An oral vaccine that may protect chimpanzees against the Ebola virus is presented in an initial study in Scientific Reports this week. The authors suggest that oral vaccination may hold promise as a safe and efficient way to protect endangered species against pathogenic threats.
Approximately one third of the world’s gorillas have been killed by Ebola and although a number of disease threats to apes are preventable using vaccines, traditional delivery using darts is challenging for use on animals that live at low density in thick, tropical forests.
Peter Walsh and colleagues conducted a trial using the vaccine filorab1 against the Ebola virus in ten chimpanzees in captivity. Six of the chimpanzees received the vaccine orally under sedation, while the other four received the vaccine via an intramuscular injection. Levels of antibodies in the blood against the Ebola virus were then monitored up to 28 days after vaccination. The authors found that levels of antibodies against the Ebola virus in the orally vaccinated chimpanzees rose during the trial, with rates of increase very similar to those seen in the chimpanzees that had received the vaccine via injection. However, none of the chimpanzees were challenged with Ebola after vaccination and future studies to further establish the protective effect of oral delivery are needed.
The authors argue that the immune response produced from a single dose of the vaccine, delivered orally, may be an advantage in the field vaccination of wild apes that are difficult to locate in dense forest. They note that field trials involving wild apes will be needed and further work on oral-bait prototypes and to stabilize the vaccine against heat for viability under hot forest conditions will be required.