[Animal reservoirs of human virulent microsporidian species].

Abstract

The main objective of the present study was to determined the occurrence of Encephalitozoon intestinalis, E. hellem, E. cuniculi, and Enterocytozoon bieneusi in Poland in animal faecal using the FISH (Fluorescent In Situ Hybridization) and multiplex FISH techniques. Additional objectives included: (1) identification of animal hosts of microsporidia that are infectious to humans amongst free-ranging, captive, livestock and domestic animals; (2) a molecular analysis of randomly selected parasite isolates and determination of their zoonotic potential; (3) evaluation of the role of animals in the dissemination of microsporidia spores in the environment, and an estimation of the potential risk of infection for other animals and humans. A total of 1340 faecal samples collected from 178 species of animals were examined using conventional staining (chromotrope-2R and calcofluor white M2R staining) and molecular techniques (FISH and multiplex FISH techniques). Microsporidian spores were detected in 33 faecal samples (2.5%) obtained from 17 animal species. Microsporidia were demonstrated more often in birds (6.1%) than in mammals (0.7%); the difference was statistically significant (p < 0.00001). In addition, the prevalence of microsporidian infections in waterfowl was significantly higher than the prevalence of microsporidian infections in other animals (p < 0.03). Animal reservoirs of human infectious microsporidia were disclosed in six of 38 sites where faecal samples were taken from animals. Three species of human virulent microsporidia were identified in animals. Spores of E. hellem were found in 25 faecal samples (1.9%) taken from 12 bird species (6 zoo bird species, 4 free-ranging bird species, 2 livestock bird species). Spores of E. intestinalis were identified in five faecal samples (0.4%) taken from two livestock bird species and two zoo mammal species. In turn, E. bieneusi spores were detected only in three faecal samples (0.2%) taken from three zoo mammal species. It was demonstrated that the new hosts of E. hellem are the following bird species: mallard duck (Anas platyrhynchos), greyleg goose (Anser anser), mute swan (Cygnus olor), black-necked swan (Cygnus melancoryphus), black swan (Cygnus atratus), coscoroba swan (Coscoroba coscoroba), black-crowned crane (Balearica pavonina), nicobar pigeon (Caloenas nicobarica) and carrion crow (Corvus cornix). In addition, E. hellem was found for the first time in birds from the Anseriformes and Gruiformes orders. Whereas E. intestinalis was disclosed for the first time in the domestic goose (Anser anser f. domestica), red ruffed lemur (Varecia variegata rubra) and the ring-tailed lemur (Lemur catta), while the black lemur (Eulemur macaco flavifrons), mongoose lemur (Eulemur mongoz) and the Visayan warty pig (Sus cebifrons negrinus) were first found to carry E. bieneusi. The mammal species that were found to carry E. bieneusi and E. intestinalis are included in The IUCN Red List of Threatened Species. The results of the present study are significant from an epidemiological point of view. The wild, livestock and zoo animals that were found to carry microsporidia live in different conditions, and thus their role as animal reservoirs for these dangerous pathogens varies. Waterfowl birds may be the main source of contamination of surface waters with E. hellem spores and the protection of surface waters is virtually impossible. Moreover, isolates of E. hellem from mute swans have SSU rRNA sequences identical to E. hellem genotype reported 10 years ago in HIV-positive patient in USA (GenBank Accession no. L19070). This result indicate that E. hellem from mute swans can be a potential source of infection for humans. The contamination of the human environment with microsporidian spores infectious to humans is also facilitated by farm and synanthropic birds, because E. hellem and E. intestinalis were found in farms pigeons, domestic goose and the carrion crow. These birds can also be the source of infectious for breeders and ornithologists. The occurrence of microsporidiosis in animals kept in zoological gardens may constitute a deadly hazard not only for the animals themselves, but also for zoo personnel and visitors. The identification of animal reservoirs of E. hellem, E. intestinalis and E. bieneusi in Poland points to the possibility of infection of humans. The results of the present study have shown that the FISH technique, although time-consuming, is very sensitive, not overly costly and--what is of prime importance--it enables identification of microsporidian species, and therefore should be used for diagnosing microsporidiosis in humans and animals.