Do All Dog Bites Lead to Rabies? The Truth About This Common Concern

Introduction

Dog bites are an unfortunate and common occurrence across the United States. According to the American Veterinary Medical Association (AVMA), over 4.5 million dog bite incidents happen every year, with the majority of victims being children (https://www.avma.org/resources-tools/pet-owners/dog-bite-prevention). While most dog bites are relatively minor, any dog is capable of inflicting serious harm under certain circumstances. When a dog bites a person, one of the biggest concerns is the potential transmission of rabies – a viral disease that is almost always fatal once symptoms appear.

What is Rabies?

Rabies is an acute viral infection that affects the central nervous system. It is caused by the rabies virus and can affect both humans and animals. According to the CDC, rabies is almost always fatal once symptoms appear, but is completely preventable if treatment is provided shortly after exposure (CDC).

The rabies virus is a lyssavirus that infects the central nervous system, ultimately causing disease in the brain and death. Once a person or animal is exposed to rabies, the virus spreads through the nerves to the brain (WHO). It has a long incubation period, ranging from one week to one year. During the incubation phase, the virus spreads slowly, causing no symptoms. But once the infection progresses to the brain and symptoms emerge, the disease is nearly always fatal.

microscopic view of the rabies virus

Thus, rabies primarily infects the central nervous system and brain. Without prompt treatment after exposure, the disease is extremely deadly in both humans and animals.

How is Rabies Transmitted?

Rabies is transmitted mainly through the bite of an infected animal. The rabies virus is present in the saliva of rabid animals and gets introduced into a bite wound. It then travels to the central nervous system and causes inflammation in the brain, leading to symptoms.

According to the CDC, rabies virus transmission occurs when infected saliva or tissue makes contact with an open wound or mucous membranes. This is most commonly through a bite from an infected animal, as the virus is concentrated in their saliva. The virus can also be transmitted if saliva gets into open wounds or onto mucous membranes like the eyes, nose or mouth [1].

Once in the body, the rabies virus travels through neurons in the nervous system to eventually reach the brain. This pathway allows the virus to avoid circulating through the bloodstream where it could be detected and cleared by the immune system. The virus incubation period depends on the distance between the site of infection and the brain, but is generally 1-3 months [2].

What Percentage of Dog Bites Lead to Rabies?

Only a small percentage of dog bites actually result in rabies transmission. According to a 2010 study published in BMC Public Health, the median risk of rabies transmission after a dog bite is estimated to be just 0.05% (https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-10-278).

This is because the vast majority of dogs in areas where rabies vaccines are routinely administered are already vaccinated against rabies. Even in areas where canine rabies is more common, only around 15-20% of dog bites transmit rabies, according to the World Health Organization (https://www.who.int/news-room/fact-sheets/detail/rabies).

Therefore, while any dog bite should be taken seriously and treated by a medical professional, the likelihood of developing rabies after a dog bite is generally quite low in most circumstances.

Risk Factors for Rabies Transmission

factors affecting rabies transmission risk
Certain factors can increase the risk of developing rabies after a dog bite. Location of the bite, vaccination status of the dog, and type of bite are key risk factors.

Bites that occur in high-risk countries have a greater chance of transmitting rabies. Over 95% of rabies deaths occur in Africa and Asia, where canine rabies is prevalent. Areas with large stray dog populations also pose an increased risk [1].

Dogs that are unvaccinated or not up to date on rabies vaccines are much more likely to spread the virus if they bite. In one study, owners of vaccinated dogs were 90% less likely to contract rabies after a bite compared to owners of unvaccinated dogs [2].

Severe bites that break the skin carry a higher risk than minor scratches or licks on intact skin. Bites to highly innervated parts of the body like the face and neck also increase chances of rabies virus entering the central nervous system.

Rabies Symptoms in Humans

Rabies symptoms in humans can begin anytime between a few days to a few months after the bite or exposure to an infected animal. The early symptoms are flu-like, including fever, headache, weakness, fatigue, discomfort, and possibly fever.

person showing symptoms of rabies infection

As the disease progresses, more serious neurological symptoms begin to manifest. This includes agitation, anxiety, confusion, hallucinations, excess saliva production, difficulty swallowing, and hyperactivity. The muscles may spasm or become paralyzed. As the disease reaches its late stages, victims fall into a coma and eventually experience death due to respiratory failure.

