Schistosomiasis: Symptoms, Types, Causes and Treatment

Schistosomiasis, also known as bilharzia, is a neglected tropical disease with a profound global impact, affecting over 200 million people, especially in resource-poor communities. Caused by parasitic flatworms of the genus Schistosoma, the disease is contracted through contact with contaminated freshwater and can lead to chronic health problems if left untreated. In this article, we’ll explore the symptoms, types, causes, and treatments of schistosomiasis, drawing from the latest scientific research to provide a comprehensive, human-centered overview.

Symptoms of Schistosomiasis

Schistosomiasis presents with a wide spectrum of symptoms that can range from mild or even unnoticed to severe, depending on the stage of infection, the species involved, and individual host factors. The disease evolves through acute and chronic phases, each with distinct clinical features that may significantly affect quality of life.

Stage	Main Symptoms	Affected Organs	Source
Acute	Fever, cough, rash, fatigue	Systemic	1 2 4
Subacute	Abdominal pain, diarrhea, hematuria	Intestine, bladder	1 3 5
Chronic	Liver fibrosis, anemia, growth delay	Liver, spleen, bladder	1 3 5 7 10

Table 1: Key Symptoms

Acute Symptoms

Acute schistosomiasis, also known as Katayama fever, typically occurs in individuals with no prior exposure, such as travelers. It can develop 2–8 weeks after infection and features:

• Fever
• Cough
• Fatigue
• Urticarial rash
• Enlarged liver and spleen (hepatosplenomegaly)
• Bronchospasm
  This stage is essentially a hypersensitivity reaction to migrating schistosomula and newly laid eggs 1 2 4.

Subacute Symptoms

As the parasite matures and settles in target organs, symptoms shift depending on the species:

• Abdominal pain
• Bloody diarrhea (intestinal types)
• Hematuria (blood in urine, especially with S. haematobium)
• Anal pain and tenesmus (urge to defecate) These symptoms result from granulomatous inflammation around eggs in the gut or urinary tract 1 3 5.

Chronic and Long-term Effects

Chronic schistosomiasis arises from years of repeated or unresolved infections, leading to:

• Fibrosis and calcification of affected organs
• Portal hypertension, splenomegaly, and esophageal varices (dangerous bleeding)
• Chronic anemia, stunted growth, and cognitive impairment
• Bladder cancer (S. haematobium)
• Female genital schistosomiasis (infertility, menstrual disorders, increased HIV risk)
• Liver and kidney damage The chronic phase is the primary driver of schistosomiasis morbidity and long-term disability 1 3 5 7 10.

Types of Schistosomiasis

Different Schistosoma species infect humans, leading to varied disease manifestations. Understanding these types is critical for diagnosis, treatment, and public health interventions.

Type	Main Species	Primary Organs Affected	Source
Urogenital	S. haematobium	Bladder, genital tract	7 8 12
Intestinal	S. mansoni, S. japonicum, S. mekongi, S. intercalatum	Intestines, liver	3 6 7 8 12
Asian	S. japonicum, S. mekongi, S. malayensis	Intestines, liver	6

Table 2: Main Types of Schistosomiasis

Urogenital Schistosomiasis

Primarily caused by Schistosoma haematobium, this form affects the urinary and genital tracts. Key features include:

• Hematuria (blood in urine)
• Bladder wall pathology
• Risk of bladder cancer
• Female genital schistosomiasis (infertility, menstrual and sexual health issues)
• Male genital involvement (prostatitis, infertility)
  Chronic infection can result in strictures, fibrosis, and increased cancer risk 5 7 8.

Intestinal Schistosomiasis

This encompasses infections with S. mansoni, S. japonicum, S. mekongi, and S. intercalatum. These species:

• Reside in mesenteric veins
• Cause abdominal pain, diarrhea, and blood in stool
• Lead to chronic colitis, polyps, and eventually hepatosplenic disease, including portal hypertension, splenomegaly, and esophageal varices 3 7 8 12.

Asian Schistosomiasis

Schistosoma japonicum, S. mekongi, and S. malayensis are prevalent in parts of Asia. Notably, S. japonicum is zoonotic, meaning it infects both humans and animals—making control efforts more complex. Disease manifestations are similar to intestinal schistosomiasis but may be more severe due to higher egg output 6.

Causes of Schistosomiasis

Schistosomiasis is fundamentally an environmental disease, resulting from a complex interaction between human behavior, parasite biology, and ecology.

