Prophylaxis of Infection in Travelers
James W. Myers
Paras Patel
INTRODUCTION
If possible, the initial consultation about travel abroad should occur at least 6 weeks to 2 months before the patient’s departure date to allow adequate time to give the appropriate immunizations and for assessment of any serious reactions.
Patients may have special needs that require additional pretravel interventions or cause modifications to their itineraries.
For example travel, particularly to developing countries, can carry significant risks for exposure to opportunistic pathogens for HIV-infected travelers, especially those who are severely immunosuppressed.
Also counseling about preventing sexually transmitted diseases (STDs) may be helpful, given that many travelers may acquire a STD abroad.
The pretravel history should include information about the places the patient plans to visit, the season of the year, and the duration of the trip.
Ideally, one should review the patient’s vaccination status at this time.
Routine immunizations that need to be evaluated would include the pneumococcal vaccine, measles, mumps and rubella, polio, tetanus, varicella, and influenza.
Recommendations for adult vaccinations may be found on the Centers for Disease Control and Prevention (CDC) Web site listed in Table 20-1.
Issues regarding safe consumption of water need to be addressed at the pretravel visit.
Only boiled water, hot beverages (such as coffee or tea), canned or bottled carbonated beverages, beer, and wine can be considered safe.
A common error committed by travelers is to add ice to their soft drinks.
Ice may be made from unsafe water and should be avoided if possible.
As an alternative to boiling, chemical disinfection can be achieved with either iodine or chlorine.
As a general rule, if you can peel fruit yourself, it is safe.
Foods that are more worrisome include salads, uncooked vegetables and fruit, unpasteurized milk and milk products, raw meat, and shellfish.
The traveler is at risk to acquire salmonellosis, toxoplasmosis, trichinosis, or cysticercosis from inadequately cooked meat; salmonellosis, shigellosis, leptospirosis, amebiasis, giardiasis, dracunculiasis, or hepatitis A from contaminated ice cubes or drinking water; brucellosis, salmonellosis, campylobacteriosis, or tuberculosis from unpasteurized milk or milk products, including cheese and ice cream; and salmonellosis, hepatitis A, fish roundworm infection, gnathostomiasis, or infection with liver or lung flukes from raw or undercooked fish or shellfish.
Table 20-1 Useful Web Sites
Adult vaccination
http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5140a5.htm
DEET
http://www.deet.com
Travel vaccines
http://www.cdc.gov/travel/vaccinat.htm
Mosquito protection
http://www.cdc.gov/travel/bugs.htm
Destination information
http://www.cdc.gov/travel/destinat.htm
Specific information for travel-related infections
http://www.cdc.gov/travel/destinat.htm
Safe food and water
http://www.cdc.gov/travel/foodwater.htm
Travel clinics
http://www.cdc.gov/travel/travel_clinics.htm
International Society of Travel Medicine
http://www.istm.org/
The American Society of Tropical Medicine and Hygiene
http://www.astmh.org/
U.S. State Department
http://travel.state.gov/
WHO
http://www.who.int/en/
CDC malaria site
http://www.cdc.gov/travel/yb/index.htm
Special travel needs
http://www.cdc.gov/travel/spec_needs.htm
Alternate CDC malaria site
http://www.cdc.gov/malaria/
Malaria pocket guide
http://www.vnh.org/Malaria/Malaria.html
Diarrhea site
http://www.travelhealthline.com/z_diarrhea.html
Some fish are not guaranteed to be safe even when cooked because of the presence of toxins in their flesh. Some species of fish and shellfish can contain poisonous biotoxins, even when well cooked. The most common type of biotoxin in fish is ciguatoxin. The barracuda and puffer fish are usually toxic, and should be avoided. Tropical reef fish, red snapper, amber jack, grouper, and sea bass can occasionally be toxic as well.
DIARRHEA
Please see chapter on diarrhea for information on this subject.
INSECTS
Many travel-related illnesses, such as malaria and dengue fever, are transmitted by insect vectors. Precautions against infection include the use of insect repellents, mosquito netting, and screened windows.
Insect repellents should be applied only to exposed skin and should be washed off as soon as possible after exposure.
They should contain DEET (30% to 35% diethylmethylbenzamide). The DEET concentration alone may not predict toxicity, but a standard maximum concentration of 10% for children and 30% for adults usually provides hours of safe protection without significant toxicity. Light, long-sleeved clothing and long pants should be worn where appropriate, and pants should be tucked into socks.
Permethrin-coated clothing and bed nets provide additional protection against insects.
DEET is far less toxic than many people believe.
Adverse effects, though documented, are infrequent and are generally associated with gross overuse of the product.
The risk of DEET-related adverse effects pales in comparison with the risk of acquiring vector-borne infection in places where such diseases are endemic.
More information about DEET can be found in Table 20-1.
