Monday, June 25, 2012

What Is Rabies? What Causes Rabies?

Rabies is a deadly virus that attacks the CNS (central nervous system) and causes acute encephalitis. It is transmitted from animals to humans (zoonotic), most commonly by animal bites - although, there have been cases of humans becoming infected in bat caves after breathing in the air. Rabies infection is nearly always fatal unless prompt treatment is administered before symptoms begin.

Infected people who do not receive post-exposure prophylaxis (preventative treatment after being exposed to the virus) will experience fever, myalgia (muscle pains) and headache, which eventually progresses to brain inflammation, seizures, confusion, paralysis, coma and death.

As soon as the virus reaches the nerves it is incurable. That is why any suspicious animal contact should be treated immediately with RIG (rabies immunoglobulin) injections, antibiotics and rabies vaccine. The incubation period for rabies - how long it takes from initial infection to the onset of symptoms - is usually about 4 to 8 weeks long, in some cases as little as one week and as long as a whole year.

Over 55,000 people die from rabies worldwide annually, 95% of them in Asia and Africa. Most human deaths occur after a dog bite, between 30% and 60% of them are children aged less than 15 years. In the majority of cases, these bites go unreported and are unrecognized by their parents and health officials, resulting in a much higher risk of complications and deaths among children, compared to adults. It is likely the total number of deaths in many parts of the world is much higher than official estimates (we do not know how many undiagnosed deaths there are globally).

According to Medilexicon's medical dictionary:

Rabies is Highly fatal infectious disease that may affect all species of warm-blooded animals, including humans; transmitted by the bite of infected animals including dogs, cats, skunks, wolves, foxes, raccoons, and bats, and caused by a neurotropic species of Lyssavirus, a member of the family Rhabdoviridae, that has tropism for the central nervous system and the salivary glands; inhalation infection possbile (aerosolized virus in bat caves, attics). The symptoms are characteristic of a profound disturbance of the nervous system, excitement, aggressiveness, and madness, followed by paralysis and death. In animals, clinical signs are variable, and sometimes drooling and tongue paralysis are the only signs. Transmission of the virus can occur before clinical signs are expressed. Characteristic cytoplasmic inclusion bodies (Negri bodies) found in many neurons aid rapid laboratory diagnosis.


The Latin word rabies means "madness". The Sanskrit word rabhas means "to do violence".

Until 1885, when Louis Pasteur and Emile Roux developed a vaccine, all human cases of rabies were fatal.

The World Health Organization (WHO) says that people most at risk of rabies live in rural areas of Africa and Asia. Approximately 31,000 people in Asia and 24,000 in Africa are thought to die of rabies each year. Dog rabies is responsible for more than 14 million courses of post-exposure treatment to prevent the onset of disease.

The World Health Organization writes:

The economic burden of rabies in the developing world also takes a large toll. The average cost of rabies immunizations after a suspicious animal bite is US$ 40 in Africa, and US$ 49 in Asia. This post-exposure treatment is a major financial burden for most households in these countries, where the average wage is about US$ 1 to US$ 2 per day, per person.

Poor people, especially children, are at highest risk of dog rabies. About 30% to 60% of the victims of dog bites (the primary mode of virus transmission) are children less than 15 years of age. Children often play with animals and are less likely to report bites or scratches.

In areas known for rabies, professionals with frequent exposure to animals (e.g. veterinarians), or who spend a lot of time outdoors (e.g. wildlife specialists or researchers), particularly in rural areas, should be vaccinated preventively. This also applies to travelers and hikers who visit areas where bats are commonly found.

What are the signs and symptoms of rabies?

A symptom is something the patient senses and describes, while a sign is something other people, such as the doctor notice. For example, drowsiness may be a symptom, while dilated pupils may be a sign.

The period between initial infection and the onset of first symptoms (incubation period) can take from four to eight weeks, and sometimes over a year. The further the bite is from the head, the longer the incubation period tends to be.

The first symptoms to appear are flu-like ones, including fever, headache and fatigue. There will be tingling and/or pain at the bite site, as well as anorexia (loss of appetite).

Two possible types of rabies can develop; furious rabies or dumb rabies.

. Symptoms of furious rabies:
  • progressive anxiety and agitation.
  • stiff neck
  • seizures
  • overproduction of tears and saliva (end stage)
  • convulsions
  • dilated pupils
  • photophobia - abnormal sensitivity to light
  • thermophobia - abnormal sensitivity to temperatures
  • hydrophobia - drinking water becomes increasingly difficult. When the patient tries to drink the throat muscles and the diaphragm go into a spasm. Eventually it becomes so bad that just the sound or sight of water can bring on spasms.
  • insomnia
  • partial paralysis
  • delusions
  • hallucinations
  • alternating periods of mental clarity with severe anxiety, followed by confusion, delusions and hallucinations.
Virtually all patients die within two to ten days after the first symptoms appear. The extremely few who are known to have survived have had severe brain damage.

Symptoms of dumb rabies:

This rarer type of rabies affects the spinal cord. The patient becomes progressively paralyzed, until the lungs and heart do not work anymore. According to the National Health Service (NHS), UK, about a week after severe symptoms develop patients go into coma, and then die.

A patient with dumb rabies will experience confusion, anxiety, agitation, headache, hallucinations, hydrophobia, excessive salivation (overproduction of spit), partial paralysis which spreads and gets worse.

