Bugs – Rabies
Rabies, (AFRIKAANS: “Hondsdolheid”) is also known as “mad dog disease” because the transmission of the disease is most frequently associated with bites by infected dogs. It is also commonly known as Hydrophobia which relates to one of the major symptoms, an inability to swallow in spite of intractable thirst. Numerous campaigns are going on throughout the world to lessen the spread of this horrific disease, known to man since ancient times. Although stray dogs are the main source of human rabies, any warm blooded animal, including bats, can carry the virus. Almost all are themselves killed by the disease within days of showing symptoms. Consequently, following a potentially rabies infected bite, scratch or lick, if the animal survives a period of 10 days it may be taken that it was not rabid at the time of the bite.
Mode of Infection
Mode of Infection
The disease is caused by an RNA virus of the rhabdovirus group. The incubation period from the time of infection until the onset of clinical symptoms may be from days to months, depending on where in the peripheral nervous system the rabies virus is inoculated.
The incubation period ranges from 3 days to 3 years, most commonly between 1 and 3 months. The incubation period is directly related to the extent of the inoculation (bite) and the proximity to the brain. Thus bites on the face and neck are particularly significant and will, in general, be associated with a short incubation period.
In many patients no symptoms occur until the final days of the disease are reached.
The site of the initial inoculation will usually have fully healed and be well forgotten. When the patient begins to experience the first effects of the disease, they may experience fever and headaches and numbness over the original bite site. Following this, patients may complain of anxiety, photophobia, muscular pains and difficulty swallowing.
Like animals, humans may have one of two clinical presentations:
Furious Rabies: (most common variety – 80%)
The patients experience severe muscular spasms which may lead to apnoea, if the respiratory muscles are involved. The patients tend to develop spasm of the pharyngeal muscles which is precipitated by swallowing, the sound of running water or attempts to drink water, cold drafts across the neck or movement.
Paralytic Rabies: Less common variety in humans
Death may be delayed but always occurs. Patients tend to lie quietly and because of the gross hypersalivation, saliva dribbles from their mouths. Some patients with furious rabies may have periods of paralytic symptoms.
Irrespective of the clinical presentation the patient remains conscious of his fate throughout the last awful days.
This disease is endemic in most areas of the world but is very common in the tropics where control of animals is limited. A few island countries are free of the disease.
It remains of great concern on the African continent including rural and urban South Africa.
All age groups are at equal risk but children who have a natural affinity for animals and who often gets bitten on the head and neck are at particular risk. They also often do not tell parents when they have had an encounter with a foreign animal.
Wounds may be very small and go unnoticed, particularly in the event of bat exposures.
Human to human transmission has not been documented
In a rabies-endemic area, the circumstances of an animal bite and the animal’s behaviour and appearance may suggest that it is rabid. Domestic animals may be aggressive and attack unprovoked and conversely wild animals may act uncharacteristically tame and timid. All such exposures that involves ANY contact with the animal should be reported to a doctor with a sound knowledge of rabies without delay.
NO attempt to catch or kill the animal should be made for fear of further exposure. Report the animal to the local authorities who should have the animal observed and or euthanized by a qualified veterinarian. Remain in contact with the veterinarian until it can be conclusively confirmed whether the animal did / not have rabies.
At the time of Exposure: The bite, scratch or lick should be well washed with soap and water to remove as much saliva as possible from the area. Do NOT scrub the wound as this may force the rabies virus into the nerve endings. Apply an iodine containing antiseptic and or 60% alcohol if iodine is not available.
Do not stitch the wound!
Dress the wound and obtain post exposure prophylaxis which should be administered in accordance with established treatment protocols dependent on whether the animal was known to be rabid or not, the category of the exposure / wound and the patient’s pre-exposure vaccination status.
Post-exposure treatment to prevent the establishment of rabies infection involves first-aid treatment of the wound including thorough cleaning followed by administration of rabies vaccine and anti-rabies immunoglobulin in the case of severe exposure and in the absence of complete, reliable pre-exposure vaccination.
The administration of vaccine, and immunoglobulin if required, must be carried out, or directly supervised, by a physician.
Patients who have established rabies can not be salvaged – they are sedated and made comfortable until death follows…
Massive animal vaccination campaigns take place in large parts of the world in an attempt to eradicate rabies from the animal and in particular domestic dog population.
Mass vaccination of humans is impractical and too costly for governments to commit to, but individuals who have regular exposure to animals such as veterinarians and wild life managers should all receive pre-exposure vaccination.
Travellers to remote areas or regions with no or unreliable access to post-exposure vaccination and rabies immunoglobulin should seriously consider pre-exposure vaccination. That will obviate the need for more than two post-exospore rabies vaccines in the event of an encounter with a rabid or potentially rabid animal and most importantly do away with the need for post exposure Human Rabies Immunoglobulin – a scarce and expensive but life-saving drug.
Pre-exposure vaccination with rabies vaccine is used to confer antibody protection to individuals before they come in to contact with potentially rabid animals.
A primary course consists of two intramuscular or intradermal vaccines on Day 0 and 7, in line with the latest WHO guidelines.
Persons who are more likely to be exposed such as cyclists, joggers, game rangers and veterinarians or persons who will spend a prolonged period of time in remote locations should receive a single booster one year later.