Dear Colleagues,

It is a pleasure to invite you to participate in this Special Issue, which aims to evaluate the prevalence of strongyloidiasis and schistosomiasis.

Both of these helminth infections are of particular importance. First, besides being as highly prevalent as other parasitic infections, they can cause long-term complications and severe consequences. Schistosomiasis is associated with chronic urogenital, hepato-intestinal, and central nervous system complications. St. stercoralis can manifest as a severe condition (disseminated infection or hyper infection) with fatal outcomes in immunosuppressed patients (e.g., transplant recipients, those on corticosteroid therapy, those with malignancies, or co-infections with human T-cell lymphotropic virus-1). Second, most infections are asymptomatic, and those that are infected are either unaware of their infection or have very mild unspecific symptoms. Third, both become chronic infections if untreated [1]. Schistosomiasis can remain as a sub-clinical infection for many years, and St. stercoralis replicates indefinitely inside the human host, causing lifelong infection if untreated [2].

Strongyloidiasis has worldwide distribution, although it is more prevalence in tropical and subtropical areas [3]. The current estimate of 30 to 100 million infected persons in the world dates back to review articles published between 1989 and 1996. However, global prevalence estimates should probably be revised, based on studies using diagnostic techniques that are better suited to S. stercoralis. In addition, few studies have been conducted to assess strongyloidiasis’ prevalence in non-endemic countries. On the other hand, schistosomiasis affects almost 240 million people worldwide, and more than 700 million people live in endemic areas [4]. The infection is prevalent in tropical and sub-tropical areas. The risk of schistosomiasis is more geographically specific, with adult migrants from sub-Saharan Africa at highest risk. In these settings, the proliferation of mass drug administration (MDA) programmes using the drug praziquantel results in substantial increases in the number of people receiving one or more treatments during their lifetimes [5]. This could decrease the burden of disease, as has been shown in some settings such as Zanzibar [6]. The Expert Committee on Prevention and Control of schistosomiasis and soil-transmitted helminthiasis has recently reviewed data on morbidity and mortality due to schistosomiasis in sub-Saharan Africa and endorsed new estimates.

Topics may include but are not limited to prevalence studies on strongyloidiasis and schistosomiasis, including studies on both endemic and non-endemic countries and also on high risk populations (e.g., immunosuppressed patients). 

Dr. Ana Requena Mendez
Guest Editor

References:

1. Agbata, E.; Morton, R.L.; Bisoffi, Z.; Bottieau, E.; Greenaway, C.; Biggs, B.A.; Montero, N.; Tran, A.; Rowbotham, N.; Arevalo-Rodriguez, I.; et al. Effectiveness of screening and treatment approaches for schistosomiasis and strongyloidiasis in Newly-Arrived Migrants from Endemic Countries in the EU/EEA: A Systematic Review. Int. J. Environ. Res. Public Health 2018, 16, 11.
2. Requena-Mendez, A; Buonfrate, D.; Gomez-Junyent, J.; Zammarchi, L.; Bisoffi, Z.; Munoz, J. Evidence-Based Guidelines for Screening and Management of Strongyloidiasis in Non-Endemic Countries. J. Trop. Med. Hyg. 2017, 97, 645–652.
3. Asundi, A.; Beliavsky, A.; Liu, X.J.; Akaberi, A.; Schwarzer, G.; Bisoffi, Z.; Requena-Mendez, A.; Shrier, L.; Greenaway, C. Prevalence of strongyloidiasis and schistosomiasis among migrants: a systematic review and meta-analysis. Lancet Glob Health 2019; 7, e236–e248.
4. Bisoffi, Z.; Buonfrate, D.; Montresor, A.; Requena-Mendez, A.; Munoz, J.; Krolewiecki, A.J.; Gotuzzo, E.; Mena, M.A.; Chiodini, P.L.; Anselmi, M.; et al. Strongyloides stercoralis: a plea for action. PLoS Negl. Trop. Dis. 2013, 7, e2214.
5. Mutapi, F.; Maizels, R.; Fenwick, A.; Woolhouse, M. Human schistosomiasis in the post mass drug administration era. Lancet Infect Dis. 2017,17, e42–e48.
6. Knopp, S.; Person, B.; Ame, S.M.; Mohammed, K.A.; Ali, S.M.; Khamis, I.S.; Rabone, M.; Allan, F.; Gouvras, A.; Blair, L.; et al. Elimination of schistosomiasis transmission in Zanzibar: baseline findings before the onset of a randomized intervention trial. PLoS Negl. Trop. Dis. 2013, 7, e2474.

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• Strongyloides
• Schistosoma
• Prevalence
• Helminth infections
• St. stercoralis