What is rabies?
Rabies is a very serious disease, and one of the oldest known infectious conditions. It is an acute viral disease that affects both wild and domestic animals including humans who get infected from contact with rabid animals. Rabies affects the nervous system and primarily spreads to almost any mammal including birds. Once the disease enters the body, it travels by the nerves until it reaches the central nervous system (the spinal cord and the brain). From here, the virus spreads to the salivary glands where it prepares to spread to another victim. Pets that have not been vaccinated against rabies are at risk if exposed to or bitten by a wild animal.
Rabies is an invariably 100% fatal viral infection that is passed from animal to animal via saliva. When the saliva comes into contact with the uninfected animal’s blood and mucus membranes (mouth, eyes, and nasal cavities) the disease passes from the infected animal to the uninfected animal. Rabies is still a serious problem in most countries of the world with the infection commonly occurring in dogs and cats associated with humans. Locating any bite marks or open wounds can help determine if a dog might have been exposed to rabies.
What are the recognizable signs of rabies?
Rabies signs usually develop within two to eight weeks after an animal has been infected with the virus, either through a bite or saliva from an infected animal gets in an open wound of another animal. Occasionally, the development of signs may be delayed for months or years, depending to some extent on the site of the bite. Signs tend to develop more rapidly following bites around the face.
a) Early signs of rabies infection.
The early stage of rabies infection can last from two to ten days. However, it can be anywhere from 5 days to 12 months, with an average of just less than 3 months. The early non-specific symptoms include:-
Muscle pain
Restlessness
Irritability
Chills
Fever
Malaise, a general feeling of sickness and discomfort
Photophobia, fear of bright lights
Anorexia, or disinterest in food
Vomiting
Diarrhoea
Inability or unwillingness to swallow
Cough
Paralysis of the throat and jaw muscles may follow
b) Symptoms of the mild form of rabies (Dumb or paralytic form).
The milder form of rabies is referred to as dumb or paralytic form because the dog may foam around the mouth or become paralyzed. It is the most common and lasts from 3 to 7 days. The dog also seems confused, sick, or lethargic (tired). If a dog shows any of the dumb form symptoms, he should immediately be taken to the vet. The other dumb form symptoms, including:-
Paralysis (inability to move) of the legs, facial muscles, or other parts of the body. This normally starts in the hind legs and moves forward through the body.
Dropping of the lower jaw, leading to a 'dumb' look.
Making a strange barking sound that does not sound like a normal bark.
Excess salivation creates foam around the mouth.
Difficulty swallowing.
Note that in this form of rabies, dogs are not vicious and rarely try to bite.
c) Symptoms of the aggressive form of rabies.
The furious or aggressive form lasts from 3 to 7 days and the dog appears aggressive or easily excitable., and may behave abnormally and foam around the mouth. Although this form is what people generally think of when they think of rabies, it is less common in dogs than in the dumb or paralytic form. Furious form creates excessive aggression that must be handled with extreme caution to prevent being bitten. Call Kenya Society for the Protection and Care of Animals (KSPCA) to assist once a dog has this form of rabies. Signs include:-
Profuse salivation that will look like foam around the dog’s mouth.
Hydrophobia, fear of water. The dog will not go near water and will seem uneasy or panicked at the sound or touch of water.
Aggressiveness. The dog may look like he's trying to bite and will viciously show all his teeth.
Restlessness or discomfort. He may also be disinterested in food.
Irritability. The slightest provocation may cause the dog to attack and bite. The dog might even do this without any provocation or cause.
Abnormal behaviour like chewing on rocks, rubbish or his own legs. The dog may also follow your hand around if you wave it in front of him while he is in a cage. He may try to bite it.
Overly playful puppies that suddenly bite when petted, and become vicious after a few hours.
How long does it take for rabies symptoms to show?
The incubation period for rabies, which is the time from getting infected to showing symptoms, can be anywhere from 5 days to 12 months, with an average of just less than 3 months. The absence of a fresh bite wound does not necessarily rule out rabies if your dog is showing the common symptoms.
Can humans get infected with rabies?
