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BMS171 Revision Prof. Khalifa E. Khalifa Medicine and Surgery Program Spring 2024 Introduction The association between two organisms may take one of four relations: Parasitism, Commensalism, Mutualism, Symbiosis: Parasitism: association between two organisms in which one benefits (parasite) and the other being injured (host= patient). e.g., Giardia intestinalis is a parasite that lives in the small intestine of man (host) and causing diarrhea. Commensalism: association between two organisms, in which one benefits without causing harm to the other. e.g., Entamoeba coli is a commensal that lives in the large intestine of man without causing any disease manifestations TYPES OF PARASITES According to Habitat: 1. Ectoparasites: live on the surface of their hosts (infestation). 2. Endoparasites: live inside the body of their hosts (small intestine, large intestine, etc.). According to the Number of Hosts: : 3. Monoxenous: (direct life cycle): needs only one host for the completion of life cycle as Ascaris lumbricoides and Trichuris trichiura 4. Heteroxenous: (indirect life cycle): the life cycle is completed in two (diheteroxenous), or more than two (polyxenous) as Fasciola and Heterophyes heterophyes According to association with hosts 5. Obligatory: can't survive outside their hosts, i.e., completely dependent on their hosts for feeding. 6. Facultative: capable of free living outside their host if the conditions is favorable and hide inside the host under unfavorable conditions (change lifestyle between free-living and parasitic) as Strongyloides stercoralis. 7. Temporary: visit the hosts from time to time for meal, as mosquitoes 8. Permanent: always fixed to their hosts, as lice. 9. Accidental: affect unusual hosts. 10.Opportunistic: capable of producing severe disease in immuno-compromised host as Cryptosporidium hominis. TYPES OF HOSTS 1. Final or definitive host (DH): harbors the adult stages or sexually reproducing forms of the parasite. (in which parasite reach maturity). 2. Intermediate host (IH): harbors the larval stages or asexually reproducing forms. 3. Reservoir host (RH): harbors the same species and stages as human. It maintains the life cycle of the parasites in nature and acts a source of re-passing infection to man. 4. Vector: an arthropod that transmits parasites from one host to another. Methods of diagnosis of parasitic infections: a) Clinical: clinical picture (symptoms and signs) b) Laboratory: including direct and indirect techniques: Direct (Parasitological): finding diagnostic stage(s) (egg, larva, trophozoites, cyst, etc.). Indirect (Immunological): detection of antibodies and antigens in blood samples by different tests as: ▪ Enzyme linked immunosorbent assay (ELISA). ▪ Indirect hemagglutinations assay (IHA). ▪ Immunochromatographic technique (ICT). Molecular: detection of parasites’ genes by PCR. c) Imaging techniques: X-ray, CT, and sonography. Methods of diagnosis of parasitic infections: Clinical Laboratory Imaging Symptoms Direct Endoscopy Indirect X-ray, CT Signs Molecular Sonography MRI Parasite Nomenclature Kingdom: Animalia Subkingdom: Phylum: Platyhelminthes Class: Cestoda Order: Cyclophyllidea Family: Taeniidae Genus: Taenia (italic, initial capital letter) Species: saginata (italic, initial small letter) solium Helminthology (Multicellular Worms) GIT, Blood, Urogenital, Respiratory Modules Protozoology (unicellular) GIT, Blood, Urogenital, CNS Modules Entomology (Arthropods) Musculoskeletal and Skin, Blood, Resp. Modules Direct and Indirect Life Cycles Parasite life cycle is the pathway of development starting by one stage and ending in it. 1. Direct Life Cycle: the life cycle is completed in one host (monoxenous parasites) 2. Indirect Life Cycle: the life cycle is completed in more than one host (heteroxenous parasites) Direct Life Cycle (Monoxenous parasites) Indirect Life Cycle (Heteroxenous parasites Fish is 2nd IH Dogs and cats are Man is RH DH Snail is 1st IH Main Components of Life Cycle 1. Habitat: The special organ or tissue in which the parasite finally reside. E.g., GIT, urogenital, respiratory, blood and lymphatics, musculoskeletal