SOME TRAVELERS NEED MORE PROTECTION
Some travelers need more preventive measures than typical tourists or other short-term visitors. Long-term visitors or travelers to remote or other high-risk areas (eg, adventure travelers, relief workers, mission workers) may need, in addition to the measures described above, measures against Japanese encephalitis, rabies, cholera, epidemic meningitis, and dengue fever.
Japanese encephalitis virus is transmitted by mosquito bite. The major regions where it is endemic are rural India and Southeast Asia, most typically in areas with rice paddies and pig farms. Travelers at risk are expatriates to these areas, those planning a long stay, and remote-adventure travelers.
The vaccine JE-VAX is given as a series of three shots, on days 0, 7, and 28. Another vaccine, Ixiaro, is given in a series of two shots, on days 0 and 28.
Patients who are allergic to bee or wasp stings should not be vaccinated. The patient should remain in the office for 30 minutes after each dose to permit observation for mild anaphylactic reactions such as angioedema and urticaria, and should complete the series 10 days before travel to allow for observation for delayed reactions. Patients must weigh the risk of contracting the disease against the high cost of the vaccine.
Rabies is a potential risk anywhere in the world except in Western Europe and Australia. Because the vaccine is costly, it is generally not given for prophylaxis except for travelers certain to have contact with animals, especially the major vectors, ie, dogs, cats, bats, and monkeys.20 Counseling about vigilance in avoiding animal contact and not promoting interaction through feeding wild animals should be part of any pretravel consult. Rabies, once acquired, is fatal.
The patient should be instructed on proper care of a bite from a potential rabies source and told to halt travel and seek medical attention. The wound should be cleaned with soap and water for 15 minutes to remove any saliva and virus from the soft tissue; this has proven to be effective in animal experiments. A virucidal such as benzalkonium chloride (Zephiran) or aqueous iodine should then be put in the wound.
Preexposure vaccination is done in a three-dose series (given on days 0, 7, and 21– 28). The patient should complete the series and adhere to the dosing schedule as closely as possible. It may be necessary to find a source of vaccine for the patient once he or she has arrived in the destination country.
If bitten, travelers without preexposure vaccination must find a source of vaccine and human rabies immune globulin (HRIG) before continuing on their trip. Postexposure treatment is 20 IU/kg of HRIG infiltrated around the wound to wall off the virus inoculation site. If the wound is in a digit or small area and not all of the HRIG can be given, then the remaining HRIG is given intramuscularly at a site distant from the vaccine site. If the patient has multiple bites, the HRIG should be diluted so it can be infiltrated around all wounds. The HRIG should be given immediately or within 7 days of beginning the vaccine series once a source is located. Later treatment than this can interfere with the patient’s ability to mount an immune reaction.
Rabies vaccine is initiated at the same time as HRIG and is given on days 0, 3, 7, 14, and 28. The CDC may soon change the schedule to allow for only four postexposure shots, but this has not yet been done as of this writing.
The patient vaccinated before exposure requires only booster doses of rabies vaccine at days 0 and 3.
Cholera is an epidemic gastrointestinal disease historically responsible for millions of deaths. It is endemic in most tropical countries, especially in Africa and southern and southeastern Asia.21
High-risk patients, most often those working with refugees and disaster victims in endemic areas, should receive the traveler’s diarrhea and cholera vaccine Dukoral, which immunizes against Vibrio cholera and enterotoxogenic E coli. The vaccine, which is not available in the United States but is available abroad, is given as two oral doses 1 week apart for adults and three oral doses for children ages 2 to 6, and the second dose must be given 7 days before travel; this provides protection for 6 months.
At various times, the above vaccines have been in short supply. Travel medicine consults should be obtained for proper identification of the at-risk traveler for efficient use of any possibly limited vaccine.
The vaccine against epidemic meningitis is now routinely given in the United States to adolescents at the age of 12 or upon entry to college or the military. The fatality rate from the disease is 10%.
Meningococcal disease transmission peaks in the sub-Saharan “meningitis belt” in the dry season of December through June. Travelers to these areas at these times should be immunized. Travelers planning close contact with the local population (eg, health care workers) should be immunized. Patients traveling to Saudi Arabia for Hajj in Mecca must be immunized for meningitis for entry to the country during this time. The vaccine must be given within 3 years of entering the country and not less than 10 days before.
Dengue fever is a flavivirus transmitted through the Aedes aegypti mosquito. No vaccine is available for dengue fever, so for now the only advice is to avoid insect vectors.
There are four closely related but serologically different dengue viruses that provide only weak cross-protection. In fact, previous infection with one serotype in a traveler then infected with another poses a risk of dengue hemorrhagic fever.
Because of inattention to public sanitation, this virus and its mosquito vector have reemerged in areas where they were once eliminated. The viral infection is a risk for the traveler to both urban and rural areas in the Americas, Southeast Asia, and Africa. The Pan American Health Organization has seen the number of reported dengue cases increase from 66,000 in 1980 to 700,000 in 2003.22