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).
n 5- Respiration is mostly anaerobic. 6- Secretion: Protozoa secrete digestive enzymes, toxins, cytolysinand 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: Entamoebahistolytica; cause Amoebic dysentery. Class: Ciliophora:motile ( by cilia). Example: Balantidiumcoli ; cause Balantidial dysentery.
a 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:Trypanosomagambiense: Cause African sleeping sickness disease. Example:Leishmania species: Causecutaneous infection. Class: Sporozoa: This class has no motor organelles. Plasmodium species, Cause Malaria.
Microscopic Morphology of protozoa: Giardia intestinalis trophozoite: Iron – hematoxylin stain.
a Trichomonas species: sexual transmission. Trypanosoma in blood film: Arthropod-born infection: Sleeping sickness disease.
a Cutaneous leishmaniasis: caused by Leishmania. Arthropod-born disease: Sand-fly.
a 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 exceptSchistosoma species. Schistosoma : Schistosomes are unisexual blood flukes that have worldwide distribution. Examples: 1- Schistosomahematobium: It causes urinary bilharziasis. 2 - Schistosoma mansoni: It causes intestinal bilharziasis.
MORPHOLOGY: Male: 10-20 x I mm with short anterior cylindrical pan and posteriorflattened part which incurved ventrally to form the gynaecephoriccanal. 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.
a TAENIA WORMS: Two Taenia species are known to affect man: 1-Taeniasaginata (beef tapeworm) 2-Taeniasolium (pork tapeworm)
Hymenolepis diminuta: Rat Tapeworm Distribution: worldwide Habitat: small intestine Morphology: 20-60 cm, 800-1000segments, 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.
3- Nematoda: Nematodes are cylindrical non-segmented unisexual worms. Mouth may be provided with lips, papillae and teeth. Examples: A-Ascarislumbricoides: Distribution: worldwide Habitat: Free in small intestine Morphology: Whitish yellow cylindrical worms: Male15-25 cm. Female20 -40 cm. with tapering posterior end.
B- Enterobius vermicularis: Pin Worm: Distribution: worldwide D.H:Man especially children, no intermediate host caecumand 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-Trichcephalustrichiuris: 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.
D-Trichinellaspiralis: 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.