Rabies is a deadly disease. Without vaccination, rabies is nearly 100% fatal once it develops. There have been two outbreaks of rabies in animals in Texas since 1988. One was caused by coyotes and dogs in south Texas, and the other was caused by a gray fox in west central Texas. Affecting 74 counties, these outbreaks killed thousands of potentially infected people, killed two humans, and claimed the lives of countless animals.
In 1994, Governor Ann Richards declared rabies a state health emergency. The Texas Department of State Health Services responded by initiating an oral rabies vaccination program to control the spread of rabies from these wild animals.
Since 1995, the program has distributed more than 53 million doses of rabies vaccine by hand or by air to 758,100 square miles (approximately 2 million square kilometers) in Texas. Rabies cases in dogs and coyotes went from 141 to zero by 2005, and rabies cases in foxes went from 101 to zero by 2014. By 2004, one canine rabies variant was effectively eliminated from Texas, and another variant was virtually suppressed.
We are researchers who began researching rabies in wild animals and oral vaccination in the 1980s. From providing a proof of concept using an oral vaccine in raccoons to being one of the first companies to use a new rabies vaccine in the 1990s, we have been at the forefront of efforts to contain this deadly virus. I was there.
Decades of vaccine research have resulted in one of Texas’ most successful public health projects. And we hope this can provide a roadmap for mass vaccination of wildlife to prevent future outbreaks.
Development of oral rabies vaccine
The Texas Oral Rabies Vaccination Program has benefited greatly from the work of multiple researchers over the past several decades.
The mid-20th century saw some major advances in rabies control. George Baer, a virologist and veterinarian at the U.S. Centers for Disease Control and Prevention, said other efforts to prevent and control rabies in wild animals have failed after efforts to poison or trap infected animals failed. recognized the need for a strategy. His and his colleagues’ research in the 1960s led to the concept of an oral rabies vaccine. Oral vaccination of wild animals can help control infections at the source, but was previously thought to be logistically unfeasible given the wide range of animals targeted.
By the late 1970s, European researchers began the first field trials of giving oral rabies vaccines to foxes. The vaccine was packaged in small plastic containers and placed inside food such as chicken heads. More than 50,000 of these vaccine-containing baits were distributed to fox habitats in forests and fields over a four-year period.
Canadian researchers have also begun a similar field trial in Ontario. In the 1980s, an average of 235 rabid foxes were reported annually in the region. Bait containing oral rabies vaccine was dropped annually from 1989 to 1995, successfully eliminating rabid fox species from the entire area.
Recombinant oral rabies vaccine
The first generation of these vaccines used live viruses that were modified so that they did not cause severe disease. Although the original rabies vaccines were effective and generally safe, they required storage at low temperatures and carried the rare risk of causing rabies in animals.
In the early 1980s, scientists developed a recombinant rabies vaccine that used another virus to express the genes of the rabies virus. A collaboration between nonprofit agencies, the U.S. government, and the pharmaceutical industry has led to the development of a recombinant virus vaccine that does not cause rabies and produces a rapid immune response against it.
In 1984, preliminary studies in laboratory animals demonstrated the possibility of using oral recombinant vaccines to vaccinate animals. However, the concept of using genetically modified organisms was still in its infancy, both among scientists and the general public. While the vaccine was safe and effective in captive raccoons and foxes, big questions loomed over how it would affect other species if released into the environment.
After years of work to refine the vaccine’s design and test its safety in several non-human species, Europe’s first clinical trial was conducted at a military base in Belgium. The vaccine was approved in 1995 to control rabies in foxes in Luxembourg and France, with data supporting its safe and effective control of wild animals.
A similar study of an oral recombinant rabies vaccine was conducted in the United States. Initial testing began in his 1990 on Parramore Island off the coast of Virginia, and after a year of intensive monitoring, no significant adverse effects on the environment or wildlife species were found. A second year of research conducted on the mainland near Williamsport, Pennsylvania, had similarly positive results.
The vaccine was approved for use in raccoons in 1997 after it successfully controlled rabies in raccoons in trials in several other states on the East Coast.
In 1998, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service and the U.S. Fish and Wildlife Service expanded existing oral wildlife vaccination projects to strategically important states to prevent the spread of certain rabies viruses and to expand interstate projects. Received funds to adjust. .
Results in Texas
Oral recombinant vaccines are currently distributed primarily by hand in Texas, with approximately 75 separate helicopter flights a year.
The Texas Department of State Health Services Rabies Laboratory has partnered with the CDC to establish a regional rabies virus reference laboratory. One of us was hired to be responsible for both vaccine distribution in the field and the development of molecular typing tools to identify different types of rabies virus variants in the lab. . These techniques have allowed us to determine when and where different rabies virus variants are emerging.
Our lab is also the first agency outside of the CDC to help test specimens for rabies virus variants in other U.S. states and countries. These techniques have helped researchers monitor where rabies epidemics are advancing or receding due to wildlife vaccination and new forms of spread.
With the ever-present threat of emerging and re-emerging infectious diseases such as COVID-19 and influenza, the prospect of mass vaccination of wildlife could be one way to combat future pandemics. There is sex. Although there are many challenges ahead of us, we have hope that mass vaccination of wildlife may one day be available to reduce or eliminate infectious diseases such as rabies.
This article is republished from The Conversation, a nonprofit, independent news organization that provides facts and trusted analysis to help you make sense of our complex world. Authors: Rodney E. Rohde, Texas State University, Charles Rupprecht, Auburn University
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Rodney E. Rohde has received funding from the American College of Clinical Pathologists, the American Society of Clinical Laboratory Sciences, the U.S. Department of Labor (OSHA), and other public and private organizations/foundations. Rohde is affiliated with ASCP, ASCLS, and ASM and serves on several scientific advisory boards.
Charles E. Rupprecht consults for academic, government, industry, and NGO organizations worldwide. He receives funding from academic, government, industry, and NGO sources.