Rabies virus is a zoonotic Lyssavirus that accounts for substantial mortality rates internationally in both humans and animals. A zoonosis (plural zoonoses, or zoonotic diseases) is an infectious disease caused by a pathogen (an infectious agent, such as a bacterium, virus, parasite or prion) that jumps from a non-human animal (usually but by no means always a vertebrate) to a human.
Rabies kills an estimated 50,000 humans per year, concentrated mainly in developing countries with endemic canine rabies and often inadequate public education and health systems.
The approach to managing rabies cases varies by region and should be decided on a case-by-case basis. Direct contact of rabies virus with mucous membranes (eg, saliva or neurologic tissue contact with the nose, mouth, or eyes) also poses a transmission risk.
Rabies virus is inoculated into the body via bites from animals in the late stages of rabies infection for the disease to occur. Typically, this is when the animals are shedding large amounts of the rabies virus in their saliva. Scratches are a potential exposure risk if rabies virus has been previously deposited on the skin via saliva and the scratch inoculates the wound, or if saliva is on the paw and the animal then scratches a human or another animal.
The approach to managing rabies cases varies by region and should be decided on a case-by-case basis. Direct contact of rabies virus with mucous membranes (eg, saliva or neurologic tissue contact with the nose, mouth, or eyes) also poses a transmission risk.
What are the rabies symptoms in humans?
How can humans protect themselves and their pets?
Rarely are there survivors of rabies in humans and animals suspected of having rabies are usually euthanised. This is essentially why the prevention of the infection is important.
There is no natural immunity against rabies virus infection and vaccination is the only most effective prevention measure. Vaccination is an important means of prevention both before possible exposure and after exposure. However, vaccination against rabies does not completely eliminate the risk of contracting rabies in certain circumstances.
What about travelling abroad with your pet?
Travelling abroad with your pet to a country with a high prevalence of rabies requires that vaccination be done. Single rabies vaccination is given and then the pet must have a blood test (a rabies titre test) done to confirm that they are protected.
As a pet owner travelling with your companion animal, you should also consider your own health by getting yourself vaccinated against rabies. If you get bitten by an animal abroad always seek local medical advice.
How is rabies treated?
Post-bite vaccination is the only recognised treatment to prevent the development of the clinical signs and death following infection with the rabies virus and the vaccine should be injected as soon as possible following the bite.
In countries where rabies occurs, any domestic animal that has bitten a person is detained and observed for at least 10 days. If the animal has rabies it is likely to show signs within 4 to 7 days. Care should be taken to avoid contact with secretions (saliva, urine) of infected or potentially infected, individuals.
References
[1] S. E. Aiello, M. A. Moses and D. G. Allen, Merck Veterinary Manual, 11th ed., NJ, USA: Kenilworth, 2016.
[2] J. Baby, R. S. Mani, S. S. Abraham, A. T. Thankappan, P. M. Pillai, A. M. Anand, S. N. Madhusudana, J. Ramachandran and S. Sreekumar, "Natural Rabies Infection in a Domestic Fowl (Gallus domesticus): A Report from India," 22 July 2015.
[3] S. Dürr, R. Mindekem, C. Diguimbye, M. Niezgoda, I. Kuzmin, C. E. Rupprecht and J. Zinsstag, "Rabies diagnosis for developing countries.," PLoS Neglected Tropical Diseases, vol. 2, no. 3, 26 March 2008.
[4] G. Gadre, P. Satishchandra, A. Mahadevan, M. S. Suja, S. N. Madhusudana, C. Sundaram and S. K. Shankar, "Rabies viral encephalitis: clinical determinants in diagnosis with special reference to paralytic form.," Journal of Neurology, Neurosurgery & Psychiatry, vol. 81, no. 7, pp. 812-820, 2010.
[5] National Association of State Public Health Veterinarians. (2016). , Compendium of Animal Rabies Prevention and Control Committee, Brown, C. M., Slavinski, S., Ettestad, P., Sidwa, T. J., & Sorhage, F. E. Journal of the American Veterinary Medical Association, 248(5), 505-517.