Hydrophobia

Rabies is a very serious viral infection that targets the brain and nervous system. It is spread by animals to humans.Once the symptoms of rabies have developed, the condition is almost always fatal.

The symptoms of rabies include:

  • numbness at the bite site
  • high temperature (fever) of 38ºC (100.º4) or above
  • hydrophobia - an irrational fear of water
  • hallucinations - seeing or hearing things that are not real

How rabies is spread

Rabies is a zoonotic infection, which means it is passed to humans by animals.

If an infected animal bites or scratches a human, the rabies virus can spread to the brain through the nervous system.

Rabies can also be spread by an infected animal's saliva coming in to contact with a cut or graze on a person's skin. However, this is much less common.

Most mammals can carry the rabies virus, but the majority of cases result from being bitten by an infected dog.

How common is rabies?

There are an estimated 55,000 cases of rabies each year worldwide. Most cases occur in the developing world, particularly in Africa and Asia. Half of all rabies cases occur in India.

However, a small number of cases continue to be reported in developed countries, particularly in North America. Most of these cases are the result of a person being bitten by a wild animal rather than a dog.

As a result of strict quarantine laws when transporting animals, and more recently,the EU Pet Passport System Ireland is cosidered rabies free. However,there is an increasing prevalence of a rabies-like virus in our bat population and a person was flown back for treatment for rabies to Northern Ireland in 2009 after working for an animal charity in South Africa.

Vaccination

A number of vaccines can be used to prevent a rabies infection developing. Routine vaccination is usually only recommended if you are travelling to a part of the world that is known to have high levels of rabies, and your access to medical care is likely to be limited.

Most people going on a standard holiday (as opposed to trekking or living and working in rural areas) will not need a rabies vaccine.

Treating rabies

There are currently no effective treatments for rabies. Therefore the only effective option is to try to prevent the rabies virus spreading from the site of the bite to the brain and nervous system. This is done by cleaning out the wound and administering several doses of the rabies vaccine and a type of blood product known as immunoglobulin, which contains rabies-fighting antibodies. This is known as post-exposure prophylaxis.

If you are travelling in a part of the world that is known to have high levels of rabies and you are bitten by an animal, seek immediate medical attention so that you can receive post-exposure prophylaxis.

Outlook

Once the symptoms of rabies have begun, it almost always leads to death. Rabies has the highest death rate of any type of viral infection. To date, there has only been one reported case of person surviving a rabies infection.

Bat rabies

There are two strains of rabies-like viruses found in bats across northern Europe, known as European Bat Lyssaviruses (EBLVs) 1 and 2. They are commonly referred to as bat rabies.

It is rare for these viruses to infect other animals and the risk of infection to humans is thought to be low. In the UK, there have been seven recorded cases of EBLV in bats and, in 2002, an unvaccinated bat handler in Scotland died from the infection.

The incubation period

The incubation period is the time that it takes for symptoms to develop after a person is infected with a virus. The incubation period for rabies is usually between three and 12 weeks, although it can be as short as four days or as long as 19 years. However, it would be highly unusual for an incubation period to last for more than a year.

The length of the incubation period is important because this is the only period in which the rabies vaccine can prevent a rabies infection.

The closer the bite is to your brain, the shorter the incubation period. For example, a bite to your face, head or neck will have a shorter incubation period than a bite to your arm or leg.

Initial symptoms

The initial symptoms of rabies are often non-specific, and it can be easy to mistake them for other, less serious types of infection. They include:

  • a high temperature (fever) of 38ºC (100.4ºF) or above
  • chills
  • a general feeling of uneasiness - 'feeling out of sorts'
  • fatigue (extreme tiredness)
  • insomnia - problems sleeping
  • lack of appetite
  • headache
  • irritability
  • anxiety 
  • sore throat
  • vomiting (being sick)

Around half of people will also experience pain, itchiness and a tingling sensation at the site of the bite.

