Lecture 2 Schistosomiasis

Urogenital System Microbiology… Lecture 2 Schistosomiasis (Schistosoma haematobium) 1 _first: General features: I. II. Adult worms: - Inhabit portal vascular system, and have: 1. Ventral sucker for attachment 2. Cylindrical bodies To fit in the vessels 3. Separate sexes: Male: 1-2 cm in long , with a deep ventral groove “called schist” to carry long and slender female(longer than male) - Adults live for 4- 35 years!! Life cycle: - From the figure: 1. Eggs: found at Terminal spine At submucosal venules, worms lay 300 eggs per day . Then eggs are passed in urine or feces 2. Eggs hatch and release miracidia ( free-swimming ciliated larval stage) 3. Miracidia goes to snells 4. miracidia mature through 1-2 months 5. Matured parasites/ carcariae (with forked tail) go out . 6. Penetrate human Skin 7. Inside the human it becomes as schistosomula larvae, loss it’s tail; with 7 layers in (1-3days) 8. Vascular system (right heart to Lung to left heart to liver/ hepato-portal system) 9. + 10. Mating in the hepato-portal circulation: Then migrate from Inferior Mesenteric system to venous plexus of bladder, ureter and other pelvic organs 2 _Second: Epidemiology: I. II. III. IV. V. Schistosomiasis is a parasitic disease (the most important helminthic infection ) caused by blood flukes (trematodes) of the genus Schistosoma was discovered by Theodore Bilharz, a German surgeon working in Cairo, who first identified the etiological agent Schistosoma hematobium in 1851 Modern sanitation can break life cycle Schistosomiasis has geographical distribution (Common in Egypt) Peak age of Schistosomiasis is 20s. (Working force) _third: clinical diseases: Schistosomiasis/bilharzias snail fever: I. There are 3 stages : - Early stage: (Penetration and migration of the parasite) 1. Intensely pruritic skin rash (due to type I and II Hypersensitivity), in 24 hours of Entrance 2. In 1- 2 week, general (Infections) symptoms appears - Intermediate stage: (Ovi-position and immune-complexes formation) 1. Katayama fever: (acute cases) • Fever, an urticarial rash, hepatosplenomegaly , and bronchospasm due to allergic reaction. • An immune complex phenomenon, initiated by eggs laid by maturing schistosomes. Due to that, eggs trapped in the tissue • four to six weeks after infection. • Diagnosis: Clinically, with Increased: WBC, Eo, IgG, IgM, and IgE - Chronic stage: (granuloma formation) 1. Inflammatory and fibrotic reactions to Retained eggs form granulomas around the trapped eggs 2. involving T cells, macrophages, and eosinophils (common against Parasitic manifestation) 3. Bladder mucosa becomes thickened, Papillated and ulcerated (causing Hematuria and Dysuria ; repeated hemorrhage may cause Anemia (iron deficiency anemia) 4. Bladder muscles may be involved leading to Loss in bladder capacity and contractility(increased frequency of urination) 5. Complications: • Vesicoureteral reflux ( condition in which urine flows backward from the bladder to one or both ureters and sometimes to the 3 • • • • III. IV. kidneys) + ureteric obstruction & hydronephrosis = Renal failure/uremia Calcification of bladder wall then Calculi high risk to get Chronic Salmonella bacteruria Squamous cell bladder carcinoma(precancerous) Other UG organs involved: Spermatic cord, Testes, fallopian tubes, ovaries, and vagina Diagnosis: Collect the first urine specemin (Mid-day sample/ mainly last drop , then: 1. Recovery of eggs and/or concentration method (if the first specemin Is negative ) 2. If negative Filtration of urine 3. Local biopsy (Cystoscopy) can be used 4. Egg viability (microscopically or Hatching) - EIA of antigens in blood and urine (by using dipstick) - Conventional serological tests delayed, need 48 hrs (complement Fixation test, ID injection of Schistosoma Ag) ….. similar to TB test Immunity - Cell mediated immunity against retained eggs (Granuloma formation) by: 1. Role of suppressor T (T-reg) cells 2. Blocking Ab (IgG4) 3. genetically related, HLA mediated immunity (A1 and B5) , this reaction may lead to hepatosplenomegaly - Tolerance to parasites results in Long life of the adult worms (4-35 Y) - Concomitant immunity: 1. Role of protective specific IgE _ Fourth: Treatment & Prevention: - Anthelmintic agents: 1. Praziquantel (agent of choice), oral; One Day 3 doses • contraindicated in breast-Feeding but NOT in pregnancy (u can use it for pregnant) • Resistance is increasing. So either: – Repeat the dose – Use Artemisinin as an alternative (it’s also an anti-malaria drug) - For Prevention: 1. Sanitary disposal of feces and urine 2. Molluscicides (kill snails) are effective 4 3. Multipronged programs, Tried in China show effectiveness for prevention 4. Vaccines is under development _ past years’ questions: ▪ False about schistosomiasis: ………… Answer: hatche egg release cercariae ▪ Regarding Schistosoma and schistosomiasis, all are correct, except: a.Katayama fever occurs at the intermediate stage B. The life span of adult worm is 4 to 35 years C. In life cycle cercanae are formed before miracidia D. Their eggs has terminal spines E. Granuloma formation occurs around returned eggs and tissue The answer is C 5