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The Future of Parasitology
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
With respect to detection efforts, you may recall at the start of Chapter 2 we discussed an unpleasant case of cyclosporiasis caused by the apicomplexan Cyclospora cayetanensis. Many other food-borne parasites create similar concerns including apicomplexans like Cryptosporidium, Toxoplasma and helminths like Trichuris or Ascaris. Improved methods to detect parasite-contaminated food are needed. One recent approach targeted the internal transcribed spacer-1 (ITS-1) region among the genes encoding ribosomal RNAs of C. cayetanensis in a real-time PCR format to detect the presence of this parasite in extracts from raspberries. Real-time PCR, or quantitative PCR (qPCR), monitors the progress of a PCR reaction in real time, allowing one to identify when the amplified target can first be detected. The higher the starting number of copies of the target molecule, in this case, the ITS-1 gene of C. cayetanensis, the sooner it is detected. Importantly for this particular application, an internal control is included to test whether a non-parasite gene would also be amplified, this as a check against the presence of general PCR inhibitors like pectin that are common in fruit, which could potentially cause false negatives to be reported.
Cyclospora cayetanensis: Portrait of an Intriguing and Enigmatic Protistan Parasite
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Annunziata Giangaspero, Robin B. Gasser
Cyclospora cayetanensis is an obligate monoxenous intracellular coccidian parasite that infects the epithelium of the intestine or bile duct [2], leading to significant morbidity and mortality. Following documentation in the early 1990s as the causative agent of numerous outbreaks of diarrheal illness in the developed world, this emerging pathogen appears to target travelers to endemic countries or people who consume fresh produce (mostly soft fruits and leafy vegetables) imported from developing countries, as well as those who drink contaminated water.
Protozoa
Published in Loretta A. Cormier, Pauline E. Jolly, The Primate Zoonoses, 2017
Loretta A. Cormier, Pauline E. Jolly
Cyclospora cayetanensis is an intestinal parasite that is spread by ingesting food or water that has been contaminated with feces (CDC 2013). It has a worldwide distribution but is most common in developing areas (Suh et al. 2015). C. cayetanensis is a common cause of traveler’s diarrhea, but it has become a concern as an emerging disease due to several large-scale food-borne outbreaks in the late 1990s in the United States and Canada (Shields and Olson 2003). C. cayetanensis infection is sometimes asymptomatic, but common symptoms are watery diarrhea, vomiting, headache, fever, and other flu-like-symptoms (CDC 2013). It is also of concern because it has been associated with more serious sequelae including Guillain-Barré syndrome, reactive arthritis syndrome, and cholecystitis (Shields and Olson 2003).
Validation and maintaining laboratory developed molecular tests compliant with ISO15189 for diagnosis of intestinal parasitic infections
Published in Expert Review of Molecular Diagnostics, 2022
The in silico specificity determines if primers and probes used to amplify and detect a target sequence are unique for the intended organism. Although false positive results will only occur if both primers and probe will anneal to the DNA of a nonintended organism, the efficiency of a PCR will decrease if one of the primers or probes will anneal to the DNA of another organism. Sequences of related and non-related organisms are obtained from the GenBank and by BLAST search of the primers and probes with exclusion of the target organism. When no relevant matches are found this is reported for each primer and probe sequence in the validation report. Suspicious matches are aligned with the target sequence together with the primers and probes assessed for their relevance. In some cases one can accept a certain degree of non-specificity for example if a PCR turns out to be genus- instead of species-specific. In Figure 2a and 2b, the alignment for a Cyclospora cayetanensis PCR and for an Ancylostoma duodenale PCR are given [9,10]. In both examples, the in silico analysis for specificity revealed that the primers and probes are not unique for the initially intended species and therefore do not meet the preset criterion. However, in both cases this is accepted with an adaptation in reporting the results to the clinic. In the first example results are reported as Cyclospora cayetanensis/Cystoisospora belli DNA detected or not detected and although the treatment for both infections is the same additional microscopy will be performed to confirm the presence of one of the two parasites. In the second example the result of the PCR is reported as Ancylostoma DNA detected or not-detected and thus resulting in a genus- rather than a species-specific result. Including Ancylostoma caninum within the current Ancylostoma genus PCR as screening assay followed by a multiplex Ancylostoma species-specific PCR will be considered in future work [11].
The impact of water crises and climate changes on the transmission of protozoan parasites in Africa
Published in Pathogens and Global Health, 2018
Shahira A. Ahmed, Milena Guerrero Flórez, Panagiotis Karanis
In SSA and Asia (developing settings), the common water enteric pathogenic protozoa include G. duodenalis (intestinalis), Entamoeba spp., Cryptosporidium spp., Cyclospora cayetanensis, and Microsporidia. Whereas other species such as Blastocystis spp. and Dientamoeba fragilis are usually isolated from developed countries [13,14].