By Rowenna Hoskin | Science Editor
With COVID-19 on the rampage, vaccinations are at the forefront of everyone’s minds. While scientists are working on a cure for COVID-19, the benefit of prevention of disease is obvious.
Many diseases – like Rabies, COVID-19, SARS and Ebola – originate in animals and are then passed onto human populations.
In the past, the only methods to reduce transmission between wildlife and humans was to reduce human contact with disease-harbouring species, or to cull the species.
There have been vaccination programs in the past, a classic example being Rabies: by vaccinating dogs and other carnivores, rabies was suppressed in those populations which reduced the risk of humans contracting rabies. This was a very successful program and virtually eliminated rabies in the US and Europe. Rabies still kills more than 55,000 people a year across Africa and Asia where the cost of vaccination projects are preventing a sufficient level of immunity.
The problem that arises with these programs, the reason why they are very expensive, is because of the rapid population turnover and large population sizes of species. This makes maintaining immunity within populations very difficult and expensive – fortunately another solution is now available.
Scientists have created vaccines that spread themselves; these self-spreading vaccines can be developed in two ways.
The convenient approach relies on applying the vaccine to the fur of the captured animals and releasing them back into the wild. When they return to their natural homes, the vaccine will spread as social grooming takes place. As the individuals groom each other they ingest the vaccine which magnifies the level of immunity that populations can reach. This process shows promise for reducing the threat of rabies transmitted from vampire bats.
The second approach is a bit more radical: it relies on inserting a small piece of the genome of the infectious disease agent into a benign virus that spreads through the animal population. As the transmissible vaccine spreads from animal to animal, it immunises them against the target infectious disease. Immunity will increase within the population and the threat to humans will be heavily reduced.
The technology to create self-disseminating vaccinations now exists and has already been taken to field trials. Currently experiments are focused on protecting wild rabbit populations from a viral haemorrhagic fever using this technology.
Scientists are now looking at developing prototypes for several human pathogens like Ebola and Lassa. This technology could be revolutionary in reducing the threat of disease that is transferred from animals to humans.
Another benefit to this technology is the fact that disease would be able to be controlled, meaning that extermination of wildlife species would no longer be necessary. Ecologically important disease reservoir species populations will be conserved which maintains a healthy interdependent environment.
There is still a lot of work left to do before this technology is widely implementable; field trials will be testing effectiveness and possible unexpected consequences of self-spreading vaccines.
Considering the money being spent on a cure for COVID-19, prevention is unarguably a better method than waiting until it is too late. Vaccines that prevent pathogen transmission to human populations from the start are certainly a better investment than their cures.
Science and Technology Rowenna Hoskin