AVMA Collections: Rabies summary

 


Single-topic compilations of the information shaping our profession

Updated December 2010

While the World Health Organization reports that rabies is still a significant public health problem in many countries of Asia and Africa, according to the Centers for Disease Control and Prevention (CDC) modern day rabies prophylaxis in the United States has proven nearly 100% successful. The number of rabies-related human deaths in the United States has declined from more than 100 annually at the beginning of the 20th century to one or two per year in the 1990s. Although human rabies deaths are rare, the estimated public health costs associated with disease detection, prevention, and control in the United States have risen, exceeding $300 million annually.

Veterinarians have a vital role in the continued success of rabies vaccination programs and in ongoing research to find more effective and efficient vaccination methods. The articles in this collection have been selected to present an overview of current findings in veterinary medicine related to best practices in rabies prevention and control.

In "Epidemiology/surveillance" results of epidemiologic studies of dogs, cats, bats, and skunks are provided. Rabies in dogs and cats was far more likely in unvaccinated, owned animals, suggesting a need for owner education. As the authors of "Rabies in vaccinated dogs and cats in the United States, 1997-2001" remind us, however, rabies may still occur in previously vaccinated dogs and cats. Educational efforts aimed at wildlife rehabilitators are recommended by the authors of "Survey of wildlife rehabilitators regarding rabies vector species," based upon survey findings that revealed an inconsistent knowledge of rabies in this group.

"Rabies preexposure vaccination among veterinarians and at-risk staff," the first article in the "Zoonosis management" section, contains results of an examination of factors affecting use of preexposure vaccination, such as cost and risk of adverse events. Authors of two unrelated studies also presented in this section found infection controls in veterinary facilities to be inadequate, and they recommended the implementation of written policies and procedures for infection as the best means to improve zoonosis management in veterinary practices.

In "Postexposure prophylaxis" researchers determined that a protocol used in Texas for administering postexposure prophylaxis, consisting of immediate vaccination and follow-up boosters, was effective in preventing disease. These original findings were confirmed in a follow-up study using data from 2000 through 2009. In an unrelated study, experimentally infected dogs given only rabies vaccine postexposure were not protected, while those given vaccine and monoclonal antibody postexposure were adequately protected from disease.

The findings of several studies of oral rabies vaccines are presented in "Vaccination methods." In the first, "Evaluation of oral rabies vaccination programs for control of rabies epizootics in coyotes and gray foxes: 1995-2003," oral rabies vaccine distributed in edible baits was found to be effective in halting the spread of 2 rabies epizootics in Texas involving coyotes and gray foxes. A second study examined both vaccine efficacy and cost efficiency of an oral rabies program used in Texas. The authors found the program to be effective in controlling the spread of rabies, and they found that the economic benefits of the program were 3- to 13-fold greater than the costs. In a third study, the costs of several approaches to distributing fishmeal bait containing oral rabies vaccine to raccoons in Ohio were compared. The authors found that distribution on the ground was consistently less expensive than distribution by helicopter or fixed-wing aircraft.

A study of the efficacy of oral vaccine in a previously vaccinated population of foxes is presented in "Effect of maternal immunity on the immune response to oral vaccination against rabies in young foxes." Cubs of vaccinated and unvaccinated vixens were given oral rabies vaccine, and their antibody titers were checked before and after vaccination. The authors found that the cubs from vaccinated vixens had impaired immune responses which provided insufficient protection against rabies, and that the inhibition of immune response was relatively long lasting. The authors concluded that oral vaccination programs for young foxes in areas where vaccination has been performed should be reconsidered.

In the final study in this section, researchers found that rabies vaccine administered to mice intramuscularly produced a response and level of protection higher than via a subcutaneous route and comparable to an intraperitoneal route. Further, the authors recommended that rabies challenge studies in mice be modified to more closely model vaccine practices in target species, such as in dogs which are typically vaccinated intramuscularly.

A number of studies have been included in "Vaccination safety and efficacy" which reflects the significant amount of research that has been done in this area. Two comprehensive panel reports on vaccination begin this section. The "AVMA Council on Biologic and Therapeutic Agents' report on cat and dog vaccines" contains the results of a comprehensive review of available vaccine information for cats and dogs, conducted by 4 panels of experts from various disciplines. The "The 2006 American Association of Feline Practitioners Feline Vaccine Advisory Panel Report" is also a comprehensive review of vaccine information and is specific to cats. The report contains definitions of core and noncore vaccines as well as summaries of vaccination suggested for use in general practice and in shelter environments respectively.

Adverse event reports associated with rabies vaccination were the focus of research in the next three articles. The authors of a study of 246 rabies-related adverse events reported in dogs found that the rabies vaccine event rate was similar to event rates for other vaccines. Results of a study of adverse events in vaccinated ferrets suggested that ferrets may be at increased risk for adverse events following vaccination, particularly when both rabies and distemper vaccines are administered simultaneously. In another study of adverse events in ferrets, the authors concluded that the risk of adverse events was higher when ferrets had received multiple vaccines over time.

The question of whether chemotherapy has an effect on antibody titers in dogs was addressed in "Association between cancer chemotherapy and canine distemper virus, canine parvovirus, and rabies virus antibody titers in tumor-bearing dogs." Thirty-one client-owned dogs with cancers were studied, and their serum antibody titers were measured before and following chemotherapy treatment. The authors found no significant change in titers, and concluded that prior immunity is not compromised by chemotherapy.

Antibody titers in African elephants was the subject of study in "Serum antibody titers following routine rabies vaccination in African elephants." The authors of this article found great variability in response to vaccination among and between individuals of a captive herd of African elephants, but concluded that detectable antibody titers were present in all animals and persisted beyond 1 year.

In the final article of this section, "Effect of heterogeneity of rabies virus strain and challenge route on efficacy of inactivated rabies vaccines in mice," the accuracy of the standard potency test for rabies is called into question.

The "Additional resources" section contains valuable general reference information related to rabies. The "Compendium of Animal Rabies Prevention and Control," produced by The National Association of State Public Health Veterinarians Committee, is updated every year, and the 2000 through 2008 versions are provided in this collection for reference. The recommendations in the compendium are intended to serve as the basis for animal rabies prevention and control programs throughout the United States. Also, a series of annual reports on rabies surveillance in the United States, from 2000 to 2007, contains comprehensive data regarding rabies cases. The AVMA "Model Rabies Control Ordinance" is also provided to assist those with responsibility for establishing or managing a rabies control program in their communities.

These are just some of the highlights of the information to be found in the "Rabies" collection. We hope you will find it useful as you address rabies prevention and management in your practice and your community.