- Also called:
- hydrophobia or lyssa
- Key People:
- Louis Pasteur
- Sir Victor Horsley
- Related Topics:
- dog
- disease
- notifiable disease
- rabies virus
rabies
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What is rabies?
Rabies is a typically fatal viral disease impacting the central nervous system. It spreads through the bite of infected animals, such as domestic dogs and wild carnivores. The rabies virus travels from the bite through the nerve tissue to the brain, where it becomes established in the central nervous system. It subsequently spreads to the salivary glands, causing a foaming at the mouth.
Symptoms in animals include excitation, viciousness, and paralysis. In humans, rabies symptoms include headache, nausea, muscle stiffness, and hydrophobia (dread of water). There is no cure once the symptoms start.
Preventive measures, like vaccines, can prevent the disease if administered shortly after exposure. Disease control may also include vector-control programs for ticks, fleas, or mosquitoes, and environmental cleanup.
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How does the rabies virus enter and spread in the body?
The rabies virus, typically transmitted through the bite of an infected animal, enters the body via a fresh wound. The virus then travels along nerve tissue from the wound to the brain, where it becomes established in the central nervous system. After a period that ranges from 10 days to eight months, it spreads through the nerves to the salivary glands, where it multiplies, causing the infected animal to foam at the mouth. The disease often begins with excitation of the central nervous system, which is expressed as viciousness and irritability.
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Which body systems are most affected by rabies?
Rabies primarily affects the central nervous system. After the rabies virus enters the body through a bite, it travels along the nerve tissues to the brain, where it becomes established. The virus then spreads through the nerves to other areas, such as the salivary glands.
Symptoms of rabies include excitation of the central nervous system, which can manifest as irritability and viciousness. As the disease progresses, paralysis can occur. In humans, hydrophobia (a dread of water) is a notable symptom due to the paralysis of throat muscles, along with increased saliva production. Cardiac or respiratory failure usually causes death.
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What are the main symptoms of rabies in humans?
The primary symptoms of rabies in humans are similar to those in animals. Initial symptoms include headache, fever, depression, and anorexia. As the disease progresses, other symptoms such as seizures, muscle stiffness, and increased saliva production may occur.
A common early symptom is abnormal sensations, such as itching, around the site of exposure. Paralysis of the throat muscles can cause difficulty swallowing and a dread of water (hydrophobia). Mental states can vary, but infected persons eventually fall into a coma and typically die in less than one week as a result of cardiac or respiratory failure.
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How does rabies damage the nervous system?
Rabies is a viral disease that affects the central nervous system, typically transmitted through the bite of infected animals. The rabies virus travels through nerve tissue from the wound to the brain, where it becomes established. This can lead to excitation, such as viciousness and irritability. Once in the central nervous system, the virus spreads to the salivary glands, potentially causing a foaming at the mouth. Symptoms in humans include headache, fever, and seizures. As the disease progresses, paralysis can occur, along with an inability to swallow or drink, and eventually coma and death, often due to respiratory or cardiac failure.
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Why is rabies almost always fatal once symptoms appear?
Rabies is almost always fatal once symptoms appear because the virus travels quickly from the bite to the central nervous system. By the time symptoms manifest, the virus has already established itself in the brain, making it difficult to treat.
Symptoms in humans include depression, headache, nausea, seizures, muscle stiffness, and increased saliva production. Paralysis of the throat muscles leads to hydrophobia (dread of water) because the person cannot swallow. The disease progresses to a coma, and death usually occurs within a week due to cardiac or respiratory failure.
There is no cure for rabies, so treatment focuses on preventing the virus from establishing itself by washing the bite wound and administering antirabies serum and rabies vaccine.
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rabies, acute, ordinarily fatal, viral disease of the central nervous system that is usually spread among domestic dogs and wild carnivorous animals by a bite. All warm-blooded animals, including humans, are susceptible to rabies infection. The virus, a rhabdovirus, is often present in the salivary glands of rabid animals and is excreted in the saliva; thus, the bite of the infected animal introduces the virus into a fresh wound. Under favourable conditions, the virus propagates along nerve tissue from the wound to the brain and becomes established in the central nervous system. After a time it spreads via nerves to the salivary glands, where it frequently produces a foaming at the mouth. The disease develops most often between four and six weeks after infection, but the incubation period may vary from 10 days to eight months.
Rabies virus travels quickly in a bitten animal (e.g., raccoons, skunks, bats, foxes, dogs, and cats, among other smaller animals) from the bite to the central nervous system. The disease often begins with excitation of the central nervous system expressed as irritability and viciousness. A rabid animal is most dangerous during the early stages of the disease because it appears to be healthy and may seem friendly but will bite at the slightest provocation. Wild animals that appear to be tame and that approach people or human habitations in the daytime should be suspected of having rabies.
Infected dogs usually show a short excitation phase that is characterized by restlessness, nervousness, irritability, and viciousness and is followed by depression and paralysis. After a few days they are unable to bite any more because the muscles of the throat are paralyzed; they seek only a quiet place to hide and die from the rapid spread of paralysis. Sudden death without recognizable signs of illness is also not uncommon. Dogs that develop the predominantly excited type of rabies invariably die of the infection, usually within three to five days after the onset of symptoms. Those that develop the paralytic type of rabies without any evidence of excitation or viciousness may recover on rare occasions. Paralysis of the “voice” muscles in rabid dogs may produce a characteristic change in the sound of the bark.
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Rabies in humans is similar to that in animals. Symptoms include depression, headache, nausea, seizures, anorexia, muscle stiffness, and increased production of saliva. Abnormal sensations, such as itching, around the site of exposure are a common early symptom. The muscles of the throat become paralyzed so that the person cannot swallow or drink, and this leads to a dread of water (hydrophobia). The mental state of a person infected with rabies varies from maniacal excitement to dull apathy—the term rabies means “madness”—but soon the person falls into a coma and usually dies in less than one week owing to cardiac or respiratory failure. Sometimes rabies is characterized by paralysis without any evidence of excitation of the nervous system. In such cases the course of the disease may be prolonged to a week or more.
There is no cure for rabies. The incubation period (the time that elapses between the bite and the first symptom) is usually one to three months but in rare cases has been as long as several years. This provides a chance to interrupt the otherwise inevitable progress of the infection. The bite should be washed immediately because much, if not all, of the virus can be thus removed. The bitten patient should then receive a dose of antirabies serum. Serum is derived from horses or humans that have been immunized with attenuated rabies virus; it provides the patient with already prepared antibodies against the rabies antigen. The treatment is effective if given within 24 hours after exposure but has little, if any, value if given three or more days after infection by rabies.
Active immunization with rabies vaccine should also be initiated to allow the patient’s body to make its own antibody. The safest and most effective vaccines are human diploid cell vaccine (HDCV), purified chick embryo cell culture (PCEC), and rabies vaccine adsorbed (RVA). With older vaccines, at least 16 injections were required, whereas with HDCV, PCEC, or RVA, 5 are usually sufficient. Persons at risk of rabies by virtue of occupation (e.g., veterinarians) or travel to endemic areas should receive rabies vaccine as a form of preexposure prophylaxis.