What are the causes of rabies?

The rabies virus is part of the Lyssavirus genus and infects other animals, including humans, through infected saliva, usually from a bite. Much less commonly, a person can become infected if an open wound or mucous membranes have contact with infected saliva. There have been recorded cases of people becoming infected after inhaling the air inside bat caves.

The virus lingers at the bite site for a while and then invades muscle and multiplies, eventually entering nerve endings and making its way to the central nervous system (spine and brain). From the central nervous system the virus spreads to vital organs and glands, such as the kidneys, lungs and salivary glands.

Dogs are still the main rabies carriers in Africa and Asia and are responsible for the majority of human infections and subsequent deaths worldwide, according to WHO (World Health Organization). Over the last decade bat rabies has been emerging as a problem in Europe and the Americas. Since 2003, wild bats have overtaken dogs as the main cause of human infection in South America.

The World Health Organization says that "Human rabies deaths following exposure to wild foxes, raccoons, skunks, jackals and wolves are very rare. Livestock, horses and deer can become infected with rabies, but although they could transmit the virus to other animals or people, this rarely occurs." The Centers for Disease Control and Prevention (CDC), USA, says that beavers, coyotes, monkeys, and woodchucks may also become infected and transmit to humans.

Pets and farm animals, such as cats, cows, dogs, ferrets, goats, horses and rabbits can become infected and there is a risk of transmission to humans. In most developed nations this risk is extremely small.

How is rabies diagnosed?

A PCR (polymerase chain reaction) or viral culture on brain samples after death can help diagnose rabies.

Taking skin samples before death and analyzing them can help in reaching a reliable diagnosis.

Taking samples of saliva, urine or cerebrospinal fluid is a less sensitive way of testing for rabies. Inclusion of Negri bodies, which if detected are 100% diagnostic for rabies are only found in 80% of analyzed samples from infected patients.

If a human is bitten by an animal, there is no way rapid of finding out whether they have been infected.

An animal suspected of rabies can be captured and monitored for 5 to 10 days. If no signs or symptoms are detected during this period, the animal does not have rabies, and the human who was bitten by that animal can stop receiving treatment.

What is the treatment for rabies?

Anybody who is bitten by an animal that might have rabies needs to see a doctor immediately and receive treatment. If left untreated and symptoms eventually develop, the individual will die. In fact, even if you know the animal does not have rabies and you are bitten, see a doctor anyway as you may still need some other kind of treatment, and also a tetanus jab.

After being bitten place the wound under a running tap and clean it thoroughly (use soap) for about five minutes. Exposed mucous membranes should be well rinsed with water. A virucidal antiseptic such as povidone-iodine, iodine tincture, aqueous iodine solution or alcohol (ethanol) should be applied after washing. If there is not profuse bleeding, do not try to close up or stitch the wound. Get medical help as soon as you can.

  • If the patient was not vaccinated before being bitten the doctor will inject HRIG (human rabies immunoglobulin), mostly around the site of the wound and partly by deep intramuscular injection.

    Intramuscular injection should not be given into the gluteal area (buttocks) because it is linked to vaccination failure (injection must go into muscle, not fat).
  • The CDC (Centers for Disease Control and Prevention) says patients should receive 1 dose of HRIG and 4 doses of rabies vaccine over a 14-day period. The HRIG dosage should be no more than 20 units per kilogram of body weight. The vaccination site should be distant from the HRIG injection site. In infants (babies) the lateral thigh should be used for injection. If the patient is an adult, the arm can be used to give the vaccine.
  • The initial rabies vaccine should be given immediately, with the other doses on days 3, 7 and 14 after the first.
  • If a patient has already received pre-exposure vaccination, they should only receive the post-exposure vaccinations on days 0 and 2, and not be given the HRIG injections.
The National Health Service (NHS), UK warns all British people who have been bitten abroad and cannot get the vaccine in that country to return to the UK immediately for medical treatment.

If the patient has symptoms - all the medical team can do is make the him/her as comfortable as possible. Death is virtually inevitable.

How is rabies prevented?

Travelling - anybody travelling abroad into an area with rabies and know they will be in contact with possibly infected animals - for example, exploring bat caves - should have a pre-exposure anti-rabies vaccination. The vaccination gives the individual more time to get medical help; it does not offer full protection, but slows the virus down.

Contact with animals - do not touch unknown animals, no matter how friendly, furry, pretty and cute they seem. This is especially the case in areas that are not rabies-free. The National Health Service, UK informs that an early sign of rabies in an animal is unusual tameness.

Vaccinating animals - if you do not live in a rabies-free country or area, make sure your pets and farm animals' vaccinations are up-to-date. If you are not sure, talk to a veterinarian (animal doctor).

The World Health Organization writes:

The most cost-effective strategy for preventing rabies in people is by eliminating rabies in dogs through animal vaccinations. A lack of awareness of the effectiveness and feasibility of this prevention approach hinders elimination of human cases. As shown in several countries - such as Japan and Malaysia - elimination of rabies in dogs can result in elimination of transmissions to people and other animals. Preventing human rabies through control of domestic dog rabies is a realistic goal for large parts of Africa and Asia.

Prevention of human rabies must be a community effort involving both veterinary and public health services. Rabies elimination efforts that focus on mass vaccinations of dogs are financially justified by the future savings of discontinuing post-exposure preventive treatment for people.

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