Explore chapters and articles related to this topic
The Parasitic Protozoa and Helminth Worms
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Microsporidiosis, caused by at least seven species belonging to five genera, is a rare but increasingly recognized condition in immunologically compromised patients particularly those suffering from AIDS. As the condition is virtually unknown in immunologically competent individuals, there is obviously some immune response that keeps these infections under control, but definite evidence that this is the case, or what the mechanisms are, is lacking. Apart from the epidemiological evidence, most of what is known comes from animal and in vitro studies which might not be relevant to what happens in humans. However, what is apparent is that perturbation of T cell function is a major cause of immunological failure leading to microsporidiosis, but as T cells are central to so many immunological responses, it is difficult to draw any firm conclusions about the nature of natural or acquired immunity to microsporidiosis in humans.
Encephalitozoon
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Alexandra Valencakova, Lenka Luptakova, Monika Halanova, Olga Danisova
Clinical manifestations of microsporidiosis are diverse and include intestinal, hepatobiliary, pulmonary, ocular, muscular, cerebral, and renal diseases. Human microsporidiosis has been described worldwide. The species known to infect humans have been isolated from a large variety of birds, fish, insects, and other animals, as well as from food and water sources.44
Malabsorption and microsporidia
Published in Ronald R. Watson, NUTRIENTS and FOODS in AIDS, 2017
A coprodiagnostic technique recently described by Weber et al.17 has significantly enhanced the ease by which the diagnosis of intestinal microsporidiosis can be made. The chromotrope-based staining technique uses a procedure that is similar to the trichrome method. The chromototrope concentration in the new stain is higher and includes chromotrope 2R, fast green, and phosphotungstic acid. Identification of microsporidia spores by this coprodiagnostic technique is as sensitive and as specific as light and electron microscopy.17,18 At our institution we currently rely upon this method to identify intestinal microsporidia. Other techniques that may be useful in the coprodiagnosis are Giemsa staining of stool specimens which stain microsporidia blue, but so are other fecal elements stained with the same color and chemifluorescent agents such as calcofluor white, which require fluorescent microscopy, and are not truly specific. Several serologic assays have been described for the detection of Encephalitozoon cuniculi, a rare cause of encephalitis in humans7,19 and able to cause disseminated microsporidiosis in a number of animal species.3,20,21 These include the enzyme-linked immunosorbent assay and an indirect immunofluorescent test. Cross-reaction with sporozoa (e.g., malaria) detracts from the reliability of such serologic assays and their value as screening tests for the prevalence of microsporidial infection.22
Coexistence of Fungal Keratitis in Bilateral Sequential Microsporidial Keratitis – A Rare Case Presentation
Published in Ocular Immunology and Inflammation, 2022
Richa Dhiman, Shweta Agarwal, Appakkudal R. Anand, Dhanurekha Lakshmipathy, Bhaskar Srinivasan, Geetha Iyer
Microsporidia are eukaryotic, obligate microorganisms that belong to the phylum Microspora, and were traditionally, classified as protozoans but are now considered closely related to fungi.1 Ocular disease presenting either as superficial punctate keratoconjunctivitis, corneal stromal keratitis, scleritis, or endophthalmitis is the second most common clinical manifestation of the microsporidia after digestive tract infection.2,3 Stromal keratitis is relatively rare, has an indolent course with symptoms ranging from 1 month to 2 years, and often resembles herpes simplex viral (HSV) or fungal keratitis with surgery being the mainstay of treatment.4 Presentation is usually unilateral and to date only three cases of bilateral microsporidiosis have been reported; none of which had a coexisting infection.5
Stromal Keratitis with Endophthalmitis Caused by Vittaforma Corneae in an Immunocompetent Patient: A Case Report
Published in Ocular Immunology and Inflammation, 2019
Lalida Pariyakanok, Vannarut Satitpitakul, Prasart Laksanaphuk, Kitiya Ratanawongphaibul, Chaturong Putaporntip, Somchai Jongwutiwes
To date, it remains unknown whether different clinical presentations in human microsporidiosis are influenced by the route of infections or different tissue tropisms of each species. However, an in vitro study has shown that spores of Vittaforma corneae could be internalized into various cell types comparable to those belonging to the genus Encephalitozoon; thereby, favoring the importance of infection route.6 On the other hand, severe ocular microsporidiosis has been diagnosed in both immunocompromised and immunocompetent hosts as reported herein.3 It is therefore likely that the interplay between host immunity and yet unknown pathogen virulence factors could determine disease severity. Undoubtedly, further studies are mandatory to resolve this issue.
Therapeutic targets for the treatment of microsporidiosis in humans
Published in Expert Opinion on Therapeutic Targets, 2018
Microsporidia have become important emerging human infections, particular with the increased use of immunomodulatory agents for disease therapy. These pathogens cause infection in both immune competent and immune-compromised individuals. Clinically, microsporidiosis can cause a range of symptoms including chronic diarrhea, abdominal pain, fever, renal failure, and fatigue, which carry a significant mortality risk to patients. Albendazole and fumagillin are the most widely used drugs for the therapy of microsporidiosis which use β-tubulin and MetAP2 as targets, respectively. Albendazole is effective for Encephalitozoon spp.; however, it is not effective against Ent. bieneusi. Fumagillin has a much broader range of effectiveness against microsporidia, including both Encephalitozoon spp. and Ent. bieneusi. New therapeutic targets for microsporidia include TIM, chitin synthase, polyamines, and topoisomerase IV. Drugs based on these targets are promising, but there is a need for additional studies before any are ready for clinical trials.