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An Overview of Rabies

By Edited May 11, 2015 0 0

Rabies - An Ever-Present Danger

Rabies is not present in Australia and New Zealand so increased cases of the disease in Bali, Australia's near neighbour and a popular holiday resort, were received with dismay. The increased interest in the ownership of pets in East Asia has seen a dramatic rise in cases of rabies in these countries.

In 1996, Australian Bat Lyssavirus (ABLV) was discovered. This is similar to rabies and seems prevalent among native bat populations. In some European countries, rabies is confined to bat populations.

Rabies is a viral disease. The virus is a lyssa virus and one of the few in the lyssa group which affects humans. It is zoonotic, meaning it is transmitted by animals, either to other animals or to humans. Unless the disease is treated prior to the onset of neurological symptoms, it is almost always fatal to humans. An estimated 55,000 humans die annually from rabies, some 31,000 in Asia and 24,000 in Africa. In these countries, stray dogs are the most common cause of infection. Monkeys and bats are also key offenders. In Europe, the most common carrier is the fox. Infected animals become aggressive and will attack and bite without provocation. Not everyone who is bitten by a rabid animal develops the disease. The ratio is about one in six falling ill.

Rabid Dog

The virus enters the body through a bite from infected animals, and travels to the brain via the peripheral nerves. It may take several months in humans for the virus to reach the central nervous system (CNS). The brain becomes inflamed and many CNS functions are affected. The virus spreads to many tissues of the body including mucous membranes and salivary glands. Unless treatment is started almost immediately, convulsions, respiratory failure and death follow, usually within a matter of days.

In the United States, rabies is common among wild animals with foxes, skunks, raccoons and bats accounting for 98% of all cased in 2009. Britain was thought to be free of rabies until bats in Scotland were found to be infected. However the disease has been eradicated from all animals that live on the ground.

Vaccination of domestic animals against rabies has reduced or eliminated the condition is most developed countries.

Rabies Notice

Some countries and/or states distribute baits in an effort to inoculate wild animals against rabies. Texas has laid out vaccine baits for coyotes and Canada has done the same for wild raccoons in the Mont-Royal Park region.

The term 'rabies' comes from the Latin rabies meaning madness. The disease has been known since around 2000 BC with the first written records appearing in the Codex of Eshnunna of Mesopotamia. There has been a great fear of rabies throughout the centuries with much irrational thinking and hocus-pocus surrounding its causes, prevention and treatment.

In 1885, Louis Pasteur began to test post-exposure treatments, eventually inventing the first vaccine against rabies. Until this time, all human rabies victims died of the disease.

Rabies is passed from one mammal to another. Three stages are recognised. The first stage is known as the prodromal stage and lasts from one to three days. This stage is characterised by behavioural changes. The excitative stage lasts from three to four days. This is sometimes known as furious rabies because of the affected animal's aggressiveness and hyperactivity. Finally the paralytic stage takes over, causing paralysis of the hind limbs, face and throat muscles. This causes incoordination, drooling and difficulty swallowing. Respiratory arrest is the usual cause of death.

In humans, the first symptoms are itching and discomfort at the site of the bite. There may be fever or headache. This is the acute incubation period of the disease, lasting generally from two days to weeks. Before the next group of signs and symptoms appear, there is a second incubation period. These range from anxiety and tension to delirium, drooling, hallucinations, combativeness, loss of muscle function, numbness, restlessness, insomnia and difficulty in swallowing. Violent movements, uncontrolled excitement, mania, acute pain may be experienced. Large quantities of tears and saliva are produced. The person has a great thirst but may become hydrophobic (fearful of water) as drinking causes throat spasms. The muscles of the throat and jaw slowly become paralysed. Speech and swallowing become impossible.

Once these symptoms appear, death is almost inevitable and usually occurs within seven days. Less than ten people have survived after reaching this stage of the disease. Treated early and appropriately the prognosis is extremely good. If treatment is begun within 48 hours of exposure, recovery is almost certain. The longer the delay in treatment, the greater the risk of a fatal outcome. Those with a compromised immune system (cancer patients, HIV sufferers) may need additional treatment.

Treatment
One method of treatment which has led to several recoveries from the disease is the Milwaukee protocol. In 2005, teenager Jeanna Giese survived rabies without receiving post-exposure prophylaxis. By the time Giese was admitted to hospital she had symptoms of blurred vision, slurred speech, fever and jerking of the left arm. After testing negative for a variety of diseases, her mother mentioned that Jeanna had been bitten by a bat about a month earlier. Rabies was diagnosed and confirmed by laboratory tests.

Dr Rodney Willoughby, Jr. at the Children's Hospital of Wisconsin in Wauwatosa decided to put Jeanna into an induced coma. The theory was that this would give her immune system a chance to defeat the virus. Suppressing brain activity would prevent the other potentially harmful symptoms from manifesting. Jeanna made a remarkable recovery with very few side effects and was able to finish her schooling and head off to college.

Vaccination involves a course of three injections at intervals of a week between the first two and the third injection three weeks later. The vaccination lasts for three years and is recommended for areas where there is a steady incidence of rabies.

Preventative treatment consists of administering specific antibodies (immunoglobins) which act by binding themselves to the virus, preventing penetration of the cells and giving the immune system time to fight the virus. The process is similar to be given an antivenin for snake bite.

As the immunoglobins break down in the body at a later date, this method does not give lasting protection from the disease.

If you receive a bite or even a slight scratch from a suspect animal, seek medical assistance immediately. Rabies is fully treatable if caught in time. The alternative is not pleasant.

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