Advanced symptoms

The initial symptoms of rabies last for two to 10 days, before more severe symptoms start to develop. There are two types of advanced rabies symptoms. They are known as:

  • furious rabies, which account for 4 out of 5 cases
  • dumb rabies, which accounts for the remaining cases

Furious rabies

Furious rabies is characterised by episodes of increasingly bizarre and hyperactive behaviour, separated by periods of relative calm. During these episodes, a person may have some, or all, of the following signs and symptoms:

  • aggressive behaviour, such as thrashing out or biting
  • agitation
  • hallucinations - seeing or hearing things that are not real
  • delusions - believing things that are obviously untrue
  • excessive production of saliva
  • high temperature (fever)
  • excessive sweating
  • the hair on their skin stands up
  • a sustained erection (in men)

Around 50-80% of people with furious rabies will also develop hydrophobia (a fear of water). This initially begins as a pain in the throat or difficulty swallowing. On attempting to swallow, the muscles in the throat go into a brief spasm that lasts for about five to 15 seconds. Subsequently, the sight, sound or even the mention of water (or any other liquid) will trigger further spasms.

The affected person will then fall into a coma before dying, usually within 12 days, as a result of heart or lung failure.

Dumb rabies

Dumb rabies is characterised by increasing muscle weakness, loss of sensation and paralysis (an inability to move one or more muscles). This usually begins in the hands and feet before spreading throughout the body.

Hydrophobia is unusual in cases of dumb rabies, although muscles other than those in the throat may go into spasm. As with furious rabies, someone with dumb rabies will fall into a coma and eventually die from heart or lung failure.

When to seek medical advice

If you are in a part of the world that is known to be affected by rabies, always seek medical advice as soon as possible if you are bitten or scratched by an animal, particularly a dog.Always seek medical attention if you are bitten by a bat (although this situation is rare), or if you suspect that someone in your care who is unable to report a bite may have been bitten. For example, if you find a bat in a young child's room. 

Symptoms of rabies in an animal

As with humans, the symptoms of rabies in an animal follow a number of stages.

The first stage is marked by initial non-specific symptoms, such as:

  • loss of appetite
  • high temperature
  • change in normal behaviour, such as appearing unusually tame around strangers

The second stage is known as the 'mad dog' stage and usually lasts for two to four days. It is characterised by very aggressive and erratic behaviour, such as:

  • constantly barking or growling
  • no fear of normal, natural enemies
  • attempting to attack and bite anything that comes near, including inanimate objects

The final stage, known as the 'paralytic' stage, lasts for two to four days and is characterised by symptoms such as:

  • the animal appearing to be choking
  • foaming at the mouth
  • the dropping of the lower jaw (in dogs)
  • paralysis of the jaw, mouth and throat muscles 
Anxiety
Anxiety is an unpleasant feeling when you feel worried, uneasy or distressed about something that may or may not be about to happen.
Coma
A coma is a sleep like state when someone is unconscious for a long period of time.
Delusions
If someone is suffering from delusions, they have lost touch with reality and may experience hallucinations.
Fever
A fever is when you have a high body temperature (over 38ºC or 100.4ºF).
Hallucinations
Hallucinations are a sensory experience in which a person sees, hears, or feels something or someone that isn't really there.
Loss of appetite
Loss of appetite is when you do not feel hungry or want to eat.
Lungs
Lungs are a pair of organs in the chest that control breathing. They remove carbon dioxide from the blood and replace it with oxygen.
Pain
Pain is an unpleasant physical or emotional feeling that your body produces as a warning sign that it has been damaged.
Panic
To panic is to be quickly overcome with a feeling of fear or worry.

The rabies virus belongs to a group of viruses called lyssaviruses, which exist in warm blooded animals. The disease is transmitted through infected saliva.

Rabies can spread to humans from infected animals, usually dogs, through a bite or a lick to broken skin or the eye. Domestic dogs and cats can become infected with rabies if they come into contact with wild animals that have the disease, such as foxes, wolves, jackals, skunks, mongooses, raccoons and bats.

The rabies virus remains at the site of the bite and multiplies in the muscle cells near to the bite wound, before entering the body. The virus enters the nerve endings and travels to the spinal cord and brain (the central nervous system). Once the virus is in the central nervous system, it will spread to the salivary glands, lungs, kidneys and other organs.

Incubation period

The incubation period (the time between the bite and the onset of symptoms) will vary depending on the distance of the bite from the head.

If a bite occurs near the head, such as the neck or face, then the rabies virus has a shorter journey to travel to the brain. So the incubation period is shorter than in bites to the legs and feet.

Children, particularly young children, tend to have relatively a short incubation period than adults. This is because children are shorter, so their upper body is closer to the ground, making them more vulnerable to bites higher up the body.

Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.
Disease
A disease is an illness or condition that interferes with normal body functions.
Kidneys
Kidneys are a pair of bean-shaped organs located at the back of the abdomen, which remove waste and extra fluid from the blood and pass them out of the body as urine.
Lungs
Lungs are a pair of organs in the chest that control breathing. They remove carbon dioxide from the blood and replace it with oxygen.
Onset
The onset is the beginning or early stages of a condition or disease.
Spinal cord
The spinal cord is a column of nervous tissue located in the spinal column. It sends messages between the brain and the rest of the body.

Animals that carry rabies

In developing countries, particularly those in Africa and Asia, the majority of rabies in humans happen when people are bitten by dogs. In South America, bats are another significant cause.

In developed countries, all warm blooded animals can carry rabies. However, some species are more commonly infected than others. For example:

  • bats
  • raccoons
  • foxes
  • jackals
  • wolves

Due to the devastating nature of a rabies infection, treatment should always start whenever there is a risk that a person has contracted the disease. It is dangerous to delay treatment until a diagnosis has been confirmed.

If possible, the animal that is suspected of having rabies should be captured and watched for five to 10 days. After this time, if no rabies symptoms are observed, it can be assumed that the animal does not have rabies and treatment can be stopped. If the animal is killed or dies, its brain can be examined for the presence of the rabies virus.

Tests

Tests that can be used to confirm a diagnosis of rabies in people who are experiencing symptoms associated with rabies include:

  • skin biopsy - a small sample of skin is removed and checked for the presence of the rabies virus
  • saliva test - a sample of saliva is tested for the presence of the rabies virus
  • lumbar puncture - a needle is used to remove a small sample of cerebrospinal fluid (CSF), which can be checked for the rabies antibodies (CSF is the fluid that surrounds your brain and spinal cord)
  • blood tests - your blood is checked for the rabies antibodies
Antibody
Antibodies and immunoglobins are proteins in the blood. They are produced by the immune system to fight against bacteria, viruses and disease.
Brain
The brain controls thought, memory and emotion. It sends messages to the body controlling movement, speech and senses.

Two different types of treatment can be used in cases of rabies:

  • post-exposure prophylaxis - treatment is given to prevent a rabies infection taking place
  • supportive care - treatment is given to make someone with an active rabies infection feel as comfortable as possible

These two types of treatment are described in more detail below.

Post-exposure prophylaxis

Post-exposure prophylaxis consists of three stages:

  • cleaning the wound
  • administering rabies immunoglobulin - this special preparation of antibodies protects against the rabies virus
  • administering a course of the rabies vaccine

Cleaning the wound

Immediately after being bitten, you should:

  • wash the wound thoroughly with soap and water under a running tap
  • use antiseptic or alcohol to clean the wound, apply ethanol, tincture or aqueous solution of iodine, if available
  • leave the wound open - do not try to stitch it because this could expose your nerve endings to the rabies virus
  • go to the nearest hospital or medical centre and explain that you have been bitten

Where possible, the animal that bit you should be captured and observed for five to 10 days, and you should inform the police and relevant authorities.

Rabies immunoglobulin

After being bitten, you should be given an injection of rabies immunoglobulin as soon as possible. This should help to neutralise the virus and prevent it from travelling to your nervous system. The immunoglobulin works by stimulating the production of antibodies that can stop the virus from spreading.

Aside from some temporary soreness at the site of the injection, rabies immunoglobulin does not usually cause any side effects.

Vaccination

The length of your course of vaccinations will depend on whether you have previously been vaccinated.

If you have never been vaccinated, you should receive five doses of the vaccine. The first dose is given at the beginning of the treatment, followed by four further doses which are given three, seven, 14 and 30 days after the start of treatment.

If you have previously been vaccinated, you should receive two doses of the vaccine. The first dose is given at the start of your treatment and it will be followed by the second one three days later. The doses are given by injection into the shoulder muscle.

A common side effect of the rabies vaccine is redness, swelling and pain at the site of the injection that occurs 24 to 48 hours after the injection has been given.

Choice of vaccine

There are three types of rabies vaccine:

  • human diploid cell vaccine (HDCV), which is created by using samples of human cells
  • purified chick embryo cell rabies vaccine (PCEC), which is created by using samples of chicken embryos 
  • nerve tissue vaccine is created by using samples of nerves taken from animal brains

The World Health Organisation (WHO) recommends that only HDCV or PCEC should be used.

