Blood Fluke ( Shictosoma Mansoni)

Question 1

Other name ?

Answer 1

• blood fluke

Question 2

Type ?

Answer 2

• trematode

Question 3

Differs from other trematodes by
(6)

Answer 3

1- unisexual
2- lack a muscler pharynx
3- gyencophoral canal in male
4- eggs spine
5- eggs are mature , non operculated
6- cercaria can pentrate the skin

Question 4

Life cycle
(8)

Answer 4

1- adults inhabitant in inferior mesentric venous plexous
2- man is infected by penetration of cercaria by
• protolytic secretion
• surface tension of drying water droplets on wet skin

3- cercaria loses its tail to become schistosomula
4- shcistosomula migrates to rt side of heart ~> lung ( o2 attracts it ) ~> lt side of heart ~> systemic circulation ~> liver

5- in liver it maturate into male, female and then male carries the female on its canal to travel against flow in blood reaching narrow blood vessels that he cant proceeds but female can then it search for the narrowest point to lay the eggs in it

6- 1/3 of eggs pass to exterior due to • lytic action•spine ( desentry) • contraction force of veinules passing to stool , while the remaining eggs are either trapped in intestinal walls or swept back by blood to ectopic regions eg liver , spleen

7- in water , eggs hatch to miracidium that penetrate biomphalaria alexandrina snail to be cercaria
8- the cercaria has forked tails so called fercocercous cercaria

Question 5

Inhabitant- infective- diagnostic- mode of infection- definitve host - intermediate host

Answer 5

Imv- fercocercous cercaria - mature eggs - penetrating skin- man- biomphalaria alexandrina

Question 6

Pathogensis & manifestations

Answer 6

• the main pathology comes from the egg with minor reactions of penetrating cercaria and migrating shictosomula

• stage of penetrating cercaria ( swimmers itch ) (2)
Asymptomatic in endemic areas , in travellers it shows prurits , urtacrial rash

• stage of migrating shictosomula (4)
Lung ( cough - hemoptysis- loeffler syndrome- verminous pneumonitis
Fever
Headache
Allergy due to metabolic products

• stage of egg deposition (2)
- desentry ( egg اللي نزلت (
- right hypochondriac pain ( egg اللي فضلت(

• stage of complication ( granulomatous ) (7)
• intestine : fibrosis- stricture- fistula- pseudopolyps
• liver : granuloma( bilharizeoma)- fibrosis- liver cirrhosis- portal hypertension- hepatomegaly - jaundice
• kidney : glomruli immune complex deposition
• osephagel varices
• heart : cor pulomonale rt sided heart failure
• spleen : hypersplenism ~> hemolytic anemia
• anemia
Hemolytic ~> hypersplenism
Anaplastic ~> chronic diseases ( inflammatory mediators)
Iron deficiency ( microcytic hypochromic ) ~> hematemsis - hemoptysis- desentry - penetration of egg

Question 7

Diagnosis

Answer 7

1- history : if he related to endemic areas or swimming
2- clinical diagnoses
3- laboratory (6)
• kato thick fecal smear is technique for detection, quantification of egg in stool ( after 35:40 days the time the egg pass in stool)
• serology : detect antigen ( CCA) circulating cathodic antigen
Detect antibody ( ELISA)
• CBC: eosinophila , leukocytosis
• indoscope
• ultrasonography
• biopsy in colon ( pseudopolyps) , liver ( egg)

Question 8

Treatment
(3)

Answer 8

1- praziquental (6)
- drug of first choice
- oral
- 40 mg / kg
- single dose
- against adult only
- repeated after two weeks ( shistosomula ~> adult )

2- artimesinin
More effective than prazi
Against all stages

3- surgical

Question 9

Prevention
(4)

Answer 9

1- mass treatment for all infected patients
2- health education
Swimming in infected water with protective boots / gloves
Quick drying of skin
3- sanitary disposal of human excreta
4- snail control ( physical- chemical- biological )
Biological ( planting trees toxic for this snail

Question 10

Swimmers itch
(4)

Answer 10

1- invasion of skin by non human cercaria
2- it cant pass beyond the germinal layer ( circulation)
3- it causes dermatitis/ itching / 2 nd bacterial infection
4- treatment : antihistaminic - antibiotic- antiprurtic