RABIES

 RABIES

Rabies is a viral disease that causes encephalitis in humans and other mammals.

Estimates suggest that over 5.5 billion people live with the daily risk of rabies, with 59,000 deaths every year.

Rabies is a vaccine-preventable, zoonotic, viral disease that affects the central nervous system, causing progressive and fatal inflammation of the brain and spinal cord once clinical symptoms appear.

Cause: The disease is caused by the rabies virus (Lyssavirus).

Transmission: It is primarily spread to people and animals through the saliva of infected mammals, usually via a bite or a scratch. 

Less commonly, transmission can occur if infectious saliva gets into an open wound or mucous membranes (like the eyes or mouth).

Primary Carriers:

• Globally, dogs are responsible for up to 99% of human rabies cases.

• In some countries, like the US, bats are the most common source of human infection, but other wildlife like raccoons, skunks, and foxes are also carriers.

How do you tell if an animal has rabies?

An animal with rabies may display a variety of behaviors that are uncharacteristic for the species. 

• Aggression: A normally passive animal may become aggressive and may attack for no reason.
• Lethargy: The animal may appear tired, confused, or uncoordinated, with a staggering or stumbling gait.
• Excessive salivation: Many people associate rabies with "foaming at the mouth" due to excessive drooling and difficulty swallowing.
• No fear of humans: A wild animal that appears unusually tame and unafraid of humans could have rabies. 

The incubation period 

How long does it take for rabies symptoms to appear?

The incubation period, or the time between exposure and the onset of symptoms, can vary greatly. While it typically ranges from a few weeks to several months, it can be as short as 4 days or, in rare cases, more than 3 year. This is why immediate treatment after exposure is critical, as there is no cure once symptoms develop. 

most commonly 3 to 8 weeks

The time depends on the distance the virus must travel along peripheral nerves to reach the central nervous system.

Early, non-specific symptoms may include:

• Fever, headache, and general malaise.

• Pain, tingling, pricking, or burning sensation (paraesthesia) at the wound site

There are several phases that most people go through: incubation, prodromal phase, acute neurologic phase and coma.

Incubation

Rabies virus can spend days to weeks in your body before it gets into your nervous system (incubation). You don’t have any symptoms during this time. If you receive treatment early in the incubation period, you won’t get rabies.

Prodromal phase

RABV travels through your nerve cells into your brain and spinal cord, causing nerve damage as it goes. The prodromal phase starts when the rabies virus has entered your nervous system. Your immune system tries to fight back, causing flu-like symptoms. Nerve damage might cause tingling, pain or numbness where you were bitten. This lasts two to 10 days. There aren’t any effective treatments when rabies reaches this phase.

Acute neurologic phase

In this phase, the rabies virus starts damaging your brain and spinal cord. About two-thirds of people have furious rabies, with symptoms like aggression, seizures and delirium. Others have paralytic rabies, with weakness and paralysis progressing from the bite wound to the rest of their body. Furious rabies can last a few days to a week. Paralytic rabies can last up to a month.

Coma

Many people enter a coma in the final stages of a rabies infection. Rabies eventually leads to death after 10 days.

As the virus reaches the central nervous system, the disease progresses into one of two forms:

1. Furious Rabies (about 80% of cases): Characterized by hyperactivity, excitable behavior, anxiety, confusion, hallucinations, hydrophobia (fear of water), and aerophobia (fear of drafts/fresh air). Death occurs after a few days due to cardio-respiratory arrest.

2. Paralytic Rabies (about 20% of cases): Runs a less dramatic course, characterized by muscle weakness and gradual paralysis, starting at the site of the bite or scratch. A coma slowly develops, leading to death.

Once clinical signs appear, rabies is virtually 99,9 % fatal.

Prevention and Treatment

POST EXPOSURE

Treatment after exposure can prevent the disease if given within 10 days.

The rabies vaccine is 100% effective if given before symptoms of rabies appear

The side effects of modern cell-based vaccines are similar to the side effects of flu shots.

1. Immediate First Aid: If bitten or scratched by an animal that could have rabies, immediately and thoroughly wash the wound with soap and running water for at least 15 minutes. Then, apply an antiseptic like povidone-iodine or alcohol.

2. Post-Exposure Prophylaxis (PEP): Seek medical attention immediately. PEP consists of:

• Thorough Wound Management.

• Rabies Immune Globulin (RIG): A fast-acting shot of antibodies given near the wound site (if possible) to provide immediate protection while the vaccine takes effect. This is usually given only if the person has not been previously vaccinated against rabies.

• Site and syringe separation: HRIG must never be mixed in the same syringe or injected into the same anatomical site as the vaccine, as this can neutralize the vaccine's effectivenes

• HRIG is not administered to previously vaccinated individuals, as it can interfere with their existing immune memory. 

• Rabies Vaccine: A series of injections (typically 4 doses over 14 days, or 2 doses if previously vaccinated) to help the body produce its own antibodies.

IM rabies vaccines should be administered in the deltoid for adults and the deltoid or anterolateral thigh for children

The CDC recommends administering the rabies vaccine on days 0, 3, 7, and 14 after exposure for patients with no prior rabies immunization.

Post-exposure prophylaxis of immunocompetent persons who have not been previously immunized with rabies vaccine consists of: local wound treatment; rabies immunoglobulin (20 IU/kg body weight) given on day 0 with as much as possible infiltrated into and around the wound; and four 1.0 mL IM doses of rabies vaccine given on days 0, 3, 7 and 14. In those who have not previously been immunized, and either are immunocompromised or are taking antimalarial drugs, a fifth dose of vaccine should be given on day 28.

 If you’ve already been vaccinated before exposure, you’ll only need two shots. 

• Post-exposure prophylaxis of persons previously appropriately immunized with rabies vaccine consists of: local wound treatment and two 1.0 mL IM doses of rabies vaccine given on days 0 and 3. Rabies immunoglobulin should not be given to persons who have previously received appropriate rabies vaccinations.

Around 95% of people who have 3 doses of the rabies vaccine will have some protection from rabies.

How long the protection lasts can vary, but it usually lasts at least 1 or 2 years.

People at continued risk of rabies may need 1 or more booster doses of the rabies vaccine to make sure they stay protected.

PRE EXPOSURE

Pre-Exposure Prophylaxis (PrEP): Vaccination is recommended for people in high-risk groups, such as veterinarians, animal handlers, and people traveling to areas where rabies is common and medical access may be limited.

• Pre-exposure immunization: three 1.0 mL intramuscular (IM) or 0.1 mL intradermal (ID) doses of rabies vaccine given on days 0, 7 and any time between days 21 to 28. Rabies vaccine must never be given into the gluteal muscle due to the risk of a decreased immune response.

PET VACCINATION

The most cost-effective strategy to prevent human rabies is mass vaccination of dogs.

Schedule: Kittens typically receive their first rabies shot around 3-4 months of age. 

A booster is given one year later, and subsequent boosters are typically given every 1 or 3 years, depending on the vaccine type and local laws.

EXPOSURE TO DOG/CAT

Exposures to dogs, cats and ferrets that could potentially result in rabies transmission (as described in Type of exposure) should be reported to local public health officials. Dogs, cats and ferrets that are apparently healthy should be confined and observed for 10 days after a bite, regardless of the animal's rabies vaccination status. If these animals - are alive and healthy at the end of the 10-day period, they would not have transmitted rabies in their saliva at the time of the bite.