Update from the American Society of Tropical Medicine and Hygiene Meeting in Baltimore

CONFERENCE COVERAGE

Editor’s Note—Approximately 1500 people gathered near the waterfront of Baltimore’s Inner Harbor in early December for the 45th Annual meeting of the American Society of Tropical Medicine and Hygiene. Participants were treated to an attractive menu of plenary sessions, symposia, and scientific sessions. There were many sessions of interest to travel medicine practitioners. Dr. Philip R. Fischer summarizes some of the information relevant to the care of travelers. Readers interested in more information can order a copy of the program and abstracts for $10 from the Society by calling (847) 480-9592. —fjb

Diarrhea

Diarrhea continues to be a major concern for travelers. As scientific understanding of some of the bacterial enteropathogens grows, inroads are being made into both the prevention and treatment of travelers’ diarrhea.

Collaborators from Texas and Switzerland teamed with Jamaican colleagues from 1994 to 1996 to study the etiologies of diarrhea in travelers visiting Jamaica. Fifteen percent of hotel clinic patients presented with diarrhea, usually associated with abdominal pain. Of 350 patients studied, 123 had identifiable pathogens. The vast majority of patients with identified etiologies (and, indeed, 24% of all patients with diarrhea) had enterotoxigenic Escherichia coli (ETEC). ETEC cases were clustered in time and in specific hotels; this suggested that the etiologic agent might have been food-borne. The Jamaican Ministry of Health, based on these findings, instituted training programs for food handlers and increased inspections of kitchens. Since that time, the incidence of diarrhea in travelers has decreased. These investigators modeled a process by which travel health workers can collaborate across international borders to improve the health of tourists. (Abstract #74)

Often, travelers’ diarrhea is the result of locally endemic health conditions. ETEC was studied in Egypt. Near Alexandria, 628 episodes of diarrhea in 260 children were evaluated. One-fifth of the episodes were associated with ETEC. Overall, there was not a seasonal variation in diarrhea cases, but heat-stable-toxin-producing ETEC (ST-ETEC) was more common during warmer months (April-October), and heat-labile-toxin-producing ETEC (LT-ETEC) was more common in cooler months (November-May). (Abstract #75)

Also in Egypt, recurrent diarrhea led to poor growth. A vicious cycle, malnutrition also led to increased diarrhea. (Presentation #76)

Elsewhere in Egypt (where ETEC was also the most commonly identified cause of diarrhea), Shigella was more likely to be seen from April to July than during other times of the year. These Shigella strains were resistant to most commonly used antibiotics but were uniformly susceptible to nalidixic acid. (Abstract #77)

In another area of the world, a six-center collaborative effort in Asia identified ETEC in 13% of 518 patients with travelers’ diarrhea. While the ETEC showed a variety of toxin types, most all organisms had E. coli surface antigens. Vaccines, it is suggested, might be directed at these antigens in an effort to prevent travelers’ diarrhea in Asia. (Abstract #78)

There are, of course, several types of pathogenic E. coli. Increasingly, enteroaggregative (or enteroadherent) E. coli (EAggEC) are found to cause persistent diarrhea in children in developing countries, in individuals with AIDS, and in travelers. In an urban Brazilian shantytown, EAggEC from children was studied. The presence of these organisms was associated with poor growth, cytokine release, and intestinal inflammation. (Abstract #79)

Worms

A scourge is disappearing from our planet—Guinea worm. Guinea worm, or dracunculiasis, is preventable by ensuring that drinking water has at least been filtered. Even such "simple" prevention, however, is often "easier said than done." Reported since at least 1350 BC, Guinea worm has menaced and debilitated people across the globe. Due to extensive efforts by international organizations, governmental groups, private foundations, and local communities, Guinea Worm is facing its final years. Over the last decade, reported cases have decreased by 95%. Southern Sudan, where war limits worm eradication efforts, now accounts for 50% of the world’s cases. (Abstract #67)

Though not previously reported in Africa, human gnathostomiasis has now been linked to travel in southern Tanzania. At least three of five Americans visiting a game park together developed migratory subcutaneous nodules after eating incompletely cooked local fish. Symptoms resolved following treatment with albendazole. (Abstract #69) Travelers should be reminded to fully cook fish and meat before eating it.

It is reported that more than 1 billion inhabitants of our planet are infected with intestinal helminths, and 100 million have filariasis. In Haiti, where 55% of school children have helminths and 13% are microfilaremic, combined, presumptive, single-dose, school-based treatment with albendazole and ivermectin was well-tolerated. Early data analysis suggests that this treatment might lead to improved nutritional status; final sampling and analysis is pending. (Abstract #168)

In Guatemala, intestinal worms are also very common (> 60% of people have hookworms; ascaris and trichuris are also common) with the highest incidences seen in males and in five- to nine-year-olds. The mean, per person worm burden was 36! (Abstract #169) Again, travelers should be reminded about the importance of shoes and good hand-washing in worm-endemic areas.

