Be Aware of Rabies Disease |PharmD India

Rabies is a viral disease. The virus travels from the site of entry (the bite or scratch) via the nerves to the brain and spinal cord and eventually spreads to the salivary glands. In humans, once symptoms have developed it is invariably fatal (there are reports of one or two people surviving once symptoms had developed). Symptoms may start with itching or tingling at the site of the bite or scratch. These may then develop to include headache and fever progressing to paralysis, agitation, spasm of the muscles used for swallowing, delirium and convulsions.
Symptoms

The incubation period for rabies is typically 1–3 months, but may vary from <1 week to >1 year. The initial symptoms of rabies are fever and often pain or an unusual or unexplained tingling, pricking or burning sensation (paraesthesia) at the wound site.

As the virus spreads through the central nervous system, progressive, fatal inflammation of the brain and spinal cord develops.

Two forms of the disease can follow. People with furious rabies exhibit signs of hyperactivity, excited behaviour, hydrophobia and sometimes aerophobia. After a few days, death occurs by cardio-respiratory arrest.

Paralytic rabies accounts for about 30% of the total number of human cases. This form of rabies runs a less dramatic and usually longer course than the furious form. The muscles gradually become paralyzed, starting at the site of the bite or scratch. A coma slowly develops, and eventually death occurs. The paralytic form of rabies is often misdiagnosed, contributing to the underreporting of the disease.
Diagnosis

No tests are available to diagnose rabies infection in humans before the onset of clinical disease, and unless the rabies-specific signs of hydrophobia or aerophobia are present, the clinical diagnosis may be difficult. Post mortem, the standard diagnostic technique is to detect rabies virus antigen in brain tissue by fluorescent antibody test.

Transmission

Rabies can be transmitted in a number of ways to humans. Dog bites are by far the most common source of infection—though mostly in undeveloped countries where vaccination programs are not in place. A scratch to the skin, a lick on a fresh skin break or contact of the infected saliva with intact mucous membranes may also transmit rabies. Cats, bats, foxes, skunks, raccoons, monkeys and many other animals can be infected with this virus. Animals may be infectious for five days before they develop symptoms. More unusual routes of infection have also been documented. Aerosol transmission has been reported in a bat infested cave in South America and corneal transplants taken from undiagnosed rabies sufferers have also transmitted this infection to others.

The incubation period for rabies in humans varies from 4 days to 7 years (usually between 20–90 days). The size and location of the bite or scratch, ie, proximity to the brain and the richness of the nerve supply to the area are thought to be important factors that influence the length of the incubation period. A deeply penetrating bite to the face or neck is likely to cause problems quicker than a scratch to the ankles.

Treatment and Prevention

Thoroughly cleanse all bites with soap and water and do not allow the wound to be stitched. Limited bleeding should be encouraged. Apply alcohol if possible. Once symptoms develop, death is inevitable in all cases. There is no cure. However, the disease can almost always be prevented, even after exposure, if rabies vaccine is administered without delay. Travelers should seek one of the modern cell culture vaccines. These can be difficult to obtain abroad. Some countries are using less effective locally produced vaccines that have to be administered into the abdomen; these are best avoided where possible. Travelers who have had a full course of pre-exposure vaccines still need to seek post exposure vaccines if they are bitten. However, they should only need two vaccines over 2 days and they will not need the human rabies immunoglobulin (HRIG) injection (HyperRAB S/D), which is in short supply in many countries. Those who have not had any pre-exposure vaccines or had an incomplete course of vaccine before travel should be given five post-exposure vaccines over 28 days plus the human rabies immunoglobulin (HRIG).

The antibody response to the first post exposure vaccine is expected to be rapid in those who have been “primed” with any rabies vaccines before they travel (even if they have not had a full 3 dose course). As the incubation period of the disease can in rare circumstances be as short as 4 days, the vaccines should always be sought as soon as possible. However, as the incubation period can be as long as several years in exceptional circumstances, it is still worthwhile getting vaccines if you were bitten in a risk area some time ago.

Never approach or handle animals you don't know, particularly if they are acting strangely. Pre-exposure immunization against rabies is recommended for long-stay travelers/residents and those who intend to travel to rural and remote areas in areas where rabies is common. In the event of a bite, your body's responses could be quickly activated by booster doses of vaccine. A full course of pre-exposure vaccines is three doses given on Days 0, 7 and 21–28. All travelers to risk areas should know what to do if they are bitten.

FIRST AID TREATMENT
Effective treatment soon (within a few days, but as soon as possible) after exposure to rabies can prevent the onset of symptoms and death.

Post-exposure prevention consists of local treatment of the wound, administration of rabies immunoglobulin (if indicated), and immediate vaccination.

Local treatment of the wound

Removing the rabies virus at the site of the infection by chemical or physical means is an effective means of protection. Therefore, prompt local treatment of all bite wounds and scratches that may be contaminated with rabies virus is important. Recommended first-aid procedures include immediate and thorough flushing and washing of the wound for a minimum of 15 minutes with soap and water, detergent, povidone iodine or other substances that kill the rabies virus.

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Akshaya Srikanth

Pharm.D*

Hyderabad, India
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