This presentation covers Helminths. Classification of helminths. Morphology and life cycles. Nematodes,Cestodes,Taenia worms.
1 of 16
Download to read offline
More Related Content
Short Overview of HELMINTHS(Microbiology)
1. Helminthes:
Trematodes (flukes):
SCHISTOSOMES:
Schistosomes are unisexual blood flukes that have worldwide
distribution,
Three species arc known to affect man:
1- Schistosoma hematobium:
• Found in Middle East, Africa, Portugal and Cyprus
• Definitive host: man
• Intermediate host: snail
• It causes urinary bilharziasis (female deposits eggs in the
vesical and pelvic plexus of venous circulation).
2. a
2 - Schistosoma mansoni:
• Found in Middle East, Africa, Sooth America
• Definitive host: man
• Intermediate host: snail (Biomphilaria)
• It causes intestinal bilharziasis (female deposits eggs in mesenteric
venous circulation.
3- Schistosoma Japonicum:
• Found in Far East
• Definitive host: man, domestic animals (dogs, pig, cats)
Intermediate host: Snail (onchomelania)
• It causes intestinal bilharziasis (female deposits eggs in mesenteric
venous circulation.
3. MORPHOLOGY:
Male:
10-20 x I mm with short anterior cylindrical pan and posterior
flattened part which incurved ventrally to form the gynaeccphoric
canal.
It has well developed oral and
ventral suckers.
Female:
15-25 x 0.25 mm:, cylindrical,
ovary may "be central, anterior
or posterior, uterus may be short
or long containing eggs.
4. Schistosoma Eggs:
S. hematobium :
140x50 µ, oval with terminal spine. Passes in urine and sometimes in
stool
S. mansoni:
150x60 µ,oval with lateral spine ,passes with feces and sometimes in
urine.
S. Japonicum : 80x60 µ sub-rounded, spineless with tubercle like
projection, Pass with stool.
6. CLINICAL PICTURE:
The clinical pictures of Schistosoma (Schistosomiasis) is mainly due
to egg deposition with tearing action of the spine in early stags and
fibrosis around the eggs in late stages.
The clinical picture is divided into three stage:
1-Incubation period; (acute Schistosomiasis 6-12 Weeks) :
This stage is characterized by skin irritation after coming from
water, and coughing.
Late in the incubation period, patients complains of enlarged liver, fever,
headache, anorexia, loss of weigh. CBC shows Eosinophilia.
2- Stage of egg deposition: (1- 5 years after infection).
Urinary bilharziasis: caused by S.hematobium, characterised by
terminal haematuria, burning sensation during urination.
Intestinal bilharziasis: dysentery with frequent defecation.
blood and mucous in stool.
7. a
3-Stage of complication: due to a fibrosis around the eggs in
bladder, rectum, colon, liver and lung.
It occurs 2 to 5 years after infection depending on
severity of infection and immunity of the patients.
A- Urinary bilharziasis: cystitis, hydronephrosis and
Pyonephrosis , sterility in males,
renal failure, cancer bladder,
pulmonary hypertension and
heart failure.
B- Intestinal bilharziasis: fever, Jaundice,
portal hypertension,
and Hepatospleenomegaly.
8. Nematoda:
Nematodes are cylindrical non-segmented unisexual worms.
They have body cavity containing fluids in which organs float.
Anal and genital opening are separate in female and united in male
(Cloaca).
Mouth may be provided with lips, papillae and teeth.
Ascaris lumbricoides :
Distribution: worldwide
Habitat: Free in small intestine
D.H.: Man, no intermediate host (direct life cycle).
Morphology: Whitish yellow cylindrical worms,
male 15-25 cm x 3 mm with posterior
curved end, female 20 -40 cm x 5mm
with tapering posterior end.
it lays around 200000 eggs per day.
10. TYPES OF ASCARIS EGGS:
1-Fertilized egg (corticated mamillated egg):
60x45µ, oval, thick walled, shell is covered with a layer of
albuminoid mamillation, contains unsegmented fertilized embryo.
2-Decorticated egg: no albuminoid mamillation.
3-Unfertilized egg: elongated 90x45 µ, dark, ill developed
mamillation, and contains multiple refractile granules.
4- Embryonated egg: like corticated egg, embryo in form of larva.
11. CLINICAL PICTURE:
1- Pulmonary: cough, Sputum production.
2-Intestinal: abdominal pain, nausea, vomiting, abdominal distension
and indigestion.
3- Complication:
Light infection: obstruction of bile duct, pancreatic duct and appendix
leading respectively to jaundice, pancreatitis and appendicitis.
Peritonitis may occur
Heavy infection: Intestinal obstruction and bronchopneumonia.
12. Cestoda:
Cestodes are flattened segmented, hermaphroditic worms (Tapeworm)
with body differentiated into:
Scolex: 1-2 mm, carries, organ of fixation in the form of suckers or
bothria.
Neck actively dividing parts which gives rise to segments
Segments (Strobila): start with immature segments followed by mature
segments with well-developed reproductive organs and then by gravid
segments with well gravid uterus.
13. FAMILY: TAENDDAE
TAENIA WORMS:
Two Taenie species are known to affect man:
1- Taenia saginata (beef tapeworm)
Distributed all over the world.
Definitive host: man
Intermediate host: sheep, cattle and camels.
2- Taenia solium (pork tapeworm):
Distributed in pig raising countries
Definitive host: man
Intermediate host: pigs
15. CLINICAL PICTURE:
Abdominal pain, nausea, vomiting, colic, irregular bowel
habits, Intestinal obstruction, Loss of weight, and Loss of
vitamins.
DIAGNOSIS:
By finding the eggs or gravid segments in the stool of patient.