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Rabies



Rabies Causes


The virus that causes Rabies is known as Lyssavirus, a genus of RNA viruses that comprises the Australian bat lyssavirus, Duvenhage virus, Lagos bat virus, Aravan virus, Mokola virus and West Caucasian bat virus. This virus is generally present in the saliva of infected animals, and transmitted to others by bites. All warm-blooded mammals can potentially get the virus; while there are some that may serve as natural reservoirs of the virus. Commonly, humans are exposed to the rabies virus when bitten by an infected animal. Transmitted through the mucous membrane or the skin, the virus then replicates in the striated muscle cells at the bite site, rapidly spreading to the Central Nervous System and ultimately replicating in the brain. The virus then spreads through the nerves and into the other tissues, including the salivary glands. Very rarely, the rabies virus may also be transmitted through airborne droplets and infected tissue transplants.


Rabies Definition


Rabies is a viral zoonotic neuro-invasive infection that often causes an inflammation of the brain (a condition known as acute encephalitis). Rabies is from the Latin word “rabies” meaning “rage, fury, or madness”. Rabies can be fatal when affecting non-vaccinated humans, especially after neurological symptoms have occurred. However, the effects can be curbed if the patient is promptly vaccinated shortly after exposure to the virus. When the disease becomes symptomatic, however, it becomes invariably fatal.


Rabies Diagnosis


In humans suspected of rabies, differential diagnosis almost always includes any known cause of encephalitis. Herpes simplex virus type 1, varicella-zoster virus, and less commonly, a number of enteroviruses need to be ruled out. A PCR (polymerase chain reaction) test may be done to assess cerebrospinal fluid, viral culture, and of course, serology. Currently, inexpensive rabies diagnostic methods are being developed in clinical research settings. Among those evaluated is a technique using light microscopy, which is said to be ten times cheaper than standard rabies tests but better able to diagnose the virus.


Rabies Symptoms and Signs


Generally, an animal infected with the rabies virus becomes excessively aggressive, attacks without provocation, and demonstrates uncharacteristic behavior. In infected humans, the rabies virus invades the peripheral nervous system and ultimately affects the CNS. When it reaches the brain, encephalitis or brain inflammation rapidly occurs. At this point, neurological symptoms appear and treatment is useless. There is an interval between infection and the onset of the first symptoms, which may last from 2 to 12 weeks, but may last for as long as 2 years. The first tell-tale signs are flu-like symptoms. Soon after the initial onset, these symptoms rapidly expand to paralysis, anxiety, cerebral dysfunction, insomnia, agitation, confusion, abnormal behavior, hallucinations, paranoia, terror, and delirium, among others. During the late stages, typical signs include an overproduction of excess saliva and tears. A patient may also lose the ability to speak or swallow, which can lead to hydrophobia due to the paralysis of both the jaw and the throat. The “foaming at the mouth” symptom which has been popularly associated with the disease is a result of the patient's inability to swallow their own saliva for long periods. The excess saliva is accumulated in the mouth until it overflows. Within two to ten days from the onset of symptoms, death almost invariably occurs. In isolated cases, a very small number of humans were known to survive the disease, but with the exception of one recorded case, all were left with severe brain damage.


Rabies Treatment


Rabies can be prevented through vaccination in both humans and other animals. Treatment after the virus has been transmitted is known as P.E.P. or post-exposure prophylaxis. This has proven to be successful if administered promptly, usually within 6 days after exposure. Rinsing the wound thoroughly with soap or virucidal antiseptic can reduce the number of viral particles. In addition, exposed mucous membranes must also be washed thoroughly. Patients are treated with a dose of immunoglobulin and five doses of rabies vaccine at the bite site. The rest is introduced intramuscularly away from the region of the bite. The first vaccine dosage must be given shortly after exposure, with additional doses injected on the third, seventh, fourteenth, and twenty-eight day after the first.


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