Schistosomiasis PDF

Schistosomiasis By Prof. Ameer kadhim Hussein M.B.Ch.B. FICMS (Community Medicine)  Objectives Describe and discuss the epidemiology, mode of transmission and preventive and control measures of Schistosomiasis  Schistosomiasis (Bilharzia) Sometime...

Schistosomiasis By Prof. Ameer kadhim Hussein M.B.Ch.B. FICMS (Community Medicine)  Objectives Describe and discuss the epidemiology, mode of transmission and preventive and control measures of Schistosomiasis  Schistosomiasis (Bilharzia) Sometimes referred to as bilharzias, bilharziasis, or snail fever, schistosomiasis was discovered by Theodore Bilharz, a German surgeon working in Cairo, who first identified the etiological agent Schistosoma hematobium in 1851.  Epidemiology Schistosomiasis is a parasitic disease caused by flukes (trematodes) of the genus Schistosoma. After malaria and intestinal helminthiasis, Schistosomiasis is the third most devastating tropical disease in the world, being a major source of morbidity and mortality for developing countries in Africa, South America, the Caribbean, the Middle East, and Asia. More than 140 million people are infected with schistosomiasis. An estimated 700 million people are at risk of infection in 76 countries where the disease is considered endemic, as their agricultural work, domestic chores, and recreational activities expose them to infested water. Globally, 200,000 deaths are attributed to schistosomiasis annually. Transmission is interrupted in some countries.  Epidemiology The World Health Organization (WHO) estimates that about 220.8 million people required preventive treatment for schistosomiasis in 2017. An estimated 102.3 million people were treated the same year. Estimates show that at least 236.6 million people required preventive treatment in 2019.  Epidemiology Schistosomiasis is more common in males, most likely because of increased exposure to infected water via bathing, swimming, and agricultural activities. S haematobium causes genital lesions in 30% of women who are infected. Vulval lesions may increase the risk of HIV transmission. The prevalence and severity of schistosomal infections vary with age. Children and adolescents are infected most often and are infested most heavily. Globally, infections peak in individuals aged 10-19 years. In some areas, the prevalence in this group may approach 100%. Age distribution differs somewhat in infected travelers, with young adults most likely to be exposed and infected. Egg of Schistosoma hematobium, with its typical terminal spine  Schistosomiasis Most human schistosomiasis is caused by S haematobium, S mansoni, and S japonicum. Less prevalent species, such as S mekongi and S intercalatum, may also cause systemic human disease. Less importantly, other schistosomes with avian or mammalian primary hosts can cause severe dermatitis in humans (eg, swimmer's itch secondary to Trichobilharzia ocellata).  Snail hosts The different species of Schistosoma have different types of snails serving as their intermediate hosts; these hosts are as follows: Biomphalaria for S mansoni Oncomelania for S japonicum Tricula (Neotricula aperta) for S mekongi Bulinus for S haematobium and S intercalatum  Types Species Geographical distribution Intestinal Africa, the Middle East, the schistosomiasis Schistosoma mansoni Caribbean, Brazil, Venezuela and Suriname Schistosoma japonicum China, Indonesia, the Philippines Several districts of Cambodia and Schistosoma mekongi the Lao People’s Democratic Republic Schistosoma guineensis and Rain forest areas of central Africa related S. intercalatum Urogenital Schistosoma Africa, the Middle East, Corsica. schistosomiasis haematobium  Species Reservoir S. Haematobium Humans. Mainly humans but also S. Mansoni reported in rodents. Humans and domestic S. japonicum animals like (dogs and cats) and wild rodents. Miracidia larva with cilia Cercariae with forked tail Paired male & female  WHO case definition in endemic area A. For urinary schistosomiasis: Suspected case: Visible hematuria or positive reagent strip for hematuria Confirmed case: eggs of S. haematobium in urine. B. For intestinal schistosomiasis: Suspected case: non specific abdominal symptoms, blood in stool, hepatosplenomegaly. Confirmed case: Presence of eggs in the stool. Incubation period: Acute systemic manifestation ( katayama fever) including fever, urticaria, malaise and diarrhea may occur 2-6 weeks after exposure which immediately preceding and during initial egg deposition. This manifestation is un common but can occur with S. haematobium. Period of communicability: Not communicable from one person to another. Persons with S. may spread infection as long as excrete the eggs in urine or stool to water bodies. It last in excess of 10 years in S. haematobium and S. Mansoni. Infected snail persist in release cercariae as long as they live (several weeks to about 3 months). Susceptibility: is universal. Any immunity developing as result of infection is variable and not yet fully investigated.  