Things you should know about rabies | What is rabies?

Dogs - potential rabis transmitter?
Dogs – potential rabis transmitter?

Rabies comes from the latin word, “rabere” meaning “to rage”. It is a preventable viral disease of mammals most often transmitted through the bite of a rabid animal. It is also referred to as “hydrophobia” in man, Lyssa le rage or Tollwut.

It is a zoonotic disease due to its transmission between man and animals.

The rabies virus infects the central nervous system, ultimately causing disease in the brain and death. It is believed to be the oldest infectious disease known to Medical science; recognized as early as 2300BC. The infectious nature of rabies is through the saliva of a rabid dog as recognised by Zinke in 1804 and then by Pasteur in 1881.

It is an acute encephalomyelitis that affects all warm-blooded wild and domestic animals and humans. It is caused by a neurotropic (negative sense single stranded) RNA virus, which belongs to the genus Lyssavirus of the family Rhabdoviridae, the Central Nervous System (Brain and spinal cord), salivary glands and saliva are the common sites the rabies viruses reside.

Rabies has been eliminated as a significant public health risk in most parts of the developed world. It is however estimated to cause at least 60,000 to 10,000 deaths per year worldwide, majority of which occur in Africa and Asia, particularly in rural areas in both continents (WHO, 2008).

Susceptible host
The virus affects primarily dogs, cats, bat, cattle, sheep, goat and all warm blooded animals are susceptible.

The virus is typically transmitted by being deposited under the skin, usually through a bite wound, contamination of a pre-existing wound is possible but unlikely because the local inflammatory reaction which follows a wound, which quickly seals the skin and prevents entry of the virus. Transmission across mucous membranes is also possible, but less likely. It has also been reported to be transmitted aerobically. Transmisssion by non-salivary routes has been recorded (Milius et al, 2004). These include aerosol transmission to humans in the laboratory and in bat-infested caves, transmammary and transplacental. Most often, humans contract the disease from infected stray domestic animals, commonly through a bite from such animal (dog especially).Also, animals contract it through wounds, when they are bitten by a rabid animal.

Rabies virus gains entry into a new host by introduction of virus-containing saliva into a bite wound. Entry may also be gained by saliva contamination of the mucous membranes of the mouth, eyes and nasal passages. The virus does not penetrate intact skin. At the site of entry, there may be local viral proliferation in non-neural tissue followed by viral attachment to nerve cell receptors and entry into peripheral nerve endings. The virus is transported along afferent axons, eventually reaching the central nervous system where proliferation is followed by widespread distribution of the virus throughout the brain and spinal cord. Following centrifugal transport along efferent cranial nerves, the salivary glands become infected and virus particles are shed in the saliva. Infection of the brain commonly leads to behavioral changes that induce the host to bite other animals, thereby transmitting the virus. The clinical picture can be highly variable between different species, individuals of the same species, and even within the course of the disease in a particular individual. The widespread central nervous system infection almost inevitably leads to death, usually through respiratory paralysis, but also through secondary circulatory, metabolic or infectious processes.

Types of Rabies
1. Urban rabies
2. Sylvatic rabies

Urban rabies

This particular type of rabies exist in metropolitans where unvaccinated and roaming dogs serve as the source of the infection.

Sylvatic rabies
This type exist in the wild whereby the scoons, raccoons, wild dogs, ferrets are the source. They serve as the reservoir of the virus and can transfer a fresh source of infection to urban areas from time to time.

Forms of rabies
Because rabies affects the central nervous system, it is nearly always associated with behavioral changes that may manifest in many different ways. Classically, rabies has been described as having a Prodromal Phase followed by either an Excitative Furious Form, or a Paralytic Dumb Form.
The Furious form of rabies is the most common. The roaming animals, dogs especially serve as the source of the virus. The rabid animals show signs of neuronal disorders like excitement, loss of fear of man, etc, hence can bite anything without necessarily been provoked.
The Dumb form of rabies usually have the animal owners as their victims, such rabid animal hides and shows signs like depression and excessive salivation to mention few, As the owner attempts to force it out of the hidden place, it bites upon provocation and transfer the infection if proper preventive measure is not taken.


Incubation period
This is the period of time from the exposure to rabies virus until the animal finally becomes sick and/or acts differently and is capable of infecting other animals or people. The incubation period can be as short as two weeks or in very rare cases as long as one year. The incubation period is usually 6 to 8 weeks in humans but it may be longer. During the incubation period, the animal cannot transmit rabies and its behavior remains normal and there may be time for the vaccine to prevent the animal from developing disease and prevent it from shedding or transmitting the virus.
Clincal signs

In Humans
Cerebral dysfunction

As the disease progresses, the person may experience
Abnormal behaviour

In Dogs
Change in temperament
Attacking and biting anything [often injuring mouth and breaking teeth, (excitative phase)]
Exaggerated responses to sound and light
Restlessness, and nervousness,
Snapping at imaginary flying insects, disorientation, wandering aimlessly, or a fixed stare,
Drooling saliva,
Depression (especially the dumb phase)
Hoarse howling and choking sounds,
Uncoordinated actions and progressive paralysis,
Dilated pupils, photophobia,
Irritability and infliction of self-injury,
Convulsions, and muscle spasms.

In Cats
Generally aggressiveness uncoordination, frothing, and muscular tremors.
Dilated pupils and staring
Threatening posture, abnormal vocalisation, lack of response to owners
Unprovoked attacks, biting (sometimes without releasing grip),
convulsions, paralysis, and coma,
Hiding away, some cats appear unusually affectionate and purr, or extend and retract their claws

In Cattle, sheep and goat
A typical hoarse bellow
Aggressiveness particularly on provocation, vicious attacks on inanimate objects, butting other cattle, attacking humans.Wind-sucking, and “bone in throat” syndrome
Separate themselves from rest of herd
Knuckling of fetlocks especially hind limbs, swaying gait, tail and posterior limb paralysis, jaw and tongue paralysis, profuse salivation, dragging hooves,
Pseudo-oestrous, hypersexual behaviour, decreased milk production, dilated pupils, fixed stare, grinding teeth, pica, tenesmus with diarrhoea, frequent urination, loss of condition, and emphysema

In pig
Hiding in corners of pen
Hypersexual behaviour
Aggression, biting,
And may kill offspring.

Prevention and treatment.
Thorough and immediate washing of bite wounds with plenty of soap and water is the best preventative treatment for rabies
NO effective treatment once clinical signs appear. Rabies post exposure prophylaxis (PEP) given before the onset of symptoms is nearly 100% effective and include the following:
a. Wound cleansing
b. Rabies immunoglobulin (RIG)
c. Vaccination

For unvaccinated persons after a dog bite:
• Give Five (5) doses of rabies vaccine intramuscularly in the deltoid area (shoulder) at day 0,3,7,14 and 21
• Give RIG

For vaccinated persons after a dog bite
• Give Five two doses of rabies vaccine intramuscularly in the deltoid area (shoulder) at day 0 and day 3
• Don’t give RIG

Pre-exposure prophylaxis recommended for Veterinarians, wildlife biologists, and animal control personnels
• Three doses of rabies vaccine is given at days 0,7, 21 or 28

In conclusion, the endemic nature of rabies is due to the rampant straying of owned domestic animals which are not catered for, and thus uninfected animals can contract the disease easily and spread it to man and animals . Also, there still exist a large number of dogs especially in our society which are unvaccinated and thus tend to spread the virus and making it uneasy to control and eliminate rabies completely from our society.

Abdulwahab Waliyullah
Faculty of Vertinary Medicine
University of Ilorin