present in the water and in food have been investigated, allowing a better understanding of the complex circulation of the parasites in the environment, that may eventually led to implemented control measures. Finally, phylogenetic analysis of several nuclear genes is having a major impact in the revision of the taxonomy of Cryptosporidium and Giardia. The main limitation of PCR is that it doesn't provide information on the viability and infectivity of the pathogen. To obtain additional information on these important aspects, indirect methods, such as inclusion/exclusion assays using vital dyes or the Reverse-Transcriptase PCR (RT-PCR), can be used. Since RT-PCR relies on the integrity of mRNA, which usually has very short half-life (seconds), its use is thought to provide a more closely correlated indication of viability status compared to DNA-based methods. RT-PCR assays usually target the heat shock protein (hsp) 70 gene. The rationale behind this choice is that hsps are known to be synthesized with a high level of efficiency in stressed organisms; therefore, when (oo)cysts are exposed to a thermal shock, the induction of heat shock response provides both a level of amplification to increase detection sensitivity and an index of viability. Moreover, with the recent introduction of real-time PCR, that allows the continuous monitoring of amplicon formation throughout the reaction, quantitative aspect of the infection could be studied with exquisite sensitivity. This will, for example, allow (1) to detect carrier states, (2) to determine the number of oocysts/cysts present in a sample, (3) to study quantitative aspects of gene expression during the various phases of the infection.
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PMID:[New methods for the diagnosis of Cryptosporidium and Giardia]. 1530 6

Giardia duodenalis is a waterborne protozoan parasite that causes the diarrhoeal disease, giardiasis. Its durable and thick cell wall allows the parasite to exhibit resistance to environmental stresses. Because G. duodenalis exists in a water system at low levels, it is necessary to develop a sensitive method to detect its viability in aquatic environments. In the present study, specific primers for the heat shock protein (hsp) 70 gene were designed on the basis of G. duodenalis genome sequence and bioinformatic analysis. Viable G. duodenalis cysts were successfully distinguished by reverse transcription-PCR (RT-PCR) analysis using these primers. The amplicon of hsp70 was obtained from one cyst of G. duodenalis/100 microl, and this detection sensitivity significantly increased by 10(3)-fold when the cysts were given heat shock treatment. These findings prove that viable G. duodenalis cysts were successfully detected with a high degree of sensitivity by RT-PCR analysis targeting the hsp70 gene of G. duodenalis, thereby suggesting its practical potential for detecting viable G. duodenalis in environmental samples.
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PMID:Giardia duodenalis: improved detection of viable cysts by reverse transcription-PCR of heat shock-inducible hsp70 gene. 1970 45

Non-human primates (NHPs) are commonly infected with Cryptosporidium spp. and Giardia duodenalis. However, molecular characterisation of these pathogens from NHPs remains scarce. In this study, 2,660 specimens from 26 NHP species in China were examined and characterised by PCR amplification of 18S rRNA, 70kDa heat shock protein (hsp70) and 60kDa glycoprotein (gp60) gene loci for Cryptosporidium; and 1,386 of the specimens by ssrRNA, triosephosphate isomerase (tpi) and glutamate dehydrogenase (gdh) gene loci for Giardia. Cryptosporidium was detected in 0.7% (19/2660) specimens of four NHP species including rhesus macaques (0.7%), cynomolgus monkeys (1.0%), slow lorises (10.0%) and Francois' leaf monkeys (6.7%), belonging to Cryptosporidium hominis (14/19) and Cryptosporidium muris (5/19). Two C. hominis gp60 subtypes, IbA12G3 and IiA17 were observed. Based on the tpi locus, G. duodenalis was identified in 2.2% (30/1,386) of specimens including 2.1% in rhesus macaques, 33.3% in Japanese macaques, 16.7% in Assam macaques, 0.7% in white-headed langurs, 1.6% in cynomolgus monkeys and 16.7% in olive baboons. Sequence analysis of the three targets indicated that all of the Giardia-positive specimens belonged to the zoonotic assemblage B. Highest sequence polymorphism was observed at the tpi locus, including 11 subtypes: three known and eight new ones. Phylogenetic analysis of the subtypes showed that most of them were close to the so-called subtype BIV. Intragenotypic variations at the gdh locus revealed six types of sequences (three known and three new), all of which belonged to so-called subtype BIV. Three specimens had co-infection with C. hominis (IbA12G3) and G. duodenalis (BIV). The presence of zoonotic genotypes and subtypes of Cryptosporidium spp. and G. duodenalis in NHPs suggests that these animals can potentially contribute to the transmission of human cryptosporidiosis and giardiasis.
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PMID:Multilocus typing of Cryptosporidium spp. and Giardia duodenalis from non-human primates in China. 2514 45