Co-infection par des microsporidies et des cryptosporidies chez un nouveau-né infecté par le VIH

Chronic Infections in Mammals Due to Microsporidia

Microsporidia are pathogenic organism related to fungi. They cause infections in a wide variety of mammals as well as in avian, amphibian, and reptilian hosts. Many microsporidia species play an important role in the development of serious diseases that have significant implications in human and veterinary medicine. While microsporidia were originally considered to be opportunistic pathogens in humans, it is now understood that infections also occur in immune competent humans. Encephalitozoon cuniculi, Encephalitozoon intestinalis, and Enterocytozoon bieneusi are primarily mammalian pathogens. However, many other species of microsporidia that have some other primary host that is not a mammal have been reported to cause sporadic mammalian infections. Experimental models and observations in natural infections have demonstrated that microsporidia can cause a latent infection in mammalian hosts. This chapter reviews the published studies on mammalian microsporidiosis and the data on chronic infections due to these enigmatic pathogens.

First identification of genotypes of Enterocytozoon bieneusi (Microsporidia) among symptomatic and asymptomatic children in Mozambique

Enterocytozoon bieneusi is a human pathogen with a broad range of animal hosts. Initially, E. bieneusi was considered an emerging opportunistic pathogen in immunocompromised, mainly HIV-infected patients, but it has been increasingly reported in apparently healthy individuals globally. As in other African countries, the molecular epidemiology of E. bieneusi in Mozambique remains completely unknown. Therefore, we undertook a study to investigate the occurrence and genetic diversity of E. bieneusi infections in children with gastrointestinal symptoms as well as in asymptomatic children in Mozambique. Individual stool specimens were collected from 1,247 children aged between 0 and 14 years-old living in urban and rural settings in Zambézia (n = 1,097) and Maputo (n = 150) provinces between 2016 and 2019. Samples were analysed for E. bieneusi by nested-PCR targeting the internal transcribed spacer (ITS) region of the rRNA gene. All positive amplicons were confirmed and genotyped. Penalised logistic regression (Firth) was used to evaluate risk associations. The overall prevalence of E. bieneusi in this children population was 0.7% (9/1,247). A 10-fold higher prevalence was found in Maputo (4.0%; 6/150) than in Zambézia (0.3%; 3/1,097). All E. bieneusi-positive samples were from children older than 1-year of age, and most (8/9) from asymptomatic children. Nucleotide sequence analysis of the ITS region revealed the presence of four genotypes, three previously reported (Peru11, n = 1; Type IV, n = 2, and S2, n = 2) and a novel genotype (named HhMzEb1, n = 4). Novel genotype HhMzEb1 was identified in both asymptomatic (75%, 3/4) and symptomatic (25%, 1/4) children from a rural area in Maputo province in southern Mozambique. Genotypes HhMzEb1, Peru11, S2, and Type IV belonged to the Group 1 that includes genotypes with low host specificity and the potential for zoonotic and cross-species transmission. Being infected by enteric protozoan parasites and no handwashing were identified as risk associations for E. bieneusi infection. This study reports the first investigation of E. bieneusi genotypes in Mozambique with the identification of three previously reported genotypes in humans as well as a novel genotype (HhMzEb1). Findings highlight the need to conduct additional research to elucidate the epidemiology of E. bieneusi in the country, especially in rural areas where poor hygiene conditions still prevail. Special attention should be paid to the identification of suitable animal and environmental reservoirs of this parasite and to the characterization of transmission pathways.

Molecular identification of Enterocytozoon bieneusi and Encephalitozoon spp. in immunodeficient patients in Ahvaz, Southwest of Iran

