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.