Rabies Awareness and Prevention
September 28, 2016 commemorates World Rabies Day, a Centers for Disease Control (CDC) and Alliance for Rabies Control (ARC) initiative to educate the global community about prevention and control of the disease.
Pet owners are likely aware of Rabies as a result of state-mandated vaccinations that help prevent our canine and feline companions from becoming infected. But, what kind of infectious organism is Rabies, how are pets exposed to it, and why is the Rabies vaccination legally required? Additionally, what happens if your pet has previously had an adverse response to a Rabies vaccination or has an underlying ailment that could be aggravated if a Rabies vaccination is given?
What is Rabies and how is it transmitted?
Rabies is a virus capable of spreading between different species and therefore is considered to be a zoonotic disease (zoonosis). The primary means of transmission is through a bite wound by an infected animal. Other modes of transmission have been documented and are uncommon, including contact between Rabies-contaminated saliva and mucous membranes (eyes, nose, mouth), inhalation of virus-contained saliva (aerosol aspiration), and organ transplants (cornea, other tissues).
Bats, foxes, skunks, raccoons, and other wild animals are common vectors for Rabies. As cattle, horses, and other farm animals often live in close proximity to wildlife, they are also at risk for Rabies infection. Hunting and farm dogs and indoor/outdoor cats are at higher risk than pets that spend their lives predominantly inside. Yet, exposure risks exist everywhere and are often unforeseen. For example, a bat that gets into your house is a potential source of Rabies infection for both pets and people.
The incubation period, which is the time it takes between exposure and development of clinical signs, take three to twelve weeks and varies depending on the level of existing immunity and immune system health.
Rabies proliferates in muscle tissues then spreads along nerve fibers to enter the central nervous system (CNS), including the brain and spinal cord. The virus replicates in the brain, causes a type of inflammation called encephalitis, and moves into the salivary glands and saliva to facilitate transfer to another host organism. Rabies virus can be spread by saliva even before clinical signs of the disease appear.
The development of encephalitis causes brain damage and leads to clinical signs within three to five days. Clinical signs can be diverse and non-specific to the nervous system, including:
- Digestive tract upset – vomiting, diarrhea, decreased appetite and water consumption
- Ptyalism – excessive salivation
- Hyperthermia – elevated body temperature
- Pica – consumption of environmental materials
- Behavior changes – aggression, avoidance of interaction, irritability, etc.
- Altered vocalization or respiration – changes in the sound or tone of a bark or meow or respiratory pattern due to paralysis of the larynx (voice box)
- Unusual jaw position – the mandible (jaw bone) drops and lends to a slacked appearance
- Ataxia – difficulty standing or walking
Death typically occurs within seven days of the development of clinical signs.
Can Rabies be treated?
Unfortunately, once an animal starts to show clinical signs of Rabies there is no known treatment. Pets that are bitten by an animal suspected to be rabid (i.e. be infected with Rabies) must be quarantined during the incubation period and monitored for the development of clinical signs. If you know or suspect your pet has been exposed to Rabies, immediately call your veterinarian or local emergency veterinary hospital.
With no treatment being available, we veterinarians need to focus on Rabies prevention via education and vaccination.
How is Rabies prevented?
Rabies is prevented through a combination of avoidance and vaccination. Fortunately, with the advent of immunizations to prevent Rabies infection, the disease has been considerably controlled on a local and worldwide basis.
The State of California Health and Human Services Agency reports “between 50,000 and 75,000 cases of human Rabies are estimated to occur each year worldwide. Over 90% of these cases occur following exposure to a rabid dog. In the United States, Rabies is rare among dogs because all states have laws that require dogs to be vaccinated against Rabies. Nevertheless, approximately one-fifth of the human Rabies deaths in the United States in the last 20 years occurred in people who had contact with a rabid dog in a foreign country where Rabies vaccination is not widely practiced.”
Vaccination promotes the immune system to produce antibodies. Antibodies are proteins that help to signal white blood cells to target and eliminate infectious organisms like Rabies virus.
Legal requirements for Rabies vaccination vary by state. In California, dogs are legally required to be vaccinated for Rabies by four months of age. A booster vaccination is recommended 12 months later, then every 36 months depending on the dog’s heath status. California-dwelling cats, horses, and other animals are not legally required to be vaccinated for Rabies, but doing so is strongly recommended.
In 2011, a change in the legality of Rabies vaccination occurred when AB 258 (AKA Molly’s Bill) was passed in California. AB 258 will “exempt from the vaccination requirement a dog whose life would be endangered due to disease or other considerations that a veterinarian can verify and document if the dog received the vaccine, as determined by a licensed veterinarian on an annual basis.”
According to Los Angeles County Canine Rabies Vaccination Exemptions AB 258 applies only select group of dogs, including as those having:
- Life-threatening anaphylactic reaction after administration of a Rabies vaccine, specifically. Facial angioedema and hives do not qualify as life-threatening.
- Immune-Mediated Hemolytic Anemia (IMHA), if:
- Onset was within 1 month of a Rabies vaccination, or
- More than one episode (i.e. relapses)
- Dog is currently on immunosuppressive therapy for cancer or immune-mediated disease (low dose prednisone is not considered immunosuppressive therapy).
Ultimately, Molly’s Bill helps veterinarians and pet owners pursue the best route of health maintenance while abiding by state regulations aimed at minimizing zoonotic disease affecting both people and pets. My dog Cardiff has endured four episodes of Immune Mediated Hemolytic and is currently under treatment on an ongoing basis for T-Cell Lymphoma, so I’m grateful that he can be exempt from further Rabies vaccination.
What strategies do you take to reduce your dog’s potential exposure to Rabies? Feel free to share your perspective in the comments section.