VACCINATIONS
General information about vaccination requirements for adults can be found on the CDC Web site. Specific requirements for certain countries can be found there as well. Pretravel counseling is a good time to do routine health maintenance, including vaccination status for some patients.
See Table 20-2 for list of recommended vaccines, dose, and indication.
Table 20-2 Drugs for the Prevention of Malaria | ||||||||||||||||||
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HEPATITIS A AND B
Hepatitis A and B can be prevented by vaccines, and both have widely overlapping epidemiologic distribution.
The disease endemicity in the travel destination, the duration and frequency of travel, the activities to be undertaken, and the purpose of the travel are the risk factors for hepatitis A virus (HAV) and HBV infection in the travelers.
Travelers requiring medical care while traveling are at increased risk for blood-borne virus, such as HBV.
The risk of hepatitis A in nonimmune travelers to developing countries has been estimated at 1 per 1,000 travelers per week for most tourists, but as high as 1 per 200 per week for backpackers.
As a result, the CDC recommends hepatitis A vaccine be given for all international travelers except those going to low-risk countries such as Canada, Australia, New Zealand, Japan, or most of western Europe.
Hepatitis A and B vaccines are available either as monovalent formulations or in various combinations.
HAVRIX is formulated with 2-phenoxyethanol as a preservative, unlike VAQTA, which is formulated without a preservative.
These two vaccines are available in pediatric (ages 2 to 18) and adult (older than age18) formulations, administered intramuscularly in a two-dose schedule.
Also a combination hepatitis A and hepatitis B vaccine (TWINRIX, GlaxoSmith-Kline) is available, and it contains 720 ELU of HAV antigen and 20 µg of recombinant hepatitis B surface antigen.
Unlike the previous vaccines, the combination vaccine is given as a three-dose schedule.
Hepatitis B vaccine is produced by two manufacturers in the United States, Merck (Recombivax HB) and GlaxoSmithKline Pharmaceuticals (Engerix-B). Both vaccines are available in both pediatric and adult formulations.
Hepatitis B vaccine is recommended for international travelers to regions with high or intermediate levels (HBsAg prevalence of 2% or higher) of endemic HBV infection and persons with HIV infection.
The standard primary course of hepatitis B vaccination consists of three doses, with doses administered at 0, 1, and 6 months. A short 0-, 1-, and 2- month schedule and an accelerated 0-, 7-, and 21-day schedule also exist, with a fourth dose recommended at 12 months in both schedules.
Immune globulin (IG) is effective, providing 85% to 90% protection, but provides only short-term (i.e., months) protection.
In general, even a single dose of the vaccine induces higher levels of antibodies than achieved with use of IG, but lower than levels induced by natural infection.
However, levels of neutralizing antibodies are lower immediately after active immunization than after administration of IG.
Antibody production is somewhat slower and antibody levels are lower when IG and vaccine are given simultaneously, but still reach protective levels in healthy adults.
Testing for antibodies to hepatitis A after vaccination to assess for adequacy of response is not recommended.
Commercially available tests for hepatitis A antibodies were developed to assess immunity to natural infection, so the vaccine does not cause a long-lasting falsepositive result or diagnostic dilemmas.
Protection from the vaccine is expected to be long lasting.
Exposure to wild virus after receiving the vaccine will most likely lead to a booster effect.
Mathematical models have predicted that protective levels of antibodies will persist for 24 to 47 years, with an average annual decrease of 25% in anti-HAV.
Nevertheless, long-term follow-up studies are required to assess duration of protection.
MENINGOCOCCAL MENINGITIS
There are five major meningococcal serogroups, A, B, C, Y, and W-135, that are associated with disease.
It is transmitted from person to person by close contact with respiratory secretions or saliva.
Vaccine is indicated in people traveling to the “meningitis belt” of sub-Saharan Africa during December to June as well as Mecca during the annual Hajj and Umrah pilgrimages.
Serogroup A infection predominates in the meningitis belt, although serogroups C, X, and W-135 are also found.
Two quadrivalent meningococcal polysaccharide-protein conjugate vaccines (Men-ACWY) (Menactra, Menveo) are licensed for use in the United States.
A one-dose primary series of MenACWY-D (Menactra) is licensed for people aged 2 to 55 years; a two-dose primary series of MenACWY-D is licensed for children aged 9 to 23 months. MenACWY-Crm (Menveo) is licensed for people aged 2 to 55 years.
Quadrivalent meningococcal polysaccharide vaccine (MPVS4) (Menomune) is licensed for use among people aged ≥2 years. These vaccines protect against meningococcal disease caused by serogroups A, C, Y, and W-135.
Approximately, 7 to 10 days are required after vaccination for development of protective antibody levels.
MenACWY-D is the only meningococcal vaccine licensed for children aged 9 to 23 months.
Using either one of the MenACWY vaccines is preferred for people aged 2 to 55 years; MPSV4 should be used for people >55 years.
