This article provides a brief overview of the Rabies virus and the disease it causes. The virus is a highly dangerous pathogen belonging to the family Rhabdoviridae. It is responsible for Rabies, a disease that primarily affects mammals and can be transmitted to humans through the bite of infected animals. Although rabies is almost always fatal once symptoms appear, timely diagnosis and vaccination can effectively prevent the disease.
Rhabdoviruses and Vesicular Stomatitis Virus
Rhabdoviridae are viruses with a distinctive bullet-like shape and relatively large dimensions, measuring approximately 70–80 nm in width and 130–240 nm in length. Their structure includes a helical nucleocapsid that encloses a single-stranded negative-sense RNA genome. Surrounding this nucleocapsid is a lipid envelope that carries glycoprotein spikes on its surface, which function as important antigenic components.
Members of this viral family are capable of infecting humans, animals, and even plants, producing a variety of diseases. One notable group of animal rhabdoviruses is the Vesicular stomatitis virus (VSV) group. These viruses commonly infect livestock such as cattle, pigs, and horses, leading to the development of vesicular (blister-like) lesions in the mouth and sometimes on other parts of the body.
The exact transmission route of vesicular stomatitis virus is not fully established, but it is believed that arthropods, such as insects, may play a role in spreading the infection. Humans can occasionally become infected as well, usually developing a mild illness resembling vesicular stomatitis. This condition may include symptoms such as fever, malaise, body aches, headache, nausea, and vomiting, but it is generally not severe.
Rabies Virus and Rabies Disease in Humans
The most significant member of the Rhabdoviridae is the Rabies virus, which infects both domestic and wild mammals. Scientists recognize this Rabies virus as a single immunological type, meaning that all its strains share very similar antigenic properties. Humans usually become infected when an infected animal transmits the virus through its bite, leading to Rabies. The animals most commonly responsible for spreading the virus to humans include dogs, cats, bats, and skunks.
The disease caused by this virus is Rabies, which primarily affects the central nervous system, resulting in severe inflammation of the brain and spinal cord (encephalomyelitis) (Below Flowchart ). In humans, the incubation period (the time between infection and the appearance of symptoms) can range from about 6 days to as long as 1 year, although it typically lasts 3 to 8 weeks. The length of this period and the severity of the disease largely depend on factors such as the depth and location of the animal bite.
The Flowchart
Bite of a Rabid Animal
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The virus enters muscle tissue
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The virus multiplies at the bite site
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The virus enters the peripheral nerves
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The virus travels to the spinal cord
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Virus reaches the brain
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Encephalitis develops
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The virus spreads to the salivary glands
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Transmission to another host
Only a small percentage of individuals bitten by rabid animals, estimated at 5–15%, actually develop rabies. When symptoms appear, they usually begin with severe headache, high fever, and general discomfort. As the disease progresses, patients may experience alternating periods of agitation and depression. Another characteristic symptom is difficulty swallowing, and even mild external stimuli can trigger painful muscle spasms in the throat and chest. In the later stages, the disease typically leads to paralysis or severe convulsions, which eventually cause death. Once symptoms develop, rabies is almost always fatal, with a mortality rate approaching 100 percent.
Prevention, Diagnosis, and Vaccination of Rabies
When an animal suspected of carrying the Rabies virus bites a person, doctors can use the relatively long incubation period of Rabies to prevent the virus from spreading to the central nervous system. Preventive treatment usually involves a combination of passive immunization(administration of rabies antibodies) and active immunization through vaccination.
Several laboratory tests are performed to confirm whether the biting animal is infected. These include:
- Detection of viral antigens in clinical samples using fluorescent antibody techniques.
- Isolation of the virus from materials such as saliva, urine, cerebrospinal fluid, or tissues by inoculating them into the brains of laboratory mice.
- Microscopic examination of brain nerve cells to identify characteristic viral inclusion bodies.
However, negative laboratory results do not completely rule out rabies infection. Therefore, an animal suspected of transmitting the virus should not be destroyed immediately. Instead, it should be kept under observation for at least two weeks. If signs of rabies appear during this period, the person who was bitten must undergo vaccination.
The development of rabies vaccines has a long history. In 1885, Louis Pasteur produced the first effective vaccine by using brain tissue from rabbits infected with the rabies virus. He dried the infected nerve tissue for different periods of time. The virus gradually weakens, allowing it to safely stimulate immunity in individuals who have been exposed to Rabies.
Later, in 1919, David Semple improved Pasteur’s method by treating the virus with phenol, which completely inactivated it. Although these early vaccines were effective, they sometimes produced allergic encephalitis. It is because they contained nerve tissue components that could trigger immune reactions.
Vaccination
In 1949, scientists introduced a new approach by preparing a vaccine from a live attenuated strain of the Rabies virus known as the Flury strain. Researchers grew this virus in embryonated duck eggs and widely used the resulting vaccine. However, the vaccine produced a relatively weak immune response. Although it contained fewer nerve tissue antigens, it still occasionally caused allergic encephalitis in some recipients.
A major improvement occurred in 1980 with the introduction of an inactivated rabies vaccine produced in cultures of human diploid cells. Because this vaccine does not contain nerve tissue antigens, it is safer and produces a strong immune response. Today, such vaccines are considered both highly effective and reliable for preventing rabies following exposure.
Conclusion
Rabies is one of the most dangerous viral diseases caused by the Rabies virus, a member of the Rhabdoviridae. The infection is mainly transmitted to humans through the bite of infected animals such as dogs, bats, and other mammals. Although rabies is almost always fatal once clinical symptoms develop, the disease can be effectively prevented if appropriate treatment and vaccination are given soon after exposure. Advances in vaccine development have greatly improved both the safety and effectiveness of rabies prevention. Therefore, early diagnosis, prompt post-exposure treatment, and proper vaccination programs in animals and humans remain essential measures for controlling this deadly disease.
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I, Swagatika Sahu (author of this website), have done my master’s in Biotechnology. I have around fourteen years of experience in writing and believe that writing is a great way to share knowledge. I hope the articles on the website will help users in enhancing their intellect in Biotechnology.