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Rabies treatment and prophylaxis

Posted Dec 08 2009 12:00am

I recently had an opportunity to discuss a very old and deadly disease with some patients…Rabies.  Rabies is a viral disease that is 99.99% fatal if acquired and should be taken very seriously.  A problem that is faced by adventure travelers and those who typically travel in more developing nations, having a plan to deal with a potential rabies exposure should be part of every traveler’s “what if” scenario.

Infectious Agent:  Rabies is a rhabdovirus of the genus Lyssavirus.  There are also several “rabies related viruses” in the Lyssavirus group with similar presentations to rabies (Mekola, Duvenhague and Australian bat lyssavirus).   

Location and occurence:  Worldwide an estimated 65,000 to 87,000 deaths per year with the majority of cases occurring in Asia and Africa. 

Treatment:  Since there is little hope of treating “full-blown” rabies once infected, treatment centers around the prompt administration of rabies post-exposure treatment before the infection has a chance to progress. 

Prevention:  Fortunately a series of injections/immunizations exists to help prevent rabies, before being bitten.  This series of immunizations is known as Rabies pre-exposure prophylaxis.  Children and their natural affinity and curiosity to animals should be considered a special risk.  Strict education on not approaching strange dogs is vital for the traveling family.   

So I have been bitten by a strange dog while riding my bike in a far away land…Now what?!

As with any wound, a good cleaning and first aid should be the first thing that gets done.  Bleeding from the wound usually stops with a bit of direct pressure over the site, using some gauze or a cloth compress.  A 20% soap and water solution or benzalkonium chloride towelettes make a decent choice for cleaning the wound.  Simply flushing the wound with the soapy water is not good enough and there should be several minutes of contact time between the wound and either soapy water or benzalkonium.  After several minutes, wash the cleaning solution off the wound.  If nothing else is available, a good scrubbing of the wound with soap and water is considered better than nothing.  Now comes the decision time…To seek post-exposure treatment for rabies or not.

Remembering that rabies is a fatal disease with very rare reports of people living through the illness, an extremely low threshold for seeking treatment should be advised.  Some experts advise an attempt to capture the animal for a 10 day quarantine period to observe the animal for strange behavior indicating rabies infection.  This is not always realistic, in my opinion.  A true diagnosis of rabies can only be made by examining the brain tissue of the animal, after death.  This determination should be made by a trained professional such as a pathologist or veterinarian. 

Doctors divide those who have had a potential rabies exposure into two groups:  Those who have had pre-exposure prophylaxis and those who have not.  Any type of exposure require treatment after their bite encounter, but the treatment is different depending on your prior immunization history.  Having already had the pre-exposure vaccine simplifies the process of protection.  A person who has been previously vaccinated against rabies simply needs less injections after their bite and only receives the vaccine, not the immune globulin.  Without pre-exposure vaccination, a person should be given “double treatment” with both Rabies Immunue-globulin (RIG) and a five dose series of injections for the rabies vaccine.   

Rabies Pre-Exposure Prophylaxis

The rabies virus vaccine is an inactivated vaccine meaning that the parts of the virus that can cause disease in humans have been removed or disabled.  You cannot get rabies from the vaccine.  There are several different commercial vaccine available.  A total of three doses of the vaccine are given as an intra-muscular injections.  The first dose and second dose are separated by a week in time and the last dose is given 3-4 weeks after the first.  This means that a traveler should begin their vaccine schedule at least one month prior to travel.  Common side-effects and reactions to the vaccine include some swelling and local pain at the injection site.  Travelers who have previously had their vaccine series and are planning travel to a “high risk area” or a higher risk style of travel should have their antibody titers checked every two years and may benefit from a booster.  Some types fo travelers with continuous risk, such as cavers or animal handlers may need titers checked every 6 months. 

Travelers who have had their pre-exposure prophylaxis should be given two additional doses of the vaccine, three days apart, if potentially exposed to rabies.  This is in addition to a proper cleaning fo the wound as mentioned above. 

Rabies Post-Exposure Treatment

A traveler or person who is previously unprotected and receives a bite or exposure to rabies should be treated with Rabies Immune Globulin (RIG) in addition to a 5 dose series of the rabies vaccine.  Typically, the RIG is given as quickly as possible after the bite/exposure.  Rabies immune-globulin (RIG) is commonly injected into the tissue surrounding the bite or wound.  If the wound is on a small body part such as a finger, one should inject as much of the RIG as possible into the area and the remainder of the RIG should be given into a distant site on the opposite side of the body such as the thigh or upper/outer quadrant of the buttocks.

After the RIG is administered, the rabies vaccine should be administered.  The point of this two-step process is to give the RIG for neutralizing active rabies virus in the blood, directly from the bite.  The vaccine is then given to allow for the body to produce its own antibodies to the virus, which takes several days.  The RIG protects the body while the antibodies from the vaccine develop.  The rabies vaccine is commonly given as a five dose series on days 0, 3, 7, 14, and 28, all as intramuscular injections.  The days of “rabies shots in the stomach” are thankfully gone!

Potential Problems

As one can see, the pre-exposure prophylaxis makes life much easier should there be a rabies exposure.  Other concerns include the availability of Rabies Immune Globulin in the are of the world that you are traveling.  There is currently a world-wide shortage of RIG and it is difficult to obtain.  There is a real chance that RIG is simply unavailable in the are where you were bitten.  Perhaps of more concern is that some developing nations use an older version of RIG that are animal derivatives , chiefly from horses, ducks or rats.  These products have a much higher risk of serum sickness reactions when compared to the RIG that is used in developed nations.

An outstanding lecture I heard several years ago discussed this problem and described the situation very succinctly.  A bite from an unknown animal will effectively stop your trip, right there and then.  The person must immediately seek medical care and proper protection against rabies.  This may mean several days travel to a major city, perhaps out of that country entirely.  This is typically at a great expense due to the need for immediate travel.  Once proper treatment can be located, the traveler must then complete the series of injections there or attempt to find another suitable clinic “further down the road”.  Basically, the dream trip that you have been waiting for has now become an international rabies treatment hunt. 

Ultimately, the decision to receive a vaccine or follow any advice is up to the individual traveler.  Special attention should be payed to personal risk of animal exposures, location and access to medical care in the area of travel and complications that may affect the trip when seeking such medical care.  These risks should be discussed with a travel/expedition healthcare provider, well in advance of your trip.

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