Microsporidia are often considered as an opportunistic infection in patients with impaired immune systems such as transplant recipients and patients with acquired immune deficiency syndrome (AIDS). Due to the increasing prevalence of parasitic infections and immunodeficiency diseases; the aim of the study is to evaluate molecular identification of Enterocytozoon bieneusi and Encephalitozoon spp. in immunodeficient patients in Ahvaz, southwest of Iran. At first, 310 stool samples were collected from patients with immunodeficiency. The specimens were stained by modified trichrome (weber) and were examined microscopically. The extracted DNA samples were evaluated by multiplex/nested PCR method. The products of multiplex/nested PCR were explored by RFLP method using the restriction enzyme of Mnl1. Of 310, 93 samples were suspected positive for microsporidia by the staining. Also, of 310, 88 samples were positive by the multiplex/nested-PCR test that 62 samples were positive for E. bieneusi as well as 26 were detected as Encephalitozoon species that including 3 E. cuniculi, 19 E. intestinalis and 4 E. hellem. Of 62 E. bieneusi, 45, 16 and 1 were detected as genotype D, M and WL11, respectively. Also, Of 3 E. cuniculi, 1 and 2 cases were identified as genotype I and II, respectively. All E. hellem samples were included genotype 1A. Our findings revealed a relatively high prevalence of microsporidia species in immunodeficient patients. The highest risk of this infection is at individuals with impaired immune systems that it can be life-threatening in people with immune system dysfunction. It is essential that the high-risk people should be receiving the information about the risk of direct contact with infected individuals and animals.

The first study on opportunistic intestinal microsporidiosis in IBD patients receiving immunosuppressive medications in Iran

Microsporida are known as opportunistic unicellular organisms and have recently been reclassified as fungi that have been frequently reported from patients with congenital and acquired immunity failure disorders, worldwide. However, use of immunosuppressive medications in inflammatory bowel disease (IBD) patients significantly decreases overall immunity, and increases their susceptibility to opportunistic infections. Totally, 71 stool samples were collected from IBD patients consisted of 69 ulcerative colitis (UC) patients and two Crohn's disease (CD) patients. All patients had taken immunosuppressive and/or immunomodulator drugs for at least 3 weeks. DNA was extracted from all stool samples and Nested PCR was performed using genus-specific primers based on small subunit ribosomal RNA (SSU rRNA) gene. Fisher's Exact Test was applied to evaluate statistical association between microsporidia infection and sex, age and types of IBD. Mean of age ± s.d., women and men percentage of the attended patients were 36·17 ± 11·93, 60·6%, and 39·4%, respectively. A 440-bp fragment of SSU rRNA gene attributed to Enterocytozoon bieneusi was amplified from 12·7% of IBD patients. No Encephalitozoon DNA was detected in the samples. No microsporidia-positive sample was found in CD patients. Fisher's Exact Test showed that there was no statistically significant correlation between intestinal microsporidiosis and age, sex, and IBD types with P values: 0·389, 1·00, and 1·00, respectively. This study has shown IBD patients undergoing immunosuppressive/immunomodulators medications, which may be susceptible to intestinal microsporida infection. E. bieneusi is the commonest intestinal microsporidan reported from IBD patients.

Microsporidiosis: not just in AIDS patients

PURPOSE OF REVIEW

Microsporidia have emerged as causes of opportunistic infections associated with diarrhea and wasting in AIDS patients. This review describes recent reports of microsporidiosis in HIV-infected individuals and the growing awareness of microsporidiosis in non-HIV-infected populations.

RECENT FINDINGS

Microsporidia were only rarely recognized as causes of disease in humans until the AIDS pandemic. Implementation of combination antiretroviral therapy (cART) to curtail HIV replication and restore immune status drastically reduced the occurrence of opportunistic infections, including those due to microsporidia, in HIV-infected individuals. In developing countries where cART is not always accessible, microsporidiosis continues to be problematic. Improvement of diagnostic methods over the previous 25 years led to identification of several new species of microsporidia, many of which disseminate from enteric to systemic sites of infection and contribute to some unexpected lesions. Among non-HIV-infected but immune-suppressed individuals, microsporidia have infected organ transplant recipients, children, the elderly, and patients with malignant disease and diabetes. In otherwise healthy immune-competent HIV seronegative populations, self-limiting diarrhea occurred in travelers and as a result of a foodborne outbreak associated with contaminated cucumbers. Keratitis due to microsporidiosis has become problematic and a recent longitudinal evaluation demonstrated that non-HIV-infected individuals seropositive for microsporidia who had no clinical signs continued to intermittently shed organisms in feces and urine.

SUMMARY

Greater awareness and implementation of better diagnostic methods are demonstrating that microsporidia contribute to a wide range of clinical syndromes in HIV-infected and non-HIV-infected people. As such, microsporidia should be considered in differential diagnoses if no other cause can be defined.