and skin, CNS. 2. Hosts: (DH, IH, RH) 3. Infective stage: Egg, Larva, Trophozoite, Cyst, Oocyst 4. Mode of Infection: Ingestion, inhalation, blood transfusion, sexual intercourse, insect bite, penetration of the skin, etc. 5. Diagnostic Stage: Egg, Larva, Trophozoite, Cyst, Oocyst 6. Source of Infection: Another person, food (vegetables, meat, fish), water, air, soil, self infection (Autoinfection) 7. Route of infection (Entry): oral, skin, parenteral 8. Route of Exit: Stool, urine, sputum, taken by insect, etc. Importance of Study the Life Cycle 1. Prediction of clinical manifestations from habitat 2. Diagnosis of infection and proper selection and timing of diagnostic samples 3. Design control and prevention strategies from mode of infection and hosts needed for completion of the life cycle Transmission of Parasitic Infection 1. Oral transmission (Foodborne): Improperly cooked meat Improperly cooked fish Improperly washed fruits and vegetables 2. Skin penetration Active penetration Skin contact 3. Autoinfection: self infection or reinfection: May be external or internal Transmission of Parasitic Infection (cont.) 4. Congenital (transplacental): 5. Sexual transmission 6. Blood transfusion and organ transplantation 7. Inhalation followed by swallowing 8. Vector transmission Biological: part of the life cycle occurs in the vector. Arthropod are specialized in transmission Mechanical: by inoculation of contamination Effect of Parasites On Host Systemic Local Systemic Effects ▪ Fever (proinflammatory cytokines as IL-1, IL-6, TNF-α) ▪ Anemia ▪ Eosinophilia: especially in helminthic infections (Type 2 immune response, increased IL-4, IL-5, increase in mast cells) ▪ Malnutrition ▪ Allergy and Anaphylaxis (Type 1 hypersensitivity reaction) ▪ Autoimmune disorders (Type 2 hypersensitivity reaction) ▪ Immune complex deposition (Type 3 hypersensitivity reaction) ▪ Impaired response to bacterial, viral infections and vaccination ▪ Immunomodulation by helminths (Increased IL-10 and TGF- β, T-regs cells) Local Effects ▪ Disturbed physiological processes (Diarrhea, defective digestion and absorption, increased liver enzymes) ▪ Tissue destruction ▪ Space occupying lesions and pressure symptoms ▪ Chronic inflammation, granuloma formation and fibrosis ▪ Hypertrophy, hyperplasia (hepatosplenomegaly, lymphadenopathy) ▪ Malignant transformation (Cancer bladder in Schist. haematobium) ▪ Obstruction (intestine, bile duct, pancreatic duct, lymphatics) ▪ Skin nodules, ulceration, dermatitis, eczema ▪ Destruction of RBCs and anemia Helminths Character Trematoda Cestoda Nematoda Shape Leaf-like, Tape-like, Cylindrical, Unsegmented segmented unsegmented Sex Hermaphrodites, Hermaphrodites Separate (unisexual) except Schistosomes Suckers Present Present Absent Body cavity Absent Absent Present Alimentary Present, incomplete Absent Present, complete canal without anus with anus Life cycle Heteroxenous Heteroxenous Heteroxenous or monoxenous TREMATODA General characters of trematodes Body is flattened unsegmented, except female schistosomes (cylindrical). No body cavity, organs are embedded in connective tissue. Digestive system is simple, no anus. Nutrients are taken from the surroundings; remnants of food are vomited through mouth Organs of fixation in the form of suckers (oral, ventral). A 3rd sucker, genital, may be present. Hermaphrodites (monoecious) except schistosomes unisexual (diecious). All trematodes need a snail intermediate host, so part of the life cycle occurs in water. Life Cycle of Trematodes Trematodes are heteroxenous Fish is parasites, they 2nd IH need at least 2 hosts for completion of the Man is life cycle (indirect Snail is DH life cycle). Part of 1st IH the life cycle occurs in water as they need a snail intermediate host Developmental stages of trematodes Egg All eggs are operculated except those of Schistosomes Miracidium Sporocyst Absent in Schistosomes Redia Cercaria is formed of a body and a tail, the latter may Cercaria be simple (leptocercus cercaria), surrounded by a membrane (lophocercus) or forked (furcocercus). Types of Cercaria Leptocercus cercaria: with Simple tail Lophocercus cercaria: tail is surrounded by a membrane Furcocercus