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.