September 28, 2017 – World Rabies Day is an important awareness day targeting a lethal disease. The word rabies may conjure up images of dogs foaming at the mouth, bats randomly biting people, and videos posted online of crazed skunks and raccoons. To be certain, rabies continues to be a threat to people, livestock and pets around the world and research continues to be conducted to best understand the disease. Morris Animal Foundation has supported more than a dozen projects to eliminate the disease in an effort to protect animals. Despite awareness days and continued research, many misperceptions about rabies exist, fueled by images from popular culture and widespread misinformation. As a pet owner, this blog may help you sort fact from fiction, an important step to protecting your pets from this fatal but very preventable disease.
Rabies through the years
First described almost 5,000 years ago in Mesopotamia, rabies was well known in Europe for centuries. Around the 1700s, rabies was introduced to the United States and rapidly spread across the continent, becoming established in native wildlife species.
The first rabies vaccine was introduced in 1885, and was followed by an improved version in 1908, which is regularly revised and tweaked. Millions of people and animals globally have been vaccinated and it is estimated that this saves more than 250,000 human lives a year. Today, the rabies vaccine is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system.
As vaccination became commonplace in the last century, the incidence of human and domestic animal rabies greatly declined in developed countries. However, the disease remains a serious problem in many areas of the world, particularly in developing nations. The World Health Organization estimates that from 55,000 to 100,000 people die each year from rabies, which averages to one death from rabies every 10 minutes.
Wild carnivores remain the most important reservoir of rabies, with species varying depending on location. Skunks, raccoons, foxes and coyotes are the dominant wildlife reservoirs in the United States. Bats also carry the virus but aren’t common sources of infection for dogs and cats.
Bites from infected dogs are responsible for 95 percent of human rabies deaths. All warm-blooded animals are susceptible to infection, and an untold number of animals die from rabies each year worldwide. In developing nations, studies suggest that vaccinating a minimum of 70 percent of dogs in a given region is effective in controlling the disease within that population. This percentage is frequently used as a guideline in developing and implementing mass canine vaccination programs. A similar number hasn’t been established for cat populations.
A virus with a lethal destination
Rabies is caused by a virus in the Rhabdoviridae family of viruses. Rabies virus is shed in the saliva of infected animals, and transmitted through breaks in the skin caused by a bite, or via a scrape or wound. Once the virus enters a new host, it invades local nerve endings and uses the nervous system as a “highway” to move to the brain. Once in the brain, the virus continues to infect nerve cells, ultimately resulting in death.
It can take days, weeks or even months for an infected individual to start showing signs of rabies infection, depending on how quickly the virus enters the nervous system. On average, the incubation time before the start of signs is three to eight weeks in dogs, and four to six weeks in cats. However, incubation times can be influenced by several factors, including:
- Age of the individual infected
- Number of nerve fibers at the bite site
- Distance of the bite from the spinal cord or brain
- Amount of virus introduced
After the virus reaches the brain and spinal cord and begins to reproduce, virus particles move to other body tissues. It’s during this phase that the virus enters the salivary glands, and can be transmitted to other animals and people. Rabies virus can be present in the saliva for a few days (usually one to five days) before the onset of signs.
Signs of rabies infection in cats and dogs
Although rabies has historically been divided into two major types – excitatory (“furious”) and paralytic (“dumb”) – signs of rabies can vary significantly between individuals, and not all animals with rabies progress through each stage. Despite these differences, there are common signs most cats or dogs with rabies display.
The early stages of rabies infection often is called the prodromal, or initial, phase. Early signs of rabies in both dogs and cats include:
- Nervousness, anxiety and restlessness
- Fever (more common in cats)
- Licking/chewing/clawing at site of infection
Initial signs last from two to three days in dogs, and from one to two days in cats. The disease then progresses to either the furious or paralytic form.
Approximately two-thirds of infected dogs and cats will exhibit a furious phase, lasting from one to seven days. Cats more consistently develop the furious phase of the disease than dogs.
Clinical signs of the furious form of rabies are:
- Restlessness, aggression
- Increased sensitivity to sound and light
- Ingestion of unusual objects (dogs)
- Muscular incoordination, disorientation and seizures
Some dogs will move to a paralytic phase after the furious phase, and others only show a paralytic form of the disease. Cats frequently show both forms of the disease.
