Rabies, a fatal viral encephalitis

Rabies is a viral encephalitis that is invariably fatal in humans and susceptible animals. The World Health Organization (WHO) estimates that 55,000 people die from rabies worldwide each year. Caused by infection with Lyssavirus, the disease has been documented since ancient times and remains a concern in many countries.

The classic rabies virus is responsible for nearly all human cases reported worldwide. Dog bites, licks, and scratches account for more than 99% of human infections. Children, due to their size and lack of wariness toward animals, are more at risk of these bites and virus transmission.

The lyssaviruses present in Europe include the classical rabies virus circulating among carnivores in Eastern Europe and EBLV1 and 2 (European Bat Lyssavirus 1 and 2) circulating among insectivorous bats throughout Europe.
EBLV 1 and 2 cause a disease in humans that is clinically identical to that caused by the classical rabies virus. However, human cases caused by EBLV are very rare, and only 5 cases have been reported worldwide since the discovery of these viruses.In 2011 in Germany and then in 2012 in France, a new lyssavirus, Bokeloh, was isolated from bats of the species Myotis nettereri. Its pathogenicity in humans is unknown. In Spain, the Lleida virus was first identified in 2013 in another bat species (Minopterus schreibersii). The virus was subsequently detected in France in the same species in 2017. Again, its pathogenicity in humans is unknown.

Ways of Contracting Rabies

Rabies is a vector-borne disease transmitted to humans through bites, scratches, or licks from an infected animal that excretes the virus in its saliva. Dogs are the primary reservoir, accounting for an estimated 95% of cases worldwide.
Cases of rabies following organ or cornea transplants have been reported in the past, including one in France in 1979. The organ donor screening measures in place in France help prevent such situations by excluding patients with serious infectious diseases from organ donation. Aside from these specific cases, human-to-human transmission of rabies remains theoretical and has never been demonstrated.

A risk that varies by region

Most Western European countries, including mainland France, are free of terrestrial rabies (i.e., rabies in non-flying animals as opposed to rabies in bats) as defined by the International Office of Epizootics. The risk to humans in these rabies-free countries stems, on the one hand, from potentially infected animals from other countries that are illegally imported, and on the other hand, from bats.

In contrast, in Eastern Europe and the Balkans, the risk of rabies among carnivores is not under control, and cases are regularly diagnosed in foxes and, more rarely, in domestic animals (primarily dogs).

In France, French Guiana presents a unique situation: it shares direct borders with countries where rabies is not controlled (Brazil, Suriname). The risk of rabies in French Guiana stems from carnivores that may have arrived infected from a neighboring country. Furthermore, in French Guiana, as in the rest of the Americas, rabies viruses circulate among hematophagous bats (“vampire bats”). These animals are responsible for significant economic losses in livestock and for the transmission of rabies to terrestrial animals and potentially to humans. In contrast, the other French overseas territories have never recorded any cases of animal or human rabies.

In Africa and Asia, animal rabies is not controlled, and these continents experience numerous animal and human cases. Estimates indicate that the highest annual numbers of rabies-related deaths occur in India (with an estimated 20,000 annual deaths), China, the Congo Basin, and West Africa.

A Fatal Disease

In humans, rabies has an average incubation period of 20 to 60 days. Shorter incubation periods, of less than a month, have been observed in rare cases of infection resulting from multiple bites, particularly to the head. Much longer incubation periods have also been observed very rarely.

After inoculation via a bite, scratch, or licking of mucous membranes by an infected animal, the virus multiplies at the site of entry and then reaches the brain by traveling along the nerves. Once the brain is reached, the virus causes encephalitis and then spreads to various organs.

Clinically, rabies presents as encephalitis (brain inflammation): fever, erratic behavioral disturbances, sometimes motor deficits, convulsions, and coma. Two highly suggestive signs are described: aerophobia (intolerance to the sensation of a draft) and hydrophobia (aversion to water, which is actually a laryngeal spasm that prevents swallowing). These signs are highly variable.

The disease inevitably progresses to death, characterized by coma associated with multi-organ failure.

There is no effective treatment for rabies once symptoms appear. The disease is then invariably fatal. It can, however, be prevented after exposure through the administration of vaccines and, if necessary, immunoglobulins (see below).

Rabies Prevention

The fight against rabies relies on a set of measures and tools available in both animal and human health. In this regard, the fight against rabies in France and Europe serves as a multidisciplinary and effective example of the “One Health” concept.

Traveler Information and Bite Prevention

The best way to prevent rabies is to avoid bites, scratches, and licking on mucous membranes or broken skin. Travelers should be advised not to touch animals while traveling, particularly dogs, to avoid not only infection with the rabies virus but also wounds caused by bites or scratches, and infections from bacteria present in the mouth and under the claws of animals.

• Learn more: Health recommendations for travelers.

With regard to rabies specifically, the virus is shed by infected animals before the onset of rabies symptoms such as aggression. A dog’s friendly behavior therefore does not rule out the risk of virus transmission, and the recommendation should be to avoid contact with animals—especially strays—in countries where rabies is not under control.

Vaccination of Pets

In France, vaccination of pets has always been carried out on a voluntary basis, and only animals traveling or staying in public places [e.g., campgrounds] are required to be vaccinated

Preventive vaccination

Preventive rabies vaccination is recommended for travelers visiting high-risk areas without easy access to medical facilities (rural or mountainous areas, remote locations, independent travel, etc.), as well as for biologists handling Lyssavirus and people in frequent contact with bats.

Post-exposure treatment

A very interesting aspect of rabies control is the ability to effectively treat people after exposure to the virus, and before symptoms appear, using vaccines and immunoglobulins. These post-exposure treatments (PET) aim to take advantage of the long incubation period to trigger a massive and rapid production of antibodies following the administration of multiple vaccine doses.
According to WHO recommendations, PEP is indicated for individuals exposed to animals that are known or suspected to be shedding the rabies virus. The recommendation for vaccination, with or without the addition of immunoglobulins, depends on the severity of the exposure (contact, superficial wound, deep bite wound) and the patient’s immune status.

In France, only rabies centers are authorized to prescribe post-exposure treatment.