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Emerging pathogens: Isospora, Cyclospora and microsporidia
Abstract:
Isospora belli, Cyclospora cayetanensis as well as several species of microsporidia are recognized as emerging protozoan pathogens of humans. All are obligate intracellular parasites, with Isospora and the microsporidia being primarily associated with immunocompromised hosts. Cyclospora is a cause of traveller's diarrhoea, and is responsible for water-borne and food-borne outbreaks of disease. Drug treatment is available for these infections. Improved diagnostic methods including the autofluorescence of I. belli and C. cayetanensis oocysts have assisted in the routine detection of these pathogens. Since the recognition of immunosuppression due to HIV infection, microsporidia have become recognized as important human pathogens with a continuing expansion of the parasite-associated clinico-pathological spectrum. The small size, intracellular nature and poor staining properties with many histological stains result in under-reporting of microsporidial infections. Trichrome stain and optical brighteners are used to detect spores in faeces, urines, respiratory secretions and other aspirates. Electron microscopy remains an important diagnostic method but its sensitivity is relatively poor. Molecular techniques should overcome current diagnostic limitations. The ability to extract DNA and amplify by PCR directly from clinical samples has increased the usefulness of molecular methods. Restriction fragment length polymorphism analysis of amplicons can be used to determine genus, species and strain types of various microsporidia. Increased specificity is required in primer design because current primers used for amplifying non-microsporidian DNA also amplify microsporidian DNA. Diagnosis and pathogen characterisation rely increasingly on PCR-based approaches, and the sequence analysis approach becomes increasingly feasible and affordable. However, robust, reliable and sensitive methods are still required for dissecting pathogenesis, epidemiology, transmission routes and sources of infections.
Insights
Emerging protozoan pathogens like Isospora belli, Cyclospora cayetanensis, and microsporidia pose significant health risks. Advanced molecular techniques are crucial for accurate diagnosis and characterization of these infections, especially in immunocompromised individuals.
Area of Science:
- Medical Parasitology
- Infectious Diseases
- Molecular Diagnostics
Background:
- Emerging protozoan pathogens, including Isospora belli, Cyclospora cayetanensis, and microsporidia, are increasingly recognized as significant human health threats.
- Isospora and microsporidia primarily affect immunocompromised hosts, while Cyclospora causes traveler's diarrhea and outbreaks linked to contaminated food and water.
- Current diagnostic methods face limitations due to the small size, intracellular nature, and poor staining properties of these parasites, leading to under-reporting.
Purpose of the Study:
- To review the current understanding of emerging protozoan pathogens and their diagnostic challenges.
- To highlight the advancements and limitations of diagnostic methods, including traditional staining and newer molecular techniques.
- To emphasize the need for improved diagnostic tools for accurate pathogen characterization and epidemiological studies.
Main Methods:
- Review of existing literature on Isospora belli, Cyclospora cayetanensis, and microsporidia.
- Discussion of diagnostic techniques such as autofluorescence, trichrome stain, optical brighteners, and electron microscopy.
- Exploration of molecular methods including PCR, restriction fragment length polymorphism (RFLP), and sequence analysis.
Main Results:
- Autofluorescence aids in the detection of I. belli and C. cayetanensis oocysts.
- Molecular techniques, particularly PCR, show promise in overcoming diagnostic limitations by enabling DNA amplification from clinical samples.
- Restriction fragment length polymorphism (RFLP) allows for genus, species, and strain typing of microsporidia.
- Current PCR primers require increased specificity to avoid amplifying non-target DNA.
Conclusions:
- Accurate diagnosis and characterization of these emerging protozoan infections are increasingly reliant on PCR-based approaches.
- Sequence analysis is becoming more feasible and affordable for pathogen identification.
- There is an ongoing need for robust, sensitive, and reliable methods to fully understand the pathogenesis, epidemiology, transmission, and sources of these parasitic infections.