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Updated 13 February 2013

Rabies

Rabies is a fatal viral encephalitis (brain inflammation). The disease occurs in wild and domestic mammals and occasionally in humans.

1

Summary

  • Human rabies occurs in South Africa. There is a current outbreak of rabies in domestic animals in Gauteng, specifically in the Southdale, Lenasia, Eldorado and Dobsonville areas.
  • Rabies is always fatal once symptoms appear.
  • Human rabies can almost always be prevented, even after exposure. Awareness and prompt preventative measures are essential.
  • Although rabies occurs in a number of Southern African wild animal species, transfer to humans occurs via the bite of a domestic dog or cat in more than 90% of cases.
  • Symptoms of rabies in an animal include abnormal behaviour, excessive salivation and paralysis.
  • Symptoms of rabies in a human include abnormal behaviour, fever, anxiety, severe muscle spasms and an inability to swallow.
  • A dog or cat bite should always receive medical attention. If there is a risk of rabies, rabies immune globulin and a course of vaccination must be given.

Definition

Rabies is a fatal viral encephalitis (brain inflammation). The disease occurs in wild and domestic mammals and occasionally in humans.

Alternative names

Hondsdolheid (Afrikaans)

Cause

Rabies is caused by the rabies virus and other  related rabies-like viruses. Once the virus has entered the body, it enters peripheral nerves and is carried towards the brain. The virus multiplies in the brain, causing brain dysfunction and ultimately death. The disease is spread from animal to animal, and occasionally from animals to humans. Human to human transmission is theoretically possible, but extremely rare.

Who gets it and who is at risk?

People usually get rabies after a bite from a rabid animal. In South Africa, most cases of human rabies follow dog or cat bites. Dog or cat rabies occurs in Gauteng, KwaZulu-Natal, the Eastern Cape, Mpumalanga and Lesotho, and this is also where most human cases occur. About 600-700  cases of animal rabies (dogs, cats, cattle, yellow mongoose) and 20-30 diagnosed cases of human rabies occur each year in South Africa. A large proportion of the human rabies cases are in children.

People who work with animals such as veterinarians, game-rangers and animal welfare organisation workers are at high risk for exposure to rabies.

Rabies occurs in some indigenous wild animals, such as the bat-eared fox (Namibia and North-Western Cape), black-backed jackal (Northern Province) and yellow mongoose (Highveld and Karoo). These animals seldom come into contact with humans and account for very few human rabies cases. However, domestic animals such as cattle and cats are sometimes infected by bites from these animals. Bats are a very uncommon source of human rabies in South Africa.

Note that there are no animals which “carry” rabies. Any animal infected with the rabies virus will itself get sick and die. In order to transmit the virus to another animal or human, the infected animal must already be in the early stages of the disease. Abnormal behaviour is the most  obvious sign of rabies in an animal -  a simple guideline is “when a wild animal becomes tame or a tame animal becomes wild” – for example  when a wild animal appears to have lost its fear of humans and is unusually approachable, or a previously tame and docile animal becomes aggressive without provocation. Physical signs of rabies in an animal include excessive salivation (drooling) because of loss of the normal ability to swallow, and partial paralysis.

The saliva of a rabid animal contains a high concentration of the rabies virus. The virus is therefore usually transmitted by biting, which forces saliva through skin and into muscle tissue. The virus can also be transmitted if a rabid animal licks broken skin (scratches, sores, eczema, etc.) or a mucosal surface which is thin and wet, such as the eye, mouth or genitals. The virus cannot pass through unbroken, healthy skin.

Typically, rabies exposure might occur when a person tries to help a sick dog or other animal, or when a person is subject to an unprovoked attack by a stray dog or cat, in a high-risk area, such as the southern suburbs of Johannesburg or rural KwaZulu-Natal. Other regions of the world where human rabies is common (more common than in South Africa) are India, Thailand and South-East Asia, Central and South America, and several African countries. Travellers to these destinations should be aware of the risk of rabies, which is usually secondary to dog bites.

