Schistosoma Flashcards
what is the source of cercarie of schisto
transdermal from freshwater
what is the most important human helminth infection
schistosomiasis
how many people infected with schisto in africa
200 million
how many people die due to schisto in sub saharan africa per yeat
200 000
which parasite was found in 3100 bc mummies
schisto
where does schisto mature un the definitive host
the blood vascular system
schisto is associated with what
renal, bladder dysfunction, liver or intestinal disease
wha are the intestinal schisto parasites
-mansoni
-japonicum
-mekongi
-guineesis, intercalatum
where is mansoni found
middle east africa
caribbean
brazil
venezuela
suriname
where is japonicum found
china
indonesia
philipines
where is mekongi found
cambodia
lao
where is guineensis and intercalatum found
rain forest of central africa
which schisto is urogenital
haematobium
where is haematobium found
middle east africa
corsica aka france
which schisto is the most widely distributed and is endemic in its areas
mansoni
construction of the egyptian dam in the 60s led to what
the virual elimination of haematobium from the nile delta but has brought the establishment of mansoni in upper egypt
construction of diama dam in senegal river led to what
the introduction of schisto into mauritania and senegal
construction of akosombo dam in ghana led to what
the introduction if shisto into lower volta river
the movement of refugees and the displacement of populations resulted to what
the intro of schisto in somalia and djibouti
what are the 3 major species of schisto
mansoni
haematobium
japonicum
true or false: in schisto, females are bigger than males
so true
what are the lil features of male schisto
-oral and ventral sucker
-gynocophoric channel for female to get in
-sturdy body and tuberculated tegument
what is the ;enght of male schisto haematobium
10-15 mm
what is the lenght of mansoni
6-12 mm fp male
what is lenght of male japonicum
12-20 mm
what is the intermediate host of schisto
snail
what is the snail for haematobium
bulinus
what is the snail for mansoni
biomphalaria
what is the snail for japonicum
oncomelaniawhere
are usually the cercariae in
fresh water
how do schisto infect people
they penetrate the skin
what is life cycle of schisto starting from penetration
-penetration of the skin
-cercariae become schistosomula
-larvae migrate first to the lungs through venous circulation
-larvae migrate to the heart and into circulation
-larvae mature in liver
-worms mature and pair off
-worms migrate to mesenteric vessels of bowel or bladder where females lay eggs
-eggs excreted in feces or urine
-eggs get into snail
-miracidia develop into sporocyst and produce cercariae
how long to schisto take to develop into mature miracidium
8-10 days
what is the color of schisto eggs and what is their special characteristiv
they are yellowish brown and elongate with a spine
what is the size of the egg haematobium
140u
what is the size of the egg mansoni
140u
what is the size of the egg japonicum
85u
what is the life expentancy of shisto in tissues
21 days
what is the lenght of the swimming ciliated miracidium and how long does it live for
100-200u and lives 8-12 hrs
miracidium male or female gives rise to what and how long do they live for
-give rise to cercaria of the same sex
-live up to 3-4 days
penetration of schisto is triggered by what
chemical and theremal cues
cercaria penetration is accompanied by what
-the transformation of the free living cercaria to a parasitic larval schistocomulum
Schistosomules enter the capillary bed or the lymphatic
system, migrating to where?
the right side of the heart and then entering the lungs
juveniles of schisto feed on what and then what happens
erythrocyte and grow rapidely
-after 10 days the schistosomules move through the pulmonary vein to the left side of the heart and then into systemic circulation
3 weeks after penetration, the worms of schisto will reach what
hepatic portal vein
initial egg production begins when for schisto?
-4-7 weeks after infection
s mansoni mature females produce how many eggs per day
100-300 eggs
how long do adult schisto adults live
3-8 yrs
what is the first clinical sign of shchisto
skin bumps
what is a clinical sign of s mansoni
cercarial dermatitis
what causes swimmers itch
avian schisto
true or false: cercarian dermatitis is an igg mediated hypersensitivity response
false it is an ige response
what is cercarial dermatitis characterized by
-maculopapular, pruritic rash that manifests within several hours of exposure to the contaminated water and may persist for days
when is acute dermatitis
4-10 weeks after infection
what is the name of the acute stage of the acute stage os schisto and what is it
katayama fever
-normally found in kids or adults with no previous exposure to the disease
-it is a response to the sudden high levels of antigen exposure
-is usually assocuated with the onset of egg deposition
what are the clinical symptoms of acute schisto
-skin rashes
-asthmalike episodes
-daily fever
-malaise
-diarrhea
-swollen lymph nodes
-aching joints
which is most common with katayama fever in terms of which schisto
japonicum
in schisto: accumulation of eggs and fibrotic reactions leads to what
cirrhosis and portal hypertension
-ascites (fluid accumulation in the abdominal cavity) is common
-some eggs pass the liver, lodging in the lungs, brain and other organs
in s haematonium, fibrosis of the bladder may lead to what?
ureteric obstruction and renal failure
true or false: s mansoni can cause growth stunting
true due to chronic infection
pathology of schisto is due to what
egg deposition in tissues and not adult worm
-eggs become surrounded by granulomas and antigen leakage lead to what
delayed type hypersensitivity aka DTH reactions
what is the granuloma
concentric layers of cells that together form the distinctive lesion
what is the central focus of the granulomas of schisto
-formed by 2 cell types:
-epitheloid cells aka macrophages
-multinucleated giant cells (cytoplasmic fusion of macrophages fue to stimulation with macrophages)
what is the next layer after the central focus of granulomas
lymphocytes
what is the outerlayer of schisto granuloma
fibroblasts
what is the immune response of schisto
-th1
-aimed at adult worm in early stages which shifts to eggs induced th2 biased profile 6 weeks post infection
in schisto; egg antigens directly suppress what type of response
th1 response
Major components of the granulomatous response to schistosome eggs in the host liver and the main cytokines and chemokines that regulate
this response. what are the cytokines and chemokines
-il 17, 23, 4, 19, 13 and 5
what is the difference between the 2 pathologies of schisto
-severe: th17, th1 and th2
-mild: th2 and treg
Schistosoma infection triggers a Th2 type response: which types of antigens and cells are involved
-ige
-mast cells
-eosinophila aka il4-5
how is adcc induced in shisto
-by the interaction between the ige and igg with fd receptors on eosinophils
ige dependant killing in shisto is mediated by what
eosinophils
what are the other ways for ig isotypes to also kill
-toi, rni etc
do people with schisto develop age dependent development of immunity
yup the egg counts go lower with age
what is the correlation with igg titers and reinfection
-negative
-aka low igg=high egg count
-high igg=low egg amount
what is the correlation between igm titers and reinfection
-high igm=high egg count aka it is positive
ig in shisto is associated with what
protection
Diagnosis: intestinal schistosomiasis
- History of freshwater exposure
- Stool for O&P (egg counts and viability)
- Serology– Elisa and Western Blot
- Antigen capture
- Eosinophilia
- Rectal snips or biopsies
- Liver biopsy
- Ultrasound or CT of abdomen
tests based on the detection of schisto antigens what happens?
-become positive as soon as antigens are present and become negative quickly after cure
monoclonal antibodies to schisto antigens have led to what
to the development of sensitive dot immuno assays aka very small sample quantities
treatment to schisto
Drug: Praziquantel - WHO recommended dose
40 mg/kg body weight
In case of treatment failure;
S. mansoni - Oxamniquine
S. haematobium – Metrifonate
are there any vaccines for schisto
nope
