We can break the chain of transmission!

As we saw in a previous video, rabies is a fatal disease.

Nevertheless, there is good news: it is preventable and there are effective vaccines for its control. In this activity, we will see the different systems to try to minimize the spread of rabies. Since most of the 30,000 to 50,000 cases of human rabies are caused by bites from rabid dogs, the most effective way to avoid human rabies is controlling urban rabies. Wide coverage campaigns, including over 70% of the dogs, have been the most effective systems to eliminate rabies in a region. To achieve this goal, education is greatly needed, involving the general population, local authorities, and implementing good diagnostic measures to track down infected animals and interrupt the chain of transmission.

Throughout the process, it is necessary to keep the vaccinated animals identified, through the corresponding health card, and eliminating stray dogs. In case a rabid animal has bitten a person, the person should be vaccinated immediately. Usually it will give time for antibodies to form before the virus penetrates the nervous system, and the progress of the infection will be blocked. In any case, the animal should be quarantined for observation. It is not possible to follow the same strategy to control wild rabies. The control of the spread of the infection has been attempted by decreasing the density of the populations of the reservoir species, but this system has not provided good results.

Currently, an oral vaccine is used to vaccinate wildlife, which is administered in baits, provided with an attractive smell for the target species. The bait is thrown from helicopters or vehicles. This system is safe, not detrimental to other species and effective, as we have seen in the step on epidemiology. Vaccines used are generally of recombinant virus, though attenuated vaccines have also been used. In contrast to urban and the wild rabies, rabies in bats cannot be prevented by vaccination, so the main control measures are management, like those shown here. For example, if a bat is found on the ground, unable to fly or with any other type of anomalous behaviour, it shouldn’t be handled.

It is advisable not to enter caves with dense populations of bats, where there will be many viral particles suspended in the air produced by aerosols. In places in the world where blood-sucking bats are a danger, it is recommended to keep cattle in stables overnight so that they are not exposed to them, closing windows and doors with screens, and administering anticoagulants.

There are three types of vaccines: live or attenuated virus, inactivated virus and those obtained by genetic recombination. Attenuated virus vaccines are obtained by growing the virus in chicken embryos or in cell cultures. Initially Pasteur obtained the vaccine against rabies by passing the virus in the brains of laboratory animals. All attenuated vaccines have the problem that the virus can revert to a virulent form and become dangerous, so they are not used in some countries. To obtain inactivated vaccines the virus is treated with heat or chemical or physical agents. Inactivated virus vaccines are safer, but less immunogenic, so animals need to be revaccinated every one or two years. They are the most used in pets.

Finally, recombinant vaccines are those in which the rabies virus gene encoding glycoprotein G of the envelope, are introduced in the genome of a poxvirus. As we mentioned in the first video of this week, glycoprotein G is recognized by the cell receptors. These vaccines induce a strong immune response. Besides pets, they are also used to vaccinate wild animals orally. We hope you remember that rabies is a preventable disease, but prevention measures are different depending on the epidemiological type of rabies.