Unusual ways that rabies has been acquired

  • Rabies has been acquired after people have entered caves heavily inhabited by bats. Bats infected with rabies can aerosolise the virus by sneezing. It is believed that aerosolised virus, in high concentration, can access nerve endings in the nose and then reach the brain by travelling up the olfactory nerve.
  • A laboratory worker acquired rabies after breakage of a vial of cultured rabies virus inside a high-speed centrifuge. It is believed that highly concentrated aerosolised virus was inhaled, with the route of infection through the nose, as in the example above.
  • An outbreak of rabies occurred in kudu in Namibia, spreading from animal to animal. This was attributed to infected saliva being deposited on thorny branches during feeding. Buck subsequently feeding on the same branches were inoculated with the virus from the tips of contaminated thorns.
  • Several cases of rabies have occurred following corneal transplants, mostly on the Indian subcontinent. This has occurred when persons have died of unrecognised rabies and their corneas donated to a cornea bank.

Symptoms and signs

Rabies in a person typically begins 20-60 days after exposure. (Bites to the head and body are followed more quickly by rabies than bites to the limbs.) However, rabies can occur months or even years after exposure, often when the exposure incident is long forgotten. Early symptoms of rabies are vague, and include fever, headache, sore throat, fatigue, loss of appetite, nausea and vomiting. An early clue is tingling or pain and intense itchiness at the site of the animal bite, even when the wound has already healed. The person may also be anxious and struggle to sleep.

 These symptoms rapidly progress to a state of agitation, outbursts of aggression and wild, uncontrollable behaviour and muscle spasms. In between these episodes the person may be clear-headed, though fearful. These distressing symptoms are worsened by loss of the ability to swallow, excessive salivation and seizures, sparked off by any stimulus such as a loud noise, a draught of air or another person’s touch. At this stage, a characteristic sign of rabies is “hydrophobia” or fear of water. This is triggered by being offered water to drink, in response to which intense, painful spasms of the muscles of the throat, neck and diaphragm occur, accompanied by extreme fear. (The basis of this reaction is not understood, but one theory is that the disturbed brain initiates an inappropriate “drowning response” at the sight of water.)

Death is inevitable in these cases, and will occur within a few days. The usual cause of death is cessation of breathing and heart function during a seizure. Sometimes people with rabies do not have these dramatic symptoms, but gradually become completely paralysed and slip into a terminal coma. This alternative form of rabies is more difficult to recognise.

Diagnosis

Rabies is usually recognised by the history of a bite or exposure, symptoms and signs. However, the disease is rare, and if you do not report a recent dog bite, it can be difficult for a health care professional to identify rabies in the early stages. Often the disease is only confirmed after death. By law, a post-mortem examination is required in cases of suspected rabies. Typical changes in the brain will confirm the diagnosis. If rabies is suspected before the person dies, an attempt may be made to identify the virus in a skin sample, or in cells from the cornea of the eye. It is possible to grow the virus from saliva in specialised laboratories with special safety facilities. A blood test can be done to detect antibodies (proteins produced by the immune system that attack harmful invasive organisms or substances) to the rabies virus, but this will only become positive once the disease has progressed. PCR testing on saliva a specimen also now exists, which can detect rabies virus, but is only used in consultation with specialists in this field. In South Africa, all rabies testing for humans is done at the National Institute for Communicable Diseases in Johannesburg.

Prevention

Rabies Prevention

  1. Domestic pets must be vaccinated. Dogs and cats should be vaccinated at 3 months of age, with a booster at 9 months, and then every 3 years afterwards. In high risk areas, annual revaccination is recommended.   
  2. Avoid stray animals, animals that are behaving strangely or that appear sick. Wild animals may appear unusually tame.
  3. If exposure occurs, under no circumstances must treatment be delayed, pending availability of a laboratory diagnosis. The risk of exposure to rabies can be categorized as either 1 (low), 2 (medium) or 3 (high) as follows;

 

