Research Article: Filariasis in Travelers Presenting to the GeoSentinel Surveillance Network

Date Published: December 26, 2007

Publisher: Public Library of Science

Author(s): Ettie M. Lipner, Melissa A. Law, Elizabeth Barnett, Jay S. Keystone, Frank von Sonnenburg, Louis Loutan, D. Rebecca Prevots, Amy D. Klion, Thomas B. Nutman, Maria Yazdanbakhsh

Abstract: BackgroundAs international travel increases, there is rising exposure to many pathogens not traditionally encountered in the resource-rich countries of the world. Filarial infections, a great problem throughout the tropics and subtropics, are relatively rare among travelers even to filaria-endemic regions of the world. The GeoSentinel Surveillance Network, a global network of medicine/travel clinics, was established in 1995 to detect morbidity trends among travelers.Principal FindingsWe examined data from the GeoSentinel database to determine demographic and travel characteristics associated with filaria acquisition and to understand the differences in clinical presentation between nonendemic visitors and those born in filaria-endemic regions of the world. Filarial infections comprised 0.62% (n = 271) of all medical conditions reported to the GeoSentinel Network from travelers; 37% of patients were diagnosed with Onchocerca volvulus, 25% were infected with Loa loa, and another 25% were diagnosed with Wuchereria bancrofti. Most infections were reported from immigrants and from those immigrants returning to their county of origin (those visiting friends and relatives); the majority of filarial infections were acquired in sub-Saharan Africa. Among the patients who were natives of filaria-nonendemic regions, 70.6% acquired their filarial infection with exposure greater than 1 month. Moreover, nonendemic visitors to filaria-endemic regions were more likely to present to GeoSentinel sites with clinically symptomatic conditions compared with those who had lifelong exposure.SignificanceCodifying the filarial infections presenting to the GeoSentinel Surveillance Network has provided insights into the clinical differences seen among filaria-infected expatriates and those from endemic regions and demonstrated that O. volvulus infection can be acquired with short-term travel.

Partial Text: Parasitic diseases are widespread throughout the developing world and are associated with a heavy burden of morbidity and mortality. Human filariae, nematodes transmitted by arthropod vectors, are endemic in tropical and subtropical regions of the world. With an estimated 80 million people who travel to developing countries each year [1], exposure to filarial parasites is likely to become more common. It has been suggested that infection with filariae requires prolonged and intense exposure to the vectors that transmit them [2]. Moreover, when comparing nonendemic visitors who have acquired filarial infections with those born in endemic regions, the nonendemic visitors appear to have greater numbers of objective clinical symptoms and fewer clinically asymptomatic (or subclinical) infections [3]–[7].

From a total of 43,722 individual patient encounters, filarial infections were diagnosed for 271 (0.62%) persons who presented to GeoSentinel sites from August 1997 through July 2004. The reporting of cases to GeoSentinel was lowest in 1997 and 1998 (3.7% and 8.9% respectively); from 1999 through 2004, filariasis as a proportion of morbidity (ill patients reporting to the clinics) fluctuated between 11% (n = 30) and 17.5% (n = 47). Of the 271 patients with filarial infections, 37% were diagnosed with O. volvulus, 25% were infected with L. loa, and another 25% were diagnosed with W. bancrofti. Among all filarial infections, 5.5% were identified as other filarial species, (e.g., Mansonella, Brugia spp.), and 5.5% of all filarial infections reported in the database were unspecified. Three patients were coinfected with L. loa and other filarial species; one patient presented with O. volvulus and L. loa coinfection (Figure 1). Overall, 122 (45%) patients were female; gender was not recorded for 17 (6.3%) patients. Patient mean age was 34.9 years (range 0–84). The region of acquisition among filaria-infected individuals was assigned when possible (n = 230). The majority (75%) of infections were acquired in Africa (both Northern Africa and Sub-Saharan Africa) and 10% in South America (see Table 1). The remaining individuals were exposed in, Oceania, the Caribbean, South Central Asia, and Central America. Of all filarial infections reported to the GeoSentinel ntwork (n = 271), the majority were reported by the North American sites (76.4%); 18.5% were reported from European sites, and the remainder were reported from GeoSentinel sites in the Middle East, Australia/New Zealand, and South Central Asia.

While filarial infection and disease are most frequently diagnosed among native residents of endemic regions, the risk of infection acquisition among travelers from nonendemic regions is sizeable. Filarial species are found in tropical and sub-tropical regions of the world and, as travel to these regions becomes more popular, filarial infection among nonendemic visitors becomes increasingly common as well. We describe here important epidemiologic characteristics of filarial infections acquired by world travelers from nonendemic regions as reported to the GeoSentinel network. While clinical presentation of filarial disease is known to differ between visitors to and natives of endemic regions [3], our analysis also provides a quantitative assessment of filarial acquisition among travelers and helps describe the differences in clinical presentation between those native to filaria-endemic regions and those traveling to those regions.

In addition to the authors, members contributing data include:



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