What is Rabies?
Rabies is a viral disease that affects the central nervous system. It is caused by the rabies virus and is spread through the saliva of infected animals. Rabies is almost always fatal once clinical symptoms appear. According to the CDC, rabies causes tens of thousands of deaths worldwide every year. In the United States, human deaths from rabies are rare due to widespread vaccination of domestic dogs and cats and the availability of post-exposure prophylaxis. Rabies does not cause epidemics and more than 95% of human rabies cases are the result of dog bites.
The rabies virus is a lyssavirus and can infect all warm-blooded animals. Wild animals like raccoons, skunks, bats, and foxes are the most common source of human rabies infections in the United States. The rabies virus infects the central nervous system and causes inflammation of the brain and spinal cord. Once a person or animal begins showing clinical signs and symptoms of rabies, the disease is almost always fatal.
According to the CDC (https://www.cdc.gov/rabies/index.html), rabies causes approximately 59,000 deaths worldwide per year. More than 95% of human deaths from rabies occur in Africa and Asia with India alone accounting for about 36% of rabies deaths. Rabies can be prevented through vaccination. Widespread vaccination of dogs helps control the spread of rabies to humans.
How Do Dogs Get Rabies?
Dogs primarily get rabies through bites from infected animals. Wild animals like bats, raccoons, skunks and foxes are the most common carriers of the rabies virus and transmit it to dogs through bites. According to the Centers for Disease Control and Prevention, over 90% of rabies cases in animals occur in wildlife.
The rabies virus is present in the saliva and brain/nervous system tissue of infected animals. When an infected animal bites another animal, its saliva transmits the virus into the wound. The virus then travels to the central nervous system where it causes inflammation of the brain and spinal cord.
Less commonly, rabies can be transmitted through scratches. If an infected animal’s saliva gets into a fresh scratch wound, the rabies virus can enter the body and make its way to the nervous system.
Overall, direct contact with the saliva or nervous system tissue of a rabid animal is required for transmission. Bites represent the most common route of infection as the animal’s teeth introduce virus-laden saliva deep into the wound.
Source: https://www.cdc.gov/rabies/transmission/index.html
What Are the Stages of Rabies in Dogs?
Rabies progresses in four distinct stages in dogs:
Incubation Period
After a dog is initially infected, the rabies virus travels from the wound site via nerves to the brain and salivary glands. This incubation period usually lasts 3-12 weeks (Source). During this time the dog shows no symptoms of rabies.
Prodromal Period
The prodromal period, lasting 2-3 days, marks the first stage where symptoms are present. Dogs may act restless, hide, or appear anxious. Other signs include fever, lack of appetite, and enlarged pupils (Source).
Furious Period
In the furious stage, lasting 1-7 days, dogs display erratic and aggressive behavior. They may attack inanimate objects, other animals, or people. Other symptoms include excessive salivation, seizures, and roaming. Dogs may bite with no provocation (Source).
Paralytic Period
The paralytic period begins after the furious stage. Dogs become progressively paralyzed, usually starting with the lower jaw and throat muscles. This prevents the dog from swallowing, leading to excessive drooling. Paralysis spreads through the limbs and body until the dog eventually dies, usually by cardiac arrest (Source).
Symptoms of Rabies in Dogs
Some of the most common symptoms of rabies in dogs include:
Fever – One of the earliest signs of rabies is a high fever, often over 104°F. The fever may come and go unpredictably.
Seizures – Dogs with rabies frequently have seizures. The seizures may start as subtle twitching and progress to full grand mal seizures.
Behavior changes – Rabid dogs often exhibit significant behavior changes. Quiet dogs may become agitated and active dogs may become nervous or shy. Dogs may bite or snap at imaginary objects and show signs of confusion or hallucination.
Excessive drooling – Dogs with rabies tend to drool excessively due to paralysis of the muscles in the throat and jaw. The drooling may be thick and ropey in texture.
Difficulty swallowing – Rabid dogs often have trouble swallowing food, water, and even their own saliva due to throat and mouth paralysis.
Loss of appetite – Loss of appetite is common in dogs with rabies. They may refuse all food and struggle to eat or drink.
Paralysis – As rabies progresses, dogs become increasingly paralyzed. The paralysis usually starts in the hind legs and moves up the body. Eventually, dogs have difficulty standing or walking.
According to the CDC, the signs of rabies tend to progress and worsen rapidly once they appear.[1] Dog owners who notice any of these symptoms should seek veterinary care immediately.
How is Rabies Diagnosed in Dogs?
There are two main ways to diagnose rabies in dogs:
Clinical Signs and Medical History
A veterinarian will first look for clinical signs of rabies in the dog and take a medical history. Classic symptoms like sudden behavior changes, paralysis, seizures, and hyperactivity can point to a rabies diagnosis. The vet will also ask about the dog’s potential exposure to rabies through wildlife contact or bites from other animals (CDC).
Laboratory Testing
There are two types of lab tests used to confirm rabies in dogs:
- Analysis of saliva samples – Saliva can be tested for the presence of rabies virus antigens using the fluorescent antibody test (WHO).
- Brain tissue biopsy – Examining brain tissue for rabies antigens using the fluorescent antibody test provides the most definitive diagnosis, but requires euthanasia (CDC).
Any dog suspected of having rabies will likely undergo both saliva testing and a postmortem brain biopsy to confirm the diagnosis.
Is Rabies Always Fatal for Dogs?
