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Rabies in dogs

Published: 
Sunday, August 20, 2017
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Rabies is an infectious viral disease that affects the brain and spinal cord of domestic and wild mammals, including human beings, dogs and cats.

The rabies virus is the type species of the Lyssavirus genus of the Rhabdoviridae family. The disease is almost always fatal following the onset of clinical symptoms. Rabies is present on all continents, except Antarctica, with over 95 per cent of human deaths occurring in the Asia and Africa regions. Dogs are the main source of human rabies deaths worldwide, contributing up to 99 per cent of all rabies virus transmissions to humans.

There are several reported routes of transmission of the rabies virus. It is most often transmitted through a bite from an infected animal, as the virus is shed at high levels in saliva. Less frequently, it can be spread when the saliva from an infected animal enters another animal’s body through mucous membranes or through an open wound. The risk for contracting rabies is highest if your dog is not vaccinated and is exposed to wild animals.

The rabies virus does not live very long outside the host and only remains viable in the carcass of an infected animal for less than 24 hours. In Trinidad and Tobago, bats are the animals most likely to transmit the virus. Joseph Pawan (1887-1957) was a Trinidadian bacteriologist who was the first person to show that rabies could be spread by vampire bats to other animals and to humans.

In 1925 there was an outbreak of rabies in cattle in Trinidad, which was first diagnosed as botulism. Humans began contracting rabies in 1929, first diagnosed as poliomyelitis. The outbreak continued until 1937, by which time 89 human fatalities were recorded.

If your pet has been bitten by a rabid animal, the virus will spread through the nerves towards the brain. The dog is unlikely to show immediate signs as the virus is relatively slow-moving, and the average time of incubation from exposure to brain involvement is between three to eight weeks. After the virus reaches the brain it will then move to the salivary glands, where it can be spread if your dog bites a human or animal. Once the virus reaches the brain, the animal will show symptoms which can be categorised into three different phases.

The first is the prodromal phase which lasts for two-three days in dogs and is generally characterised by a change in behaviour. Friendly animals may become shy, irritable or aggressive; while normally aggressive animals may become affectionate and docile. Other symptoms include apprehension, nervousness, anxiety, solitude and a fever.

The second is the furious phase, which usually lasts for one-seven days in dogs, where the animal becomes hyper-sensitive to auditory and visual stimuli. They may hide in dark places or eat unusual objects. They are more prone to irritability and restlessness, which causes them to roam and behave viciously. They may progress to becoming disoriented, weak, lose their appetite, suffer seizures, and die suddenly.

Animals may develop the paralytic (dumb) phase either after the prodromal or furious stage. It usually develops within two-four days after the first signs are noted. Nerves in the head and throat are the first to be affected and animals may begin to salivate and foam at the mouth as a result of their inability to swallow. The animal will get weaker and eventually go into respiratory failure and die.

There is no treatment or cure for rabies once symptoms appear. Since rabies presents a serious public health threat, dogs who are suspected of having the virus are most often euthanised. Vaccination is the only way to ensure that your dog is protected from this deadly disease.