Zoonotic Risk of Encephalitozoon cuniculi in Animal-Assisted Interventions: Laboratory Strategies for the Diagnosis of Infections in Humans and Animals

The involvement of animals for therapeutic purposes has very ancient roots. To date, it is clear that animal-assisted interventions (AAIs), in addition to ensuring the replacement of missing or deficient affects, improves psychophysiological parameters connected to human health. However, AAI could potentially present risks related to the transmission of infectious agents from animals to humans. Among these microorganisms, E. cuniculi is a microspore which induces pathological effects (fever, headache, nausea, vomiting, diarrhea, breathlessness, respiratory symptoms, and weakness) in both humans and animals. Consequently, an accurate and fast diagnosis of E. cuniculi infection, as well as the identification of new diagnostic approaches, is of fundamental importance. This literature review was carried out to provide an extensive and comprehensive analysis of the most recent diagnostic techniques to prevent and care for E. cuniculi-associated risks in the AAI field.

Zoonotic Microsporidia in Wild Lagomorphs in Southern Spain

Microsporidia are obligate intracellular protist-like fungal pathogens that infect a broad range of animal species, including humans. This study aimed to assess the presence of zoonotic microsporidia (Enterocytozoon bieneusi, Encephalitozoon intestinalis, Encephalitozoon hellem, and Encephalitozoon cuniculi) in organ meats of European wild rabbit (Oryctolagus cuniculus) and Iberian hare (Lepus granatensis) consumed by humans in Spain. Between July 2015 and December 2018, kidney samples from 383 wild rabbits and kidney and brain tissues from 79 Iberian hares in southern Spain were tested by species-specific PCR for the detection of microsporidia DNA. Enterocytozoon bieneusi infection was confirmed in three wild rabbits (0.8%; 95% CI: 0.0-1.7%) but not in hares (0.0%; 95% CI: 0.0-4.6%), whereas E. intestinalis DNA was found in one wild rabbit (0.3%; 95% CI: 0.0-0.8%) and three Iberian hares (3.8%; 95% CI: 0.0-8.0%). Neither E. hellem nor E. cuniculi infection were detected in the 462 (0.0%; 95% CI: 0.0-0.8%) lagomorphs analyzed. The absence of E. hellem and E. cuniculi infection suggests a low risk of zoonotic foodborne transmission from these wild lagomorph species in southern Spain. To the authors' knowledge, this is the first report of E. intestinalis infection in wild rabbits and Iberian hares. The presence of E. bieneusi and E. intestinalis in organ meats from wild lagomorphs can be of public health concern. Additional studies are required to determine the real prevalence of these parasites in European wild rabbit and Iberian hare.

Dynamics of parasitophorous vacuoles formed by the microsporidian pathogen Encephalitozoon cuniculi

It has been a long-standing debate if sexual development occurs in the microsporidian lineages. Previous studies, including morphological observations, ploidy analysis, and the presence of a sex-related locus, provided evidence of possible extant of sexual development. This study presents another line of evidence by monitoring the parasitophorous vacuoles (PVs) formed by Encephalitozoon cuniculi. Time lapse observations of infection cycles of E. cuniculi revealed that multiple PVs can be formed in a single host cell and the PVs in the single cell can merge (fusion) or split (fission). The dynamics of PVs may provide a route for interactions between genetically distinct microsporidian isolates during host infections.

Generation of genetic diversity in microsporidia via sexual reproduction and horizontal gene transfer

Microsporidia are obligate intracellular pathogens mainly infecting both vertebrate and invertebrate hosts. The group comprises approximately 150 genera with 1,200 species. Due to sequence divergence phylogenic reconstructions that are solely based on DNA sequence have been unprecise for these pathogens. Our previous study identified that three microsporidian genomes contained a putative sex-related locus similar to that of zygomycetes. In a comparison of genome architecture of the microsporidia to other fungi, Rhizopus oryzae, a zygomycete fungus, shared more common gene clusters with Encephalitozoon cuniculi, a microsporidian. This provides evidence supporting the hypothesis that microsporidia and zygomycete fungi may share a more recent common ancestor than other fungal lineages. Genetic recombination is an important outcome of sexual development. We describe genetic markers which will enable tests of whether sex occurs within E. cuniculi populations by analyzing tandem repeat DNA regions in three different isolates. Taken together, the phylogenetic relationship of microsporidia to fungi and the presence of a sex-related locus in their genomes suggest the microsporidia may have an extant sexual cycle. In addition, we describe recently reported evidence of horizontal gene transfer from Chlamydia to the E. cuniculi genome and show that these two obligate intracellular pathogens can infect the same host cells.