Encephalitis explained Types of encephalitis Infectious encephalitis Rabies encephalitis By Alina Ellerington, Encephalitis Society What is rabies? Rabies is a severe acute viral infection of the central nervous system (CNS) that is transmitted by biting animals. Human rabies is a disease with almost 100% fatal outcome (death). Causes Rabies is caused by the rabies virus through a bite from infected animals such as dogs in rabies endemic areas (Africa and Asia) or bat virus rabies variants (North America). There are also reports of human rabies due to bites of cats, mongooses, jackals, foxes, wolves and other carnivorous animals. There is no evidence that rabies is transmitted through the consumption of milk or cooked meat of an infected animal. Although rabies has been successfully controlled in many parts of the world, there are estimated 25,000 deaths every year in Africa with about one death every 20 minutes. Children are at a high risk as they tend to get in contact more frequently with infected animals. Since 1946, 25 cases of human rabies have been reported in the United Kingdom, all associated with exposures to rabid dogs in countries such as the Philippines, Nigeria, India, and South Africa. The virus can’t get through if the skin is intact, but can pass through pre-existent scratches or through intact mucosa (lining of the part of the body that secretes mucus, for example inner lining of the nose). Rabies can’t be transmitted from human to human; the human is the host end. It can be transmitted through transplantation of tissues or organs from someone who died from rabies. Symptoms and diagnosis The incubation period (the time from the infection to the symptoms) may last between 20 to 90 days or even longer, and after this time the virus spreads to the CNS and multiple organs. Early symptoms are often non-specific, mimicking viral infections, although there may be initial neuropathic pain at the site of the bite, weakness of the affected limb or intense pruritus (itching) beginning at the site of the bite and progressing to involve the limb or side of the face. Other symptoms include fever, malaise (general feeling of unwell), headache, intolerance to noise, air or light, anger and depression. Eighty percent of patients then progress to encephalitic rabies (furious rabies), which is characterised by episodes of generalised arousal or hyper-excitability separated by lucid periods, autonomic dysfunction (altered functioning of the heart, bladder, intestines, sweat glands, pupils, and blood vessels), and hydrophobia (fear of water). The remainder develop paralytic rabies with quadriparesis (weakness in all 4 limbs) and sphincter dysfunction which is sometimes difficult to diagnose. It is not known why some patients develop the encephalitic form and others paralytic rabies. Diagnosis is made based on symptoms and history of exposure. Some cases of rabies are misdiagnosed for malaria. Death occurs by cardiac or respiratory failure typically within 7-10 days after the first symptoms, if no intensive care is instituted. Treatment Presently, there are no successful protocol therapies if the patient has developed signs of illness. A protocol treatment (Milwaukee) was suggested after survival of a 15-year old girl who developed signs of the illness. It included a combination of vaccine, antirabies immunoglobulin, antiviral drugs and the anesthetic ketamine plus a drug-induced (therapeutic) coma. Later attempts of the same protocol failed, the success of this therapy in the survival case is more due to an individual immune response, rather than the treatment. Care in hospital for a patient with rabies encephalitis consist of sedation, keeping the patient free from physical pain and emotional support in a quiet room. Intravenous fluids are recommended for the patients with hydrophobia because they become progressively thirsty. Care needs to be taken when dealing with patient saliva. Prevention Rabies is a 100% preventable disease: there is a pre-exposure prevention and a post-exposure prevention. World Health Organisation (WHO) recognises two ways of vaccination: one administered intramuscularly and the other one intradermally. The use of the intradermal immunisation regime is recommended as it requires a smaller quantity of the vaccine than the intramuscular one and gives a better antibody response. The vaccine provides immunity only for a limited period of time, boosters being needed depending on the level of risk. In the event of exposure to rabies, post-exposure prophylaxis (PEP) is still required for those who have received pre-exposure vaccination. Rabies can be effectively prevented after a recognised exposure through post-exposure prophylaxis (PEP) which includes: wound cleansing, active immunisation with multiple doses of rabies vaccine, and passive immunisation with human rabies immuno-globulin injected into and around the wound and intramuscularly. The aim of the PEP is to prevent the virus going into CNS. It is effective only before the signs of the illness develop. Dogs are the main source of transmission of rabies to humans. Mass vaccination of dogs is recognised as the most cost-effective and sustainable way to eliminate rabies in humans. Rabies among travellers Travellers need to be aware of the risk of rabies and take preventive measures which include: knowing if the country they visit is endemic, getting informed about PEP measures in these areas and what to do in case of exposure vaccination before travelling in areas with a high risk avoiding contact with animals; even a bite from what appears to be a harmless pet must be considered carefully. The following risk factors for injury caused by potentially rabid animals may need to be considered: traveling to Southeast Asia, India, and North Africa, young age, and traveling for tourism. Challenges faced by the rabies’ prevention and control Rabies mainly affects poor and marginalised populations. Rabies is a 100% preventable disease. However people are dying of rabies because of lack of education or financial means: people do not know about rabies, what to do in case of exposure or about PEP pre-exposure vaccination or PEP is not available in their area they have no financial means to access pre-exposure vaccination or PEP dog vaccination is difficult to implement in some areas health care professionals haven’t got adequate training There is also a lack of effective preventable human and veterinary programmes and strategies and effective surveillance programmes. Even if rabies is a notifiable disease, the reported data is not accurate. Recent studies have shown an increase incidence of human rabies infection in children in some parts of the world such as Malawi (Africa). In other parts of the world (Latin America) One Health approach (a collaborative way to address animal and public health globally) succeeded in reducing the prevalence of canine rabies and human fatalities nearly vanished. This approach recognised the importance of mass dog vaccination and effective surveillance across human health and veterinary sectors. First Aid in case of a bite recommended by World Health Organisation: wash and flush the wound with soap and water for 10- 15 minutes clean the wound with 70% alcohol/ ethanol or povidone-iodine or a similar antiseptic if available contact a health care facility immediately Other resources Global Alliance for Rabies Control (GARC) World Health Organisation (WHO) NHS (Rabies vaccination within UK) FS040V1 Rabies encephalitis Date created: February 2015; Review date: February 2018 Disclaimer: We try to ensure that the information is easy to understand, accurate and up-to-date as possible. If you would like more information on the source material the author used to write this document please contact the Encephalitis Society. None of the authors of the above document has declared any conflict of interest which may arise from being named as an author of this document.