cercaria: with forked tail Microcercus cercaria): tail is a a knob like structure Encysted metacercaria When cercariae come out of the snail to water where they may become encysted on vegetation to be ingested by the D.H., penetrate the second I.H. (fish and crabs) to encyst in muscles. Juvenile Fluke This is known as metacercaria. It is the infective stage of all trematodes except Schistosomes LIVER FLUKES Fasciola gigantica (Giant liver fluke) Fasciola hepatica (Sheep liver fluke) Life Cycle of Mode of Fasciola spp. infection IH DH DH: ------------------------ Man RH:------------------------- Sheep and cattle, herbivores (Zoonotic) IH:-------------------------- Snail Habitat:------------------- Biliary tract Larval stages :----------- Egg, miracidium, sporocyst , redia, cercaria , metacercaria Infective stage :-------- Encysted metacercaria Ingestion of improperly washed vegetables contaminated Mode of infection: ---- with encysted metacercaria Diagnostic stage : ----- Immature-Operculated Blood FLUKES Schistosoma mansoni Schistosoma haematbium Schistosoma japonicum Morphology Male: 6 -15 mm x 1mm with an anterior cylindrical part, and a post. flattened part that incurved ventrally to form the gynaecophoric canal for holding female during copulation. Has well developed oral and ventral suckers. Testes 4-8, cuticle is smooth or covered with tubercles Female: 14- 20 mm x 0.15-0.25 mm, cylindrical Smooth surface, ill developed suckers One ovary present in front of the union of the intestinal caeca Life Cycle of Schistosoma spp. DH: ------------------------ Man IH:-------------------------- Snail Habitat:------------------- Mesenetric and vesical venous plexus Larval stages :----------- Egg, miracidium, sporocyst , daughter sporocoyst, cercaria Infective stage :-------- Furcocercus cercaria Mode of infection: ---- Penetration of the skin by furcocercus cercaria while wadding in water Diagnostic stage : ----- Mature-Spinated Schistosoma Eggs (diagnostic stage) Size: 120-140 x 50 Size: 150 x 60 µm. µm. Shape: oval Shape: oval Shell: Thin Shell: Thin Color: yellow Color: Colorless Content: Mature with Content: Mature with fully formed miracidium fully formed Character: lateral miracidium spine Character: terminal Pass in stool, rarely in spine urine Pass in urine, rarely in stool Terminal spine Lateral spine Furcocercus cercaria (infective stage) Fasciola gigantica Schistosoma mansoni Fasciola hepatica Schistosoma haematobium Morphology Leaf like, unsegmented, Fasciola Sex separate, male 6-15 x 1 mm with well developed oral gigantica (2-8 cm), Fasciola hepatica (2- and ventral sucker and a gynaecophoric canal, cuticle may 3 cm) be smooth or tuberculated. Female is cylindrical, 15-20 X 0.25 mm, smooth, weak suckers Digestive system With pharynx, intestinal caeca are No pharynx, simple intestinal caeca that reunite after branched bifurcation to form single tube Genital system 2 branched testes in front of each other, Testes, 4-8, rounded or oval behind ventral sucker, on ovary one branched ovary. Genital pore in front in front of union of intest. Caeca. Genital pore behind ventral of ventral sucker. Vit. gland lateral field sucker. Vit. Glands behind union of caeca. Habitat Biliary passage (liver fluke) Mesenteric and vesical venous plexus (Blood fluke) DH Man, and herbivores Man IH Snail: Lymnaea spp Snail (Biomphalaria alexandrina, Bulinus truncatus) Infective stage Encysted metacercaria Furcocercus cercaria Mode of infection Eating improperly washed vegetables Piercing of skin by furcocercus cercaria while swimming in infected water Diagnostic stage Operculated eggs Spinated eggs Developmental stages Egg, miracidium, sporocyst, redia, Egg, miracidium, sporocyst, furcocercus cercaria, leptocercus cercaria, encysted met. (No redia) Prevention and Control TTT of patients + avoid eating improperly Mass TTT of patients, snail control, avoid swimming in washed vegetables + Snail control infected water, avoid defecation and urination in water CESTODA General Characters of Cestodes Flattened dorsoventerally, segmented ribbon-like (Tapeworms) Size varies from few millimeters to several meters No Body Cavity No alimentary canal (No digestive