Schistosomiasis

Schistosomiasis (Snail Fever/bilharzia)

Schistosomiasis, also known as snail fever, is a parasitic disease caused by flatworms of the genus Schistosoma.

Schistosomiasis (also known as bilharzia or snail fever) is a disease of the large intestine and urinary tract caused by parasitic worms of the Schistosoma blood fluke.

It may infect the urinary tract or intestines.

Causes/Aetiology:

Schistosoma species: The disease is caused by five main species of Schistosoma:

• S. haematobium: Causes urinary schistosomiasis.
• S. mansoni: Causes intestinal schistosomiasis.
• S. japonicum: Causes intestinal schistosomiasis.
• S. intercalatum: Causes intestinal schistosomiasis.
• S. mekongi: Causes intestinal schistosomiasis.

Snail intermediate host: Snails of specific species are essential for the parasite\’s lifecycle.

Transmission:

• Vector: The disease is transmitted through contact with contaminated freshwater, primarily by snails infected with Schistosoma parasites.

Schistosomiasis  Lifecycle:

In the Snail (Intermediate Host):

1. Schistosoma eggs released from an infected human enter freshwater, where they hatch into larvae called miracidia.
2. Miracidia infect snails.
3. Within the snail, the miracidia transform into cercariae, which are free-swimming larval forms.

In Humans (Definitive Host):

1. Cercariae penetrate the skin of humans who come into contact with contaminated water.
2. Cercariae mature into adult worms within the human body.
3. Adult worms reside in the blood vessels of the intestines, bladder, or other organs.
4. Female worms release eggs into the body, and these eggs are excreted in feces or urine.
5. The cycle repeats as eggs enter freshwater and infect snails.

The lifecycle of Schistosoma worms starts with infected humans. The worms live in the blood vessels of the intestines and produce eggs that are released in feces. These eggs enter freshwater and hatch into microscopic larvae called miracidia.

Miracidia swim until they find a specific type of snail. Inside the snail, they multiply and transform into another type of larvae called cercariae. Cercariae leave the snail and swim in the water.

If a person enters this contaminated water, the cercariae can penetrate their skin. Once inside, they mature into adult worms. The cycle starts again when the worms reproduce and release eggs, which are then expelled in feces and enter the water.

Clinical Features:

1. Acute Schistosomiasis (Katayama Fever):

• Fever
• Chills
• Headache
• Muscle aches
• Rash
• Cough
• Abdominal pain
• Diarrhea
• Enlarged liver and spleen

2. Chronic Schistosomiasis:

Urinary Schistosomiasis:

• Blood in the urine (hematuria).
• Frequent urination, especially at night (nocturia).
• Painful urination (dysuria).
• Bladder inflammation (cystitis).
• In advanced cases, bladder fibrosis and cancer.

Intestinal Schistosomiasis:

• Abdominal pain and cramping.
• Diarrhea or constipation.
• Blood in the stool (hematochezia).
• Liver enlargement (hepatomegaly).
• Splenomegaly (enlarged spleen).
• In advanced cases, portal hypertension, ascites, and esophageal varices.

3. Other Manifestations:

• Lung involvement (pulmonary schistosomiasis) with cough and shortness of breath.
• Skin lesions (schistosomal dermatitis) with itching and papules.
• Brain involvement (neurological schistosomiasis) with seizures, paralysis, and cognitive impairment.

Diagnosis and Investigations:

• Stool and Urine Examination: Microscopic examination for eggs in stool or urine samples.
• Serological Tests: Blood tests to detect antibodies against Schistosoma.
• Imaging Studies:

  • Ultrasound: To visualize the liver, spleen, and other organs.

  • CT scan: To evaluate the bladder and kidneys.

  • MRI: To assess the brain and spinal cord.

• Biopsy: Biopsy of affected organs (liver, bladder) to confirm the presence of eggs or adult worms.

Prevention:

Safe Water and Sanitation:

• Provide access to safe drinking water and adequate sanitation facilities.
• Promote proper waste disposal to prevent contamination of freshwater sources.

Health Education:

• Educate communities about the disease, transmission, and prevention.
• Encourage safe bathing and swimming practices in freshwater bodies.

Snail Control:

• Reduce snail populations by using molluscicides (chemicals that kill snails).
• Implement environmental interventions to modify snail habitats.

Mass Drug Administration (MDA):

• Regularly administer praziquantel to all individuals in endemic areas to control the disease.

Management:

Aims of Management:

• To kill adult worms and prevent egg production.
• To treat existing symptoms and complications.
• To prevent further transmission of the disease.

Medical Management:

• Praziquantel: The primary drug for schistosomiasis, effective in killing both adult worms and reducing egg production.
• Praziquantel 40 mg/kg single dose
• Refer patient if they develop obstruction or bleeding.
• Other Medications:

1. Antibiotics: For treating secondary bacterial infections.
2. Pain relievers: For managing pain and discomfort.
3. Anti-inflammatory medications: For reducing inflammation.

• Symptomatic Treatment: Address specific symptoms such as fever, diarrhea, and urinary problems.

Nursing Care:

• Symptom Management: Provide comfort measures for fever, pain, and diarrhea.
• Hydration: Encourage fluid intake to prevent dehydration.
• Hygiene: Promote proper hygiene to prevent infection.
• Education: Educate patients about the disease, treatment, and prevention.
• Monitoring: Monitor for signs of complications, including liver problems, bladder dysfunction, and neurological symptoms.