Airdropping vaccines to eradicate canine rabies in Texas – the decades of research behind its success

Rabies is a fatal disease. Without vaccination there is a risk of rabies infection 100% fatal as soon as someone develops symptoms. Texas has experienced two epidemics of rabies in animals since 1988: one with coyotes and dogs in south Texas and the other with gray foxes in west central Texas. These outbreaks, which affected 74 counties, resulted in thousands of people who could have been exposed to the virus, two human deaths, and countless animal lives lost.

In 1994, Governor Ann Richards declared rabies a state health emergency. The Texas Department of State Health Services responded by introducing the Oral rabies vaccination program to control the spread of these rabies outbreaks in wild animals.

The program has been distributed since 1995 over 53 million doses of rabies vaccine across 758,100 square miles(almost 2 million square kilometers) in Texas by hand or plane. The number of rabies cases in dogs and coyotes increased from 141 to 0 by 2005, and the number of rabies cases in foxes increased from 101 to 0 by 2014. By 2004, there was a variant of rabies in dogs effectively eliminated from Texasand another variant has been largely controlled.

We are researchers who have started Study wildlife rabies And oral vaccination in the 1980s. From providing a proof of concept for the use of oral vaccines in raccoons to being among the first to use new rabies vaccines in the 1990s, we were at the very beginning of the effort to contain this deadly virus.

Decades of vaccine research led to one of the most successful public health projects in Texas. And we hope it could provide a roadmap for deploying mass vaccinations in wildlife to prevent future outbreaks.

Development of the oral rabies vaccine

The Texas Oral Rabies Vaccination Program has benefited greatly from the work of several researchers over the past few decades.

There were several in the mid-20th century significant developments in combating rabies. Virologists and veterinarians fail in attempts to poison or capture infected animals George Bearat the U.S. Centers for Disease Control and Prevention recognized the need for a different strategy to prevent and control rabies in wildlife. His and his colleagues' work in the 1960s led to the concept of oral rabies vaccination. While oral vaccination of wild animals would help combat the infection at its source, it was previously considered logistically unfeasible due to the large range of target animals.

European researchers started doing this in the late 1970s first field Try Orally vaccinate foxes against rabies. Small plastic containers were filled with vaccines and inserted into bait like chicken heads. Over a four-year period, over 50,000 of these vaccine-laden baits were distributed in fox habitats in forests and fields.

Researchers in Canada also began similar field trials in Ontario. In the 1980s, an average of 235 rabid foxes per year were reported in the area. From 1989 to 1995, oral rabies vaccine baits were used annually, successfully eradicating the fox variant of rabies from the entire area.

Recombinant oral rabies vaccine

The first generation of it Vaccinations used live viruses modified to prevent serious illness. Although effective and generally safe, the original rabies vaccines required storage at cool temperatures and carried the rare risk of causing rabies in animals.

In the early 1980s, scientists developed recombinant rabies vaccines that use a separate virus to express the rabies virus genes. A collaboration between a non-profit institute, the US government and the pharmaceutical industry led to the development of a recombinant virus Vaccine which produced a rapid immune response against rabies without the possibility of causing rabies.

In 1984 Preparatory work in the laboratory Animals showed promise of using an oral form of the recombinant vaccine to vaccinate animals. However, the concept of using genetically modified organisms was still in its infancy among scientists and the general public. While the vaccine was safe and effective in captive raccoons and foxes, there were big questions about what impact it might have on other species once it entered the environment.

After years of work improving the design of the vaccine and testing its safety in multiple non-human species, the first European Attempt took place at a military base in Belgium. Because there was data showing that the vaccine could safely and effectively control wildlife in Luxembourg and France, it was approved in 1995 to combat fox rabies.

Similar studies of the oral recombinant rabies vaccine have been conducted in the United States. The first trial began in 1990 Parramore Island off the coast of Virginiaand a year of intensive monitoring revealed no significant negative impacts on the environment or wildlife species. A second year-long study on the mainland near Williamsport, Pennsylvaniahad similarly positive results.

After the vaccine was successfully used in tests to combat raccoon rabies in severalother east Coastal statesIn 1997 it was approved for use on raccoons.

In 1998, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service and the U.S. Fish and Wildlife Service received funding Expansion of existing oral wildlife vaccination Projects in states of strategic importance, prevent the spread of specific rabies viruses and coordinate intergovernmental projects.

Results in Texas

In Texas, the oral recombinant vaccine is now distributed primarily by hand and through about 75 separate helicopter flights per year.

The Texas Department of State Health Services rabies lab worked with the CDC to develop this Regional reference typing laboratory for rabies viruses. One of us was recruited to distribute and develop the vaccine locally Molecular typing tools to distinguish between different types of rabies virus variants in the laboratory. Using these techniques, we were able to determine where different variants of the rabies virus were occurring at any point in time.

The Texas Oral Rabies Vaccination Program continues to monitor and control rabies cases in the state.

Our lab was also the first in the country outside of the CDC to help other U.S. states and countries test their samples for rabies virus variants. These techniques helped researchers monitor where rabies epidemics persisted or declined due to wildlife vaccinations new forms of distribution.

Given the constant threat of re-emerging infectious diseases such as COVID-19 and influenza, the prospect of mass vaccination of wildlife could be a way to combat future pandemics. Although there is still a lot of work ahead of us, we hope that one day we will have the opportunity to do so through mass vaccination of wild animals to reduce or eliminate infectious diseases such as rabies.

Rodney E. Rohde is Regents' Professor and Chair of Medical Laboratory Science at Texas State University. Charles Rupprecht is an associate professor of veterinary medicine at Auburn University. This article was republished by The conversation under a Creative Commons License. Read that Original article.