Blood flukes - Schistosoma Flashcards
Schistosomes cause following disease:
snail fever, schistosomiasis or bilharziasis
3 major spp
Schistosoma haematobium, S. mansoni & S. japonicum
Schistosomes differ from other trematodes in several ways:
separate sexes (dioecious)
males have a specialized canal
life cycle patterns
Sexual dimorphism in Schistosoma
males are shorter & stouter than females
ventral gynecophoric canal where female resides
Mouth is surrounded by ___________
strong oral sucker
_____ is near mouth end
acetabulum
___ pharynx, esophagus has prominent __________
No
esophageal glands
Males have _____ testes
5-9
_____ is absent
Cirrus
S. haematobium lives in _________
veins of urinary bladder
S. mansoni lives in _____________
the veins of the large intestine
S. japonicum resides in _____________
the veins of the small intestine
The gynecophoral canal transfers ______ and ______ from the male to the female and vice versa
nutrients
hormones
Eggs must penetrate the:
vein wall before entering the lumen of the gut or the bladder to escape by urine or feces
___ 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
Eggs are _____
embryonated
______ enters the snail host and trasnforms into _____
Miracidium
sporocyst
Sporocysts produce _______ of ______ sporocysts. They move to _________ & produce either additional _________ or the _______
2nd generation migratory digestive gland or gonads sporocyst generations cercarial generation
______ stage absent
Redial
Cercaria leave the sporocyst via _____ and exits the snail’s tissues.
birth pore
This passage is aided by secretions of ______
escape glands
Actively swimming cercaria with forked tails move in a “figure-8” pattern continuously for _____
1-3 days
_____ host absent
2nd intermediate
Upon contact with ______, they are ____________
mammalian skin
attracted to skin’s secretions and attach.
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 isworsefor:
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
