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Correlation of colony social behavior and infection with Thelohania solenopsae (Phylum Microspora) in Red Imported Fire Ants (RIFA) in Texas

Elizabeth A. Ashbaugh; Forrest L Mitchell, PhD; Kathleen S. Logan; Karen F. Snowden, DVM, PhD

Objective-To determine the colony social status for polygyne and monogyne archived RIFA and correlate this information with parasite infection status.  

Study Population-99 archived fire ant colony samples from 60 fire ant-infested Texas counties.

Procedure-Samples were previously evaluated for infection with T. solenopsae.  Genomic DNA was isolated using an ammonium acetate-isopropanol extraction method. PCR amplification of the Gp-9 alleles was carried out, and the amplicons were separated on 1.5% agarose gels and visualized with ethidium bromide staining.  Polygyne and monogyne genotypes for each sample were geographically recorded and correlated with parasite status.

Results-Polygyne colonies had a higher parasite infection level with 30 of 62 colonies (48%) identified as parasite positive while monogyne colonies showed a 14% (5/37) parasite infection rate.  Our molecular data showing high parasite prevalence in polygyne colonies supports previous field observations that suggested that polygyne colonies were more frequently infected with T. solenopsae than monogyne ant colonies.  Thus far, the geographic distribution of polygyne/monogyne colony types does not appear to correlate with the geographic distribution of the parasite.

Conclusion-Since polygyne and monogyne colony types have differing behavioral characteristics and colony densities it is crucial to understand their geographic distribution.  Additionally, it is important to understand parasite infection rates and potential infectivity and transmission.  This knowledge of host-parasite relationships is vital in evaluating the potential of T. solenopsae as a biological control agent against the Red Imported Fire Ant.