Rabies virus

Rabies virus is a neurotropic virus that causes rabies in humans and animals. The virus is a member of the Lyssavirus genus, within the family Rhabdoviridae, and is characterized by its bullet-shaped virion. Rabies is a zoonotic disease, primarily transmitted through the saliva of infected animals via bites, scratches, or mucosal contact. The rabies virus has a wide host range, including domestic and wild mammals, with dogs being the most common vector for human rabies in endemic regions.

Etiology and Pathogenesis

The rabies virus contains a single-stranded, negative-sense RNA genome. Upon entry into the host, the virus binds to nicotinic acetylcholine receptors at the neuromuscular junction, facilitating its entry into peripheral nerves. It then travels retrogradely within the axon towards the central nervous system (CNS), where it causes severe neurological dysfunction. The virus's ability to evade the host's immune response and its preferential replication in neurons contribute to the disease's high mortality rate once clinical symptoms appear.

Clinical Manifestations

The incubation period of rabies can vary widely, from weeks to years, but typically ranges from one to three months. The disease progresses in five stages: incubation, prodrome, acute neurologic period, coma, and death. Initial symptoms are nonspecific, including fever, malaise, and headache. As the virus spreads to the CNS, neurological symptoms develop, which can include hydrophobia, aerophobia, agitation, confusion, and paralysis. Without prompt treatment, the disease invariably progresses to coma and death, usually due to respiratory failure.

Diagnosis

Diagnosis of rabies is primarily based on clinical presentation and history of exposure to potentially rabid animals. Laboratory tests can confirm the diagnosis, including direct fluorescent antibody testing of tissue samples, reverse transcription polymerase chain reaction (RT-PCR) on saliva or cerebrospinal fluid, and virus isolation. However, these tests are often performed postmortem.

Prevention and Control

Prevention of rabies is focused on controlling rabies in animals, vaccination of at-risk populations, and post-exposure prophylaxis (PEP) for individuals exposed to the virus. Vaccination of domestic animals, especially dogs, is the most effective way to prevent rabies in humans. For individuals at high risk of exposure, such as veterinarians and animal handlers, pre-exposure vaccination is recommended. PEP, consisting of wound cleaning, rabies immunoglobulin, and vaccination, is highly effective if administered promptly after exposure.

Treatment

Once clinical symptoms of rabies appear, there is no effective treatment, and the disease is almost always fatal. Supportive care can be provided to alleviate symptoms, but efforts to prevent the disease through vaccination and PEP are paramount.

Epidemiology

Rabies is present worldwide, with over 95% of human deaths occurring in Asia and Africa. The disease disproportionately affects children and individuals in rural areas where access to vaccination and PEP is limited.

Public Health and Global Impact

Rabies remains a significant public health challenge in many parts of the world, despite being preventable. Efforts to eliminate rabies focus on improving awareness, increasing access to vaccines and PEP, and implementing mass vaccination campaigns in dogs.