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Opportunistic properties of Nosema algerae (Microspora), a mosquito parasite, in immunocompromised mice
T Trammer1, F Dombrowski, M Doehring
1Institute of Medical Parasitology, Bonn, Germany. malaria@parasit.meb.unibonn.de
Abstract:
In the last ten years microsporidia have been recognized as opportunistic pathogens in AIDS patients. The sources of infection and the mechanisms of transmission of these organisms in humans are mostly uncertain. Transmission of invertebrate microsporidia to mammals is normally considered impossible, temperature being a limiting factor for development. Mice treated with cortisone acetate and with cyclosporin A, respectively, as well as athymic nice were injected intravenously, intranasally, perorally and subcutaneously with spores of Nosema algerae, a microsporidian species of culicine mosquitoes. No infection could be detected in tissue samples of cortisone acetate and cyclosporin A treated mice. However, the experimental inoculation of spores into the tail and foot of athymic mice caused severe infection in skeletal muscles and the connective tissue. In some tails, nerve tissue and bone marrow were also infected. Vegetative stages and spores were seen in direct contact to host cell cytoplasma. For the first time the prolonged and progressive development of an invertebrate microsporidium in a mammalian host is shown. The possibility of invertebrate microsporidia as a source of human microsporidiosis should now be taken into consideration.
Insights
Invertebrate microsporidia, previously thought unable to infect mammals, can cause severe infections in immunosuppressed mice. This finding suggests a potential new source for human microsporidiosis, impacting immunocompromised individuals.
Area of Science:
- Microbiology
- Parasitology
- Immunology
Background:
- Microsporidia are increasingly recognized as opportunistic pathogens in AIDS patients.
- The transmission routes and sources of human microsporidiosis remain largely unknown.
- Invertebrate microsporidia were traditionally considered unable to infect mammals due to temperature limitations.
Purpose of the Study:
- To investigate the potential for invertebrate microsporidia to infect mammalian hosts.
- To determine if Nosema algerae, a mosquito microsporidian, can establish infection in mice.
Main Methods:
- Athymic mice, cortisone acetate-treated mice, and cyclosporin A-treated mice were inoculated with Nosema algerae spores via various routes (intravenous, intranasal, peroral, subcutaneous).
- Infection was assessed by examining tissue samples for microsporidian presence.
- Experimental inoculation into the tail and foot of athymic mice was performed.
Main Results:
- No infection was detected in cortisone acetate or cyclosporin A treated mice.
- Athymic mice experimentally inoculated in the tail and foot developed severe infections in skeletal muscles and connective tissue.
- Infection in athymic mice extended to nerve tissue and bone marrow in some cases, with direct host cell contact observed.
Conclusions:
- This study demonstrates, for the first time, the prolonged development of an invertebrate microsporidium in a mammalian host.
- The findings challenge the notion that invertebrate microsporidia cannot infect mammals.
- Invertebrate microsporidia should now be considered a potential source of human microsporidiosis, particularly in immunocompromised populations.