Wikipedia rabies virus

Here, prevalent symptoms include difficulty with coordination, paralysis, seizures, signs of choking or difficulty swallowing food or water, and frothing at the mouth. Other abnormal behaviors include depression, odd vocalizations, appearance of nocturnal animals during the day, and, in carnivores, evidence of having attacked porcupines.

Death usually results from respiratory arrest. In addition to bites by infected animals, rabies can be transmitted by infected animal licks or saliva that come into contact with the mucous membranes of the eyes, nose, lips, or skin wounds. The virus is inactivated by external factors, such as exposure to direct sunlight, ultraviolet radiation, chemicals, detergents, and strong acids and bases, and thus, cannot thrive in the environment.

At this point, the virus is not immediately evident within the host and vaccination may lead to cell-mediated immunity, which will prevent the symptoms of rabies in the host. Once the virus reaches the brain, it replicates and then spreads to other organs of the body via the nervous system.

At this prodromal stage, symptoms appear and treatment is ineffective. The salivary glands in the mouth and cheeks receive a high concentration of the virus, thereby facilitating further viral transmission when the diseased animal bites another animal.

In humans, early symptoms of rabies are nonspecific and include fever, headache, and overall lethargy. As the disease progresses, neurological symptoms emerge, including anxiety, insomnia, confusion, violent movements, partial paralysis, agitation, hallucinations, hyper-salivation, difficulty swallowing, and hydrophobia fear of water , which is also another name for the virus.

If left untreated, rabies is always fatal in humans and death can occur within days of symptom onset. Death may result from respiratory insufficiency, brain swelling, or pneumonia. This usually occurs two to ten days after the first symptoms, and the few humans known to have survived the disease all suffered from severe brain damage. The period between infection and the first flu-like symptoms normally occur between two and twelve weeks, but may even last up to two years. Transmission between humans is very rare though there are documented cases associated with transplant surgery.

Only six people are reported to have survived symptomatic rabies, while two survivors received no rabies-specific treatment either before or after the onset of illness. In Israel, decisions to vaccinate are the exclusive decision of public health physicians in the district health offices, affording the process a measure of expertise.

Although the incidence of rabies in Israel has declined from 97 cases in to 43 cases in , rabies remains a significant public health problem in Israel, thus indicating the importance of compliance to a rabies post-exposure prophylaxis.

Treatment guidelines emphasize four levels of risk based on the type of animal exposure. Vaccinations are required of those exposed to wild or unidentified animals, whereas vaccinations are not deemed necessary following rodent bites, or exposure to large, domestic farm animals.

Decisions to vaccinate were more common for those aged and soldiers, and were 2. Absence of provocation of the animal was 2. Finally, senior physicians recommended vaccination 1. Listed in descending order, the variables that influenced the decision to vaccinate were type of animal, type of exposure, and definition of area as rabies enzootic.

Also statistically significant were being a soldier, provocation, and being a senior physician. Regarding type of animal, the guidelines had initially grouped all domestic animals in a single risk category, but were later revised to state explicitly that, according to the epidemiology of rabies in Israel, identification of cat rabies is relatively rare, and thus there is a much lower risk of contracting rabies following exposure to cats.

One end is rounded while the other is planar. The virus envelope contains so-called "spikes" protuberances that are formed by glycoprotein G. These protuberances are absent from the planar end of the virion.

Below the shell is a layer of matrix protein M, which covers the core of the virion made of helical ribonucleoprotein , which is composed of RNA and protein N.

The genome consists of unsegmented, linear, single-stranded RNA with negative polarity. The genome has been completely sequenced and is 11, nucleotides in length. The genetic information is packaged as a ribonucleoprotein complex in which the RNA is tightly bound to the viral nucleoprotein. Rabies viruses attach themselves to the cell surface via specific receptors nicotinic acetylcholine receptor , neural cell adhesion molecule 1 and are absorbed through endocytosis by an endosome vesicle that forms.

Inside the endosome, the acidic pH induces the fusion of the endosome membrane and the virus envelope. This causes the capsid to enter the cytosol , disintegrate, and release the genome.

Both receptor binding and membrane fusion are catalyzed by glycoprotein G, which plays an important role in pathogenesis mutants without G are not infectious. After entering the host cell, transcription of the viral genome is initiated by the L polymerase to produce more viral proteins. P is an essential cofactor for polymerase L. Transcription is regulated by cis elements on the viral genome and by protein M. The latter is not only essential for the budding ger. PEP is more than 10 times more expensive to administer than pre-exposure PREP for those who haven't had PREP, and the cost is more than half the per capita annual income of the average citizen.

