Travel-related schistosomiasis, strongyloidiasis, filariasis, and toxocariasis: the risk of infection and the diagnostic relevance of blood eosinophilia

Abstract

BackgroundThis study prospectively assessed the occurrence of clinical and subclinical schistosomiasis, strongyloidiasis, filariasis, and toxocariasis, and the screening value of eosinophilia in adult short-term travelers to helminth-endemic countries.MethodsVisitors of a pre-travel health advice centre donated blood samples for serology and blood cell count before and after travel. Samples were tested for eosinophilia, and for antibodies against schistosomiasis, strongyloidiasis, filariasis, and toxocariasis. Previous infection was defined as seropositivity in pre- and post-travel samples. Recent infection was defined as a seroconversion. Symptoms of parasitic disease were recorded in a structured diary.ResultsPrevious infection was found in 112 of 1207 subjects: schistosomiasis in 2.7%, strongyloidiasis in 2.4%, filariasis in 3.4%, and toxocariasis in 1.8%. Recent schistosomiasis was found in 0.51% of susceptible subjects at risk, strongyloidiasis in 0.25%, filariasis in 0.09%, and toxocariasis in 0.08%. The incidence rate per 1000 person-months was 6.4, 3.2, 1.1, and 1.1, respectively. Recent infections were largely contracted in Asia. The positive predictive value of eosinophilia for diagnosis was 15% for previous infection and 0% for recent infection. None of the symptoms studied had any positive predictive value.ConclusionThe chance of infection with schistosomiasis, strongyloidiasis, filariasis, and toxocariasis during one short-term journey to an endemic area is low. However, previous stay leads to a cumulative risk of infection. Testing for eosinophilia appeared to be of no value in routine screening of asymptomatic travelers for the four helminthic infections. Findings need to be replicated in larger prospective studies.

Eosinophilia in Infectious Diseases

“…It causes mild eosinophilia (in 88% of infected patients) [58] that can be associated with diarrhea, abdominal discomfort, or no symptoms at all [59]. …”

Strongyloides stercoralisInfection in Alcoholic Patients

“…Peripheral eosinophilia or elevated total IgE levels greater than 250 IU/mL may be observed in up to 75% of infected hosts [19], serving as a marker for differential diagnoses for travelers to or immigrants from endemic areas with high and persistent levels of eosinophilia [20]. In symptomatic patients with chronic diseases, nonspecific gastrointestinal manifestations, such as abdominal pain, vomiting, diarrhea, and constipation, may also be observed [11].…”

CATMAT statement on disseminated strongyloidiasis: Prevention, assessment and management guidelines

“…4 Defined as cumulative six-month exposure in rural or beach areas, or contact of skin with sand or soil in a risk area even during shorter-term travel (8,9,10). If significant re-exposure accumulates, consider re-screening if initially negative.…”

“…This estimate excludes travel-acquired strongyloidiasis, which is expected to account for a minority of cases in Canada. However, it is important to recognize that even short-term travel to highly endemic areas may be associated with acquisition of strongyloidiasis (8,9,10).…”