One of the scariest diseases on record was rabies, until Louis Pasteur and Émile Roux developed the first effective vaccine. It is a viral disease, zoonotic in nature, which, if contracted, can be fatal.
The virus that changes behavior
The rabies virus is transmitted to humans by direct contact with the saliva or nervous tissues of an infected animal through mucous membranes or wounds. The most common way to get rabies is from the bite of a sick animal .
Once the virus enters the body, it travels through the blood to the central nervous system. The incubation period varies, but can last several months.
The first symptoms of rabies are reminiscent of the flu, however, very different effects soon appear, which are very characteristic: states of confusion and agitation, delirium, hallucinations and insomnia. The patient’s behavior changes ; experiences a strong hydrophobia , that is, the patient moves away from the water. It is an evolutionary adaptation that, by preventing the patient from drinking water, allows the virus to concentrate in the saliva without being diluted. Finally, the patient becomes aggressive and tries to bite any creature he finds; again, an evolutionary adaptation of the virus for its spread.
Between 2 and 10 days after the first symptoms appear, the patient usually dies. Barely 20 cases of unvaccinated human survival from rabies disease have been documented.
The rabies vaccine
Since Pasteur and Roux developed the rabies vaccine in 1885 , others have been developed, all of them effective, and safer the more modern they are. The most current ones are still under investigation. The studies are very promising, these new vaccines are based on mRNA, and thanks to research with SARS-CoV-2 vaccines, which use the same technology, they will probably have a significant advance in the coming years.
The advantage of the rabies vaccine, unlike most viral diseases, is its effectiveness even after exposure to the virus, as long as it is given before the first symptoms appear. Since the virus has a certain incubation period, during which it does not cause symptoms, the immune system can recognize the pathogen and neutralize it before it reaches the brain, preventing the disease.
When a person is potentially exposed to the virus, they are usually also inoculated with human rabies immunoglobulin . This provides immediate and functional antibodies to the patient, which can act against the virus while the immune system responds to the stimulus of the vaccine.
Of course, the best way to prevent rabies is to immunize pets. In some places the rabies vaccine is mandatory for domestic dogs, but even where it is not, it is always advisable to keep it up to date. Even in countries like Spain, where there is no endemic rabies.
Animals that transmit rabies
Although most of the cases of rabies in the world come from infected dogs, rabies is a virus that has natural reservoirs in many species of wild mammals.
Rabies only affects mammals , any mammal can get it, although not all can transmit it to humans. Therefore, birds, reptiles, amphibians or fish cannot transmit it.
In Spain, the largest reservoirs of rabies are the fox and the bat . Some invasive species , introduced as pets, such as the raccoon or the tanuki, have reintroduced rabies in countries where it was already controlled. Other possible transmitters, although less important, are the weasel, the stoat, the otter, the ferret and other mustelids, the bear, the wolf and other canids and even the wild cat. The domestic cat is also susceptible to contracting rabies and spreading it.
Among herbivores, rabies is less frequent, and when it does appear, they are unlikely to transmit it, but it does not make them immune or totally harmless. The risk exists in all farm mammals: cows, pigs, sheep and goats, even camels and horses, as well as their wild species can be infected; also cervids.
On the other hand, rats, mice and other rodents, contrary to popular belief, do not transmit rabies to humans even if they are infected. But, beware, that does not mean that they cannot transmit other diseases.
With domestic and farm animals, as with the dog, the best way to avoid rabies is vaccination . Especially if they are in the natural environment, and, therefore, are likely to come into contact with wild populations. Regarding animals in the wild, it is best to avoid contact, even with carcasses; the animal’s saliva can carry the virus even after death.
And if you are bitten by a wild animal, whatever it is, immediate medical attention is essential.
References:
Armbruster, N. et al. 2019. Advances in RNA Vaccines for Preventive Indications: A Case Study of a Vaccine against Rabies. Vaccines, 7(4), 132. DOI: 10.3390/vaccines7040132
Geison, G. L. 1978. Pasteur’s Work on Rabies: Reexamining the Ethical Issues. The
Hastings Center Report, 8(2), 26-33. DOI: 10.2307/3560403 Ministry of Agriculture, Fisheries and Food. yes Rage.
NCEID et al. 2019, julio 15. Rabies. CDC.