Hydatid disease is more common in Arab and Druze populations than among Jews in Israel, and the incidence of hydatid disease seems to be increasing over time. Ten percent of dogs and 0.5% of 8000 people tested in one community showed evidence of echinococcal infection. (Abstract #171) In endemic areas, children often develop hydatid cysts in their lungs rather than in their livers. (Abstract #172)

Viruses have prompted news headlines and major movies. Do worms hold the same potential for popularity? Dr. Gary Weil dazzled conference-goers with a video of active subretinal cysts containing larvae of Taenia crassiceps. (Abstract #173)

Dengue

Dengue fever, carried by the mosquito Aedes aegypti, presents with headache, fever, joint pains, and rash. The fatal form, known as dengue hemorrhagic fever, is less common. No specific treatment is available, but good supportive care and avoidance of aspirin can be beneficial. In a special symposium about "Health, Development, and Tourism in the Caribbean," a 1994 dengue outbreak was reviewed. Generally, the biggest problems with dengue in the Caribbean are seen between August and January. Since the vector can breed indoors and bite during the day, attention should be paid to mosquito breeding sites such as indoor plants and water containers in hotels. Even during the large 1994 dengue epidemic in Puerto Rico, careful attention to mosquito control in hotels and at tourist resorts minimized the risk for travelers. Public health officials managed to balance the desire of visitors for healthy vacations and the need of the islands’ economies for tourism. No increase in dengue among travelers was noted. Still, however, travelers to the Caribbean should be diligent with mosquito avoidance.

Education

In an era of medical school curriculum reform, a traditional parasitology course was compared with a newly designed, computer-guided, self-instructional course for medical students. Individuals following the new course performed as well on exams as did students in the traditional lecture course. Internet access to extensive information about parasitology was also provided. (Abstract #600)

The ASTMH certification process is off to a successful start. It was announced at the conference that 120 candidates sat for the certifying exam in clinical tropical medicine and travelers’ health. Another review course is planned for 1997. Seven programs have been accredited (Case Western, Gorgas-University of Alabama Birmingham, Johns Hopkins, Tulane, University of West Virginia, Uniformed Services University, and University of Virginia), and four programs outside the United States are pursuing accreditation (London, Liverpool, Sao Paulo, and Maihidol).

Refugees and Immigrants

Approximately 30,000 foreign refugees enter the United States each year. Two studies dealt with "tropical" problems in refugees and immigrants in the United States.

In Maine, 132 pediatric refugees and immigrants were evaluated in 1994 and 1995; half were from East Africa. Nearly half of the children evaluated had pathogenic intestinal parasites. One-third had positive tuberculosis skin tests, but only 5% had abnormal chest radiographs. One-fifth had evidence of past hepatitis B infection, and 4% were hepatitis B surface antigen positive. Mildly elevated lead levels were found in 17%, anemia in 32%, and dental caries in 17%. (Abstract #72) Screening evaluations and implementation of "well child care" is important for refugees.

Social, nutritional, and epidemiological evaluations were done in a group of Mexican immigrants employed and residing in North Carolina. Health problems were identified (19% with hypertension, 5% with previously undetected hyperglycemia). Health hazards were identified in many homes. "Routine" care was uncommon in this population, where half had never seen a dentist and half of adult women had never had a gynecologic exam. Subjects were often unaware of available health services, and financial and linguistic barriers prevented access to known services. (Abstract #73) Clearly, poor access to care is not limited to the Tropics.

Malaria

A series of 268 cases of malaria seen in Washington, DC, was reported. Most infected individuals (80%) were foreign nationals; almost none had taken prophylaxis during travel. Most patients had returned from West Africa (80%). Travel health advice and malaria prophylaxis should be provided for all American residents traveling to malaria-endemic parts of the world. (Abstract #68)

Realizing that most published literature about severe malaria deals with children in Africa or adults in Thailand, clinicians from a hospital near London’s Heathrow Airport reviewed their experience with 24 patients with severe malaria. They found a variety of clinical presentations including renal failure, adult respiratory distress syndrome, and heart disease. Severe anemia and spontaneous bleeding were not seen. Pre-existing or co-incident health problems can affect the presentation of severe malaria. None of the patients who died had been on prophylaxis. (Abstract #421)

A 74-year-old Greek woman presented in Baltimore with what likely represents the longest course of documented asymptomatic malaria. An older sister later recalled that the patient had had untreated malaria at the age of three years. She never left Greece, which has been free of malaria for at least 40 years, and was well until noting asymptomatic splenomegaly at age 73. Following a course of methotrexate for presumed lymphoma, she developed persistently (15 months) recurrent (quartan) fevers. Malaria smears were repeatedly negative, but P. malariae PCR was postiive on evaluation in the United States. Symptoms resolved with anti-malarial therapy. Dr. Vinetz summarized his presentation saying:

There was an Olympian woman

Whose spleen was the size of a ruin

’Trexate she got

Which made her quite hot

But chloroquine stopped all the stewin’.

(Program and Abstracts of the 45th Annual Meeting of the American Society of Tropical Medicine and Hygiene, Baltimore, Maryland, December 1-5, 1996. Published as a Supplement to the Amercian Journal of Tropical Medicine and Hygiene, Volume 55, August 1996. The executive offices of the ASTMH are located at 60 Revere Drive, Suite 500, Northbrook, IL 60062; phone 847/480-9592; fax 847/480-9282. Copies of abstracts may be obtained.)