Cause	Description	Key Factor	Source
Parasite	Schistosoma species (six main types)	Infectivity	8 9 12
Water Exposure	Contact with contaminated freshwater	Human behavior	2 8 9 11
Snail Hosts	Essential for parasite lifecycle	Ecology	9 11 12
Poor Sanitation	Fecal/urinary contamination of water sources	Infrastructure	8 9 11

Table 3: Main Causes and Transmission Factors

Parasite Lifecycle and Transmission

The disease is caused by six main Schistosoma species, with S. haematobium, S. mansoni, and S. japonicum most commonly responsible for human disease. The lifecycle involves:

• Human excretes eggs in urine or feces into water
• Eggs hatch into miracidia, which infect specific freshwater snails
• Inside snails, they multiply and release cercariae (infective larvae)
• Cercariae penetrate human skin during water contact (swimming, bathing, fishing)
• In humans, larvae migrate to blood vessels, mature, and lay eggs—continuing the cycle 8 9 12

Environmental and Behavioral Factors

Transmission is concentrated in areas with:

• Freshwater bodies contaminated by human waste
• Presence of compatible snail hosts
• Poor access to safe water and adequate sanitation
• High-risk activities (e.g., swimming, fishing, irrigation) A single water exposure can result in high infection rates, as seen in traveler outbreaks 2 8 9 11.

Socioeconomic and Gender-Related Issues

• Children and women are especially vulnerable due to water usage patterns
• In endemic areas, women may suffer disproportionately due to genital schistosomiasis and its reproductive health consequences 5

Treatment of Schistosomiasis

Effective treatment is essential to control morbidity and interrupt transmission. Most cases are treatable with safe, affordable medications, but prevention and control require integrated strategies.

Treatment	Drug(s)	Effectiveness	Source
Antiparasitic	Praziquantel	~80% cure	1 13 15 16
Other options	Metrifonate, Oxamniquine, Artemether	Species-specific	1 13 16
Prevention	Mass drug administration, WASH, snail control	Reduces morbidity, transmission	8 11 14 15

Table 4: Current Treatments and Strategies

Praziquantel: The Gold Standard

• Praziquantel is the treatment of choice for all human schistosome infections.
  • Single or divided doses are highly effective (~80% cure rate).
  • Well-tolerated with mild, transient side effects.
  • Safe for use in pregnancy and children over 2 years old 1 13 15 16.

Other Antischistosomal Drugs

• Metrifonate: Effective against S. haematobium.
• Oxamniquine: Used for S. mansoni (not effective against all species).
• Artemether: Investigated for both prevention and treatment, but not widely used 1 16.

Mass Drug Administration (MDA) and Preventive Chemotherapy

• MDA programs target high-risk groups, especially school-aged children, to reduce community transmission and morbidity.
• WHO now recommends expanded treatment to all at-risk groups (age 2+), with lower thresholds for annual treatment.
• MDA has led to significant reductions in disease burden when implemented consistently 14 15.

Prevention and Control Strategies

• Water, Sanitation, and Hygiene (WASH): Improving access to safe water and sanitation reduces transmission risk.
• Snail control: Environmental management and molluscicides can reduce intermediate host populations.
• Health education: Encourages behavioral change to avoid contact with contaminated water 8 11 14.
• Vaccine development: Ongoing, but not yet available 1 3.

Challenges and Future Directions

• Drug resistance is a growing concern due to reliance on praziquantel.
• Reinfection is common if exposure persists.
• Integrated approaches combining treatment, WASH, snail control, and education are essential for sustained control and eventual elimination 9 11 14 15.

Conclusion

Schistosomiasis remains a major public health challenge in many parts of the world. Understanding its symptoms, types, causes, and treatments is crucial to reducing its burden and moving toward elimination. Here’s a summary of the key points covered:

• Symptoms vary by stage and species, ranging from fever and rash to chronic organ damage and cancer risks.
• Different types are caused by distinct Schistosoma species, affecting either the urinary or intestinal systems.
• Caused by contact with freshwater contaminated by schistosome larvae, requiring both human and snail hosts for transmission.
• Praziquantel remains the cornerstone of treatment, but prevention and control require mass drug administration, improved sanitation, snail control, and education.
• Integrated, multi-pronged public health approaches are essential to interrupt transmission and eventually eliminate the disease.

By staying informed and supporting comprehensive control strategies, we can help combat this neglected but preventable disease.