What Is Rabies?

Annually, rabies is responsible for over 55,000 human deaths per year globally, and over 99% of these deaths occur in the developing world, most notably, in Asia and Africa. In literature rabies infection is frequently referred to as a ‘neglected disease’ due to the lack of political and financial commitment to combating rabies. The neglect for this zoonotic disease most likely stems from inaccurate public health data diminishing the true impact of the disease.¹ Rabies is a fatal disease which is transmitted through the saliva of an infected animal. The central nervous system (CNS) and the brain are targetted by the virus, and once the infection has been established it is almost certainly fatal. There are 2 manifestations of rabies infection, furious and dumb (these are described further below). Both forms eventually lead to coma and death. However, immediate medical intervention following exposure to rabies virus can prevent the infection from becoming established and spreading to the CNS and brain.² This article contains relevant up to date information on the causes, signs and symptoms, and management and treatment of rabies in addition to answers for a range of frequently asked questions. 

Overview

Rabies is a fatal viral illness that is preventable. It is caused by the rabies virus (RABV) and is transmitted to humans through the saliva of infected mammals. Rabies can be prevented through vaccination. The option of vaccination is applicable to both humans and animals. However, due to issues with affordability and availability of vaccination and treatment, rabies continues to be a serious threat to public health, predominantly in areas with endemic poverty. If an individual becomes infected with rabies and symptoms develop the disease almost always results in death.²

Causes of rabies

Rabies is caused by infection with RABV, this viral disease can be prevented by vaccination. RABV is usually transmitted to humans through exposure of either skin lesions or severe bites to the saliva of an infected animal. All mammals have the potential to carry and transmit rabies, however, dogs are considered to be the main rabies reservoir species infecting humans. 99% of human rabies deaths are accounted for by infection with the canine rabies virus. Typically canine rabies is transmitted via an unprovoked dog bite.³

In Canada, Europe and the United States large scale vaccination programmes have eliminated canine rabies in these regions. These large scale efforts have shown the efficacy of rabies vaccines to eliminate the rabies virus within certain wildlife reservoirs.2 Regions with limited access to dog vaccination programmes including Asia and Africa currently account for over half of the annual global rabies deaths. Within these areas 30-60% of rabies deaths are children below the age of 15.⁴ This is likely due to more frequent interactions children and dogs. Furthermore, children are smaller and therefore have an increased likelihood of a being bitten either on or closer to their head. Bites that are on or closer to the head are associated with a shorter incubation period and an earlier onset of disease. This is because when the virus enters the body it travels via nerves to the brain, once in the brain, the virus multiplies and this is what causes the untreatable fatal disease.²

There have also been rare cases of rabies virus transmission via organ transplantation. This happens when the donor has been undiagnosed with rabies.⁵ 

Once the rabies virus has entered the body, it spreads through nerves to eventually infiltrate the CNS and the brain. Once in the brain the virus multiplies very quickly causing inflammation that results in encephalomyelitis.⁶

Signs and symptoms of rabies

Initial rabies infection may be accompanied by flu like syptoms. As a rabies infection progresses the presentation of the disease is either furious (encephalitic) or dumb (paralytic).3, 7 Patients with furious rabies are hyperactive and erratic, they typically survive a few days from the onset of symptoms. Individuals with paralytic rabies infection slowly become paralyzed, this is then followed by a coma and ultimately death. The progression of this infection is slower and patients will typically survive a few weeks. The World Health Organisation says 20% of human rabies cases are the paralytic form of the infection.

Signs and symptoms of both furious or dumb rabies can include:

• Headaches
• Vomiting/Nausea
• Fever
• Anxiety
• Agitation
• Hallucinations
• Partial paralysis
• Insomnia
• Confusion
• Excessive salivation
• Swallowing difficulty
• Hyperactivity
• Hydrophobia (fear of water)
• Aerophobia (fear of drafts/fresh air)

Management and treatment for rabies

Following exposure to the rabies virus provided to given a rabies vaccine is usually provided. It should be mentioned that rabies vaccines are more effective before RBAV exposure. Having a vaccine prior to exposure in addition to a vaccine post exposure to a rabid animal is 100% effective at preventing a rabies infection taking hold. 

Following a possible rabies exposure treatment typically consists of cleaning the wound (with soap and water or povidone iodine), receiving rabies vaccinations (even if vaccinated prior to exposure) and rabies immune globulin treatment (only given to previously unvaccinated patients). The typical post rabies exposure regime used in the UK is 5 doses of the rabies within 4 weeks. These are administered on days 0, 3, 7, 14 and 28. Rabies immune globulin (RIG) treatment is administered once to patients that prior to rabies exposure are unvaccinated against the disease. It provides immediate antibodies that begin fighting off the viral infection before the body can produce its own antibodies. Currently RIG is not available in several countries and many rural areas due to a global shortage.

Currently there is no specific treatment that has shown any effectiveness once a rabies infection has taken hold. Palliative care is given to patients to ease agonising symptoms.³

FAQs

How is rabies diagnosed

Hydrophobia and aerophobia are strong indicators that a patient may have a rabies infection. Many other infectious and non-infectious diseases share some symptoms with rabies. Therefore, the only way a rabies infection can be confirmed is through diagnostic testing. However, following the diagnosis of rabies, irrespective of early diagnosis, the disease will almost always result in death of the patient.²

Can rabies be prevented?

Rabies is frequently referred to as a disease of poverty and ignorance.² This is because infection with rabies should be entirely preventable through vaccination.³ Rabies is mentioned in the world health organisation’s list of neglected tropical diseases, and is aimed to be eliminated by 2030 provided the goal is adequately financed and supported politically. The vaccination of dogs against rabies and reducing dog bite incidence is the most cost effective strategy for rabies prevention and elimination.

Who is at risk of rabies?

In developed countries the risk of becoming infected with rabies is low. Visiting developing countries puts you at greater risk of contracting rabies. In addition, having a greater exposure to wild animals whether that is through living in a rural area, camping regularly or living in a bat-populated area also increase your risk of contracting rabies.

How common is rabies?

There are 55,000 canine rabies infection deaths recorded annually. It is expected that this figure is much lower than the actual burden the disease. This is due to limited health care services and a lack of education on rabies resulting in the under reporting of human rabies cases.

What animals usually have rabies?

Canine transmitted rabies accounts for >99% of rabies cases reported annually. However, all mammals have the potential to carry and transmit the virus.

When should I see a doctor?

If you are bitten by any animal or suspect you may have been exposed to rabies seek immediate medical attention. If you are unsure whether you or someone you are responsible for has been bitten/licked by an animal you should also seek medical attention. It is important to recieve treatment to prevent a rabies infection taking hold.

Summary

Rabies is a vaccine-preventable disease. It is primarily transmitted through the saliva of infected animals coming into contact with broken skin (minor or major). Rabies infections in humans are usually transmitted through dog bites, however, all wild rabid animals have the potential to spread the disease to humans. If you or someone you know has potentially been exposed to the rabies virus it is important you/they seek immediate medical attention. You can prevent a rabies infection taking hold through appropriate treatment, this includes cleaning the would, post exposure vaccinations and RIG treatment (as required). If rabies symptoms devlop, it indicates the infection has spread to the CNS and brain. Rabies infection develops either into a furious (encephaltic) or dumb (paralytic) form of infection.The dumb form of infection is typically slower progressing than the furious form, however, both almost always result in coma then death of the patient.