Tag Archive for travellers

Chapter 4 – Molecular Diagnostics of Intestinal Parasites in Returning Travellers.


A new diagnostic strategy was assessed for the routine diagnosis of intestinal parasites in returning travellers and immigrants. Over a period 13 months, unpreserved stool samples, patient characteristics and clinical data were collected from those attending a travel clinic. Stool samples were analyzed on daily basis by microscopic examination and antigen detection (i.e. care as usual), and compared with a weekly performed multiplex real-time PCR analysis on Entamoeba histolytica, Giardia lamblia, Cryptosporidium and Strongyloides stercoralis. Microscopy and antigen assays of 2591 stool samples showed E. histolytica, G. lamblia, Cryptosporidium and S. stercoralis in 0.3%, 4.7%, 0.5%, and 0.1% of the cases, respectively. These detection rates were increased using real-time PCR to 0.5%, 6.0%, 1.3% and 0.8%, respectively. Prevalence of 10 additional pathogenic parasite species identified with microscopy was 0.5% at most. A pre-selective decision tree based on travel history or gastro-intestinal complaints could not be made. With increased detection rates at a lower workload, and the potential to extend with additional parasite targets combined with fully automated DNA isolation, the molecular high throughput screening could eventually replace microscopy to a large extend.

Robert ten Hove, Marjan van Esbroeck, Tony Vervoort, Jef van den Ende, Lisette van Lieshout, Jaco J. Verweij. European Journal of Clinical Microbiology and Infectious Diseases, 2009.

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Predictors of parasitic and bacterial causes of diarrhoea in travellers.

Trans R Soc Trop Med Hyg. 2012 Sep;106(9):549-53. doi: 10.1016/j.trstmh.2012.04.008. Epub 2012 Jul 20.
Geographic, symptomatic and laboratory predictors of parasitic and bacterial causes of diarrhoea in travellers.
McGregor AC, Whitty CJ, Wright SG.

Hospital for Tropical Diseases, Capper Street, London WC1E 6AU, UK. alastairmcgregor@yahoo.co.uk

An observational study of patients presenting with diarrhoea to a walk-in service for returning travellers was conducted with the aim of identifying features that would help predict whether pathogens were bacterial or parasitic. In total, 509 cases were included, of which a bacterial aetiology was found in 55/440 (12.5%) and a parasitic cause in 51/428 (11.9%). Patients with symptoms of ≤14 days were significantly more likely to have a bacterial diagnosis than those with longer symptoms (p<0.001), whereas parasitic causes of diarrhoea were not associated with length of symptoms and became proportionately more likely with time. Raised CRP, faecal white cells and fever were all predictive of positive bacterial culture (p<0.001, p=0.001 and p=0.001, respectively) but did not predict parasitic infection. Travellers to South and Southeast Asia were more likely to have parasites detected in their stool than travellers to other tropical areas (OR=1.96; p=0.041). Gender, ethnicity, reason for travel and length of stay abroad were not significantly associated with the faecal pathogen identified.

Note from Robert ten Hove

The study on bacterial and parasitic infections among returning travelers was well performed. Interesting to see such a difference in travelers destinations. The majority of patients at the British clinic returned from India / South-East Asia whereas in The Netherlands and Belgium the majority of travelers return from the African continent. Nonetheless, nothing remarkable about percentages. It was good to read that Dientamoeba fragilis is not considered as a pathogen.

The most important message of this article is the one that is not mentioned. The writers do suggest that the absence of a good gold standard makes estimating the sensitivity of a stool microscopy difficult… In several countries (at least in The Netherlands and Belgium), Molecular diagnostics is now considered to be the gold standard, both for the detection of parasites as for several bacteria species. Why still dabbling through the poo with culture, ELISAs, Ridley’s, Ziehl-Neelson staining, fluorescend microscopy, and so on? When you got molecular diagnostics!