Rabies and the Little Boy Who Didn’t Cry Raccoon

littlboyraccoonRecently there was a cute, little, 6-year-old boy bitten by a rabid raccoon. Soon after attack he was taken to the hospital where according to news reports, he was sutured and treated with antibiotics before being released. Later reports, confirmed that the raccoon was indeed rabid, however no additional reports addressed whether the little boy was vaccinated against rabies. Hopefully, he was treated after confirmation of the raccoons rabidity, but this type of reporting leads to confusion amongst the populace regarding what to do in case of a rabid animal bite.

rabidraccoonRabies which means “rage” or “madness” in Latin, was described as far back as the 4th and 5th century. It is caused by a ribonucleic acid (RNA) rhabdovirus (rod/bullet-shaped virus) that infects the central nervous system (CNS). A bite to the face carries an over 50% chance of developing rabies, however treatment soon after may prevent the fatal spread of the virus to the brain. Unless treated immediately, rabies is fatal.

Transmission of Rabies

Rabies is primarily transmitted through the bite of an infected animal, within whom the virus is shed in its saliva, to a human. However rare, It may also be spread through scratch and airborne transmission.

Signs and Symptoms

In humans, rabies  infects the nervous tissue, salivary glands, and respiratory tract, and causes mania, hydrophobia, aerophobia, and paralysis. Rabies has a variable incubation period, stemming from as little as a few days up to 2 or 3 years. Most cases present within 3 months. Once onset of the disease begins, there will be a localized pain or burning sensation, accompanied by tingling, and severe itching at the site of the wound; where the virus has replicated in the striated muscle tissue.

Early signs and symptoms may include headache, fever, nausea, and partial paralysis, which progress to confusion, hyperactivity, and hallucinations, as the virus spreads along the motor and sensory nerves. Additionally, the skin becomes hypersensitive to sensation.

Neurological symptoms develop as the virus travels to  the spinal cord causing uncoordinated gait, and worsening paralysis. Throat muscles spasm, causing difficulty in swallowing. Then there is the phenomena of  hydrophobia and aerophobia (fear of water and air). In the final stage, the virus invades the brain, causing encephalitis, coma, and death.

Rabies Vaccination and Treatment.

Bites and scratches should be immediately washed with soap and water. Antibiotics and a tetanus-diphtheria shot should be administered to prevent tetanus (a bacterial infection that causes muscle spasms and death). A Rabies vaccine regimen should be started as soon as possible.

Prophylactic Immunization. Post exposure Rabies vaccination is a prophylactic regimen consisting of multiple doses of vaccine given intramuscular, over the course of 3 months. It is designed to elicit an immune response that confers protection of the host against the virus by inducing antibody formation. Treatment should be started immediately, while it is being determined whether the animal was rabid or not.

Post exposure vaccination should be accompanied by Rabies Immune Globulin (RIG) or Anti-rabies Serum(ARS). This treatment should be given immediately at the site of the wound. RIG or ARS is not necessary for those who have received immunization prior to exposure.

1883. Louis Pasteur develops the first rabies vaccine. Prior to which, cauterization of the wound was the only treatment.

1911. The Semple vaccine was made up of inactivated virus from brain or spinal cord tissue. Given subcutaneously, the Semple vaccine had the draw back of eliciting possible allergic reactions that occasionally led to complications involving the brain, such as, encephalitis and paralysis. It also caused severe abdominal pain, fatigue, fever, and even rabies itself.

1957 – 1981. In the United States, during this period, a duck embryo vaccine was used.

1970’s. A human diploid cell vaccine (HDCV) was developed by growing the virus in fibroblast cell cultures. More efficacious than the duck embryo vaccine, it gives a faster antibody response, higher titer, and fewer side effects. This is the current vaccine in use.

Pre exposure Immunization. The human diploid cell vaccine is given in three doses over the course of a month, to those who are at risk of contracting rabies through occupational exposure (veterinarians, dog handlers, hunters, etc.) and to people living in regions where rabies is endemic.

Pre exposure immunization serves the function of drastically reducing the chances of developing rabies if infected, but does not eliminate the need for treatment. In such a case, a booster shot is given, alongside antibiotics and a tetanus shot.

Controlling the Spread of Rabies

The primary way that the spread of Rabies has been controlled in the United States is through the immunization of domestic dogs, as well as eliminating the presence of stray-dogs. The possibility of dogs biting other dogs, animals, and humans must also be prevented. This is the reason why dogs are kept on leases and not permitted to roam unaccompanied by an owner. Cats may also be immunized, especially if they are permitted outdoors.

However, the presence of rabies amongst wildlife such as raccoons, foxes, wolves and coyotes, bats, skunks, and feral cats cannot be as readily controlled. Population reduction helps by reducing the reservoir population for the virus and keeps wild animals from infringing on urban and suburban communities. Bait covered sponges containing an oral vaccine have been used to immunize raccoons in the wild.

Summary

rabiesvirusRabies is a zoonotic virus, transmitted via the bite or scratch of an infected animal to humans. At the wound the virus replicates and then travels along the nerves to the spinal cord, until it reaches the central nervous system. Therefore, a bite to the face has a shorter incubation period than bites to the limbs, as the proximity to the brain is shorter. If bitten, treatment should start immediately, and before the onset of symptoms, because once symptoms develop, the outcome is most certainly fatal. Most animals can be infected with rabies, but some are more susceptible to infection than others. In the case of a raccoon the likelihood of infection is high. So treatment for rabies should be started even before confirmation of the animals status. However, rodents and rabbits are very unlikely to have rabies. Consideration of what type of animal bite, and location of bite should play into determining the course of treatment. If possible the dead animal should be brought in for testing.

 

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