D3043: Larval honey bee resilience to IAPV is accompanied by delayed development

Israeli acute paralysis virus (IAPV) is an emerging honey bee virus that has been associated with large-scale honey bee (Apis mellifera) colony losses and is marked by paralysis and death in infected adults. However, despite this observed virulence and pathogenicity in adults and susceptibility of pupae, the effect of IAPV infection in larval bees is understudied, hampering our ability to fully understand its dynamics. To address this, we experimentally provisioned larvae with diet containing a concentrated lethal dose of IAPV every day throughout the course of their development until the prepupal stage. The time to three specific developmental stages (white-eyed pupae, red-eyed pupae, and adults) was tracked in addition to survivorship. Surprisingly, despite the virus’ rapid lethality to adult workers, inoculation with IAPV does not have a significant effect on larval mortality. Instead, larval exposure to IAPV manifests as a significant delay in larval development, after which most infected individuals arrest development at the white-eyed pupa stage. Quantitative PCR was used to determine the level of infection in larval tissue. The delayed development of infected bees may have repercussions for IAPV’s disease dynamics within the colony. Capped brood which do not emerge on time are often culled and cannibalized—a method of transmission for other honey bee viruses such as deformed wing virus, and how viral levels may remain stable in a colony without the presence of a vector such as Varroa destructor.