Risks of travel, benefits of a specialist consult

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While many travelers can confidently consult their primary care provider, those traveling to places where malaria is prevalent should be referred to a physician with a thorough and current knowledge of the incidence of drugresistant strains of the disease and other complex issues in travel medicine. Short-term and long-term travelers are often approached differently, but a travel medicine consult should be obtained for any patient traveling to a region with malaria risk.

Based on data from the US Centers for Disease Control and Prevention.

Figure 1. Global distribution of malaria, and reported areas of drug resistance.

Geographically, the areas where most of the other diseases described below pose a risk overlap with the areas where malaria is endemic, and specialists at a travel clinic will know, based on the traveler’s itinerary, what additional immunizations are recommended or required. Malaria is endemic in much of South America, sub-Saharan Africa, the Indian subcontinent, Southeast Asia, parts of the Middle East, the west coast of Mexico, and southern China (Figure 1).

Malaria kills up to 3 million each year

Malaria, caused by the Plasmodium parasite, transmitted by the night-biting Anopheles mosquito, is responsible worldwide for between 1 and 3 million deaths annually, mostly of children in sub-Saharan Africa.15 Every year about 1,500 Americans are diagnosed with malaria and, on average, 10 die.6

Nearly all cases of malaria and deaths from it are preventable. Prophylaxis is imperative for travelers to affected areas, as is preventive counseling. Based on the patient’s itinerary, the physician needs to thoroughly research potential exposure to drug-resistant strains before choosing which antimalarial regimen to prescribe.

Malaria causes symptoms of anemia, fever, or nausea and, without treatment, can lead to coma and death. Because two of the five strains, P vivax and P ovale, can remain dormant in an infected person’s liver for up to 1 year and, in rare cases, up to 4 years after travel, it is imperative that a returned traveler who experiences flu-like symptoms seek medical attention and inform the treating physician of the need to screen for malarial infection. The primary means of diagnosis is through microscopic examination of the blood.

No malaria vaccine, but prophylactic drugs are available

Unlike many of the illnesses discussed below for which vaccines are available, malaria prophylaxis requires the active participation of the patient in completing a course of medication, so noncompliance becomes a risk.

A number of prophylactic drugs are available. The choice depends on the locally resistant strains.16

Chloroquine (Aralen), the traditional malarial prophylactic drug, is still effective against many strains, primarily in Central America and some areas of the Middle East. The dosage is 500 mg once a week, started 1 week before travel and continued for 4 weeks after return to the United States.

Mefloquine (Lariam) is dosed at 250 mg weekly. The patient should be carefully screened for depression, anxiety, and other mood disorders. Even the report of bad dreams or nightmares should make a patient be considered a poor candidate for this medication. The patient should start taking this drug 3 weeks before travel to provide time to assess for adverse effects and, if necessary, to change the antimalarial regimen. Mefloquine is taken weekly while traveling and is continued for 4 weeks after return.

Doxycycline (Vibramycin) is an antibiotic. As an antimalarial prophylactic, it is taken as 100 mg daily beginning 2 days prior to travel and continuing while travelling and for 4 weeks after return.

Atovaquone-proguanil (Malarone) prevents infection at the blood stage and in the liver. It is well tolerated and is begun 2 days before travel. It is taken daily while traveling and daily for 1 week after return.

Yellow fever

From the US Centers for Disease Control and Prevention.

Figure 2. Approximate global distribution of yellow fever (2007 data).

Yellow fever is spread by the day-biting Aedes aegypti mosquito. It is prevalent in equatorial Africa and South America (Figure 2).

Immunization is required for entry to more than 20 African nations and is recommended for those traveling to most of South America. The only physicians who can give this vaccine are those who have approval from their state health department and have been issued an official stamp, used on the World Health Organization (WHO) yellow fever vaccination card. Several countries require the card for entry from places where yellow fever is present. For any multicountry travel involving at least one area where yellow fever is endemic, the entire itinerary needs to be reviewed to make sure all legal entry requirements are met. The WHO maintains a current list of these requirements.17 If there is any doubt, it is generally best to refer and certify the traveler.

Referral should be timely. The vaccine must be given 10 days prior to entry into a country where yellow fever is endemic; it is valid for 10 years.

The yellow fever vaccine is a live-attenuated vaccine and should not be given to infants younger than 9 months old, adults over age 60 who are not properly screened and informed, or pregnant women. Immunocompromised patients are excluded from receiving this vaccine, as are patients taking immunosuppressant drugs and patients with thymus disorders such as myasthenia gravis. Patients who have had chemotherapy must wait 3 months before being vaccinated. Those on steroids (eg, prednisone 20 mg or more daily) must wait until 2 weeks after cessation of steroids to receive this vaccine. Patients who cannot be vaccinated should be advised not to travel to areas with a high risk of yellow fever.

Women contemplating pregnancy should use contraception for 28 days after yellow fever vaccination. Children younger than 9 months and the elderly are at higher risk of adverse reactions from the vaccine, either neurotropic or viscerotropic disease that mimics yellow fever infection. It is possible for physicians to write a medical waiver of contraindication to vaccination for patients who should not be immunized.

Typhoid fever

Typhoid fever can occur anywhere in the world, but it is endemic in the tropics. Worldwide, an estimated 200,000 deaths occur each year from typhoid fever, and 400 cases are reported annually in the United States, most commonly acquired by travelers to the Indian subcontinent.18 One study indicates that 95% of infected travelers had not been vaccinated, and a significant number returned with drugresistant strains.19

Typhoid fever is caused by ingestion of Salmonella typhi bacteria. It causes a febrile illness with infection of the digestive tract and reticuloendothelial system.

Prevention is the same as for traveler’s diarrhea: drink no local water and eat nothing raw. Vaccination can be provided in an intramuscular shot or a series of oral capsules. The shot is well tolerated and is valid for 3 years. The capsule provides 5 years of immunity. Vaccination is recommended for people going to areas with a high prevalence of typhoid fever, such as India, and for people planning to spend more than 2 weeks in an area where typhoid is endemic, as well as for adventurous eaters.

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