A species-specific enzyme-linked immunosorbent assay for Nosema furnacalis (Microspora: Nosematidae)

Detection of Thelohania solenopsae (Microsporidia: Thelohaniidae) in Solenopsis invicta (Hymenoptera: Formicidae) by multiplex PCR

Oligonucleotide primer pairs were designed to unique areas of the small subunit (16S) rRNA gene of Thelohania solenopsae and a region of the Gp-9 gene of Solenopsis invicta. Multiplex PCR resulted in sensitive and specific detection of T. solenopsae infection of S. invicta. The T. solenopsae-specific primer pair only amplified DNA from T. solenopsae and T. solenopsae-infected S. invicta. This primer pair did not produce any amplification products from DNA preparations from uninfected S. invicta, seven additional species of microsporidia (including Vairimorpha invictae), or Mattesia spp. The Gp-9-specific primers recognized and amplified DNA from Solenopsis xyloni, Solenopsis richteri, Solenopsis geminata, the invicta/richteri hybrid, and monogyne and polygyne S. invicta, but not from T. solenopsae, and, as such, served as a positive control verifying successful DNA preparation. Multiplex PCR detected T. solenopsae in worker fire ants infected with as few as 5000 spores. Furthermore, multiplex PCR detected T. solenopsae in all developmental stages of S. invicta. However, detection could be made more sensitive by using only the T. solenopsae-specific primer pair; ants infected with as few as 10 spores were able to be discerned. Multiplex PCR detection of T. solenopsae offers the advantages of a positive control, a single PCR amplification, detection of all developmental stages, and increased sensitivity and specificity compared with microscopy.

Physiological host specificity of microsporidia as an indicator of ecological host specificity

For most groups of biological control agents the relationship between laboratory (physiological) host range and the host range in the field (ecological host range) has not been explored empirically. The objective of our study was to investigate this relationship using the North America gypsy moth, Lymantria dispar, as a model nontarget host for microsporidia from native North American Lepidoptera. The gypsy moth, L. dispar, a native of Europe, has been established in North America for nearly 130 years and presumably exposed to many species of microsporidia from sympatric native Lepidoptera. Nevertheless, microsporidia have never been observed in North American populations of L. dispar. We conducted traditional laboratory feeding experiments using microsporidia from 20 lepidopteran host species and 1 coleopteran host species against L. dispar. Microsporidia from 18 native hosts infected L. dispar larvae. Although some of the infections were not typical of infections in the indigenous natural hosts, mature spores were produced in most of these infections. Horizontal transmission experiments, based on exposure of uninfected L. dispar larvae to infected L. dispar larvae, demonstrated that the microsporidia were far more host specific than the direct feeding experiments suggested. Of the three microsporidian biotypes that were horizontally transmitted between the nontarget L. dispar larvae, all were transmitted at very low levels. The results of our experiments provide additional evidence that the ecological host specificity of terrestrial microsporidia is much narrower than the physiological host specificity. Our studies establish the validity of using nonindigenous insect species with long-term data sets on natural enemies associated with them as a tool for testing hypotheses about host specificity.