immunoglobulins

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Rabies

Human Rabies immunoglobulin

Rabies is a highly contagious infection that attacks the central nervous system. It is caused by a virus that enters the body through the bite of an infected animal or through the contact of infected saliva on a cut or graze. The incubation period is usually between 30 and 70 days, although in some cases it can be as short as 9 days or as long as several months. The reason for this incubation time variance depends on the site of the original infection, i.e. a shorter or longer time it takes the virus to reach the spinal cord and brain. Not everyone who is bitten by an infected animal develops rabies. There is little treatment for rabies and once the disease has taken hold it is invariably fatal. If the disease is caught in the incubation period its development may be prevented. The wound or bite should be thoroughly cleaned and then human rabies IgG given. Rabies is very rare in the United Kingdom but is endemic in continental Europe. Vaccines are available to protect vets, farmers and others, whose occupations put them at risk from the disease. There is a specific vaccine available for domestic animals.

Rabies is a rhabdovirus that gets into the central nervous system via the nerves in the skin and surrounding tissues around the bite. The first symptoms are usually those of any flu-like illness (headache, sore throat, and fever), but there may also be altered sensation at the wound site, e.g. numbness, tingling or itching. It would be extremely difficult to diagnose at this point unless the person mentioned the possibility of a bite or other exposure to an animal. These early symptoms may last several days but then would progress to the symptoms most associated with rabies and which are caused by an acute inflammation of the brain (encephalitis). Symptoms include: mental disturbance e.g. confusion, anxiety, agitation, hallucinations; an increase in the amount of saliva causing the typical foaming of the mouth; spasm of the muscles, particularly those at the back of the throat when drinking water, hence the 'fear of water', unsteadiness and a lack of co-ordination; and eventually paralysis. These symptoms may last for 7-10 days and are followed by coma. Death is usually due to heart failure or to an inability to breathe (respiratory failure). There is no effective treatment once the neurological symptoms emerge. Supportive treatment is all that can be offered.

Pre-exposure prophylaxis. Pre-exposure prophylactic immunisation should be offered to those at high risk: laboratory staff who handle the rabies virus, such as those working in quarantine stations; animal handlers; veterinary surgeons and field workers who are likely to be bitten by infected wild animals; certain port officials; and licensed bat handlers. Human transmission of rabies has not been recorded but it is advised that those caring for patients with the disease should be immunised as if they have been exposed. Pre-exposure immunisation is also recommended for those living or travelling, usually for longer than 4 weeks, in areas where rabies is endemic, especially those who will be away from medical facilities or those who may be exposed to unusual risk. Pre-exposure prophylaxis is indicated during pregnancy if there is substantial risk of exposure to rabies. Pre-exposure use requires 3 intramuscular doses of rabies vaccine, with further booster doses for those who remain at continued risk.

Post-exposure prophylaxis. Post-exposure prophylaxis depends on the level of risk in the country, the nature of exposure, and the individual's immune status. Specialist advice must be sought for all bat bites. There are no specific contraindications to the use of a rabies vaccine for post-exposure prophylaxis and its use should be considered whenever a patient has been attacked by an animal in a country where rabies is endemic, even if there is no direct evidence of rabies in the attacking animal. As a result of the potential consequences of untreated rabies exposure and because rabies vaccination has not been associated with fetal abnormalities, pregnancy is not considered a contra-indication to post-exposure prophylaxis.

The use of Human Rabies Immunoglobulin is specified in the World Health Organisation (WHO) guidelines for specific systemic treatment.  These guidelines are outlined in the table below:

Nature of Exposure

 

Status of biting animal

(irrespective of any earlier vaccination)

Recommended

Treatment

At time of exposure

During next 10 days a

 

Contact, but no lesions; indirect contact; non contact

Healthy

 

None

Suspected as rabid b

Healthy

None

Rabid

None

Licks on the skin; scratches or abrasions; Minor bites (on covered areas of arms, trunk and legs)

Healthy

Healthy

None

Rabid

Start vaccination schedule c

Suspected as rabid b

Healthy

Start vaccination schedule; stop treatment if animal remains healthy for 5 days a, d

 

Rabid

Start vaccination schedule; upon positive diagnosis, complete the course of vaccine

Rabid; wild animal e or animal unavailable for observation

 

Give complete course of vaccination

Licks of mucosa; major bites (multiple or on face, head, neck or finger)

Suspect b or confirmed rabid domestic or wild e animal, or animal unavailable for observation.

 

Immunoglobulin and vaccine.  Stop treatment only in the case of domestic animal under observation a which remains healthy for 5 days.

a.       This observation period applies only to dogs and cats. Other domestic and wild animals suspected as rabid should be killed and examined using the fluorescent antibody techniques.

b.       All unprovoked bites in endemic areas should be considered suspect unless proved negative by laboratory examination of the animal's brain.

c.       During the usual period of 10 days, begin treatment with vaccine at first sign of rabies in a dog or cat that has bitten someone.  The symptomatic animal should be killed immediately and examined using the fluorescent antibody technique.

d.       Or if the animal's brain is found to be negative by fluorescent antibody examination.

e.       In general, exposure to rodents, rabbits and hares seldom, if ever, requires specific anti-rabies treatment.

Useful documentation available from the electronic Medicines Compendium (eMC).

PDF Rabies (Patient Information Leaflet)

Patient information leaflets