How to prevent rabies?


Dogs are humans' closest animal companions. But one infectious disease related to dogs is very scary, and that is rabies.

Rabies is a disease transmitted by the rabies virus. Its clinical manifestations include foaming at the mouth, fear of water, inability to drink water, and even the inability to swallow one's own saliva, so it is also called hydrophobia. After a person is infected, once symptoms appear, the probability of death is almost 100%.

The manner in which rabies patients die is horrific. Worse yet, by the time an attack occurs, nothing can be done to help. All people can do is to put on an intravenous drip to prevent the patient from dying of dehydration immediately. In humans, rabies is one of the deadliest infectious diseases known, killing more than 60,000 people worldwide each year.

However, humans are not helpless. Recent scientific experiments have shown that we have ways to eradicate rabies. Several small-scale experiments show that with the right measures, this dream can become a reality in just a few years. If it does, rabies will become the third infectious disease to be eradicated from humans, after smallpox and rinderpest.

Rabies - the ancient enemy of mankind

Rabies is mankind's ancient enemy. Many animals, from bats and weasels to monkeys and raccoons, can carry rabies, but most wild animals can live with it without incident. Only dog rabies virus poses a major threat to both dogs and humans. In ancient Mesopotamia, if a mad dog bit someone, the owner would be fined a large sum of money, enough to buy 20 boats. It is certainly reasonable to impose such heavy penalties in law, because rabies is an incurable disease.

Humans have been trying to figure out how to deal with rabies since 1885. At that time, French microbiologist Louis Pasteur encountered a boy bitten by a mad dog. Pasteur treated rabies with a vaccine made from the dried bone marrow of a rabbit infected with rabies. After many attempts, he finally saved the boy's life.

Like Pasteur, modern times also use a combination of prevention and treatment, because rabies has an unusual feature: the virus does not attack immediately after entering the body; it takes several weeks for the virus to spread from the wound to the spinal cord or brain. incubation period. The spread process is relatively slow, which means that if people bitten by animals carrying rabies virus can receive timely treatment, such as multiple consecutive vaccinations within a month, the rabies virus will not attack them. Thanks to these treatments, there are now only one or two rabies deaths a year in the United States. Those who die are usually caused by being bitten by wild animals and failing to seek medical treatment in time.

Indiscriminate killing of dogs cannot eradicate rabies

Today, rabies deaths are concentrated in underdeveloped areas of Africa and Asia, where most dogs are not strictly controlled and are allowed to roam the streets. Dog owners have little awareness of being responsible for their dogs' behavior. As house animals, people may provide their dogs with food and sleep but don't have the money to vaccinate them against rabies. Similarly, if someone is bitten by a dog, the rabies vaccine is not readily available: treatment costs are a huge expense for poor people; or the local hospital may not have the vaccine in stock.

This is why in developing countries, rabies is often controlled by reducing dog populations. When rabies breaks out in an area, dogs are the first to suffer. People hunted dogs everywhere, killing them regardless of whether they were sick or not.

But this is not a long-term solution to controlling rabies. Killing can indeed reduce the number of dogs in a short period of time and control the spread of rabies virus, but dogs from other places will soon flood in to fill the gap, and the newcomers may carry rabies virus, laying the groundwork for the next outbreak. The bane.

A better approach would be to vaccinate the dogs instead of killing them. Vaccines for dogs are relatively cheap: A dose only costs about 25 cents, compared with more than $100 to vaccinate a person bitten by a dog. If enough dogs in an area are vaccinated for several consecutive years, the probability of people contracting rabies will be greatly reduced.

Vaccination works

This solution works because rabies spreads relatively slowly. For example, for infectious diseases like measles, each patient can infect about 15 other people, while a mad dog can only infect an average of 1.2 dogs (or people) before dying. From the perspective of disease transmission, this means that if 70% of the dogs in an area are vaccinated, the rabies virus will basically disappear on its own with the death of the sick dogs. Moreover, if there is not a resource vacuum left after a large number of dogs are killed, dogs carrying rabies virus from other places will not come in.

Why is the vaccination rate of dogs in an area so important for rabies control? For example, if a mad dog bites two dogs before dying, and these two dogs happen to be vaccinated, then rabies will be stopped in the first step; if both dogs are not vaccinated, then the number of rabies There were two more dogs at once. These two sick dogs were going to bite other dogs, and then they had to face the problem of whether the bitten dogs had received their seeds. Theoretically, as long as 70% of dogs are vaccinated, the probability of infection will gradually decrease and eventually approach zero; but if the vaccination rate is lower than 70%, the probability of infection will increase step by step, eventually spreading to the entire dog population .

However, this method of vaccinating dogs has not been taken seriously in the past. Because people are worried that so many other animals in nature carry rabies virus, even if the virus has just been completely eliminated from the dog population, it will be quickly replenished from the "virus reservoir" in nature.

But this idea is actually wrong. Although dogs may be infected with rabies virus after being bitten by bats, and then the dogs bite people and pass the virus to people, bat rabies virus is a variant of dog virus and cannot be transmitted between dogs. Therefore, in order to control rabies, we should still focus on controlling the spread of dog viruses, and the effective way is to vaccinate dogs.

A two-pronged approach is ineffective

Many South American countries have used this approach with great success. They set up free vaccination clinics in the community, allowing residents to bring their dogs to be vaccinated, and then put a signature collar on them after vaccination. This approach worked so well in Uruguay, Chile, and southern Brazil that dog rabies was almost eradicated there, and mass vaccination of dogs was no longer even necessary.

In contrast, other places have achieved little despite great efforts. For example, although the Indonesian island of Bali has been using a two-pronged approach of vaccinating dogs and killing dogs to eliminate rabies in the past decade, rabies outbreaks still occur from time to time. Bali is an island isolated from the mainland. It stands to reason that it should be easier to eliminate rabies here.

Experts believe that a two-pronged approach is precisely the crux. The indiscriminate killing of dogs actually hampers vaccination campaigns. Because when the bred dogs are killed, the proportion of such dogs in the population will drop to less than 70%, and to eradicate rabies, this proportion cannot be less than 70%. In addition, when they see their vaccinated dogs being killed like other dogs, the public will also become resistant to vaccination, thinking that vaccination is a waste of money, and they will be reluctant to get vaccinated in the future.

Eradicating rabies is possible

Currently, the country with the most difficult task of eradicating rabies is India. India accounts for a disproportionate share of global rabies deaths, accounting for 35% of the total. The main reason is that the streets of India are full of stray dogs due to the lack of timely removal of junk food. These dogs are not only numerous in number, but also very vicious. It is difficult for ordinary people to catch them and take them for vaccination.

But even here, vaccinations, through the efforts of international charities, have led to a multi-year decline in local rabies deaths. For example, in Goa, India's smallest state where the charity is running trials, rabies deaths have dropped from 14 in 2014 to four in 2015 to one in 2016. This proves that by vaccinating dogs, rabies can be eradicated in a place like India where rabies remains so high.

While these achievements are encouraging, eradicating rabies globally will require continued efforts by national governments and international agencies. In 2015, the World Health Organization and several other international agencies developed an action plan with the goal of eliminating the threat of rabies to humans by the end of 2030.