Question

Is rabies caused by viruses or by bacteria? How is it transmitted? Which organs and tissues are affected by the disease? How is it prevented and treated?

Answer 1

Rabies is a viral disease that causes inflammation of the brain in humans and other mammals.

TRANSMISSION:

Rabies is caused by lyssaviruses, including the rabies virus and Australian bat lyssavirus.Rabies is spread when an infected animal scratches or bites another animal or human. Saliva from an infected animal can also transmit rabies if the saliva comes into contact with the eyes, mouth, or nose.Globally, dogs are the most common animal involved. More than 99% of rabies cases in countries where dogs commonly have the disease are caused by dog bites.In the Americas, bat bites are the most common source of rabies infections in humans, and less than 5% of cases are from dogs.Rodents are very rarely infected with rabies.

ORGANS AFFECTED BY RABIES ARE:

Rabies causes inflammation of the brain and spinal cord. Once the virus reaches the spinal cord and brain, rabies is almost always fatal.

PREVENTION AND TREATMENT:

Animal control and vaccination programs have decreased the risk of rabies from dogs in a number of regions of the world.Immunizing people before they are exposed is recommended for those who are at high risk. The high-risk group includes people who work with bats or who spend prolonged periods in areas of the world where rabies is common. In people who have been exposed to rabies, the rabies vaccine and sometimes rabies immunoglobulin are effective in preventing the disease if the person receives the treatment before the start of rabies symptoms.Washing bites and scratches for 15 minutes with soap and water, povidone iodine, or detergent may reduce the number of viral particles and may be somewhat effective at preventing transmission. Only six people have survived a rabies infection after showing symptoms, and this was with extensive treatment known as the Milwaukee protocol.

Their original vaccine was harvested from infected rabbits, from which the virus in the nerve tissue was weakened by allowing it to dry for five to ten days.Similar nerve tissue-derived vaccines are still used in some countries, as they are much cheaper than modern cell culture vaccines.

The human diploid cell rabies vaccine was started in 1967. Less expensive purified chicken embryo cell vaccine and purified vero cell rabies vaccine are now available. A recombinant vaccine called V-RG has been used in Belgium, France, Germany, and the United States to prevent outbreaks of rabies in undomesticated animals.Immunization before exposure has been used in both human and nonhuman populations, where, as in many jurisdictions, domesticated animals are required to be vaccinated.

Preventions are:

• Vaccinating dogs, cats, and ferrets against rabies
• Keeping pets under supervision
• Not handling wild animals or strays
• Contacting an animal control officer upon observing a wild animal or a stray, especially if the animal is acting strangely
• If bitten by an animal, washing the wound with soap and water for 10 to 15 minutes and contacting a healthcare provider to determine if post-exposure prophylaxis is required.

Treatment:

Treatment after exposure can prevent the disease if administered promptly, generally within 10 days of infection. Thoroughly washing the wound as soon as possible with soap and water for approximately five minutes is effective in reducing the number of viral particles.Povidone-iodine or alcohol is then recommended to reduce the virus further.

In the US, the Centers for Disease Control and Prevention recommends people receive one dose of human rabies immunoglobulin (HRIG) and four doses of rabies vaccine over a 14-day period.The immunoglobulin dose should not exceed 20 units per kilogram body weight. HRIG is expensive and constitutes most of the cost of post exposure treatment, ranging as high as several thousand dollars.As much as possible of this dose should be injected around the bites, with the remainder being given by deep intramuscular injection at a site distant from the vaccination site.

The first dose of rabies vaccine is given as soon as possible after exposure, with additional doses on days 3, 7 and 14 after the first. Patients who have previously received pre-exposure vaccination do not receive the immunoglobulin, only the postexposure vaccinations on days 0 and 3.

The pain and side effects of modern cell-based vaccines are similar to flu shots. The old nerve-tissue-based vaccinations that require multiple painful injections into the abdomen with a large needle are inexpensive, but are being phased out and replaced by affordable World Health Organization intradermal-vaccination regimens.

Intramuscular vaccination should be given into the deltoid, not the gluteal area, which has been associated with vaccination failure due to injection into fat rather than muscle. In infants, the lateral thigh is recommended.

Awakening to find a bat in the room, or finding a bat in the room of a previously unattended child or mentally disabled or intoxicated person, is an indication for post-exposure prophylaxis (PEP). The recommendation for the precautionary use of PEP in bat encounters where no contact is recognized has been questioned in the medical literature, based on a cost–benefit analysis.However, a 2002 study has supported the protocol of precautionary administering of PEP where a child or mentally compromised individual has been alone with a bat, especially in sleep areas, where a bite or exposure may occur without the victim being aware.Begun with little or no delay, PEP is 100% effective against rabies.In the case in which there has been a significant delay in administering PEP, the treatment should be administered regardless, as it may still be effective. Every year, more than 15 million people get vaccination after potential exposure. While this works well, the cost is significant.

Induced coma

In 2004, American teenager Jeanna Giese survived an infection of rabies unvaccinated. She was placed into an induced coma upon onset of symptoms and given ketamine, midazolam, ribavirin, and amantadine. Her doctors administered treatment based on the hypothesis that detrimental effects of rabies were caused by temporary dysfunctions in the brain and could be avoided by inducing a temporary partial halt in brain function that would protect the brain from damage while giving the immune system time to defeat the virus. After 31 days of isolation and 76 days of hospitalization, Giese was released from the hospital. She survived with all higher level brain functions intact, but an inability to walk and balance.On a 2013 podcast of NPR's Radiolab, 9 years after her discharge from the hospital, Giese recounted: "I had to learn how to stand and then to walk, turn around, move my toes. I was really, after rabies, a newborn baby who couldn't do anything. I had to relearn that all ... mentally I knew how to do stuff but my body wouldn't cooperate with what I wanted it to do. It definitely took a toll on me psychologically. You know, I'm still recovering. I'm not completely back. Stuff like balance, and I can't run normally.

Giese's treatment regimen became known as the Milwaukee protocol, which has since undergone revision with the second version omitting the use of ribavirin. Two of 25 patients survived when treated under the first protocol. A further 10 patients have been treated under the revised protocol, with a further two survivors.