Submitted to: Virology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/21/2014
Publication Date: 5/1/2014
Citation: Valles, S.M., Porter, S.D., Firth, A.E. 2014. Solenopsis invicta virus 3: pathogenesis and stage specificity in red imported fire ants. Virology. 460-461(2014):66-71. Interpretive Summary: The red imported fire ant was introduced into the United States in the 1930s and currently infests about 300 million acres. It is estimated to cause $3-6 billion in annual economic losses to livestock and agricultural production and poses a serious threat to human health. Biological control is widely considered the most sustainable method of controlling the fire ant over its entire range. The virus, Solenopsis invicta virus 3, discovered by USDA-ARS scientists at the Center for Medical, Agricultural and Veterinary Entomology (CMAVE, Gainesville, FL), has been shown to be a promising potential biocontrol agent for these ants. However, characterization of this virus is crucial to its development as a microbial insecticide. Scientists at Center for Medical, Agricultural and Veterinary Entomology (CMAVE, Gainesville, FL) and the University of Cambridge, Cambridge, United Kingdom have completed the first studies to characterize the unique stage dependency of the virus. Their research findings describe the mechanism of infection in fire ant colonies and that the virus may alter worker ant behavior. This information will advance our understanding of this and related viruses, and provide information necessary to its development as a microbial insecticide.
Technical Abstract: Small Solenopsis invicta colonies were exposed to purified preparations of Solenopsis invicta virus 3 (SINV-3) to investigate virus pathogenesis at the colony level. Time course experiments revealed an infection exhibiting specificity for the adult stage (workers). SINV-3 genome and a capsid protein were present in increasing quantities as the infection progressed in worker ants. Northern blot analysis revealed two bands in RNA preparations from worker ants infected with SINV-3 corresponding to the genomic and sub-genomic species. Conversely, larval RNA preparations from SINV-3-infected colonies showed a near-complete absence of SINV-3 genome or sub-genome. This study provides further support that SINV-3 is the etiological agent causing mortality among S. invicta colonies in the laboratory. Results also satisfy Koch’s postulates for SINV-3. SINV-3 replication appears to be limited to the adult stage. We propose that SINV-3 infection somehow alters worker ant behavior, which may prevent them from acquiring or distributing solid food to the larvae. Consequently, larval mortality occurs as a result of starvation or neglect by the worker caste. Worker mortality and decreased queen fecundity occur later in the infection process.