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Questions and Answers
What is the characteristic feature of the body of trematodes?
Which type of fluke is responsible for water-borne parasitic disease?
Where do adult worms of S.mansoni inhabit in the human body?
What is the intermediate host of the schistosome life cycle?
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What is the process by which the conjoined couple of worms ascend the mesenteric vessels?
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What is the type of reproduction that occurs within the intermediate host?
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What is the primary site where the eggs of S.haematobium are discharged?
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What is the intermediate host for S.mansoni?
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What is the primary site where the eggs of S.mansoni and S.japonicum are swept back into the circulation and lodge in?
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What is the final host for S.japonicum?
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What is the stage of the parasite that penetrates human skin?
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What is the most significant pathology associated with in schistosomiasis?
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What is the result of a granulomatous reaction surrounding the eggs in the liver with S.mansoni and S.japonicum?
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What is the characteristic of S.haematobium infections?
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What is the term for the symptoms that occur after cercarial penetration in travelers to endemic countries?
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What is the primary cause of morbidity and mortality in chronic schistosomiasis?
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What is the duration of localized pruritus after cercarial penetration?
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What is the incubation period for the development of Katayama syndrome in non-immune individuals?
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What is a common symptom associated with the onset of fever in this syndrome?
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What is the result of gradual accumulation of scar tissue within the bladder and ureters?
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What type of inflammation is formed by host lymphocytes, eosinophils, and macrophages in response to trapped parasite eggs?
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What is the result of eggs passing into the brain, spinal cord, and meninges?
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What is the outcome of the inflammation associated with scar formation in the bladder and ureters?
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What is the result of chronic systemic inflammatory illness in this syndrome?
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What is the primary goal of controlling schistosomiasis infection?
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What is the mechanism of action of Praziquantel against Schistosoma species?
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What is the typical diagnostic method for schistosomiasis?
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What is the recommended treatment for Katayama syndrome?
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What is the consequence of schistosomiasis infection if left untreated?
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What is the effective way to prevent schistosomiasis infection?
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What is the possible outcome of inflammation caused by Schistosoma infection?
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What is the primary mechanism of action of Praziquantel against Schistosoma species?
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What is the most effective way to control Schistosoma infection?
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What is the primary purpose of biopsies in diagnosing Schistosoma infection?
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What is the role of antihistamines and corticosteroids in treating Katayama syndrome?
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What is the result of the granulomatous reaction surrounding the eggs in the liver?
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What is the primary method of diagnosing Schistosoma infection?
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What is the consequence of chronic Schistosoma infection?
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What is the primary goal of controlling Schistosoma infection?
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What is the effect of Praziquantel on the Schistosoma worms?
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Study Notes
Trematodes (Flukes)
- Leaf-like, unsegmented flat worms with two suckers (oral and ventral)
- Body consists of a mouth surrounded by oral suckers, a pharynx, and an esophagus; anus is absent
Classification
- Blood fluke
- Intestinal fluke
- Hepatic fluke
- Lung fluke
- Blood flukes: Schistosoma japonicum, Schistosoma mansoni, and Schistosoma haematobium cause water-borne parasitic disease (Schistosomiasis or Bilharziasis)
Life Cycle
- Adult dioecious (male and female) sexual stage within the definitive host (human)
- Asexual reproductive stage within an intermediate host (snail)
- Female schistosomes lay hundreds or thousands of eggs per day within the venous system
- Eggs are discharged in urine (S. haematobium) or feces (S. mansoni and S. japonicum)
- In water, eggs hatch, releasing miracidia (first larval stage)
- Miracidia are eaten by certain snails (intermediate hosts)
- Miracidia develop to a second larval stage (sporocyst stage) and then the infectious stage cercariae
- Cercariae leave the snail and swim to penetrate human skin
- Cercariae transform into schistosomules, which enter the peripheral circulation and eventually become adults in the hepatoportal system or venous plexus surrounding the bladder
Pathology and Pathogenesis
- Most significant pathology is associated with schistosome eggs, not adult worms
- Eggs cause granulomatous reaction, leading to fibrosis in the liver with S. mansoni and S. japonicum
- Chronic cases lead to portal hypertension, accumulation of ascites in the abdominal cavity, hepatosplenomegaly, and esophageal varices
- S. haematobium infections involve urinary tract: urethral pain, increased urinary frequency, dysuria, hematuria, and bladder obstruction leading to secondary bacterial infections
Signs and Symptoms
- Acute manifestations: localized pruritus, urticarial rash, fever, headache, chills, diarrhea, and eosinophilia (snail fever or Katayama fever)
- Chronic systemic inflammatory illness: weight loss, hepatosplenomegaly, diarrhea, constipation, and dysentery-like illness with bloody bowel movements
- Bilharzia: S. haematobium eggs trapped in host tissues, leading to delayed-type hypersensitivity granulomatous inflammation, scar formation, and obstruction, resulting in hydronephrosis, bladder calcification, and squamous cell carcinoma of the bladder
Diagnosis
- Detection of ova in fecal or urine smear preparations
- Invasive procedures—biopsy material are effective in visualizing eggs when the stool or urine sample testing is negative
- Serology: S. mansoni, S. haematobium, S. japonicum
Treatment
- Praziquantel is active against all Schistosoma species
- Praziquantel’s mechanism of action: damages the worm’s outer tegument membrane, exposing the worm to the body’s immune response, leading to worm death
- No specific therapy is available for the treatment of Katayama syndrome
- Antihistamines and corticosteroids may be helpful
Control of Infection
- Eradication of the intermediate snail hosts
- Prevention of water pollution with human excreta
- Avoidance of swimming in contaminated water
- Effective treatment of infected persons
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Description
Test your knowledge on Trematodes, also known as flukes, a type of flat worm. This quiz covers their life cycle, pathology, signs and symptoms, diagnosis, treatment, and control of infection.
