Schistosomiasis or bilharzia is an acute and chronic tropical parasitic disease caused by blood-dwelling fluke worms of the genus Schistosoma. Schistosomiasis is endemic in 77 countries with an estimated total of 230 million people are infected worldwide, and 732 million people are at risk of being infected/ persons being vulnerable to infection worldwide(1, 2) Schistosomiasis is neglected tropical disease of poverty ranks second among the most widespread parasitic disease in various nations in sub-Saharan Africa (3).
Three main species of schistosomes infect human beings, S. haematobium, S. mansoni and S. japonicum. S. mansoni, which causes intestinal and hepatic schistosomiasis in Africa, the Middle East, and South America; S. haematobium, causing urinary schistosomiasis in Africa and the Arabian peninsula; and S japonicum, causes intestinal and hepatosplenic schistosomiasis which localizes to Asia, primarily in China, Philippines, and Indonesia (2). S. mansoni and S. haematobium need certain species of aquatic freshwater Biomphalaria and Bulinus snails, respectively. S japonicum uses amphibious freshwater Oncomelania spp snails as its intermediate host (1).
The life cycle of schistosoma parasites is completed in two different hosts i.e. humans and freshwater snails. Human get infected when they come in contact with fresh water contaminated by cercariae, the infective stage of the parasite. Cercaria penetrate the skin, and transform into schistosomula. Then develop to male-female worm pairs, and inhabit either the portal or pelvic vessels. The female begins to lay eggs within the mesenteric or pelvic vessels. Most of the eggs are carried upstream to the liver via the portal veins and its branches and get trapped in the pre-sinusoidal portal venules. Some of the eggs migrate and penetrate the intestines and shed in the stool. When eggs contact water, they hatch into ciliated larval forms called miracidia that can sense compatible intermediate snail hosts. Miracidia penetrate the snail by proteolytic activity and mechanical movement. Inside the snail host, miracidia undergo asexual development and transform into cercariae which emerge from the snails and find out the definitive host. Snail populations, cercarial density, and patterns of human water contact are the main factors for the transmission (1, 4).
Based on pathogenesis we can classify acute and chronic form of Schistosomiasis. Acute schistosomiasis occurs weeks to months after infection, as a consequence of worm maturation, egg production and release of egg antigen. Sometimes referred to as Katayama syndrome and the typical clinical presentation are a sudden onset of fever, myalgia, headache, eosinophilia, fatigue, malaise, and abdominal pain (5). In chronic schistosomiasis, eggs are the cause of pathology; many eggs are not excreted and become permanently lodged in the intestines or liver (for S. mansoni, S. japonicum, andor in the bladder and urogenital system (for S. haematobium). They induce granulomatous host immune response largely characterized by lymphocytes which mainly produce a T helper type 2 (Th2) cytokines. The process of granuloma formation elicit chronic inflammation that leads to tissue fibrosis and chronic morbidity of schistosomiasis(6).
The microscopic examination of excreta for detection of parasite eggs remain the gold standard for diagnosis of schistosomiasis. For people from non-endemic areas or living in low transmission areas, serological and immunological tests may be useful in showing exposure to infection and the need for thorough examination and treatment. For rapid diagnosis of schistosomiasis, stool samples are examined for the presence of parasite eggs using a Kato-Katz thick smear or rapid Kato techniques(7). Praziquantel was proven to be e?ective against the all species of schistosomes a?ecting humans and now most widely used. The drug acts within one hour of ingestion by paralyzing the worms and damaging the tegument but it has little or no effect on eggs and immature worms(8, 9)
Understanding the schistosome life cycle and the parasite’s movement between
intermediate and definitive (mammalian) hosts is fundamental to the control and elimination of human Schistosomiasis. WHO recommend that population-based treatment with praziquantel is now the main component of most national control programmes. Health education, improved sanitation standards, prevention of sewage contamination of freshwater and environmental measures like snail control and changes in snail habitat are the main ways for control and prevention of infection (8, 10)
Adult schistosomes reside in their host’s bloodstream for three to five years, sometimes decades, should lead to disturbances of blood flow. As intravascular parasites, schistosomes interact with all components of host blood, including platelets and Platelets are small, no cell nucleus and fragments of cytoplasm that are derived from the megakaryocytes of the bone marrow. Platelets play a most important role in hemostasis in addition to helping to fight infection(11, 12). Parasite-induced alteration in blood flow and endothelial damage plays a role in activation of blood coagulation. Due to electronegative charges on surfaces of schistosomes there is potentially activation of platelets and coagulation cascade (13).
Statement of problem
Schistosomiasis is endemic in 77 countries where 732 million people are at risk of being infected and 230 million people are infected worldwide (1) and disease burden assessments estimate that schistosmiasis accounts for up to 70 million disability-adjusted life years (DALYs) lost annually (14). Schistosomiasis is the most destructive tropical disease globally and is a major cause of morbidity and mortality for developing countries in Africa, South America, the Caribbean, the Middle East, and Asia. The distribution of the diseases is focal and often restricted to areas with particular ecology which favours its transmission (15).
In Africa an estimated 660 million people were at risk of schistosomiasis, which accounts 85% of globally at risk people and 201.5 million infected individuals were estimated to occur in Africa, accounting for more than 97% of the estimated number of infections worldwide (16). Almost 300,000 people die annually from schistosomiasis in Africa alone (4).
Most of the countries endemic for schistosomiasis are among the least developed, whose health
systems face severe strains to provide basic care at the primary level. They cannot perform proper control program (17). Based on the size of the endemic areas and the estimated prevalence, the most severely affected countries are found in Africa, South America and South-East Asia. Twenty nine African countries, Brazil and Yemen are most suffering countries which harbour / contains more than one million cases each country (18).
Humans are usually infected by five species of schistosomes, namely Schistosoma mansoni, Schistosoma haematobium, Schisosoma japonicum, Schistosoma mekongi, and Schistosoma intercalatum (19). Schistosoma mansoni is the most prevalent being endemic in 55 countries and which is the source of hepatic and intestinal (20).
S. mansoni infection association with consistent hematologic changes. The acute phase is characterized by fever, myalgia, progressive hepatomegaly and splenomegaly. At this time, the most common finding in peripheral blood is eosinophilia. As the disease progresses, there may be massive hepatosplenomegaly associated with anemia, thrombocytopenia and coagulation disorder (21).
Schistosomiasis appears as a result of the host’s strong granulomatous response to schistosome eggs that lodge in blood vessel endothelia, particularly in the portal vasculature which lead to portal hypertension. In patients with portal hypertension, platelet count decreased, immature platelets are significantly increased, bleeding complications and hemostatic disturbances developed. The disease progresses is associated with increased hemostatic complication (22, 23).
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Literature Review
A cross sectional study was carried out in 2010 to 2012 among patients with Hepatosplenic Schistosomiasis Mansoni in Brazil which contain 55 patients and 29 controls. The aim of the study is to evaluate whether abnormal blood coagulation and liver function tests in patient with Hepatosplenic Schistosomiasis. The result showed significant increases in the INR, PTT and TT values compared to the healthy controls, while the coagulation factors there was a 40% increase in INR (p
