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Lecture of schistosomiasis.ppt

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Lecture of schistosomiasis.ppt Powered By Docstoc
					Prepared by Dr. Salem Bin Selm

Schistosomiasis

CAUSES:
► Schistosomiasis

or bilharzia

 Blood-dwelling fluke worm of the genus

Schistosoma.
►S.

 5 main species:
Haematobium ►S. Mansoni ►S. Japonicum ►S. Mekongi ►S. Intercalatum

Epidemiology:
► >200 million infected worldwide ► >200,000 deaths annually ► S. Mansoni- Subsaharan Africa, Middle

South America, Carribean S. ► S. Haematobium- North Africa, Subsaharan Africa, Middle East, India ► S. Japonicum- China, Phillipines, Thailand, Indonesia
► S. Mekongi- Southest Asia ► S. Intercalatum- Africa, Middle ► Prevalence in Yemen 10-20%

East,

East

► Infection

areas ► Peaks at age 15-20 ► Intensity of infection decreases with age ► Transmission higher in rural areas ► Higher risk near lakes and rivers.

acquired in childhood in endemic

Life Cycle:
larvae penetrate skin ► migrate in the blood via lungs to liver ► become schistosomule mature over 4-6 weeks in the portal vein ► migrate to perivesical or mesenteric venules ► female worm produces 100-3000 eggs/day which migrate to lumen of bladder or intestine ► Eggs excreted in urine or feces
► Cercarial

► On

contact with water, egg releases miracidium (immature larvae) ► Miracidium finds the intermediate host, freshwater snails. ► Multiply asexually into cercarial larvae ► Cercariae leave snail at 4-6 weeks and spin in water for 72 h seeking a suitable host

pathophysiology
Allergic Dermatitis ► Schistosomula : cough and fever ► Adult worm: Adult worms are rarely pathogenic ► Eggs: They cause Katayama fever and schistosomiasis. ► Katayama fever :result from immune complex formation and lead to a serum sickness–like illness ► Schistosomiasis:due to immunological reactions to Schistosoma eggs trapped in tissues. Antigens released from the egg stimulate a granulomatous reaction
► Cercariae:

Clinical Manifestations:
► Acute

Manifestations :

 More common in travelers  Swimmer’s itch  Katayama fever
► Chronic

Manifestations :

 Endemic areas  Higher burden of infection

►Katayama Fever ►4-8 weeks after exposure ►Hypersensitivity reaction ►, myalgias, arthalgias, dry cough, diarrhea, Lymphadenopathy, HSM ►Peripheral eosinophilia ►Feces often negative for eggs ►Symptoms usually resolve after a few weeks

Chronic infection:
►Intestinal  Abd. pain, diarrhea- bloody or nonbloody  Secondary iron deficiency anemia  Intestinal polyps  Bowel ulcers and strictures ►Hepatic  HSM secondary to portal HTN  Deposition of collagen in periportal spaces  Periportal pipestem fibrosis- Symmer’s fibrosis  Ascites, varices  Normal hepatocellular function

► Urinary

      

May be asymptomatic Micro or macroscopic hematuria Dysuria, frequency Recurrent UTI Obstruction, hydroureter or hydronephrosis Proteinuria, nephrotic syndrome Increased risk of Ca. of bladder

► Female

genital schistosomiasis ( FGS )

► Neuro

   

Granulomas in spinal cord, brain Transverse myelitis Lower limb pain, weakness, bladder dysfunction epilepsy

► Pulmonary
 Seen more often if hepatosplenic disease present  Presinusoidal portal HTN  portosystemic collaterals  allows schistosomes into pulmonary circulation  Eggs lodge in arterioles granulomas, endarteritis  pulm HTN and cor pulmonale  Dyspnea  CXR: fine miliary nodules  Cardiac enlargement, dilated pulmonary arteries  With initiation of treatment►embolization of worms to lungs  cough, wheeze and new infiltrates ►Self limited

Complications
bleeding ► GI obstruction ► Malnutrition ► Schistosomal nephropathy ► Renal failure ► Pyelonephritis ► Bladder cancer ► Sepsis (Salmonella) ► Pulmonary hypertension ► Cor pulmonale ► Neuroschistosomiasis
► GI

Diagnosis
history (in non-endemic areas). ► A history of dermatitis or Katayama fever. ► Urine dipstix for blood +/or protein (painless terminal haematuria) ► Bloody dearrhea ► Blood eosinophilia ► Urine microscopy (for the ova) ► Stool microscopy ► Rectal biopsy ► Serological markers
► Travel

►Gold

Standard: Microscopy of urine or stool  S. Mansoni- prominent lateral spine  S. Haematobium- terminal spine  S. Japonicum- small,inconspicuous spine

Diagnosis:

► Nonspecific

lab findings:

 Peripheral eosinophilia  Anemia  Thrombocytopenia- if hepatosplenic involvement  Mild elevation AP, GGT.

► Antibody

assays:

 Look for antischistosomal Abs  Does not distinguish current infection from past infection  Bad test in endemic areas  Good for travelers  Abs stay positive for up to 22 weeks after treatment.

► Antigen

detection:

 Can be used to assess cure  Ag negative 5-10 days after treatment  Used mostly for epidemiological and therapeutic studies  Development of fingerstick tests

Treatment
►

Three new drugs have revolutionized treatment: all forms of schistosomiasis, with virtually no side effects.

Praziquantel – effective in the treatment of
Oxamniquine Metrifonate

– used exclusively to treat intestinal schistomiasis (s. mansoni) in Africa and South America. – effective for the treatment of urinary schistomiasis.

Treatment:
►

Praziquantel:

 MOA: induces changes in structure of worm tegument ► Increased permeability to calcium ions muscular contractions and paralysis ► Exposes parasite Ag to immune response dislodgement of worms and expulsion by peristalsis

 Dose:

egg count.  Side effects: nausea, abd pain, diarrhea  Efficacy: Cures >85%, decreases Ag concentrations in >95%  Test for cure: stool cx >6 weeks post treatment.

► 40 mg/kg in single dose OR ► 60mg/kg in 2 divided doses

– in populations with high

Prognosis
disease usually improves with treatment. ► Hepatic, renal, and intestinal pathology improves with treatment. ► Hepatosplenic schistosomiasis carries a relatively good prognosis because hepatic function is preserved until the end of the disease (unless variceal bleeding occurs). ► Cor pulmonale usually does not improve significantly with treatment
► Early

Prevention:
► ► ► ► ►

Safe water Sanitation, sewage control Eradication of snail species Education Mass chemotherapy
 Targeted at adolescents- yearly administration of praziquantel
transmission, decreases intensity of infection ► Difficult in low-income countries ► Concern for development of resistance
► Decreases

►

Vaccine Development


				
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posted:6/29/2009
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