This is because safety concerns have arisen over the nerve tissue vaccine. Researchers have found that this type of vaccine has a 1 in a 650 chance of causing serious complications, such as muscle paralysis, which can result in permanent disability.

A small number of countries have not followed WHO's recommendation and still use the nerve tissue vaccine. They include:

  • Argentina
  • Bangladesh
  • Burma
  • Pakistan
  • Peru

Also, in many developing countries the HDCV or PCEC vaccine may only be available if you are willing to pay for private treatment.

If you are offered the nerve tissue vaccine, it is recommended that you should refuse and ask for one of the alternative vaccines.

Supportive treatment

If a person who is infected with rabies is not treated and they have developed symptoms, rabies is said to be established.

In this situation, there is nothing that can be done apart from keeping them comfortable. This is usually done by using powerful tranquilisers and sedatives to keep them free from physical pain and emotional upset.

To date, there have been no reported cases of human-to-human transmission of rabies. However, it is theoretically possible, so anyone who has been exposed to the bodily fluids of someone with a rabies infection may be advised to have post-exposure prophylaxis as a precaution.

Remember, you don't have to be bitten to get rabies

A scratch that is licked by an infected animal is enough to cause rabies. 

Rabies vaccination

Rabies vaccination is recommended for the following groups of people:

  • laboratory workers who may be required to handle samples of the rabies virus
  • people whose jobs mean that they regularly come into contact with animals that have been imported from abroad, such as people working at zoos, ports, airports and animal quarantine centres
  • veterinary and technical staff who work for the government
  • people who regularly handle bats
  • health workers who treat anyone with a suspected or confirmed rabies infection
  • people who are going to be working abroad in a job that brings them into contact with animals

Vaccination is also recommended for:

  • any person travelling or living in parts of the world where the risk of rabies is moderate to high (see box, left) for more than a month, unless there is access to prompt, safe medical care
  • any person travelling to parts of the world where the risk of rabies is moderate to high for less than a month, and their travel activities could increase their risk of being exposed to rabies, or they have limited access to medical care

The rabies vaccination consists of three injections over the course of a month. Booster injections every two years are needed for continued protection after that. Therefore you will need to allow at least a month to finish the course before you depart.

The injections are not painful and are given into the skin on your upper arm. There are usually no serious side effects.

You will have pay for a course of the vaccine, either at your GP surgery or at a travel clinic. As a general rule, pregnant women are usually advised to avoid rabies vaccinations. The vaccine is usually only recommended if the potential risk of exposure to rabies is thought to be high and there is limited access to medical care.

Advice to travellers

When travelling in countries that are not rabies-free, do not touch any unknown animals and educate your children about the dangers of petting unknown animals. This is particularly true for animals that appear unusually tame because this is an early sign of the rabies virus in animals.

Examine your children daily for cuts and scratches and ask them how they got them. Make sure they know that being bitten by an animal is dangerous and they need to tell you about it.

Quarantine and the EU Pet Passport system.

To keep countries rabies-free, it is important that there are strict public health measures to control stray animals, such as foxes. It is also important that the movement of potentially infected animals across borders into uninfected regions is controlled by strictly enforcing quarantine regulations. Animals that do not have a licence should not be brought into Ireland.

The EU Pet Passport system is a system that allows pet dogs, cats and ferrets from certain countries to enter Ireland without going into quarantine, as long as they have been vaccinated. It also means that people in Ireland can take their dogs, cats and ferrets to other European Union (EU) countries and return with them to Ireland.

Immunoglobulin
Immunoglobulins (antibodies) are types of proteins in the body that fight off infection.
Vaccination
Vaccination, or immunisation, is usually given by an injection that makes the body's immune system produce antibodies that will fight off a virus.

Areas of high risk

Rabies is a disease that can be found throughout the Middle East, Africa, Asia, Central America and in some parts of Eastern Europe. The countries with the highest risk of rabies are:

  • Colombia
  • Cuba
  • Dominican Republic
  • Ecuador
  • El Salvador
  • Guatemala
  • India
  • Mexico
  • Nepal
  • Pakistan
  • Peru
  • Philippines
  • Sri Lanka
  • Thailand
  • Turkey
  • Vietnam

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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