system) Genital System: hermaphrodites Excretory system: flame cells that drain into collecting tubes then into the ventral and dorsal longitudinal excretory canal Body is formed of scolex, neck and Strobila (Segments or proglottids) General Characters of Cestodes Scolex (head): Carrying the organs of fixation in the form of suckers or bothria with or without a rostellum that may carry hooks Neck: The actively dividing portion of the worm. Strobila: consists of: ▪ Immature segments: where sex organs are still immature. ▪ Mature segments: contain mature female and male sex organs ▪ Gravid segments: contain the gravid uterus General Characters of Cestodes Classification of Cestodes Organ of Fixation Bothria Suckers Order Pseudophyllidea Cyclophyllidea Suckers Bothria Pseudophyllidea Cyclophyllidea Scolex Elongated Globular Organ of fixation Bothria Suckers and hooks Mature segment - Genital pore Ventral Lateral - Uterus Open Blind - Vitellaria Scattered Single mass - Gravid segment Absent Present Eggs Operculated, immature, need No-operculated, mature, don’t water for develop. need water Intermediate hosts Two one Larva stage Solid (Procercoid and Cystic (Cysticercus, Cysticercoid) Plerocercoid) Members Diphyllobothrium latum Taenia saginata, T. solium Diphyllobothrium mansoni Hymenolepis nana Hymenolepis diminuta Dipylidium caninum Developmental stages of Pseudophyllidea Egg Coracidium Procercoid Plerocercoid 70 x 50 µm, oval, Spherical 6- Solid, elongated, Solid, elongated, 1-2 thick shell, hooked embryo 0.5 mm, with a cm with invaginated yellowish brown (Onchosphere) spherical caudal anterior end, body is Immature, enclosed in a end containing 6 striated but not operculated ciliated hooks segmented embryophore Larvae of Pseudophyllidea are solid in structure Developmental stages of Cyclophyllidea Larva Egg Cysticercus Hydatid Cyst Cysticercoid Size: 30-40 µm. 10-15 mm, cystic Few cm in diameter, wall Few mm. The cysticercoid Shape: spherical bladder like swelling is formed of three layers. consists of a tailed cyst Shell: Thick, radially with invaginated scolex Contains hydatid fluid enclosing the neck and striated scolex of the cestode. Present in tissues of IH The outer limiting layer Color: Yellowish brown surrounds the surface of Content: Mature the cyst, neck and hexacanth embryo scolex. Pass with the stool of DH Larval stages of Cyclophyllidea Solid tail Cysticercus Hydatid Cyst Cysticercoid Larvae of Cyclophyllidea are either cystic or partly cystic and partly solid How Cestodes Affect the Health of Man? Man acts as DH Man acts as IH - Carries adult worm in small - Carries larva in tissues (liver, intestine lung, brain, bones, etc.) - Acquires infection by ingestion of larva (T. solium, T. saginata) and - Acquires infection by ingestion eggs in Hymenolepis spp, D. of eggs caninum - Clinical manifestation in the - Clinical manifestation in the form of form of pressure symptoms diarrhea, abdominal pain, vomiting, indigestion, avitaminosis, etc. depending on the site - Diagnosis is by detection of eggs - Diagnosis depends on the and/or gravid segments in stool detection of antibodies - Examples: Taenia saginata, Taenia - Examples: Taenia solium solium & Hymenolepis spp, D. caninum (Cysticercosis) and Sparganosis Pseudophyllidea Diphyllobothrium latum “Fish Tapeworm” Diphyllobothriasis Distribution: Finland, Siberia, Lake regions of Europe, Japan, Chile, America. It is not present in Egypt Habitat: Small intestine DH: Man IH: It requires two IH 1st: Cyclops (water flea), 2nd: Fresh water salmon and cyprinoid fish. RH: Fish eating animals (dogs, cats, foxes). Larval Stages: Egg---Coracidium----Procercoid-----Plerocercoid Life Cycle of Diphyllobothrium latum Mode of infection Infective stage: Plerocercoid in fish muscles. Mode of infection: DH ingestion of the IH plerocercoid in insufficiently cooked, pickled or smoked fish. Cyclophyllidea Echinococcus grnaulosus “Hydatid worm” Hydatid disease Echinococcus granulosus (Disease: Cystic echinococcosis) Distribution: worldwide, it is common in sheep-raising areas in North Africa and Middle East, S. America, Central Europe. They are found in rural grazing areas where dogs (or other