SCHISTOSOMIASIS

Definition

            Schistosomiasis also called as Snail fever and or Bilharziasis. The disease was named after Theodor Bilharz, which is considered to be the first person to identify the parasite on 1851 in Egypt. The disease is common in tropical and subtropical country and it has relatively low mortality rate but a high morbidity cases.

Schistosomiasis is often related to the water resource development projects like irrigations or dams, where the snails (main host of the parasite) breed.

            The disease commonly affects farmer in which the nature of their job gives way in contacting directly with the parasite.

            The disease may also affect the following system:

1.      Urinary

2.      Central Nervous System

3.      Gastrointestinal system

Infectious Agents

1.      Schistosoma Japonicum  - a type that is endemic in the Philippines

2.      Schistosoma Mansoni      - it is found in Africa and the only specie found in Latin America. Oncomelania snail is the main host for this type.

3.      Schistosoma Haematobium –Specie that is most common in Africa and in Middle East. This type is contracted through a snail called Bulinus snail.

4.      Schistosoma Intercalatum

5.      Schistosoma Mekongi – This type of specie is found only in Laos and Cambodia.

The Infection Process and its Pathophysiology

ü  Schistosomiasis is contracted through direct contact of an open skin with water contaminated by a parasite.

ü  Upon contact with human, it burrows on skin, and matures into larval stage called (Schistosomula), then migrates into lung and liver where it matures to Adult worm.

ü  The adult worm then travels to different organ like bladder, rectum, intestines, portal venous system and spleen.

“The male and female parasites (s. Japonicum) lived in the blood vessels of the intestines and liver. The eggs of the parasite are laid in the terminal capillary vessels in the submucosa of the intestines and through ulceration reach the lumen of the intestines and pass out with the feces and upon contact with fresh water hatches into a larva (miracidium). The free-swimming larva seeks and penetrates soft part of the intermediate host – a tiny snail called Oncomelania quadrasi, multiples and within two months becomes the infective stage called the cercaria. This fork tailed larva emerges from the snail onto water and enters the skin of man and other warm blooded animals as cows, dogs, carabaos, cats, rats, horses and goats who come contact with infected water through the lymphatic and then the veins, it eventually goes to the heart, systemic circulation, and into the intrahepatic portal circulation where they mature, copulate and start laying eggs in about one month’s time.” (CHN 9^th edition pg.222)

Eggs       miracidia (hatched)       snail        sporocyst and cercaria (inside the snail)       human skin (open skin)       schistosomulae       human veins       lungs and  liver (maturation to become adult worm)       travels to differen organs of the body       Schistosomiasis

Incubation Period - 4-6 weeks

Sign and Symptoms

• Rash (Swimmers Itch) –Pathognomonic sign
• Hematuria
• Diarrhea                                             
• Bloody stools                                       
• Enlargement of abdomen
• Spleenomegaly
• Enlargement of the liver
• Enlargement of the lymph node
• Chills
• Painful urination
• Glomerulonephritis
• Pulmonary hypertension
• Ureteritis
• Cystitis
• Hematemesis
• Eosinophilia
• Abdominal pain
• Cough
• Fever
• Weakness
• Anemia
• Inflamed liver

Diagnostic Exam:

1.      Serology

Ø  Tool used for epidemiological cases.

Ø  It detects antibody that is specific to S. Mansoni, S. Japonicum, and S. Haematobium adult worm microsomal antigen.

a.       Mansoni Adult worm Microsomal Antigen    (MAMS)

b.      Haematobium Adult worm Microsomal Antigen (HAMA)

c.       Japonicum Adult worm Microsomal Antigen (JAMA)

Ø  These three have been reported to be highly specific when used in the Falcon assay screening test (FAST), enzyme linked immune-assays.   (CD 5^th edition Untalan pg.477)

2.      Stool Exam is used to determine the type of eggs in the stool.

3.      Urine exam is used in identifying the severity of the infection.

Ø  Below 100 eggs per gram – light infection

Ø  100-400 eggs per gram is a moderate infection

Ø  Above 400 eggs per gram is a severe infection

4.      Egg Viability Test is done to examine the effectiveness of the treatment

5.      Detecting circulating antigen to assess an active infection.

6.      Intradermal test

7.      Immunodiagnostic test

Assessment

ü  Inspect the frequency of evacuation of stools.

ü  Auscultate hyperactivity of the bowel sounds

ü  Palpate if there is enlargement of the spleen and to assess tenderness in the abdominal area.

ü  Intradermal test

ü  Direct fecal smears

ü  Kato Kats technique

ü  Concentration technique

ü  Circumoval precipitin test

Nursing Diagnosis

ü  Pain

ü  Potential infection

ü  Impaired skin integrity

ü  Altered nutrition

ü  Fluid volume deficit

ü  Knowledge deficit

ü  Self care deficit

ü  Activity intolerance

Method of Control

·         Educate people about the disease and how to prevent it.

·         Proper disposal of the excreta contaminated with parasite.

·         Improve water resources facilities.

·         Treat the snail breeding site.

·         Minimize if not prevented the exposure to contaminated water.

·         Provide water for drinking, boiling of water is recommended.

·         Treat the patient as soon as possible to prevent the progression of the disease.

·         Travelers should be informed if the place is endemic for Schistosomiasis.

·         There’s no need for the patient to be isolated.

·         Quarantine: None

·         Immunization of contacts: None

·         Concurrent disinfection: sanitary disposal of infected urine and stools.

Treatment

1.      Praziquantel (Biltricide) a drug given 30 mg/kg, orally, twice a day for the treatment of infection caused by the parasite Schistosoma. The main action of the drug is to detach the adult worm from the wall of the vein and die.

2.      Nitidazole is given once a day, orally, 25mg/kg/per day to a maximum of  1.5gm for ten days.

3.      Oxamniquine is the best treatment for the infection caused by S. Mansoni.

4.      N-diethyl-m-toluamide is a very potent topical drug for killing cercaria (cercaricidal). The action of this drug is to prevent the entry of the cercaria into the human skin as a result it prevents the person to acquire the disease.

5.      LIPODEET is best preventive measures to people who work on field. It is applied before working in the field because the drug can effectively last up to 60 minutes so that farmers can work safely.

6.      Trivalent Antimony

a.       Tartar emetic administered through vein only

b.      Stibophen (Fuadin) is given through intramuscular. This drug can effectively cure the disease if given in correct dosage and compliance to drug.

    

Prevention

• Avoid washing cloths and bathing in streams
• Proper and sanitary disposal of human feces
• Destruction of snail host –control the multiplication of snails by using snail killing chemicals.
• Improve irrigation and agriculture projects to reduce snail habitat

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Posted in: Communicable Diseases