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United States Department of Agriculture

Agricultural Research Service

Title: Intra-Colony Transmission and the Discovery of a New Spore Type for Thelohania Solenopsae (Microsporidia: Thelohaniidae) in Red Imported Fire Ants (Hymenoptera: Formicidae)

Authors
item OI, DAVID
item BECNEL, JAMES
item Williams, David

Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 19, 2001
Publication Date: N/A

Interpretive Summary: Imported fire ants are serious pests throughout the southern U.S. and in parts of California. These ants are an invasive species, originally from South America, and in the U.S. there is a lack of natural enemies which may mediate its spread and impact. Recently a pathogen of imported fire ants was discovered in Florida. This pathogen, Thelohania solenopsae, is a microsporidian (protozoan) that infects the ovaries of fire ant queens, reduces her egg production, and causes her to die prematurely. Infections can be initiated by introducing live brood (mainly larvae and pupae) infected with T. solenopsae to uninfected colonies. The transfer of live, infected brood into colonies is a very tedious and inefficient method of spreading infections. To develop better methods of inoculation, scientists from the Center for Medical, Agricultural, and Veterinary Entomology in Gainesville, FL determined which immature ant stages are required for the infection of fire ant queens. Microscopic examination of infected brood revealed a new spore type in the life cycle of T. solenopsae in the pupae of fire ants. These findings may lead to the determination of an infective spore that can be formulated into an easily dispensed product that will aid the establishment and spread of this natural enemy of imported fire ants in the U.S.

Technical Abstract: Thelohania solenopsae is a microsporidian pathogen of imported fire ants. Transovarial transmission has been documented from infected queens, however the horizontal transmission pathway of T. solenopsae within a colony is unknown. Red imported fire ant, Solenopsis invicta, colonies can be infected by introducing live brood (mainly larvae and pupae) infected with T. solenopsae. Live, infected brood introduced into uninfected colonies were adopted and raised to adulthood instead of being executed by the recipient colony. Various combinations of infected larvae and pupae were introduced into red imported fire ant colonies to determine which stage(s) of brood result in infections. Introductions of infected larvae with uninfected pupae which eclose into adult worker caste fire ants resulted in an 80% infection rate of the inoculated colonies. Infections from introductions of infected pupae with uninfected larvae resulted in a 37.5% infection. Infections were also detected in 11.6 and 3.7% of the adult worker caste ants that eclosed from uninfected large larvae and pupae, respectively, that were held with infected adults workers. Microscopic examination of infected brood revealed binucleate sporoblasts and a new spore type of T. solenopsae in S. invicta pupae.

Last Modified: 9/29/2014
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