Almost always, once clinical signs of rabies appear in dogs, the disease is fatal. According to the CDC, rabies has a mortality rate of over 99% in animals that display symptoms (1). Death usually occurs within 7-10 days after the first symptoms begin (2). This is because rabies causes inflammation of the brain and spinal cord that ultimately leads to paralysis, coma, and death.
However, there are a few very rare documented cases of rabid dog survival with intensive supportive care. One study followed over 1,000 rabid dogs in Thailand and found a small number that survived more than 10 days past displaying symptoms, with a maximum survival time of 15 days (3). Another report documented a rabid puppy surviving 52 days with intensive nursing care (4). However, these cases are extremely rare exceptions, and represent less than 1% of rabies infections in dogs.
So while rabies is not universally fatal 100% of the time, clinicians say recovery is “virtually impossible” once clinical signs occur (5). For all intents and purposes, rabies should be considered a terminal diagnosis in dogs if symptomatic. Prevention through vaccination remains the only reliable way to protect dogs from this deadly disease.
(1) https://www.cdc.gov/mmwr/volumes/68/wr/mm6823e1.htm
(2) https://academic.oup.com/cid/article/39/2/278/328860
(3) https://academic.oup.com/cid/article/39/2/278/328860
(4) https://academic.oup.com/cid/article/39/2/278/328860
(5) https://www.who.int/news-room/fact-sheets/detail/rabies
Treatment Options for Rabies in Dogs
Unfortunately, once a dog begins showing symptoms of rabies, there is no effective treatment. Rabies causes almost 100% mortality in dogs once clinical signs appear.
According to the Mayo Clinic, “Though a small number of people have survived rabies, the disease usually causes death.” This is also true for dogs – survival is extremely rare (source).
Veterinarians can provide supportive care to try to ease a dog’s suffering, but this will not cure rabies. Supportive care may include:
- Fluids and nutrition support
- Medications to control seizures and paralysis
- Comfort measures
However, most dogs with symptomatic rabies will ultimately need to be euthanized.
Pre-exposure vaccination of dogs is critical for rabies prevention. Dogs that receive rabies vaccines prior to exposure have immunity that helps their body mount a faster immune response if exposed to the virus (source).
In cases of potential exposure, post-exposure prophylaxis may prevent rabies if administered promptly. This involves immediately cleaning the wound, vaccinating the animal, and in some cases administering rabies antibodies. However, this is only effective if done right after exposure and before the virus enters the nervous system.
Preventing Rabies in Dogs
The most effective way to prevent rabies in dogs is through routine vaccination starting at 12-16 weeks old. The rabies vaccine is considered a core vaccine by veterinarians and should be boostered yearly. Puppies receive an initial vaccination between 12-16 weeks old, with a booster 1 year later, and then boosters every 1-3 years, depending on state laws and your veterinarian’s recommendations. Keeping your dog up-to-date on its rabies vaccination is critical to preventing the disease.
You should also take precautions to avoid your dog’s contact with wildlife that may be infected with rabies. Supervise your dog when outdoors and walk on a leash in areas with wild animals. Do not leave pet food or water bowls outside that may attract wild animals. Make sure your home is secured against wildlife gaining entry to areas where your dog lives and plays.
If you believe your dog has been bitten or scratched by an animal that could have rabies, contact your veterinarian immediately. They will assess the potential rabies exposure and may recommend booster vaccination if it’s been longer than 3 years since your dog’s last rabies vaccine. Bites should be reported whether or not your dog is up-to-date on rabies vaccination. Your vet is required to report animal bites by law.
By vaccinating your dog routinely for rabies, avoiding contact with wildlife, and reporting any potential exposures, you can effectively prevent this deadly disease in your pet.
Risks to Humans
Rabies is a zoonotic disease, meaning it can spread from infected animals to humans. According to the CDC, domestic dogs are responsible for up to 99% of rabies virus transmission to humans globally (CDC). If a person is bitten by a rabid dog, the virus can infect them through broken skin or mucous membranes. The rabies virus travels to the brain, causing disease.
If you are bitten by a dog, it is crucial to immediately and thoroughly wash the wound with soap and water. Seek medical care to assess if post-exposure prophylaxis (PEP) is needed. PEP consists of a dose of rabies vaccine and in some cases, rabies immunoglobulin. PEP is highly effective in preventing the onset of rabies if administered promptly after a rabies exposure (WHO).
Vaccinating dogs is the most effective way to prevent human rabies infections. In areas where canine rabies is endemic, dog vaccination coverage of at least 70% is necessary to eliminate rabies in dogs and humans (WHO). Responsible pet ownership includes keeping rabies vaccinations current.
Outlook for Rabid Dogs
The outlook for dogs that develop symptoms of rabies is extremely grave. Once a dog starts showing signs of rabies, the disease is nearly always fatal1. There is no effective treatment for rabies in dogs at this advanced stage, so euthanasia is typically recommended to prevent further suffering2.
However, the prognosis is better if rabies treatment is started immediately after exposure, before any symptoms develop. The rabies vaccine, when administered promptly after a suspected rabies encounter, is very effective at preventing the disease from taking hold in a dog’s body. But once the neurological symptoms appear, it is too late for treatment3.
Prevention is key when it comes to rabies in dogs. Following vaccination guidelines, avoiding contact with wild animals, and getting booster shots as recommended can help stop the transmission and development of this fatal virus.