Cane Toad Influenza-like Virus

The cane toad (Rhinella marina) is a large, terrestrial true toad native to South and mainland Central America. The cane toad has poison glands that secrete bufotoxin, which is fatal to many Australian predators, and population declines in toad-eating animals have occurred since the toads’ introduction in 1935.

Because of its voracious appetite, the cane toad has been introduced to many regions of the Pacific and the Caribbean islands as a method of agricultural pest control. At the time of introduction in Australia it was erroneously thought that the cane toad would be an effective predator for the cane beetle (Dermolepida albohirtum), which is a serious pest sugar cane[1].

The cane toads are notoriously successful invaders. Just 101 individual toads were introduced in Australia in 1935, but now millions of these poisonous cane toads cover an area larger than 1.2 million km² with severe adverse effects on native fauna.

The cane toad is poisonous, but scientists were curious if this species also harbours potentially deadly viruses. They identified two influenza-like viruses of amphibians that fell as sister lineages to the – only recently discovered - Influenza D Virus: cane toad influenza-like virus and the ornate chorus frog influenza-like virus, in the cane toad (Rhinella marina) and ornate chorus frog (Microhyla fissipes), respectively[2].

Despite their divergent phylogenetic positions, these viruses retained segment conservation and splicing consistent with transcriptional regulation in influenza D viruses, and were detected in respiratory tissues. These data suggest that influenza viruses have been associated with vertebrates for their entire evolutionary history.

The research further suggests that divergent members of this virus family may infect a wide range of animal hosts. Overall, despite finding these viruses in non-mammalian hosts, the viral structure is highly consistent with other influenza viruses, strongly supporting the inclusion into these viral genera.

This doesn't bode well for the future because more and more novel members of the Orthomyxoviridae are discovered, potentially posing a risk for cross species mutations.

[1] Easteal: The history of introductions of Bufo marinus (Amphibia: Anura): a natural experiment in evolution in Biological Journal of the Linnean Society - 2008
[2] Parry et al: Divergent influenza-like viruses of amphibians and fish support 2 an ancient evolutionary association in bioRxiv – 2020