Diagnosing Rabies

Rabies is diagnosed based on a combination of symptoms, exposure history, and laboratory tests. According to the CDC, several tests are necessary to diagnose rabies in humans before death as no single test is sufficient. Tests are performed on samples of saliva, serum, spinal fluid, and skin biopsies of hair follicles at the nape of the neck. https://www.cdc.gov/rabies/diagnosis/animals-humans.html

In animals, rabies is diagnosed using the direct fluorescent antibody test which detects the presence of rabies virus antigens in brain tissue. https://www.cdc.gov/rabies/diagnosis/index.html

Doctors may suspect rabies based on symptoms such as fever, weakness, headaches, discomfort, or tingling at the site of exposure. A history of potential exposure to rabies through an animal bite or contact with saliva is also considered. Lab tests like skin biopsies, saliva tests, spinal fluid tests, and blood tests can help confirm the diagnosis.

Treating Rabies

Rabies is almost always fatal if left untreated. However, modern rabies vaccines and proper medical care can prevent death in most cases if administered promptly after exposure. According to the CDC, prompt vaccination and administration of rabies immune globulin after exposure can prevent the onset of rabies in virtually all cases (CDC).

The foundation of rabies treatment is rabies vaccination, known as postexposure prophylaxis (PEP). This involves receiving a dose of rabies vaccine as soon as possible after exposure, along with a dose of rabies immune globulin. Additional vaccine doses are given over the next two weeks. PEP is highly effective in preventing the onset of rabies if administered before symptoms appear. Studies show that PEP prevents rabies in nearly 100% of cases when given promptly and appropriately (CDC).

In addition to PEP, supportive medical care is crucial. This may involve treating symptoms such as anxiety, agitation, fever, hypersalivation, hydrophobia and headache. Sedatives may help relieve anxiety and agitation. Intravenous fluids and electrolyte replacement help counter dehydration and electrolyte imbalances. Pain medications provide comfort. Precautions will be taken to prevent the patient from infecting others (Mayo Clinic).

While rabies is almost always fatal once symptoms appear, modern medicine allows for effective prevention when PEP is administered promptly after an exposure occurs.

Preventing Rabies from Dog Bites

There are several key ways to help prevent rabies transmission from dog bites:

ways to prevent rabies transmission

Animal Control – Stray dogs should be avoided and reported to animal control. Unprovoked aggression by dogs should also be reported. Animal control officers can help enforce rabies vaccination laws and remove potentially rabid animals from communities.

Rabies Vaccination Laws – Most states and localities have laws requiring routine rabies vaccination for domestic dogs. Keeping pet dogs up-to-date on rabies shots is crucial for public health. According to the CDC, “First, visit your veterinarian with your pet on a regular basis and keep rabies vaccinations up-to-date for all cats, ferrets, and dogs.” [1]

Post-Bite Prophylaxis – If a dog bite occurs, immediately washing the wound with soap and water can help reduce rabies risk. Bite victims should also receive prompt medical attention to determine if post-exposure prophylaxis (PEP) is recommended. PEP involves receiving the rabies vaccine and in some cases rabies immunoglobulin soon after exposure.

Conclusion

While rabies is a serious disease carried by some dogs, not all dog bites result in rabies transmission. Whether a dog bite leads to rabies often depends on factors like the dog’s vaccination status, the location of the bite, and how promptly the bite wound is cleaned and treated. Though rare in countries with robust animal control and vaccination programs, rabies remains a risk in areas where stray dogs roam freely. But it is also a preventable disease if dog bites are properly handled.

The main takeaway is that while dog bites can potentially transmit rabies under certain conditions, the vast majority do not actually contain or spread this virus. With an understanding of rabies risks and preventative measures, dog bites do not have to become fatal infectious events. Public education, accessible post-exposure treatment, and consistent animal vaccination can help curb rabies transmission from dogs to humans.

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