Published July 29, 2016
Leptospirosis is a bacterial disease spread through the urine of infected rats, wildlife, and canines. Although it is treatable with...
— William Wilberforce
Anyone who has encountered a rabid animal or has seen the film “Old Yeller” for that matter knows that rabies is a serious, often deadly infection to avoid, whether in the wild or in our own pets. Though many veterinarians believe that rabies vaccines in general offer a lifetime of protection for pets and do not need to be repeated, the rabies vaccine is one that is encouraged, and state or county governments usually mandate for all pets to receive annually, or every three years, depending on the type of rabies vaccine used. Although some states allow medical exemptions for rabies vaccination of pets, because the infection itself is nearly always fatal to humans and animals without immediate treatment, laws are fairly strict.
U.S. measures to control rabies in wildlife populations have turned to dropping baited vaccine into woodlands, in hopes of attracting wildlife to eat the baited treats and the vaccine along with them. The oral vaccines used in dropped-bait programs are live, attenuated (weakened), genetically modified vaccine products.1 This has become a fairly widespread practice since it was first introduced in Switzerland in the late 1970s.2 “Bait dropping” has been used in Canada since 1985 and in the U.S. since 19953 and is generally accepted without question.
But is it effective? Is it necessary? And especially, is it safe for pets or children who might encounter the attractive bait and play with or even eat it?
Rabies is a viral infection most commonly spread to humans or pets via saliva from the bite of an infected wild animal, usually raccoons, skunks, bats or foxes in the U.S., though it is also encountered in coyotes and groundhogs. Smaller mammals including rabbits and most rodents including rats and mice, squirrels, hamsters, guinea pigs, and chipmunks, do not generally carry rabies and have not been known to infect humans in this country.4
Hawaii is the only state, and Australia and Antarctica the only other places in the world that are reportedly rabies free. Globally, more than 50,000 humans and millions of animals still die from rabies every year.5
The virus affects the brain, beginning with general symptoms of illness such as fever and discomfort, but progressing to more specific signs including insomnia, confusion, partial paralysis, hallucinations, agitation, increased salivation and difficulty swallowing, and hydrophobia, or fear of water. Once these more severe symptoms occur, whether in humans or pets, death almost always occurs within days.
Even with immediate treatment, very few victims survive.6 There are only three known cases in the U.S. of (human) patients surviving without the standard urgent therapy,7 which involves thoroughly washing the wound, flooding it with rabies immunoglobulin and following up with a series of injections of the immunoglobulin and rabies vaccine.8
There are reports that some residents of remote Peruvian villages, where infected vampire bats are common, who have been bitten and survived, as evidenced by the presence of antibodies against rabies in their blood. However, it isn’t clear whether they actually got seriously ill with common symptoms of the infection.9
With such a backstory, it is easy to understand why rabies vaccination programs, both for pets and wildlife, are so widely accepted and why the infection is so wildly feared. To keep that fear in perspective, however, it is important to keep in mind that even at 50,000 cases worldwide, infection with rabies is still extremely rare, occurring in only 34 people in the U.S. since 2003, and in only three in 2013.10
Nowhere is it suggested that the rabies vaccine offers total protection against this extremely serious disease, which is essentially always fatal in animals. The most said about the vaccine’s effectiveness is that it may provide some protection, but a bite from a rabid animal always requires rapid medical attention to evaluate the type of exposure and the consequential degree of follow-up care needed.