canids) ingest organs from infected animals Habitat: Small intestine of dogs DH: Dogs and other canines IH: Sheep, camels, cattle, man (accidental host) Larval stages: Egg-------Hydatid cyst Life Cycle Infective stage: Egg Mode of infection: Eating food contaminated by excreta of dogs Diphyllobothrium latum Echinococcus granulosus Morphology Flattened segmented, 3-10 meter, 3000 Flattened segmented, 3-8 mm, 3-4 segments, scolex segments, scolex elongated with 2 globular with 4 cup-shaped suckers and a rostellum with 2 bothria, mature segments broader than rows of hooks, immature, mature and gravid segments are long. No gravid segments longer than broad Digestive system Absent Absent Genital system Testes multiple scattered, one bilobed Testes multiple scattered, one bilobed ovary, compact vit. ovary , scattered vit. glands, genital pore glands, genital pore on lateral surface. Uterus is blind. There on ventral surface. Uterus opens in is a gravid segment full of a uterus with lateral pouches genital pore no gravid segment Habitat Small intestine of man Small intestine of dogs DH Man, and fish-eating animals Dogs and other canines as wolves and foxes IH 1st cyclops, 2nd : cyprinoid fish Sheep, cattle, camels, man (accidental) Infective stage Plerocercoid in fish muscles Eggs in dog’s feces Mode of infection Eating improperly cooked, salted or Eating food or drinking water contaminated by feces of dogs pickled fish Diagnostic stage Operculated eggs Hydatid sands and protoscolices Developmental stages Egg, coracidium, procercoid, Egg, hydatid cyst plerocercoid Prevention and Control TTT of patients + avoid eating improperly TTT of patients, dogs should be prevented from entry SH cooked fish + freezing of fish. Avoid and avoid feeding on remains of animals + deworming of defecation in water dogs Diphyllobothrium latum Fasciola gigantica Fasciola hepatica Morphology Flattened segmented, 3-10 meter, 3000 Leaf like, unsegmented, Fasciola gigantica (2-8 cm), segments, scolex elongated with 2 bothria, Fasciola hepatica (2-3 cm) mature segments broader than long. No gravid segments Digestive system Absent With mouth opening, intestinal caeca are branched, no anus Genital system Testes multiple scattered follicles, one 2 branched testes in front of each other, one branched bilobed ovary , scattered vit. glands, genital ovary. Genital pore in front of ventral sucker. Vit. gland pore on ventral surface. Uterus opens in lateral field genital pore no gravid segment Habitat Small intestine of man Biliary passage (liver fluke) DH Man, and fish-eating animals Man, and herbivores IH 1st cyclops, 2nd : cyprinoid fish Snail: Lymnaea spp Infective stage Plerocercoid in fish muscles Encysted metacercaria on water plants Mode of infection Eating improperly cooked, or pickled fish Eating improperly washed vegetables Diagnostic stage Operculated eggs Operculated eggs Developmental stages Egg, coracidium, procercoid, plerocercoid Egg, miracidium, sporocyst, redia, leptocercus cercaria, encysted met. Prevention and Control TTT of patients + avoid eating improperly TTT of patients + avoid eating improperly washed cooked fish +. Avoid defecation in water vegetables + Snail control NEMATODA General Characters of Nematodes ▪ Bilaterally symmetrical, elongate, un-segmented, cylindrical worms ▪ Separate sex, males are smaller than females. Female is larger and broader than male. The post. end of female is straight while that of male is curved ventrally or expanded. ▪ Has a body cavity containing fluid within which lies the digestive and reproductive system. ▪ Body wall is formed of three layers; cuticle, hypodermis and muscle layer ▪ Digestive system: is a simple patent tube extending from oral opening, followed by oral cavity, esophagus and intestine. The latter opens posteriorly in a separate anus in female and joins genital duct to open in the cloaca in male. General Characters of Nematodes Reproductive system: Male system is a single coiled tube differentiated into testis, vas deferens, seminal vesicle, ejaculatory duct which opens in cloaca. Female system is a single or double, formed of coiled tube (s), each is differentiated into an ovary, oviduct, seminal