Protistology 3 (4) 265–272 (2004)
Identification of Microsporidia infections in nature: light microscopy or PCR?
Yuliya Y. Sokolova 1, 2, 3, Igor M. Sokolov 1, 4 and James R. Fuxa 1
1 Department of Entomology Louisiana Agricultural Experiment Station and Louisiana State
University Agricultural Center Baton Rouge, Louisiana, USA
Thelohania solenopsae is a natural pathogen of the red imported fire ant Solenopsis invictae, a pest widely distributed in the southern USA. Several introductions of T. solenopsae have succeeded in certain areas where microsporidium does not occur in assessment of T. solenopsae as a long-term biological control agent. A major problem in field introductions is monitoring of microsporidian infections in the release sites. The present research compared methods of detection of microsporidiosis in populations of fire ants after experimental introductions. These techniques included observation of fresh smears under phase contrast optics, Giemsa and Chromotrope-based trichrome staining, and PCR. Success/failure diagnosis by each method were compared and statistically treated by a sign test. Examination of fresh smears under phase contrast optics is not efficient and can be excluded from the diagnostic procedure. The Trichrome stain enhances diagnosis and is preferable to the Giemsa stain previously used. PCR is useful in samples that test negative by the Trichrome stain, because spores represent only a part of the complicated life cycle of T. solenopsae, and failure of their visualization by light microscopy can cause false negative diagnoses. A new procedure is suggested to detect microsporidiosis in field populations of insects.
Key words: Microsporidia, staining methods, molecular detection, Thelohania, Solenopsis invictae, biological control
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