Disease: Rabies
This page provides general information about this condition; reveal the text by clicking on the green headers. Press releases, results from DWHC investigations as well as other useful documents and relevant literature can be found at the bottom of the page.
Pathogen
Rabies is the fatal disease in any animal (including humans) caused by infection with a member of the group of viruses known as lyssaviruses.
Classical rabies, the most commonly seen form worldwide, may be referred to as canine rabies as it predominantly infects dogs which are responsible for the majority of human infections worldwide; dogs are considered to be the reservoir species for this form of the virus as canid to canid transmission keeps the virus circulating.
Many variants of the virus have been recognized and whilst they are not species-specific, they tend to be named after the species that acts as the main reservoir and vector of that particular variant of the virus. For example, several variants of lyssavirus, including European bat lyssavirus, cause rabies in bats; and these can also infect humans. Cats are commonly infected with rabies in some parts of the world, however, no distinct feline variant of the virus has been identified; this means that whilst cats are vectors (an infected cat can infect another animal that it bites) of the canine or other form of the virus, they are not considered to be a reservoir host (i.e. cat to cat transmission is not reported).
Susceptible species
Rabies viruses primarily affect carnivores and bats although any warmblooded mammal can theoretically be infected. The susceptibility of the different orders of animals to rabies infection can be considered to be high in canids (e.g. dogs, foxes and wolves), and procyonids (e.g. raccoons); moderate in felids, mustelids (e.g. badgers, martens), ungulates (e.g. roe deer) and primates; and, low in lagomorphs, insectivores and rodents. In Europe the majority of reports of rabies in wildlife species were seen in the red fox.
Canids are the reservoirs of the classic rabies virus. In addition to domestic dogs (Canis familiaris), several European wildlife species can be infected and act as vectors of this disease including the red fox red fox (Vulpes vulpes) in countries such as Romania and Bulgaria; and the raccoon dog (Nyctereutes procyonoides) in some northerly countries including the Baltic states.
In contrast to classic rabies which does not circulate in wild animals in the Netherlands, European bat lyssavirus is regularly found in bats (particularly serotine bats, Eptesicus serotinus) in the Netherlands and some other European countries.
Cliquet F, Picard-Meyer E, Robardet E. Rabies in Europe: what are the risks? Expert Rev Anti Infect Ther. 2014 Aug;12(8):905-8
Johnson N, Freuling C, Vos A, Un H, Valtchovski R, Turcitu M, Dumistrescu F, Vuta V, Velic R, Sandrac V, Aylan O, Müller T, Fooks AR. Epidemiology of rabies in Southeast Europe. Dev Biol (Basel). 2008;131:189-98.
Signs in animals
There is usually a long delay (latency period) between the point of infection and the appearance of clinical signs; in dogs this is typically between 3 weeks and 3 months, but in some cases years can elapse before the onset of signs. The virus has a strong affinity for the nervous system and clinical signs reflect this. Rabid animals may show behavioural changes such as increased aggression, loss of the flight-response in wild animals and nocturnal animals may be active in the daytime. Altered vocalisation, pica (ingestion of foreign objects) and excessive salivation are also reported. An unsteady gait can develop and progressive paralysis typically sets in and ultimately results in death.
Infection of animals
The main means of infection is via the saliva of a infected animals, typically in bite wounds. The way in which the virus affects the nervous system often causes animals to behave aggressively, increasing the chance of an animal biting. Less commonly, the virus can be transmitted if open wounds or exposed mucous membranes come into contact with infected saliva or nervous tissue.
Very rarely, for example in laboratory environments or large bat roosts, virus transmission may occur through inhalation of aerosolized infectious saliva.
Symptoms in people
The majority of human rabies infections are the result of a bite from a rabid animal; worldwide, dogs are most often implicated in the transmission of this disease to people, however, national differences exist: For example, in the US rabid cats and raccoons are common sources of infection of people whilst in Europe, the widely distributed bat lyssaviruses are often implicated in human rabies cases when people have been bitten by infected bats.
Infection of people
The early signs of infection in humans may be vague and include fever and headaches. As the disease develops, signs related to the viral presence in nervous tissue may appear and can include altered mental states (confusion, depression, sleepiness, agitation), facial paralysis and ultimately progressive paralysis that leads to death.
Geographical distribution
Rabies is found on every continent except Antarctica and is endemic in many countries.
There are three genotypes of lyssavirus circulating in Europe: the dog/fox/raccoon dog strains (genotype 1) and two groups of bat lyssaviruses (European bat lyssavirus 1 [genotype 5] and European bat lyssavirus 2 [genotype 6]).
Through extensive vaccination campaigns and strict border control, several countries, such as the UK and Ireland, the Netherlands, Belgium and Luxembourg, have managed to eliminate the classical form of the virus. When no cases have been documented in recent years and suitable disease surveillance measures are in place, these countries are internationally recognized as having a disease-free status.
Smith GC, Thulke HH, Fooks AR, Artois M, Macdonald DW, Eisinger D, Selhorst T. What is the future of wildlife rabies control in Europe? Dev Biol (Basel). 2008;131:283-9.
Preventative measures
On a national level governments can implement vaccination programs in wild reservoir species and should ensure strict border movement/import controls. On an individual level, dog and ferret owners are encouraged to discuss vaccination with their vets.
Individuals who are at high risk of exposure to infected animals or carcasses (e.g. laboratory and slaughterhouse workers as well as those travelling in lands where rabies is endemic and there is a large feral dog population) should speak to their health advisers as vaccination against rabies may be recommended. Personal protective equipment should be worn to avoid cuts and bites and to protect the mucous membranes of the eyes and mouth.
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