While COVID-19 swept the globe in 2020, the rabies virus continued its steady march through communities across Africa and Asia. This ancient disease, which has been possible to eliminate for a century, still wreaks devastation on those living at the margins of society. The development of an effective human vaccine in 1885 made it possible for those bitten by rabid dogs to avoid rabies infection; however, it did nothing to abate propagation of the virus through dog populations, which serve as the reservoir species. The ultimate solution to this intractable issue lies with the veterinary sector through sustained massive dog vaccination initiatives (Gibson et al., 2022). Recent examples of success and a coordinated global community under the United Against Rabies initiative are igniting new momentum for the global elimination of dog-transmitted rabies.
So as the world has become better at addressing public health disparities, why has rabies been left behind? The rabies virus is known for its unparalleled ability to evade detection by the host immune system; however, its deftness at avoiding the political spotlight for decades is perhaps even more fascinating. Unlike HIV, Ebola virus and SARS-CoV-2 which blaze through the human population like wildfire, the rabies virus burns more slowly in a companion species – dogs. The virus’s choice of reservoir species and how it spreads have significance in dodging prioritisation by both human and animal health sectors.
The [rabies] virus’s choice of reservoir species and how it spreads have significance in dodging prioritisation by both human and animal health sectors
Rabies has the highest case-fatality rate of any disease, approaching 100 percent, and kills hundreds of thousands of dogs each year, but these animals have no economic value to governments. The catastrophic impact of rinderpest on agricultural economies around the world galvanised governments and veterinary departments to unite in its global eradication.
Although the cost-effectiveness of dog rabies elimination has been well described (Fitzpatrick et al., 2016; Gibson et al., 2022; Shim et al., 2009), the economic gains fall between stools in existing political structures. Expenditure by veterinary services to control rabies pays off through reduced livestock losses, diminishing human healthcare costs and strengthening of the economy through prevented human deaths, but this is a complicated sell in the world of political campaigning. When pitched against the more tangible upswing of controlling production animal diseases such as foot and mouth disease, African swine fever and avian influenza, prioritisation of rabies has consistently failed to gain traction in veterinary ministries.
Paradoxically, while the idea of controlling rabies remains inconspicuous, the disease itself does not shy away from tabloid headlines. The uniquely violent mode of transmission, contorting the minds of once friendly dogs to seek out and bite people without inhibition, is traumatising and terrifying for those involved. Children are at greatest risk of rabies, due to their close contact with community dogs and poor awareness of the risks following a dog bite, and so public outrage understandably follows a spate of rabid dog encounters. But regardless of what action is or isn’t taken by governments, the natural epidemiology of rabies results in the apparent disappearance of the virus for long stretches of time.
Rabid dogs are inherently peppered through time by the long incubation period which begins following the infected bite from a rabid animal (Mancy et al., 2022). During this time the virus is undetectable, being slowly shuttled towards the brain from the bite location within neurones. Once in the brain, rabies only reveals itself for the short infectious period prior to death and many of these animals go unnoticed due to nondescript signs such as lethargy and paralysis. Months or years may therefore pass between dogs identified as rabid in any one community, creating the impression that rabies is there, but at the same time not there. This sporadic picture fails to generate any sustained public or political pressure for a comprehensive control strategy. The veil is only lifted once robust surveillance systems are established revealing the pervasive nature of the rabies virus and its significant impact across communities.
Once in the brain, rabies only reveals itself for the short infectious period prior to death and many of these animals go unnoticed due to nondescript signs
There is, however, reason for optimism. The occult persona of the rabies virus exposes a chink in its strategy. The virus remains below the radar of widespread public awareness by constantly teetering on the edge of decline. It is, in fact, far less transmissible than many other diseases, as measured by the reproductive number (the number of animals an infectious individual will typically infect in a susceptible population). This, in turn, determines how easy it is to eliminate the disease through mass vaccination.
The reproductive number of rabies is consistently reported as between 1.2 and 2, requiring only around 40 percent of dogs to be vaccinated to push the virus into a downward spiral towards elimination (Hampson et al., 2009). This low threshold makes rabies elimination low-hanging fruit, even at the recommended annual vaccination coverage of 70 percent to account for the death of vaccinated individuals between campaigns. The first reports of successful rabies elimination through mass dog vaccination date back over 100 years (Umeno and Doi, 1921), and have since been replicated at varying scales across the rabies-endemic world. The greatest example of this was the continental rabies control programme in Latin America launched in the 1980s, which vaccinated more than 50 million dogs annually at its peak (Freire de Carvalho et al., 2018). The challenge is now to replicate this success in African and Asian countries, where most human rabies deaths occur (Hampson et al., 2015).
[It] requir[es] only around 40 percent of dogs to be vaccinated to push the virus into a downward spiral towards elimination
For the past decade, veterinary organisations such as Mission Rabies have been working to develop effective strategies and tools to achieve dog rabies elimination at scale. Innovation in smartphone technology has enhanced the spatial management of dog vaccination teams, ensuring that pockets of population are not left unvaccinated and maximising the chances of elimination (Monroe et al., 2021). Exploration of existing and novel vaccination methods across diverse settings provides governments with data upon which to develop effective district and national strategies (Evans et al., 2019; Gibson et al., 2015, 2019; Mazeri et al., 2021; Sánchez-Soriano et al., 2019, 2020).
Development of education programmes has been shown to improve knowledge of rabies prevention in school children (Burdon Bailey et al., 2018) and such programmes have reached millions of children in India and Malawi (Gibson et al., 2018). In addition, intensification of rabies surveillance systems through central public reporting, active response and improved laboratory diagnostics have supported governments to generate the political will needed to mount a sustained offensive against the disease (Gibson et al., 2022; Yale et al., 2019).
Goa recently documented a tour de force in rabies control at the Indian state level through a seven-year campaign instigated by the government of Goa in partnership with Mission Rabies. In 2021 the state became the first in India to be declared a Rabies Controlled Area under Indian legislation and the programme was found to be highly cost-effective in the prevention of 121 deaths over a 10-year period (Gibson et al., 2022). While the Goa example is a fraction of what will ultimately be required, it provides a template from which to support other governments of South Asia to achieve their own success.
Today rabies is a disease of inequality, inflicting an abhorrent toll on those with least opportunity, agency and political influence in society
Today rabies is a disease of inequality, inflicting an abhorrent toll on those with least opportunity, agency and political influence in society. A person’s chances of survival following the bite of a rabid dog depends entirely on their financial and logistical ability to access rabies vaccine. This disparity is further compounded by higher densities of unvaccinated roaming dogs in underprivileged communities (Mazeri et al., 2019) and inequities in access to health education.
Our generation of veterinarians has an opportunity to redress this imbalance through a One Health perspective. The medical sector, experiencing the human cost of rabies, must lobby for a veterinary solution until the last victim of a rabid dog bite leaves their clinic, and veterinarians need to unite behind the biggest dog vaccination campaigns the world has ever seen. Just as smallpox eradication represented success for global human health and rinderpest eradication was a victory for animal health, global dog rabies elimination can be a historic triumph for One Health.