TEM micrograph with numerous rabies virions small dark grey rodlike particles and Negri bodies the larger pathognomonic cellular inclusions of rabies infection. Any warm-blooded animal, including humans, may become infected with the rabies virus and develop symptoms.

Indeed, the virus has even been adapted to grow in cells of poikilothermic vertebrates [29] [30] though natural transmission has only been documented among mammals. Infected bats , monkeys , raccoons , foxes , skunks , cattle , wolves , coyotes , dogs , mongoose normally yellow mongoose [ How to reference and link to summary or text ] or cats present the greatest risk to humans. Rabies may also spread through exposure to infected domestic farm animals , groundhogs , weasels , bears and other wild carnivores.

Rodents mice , squirrels etc are seldom infected. The virus is usually present in the nerves and saliva of a symptomatic rabid animal.

In many cases the infected animal is exceptionally aggressive, may attack without provocation, and exhibits otherwise uncharacteristic behavior. Transmission between humans is extremely rare. A few cases have been recorded through transplant surgery. After a typical human infection by bite, the virus enters the peripheral nervous system. It then travels along the nerves towards the central nervous system. When the virus reaches the brain , it rapidly causes encephalitis.

This is called the prodromal phase, and is the beginning of the symptoms. Rabies may also inflame the spinal cord producing transverse myelitis. The rabies virus survives in widespread, varied, rural fauna reservoirs. However, in Asia, parts of the Americas and large parts of Africa, dogs remain the principal host.

Mandatory vaccination of animals is less effective in rural areas. Especially in developing countries, pets may not be privately kept and their destruction may be unacceptable. Vaccination campaigns may be expensive, and a cost-benefit analysis can lead those responsible to opt for policies of containment rather than elimination of the disease.

There are an estimated 55, human deaths annually from rabies worldwide, with about 31, in Asia, and 24, in Africa. Recent reports suggest that wild rabid dogs are roaming the streets.

Because much cheaper pre-vaccination is not commonly administered in places like Thailand, the expense for lack of preparation with far more costly post-exposure prophylaxis can hit families hard. Rabies was once rare in the United States outside the Southern states [ How to reference and link to summary or text ] , but as of , raccoons in the mid-Atlantic and northeast United States had been suffering from a rabies epidemic since the s, which was moving westwards into Ohio.

Template:Expand section Because of its potentially violent nature, rabies has been known since B. If a person was bitten by a rabid dog and later died, the owner was fined heavily. Rabies was considered a scourge for its prevalence in the 19th century. Fear of rabies related to methods of transmissions was almost irrational; [4] however, this gave Louis Pasteur ample opportunity to test post-exposure treatments in Template:Expand section.

Rabies is infectious to mammals. Three stages of rabies are recognized in dogs and other animals. The first stage is a one- to three-day period characterized by behavioral changes and is known as the prodromal stage. The second stage is the excitative stage, which lasts three to four days.

It is this stage that is often known as furious rabies for the tendency of the affected dog to be hyperreactive to external stimuli and bite at anything near. The third stage is the paralytic stage and is caused by damage to motor neurons.

Incoordination is seen owing to rear limb paralysis and drooling and difficulty swallowing is caused by paralysis of facial and throat muscles. Death is usually caused by respiratory arrest. As recently as , a new symptom of rabies has been observed in foxes. Probably at the beginning of the prodromal stage, foxes, who are extremely cautious by nature, seem to lose this instinct.

Foxes will come into settlements, approach people, and generally behave as if tame. How long such "euphoria" lasts is not known. But even in this state such animals are extremely dangerous, as their saliva and excretions still contain the virus and they remain very unpredictable. Rabies is an RNA virus. The order and relative size of the genes in the genome are shown in the figure below.

The arrangement of these proteins and the RNA genome determine the structure of the rabies virus. The fusion of the rabies virus envelope to the host cell membrane adsorption initiates the infection process.

The interaction of the G protein and specific cell surface receptors may be involved. After adsorption, the virus penetrates the host cell and enters the cytoplasm. The virions aggregate in the large endosomes cytoplasmic vesicles. The viral membranes fuse to the endosomal membranes, causing the release of viral RNP into the cytoplasm uncoating.

Translation, which involves the synthesis of the N, P, M, G and L proteins, occurs on free ribosomes in the cytoplasm. Although G protein synthesis is initiated on free ribosomes, completion of synthesis and glycosylation processing of the glycoprotein , occurs in the endoplamsic reticulum ER and Golgi apparatus.

The intracellular ratio of leader RNA to N protein regulates the switch from transcription to replication. When this switch is activated, replication of the viral genome begins.