Microsporidia are obligate intracellular spore-forming protozoal parasites belonging to the phylum Microspora. Their host range is extensive, including most invertebrates and all classes of vertebrates. More than 100 microsporidial genera and almost 1,000 species have now been identified. Five genera (Enterocytozoon spp., Encephalitozoon spp., Septata spp., Pleistophora sp., and Nosema spp.) and unclassified microsporidia (referred to by the collective term Microsporidium) have been associated with human disease, which appears to manifest primarily in immunocompromised persons. The clinical manifestations of microsporidiosis are diverse and include intestinal, pulmonary, ocular, muscular, and renal disease. Among persons not infected with human immunodeficiency virus, ten cases of microsporidiosis have been documented. In human immunodeficiency virus-infected patients, on the other hand, over 400 cases of microsporidiosis have been identified, the majority attributed to Enterocytozoon bieneusi, an important cause of chronic diarrhea and wasting. Diagnosis of microsporidiosis currently depends on morphological demonstration of the organisms themselves. Initial detection of microsporidia by light microscopic examination of tissue sections and of more readily obtainable specimens such as stool, duodenal aspirates, urine, sputum, nasal discharge, bronchoalveolar lavage fluid, and conjunctival smears is now becoming routine practice. Definitive species identification is made by using the specific fluorescein-tagged antibody (immunofluorescence) technique or electron microscopy. Treatment options are limited, but symptomatic improvement of Enterocytozoon bieneusi infection may be achieved with the anthelmintic-antiprotozoal drug albendazole. Preliminary observations suggest that Septata intestinalis and Encephalitozoon infections may be cured with albendazole. Progress is being made with respect to in vitro propagation of microsporidia, which is crucial for developing antimicrosporidial drugs. Furthermore, molecular techniques are being developed for diagnostic purposes, taxonomic classification, and analysis of phylogenetic relationships of microsporidia.

Human microsporidial infections.

Toxoplasma gondii is a coccidian parasite which utilizes felids as definitive hosts, and which has an unusually wide intermediate host range The parasite was initially described by Nicolle and Manceaux in 1908 from the rodent, Ctenodactylus gundi Infection with T gondii is one of the most common parasitic infections of man and other warm-blooded animals It has been found worldwide from Alaska to Australia Nearly one-third of humanity has been exposed to this parasite; serologic surveys indicate that T gondii infections are common in wild carnivores, including pigs, bears, felids, fox, raccoons, and skunks Clinical and subclinical toxoplasmosis has been reported from wild cervids, ungulates, marsupials, monkeys, and marine mammals Southern sea otter populations have been severely impacted by Toxoplasma infections

Biology and epidemiology of Toxoplasma gondii in man and animals

The oriental liverfluke, Clonorchis sinensis, is of major socioeconomic importance in parts of Asia, including China, Japan, Korea, Taiwan, and Vietnam. The parasite is transmitted via snails to freshwater fish, and then to human beings and other piscivorous mammals, and causes substantial clinical or subclinical disease, known as clonorchiasis. There is considerable evidence for an aetiological relation between clonorchiasis and cholangiocarcinoma in human beings. It is estimated that about 35 million people are infected globally, of whom approximately 15 million are in China. Although very little information from China has been published in the English language, recent analyses of epidemiological data sets suggest that clonorchiasis is having an increased human-health impact due to the greater consumption of raw freshwater fish. To gain an improved insight into clonorchiasis in China, this review provides a background on the parasite and its life cycle, summarises key aspects regarding the pathogenesis, diagnosis, and treatment of clonorchiasis, describes the geographic distribution and prevalence of clonorchiasis, and makes some recommendations for future research and the control of this important disease.

https://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(04)01252-6.pdf

Clonorchiasis: a key foodborne zoonosis in China

Microsporidia are long-known parasitic organisms of almost every animal group, including invertebrates and vertebrates. Microsporidia emerged as important opportunistic pathogens in humans when AIDS became pandemic and, more recently, have also increasingly been detected in otherwise immunocompromised patients, including organ transplant recipients, and in immunocompetent persons with corneal infection or diarrhea. Two species causing rare infections in humans, Encephalitozoon cuniculi and Brachiola vesicularum, had previously been described from animal hosts (vertebrates and insects, respectively). However, several new microsporidial species, including Enterocytozoon bieneusi, the most prevalent human microsporidian causing human immunodeficiency virus-associated diarrhea, have been discovered in humans, raising the question of their natural origin. Vertebrate hosts are now identified for all four major microsporidial species infecting humans (E. bieneusi and the three Encephalitozoon spp.), implying a zoonotic nature of these parasites. Molecular studies have identified phenotypic and/or genetic variability within these species, indicating that they are not uniform, and have allowed the question of their zoonotic potential to be addressed. The focus of this review is the zoonotic potential of the various microsporidia and a brief update on other microsporidia which have no known host or an invertebrate host and which cause rare infections in humans.

