Intestinal Infections by Trematodes Flashcards
What is the disease caused by Heterophyes heterophyes?
Heterophyiasis
Morphology of Heterophyes heterophyes
- Adult :
* This is the smallest trematode parasite of man
* Pear shaped or may take different shapes.
* In addition to oral and ventral suckers it also possess a genital sucker - Eggs :
* Operculated and emberyonated (contain a fully developed miracidium)
What is the definite host in Heterophyes heterophyes
- Man
2. Fish eating animals
First intermediate host in Heterophyes heterophyes
Snails of the genera Pironella
Second intermediate host in Heterophyes heterophyes
- Fishes, such as the mullet and tilapia (Bolty & boury)
* Infective stage: encycted metacercaria in fishes
Mode of transmission in the 2nd intermediate host
eating undercooked or freshly salted containing encysted metacercaria
Clinical findings of Heterophyes heterophyes
- Colicky pain and diarrhea
2. Egg emboli
Explain what is the egg emboli
Eggs may find their way through the genital sucker and are carried in
the lymphatic and portal circulation to ectopic extra-intestinal sites
such as the brain, spinal cord and myocardium
Laboratory diagnosis of H. heterophyes
Detection of the minute operculated eggs in faeces
Morphology of Schistosoma mansoni
- Adult worm lives in the inferior mesenteric vein plexus
- Adult form:
* have their integuments studded with prominent coarse tubercles (to differentiate from Schistosoma haematobium) - Gravid female :
* uterus contains very few eggs, usually 1–3 only - Oral and ventral suckers are prominent in males and rudimentary in females
- Male carries the female inside gynecophoric canal
- Eggs :
* non operculated and yellowish brown
* have the characteristic lateral spine more near to the rounded posterior end
Name the disease caused by Schistosoma mansoni
Intestinal schistosomiasis (Intestinal bilharziasis)
Who is the definite host in Schistosoma mansoni?
Humans are the only natural definitive hosts
Who is the intermediate host in Schistosoma mansoni?
Fresh water snails of the genus Biomphalaria
Mode of transmission in S.mansoni
- cercaria skin penetration during water use (swimming washing, …)
- Humans :
a. schistosomulae mature in the liver
b. the adult worms move against the blood stream into the venules of the inferior mesenteric group in the sigmoidorectal area
c. Eggs : penetrate the gut wall, reach the colonic lumen, and are shed in feces
Clinical manifestations of S.mansoni
- Cercarial dermatitis
- Katayama fever
- Intestinal bilharziasis
- eggs deposited in the gut wall
- Ectopic lesions
- Portal hypertension
The pathogenicity of Cercarial dermatitis
Following skin penetration by cercariae, a pruritic rash may develop locally. It is self-limiting
Pathogenicity of Katayama fever
- after 4-8 weeks of cercarial invasion a serum sickness like illness may happen during production of eggs by females.
- It results from egg antigen stimuli, which leads to formation of immune complexes.
- Sign and symptoms include :
- fever
- rash
- arthralgia
- lymphadenopathy
- hepatosplenomegaly
- eosinophilia
What happens when eggs deposits in the gut due to S.mansoni ?
cause inflammatory reactions leading to microabscesses, egg granulomas, hyperplasia, and eventual fibrosis
Pathogenesis of Intestinal bilharziasis
During the stage of egg deposition in the large intestine:
- the patients develop pain in abdomen and bloody dysentery, which may go on intermittently for many years
In s.mansoni ; Portal hypertension may cause________
gastrointestinal hemorrhages
Ecoptic lesionnin S.mansoni
Include :
- hepatosplenomegaly
- periportal fibrosis
- portal hypertension as some of the eggs are carried through portal circulation into liver.
What is the result of stool microscopic examination in s.mansoni ?
Eggs with lateral spines may be demonstrated microscopically in stools
What is seen in rectal biopsy of S.mansonim?
Proctoscopic biopsy of rectal mucosa may reveal eggs
What is the imaging test result of S.mansoni?
Ultrasonography is useful to detect hepatosplenomegaly and periportal fibrosis