Clinical manifestations In patients with intestinal schistosomiasis, the symptoms include Fatigue, Abdominal pain, Diarrhea, Dysentery. In patients with urinary schistosomiasis, the symptoms include Dysuria, Urinary frequency, Terminal hematuria. Cardiopulmonary schistosomiasis may cause larval pneumonitis with a cough, mild wheezing, and a low-grade fever. CNS schistosomiasis symptoms include Focal and generalized seizures and Headache. Female genital schistosomiasis the symptoms include Postcoital bleeding, Genital ulceration, Irregular menstruation and Pelvic pain.  Complication Gastrointestinal (GI) bleeding GI obstruction Malnutrition Schistosomal nephropathy Renal failure Pyelonephritis Hematuria Hemospermia Sepsis Pulmonary hypertension  Complication Cor pulmonale Neuroschistosomiasis - Transverse myelitis, paralysis, and cerebral microinfarcts Infertility Severe anemia Low ̶ birth-weight babies Spontaneous abortion Higher risk for ectopic pregnancies  Complication End-organ disease Portal hypertension Obstructive uropathy Pregnancy complications from vulvar or fallopian granuloma Carcinoma of the liver, bladder, or gallbladder Granuloma in the liver due to Schistosoma mansoni. The S. mansoni egg is at the center of the granuloma  Diagnosis Microscopic Detection Demonstration of eggs in stool or urine sample. S. haematobium eggs are oval and have a spike at the tip. S. japonicum eggs small and S. mansoni S. japonicum almost spherical with tiny spine. S. mansoni eggs have a spike on the side. Immunological tests including ELISA and IFA are useful in diagnosis. S. haematobium  Treatment Patients should receive antischistosomal drugs and corticosteroids, especially if acutely ill. Steroids reduce inflammation and help suppress changes that result from killing of the parasites. As maturing schistosomes are less susceptible to therapy than adult worms, a second course of treatment is necessary. This is given several weeks after the first course of therapy. The drug of choice for treating all species of schistosomes is praziquantel. Cure rates of 65-90% have been described after a single treatment with praziquantel. In individuals not cured, the drug causes egg excretion to be reduced by 90%.  Treatment Praziquantel can be used in pregnant and lactating women. Resistance to praziquantel occurs. Adverse effects include dizziness, headache, nausea, vomiting, diarrhea, abdominal discomfort, bloody stool, urticaria, and fever following initiation of treatment. These are usually mild and last about 24 hours. If patients present with seizures, anticonvulsant therapy may also be needed. Swimmer’s itch and Katayama Fever are usually treated symptomatically. Drugs ineffective when fibrosis has developed, treatment is then focused on managing the complications (e.g. portal hypertension). Surgical care includes removal of tumor masses, ligation of esophageal varices, and porta-caval shunt surgeries.  Treatment Others: Metrifonate against S. haematobium. Niridazole against S. japonicum. Oxamniquine against S. mansoni.  Methods of controls 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 and special occupational groups in endemic areas with presumptive curative doses. 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 freshwater containing intermediate snail hosts.  Methods of controls 4. Improve irrigation and agriculture practices reduce snail habitats by removing vegetation or by draining and filling or by lining canals with concrete. 5. Treat snail breeding sites with molluskicides. Cost may limit the use of these agents. 6. Individual protection: prevent exposure to contaminated water by wearing rubber boots. To minimize cercarial penetration after accidental water exposure dry skin and apply 70% alcohol immediately to the skin to kill surface cercariae. 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 sand 48-72 hours before use is also effective.  Methods of controls 8. Travelers visiting endemic areas should be advised of the risks and informed about preventive measures. B. Control patient, contacts and immediate environment : 1.Report to local health authorities. 2.Isolation, quarantine, immunization of contacts: Not applicable. 3. Concurrent disinfection: Sanitary disposal of feces and urine. 4. investigation of contacts and source of infection: Examine contacts for infection from a common source. 5. Specific treatment: Praziquentel is drug of choice for all species. Alternative drugs are oxamniquine for S. mansoni and metrifonate for S. haematobium.  Epidemic measures 1. Examine for schistosomiasis and treat all infected especially those with moderate to heavy intensity of infection (children). 2. Provide clean water, avoid water contamination and warn people about risk of contact with contaminated water. 3. Treat areas that have high snail density with molluskicides. Thank you