SCHISTOSOMIASIS ICD-10 B65 (Bilharziasis, Snail fever) Dr. Nadia Aziz C.A.B.C.M. Department of community medicine Baghdad medical college

Objectives 1- Define Schistosomiasis, its clinical features & its occurrence 2-Identify the infectious agents & its life style 3- Identify mode of transmissions 4- Identify the control measures to treat and eradicate the disease

SCHISTOSOMIASIS A blood fluke (trematode) infection with adult male and female worms living within mesenteric or vesical veins of the host over a life span of many years. Eggs produce minute granulomata and scars in organs where they are deposited.

SCHISTOSOMIASIS Symptoms are related to the number and location of the eggs in the human host: Schistosoma mansoni and S. japonicum give rise primarily to hepatic and intestinal manifestations Early signs and symptoms include diarrhea, abdominal pain and hepatosplenomegaly. S. japonicum can also cause CNS disease, with Jacksonian seizures.

SCHISTOSOMIASIS S. haematobium gives rise to urinary manifestations, and early signs and symptoms include dysuria, urinary frequency and hematuria at the end of urination, CNS disease has, rarely, been reported.

Complications 1- Liver fibrosis, portal hypertension 2- Colorectal malignancy 3- Obstructive uropathy & Superimposed bacterial infection 4- Infertility& Bladder cancer Eggs can be deposited at ectopic sites, including brain, spinal cord, skin, pelvis and vulvovaginal areas.

SCHISTOSOMIASIS The larvae of certain schistosomes of birds and mammals may penetrate the human skin and cause a dermatitis, sometimes known as “swimmer’s itch”, these schistosomes do not mature in humans.

Diagnosis Demonstration of eggs in biopsy specimens, in stool by direct smear or on a Kato thick smear, or in urine by the examination of a urine sediment or Nuclepore filtration. Immunological tests include immunoblot analysis, the circumoval precipitin test, IFA and ELISA, and RIA with purified egg or adult antigens( indicate prior infection and are not proof of current infection).

Infectious agents Schistosoma mansoni, S. haematobium and S. japonicum are the major species causing human disease. S. mekongi, S. malayensis, S. mattheei and S. intercalatum are of importance only in limited areas.

Occurrence S. mansoni is found in Africa, the Arabian Peninsula S. haematobium is found in Africa and the Middle East. S. japonicum is found in China, in Indonesia, no new cases in Japan since 1978 after an intensive control program.

Reservoir Humans are the principal reservoir of S. haematobium, S. intercalatum and S. mansoni, although the latter has been reported to occur in rodents. Humans, dogs, cats, pigs, cattle, water buffalo and wild rodents are potential hosts of S. japonicum. Epidemiological persistence of the parasite depends on the presence of an appropriate snail as intermediate host.

Mode of transmission Infection is acquired from water containing free- swimming larval forms (cercariae) that have developed in snails. The eggs leave the mammalian body in urine& in feces. The eggs hatch in water and the liberated larvae (miracidia) penetrate into suitable freshwater snail hosts.

Mode of transmission After several weeks, the cercariae emerge from the snail and penetrate human skin, usually while the person is working, swimming or wading in water, they enter the bloodstream, carried to blood vessels of the lungs, migrate to the liver, develop to maturity and then migrate to veins of the abdominal cavity.

Incubation period 2–6 weeks after exposure

Period of communicability Not communicable from person to person, people with schistosomiasis may spread the infection by discharging eggs in urine and/or feces into bodies of water for as long as they excrete eggs

Period of communicability It is common for human infections with S. mansoni and S. haematobium to last in excess of 10 years. Infected snails will release cercariae for as long as they live, a period that may last from several weeks to about 3 months.

Methods of control A. Preventive measures: 1) Treat patients in endemic areas with praziquantel to relieve suffering and prevent disease progression. Regularly treat high-risk groups such as school age children, women of childbearing age or special occupational groups in endemic areas.

Preventive measures 2) Educate the public in endemic areas to seek treatment early and regularly and to protect themselves. 3) Dispose of feces and urine so that viable eggs will not reach bodies of fresh water containing intermediate snail hosts.

Preventive measures 4) Improve irrigation and agriculture practices, reduce snail habitats by removing vegetation, by draining and filling, or by lining canals with concrete. 5) Treat snail-breeding sites with molluscicides. Cost may limit the use of these agents.

Preventive measures 6) Individual protection: prevent exposure to contaminated water (e.g. rubber boots). To minimize cercarial penetration after brief or accidental water exposure, vigorously and completely towel dry skin surfaces that are wet with suspected water. Apply 70% alcohol immediately to the skin to kill surface cercariae.

Preventive measures 7) Provide water for drinking, bathing and washing clothes from sources free of cercariae or treated to kill them. Effective measures for inactivating cercariae include water treatment with iodine or chlorine. Allowing water to stand 48–72 hours before use is also effective. 8) Travellers visiting endemic areas should be advised of the risks and informed about preventive measures.

B. Control of patient, contacts and the immediate environment 1) Investigation of contacts and source of infection: Examine contacts for infection from a common source. 2) Specific treatment: Praziquantel is the drug of choice against all species. A single oral dose of 40 mg/kg is generally sufficient for cure rates of 80–90%. Oxamniquine & Metrifonate are alternative drugs for S. mansoni and S. haematobium respectively.

Thank you