There is no licensed vaccine for infants <9 months in the United States.
RABIES
Rabies is a disease caused by neurotropic viruses in the family Rhabdoviridae and present with an acute, progressive, fatal encephalomyelitis.
Travelers to rabies-enzootic countries should be warned about the risk of acquiring rabies and educated in animal bite-prevention strategies.
Travelers should avoid stray animals, be aware of their surroundings so that they do not accidentally surprise a stray dog, avoid contact with bats and other wildlife, and not carry or eat food while nonhuman primates are near.
Rabies is a disease of both domestic and wild mammals, particularly dogs and related species, raccoons, mongooses, skunks, and bats.
Although often thought of as being a domestic illness, rabies prevention should be part of pretravel counseling.
In Asia, Africa, Russia, Latin America, and other countries, dogs are the vector of rabies.
Preexposure rabies vaccine may be recommended, based on the prevalence of rabies in the country to be visited, the availability of appropriate antirabies biologics, intended activities, and duration of stay.
A decision to receive preexposure rabies immunization may also be based on the likelihood of repeat travel to at-risk destinations or taking up residence in a high-risk destination.
Preexposure vaccination may be recommended for veterinarians, animal handlers, field biologists, cavers, missionaries, and certain laboratory workers
Preexposure vaccination may be used for those who may come in contact with the virus or rabid animals
Travelers should be aware that appropriate postexposure prophylaxis (PEP) treatment might unfortunately not be available in most of the third world.
Also, neurologic complications associated with Semple (sheep brain-derived) vaccine may be as high as 1 case per 200 recipients.
Postexposure management includes immediate wound washing, followed by the use of human or equine rabies immunoglobulin (HRIG or ERIG) and a World Health Organization (WHO)-approved vaccination series.
The postexposure regimen recommended in the United States and by WHO is rabies immune globulin (RIG) on day 0 and human diploid cell rabies vaccine (HDCV) on each of days 0, 3,7 and 14; 1 mL of vaccine is administered intramuscularly in the deltoid area only.
To be optimally effective, RIG must be injected into and around wounds to neutralize virus before it enters peripheral nerves, where, once established, it is in an immune-protected environment.
Vaccines require up to 10 days to induce detectable neutralizing antibodies in most patients.
Because chloroquine may cause interference with the immune response, WHO recommends that preexposure treatment should be administered intramuscularly when a patient is receiving malaria prophylaxis concurrently.
Those who have received prior preexposure or postexposure treatment with a cellculture vaccine, or those who have proven viral neutralizing antibody (VNA) to rabies after other vaccines, should receive an intramuscular injection on each of days 0 and 3, without RIG.
JAPANESE B ENCEPHALITIS
The risk of Japanese B encephalitis (JE) virus infection appears to be very low for most travelers despite the fact that almost 50,000 cases are reported annually.
JE is a mosquito-transmitted viral infection that is endemic in rural parts of Asia.
The risk is felt to be highest in China, Korea, the Indian subcontinent, and Southeast Asia, especially in areas where pig farming is common.
Occasionally, cases have been reported in Japan, Hong Kong, southeastern Russia, Singapore, Malaysia, the Philippines, Taiwan, and parts of Oceania.
Most infections are asymptomatic, but among people who develop a clinical illness, the case-fatality rate can be as high as 30%.
Neuropsychiatric sequelae are reported in 50% of survivors. A higher case-fatality rate is usually reported in older persons.
Both domestic pigs and wild birds serve as the reservoirs of this infection, with Culex mosquitoes being the principal vectors.
This species of mosquito feeds outdoors beginning at dusk and during evening hours until dawn. Larvae are typically found in flooded rice fields, marshes, and small stable collections of water around cultivated fields.
In temperate zones, the vectors are present in greatest numbers from June through September and are inactive during winter months.
Individuals visiting endemic areas for stays of longer than 30 days are candidates for vaccination.
Short-term travelers who engage in outdoor activities with exposure to mosquito bites and long-term travelers going to endemic areas for more than 1 month should follow personal insect precautions, including the use of bed nets and insect repellents when outdoors.
At the time of this publication, only one JE vaccine is licensed in the United States.
It is an inactivated Vero cell-culture-derived vaccine (Ixiaro).
This vaccine is made by Novartis Vaccines
It was approved in March 2009 for use in people aged ≥17 years.
JE-Vax, an inactivated mouse brain-derived vaccine with significant side effects has been discontinued. Pain and tenderness are the most common side effects of the Ixiaro vaccine, as it is much better tolerated than the older vaccine.
The primary immunization schedule for Ixiaro is two doses administered intramuscularly on days 0 and 28. The dose is 0.5 mL for people aged ≥17 years, and the two-dose series should be completed ≥1 week before travel. If the primary series of Ixiaro was administered ≥1 year previously, a booster dose should be given prior to potential reexposure.Related posts:
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