Blood flukes - Schistosoma Flashcards by Taylor Nunes

Schistosomes cause following disease:

snail fever, schistosomiasis or bilharziasis

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3 major spp

Schistosoma haematobium, S. mansoni & S. japonicum

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Schistosomes differ from other trematodes in several ways:

separate sexes (dioecious)
males have a specialized canal
life cycle patterns

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Sexual dimorphism in Schistosoma

males are shorter & stouter than females

ventral gynecophoric canal where female resides

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Mouth is surrounded by ___________

strong oral sucker

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_____ is near mouth end

acetabulum

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___ pharynx, esophagus has prominent __________

esophageal glands

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Males have _____ testes

5-9

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_____ is absent

Cirrus

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S. haematobium lives in _________

veins of urinary bladder

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S. mansoni lives in _____________

the veins of the large intestine

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S. japonicum resides in _____________

the veins of the small intestine

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The gynecophoral canal transfers ______ and ______ from the male to the female and vice versa

nutrients

hormones

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Eggs must penetrate the:

vein wall before entering the lumen of the gut or the bladder to escape by urine or feces

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___ of the eggs produced reach the exterior; the remaining eggs:

~ 1/3

are either trapped in the urinary bladder or intestinal walls or swept back by the blood flow & become lodged in liver, spleen and other areas

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Eggs are _____

embryonated

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______ enters the snail host and trasnforms into _____

Miracidium

sporocyst

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Sporocysts produce _______ of ______ sporocysts. They move to _________ & produce either additional _________ or the _______

2nd generation
migratory
digestive gland or gonads
sporocyst generations 
cercarial generation

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______ stage absent

Redial

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Cercaria leave the sporocyst via _____ and exits the snail’s tissues.

birth pore

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This passage is aided by secretions of ______

escape glands

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Actively swimming cercaria with forked tails move in a “figure-8” pattern continuously for _____

1-3 days

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_____ host absent

2nd intermediate

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Upon contact with ______, they are ____________

mammalian skin

attracted to skin’s secretions and attach.

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How do they penetrate skin?

With the help of secretions from penetration glands

Infective stage:

Cercaria

Within 24 hrs,

schistosomula enter peripheral circulation and are swept off to the right side of the heart

Schistosomules appear in ______ by _____ since penetration. They start to feed on ____, and ________

pulmonary capillaries day 3 RBCs grow rapidly

After ____ days, they move through the _______ to the right side of the heart and then into ________

7-10 pulmonary vein systemic circulation

In ____, they reach _________ veins and attain ____________

~3 wk hepatic portal sexual maturity

Worm pairs then migrate to:

their preferred sites in the body

Adult worm usually lives for ____ years

2-5

Females that are unpaired:

do not become sexually mature and have the appearance of starving

Greater than ____ cases annually

250 million

Single most serious disease in china

S. japonicum

High incidence rates:

Africa, Asia, parts of South America, and several Caribbean islands

Schistosomiasis is the most common cause of ________

bladder calcification

Serious complication of urinary tract schistosomiasis

is an increased incidence of cancer of the bladder

Schistosomiasis affects ____ more often than ____ in ratio of ___

men women 9:1

What age group is infectged?

Younger than 30

The disease is worse for: | who can develop:

children | anemia, learning difficulties and malnutrition

single most important epidemiological factor in schistosomiasis

Human waste in water containing snail hosts

Control

Adequate sewage treatment is sufficient to eliminate schistosomiasis, such treatment is lacking in many poor countries

Vulnerable groups:

Farmers wading in irrigation water fisherman wading in lakes and streams children playing in contaminated body of water women washing clothes in streams

S. mansoni is found in

many countries in Africa, South America, the Caribbean and in parts of the Middle East.

S. mansoni reservoir hosts

not important for this spp

S. haematobium is found in `

Africa, Arabia, the Middle East

S. haematobium reservoir hosts

Reservoir hosts are not thought to be of importance for this species.

S. japonicum is found in

China and the Philippines but no longer in Japan where successful control programs have been implemented

S. japonicum reservoir hosts

Control of this parasite is complicated as many reservoir hosts exist

Swimmers itch

Cercarial dermatitis | caused by cercariae of bird blood fluke

Symptoms of swimmers itch

intense itching and local edema

Bird blood fluke

does not enter the blood stream and instead, destroyed by the human’s immune system.

Schistosomiasis typically causes

chronic low-grade infection with flu-like symptoms

Clinical symptoms may include

fatigue, headache, a stiff neck, lack of energy, and neurologic symptoms due to CNS complications

Initial phase:

4-10 wk after infection, during which migration takes place from lungs to liver to hepatic portal system

Initial phase symptoms

Fever and allergies (frequently skin rashes), abdominal pain, bronchitis, enlargement of the liver and spleen, and diarrhea are common symptoms.

Intermediate phase:

lasting 2 months to many years after infection. Bloody stools/urine result as intestines/bladder are most notably affected

Final phase:

characterized by severe intestinal, renal, and hepatic pathology, caused primarily by rx. of the host to the eggs.

Lodged eggs become small _______ which are also called ________

fibrous nodules Granulomas, Pesudotubercles

Repeated infection of ______ commonly lead to ________

S. haematobium bladder cancer

A marked enlargement of ________ occurs as well as ______

Spleen/liver (hepatosplenomegaly) | ascites

3 phases:

Initial intermediate final

Urogenital schistosomiasis

common in Africa and Middle East

There is a link between ____ and _____

FGS | HIV

FGS

Female genital Schistosomiasis

FGS symptoms

lesions of the cervix and vagina, vaginal bleeding, pain during sexual intercourse

genital schistosomiasis in men

Affects seminal vesicles and prostate glands and may lead to infertility

Most severe spp

japonicum becasue they produce the most eggs in a day

______ of _____ eggs are not excreted, instead they build up in _____.

~ two-thirds S. japonicum the gut

Eggs may enter _______________, which may lead to __________-

lungs, brain, spinal cord and other organs paralysis, coma, death

Build up of eggs can lead to

fibrosis and ulceration

Diagnostic tool:

Eggs in stool or urine

Treatment

Praziquantel for 3 days

Schistosomes acquire

Host antigens on surface which protect it for immune system detection

Antigen acquisition occurs in:

Early schistosomule stage | Best target for vaccine

Pervention

avoid bodies of water in endemic areas

5 methods of control:

``` prevention of water contact mass chemotherapy destruction of snails by chemical or biological agents (crayfish) alteration of habitats sanitary disposal of feces, urine ```

Two other schistosomes:

S. mekongi | S. intercalatum

S. intercalatum found in

Camaroon and Zaire (Africa)

S. mekongi found in

southeast Asia, especially Laos and Cambodia

S. mekongi closely resembles

S. japonicum It has a different snail host, and its eggs are smaller

S. intercalatum is related to

S. haematobium Has terminal spine but eggs are secreted from feces less pathogenic

Blood flukes - Schistosoma Flashcards

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