Rabies

Rabies is a viral infection of the brain and spinal cord that is almost always fatal. The rabies virus is carried in the saliva of infected animals and is typically transmitted through an animal bite, though contamination of any break in the skin with infected saliva may result in rabies. In developing countries, dog bites are responsible for the overwhelming majority of cases. In developed countries, canine rabies is largely controlled through vaccination and most cases are related to wildlife exposure. In the United States, most cases are attributable to raccoons, skunks, and bats.

The incubation period usually ranges from 20 to 90 days, but may be substantially longer. Initial symptoms may include numbness, tingling, and itching at the site of the healed bite wound, as well as fever, headache, malaise, mood swings, and personality changes. This is followed several days later by hydrophobia (the classic rabies symptom), producing uncontrollable spasms at even the sight of water, as well as aerophobia (fear of air), hallucinations, agitation, and increasing lethargy, progressing inexorably to coma. A smaller number of rabies patients develop paralysis as their main symptom, followed by mental deterioration and coma.

Between 1980 and 1992, ten American travelers died from rabies contracted while abroad, indicating a low but measurable risk. Administration of rabies immune globulin and rabies vaccine after an animal bite or scratch, as described below, is highly effective in preventing rabies. Rabies vaccine before travel is therefore reserved for those at high risk for rabies exposure, such as animal handlers and spelunkers (cave explorers), and for those who may be at risk for animal bites and may not have access to postexposure treatment if necessary, either because they will be visiting remote, inaccessible areas or because supplies of the appropriate biologicals may not be available. Some poorer countries may not have rabies immune globulin or may offer only one of the older, brain-tissue-derived rabies vaccines, which are much less effective than tissue- and avian-culture vaccines, are painful, and sometimes cause neuroparalytic reactions, including meningoencephalitis, mononeuritis multiplex, tranverse myelitis, and ascending paralysis of the Landry type.

Travelers who require rabies vaccine before departure should receive a total of three 1.0-ml doses, injected into the deltoid muscle, on days 0, 7, and 21 or 28. Three types of vaccine are currently licensed in the United States: human diploid cell vaccine (HDCV), rabies vaccine adsorbed (RVA), and purified chick embryo cell vaccine (PCEC). All appear to be safe and effective. The most frequent reaction is pain, swelling, redness, or itching at the injection site. Other side-effects may include headache, nausea, abdominal pain, muscle aches, or dizziness. Allergic reactions are occasionally reported after booster doses of HDCV. The three-dose series appears to be effective for at least two years. Those who remain at risk for rabies two years after immunization should either be tested for rabies antibodies or given a single booster dose of vaccine. Immunosuppressed individuals who receive rabies vaccine should be tested for rabies antibodies before departure.

All animal bites and scratches must be promptly and thoroughly cleaned with large amounts of soap and water, whether or not the person has received rabies vaccine, and the local health authorities should be contacted. If there is a risk for rabies and the victim has not been vaccinated, he or she should immediately receive rabies immune globulin (infiltrating as much as possible into the bite site and giving the remainder intramuscularly) and should immediately start a four dose series of rabies vaccine, to be given on days 0, 3, 7, and 14. (It was previously advised that a fifth dose should be given on day 28, but the U.S. Advisory Committee on Immunization Practices voted in June 2009 to change the recommendation.) Those who have been previously vaccinated should be given a dose of rabies vaccine on days 0 and 3 and no immune globulin. In a country where rabies is endemic, postexposure treatment should be given whether or not the attack was "provoked". Pregnancy is not a contraindication to postexposure treatment.

The only rabies immune globulin available in the United States and Canada is human rabies immune globulin. The recommended dosage after rabies exposure is 20 IU/kg. Two other types of rabies immune globulin, non-pepsin-digested (non-purified) equine rabies immune globulin (ERIG) and ammonium-sulfate-precipitated (purified) ERIG, may be given in other countries. Purified ERIG appears to be considerably safer: only 0.0025% of those receiving it develop anaphylactic (severe allergic) reactions, compared to 3.8% of those receiving the non-purified preparation. The recommended dosage of ERIG is 40 IU/kg.

Antimalarial drugs may interfere with the immune response to rabies vaccine when it is given in a dosage of 0.1 ml by the intradermal route, which is sometimes done to reduce costs. Rabies vaccine should not be given by the intradermal route if there isn't time to complete immunization before starting malaria prophylaxis.

Any traveler who receives treatment for rabies exposure while abroad should be reassessed after returning home.

NOTICE: On April 2, 2004, the manufacturer of IMOVAX Rabies Vaccine (Aventis Pasteur) announced that several lots of vaccine had been found to contain live rabies virus that had not been fully inactivated. In the United States, lot numbers X0667-2, X0667-3, W1419-2, and W1419-3, which were distributed from September 23, 2003 through April 2, 2004, have been recalled. For a list of the lots recalled in other countries, go to the Centers for Disease Control website. No unusual adverse events associated with the recalled vaccine have been reported to date. Health care providers should contact persons who received recalled vaccine and follow the recommendations outlined by the Centers for Disease Control. Any persons who received rabies vaccine between September 23, 2003, and April 2, 2004, should contact their physician to determine if they received vaccine from one of the recalled lots and, if so, whether they need further evaluation. For additional information, contact the Aventis Pasteur Medical Information Services Department, telephone 800-835-3587.

From the World Health Organization (WHO)

Rabies fact sheet

Rabies vaccine

Safety of rabies vaccine

From the Centers for Disease Control

Use of a Reduced (4-Dose) Vaccine Schedule for Postexposure Prophylaxis to Prevent Human Rabies

Human Rabies Prevention - United States, 2008 Recommendations of the Advisory Committee on Immunization Practices (ACIP)

Rabies

Common Questions and Answers about Rabies

CDC Rabies Homepage