Investigating the honey bee virus dynamics in fire ant (Solenopsis invicta Buren) colonies

The red imported fire ant, Solenopsis invicta Buren, is frequently found around the apiaries in the southern United States. Despite their role in consuming dead honey bees, few studies have focused on the potential of interspecies virus transmission from honey bees to fire ants. Here, we report a series of experiments to test the possibility of foodborne virus transmission in fire ant colonies as well as the dynamics of viruses within their colonies. We used Israeli Acute Paralysis Virus (IAPV) as an experimental pathogen, because it is relevant to honey bee heath, but is not omnipresent. Fire ant colonies were established in the laboratory and were fed once with IAPV-infected worker bee pupae. We then monitored both vertical and horizontal virus transmission routes within the colonies. In a separate experiment, we monitored virus circulation within colonies over a period of four months. Our findings revealed that IAPV transmits horizontally among all the developmental stages in ant colonies. The virus can also be transmitted to queens through trophallaxis, and subsequently be passed vertically from infected queen to her eggs. Based on our data, fire ants can acquire IAPV from honey bees through contaminated resources, and the virus spreads rapidly within the colony due to high interaction among colony members. Notably, significant viral loads persisted even after four months. Thus, our study indicate that fire ants can act as a virus reservoir, posing a potential threat to the health of bee pollinators.