Rabies is a lethal viral disease that is highly preventable. It is almost always transmitted to people through the bite or scratch of an animal with rabies, usually dogs in 99% of cases, but also wild animals such as foxes, skunks, bats, and raccoons.
It is possible to eradicate this disease in a region by vaccinating all dogs and preventing dog bites by proper awareness and sanitary measures like stray dog control. Nonetheless, more than half a hundred thousand deaths occur every year, most of them in Asia and Africa, with 40% of these being children less than 15 years.
Image Credit: Jarun Ontakrai/Shutterstock.com
Rabies occurs in every part of the world except Antarctica, but the risk is highly concentrated in Asia and Africa, where 95 of every 100 deaths due to rabies occur. As such, rabies is on the list of Neglected Tropical Diseases (NTD), that occur in poor and vulnerable populations living in remote rural locations.
About 80% of human rabies patients come from rural areas. In such cases, rabies immunoglobulin and vaccines, which are extremely effective in preventing the disease, are not always either available or in an accessible spot. The cost of such treatment in the form of post-exposure prophylaxis (PEP) could be as much as a hundred days' wages, implying that many families in such locations cannot get it.
Several separate programs will be required to help eradicate this problem. One is to do with community education on how potentially rabid dogs act, and how humans need to act around them to prevent bites.
Encouraging people to vaccinate their pets and train them properly will also help immensely. Knowledge of the need to wash any dog bite with plenty of soap and water, and seek advice on PEP at once, is also essential. Finally, dog control measures are mandatory to prevent stray dogs that are potential vectors of rabies.
The vast majority of rabies deaths in the world, and therefore rabies cases, since they are almost always fatal, come from Africa and Asia, especially India, where all cases are not even reported. Some countries in Latin America and Cuba also have high rates.
These regions typically have high stray dog populations, such as 10 million in Thailand, with a tenth of dogs in the Thai capital being rabid. People in Western Europe, Japan, Singapore, New Zealand, Taiwan, Sweden, and Norway, certain islands in the Caribbean, and Hawaii, among others, have no risk of rabies except imported animals, which itself is negligible in view of strict importation requirements.
Moreover, these areas have low access to rabies vaccination and even less to rabies immunoglobulin, which is essential to prevent the entry of the virus into the peripheral nerve while the immune response is still underway.
In countries with a high street dog menace level, tourists experience plenty of dog bites. Again, in Thailand, data show a prevalence of 1.3% dog bites in visitors to the country, with the exposure leading to infection in 15% of cases on average.
Travelers in rural areas are also at very high risk because of the large number of stray dogs in such settings. People who are in such areas in the latter half of the day, that is, during the evening or night, and spend time outdoors walking, jogging, on bikes, or in camps, are more likely to be bitten.
Children are four times more likely to be infected with rabies than adults because they are generally more prone to be bitten, and less likely to report such bites. In low-income countries, such children are prone to play with stray dogs or to be chased and bitten by them while walking on the road, for instance.
Other high-risk individuals include those who work on infected laboratory specimens, veterinary doctors, those who work with animal control teams, rabies researchers, and spelunkers. All are advised to take pre-exposure prophylaxis (PrEP), comprising three doses of the rabies vaccine. Pet owners should be aware of their own high risk of getting rabies from their pets if they do not vaccinate their pets.
The importance of pre-exposure prophylaxis
While PEP is still necessary in case of a bite or other exposure, PrEP renders immunoglobulin administration unnecessary in most cases and reduces PEP to a single intradermal vaccination. Since rabies immunoglobulin is largely unavailable in most low-resource countries, the importance of this protocol becomes obvious.
PrEP protocols are now simpler and more affordable, and scientists are considering the vaccination of high-risk groups of local people and travelers, as well as animals, in countries with endemic rabies, in a bid to eradicate the disease in developing countries as well.
The actual risk depends on other factors, such as the number and depth of the bites, the stage of rabies in the animal, and bites on the head or neck, or upper body, of the patient. This is because a high viral load in the bite wound can lead to rapid entry of the virus into the peripheral nerve, and then into the central nervous system; and also because the distance from upper body nerves to the brain is much shorter than from the lower part of the body.
Indications for immediate PEP
PEP is recommended in the following situations:
- Bites or exposure to animal saliva or to bats, and bites or scratches with broken skin, are category III exposures, and wound care, PEP plus infiltration of the area with rabies immunoglobulin are necessary.
- With scratches on the skin without bleeding, category II exposure has happened. While immunoglobulins can be avoided, but the other two are mandatory.
- For intact skin with licks, touching or feeding animals, category I exposure is present for which thorough washing is sufficient.
High-risk indications include:
- Bite by a species known to carry rabies
- High-risk geographical species
- Sick or abnormal behavior on the part of the animal
- Category III exposure
- Spontaneous aggression
- Bites by unvaccinated animals
While rabies still takes approximately 60,000 lives a year, with almost 100% fatality, the degree of risk is very uneven. It is necessary to assess the risk and understand who should take the PrEP and PEP, and when.
PEP saves almost all rabies bite victims if used early and as recommended. Moreover, it is nearly 100% effective. Once the clinical symptoms and signs of rabies manifest, treatment options are limited to keeping the patient comfortable and sedated until death supervenes.