Schistosoma – Epidemiology & Diagnosis

Technical Workshop for Basic & Clinical Parasitology ESCMID Postgraduate Technical Workshop

Schistosoma – epidemiology & diagnosis

José Manuel Correia da Costa © by author INSA ESCMIDNational Online Institute of HealthLecture Dr. Ricardo Library Jorge Brindley PJ & Hotez PJ (2013) Break Out: Urogenital Schistosomiasis and Schistosoma haematobium infection in the Post-Genomic Era. PLoS Negl Trop Dis 7(3).

More than 90% of the roughly 200 million cases of schistosomiasis occur in Africa, of which approximately two- thirds are caused by Schistosoma haematobium, the etiologic agent of urogenital schistosomiasis.

Charles King and his collegues have suggested that the number of cases of S. haematobium may be much greater than previously believed, even possibly double or triple that of earlier prevalence estimates. If confirmed, urogenital schistosomiasis may represent the most common infection or even adverse health condition in sub-Saharan Africa.

Female genital schistosomiasis (FGS) is associated with contact bleeding, discharge, pain on intercourse, and secondary infections and diminished fertility; it is also a source of shame and stigma.

FGS is not a rare condition–one estimate suggested that of the estimated 70 million children currently infected with S. haematobium, approximateley 19 million girls and women will eventually develop FGS in the coming decade. FGS may represent one of the most common gynecological conditions in Africa.

S. haematobium eggs have now been© furtherby identified author as a Group 1 carcinogen responsible for a unique squamous cell carcinoma, which is widespread in S. haematobium-endemic areas. S. haematobium also exerts important host endocrine effects … A full consideration of these and other chronic morbidities that use disability-adjusted life years (DALYs) as a metric suggests that chronic urogenital schistosomiasis may equal or even exceed malaria or other better-known conditions in terms of its diseses burden in Africa. ESCMID Online Lecture Library Despite its overwhelming public health importance and its well-established links to HIV/AIDS and cancer, S. haematobium has been labeled “the neglected schistosome”. Technical Workshop for Basic & Clinical Parasitology ESCMID Postgraduate Technical Workshop

Schistosomiasis is an ancient scourge of mankind, depicted graphically in papyri from Pharaonic Egypt, and known from human remains over 2000 years old from China.

Hieroglyfic script. Kahun papyrus

Theodor Bilharz

Schistosomiasis or bilharzia is a common intravascular infection caused by Schistosoma trematode worms;

Human Schistosomiasis is caused by one of 5 species: Schistosoma haematobium; Schistosoma mansoni; Schistosoma japonicum; Schistosoma intercalatum; Schistosoma mekongi.© Schistosoma by malayensisauthor ?

Schistosome transmission requires contamination of water by faeces or urine containing eggs, a specific freshwater snail as intermediate host, and human contact with water inhabited by the intermediate host snail. SchistosomiasisESCMID transmission is highly Onlinedependent on environemental Lecture conditions, particularly Library those affecting the snail host. Climate change will alter aquatic environments and subsequentelly the transmission and distribution of waterborne diseases.

Schistosome infections cause chronic and debilitating diseases also associated with anaemia, chronic pain, diarrhoea, exercise intolerance, undernutrition; female urogenital schistosomiasis may be risk factor for HIV infection. Technical Workshop for Basic & Clinical Parasitology ESCMID Postgraduate Technical Workshop

How is schistosomiasis acquired ?

1- Cercariae, free-swemming larval stages enter in the body after skin penetration;

2- Schistosomulae migrates through the tissues to the liver.

How is schistosomiasis acquired ?

Where is schistosomiasis acquired ?

Infection is usually acquired through activities such as swimming, bathing, fishing, farming and washing clothes.

Global distribution of schistosomiasis. Adapted from Gryseels et al.2006

IntermediateESCMID snail hosts are moreOnline likely to inhabit stillLecture to moderately flowing Library fresh water and infection increases exponentially with length of time in contact with water, peaking at 30 minutes. Technical Workshop for Basic & Clinical Parasitology ESCMID Postgraduate Technical Workshop

© by author Current global distribution of schistosomiasis , stratified according to country-specific prevalence estimates. Source: Steinmann et al., 2006 & Utzinger et al., 2009. ESCMID Online Lecture Library Technical Workshop for Basic & Clinical Parasitology ESCMID Postgraduate Technical Workshop

Technical Workshop for Basic & Clinical Parasitology ESCMID Postgraduate Technical Workshop Calcified egg

haematobium

How is schistosomiasis diagnosed? Calcified egg Microscopic examination of excreta Specific and highly sensitive PCR to detect (stool and urine) remains the gold intercalatum standard test for diagnosis of parasite DNA in faeces or sera and schistosomiasis albeit with some plasma. limitations. The miracidium hatching test. japonicum Formalin based techniques for sedimentation and concentration Biopsy of bladder or rectal mucosa. may increase the diagnostic yield. Imagiology. mekongi Kato-Katz thick smear stool. © by author Antibody detection: useful in a few Schistosoma haematobium eggs are specific circumstances, but its application released in urine and detected by is limited. Epidemiological value. It is microscopyESCMID in a urine sample Online Lectureimportant for Library diagnosis in travellers. concentrated by sedimentation, centrifugation or filtration and Cercarial antigen; SWAP; SEA; circulating forced over a filter. Sample collected adult worm or egg antigens; circulating between 10 am and 2 pm. cathodic antigen. Technical Workshop for Basic & Clinical Parasitology ESCMID Postgraduate Technical Workshop

Key indicators for positive diagnosis of Schistosomiasis

Medical history: Have you travelled to or emigrated from an endemic country recentely? If so from where?

Have you been in contact with a freshwater source (lakes, rivers or streams)?

(Patients returning/emigrating from Africa or the Middle East may have intestinal or urinary schistosomiasis and those from Asia or South America may have intestinal schistosomiasis).

Physical examination: urticarial rash; hepatomegaly; lymphadenopathy…..

Laboratory investigations: Stool/urine examination for schistosome eggs Full blood count: eosinophilia (>80% of patients) with acute infections; anaemia and thrombocytopenia. Coagulation profile: prolonged prothrombin time. Raised urea and creatinine may be evident © by author Serology: may be diagnostic in patients in whom no eggs are present.

Radiology/imagiology

ESCMID Online Lecture Library

Technical Workshop for Basic & Clinical Parasitology ESCMID Postgraduate Technical Workshop

How can be schistosomiasis controlled?

Consensus: Schistosomiasis can be controlled in a coordinated approach with treatment on large scale with safe and effective drugs at regular intervals:

Potable water Adequate sanitation HygieneESCMID education Online Lecture Library Snail control Engels et al., Acta Tropica, 82, 2002 Technical Workshop for Basic & Clinical Parasitology ESCMID Postgraduate Technical Workshop

“Long term commitment” is terminology reserved for marriage, politics, religion and schistosomiasis control.

Kenneth E. Mott, Parasite Diseases Programme, © by authorWorld Health Organization, 1989 ESCMID Online Lecture Library Technical Workshop for Basic & Clinical Parasitology ESCMID Postgraduate Technical Workshop

Additional educational resources:

Parasites – schistosomiasis dpdx (www.cdc.gov) Health topics – schistosomiasis (www.who.int)

www.path.cam.ac.uk/~schisto/schistosoma/index.htlm