Rabies is a rare but very serious viral infection affecting the nervous system. It is generally present in the saliva of the infected animals and transmitted to humans through their bite. Whilst currently eradicated from the United Kingdom and Western Europe, rabies still exists in over 150 countries around the world, particularly in Asia, Africa as well as Central and South America and is responsible for thousands of human deaths each year, half of which involving children under the age of 15.
Get to know a little more about one of the oldest diseases of mankind.
By Ricardo Ribas
Rabies is a serious and almost always fatal zoonosis that affect mammals. The term “rabies” was originated during Roman times, meaning rage/madness down to the disease’s frightening symptoms. As a matter of fact, humans have always been terrorised from catching this disease, and it was already the subjected of myths in the Mesopotamian civilization over 4,500 years ago.
THE WORLD OVERVIEW?
Rabies is a disease that is currently spread all over the world. However, some countries have achieved disease eradication, such as USA, Canada, Australia, New Zealand and many Scandinavian and Western European countries.
By the early twentieth century, rabies was eradicated from all Europe, however, in 1935, it was re-entered via Russia, and since the virus is transported through wildlife, its progression was difficult to control and the disease spread to Western countries. Nowadays and thanks to efficient preventive measures, rabies is currently eradicated from most Western and Scandinavian European countries. The United Kingdom has been free of rabies for 100 years with the exception of a rabies-like virus that is still existent in a small number of wild bats.
Whilst dog vaccination is not necessary in the UK, some European countries still require a compulsory annual vaccination for all dogs to avoid serious public health problems in the event of an outbreak. If you’re planning on taking your pet abroad to another European country, remember that your animal will need to be at least 12 weeks-old and already microchipped to have the rabies jab.
According to the world health organisation, there are currently 3 billion people in the world at risk of contracting this disease and an estimate of 59,000 deaths every year. This means that rabies kills one person every 9 minutes. Unfortunately, when the signs and symptoms start to manifest, the disease is almost always lethal.
WHO IS TO BLAME?
The rabies agent is a bullet-shaped virus belonging to the family of the Rhabdoviridae. Carnivores such as foxes, wolves, bats, monkeys, racoons and coyotes are wildlife hosts of the virus. Domestic animals are usually contaminated by other domestic or wild animals, whilst humans are mainly contaminated through the bites of domestic animals (dogs and cats). Dogs contribute to 99% of all rabies transmissions to humans.
The virus lives in the saliva of the diseased animals and is usually transmittable through a bite, however, in rare cases, contamination is also possible via sneezing, coughing or through superficial wounds.
WHAT ARE THE SYMPTONS?
Upon entering the host wound, the virus multiplies in their local muscle cells for several weeks or months before migrating to their central nervous system (brain and spinal cord), causing inflammation (encephalomyelitis) and leading to changes in the host behaviour. In animals, the incubation period (period from the entry in the body to the appearance of the first symptoms) is on average one to two months. In humans, the incubation period can range from four days to as long as 19 years, but in the majority of the cases it takes around 20 to 90 days for the first symptoms to appear.
IN THE PETS …
At the early stages of the disease, the animal exhibits increased nervousness and activity, difficulties breathing, fever and changes in vocalisation and sexual behaviour. Subsequently, two forms of the disease are possible: the furious and the silent forms. In the furious form, the animal becomes very alert and aggressive with dilated pupils, loss of appetite and changing in barking. Contrary, in the silent form, the animal becomes lethargic, paralysed, with muscle tremors and cries persistently. Cats present similar symptomatology with lack of mobility particularly in the chewing and swallowing muscles.
…AND IN THE HUMAN.
Humans affected by the disease show slightly different symptoms from the animals. Infected individuals, initially have flu-like symptoms, such as general weakness, headache and fever but with time those progress to neurological/behaviour symptoms. These include confusion, hallucinations, muscle spasms, bizarre beating and biting behaviours, fear of water (hydrophobia) and general deterioration of mental state, often culminating in death by cardiac or respiratory arrest.
PREVENTION AND CONTROL OF THE DISEASE
In order to keep control of rabies and to provide prompt actions to eradicate the disease in the event of the outbreak, several countries are implementing measures such as:
– Compulsory annual vaccination for all dogs aged four months old and older.
– Registration and compulsory licensing of dogs.
– Slaughter of all animals that are angry or have been bitten by animals infected with rabies.
– Veterinary examination and compulsory quarantine for all pets coming from countries with rabies.
– Wildlife vaccination by releasing oral vaccines into the ground to prevent the spread of the disease.
HUMAN PREVENTION AND TREATMENT
It is recommended that people travelling to rabies endemic areas are vaccinated and avoid contact with domestic and/or wild animals, particularly dogs and cats.
Unfortunately, no treatment is available. Infected animals are usually slaughtered and humans rarely survive from the disease. For humans exposed to rabies, post-exposure treatments such as a course of rabies vaccine or a specific immunoglobulin can be effective in preventing the disease from developing particularly if given before the start of the symptoms. Washing the bite sites and scratches with soaped water or detergent may also reduce the number of virus entering the skin and may be somewhat effective at preventing transmission.
As of 2016, only fourteen people had survived rabies infection after starting of the symptoms.
By Ricardo Ribas, Veterinary Doctor, doctorate in veterinary sciences and researcher in the area of oncology in London