Chapter 3Infectious Diseases Related To Travel
Barbara L. Herwaldt, Alan J. Magill
Leishmaniasis is a parasitic disease found in parts of the tropics, subtropics, and southern Europe. Leishmaniasis has several different forms. This section focuses on cutaneous leishmaniasis (CL), the most common form, both in general and in travelers.
Leishmaniasis is caused by obligate intracellular protozoan parasites; approximately 20 Leishmania species cause CL.
MODE OF TRANSMISSION
CL is transmitted through the bite of infected female phlebotomine sand flies. CL also can occur after accidental occupational (laboratory) exposures to Leishmania parasites.
In the Old World (Eastern Hemisphere), CL is found in parts of the Middle East, Asia (particularly southwest and central Asia), Africa (particularly the tropical region and North Africa), and southern Europe. In the New World (Western Hemisphere), CL is found in parts of Mexico, Central America, and South America. Occasional cases have been reported in Texas and Oklahoma. CL is not found in Chile, Uruguay, or Canada. Overall, CL is found in focal areas of about 90 countries. Most (>90%) of the world’s cases of CL occur in 10 countries: Afghanistan, Algeria, Iran, Iraq, Saudi Arabia, and Syria in the Old World; and Bolivia, Brazil, Colombia, and Peru in the New World.
The geographic distribution of cases of CL evaluated in countries such as the United States reflects travel and immigration patterns. More than 75% of the cases diagnosed in US civilians have been acquired in Latin America, including popular tourist destinations such as Costa Rica. Cases in US service personnel reflect military activities (in Iraq, for example). CL is usually more common in rural than urban areas, but it is found in some periurban and urban areas (such as in Baghdad, Iraq, and Kabul, Afghanistan). The ecologic settings range from rainforests to arid regions.
The risk is highest from dusk to dawn because sand flies typically feed (bite) at night and during twilight hours. Although sand flies are less active during the hottest time of the day, they may bite if they are disturbed (for example, if hikers brush up against tree trunks or other sites where sand flies are resting). Vector activity can easily be overlooked: sand flies do not make noise, they are small (approximately one-third the size of mosquitoes), and their bites might not be noticed.
Examples of types of travelers who might have an increased risk for CL include ecotourists, adventure travelers, bird watchers, Peace Corps volunteers, missionaries, soldiers, construction workers, and people who do research outdoors at night or twilight. However, even short-term travelers in endemic areas have developed CL.
CL is characterized by skin lesions (open or closed sores), which typically develop within several weeks or months after exposure. In some people, the sores first appear months or years later, in the context of trauma (such as skin wounds or surgery). The sores can change in size and appearance over time. They typically progress from small papules to nodular plaques, and eventually lead to open sores with a raised border and central crater (ulcer), which can be covered with scales or crust. The lesions usually are painless but can be painful, particularly if open sores become infected with bacteria. Satellite lesions, regional lymphadenopathy (swollen glands), and nodular lymphangitis can be noted. The sores usually heal eventually, even without treatment. However, they can last for months or years and typically result in scarring.
Another potential concern applies to some of the Leishmania species in South and Central America—occasionally, these parasites spread from the skin to the mucosal surfaces of the nose or mouth and cause sores there. This form of leishmaniasis, mucosal leishmaniasis (ML), might not be noticed until years after the original skin sores appear to have healed. Although ML is uncommon, it has occurred in travelers and expatriates whose cases of CL were not treated or were inadequately treated. The initial clinical manifestations typically involve the nose (chronic stuffiness, bleeding, and inflamed mucosa or sores) and less often the mouth; in advanced cases, ulcerative destruction of the nose, mouth, and pharynx can be noted (such as perforation of the nasal septum).
Clinicians should consider CL in people with chronic (nonhealing) skin lesions who have been in areas where leishmaniasis is found. Laboratory confirmation of the diagnosis is achieved by detecting Leishmania parasites (or DNA) in infected tissue, through light-microscopic examination of stained specimens, culture techniques, or molecular methods.
CDC can assist in all aspects of the diagnostic evaluation. Identification of the Leishmania species can be important, particularly if more than one species is found where the patient traveled and if the species can have different clinical and prognostic implications. Serologic testing generally is not useful for CL but can provide supportive evidence for the diagnosis of ML.
For consultative services, contact CDC Public Inquiries (404-718-4745; firstname.lastname@example.org). Additional information can be found on the CDC website at www.cdc.gov/parasites/leishmaniasis.
Decisions about whether and how to treat CL should be individualized. All cases of ML should be treated. Clinicians may consult with CDC staff about the relative merits of various approaches (see the Diagnosis section above for contact information).
The pentavalent antimonial compound sodium stibogluconate (Pentostam) is available to US-licensed physicians through the CDC Drug Service (404-639-3670) for intravenous or intramuscular administration under an investigational new drug protocol (see www.cdc.gov/laboratory/drugservice/index.html).
PREVENTIVE MEASURES FOR TRAVELERS
No vaccines or drugs to prevent infection are available. Preventive measures are aimed at reducing contact with sand flies by using personal protective measures (see Chapter 2, Protection against Mosquitoes, Ticks, and Other Insects and Arthropods). Travelers should be advised to:
- Avoid outdoor activities, especially from dusk to dawn, when sand flies generally are the most active.
- Wear protective clothing and apply insect repellent to exposed skin and under the edges of clothing, such as sleeves and pant legs, according to the manufacturer’s instructions.
- Sleep in air-conditioned or well-screened areas. Spraying the quarters with insecticide might provide some protection. Fans or ventilators might inhibit the movement of sand flies, which are weak fliers.
Sand flies are so small (approximately 2–3 mm, less than one-eighth of an inch) that they can pass through the holes in ordinary bed nets. Although closely woven nets are available, they may be uncomfortable in hot climates. The effectiveness of bed nets can be enhanced by treatment with a pyrethroid-containing insecticide (permethrin or deltamethrin). The same treatment can be applied to window screens, curtains, bed sheets, and clothing.
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