Researchers just unveiled a new vaccine that can safeguard farmed crocodiles from the debilitating effects of the West Nile virus. This mosquito-borne zoonotic virus poses a threat to various species, including birds, horses, humans, and reptiles. In saltwater crocodiles (Crocodylus porosus), the virus induces skin lesions that ultimately devalue the animals used for leather production.

Roy Hall, a researcher at the University of Queensland, Australia, and his team have successfully formulated a vaccine that demonstrates the capability to shield saltwater crocodiles from the West Nile virus. Given the similarity of skin lesions in other crocodile species, such as alligators and Nile crocodiles, it is anticipated that the vaccine will also be applicable to them too.

“Infection with West Nile virus often causes lesions in the skin that reduce the value of the hide for the production of quality leather goods,” Hall told ZME Science. “In particularly bad years, up to 30 % of the farmed crocodiles develop lesions due to infection with this mosquito-borne virus, costing the Australian industry tens of millions of dollars.”

A big industry

The international trade of crocodilians is strictly regulated by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Countries must demonstrate that the industry does not pose a threat to the species’ survival. This involves monitoring the wild population and implementing regulations on traded products, such as utilizing numbered tags on all animals.

Unlike many other animals, crocodiles are primarily farmed for their skins, with meat serving as a by-product. Consequently, meticulous care is taken during the rearing process to minimize damage to the skin, both from surface-level factors and social interactions. As crocodiles grow larger, they are kept at a distance from each other to prevent injuries.

The West Nile virus poses a significant economic threat to the crocodile farming industry due to the skin lesions it causes. While vaccines for veterinary use in horses exist, and one is used off-label for alligators in the US, there are no published reports on the vaccine’s efficacy in American alligators. Furthermore, no vaccine is currently available for crocodiles in Australia, Asia, and Africa.

To address this pressing issue, Hall and his team modified a harmless virus found in mosquitoes called the Binjari virus. Through this modification, they created a hybrid virus that presents the proteins of the West Nile virus on its surface. This hybrid virus closely resembles the West Nile virus, but animals immunized with the vaccine develop robust protective immunity against it, effectively preventing the disease in crocodiles.

“Given this potential role as an amplifying host, protecting farmed saltwater crocodiles from the West Nile infection would not only reduce industry losses but also serve, by extension, to protect humans and other animal hosts,” the researchers wrote in their paper.

While significant progress has been made, there is still work to be done. Hall’s team is collaborating with an Australian veterinary vaccine company, Treidlia BioVet, to develop a commercial version of the vaccine for use in the crocodile industry. Furthermore, they have secured funding from the Council to collaborate with the Centre for Crocodile Research, with the goal of assessing the long-term performance of the vaccine and eventually obtaining regulatory approval.

The study was published in the journal NPJ Vaccines.