Imagine if the master organ of all actions of life is damaged by an entity that cannot be seen. Then, what would happen to the body is formidable. This microscopic culprit has zoonotic origins and is a subject of interest in public health. The deadly viral disease rabies’ has affected civilizations for centuries, posing a severe threat despite advancements in medical knowledge.
Rabies is a viral disease that affects the central nervous system, particularly the brain of living organisms, including animals and humans. It is caused by a virus scientifically known as Rabies lyssavirus. Rabid people have panic attacks whenever they are given water; that’s why it is also known as hydrophobia, the fear of water. The virus is an entity that can only survive inside a living organism, also called a ‘host.’
The saliva of infected animals contains the rabies virus. The animals infected with rabies are also referred to as rabid animals. Many pet animals, such as cats, dogs, cows, goats, horses, and wild animals, such as bats, foxes, monkeys, raccoons, and skunks, are the reservoirs of this lethal virus.
The virus cannot penetrate the unbroken skin but finds its way to the human body through a bite by a rabid animal. Suppose a rabid animal licks a healthy person’s face or any wound. In that case, the saliva of a rabid animal comes in direct contact with the eyes or mouth, leading to the entry of the virus into a healthy body.
Now, let’s discuss how the rabies virus spreads to the nervous system.
Neurons, the brain cells, serve as a bit of home for the rabies virus. When an animal is infected with the rabies virus and bites the host’s muscle, it transmits from the rabid animal to the muscle wound. Consequently, the virus attaches to and enters the nerve cells. There, it hijacks the host cellular machinery and makes numerous copies of itself. Those new viruses then attack nearby neurons, reaching the brain and causing it to swell. Afterwards, it also finds its way to salivary glands through local nerves. The saliva then becomes the transmission source for the spread of this deadly disease to other individuals.
Symptoms of Rabies Infection
The rabies infection advances in five stages: Incubation, Prodrome, Acute neurological period, Coma, and Death.
Incubation Period of Rabies Virus
The period from the entry of the virus into the host till the appearance of the first symptom is termed the incubation period. Symptoms appear when the virus reaches the brain. The onset of symptoms occurs after 30 to 50 days or may take a year to appear, depending upon the site of virus entry and its distance to the brain. The general observation about rabies is that “farther the site of bite from the brain, the longer the incubation period will be,” which means symptoms will take time to appear.
Prodrome
This stage is characterized by 38 ℃ or above fever, headache, illness or malaise, flu-like symptoms like cough and sore throat, numbness, and pain at the bite site.
Acute Neurological Period
This period starts with muscular spasms, troubled and rapid breathing, hallucinations, insomnia, anxiousness, permanent erection in males, increased production of saliva and froth formation in the mouth, seizures, and fits, severely painful stiffness of neck muscles whenever a rabid person tries to drink water, thus causing hydrophobia.
Coma and Death
As rabies progresses, airways in the brain get blocked, the brain swells, and complete paralysis occurs, leading to a coma and, ultimately, the death of a rabid person.
Diagnosis of Rabies Infection
In this video, we will learn how the rabies virus is diagnosed in humans and animals.
In humans
No test can reliably detect rabies in people’s antemortem (before death); instead, many assays are required. Hair follicle skin biopsies from the back of the neck and saliva, serum, and spinal fluid samples are tested. A virus may be isolated from saliva using the process of reverse transcription, which is then followed by polymerase chain reaction (RT-PCR). Antibodies against the rabies virus are measured in serum and spinal fluid. The presence of rabies antigen is evaluated in the cutaneous nerves around the hair follicles during a skin biopsy.
In animals
If the rabies virus is found in any part of the brain that has been affected, then it is possible to diagnose it. However, to exclude the possibility of rabies, the test must include tissue sampled from the brain, most preferably the brain stem and the cerebellum.
To complete the test, the animal suspected of having rabies will need to be put to sleep to collect brain samples from and transport these samples to a diagnostic laboratory for testing at a state public health or veterinary diagnostic facility.
Every year in the United States, roughly 120,000 or more animals are examined for rabies; of those, approximately 6% are determined to be infected.
Treatment of Rabies Infection
Once the symptoms appear, death will be the final consequence. Rabies is fatal but can be prevented by taking protective measures at the right time. Postexposure prophylaxis, often known as PEP, involves administering a dose of human rabies immune globulin (HRIG) and rabies vaccination on the same day an individual is exposed to rabies. After that, more vaccination doses are injected on days 3, 7, and 14. Postexposure prophylaxis (PEP) should always involve the injection of both the human rabies immune globulin (HRIG) and the rabies vaccination for patients who have never been vaccinated against rabies in the past. No matter how much time has passed after the initial exposure, starting treatment with a combination of HRIG and vaccination is always best. This holds for both bites and non-bite exposures. Only vaccines should be administered to those who have already been vaccinated against rabies or are currently through the pre-exposure vaccination process.
About the Author
Dr Madilyn Adams is a PhD in molecular medicine from Harvard University and has been working as a medical blogger for seven years.
References
- https://www.cdc.gov/rabies/about.html#:~:text=Rabies%20is%20a%20preventable%20viral,in%20the%20brain%20and%20death.
- https://www.mayoclinic.org/diseases-conditions/rabies/symptoms-causes/syc-20351821
- https://www.ncbi.nlm.nih.gov/books/NBK8618/
- https://www.medicalnewstoday.com/articles/321780#The-birth-of-vampirism?
- https://my.clevelandclinic.org/health/diseases/13848-rabies