http://lib.ajaums.ac.ir/booklist/clinical microbiology reviews-july.pdf

Zoonotic Potential of the Microsporidia

Summary Background Food-borne trematodiases are a group of neglected tropical diseases caused by liver, lung, and intestinal parasitic fluke infections. As part of the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD 2010 study) and a WHO initiative, we assessed the global burden of human food-borne trematodiasis, as expressed in disability-adjusted life years (DALYs) for the year 2005. Methods We systematically searched electronic databases for reports about human food-borne trematodiasis without language restriction, between Jan 1, 1980, and Dec 31, 2008. We used a broad search strategy with a combination of search terms and parasite and disease names. The initial search results were then screened on the basis of title, abstract, and, finally, full text. Relevant quantitative and qualitative data on human prevalence, morbidity, and mortality of food-borne trematodiasis were extracted. On the basis of available information on pathological and clinical appearance, we developed simplified disease models and did meta-analyses on the proportions and odds ratios of specified sequelae and estimated the global burden of human food-borne trematodiasis. Findings We screened 33 921 articles and identified 181 eligible studies containing quantitative information for inclusion in the meta-analyses. About 56·2 million people were infected with food-borne trematodes in 2005: 7·9 million had severe sequelae and 7158 died, most from cholangiocarcinoma and cerebral infection. Taken together, we estimate that the global burden of food-borne trematodiasis was 665 352 DALYs (lower estimate 479 496 DALYs; upper estimate 859 051 DALYs). Furthermore, knowledge gaps in crucial epidemiological disease parameters and methodological features for estimating the global burden of parasitic diseases that are characterised by highly focal spatial occurrence and scarce and patchy information were highlighted. Interpretation Despite making conservative estimates, we found that food-borne trematodiases are an important cluster of neglected diseases. Funding Swiss National Science Foundation; Institute for Health Metrics and Evaluation.

https://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(11)70294-8.pdf

Global burden of human food-borne trematodiasis: a systematic review and meta-analysis

Rabbits infected either orally or intratracheally with cell culture-grown Encephalitozoon cuniculi were monitored regularly for serum antibody levels and E. cuniculi in the urine. Their responses were compared with intravenously inoculated and uninoculated control rabbits. All rabbits receiving E. cuniculi developed serum antibodies, generally within 3 weeks, and excreted E. cuniculi by 6 weeks. In the acute stage of infection, the organs most affected were lung, kidney and liver; the brain and gut were unaffected. However, during chronic infection, the brain, kidney, and heart were the only organs found to be involved. Antibody levels were very high at this stage. Thus both the oral and tracheal routes may be normal routes of infection with E. cuniculi in adult rabbits.

An Investigation of the Route and Progression of Encephalitozoon cuniculi Infection in Adult Rabbits

The Longevity of Clonorchis Sinensis

During a histopathologic survey of 240 dasyurid marsupials a high prevalence of infection of Toxoplasma gondii was found in eight of the nine species examined. Amongst the infected species, endemic infection in field animals was proved in Dasyuroides byrnei, but there was also good evidence of laboratory infection probably derived from raw sheep tissues in their diet. Infection was never demonstrated in animals less than six months of age. The 21 Antechinus stuartii examined remained free from infection despite a lengthy stay in the laboratory and a similar diet. This freedom from infection may indicate a particular resistance to Toxoplasma infection by this species.

https://bioone.org/journals/Journal-of-Wildlife-Diseases/volume-11/issue-4/0090-3558-11.4.543/TOXOPLASMOSIS-IN-DASYURID-MARSUPIALS/10.7589/0090-3558-11.4.543.pdf

Harold D. Attwood

Papers

An Investigation of the Route and Progression of Encephalitozoon cuniculi Infection in Adult Rabbits

The Longevity of Clonorchis Sinensis

Toxoplasmosis in dasyurid marsupials

Spontaneous malignant neoplasms in dasyurid marsupials.

Pathology of Lung Tumors