Low incidence of helminth infections (schistosomiasis, strongyloidiasis, filariasis, toxocariasis) among Dutch long-term travelers: A prospective study, 2008-2011

PLoS One. 2018 May 30;13(5):e0197770. doi: 10.1371/journal.pone.0197770. eCollection 2018.

Abstract

Background: Despite the considerable burden of helminth infections in developing countries and increasing international travel, little is known about the risks of infection for travelers.

Objective: We studied the attack and incidence rate of serology confirmed strongyloidiasis, filariasis, and toxocariasis among long-term travelers and associated factors. A second objective was to evaluate eosinophilia as a positive/negative predictive value (PPV/NPV) for a recent helminth infection.

Methods: From 2008 to 2011, clients of the Public Health Service travel clinic planning travel to (sub)tropical countries for 12-52 weeks were invited to participate in a prospective study. Participants kept a weekly diary, recording itinerary, symptoms, and physician visits during travel and completed a post-travel questionnaire. Pre- and post-travel blood samples were serologically tested for the presence of IgG antibodies against Schistosoma species, Strongyloides stercoralis, filarial species, and Toxacara species and were used for a blood cell count. Factors associated with recent infection were analyzed using Poisson regression. Differences among groups of travelers were studied using chi square tests.

Results: For the 604 participants, median age was 25 years (interquartile range [IQR]: 23-29), 36% were male, median travel duration was 20 weeks (IQR: 15-25), and travel purpose was predominantly tourism (62%). Destinations were Asia (45%), Africa (18%), and the Americas (37%). Evidence of previous infection was found in 13/604 participants: antibodies against Schistosoma spp. in 5 (0.8%), against S.stercoralis in 3 (0.5%), against filarial species in 4 (0.7%), and against Toxocara spp. in 1 (0.2%). Ten recent infections were found in 9 participants (3, 1, 6, 0 cases, in the above order), making the attack rates 0.61, 0.17, 1.1 and 0, and the incidence rates per 1000 person-months 1.5, 0.34, 2.6 and 0. The overall PPV and NPV of eosinophila for recent infection were 0 and 98%, respectively.

Conclusions: The risk of the helminth infections under study in this cohort of long-term travelers was low. Routine screening for eosinophilia appeared not to be of diagnostic value.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antibodies, Helminth / metabolism
  • Eosinophilia / diagnosis
  • Female
  • Filariasis / epidemiology*
  • Filariasis / immunology
  • Humans
  • Immunoglobulin G / metabolism
  • Incidence
  • Male
  • Netherlands / epidemiology
  • Poisson Distribution
  • Prospective Studies
  • Schistosomiasis / epidemiology*
  • Schistosomiasis / immunology
  • Strongyloidiasis / epidemiology*
  • Strongyloidiasis / immunology
  • Toxocariasis / epidemiology*
  • Toxocariasis / immunology
  • Travel-Related Illness
  • Young Adult

Substances

  • Antibodies, Helminth
  • Immunoglobulin G

Grants and funding

This study was conducted within the Amsterdam Academic Collaborative Center on Public Health: a collaboration between the Public Health Service of Amsterdam and the Academic Medical Center of the University of Amsterdam, the Netherlands. The Amsterdam Academic Collaborative Center on Public Health is financially supported by the Netherlands Organization for Health Research and Development (ZonMW; grant number 12501 0001). The study was also financially supported by the Department of Research and Development of the Public Health Service Amsterdam. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.