Risk

Type of Exposure

Action Necessary

1

Touching/feeding animal

Licking of intact skin

Nil if history is reliable

If unreliable history treat as medium risk exposure

2

Nibbling uncovered skin

Superficial scratch, no bleeding

Licking of broken skin

Treat wound (flush with water, apply 70% alcohol or iodine solution; avoid suturing)

Administer vaccine

Do not administer rabies immunoglobulin

 

3

Bites/scratches penetrating the skin and drawing of blood

Licking of mucous membranes

Treat wound

Administer:

  • rabies vaccine
  • rabies immunoglobulin
  • anti-tetanus vaccine
  • antibiotic treatment

 

Post-Exposure Treatment

All high risk exposure must receive rabies immunoglobulin (RIG) and rabies vaccines. 

Vaccines

Rabies vaccines available in South Africa, are purified, inactivated and safe, and can be used in pregnant females and infants. The dose of vaccine varies depending on the manufacturer. The vaccine is administered at Day 0,3,7,14 and 28. A double dose of vaccine on Day 0 is recommended for any patient that is first seen > 48 hours after exposure or any immunocompromised patients.

Human rabies can almost always be prevented, even after exposure. Deaths from rabies in South Africa are unnecessary, and are caused by ignorance of the disease on the part of the public and health care professionals, or lack of access to health care.

People who have occupations involving frequent contact with live animals (especially veterinarians, game-rangers and animal welfare workers) should be vaccinated at the beginning of their careers. Current World Health Organisation recommendations suggest that these individuals that are at high risk for exposure to rabies should receive rabies vaccine boosters (2 doses, at 0 and 3 days) every two years after the a full course of immunization. It is currently not recommended that rabies antibody titres be measured, but rather that prophylactic vaccination be given to all high risk individuals every two years after their primary series of vaccines. However, if these individuals are  subsequently exposed to rabies they will  need further  booster vaccinations i.e. 2 doses of vaccine immediately after the exposure.

After an animal bite, the animal should be captured if at all possible, while avoiding further injuries to others. The state veterinary services should be called in to capture any sick or dangerous animal. An obviously sick animal may be immediately euthanased by a veterinarian in order to confirm or exclude rabies. Alternatively, the animal may be kept under observation.

Rabies immune globulin and rabies vaccine are available at most major hospitals and through district surgeons. The immune globulin is injected around the wound to try to inhibit the virus’s access to the nervous system. The remainder is injected into the arm, usually the one opposite to the side where the vaccine is to be given. A dose of vaccine must be given immediately, then a further four doses of vaccine three, seven, 14 and 28 days later. The vaccine must always be given in the upper arm.

The complete rabies preventative treatment as described above will prevent rabies in almost 100% of cases. Treatment should be given as early as possible. However, if a significant risk of rabies is recognised days or weeks or months after an animal bite, a course of rabies vaccination should still be given.

Rabies-free countries (e.g. Great Britain and New Zealand) usually have a strict quarantine period for animals entering the country, in order to avoid importation of the disease.

Treatment

Once a person has symptoms of rabies, there is no cure. At this stage immune globulin, vaccination and anti-viral drugs are of no benefit. A person can be kept alive indefinitely on a life-support system, but no-one has ever made a recovery from rabies. The usual care is to make the patient as comfortable as possible in the face of a painful and fearful death. High doses of painkillers, sedatives and anti-convulsant drugs should be given.

When to call the doctor

  • Seek advice and treatment when you or your child has been bitten by an animal or has been in contact with an animal which behaved abnormally, or subsequently died.
  • Anyone displaying symptoms of rabies will need intensive medical care.

Written by Dr Jane Yeats MBChB, BSc(Med)(Hons)Biochem, FCPath (SA)Virol Specialist and lecturer, Department of Virology, University of Cape Town and Groote Schuur Hospital

Reviewed by Professor Eftyhia Vardas BSc(Hons), MBBCh, DTM&H, DPH, FC Path (Virol), MMed (Virol), Clinical Virologist, Consultant Clinical Virologist, Lancet Laboratories and Department of Medical Virology, Tygerberg Campus, University of Stellenbosch, April 2011

 
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