Such is the level of concern about the infection that any pet that has been bitten or scratched by a wild animal not available for testing is considered to have been exposed to rabies, and is treated accordingly. If mandatory vaccination records are not up-to-date, the pet will be subjected to a long quarantine period (six months) or, in most cases, will be euthanized. Even if the pet has been vaccinated as required by law, it will be subjected to rigorous treatment including immediate revaccination, isolation and a 45-day observation period to account for the possibility of “overwhelming viral challenge, incomplete vaccine efficacy, improper vaccine administration, variable host immunocompetence, and immune-mediated fatality.”11
U.S. laws mandate that pet dogs, cats and ferrets be vaccinated once at three to four months of age, again a year later, and then either annually or every three years, depending on type of vaccine used. Multiple sources indicate that the three-year rabies vaccine is actually the same dose and active agent as the one-year vaccine; the difference is solely in the manufacturers’ labeling, which will indicate whether that specific brand and formulation has been studied over time and found to retain its immunologic activity for at least three years.12
In a series of interviews with veterinarian Dr. Karen Becker, veterinary vaccinations expert Dr. Ronald Schultz noted that a three-year rabies shot may give rabies protection that in fact persists beyond three years. He emphasized that the schedule he recommends for the rabies vaccine for pets is out of respect for the law and not because he believes the vaccine is immunologically necessary every three years.13
By far the biggest carrier group of rabies in the U.S. currently is wildlife, which accounts for 92% of rabies cases according to the most recent CDC surveillance data available.14 15 In those reports, raccoons continued to be the most frequently reported rabid species encountered in the U.S., followed by skunks, bats and foxes.
Until relatively recently, control of rabid wildlife depended on such measures as education of the public and medical personnel, avoiding exposure, post-exposure preventive treatment and “selective population reduction” of animal species at high risk of infection.16
The “Vaccine Drop” is a relative newcomer in the war against rabies, but in 2010, the U.S. Department of Agriculture estimated that it distributes approximately 6.5 million baits per year in selected areas, specifically to contain the spread of raccoon rabies from the eastern states.17 Vaccine drops also target coyote and fox strains in other areas of the country.
According to public health officials,18 there is no danger to people or pets from accidental contact with or ingestion of the dropped live genetically engineered rabies vaccine, but the authorizing agencies caution that the bait should not be touched. However, they caution that, if a child does come in contact with it, or eat any of it, the product should be carefully removed and wrapped up, the child’s hands should be thoroughly washed, and health authorities should be contacted.
1 Merial, Material Safety Data Sheet. RABORAL V-RG® with Bait. Apr. 15, 2005.
2 Mähl P, et al. Twenty Year Experience of the Oral Rabies Vaccine SAG2 in Wildlife: A Global Review. Veterinary Research Aug. 19, 2014.
3 United States Department of Agriculture (USDA). Oral Rabies Vaccine Information. USDA Animal and Plant Health Inspection Service June 17, 2015.
4 Centers for Disease Control and Prevention (CDC). Rabies. CDC Fact Sheet July 2, 2015.
5 The American Society for the Prevention of Cruelty to Animals (ASPCA). Pet Care: Rabies. 2015.
6 Centers for Disease Control and Prevention (CDC). Rabies. CDC Fact Sheet July 2, 2015.
7 Carollo K. California Girl Only Third in U.S. to Survive Rabies Without Vaccine. ABC News June 14, 2011.
8 Dyer JL, et al. Rabies Surveillance in the United States, 2013. Vet Med Today: Public Veterinary Medicine (JAVMA) Nov. 15, 2014.
9 Fox M. Can People Survive Rabies? Some Vampire Bat Victims May Have. NBC News Aug. 1, 2012.
10 Dyer JL, et al. Rabies Surveillance in the United States, 2013. Vet Med Today: Public Veterinary Medicine (JAVMA) Nov. 15, 2014.
11 Centers for Disease Control and Prevention (CDC). Compendium of Animal Rabies Prevention and Control, 2011: National Association of State Public Health Veterinarians, Inc. (NASPHV). CDC Nov. 4, 2011.
12 EnlightenMe.com. Is the 3 Year Rabies Vaccine for Pets Different From the Yearly Vaccine? DexMedia 2015.
13 Becker, K. Does Your Pet Really Need That Rabies Shot? Mercola.com June 21, 2011.
14 Centers for Disease Control and Prevention (CDC). Rabies Surveillance Data in the United States. CDC Fact Sheet Nov. 15, 2011.
15 Dyer JL, et al. Rabies Surveillance in the United States, 2013. Vet Med Today: Public Veterinary Medicine (JAVMA) Nov. 15, 2014.
16 Centers for Disease Control and Prevention (CDC). Compendium of Animal Rabies Prevention and Control, 2011: National Association of State Public Health Veterinarians, Inc. (NASPHV). CDC Nov. 4, 2011.
17 U.S. Department of Agriculture, Wildlife Services. Preventing the Spread of Raccoon Rabies. August 2015.
18 See Reference #1.