Clinical signs of the paralytic form of rabies are:
- Increased salivation or frothing at the mouth due to difficulty swallowing
- Difficulty breathing
- Choking sounds
- Voice change
- Coma and death
Individuals can vary in the time they spend in each phase, but very few animals survive the infection once clinical signs are noted. Almost all animals with rabies will die within 10 days of showing clinical signs. Humane euthanasia is recommended in dogs and cats when rabies is strongly suspected.
Diagnosis of rabies is difficult in the live animal, and attempts to make a diagnosis of rabies before death is not recommended. Very few non-invasive tests are accurate, and sample collection places veterinary staff at risk.
There are a number of postmortem tests that give reliable and accurate results, and any animal suspected of having rabies should have diagnostic testing performed on tissues after death. Obtaining a definitive diagnosis of rabies is important, particularly if pet owners and veterinary hospital staff have been exposed or bitten as they may need post-exposure rabies vaccines.
Your veterinarian, as well as the Centers for Disease Control and Prevention, is a good source of information regarding testing of suspected animals.
Rabies is a preventable disease
Vaccinating your pet against rabies remains the best way to protect your pets as well as human family members from the disease.
Rabies vaccination has dramatically decreased the incidence and diagnosis of rabies in many countries, including the United States. Duration of immunity – the amount of time an animal is protected from a disease after vaccination – for rabies vaccines is at least three years. Young animals require more than one injection for full immunity.
Because of the public health concerns associated with rabies infection, rabies vaccination schedules are legislated based on the incidence of rabies in a given area. Reactions to the rabies vaccine tend to be minor, such as pain at injection site and mild fever, and are infrequent. Data from the United Kingdom showed only 0.61 reactions per 10,000 doses in the cat, and mere 0.21 reactions per 10,000 in dogs.
A potential serious complication from vaccination is the development of an injection site sarcoma, a malignant tumor that can arise at any subcutaneous (under the skin) injection site. These tumors are more common in cats than dogs, and the reported incidence is one to four cases per 10,000 cats. However, since domestic cats in the United States have a higher incidence rate of rabies than dogs, the risk of rabies vaccination usually outweighs the risk of cancer. Your veterinarian can help guide you on the best decision for your cat.
Recommendations vary for pets exposed to rabid animals
There is no treatment for rabies once an animal is showing clinical signs and that is why it is so important to keep vaccinations up to date. Treatment of dogs and cats exposed to a potentially rabid animal is often difficult, and subject to local laws. Sometimes the biting animal is available for rabies testing, which is helpful in determining whether a pet was actually exposed or not. However, in many cases, the biting animal is not known.
The National Association of State Public Health Veterinarians recommends that unvaccinated dogs and cats exposed to a rabid animal are either quarantined for six months, or immediately euthanized. Dogs and cats that are current on rabies vaccination and are potentially exposed should see a veterinarian for wound care and booster vaccination. These pets can stay with their owners but must be observed for 45 days. The process is more difficult in pets that have received vaccination in the past but are not current, and can vary from patient to patient.
Morris Animal Foundation and rabies research
A major funding focus for Morris Animal Foundation are diseases, like rabies, with a broad geographical footprint that affect multiple species. Developing nations with few resources sometimes cull animals to stop the spread of rabies. With the help of governments and world health organizations, mass vaccination programs sometimes are available for these countries. But there is always more to be done.
Morris Animal Foundation has invested just over $500,000 in 15 research projects studying many different aspects of rabies infection, from vaccination strategies for bats to understanding the impact of rabies vaccination on the health or rural South African dogs and the surrounding community.
World Rabies Day is September 28
While great strides have been made in rabies prevention and treatment globally, the World Health Organization continues to include rabies on its neglected tropical disease roadmap. As an on-going health concern, close cross-sectional coordination at the national, regional and global levels is necessary to control the disease. A part of these efforts is raising awareness about rabies through World Rabies Day, held this year on September 28.
WHO, with its partners the Food and Agriculture Organization of United Nations (FAO), World Organization for Animal Health (OIE), and the Global Alliance for Rabies Control, is developing an international action plan to reach zero human deaths from dog-transmitted rabies by 2030. The plan covers policy, human and animal interventions, awareness raising and advocacy, capacity building, and the respective resources needed for elimination of the disease in countries still suffering from rabies.