Strongyloides stercoralis is a soil-transmitted helminth, but it has a unique life cycle that can be completed in the human host, in a process known as autoinfection. Worldwide, the burden of disease is substantial (300 to 400 million infections). Strongyloidiasis is mainly prevalent in the tropics and subtropics, but there is as yet no global public health strategy for controlling the parasite.

Strongyloidiasis is a soil-borne helminthiasis, which, in spite of the up to 370 million people currently estimated to be infected with its causing agent, the nematode Strongyloides stercoralis, is frequently overlooked. Recent molecular taxonomic studies conducted in Southeast Asia and Australia, showed that dogs can carry the same genotypes of S. stercoralis that also infect humans, in addition to a presumably dog-specific Strongyloides species. This suggests a potential for zoonotic transmission of S. stercoralis from dogs to humans. Although natural S. stercoralis infections have not been reported in any host other than humans, non-human primates and dogs, other as yet unidentified animal reservoirs cannot be excluded. Molecular studies also showed that humans carry rather different genotypes of S. stercoralis. As a result, their taxonomic status and the question of whether they differ in their pathogenic potential remains open. It would therefore be very important to obtain molecular genetic/genomic information about S. stercoralis populations from around the world. One way of achieving this (with little additional sampling effort) would be that people encountering S. stercoralis in the process of their diagnostic work preserve some specimens for molecular analysis. Here we provide a guideline for the isolation, preservation, genotyping at the nuclear 18S rDNA and the mitochondrial cox1 loci, and for whole genome sequencing of single S. stercoralis worms. Since in many cases the full analysis is not possible or desired at the place and time where S. stercoralis are found, we emphasize when and how samples can be preserved, stored and shipped for later analysis. We hope this will benefit and encourage researchers conducting field studies or diagnostics to collect and preserve S. stercoralis for molecular genetic/genomic analyses and either analyze them themselves or make them available to others for further analysis.

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of intestinal parasites in the pre- and post-transplant period. Intestinal parasites are prevalent in the developing regions of the world. With increasing travel to and from endemic regions, changing immigration patterns, and the expansion of transplant medicine in developing countries, they are increasingly recognized as a source of morbidity and mortality in solid-organ transplant recipients. Parasitic infections may be acquired from the donor allograft, from reactivation, or from de novo acquisition post-transplantation. Gastrointestinal multiplex assays have been developed; some of the panels include testing for Cryptosporidium, Cyclospora, Entamoeba histolytica, and Giardia, and the performance is comparable to conventional methods. A polymerase chain reaction test, not yet widely available, has also been developed to detect Strongyloides in stool samples. New recommendations have been developed to minimize the risk of Strongyloides donor-derived events. Deceased donors with epidemiological risk factors should be screened for Strongyloides and recipients treated if positive as soon as the results are available. New therapeutic agents and studies addressing the optimal treatment regimen for solid-organ transplant recipients are unmet needs.

Strongyloidiasis is an intestinal parasitic infection becoming increasingly important outside endemic areas, not only because of the high prevalence found in migrant populations, but also because immunosuppressed patients may suffer a potentially fatal disseminated disease. The aim of these guidelines is to provide evidence-based guidance for screening and treatment of strongyloidiasis in non-endemic areas. A panel of experts focused on three main clinical questions (who should be screened and how, how to treat), and reviewed pertinent literature available in international databases of medical literature and in documents released by relevant organizations/societies. A consensus of the experts\' opinion was sought when specific issues were not covered by evidence. In particular, six systematic reviews were retrieved and constituted the main support for this work. The evidence and consensus gathered led to recommendations addressing various aspects of the main questions. Grading of evidence and strength of recommendation were attributed to assess the quality of supporting evidence. The screening of individuals at risk of the infection should be performed before they develop any clinical complication. Moreover, in immunosuppressed patients, the screening should be mandatory. The screening is based on a simple and widely accessible technology and there is now a universally accepted treatment with a high efficacy rate. Therefore, the screening could be implemented as part of a screening program for migrants although further cost-effectiveness studies are required to better evaluate this strategy from a public health point of view.

The US Centers for Disease Control and Prevention has published refugee health guidelines that recommend examination of the absolute eosinophil count (AEC) to screen for asymptomatic schistosomiasis and strongyloidiasis. We examined the predictive validity of an AEC >400 cells/microL to identify refugees with serologic evidence for schistosomiasis or strongyloidiasis. Our study revealed that eosinophilia was not predictive of serologic evidence of either a Schistosoma species or Strongyloides stercoralis infection in the pediatric refugees examined in this study.

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