Positive-Strand RNA Viruses Infecting the Red Imported Fire Ant,Solenopsis invicta

Abstract

The imported fire ants,Solenopsis invictaandS. richteriwere introduced into the USA between 1918 and 1945. Since that time, they have expanded their USA range to include some 138 million hectares. Their introduction has had significant economic consequences with costs associated with damage and control efforts estimated at 6 billion dollars annually in the USA. The general consensus of entomologists and myrmecologists is that permanent, sustainable control of these ants in the USA will likely depend on self-sustaining biological control agents. A metagenomics approach successfully resulted in discovery of three viruses infectingS. invicta.Solenopsis invicta virus 1(SINV-1), SINV-2, and SINV-3 are all positive, single-stranded RNA viruses and represent the first viral discoveries in any ant species. Molecular characterization, host relationships, and potential development and use of SINV-1, SINV-2, and SINV-3 as biopesticides are discussed.

Ant Interactions with Soil Organisms and Associated Semiochemicals

“…The first ant viruses were identified using a metagenomic approach, specifically for the fire ant, Solenopsis invicta. Three RNA viruses have been isolated and characterized (Valles 2012). The first two, SINV-1 and SINV-2 are found in all developmental stages, but only chronic asymptomatic infections have been observed, except that SINV-1 sometimes becomes pathogenic if colonies are stressed, e.g., dug up and brought to the lab.…”

Solenopsis invictaVirus (Sinv-1) Infection and Insecticide Interactions in the Red Imported Fire Ant (Hymenoptera: Formicidae)

“…The red imported fire ant (Solenopsis invicta Buren; Hymenoptera: Formicidae) has aggressively invaded ~138 million ha in the USA and causes over $6 billion in damage and control efforts annually (Valles 2011). Myriad research studies have been conducted to discover safe biological control agents to manage these invasive pests (Valles et al 2004;Milks et al 2008;Oi et al 2009;Yang et al 2009;Wang et al 2010;Callcott et al 2011;Porter et al 2011;Tufts et al 2011).…”

“…ascoviruses) (Stasiak et al 2005). The Solenopsis invicta virus (SINV-1) is a positive sense, single-stranded RNA virus, which can only infect the genus Solenopsis at all stages of development, and is verticallytransmitted within a colony (Valles et al 2004;Valles 2012).…”

“…Additionally, different bacteria have been found in the gut of S. invicta (Gunawan et al 2008;Tufts & Bextine 2009) which may work in combination with SINV to provide protection against toxic substances (Lacey et al 2001;Hedges et al 2008;Roossinck 2011). ssRNA viruses may also impart protection to hosts by integrating portions of viral RNA into the host's genome (Valles 2011) which has been reported for SINV-1(TX5) (Tufts et al 2010), although this phenomenon may not be universal (Valles & Bextine 2011).…”

“…Future work on SINVs for biological control should investigate the broader gene expressions linked to immunity and toxicity in various metabolic pathways. SINV-3, which is ubiquitous in all tissues and at greater titers, may be more effective at causing mortality, unlike SINV-1 which produces chronic, asymptomatic infections which only manifest under certain environmental stressors (Valles 2011). Additional research on virus/ant host interactions is urgently needed to fully elucidate their potential as biological control agents for S. invicta populations.…”