Latent microsporidiosis caused by Encephalitozoon cuniculi in immunocompetent hosts: a murine model demonstrating the ineffectiveness of the immune system and treatment with albendazole.

BACKGROUND: Microsporidia are obligate intracellular parasites causing severe infections with lethal outcome in immunocompromised hosts. However, these pathogens are more frequently reported as latent infections in immunocompetent individuals and raises questions about the potential risk of reactivation following induced immunosuppression. AIMS: To evaluate the possibility latent microsporidiosis, efficacy or albendazole, and reactivation, the authors monitored the course of E. cuniculi infection in immunocompetent BALB/c mice and immunodeficient SCID mice using molecular methods. METHODS: Mice were per orally infected with 10(7) spores of E. cuniculi. Selected groups were treated with albendazole, re-infected or chemically immunosuppressed by dexamethasone. The presence of microsporidia in the host's organs and feces were determined using PCR methods. Changes in numbers of lymphocytes in blood and in spleen after induction of immunosuppression were confirmed using flow cytometry analysis. RESULTS: Whereas E. cuniculi caused lethal microsporidiosis in SCID mice, the infection in BABL/c mice remained asymptomatic despite parasite dissemination into many organs during the acute infection phase. Albendazole treatment led to microsporidia elimination from organs in BALB/c mice. In SCID mice, however, only a temporary reduction in number of affected organs was observed and infection re-established post-treatment. Dexamethasone treatment resulted in a chronic microsporidia infection disseminating into most organs in BALB/c mice. Although the presence of E. cuniculi in organs of albendazole- treated mice was undetectable by PCR, it was striking that infection was reactivated by immunosuppression treatment. CONCLUSION: Our results demonstrated that microsporidia can successfully survive in organs of immunocompetent hosts and are able to reactivate from undetectable levels and spread within these hosts after induction of immunosuppression. These findings stress the danger of latent microsporidiosis as a life-threatening risk factor especially for individuals undergoing chemotherapy and in transplant recipients of organs originating from infected donors

Course of <i>Encepahlitozoon cuniculi</i> genotype II infection, including pattern of spore shedding and dissemination of infection to selected organs and tissues.

<p><b>a)</b> SCID mice, <b>b)</b> SCID mice treated with albendazole, <b>c)</b> BALB/c mice and BALB/c mice re-infected in chronic stage of infection, <b>d)</b> BALB/c mice treated with albendazole and BALB/c mice treated with albendazole with following re-infection, <b>e)</b> BALB/c mice immunosuppressed in chronic stage of infection, <b>f)</b> BALB/c mice immunosuppressed after albendazole treatment. <b>Light-gray field</b> – albendazole treatment; <b>dark-gray field</b> – dexamethasone immunosuppression; <b>black line</b> – course of <i>E. cuniculi</i> infection; <b>black dash line</b> - course of <i>E. cuniculi</i> re-infection; <b>cross</b> – <i>E. cuniculi</i> positive organ during primarily infection; <b>ring</b> – <i>E. cuniculi</i> positive organ during re-infection; <b>black square</b> – spores shedding during primarily infection; <b>black circle</b> – spores shedding during re-infection.</p

Design of experiments.

<p><b>^a</b>inoculation with 200 ul sterilized deionised water; <b>^b</b>infection with 10⁷<i>E. cuniculi</i> spores in 0.2 ml of sterilized deionised water; INF – infection; REINF – reinfection (black column); IMSUP – dexamethasone immunosuppression (highlighted in dark grey); TREAT – albendazole treatment (highlighted in light grey); <b>n1–</b> number of used animals; <b>n2</b>– number of dissected animals; <b>NS</b> – not shown; <b>x</b> – not observed due to mouse death; <b>DPI</b> – day post infection;</p

Long-Term Monitoring of Microsporidia, Cryptosporidium and Giardia Infections in Western Lowland Gorillas (Gorilla gorilla gorilla) at Different Stages of Habituation in Dzanga Sangha Protected Areas, Central African Republic

Background Infectious diseases pose one of the greatest threats to endangered species, and a risk of gastrointestinal parasite transmission from humans to wildlife has always been considered as a major concern of tourism. Increased anthropogenic impact on primate populations may result in general changes in communities of their parasites, and also in a direct exchange of parasites between humans and primates. Aims To evaluate the impact of close contact with humans on the occurrence of potentially zoonotic protists in great apes, we conducted a long-term monitoring of microsporidia, Cryptosporidium and Giardia infections in western lowland gorillas at different stages of the habituation process, humans, and other wildlife in Dzanga-Sangha Protected Areas in the Central African Republic. Results We detected Encephalitozoon cuniculi genotypes I and II (7.5%), Enterocytozoon bieneusi genotype D and three novel genotypes (gorilla 1–3) (4.0%), Giardia intestinalis subgroup A II (2.0%) and Cryptosporidium bovis (0.5%) in gorillas, whereas in humans we found only G. intestinalis subgroup A II (2.1%). In other wild and domestic animals we recorded E. cuniculi genotypes I and II (2.1%), G. intestinalis assemblage E (0.5%) and C. muris TS03 (0.5%). Conclusion Due to the non-specificity of E. cuniculi genotypes we conclude that detection of the exact source of E. cuniculi infection is problematic. As Giardia intestinalis was recorded primarily in gorilla groups with closer human contact, we suggest that human-gorilla transmission has occurred. We call attention to a potentially negative impact of habituation on selected pathogens which might occur as a result of the more frequent presence of humans in the vicinity of both gorillas under habituation and habituated gorillas, rather than as a consequence of the close contact with humans, which might be a more traditional assumption. We encourage to observe the sections concerning hygiene from the IUCN best practice guidelines for all sites where increased human-gorilla contact occurs

Neighbour-joining tree based on nucleotide sequences of the whole ITS region of Enterocytozoon bieneusi isolates, including our new sequences (underlined).

<p>Genotypes previously found in apes and humans are shaded. The host is listed for each sample. Values on branches are percent bootstrapping using 1 000 replicates. The bootstrap proportions greater than 50% are shown on each branch. Nucleotide sequences generated from this study are underlined and are deposited in the GenBank under Accession Nos. JQ837793-JQ837800.</p

<i>Enterocytozoon bieneusi</i>, <i>Encephalitozoon cuniculi</i>, <i>Cryptosporidium</i> spp. and <i>Giardia intestinalis</i> infection in wild western lowland gorillas (<i>Gorilla gorilla gorilla</i>) under different levels of human contact.

<p><b>D</b> =  <i>E. bieneusi</i> genotype D; <b>gorilla 1</b>  =  <i>E. bieneusi</i> genotype gorilla 1; <b>gorilla 2</b>  =  <i>E. bieneusi</i> genotype gorilla 2; <b>gorilla 3</b>  =  <i>E. bieneusi</i> genotype gorilla 3; <b>EC I</b>  =  <i>E. cuniculi</i> genotype I; <b>EC II</b>  =  <i>E. cuniculi</i> genotype II; <b>A</b>  =  <i>Giardia intestinalis</i> assemblage A; <b>n¹</b> number of samples; <b>n²</b> number of animals sampled.</p

Enterocytozoon bieneusi, Encephalitozoon cuniculi, Cryptosporidium spp. and Giardia intestinalis infection in humans, wild and domestic animals.

<p><b>n</b>  =  number of samples; <b>EC I</b>  =  <i>E. cuniculi</i> genotype I; <b>EC II</b>  =  <i>E. cuniculi</i> genotype II; <b>E</b>  =  <i>Giardia intestinalis</i> assemblage E; <b>A</b>  =  <i>Giardia intestinalis</i> assemblage A.</p