parasitology: (protozoa and helminthes) : protozoa: 1- protozoa are unicellular (eukaryotic) or...
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Parasitology: (Protozoa and Helminthes) :
Protozoa:1- Protozoa are unicellular (eukaryotic) or acellular organisms. 2- Protozoan is measured in microns; (size vary from 2-150 µm).
3- Cytoplasmic extension in form of pseudopodia,
flagella or cilia are responsible for locomotion.
4- Nucleus may be compact with diffuse chromatin or
vesicular
with central or eccentric karyosome (DNA).
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5- Respiration is mostly anaerobic.6- Secretion: Protozoa secrete digestive enzymes, toxins, cytolysin and antigenic substances. 7-Reproduction: may be asexual or sexual.
According to Mode of locomotion, protozoa are classified into the following groups:Class: Rhizopoda: motile (by pseudopodia).
Example: Entamoeba histolytica ; cause Amoebic dysentery.
Class: Ciliophora: motile ( by cilia).
Example: Balantidium coli ; cause Balantidial dysentery.
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Class: Mastigophora: Motile (by flagella).
A-Gastrointestinal flagellates:
Example: Giardia intestinalis : cause diarrheal illness.
B-Genitourinary flagellates:
Example: Trichomonas vaginalis : cause Urethritis.
C-Blood and Tissue flagellates:
Example: Trypanosoma gambiense:
Cause African sleeping sickness disease.
Example: Leishmania species:
Cause cutaneous infection.
Class: Sporozoa: This class has no motor organelles.
Plasmodium species, Cause Malaria.
Microscopic Morphology of protozoa:
Giardia intestinalis trophozoite:
Iron – hematoxylin stain.
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Trichomonas species: sexual transmission.
Trypanosoma in blood film: Arthropod-born infection: Sleeping sickness disease.
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Cutaneous leishmaniasis: caused by Leishmania.
Arthropod-born disease: Sand-fly.
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Plasmodium falciparum: Ring form and gametocyte : The diagnostic stage of Malaria.
The Mosquito species of the genus
Anopheles , the vector of
Plasmodium.
Helminthes:
Helminthes can be classified into the following:
1- Trematodes (flukes): are members of Platyhelminthes.
Trematoda are flattened- leaf shaped non-segmented
hermaphrodites except Schistosoma species.
Schistosoma : Schistosomes are unisexual blood flukes that have worldwide distribution.
Examples:
1- Schistosoma hematobium: It causes urinary bilharziasis.
2 - Schistosoma mansoni: It causes intestinal bilharziasis.
MORPHOLOGY:
Male:
10-20 x I mm with short anterior cylindrical pan and posterior flattened part which incurved ventrally to form the gynaecephoric canal.
It has well developed oral and
ventral suckers.
Female:
15-25 x 0.25 mm:, cylindrical.
It has ovary and uterus.
2-Cestoda:
Flattened-segmented Platyhelminthes, hermaphroditic worms (Tapeworm) with body differentiated into:
1-Scolex: carry organ of fixation( suckers ).
2-Neck
3-Segments : immature segments, mature segments with well-
developed reproductive organs, and gravid segments with uterus.
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TAENIA WORMS:
Two Taenia species are known to affect man:
1- Taenia saginata (beef tapeworm)
2- Taenia solium (pork tapeworm)
Hymenolepis diminuta: Rat Tapeworm
Distribution: worldwide Habitat: small intestine Morphology: 20-60 cm, 800-1000 segments, scolex carries a small rostellum without hooks, immature, mature and gravid segments.
Hymenolepis nana: Dwarf Tapeworm: Distribution: worldwide. Habitat: small intestine.
Morphology: 2-4 cm, 100 segments, the scolex carries a small rostellum with one row of hooks, immature, mature and gravid segments.
Hymenolepis nana: Dwarf Tapeworm:
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3- Nematoda:
Nematodes are cylindrical non-segmented unisexual worms.
Mouth may be provided with lips, papillae and teeth.
Examples:
A-Ascaris lumbricoides : Distribution: worldwide
Habitat: Free in small intestine
Morphology:
Whitish yellow cylindrical worms:
Male 15-25 cm.
Female 20 -40 cm.
with tapering posterior end.
B- Enterobius vermicularis: Pin Worm:
Distribution: worldwide
D.H: Man especially children, no intermediate host
caecum and adjacent parts of ileum and ascending colon.
Morphology: whitish cylindrical worms
Male: 2-5 mm, posterior end coiled with one spicule.
Female: 8-12 mm, posterior end is tapering like a pin.
Enterobius vermicularis: Pin Worm
D-shaped Egg (diagnostic stage)
C-Trichcephalus trichiuris: Whip worm:
Distribution: worldwide
D.H: man , no intermediate host
Habitat : large intestine( caecum).
Mode of infection: ingestion of embryonated egg.Morphology:
whitish whip like with anterior narrow part, 2/5 of the body, and
posterior broad part, 3/5 of the body.
Trichcephalus trichiuris: Whip worm: n
D-Trichinella spiralis:
Nematoda species occurring in rats, pigs, and humans (D.H).The parasite transmitted by ingestion of encysted larvae in skeletal muscles.
Transmission: ingestion of pork meat.
Diagnostic stage: The encystic larvae in skeletal muscles.