receptacle and uterus. The 2 uteri (parallel or divergent) join to form the vagina which opens through the vulva either in the middle or anterior parts of the body. Development of nematodes: Fertilized Female Egg Larva (4 stages) Adults 1st and 2nd larval stages are called rhabditiform larvae (with rhabditiform esophagus) while 3rd and 4th larval stages are called filariform larvae (with filariform esophagus). Life Cycle: Life cycle may be completed in one host (direct) or in more than one host (indirect). The eggs, larvae and adult worms are the important morphological forms seen during development. Females may lay eggs (Oviparous), or Larvae (Viviparous) or eggs containing larvae (ovoviviparous) There are 4 larval stages; the first and the second have rhabditiform esophagus i.e., rhabditiform larvae, the third and the fourth have filariform esophagus i.e., filariform larvae Ascaris lumbricoides (Giant Intestinal Roundworm) Distribution: Worldwide. Habitat: Small intestine of man free in the lumen. DH: Man. (No IH direct life cycle) Morphology: – Cylindrical long worms, pinkish in colour with small mouth surrounded by three lips. The oesophagus is muscular and club shaped. – Male: 15-25 x 0.4 cm, with the posterior end curved ventrally carrying two copulatory spicules. – Female: 20-40 x 0.5 cm, tapering posteriorly with vulva at the junction between anterior and middle thirds. (lays around 200,000 eggs/day) Life cycle Infective stage: Embryonated egg with second stage rhabditiform larva. Mode of infection: Ingestion of infective egg Enterobius vermicularis (Oxyuris, Pinworm) Disease: Enterobiasis Distribution: Worldwide, commonest nematode affecting man. Habitat: Large intestine; caecum, appendix, adjacent part of ileum and ascending colon. Free in the lumen or loosely attached to the mucosa. DH: Man, especially children. Morphology: – Male: 2-5 mm, posterior 1/3 curved ventrally and carries a single spicule. – Female: 8-13 mm, posterior 1/3 tapering with pointed tail hence the name pinworm. Life cycle Infective stage: Mature egg (egg containing larva) Mode of infection: Autoinfection. Ingestion of eggs with contaminated food or drink. Inhalation of eggs liberated into the air when sheets, clothing, etc Re-entrance of larvae that sometimes hatch from eggs on the peri-anal skin to the large intestine (retro- infection). Ascaris lumbricoides Enterobius vermicularis (Pinworm=Oxyuris) Giant intestinal round worm Morphology Cylindrical, creamy white with club-shaped Cylindrical, male 2-5 mm, posterior 1/3 curved ventrally esoph. Male 15-25 cm posterior end curved with single spicule. Female 8-13 mm, posterior 1/3 with 2 spicules. Female 20-24 cm posterior tapering like a pin end straight. Female lays 200000 eggs/day Habitat Small intestine free Large intestine: Caecum, ascending colon, adjacent part Life cycle (There lung phase, so there are of ileum, appendix pulmonary symptoms) No cycle lung, there is no pulmonary symptoms DH Man Man IH No, monoxenous No, monoxenous Infective stage Embryonated egg containing 2nd stage Larvated egg rhabditiform larva (present in soil not in There is auto infection because egg laid mature stool) No autoinfection Mode of infection Eating improperly washed vegetables Autoinfection, ingestion of eggs, inhalation of eggs, retro- containing embryonated eggs infection Diagnostic stage Eggs Perianal swabbing for eggs. Adult my appear in stool Symptoms Pulmonary-Intestinal Itching in perianal area especially at night Prevention and Control TTT of patients + avoid eating improperly TTT of patients (all family members should be treated washed vegetables + Safe water supply and + Personal hygiene (cutting fingernails, frequent hand proper sewage disposal, avoid using human washing + Boiling of bedlinens feces as fertilized PROTOZOA General Characters of Protozoa Unicellular eukaryotic organisms: capable of performing all the vital functions of life as metazoan cells. Size: vary form 1-150 µ. Structure: nucleus responsible for reproductive function and cytoplasm responsible for all other vegetative functions. The nucleus may be one or more, vesicular (chromatin is differentiated into peripheral chromatin and endosome) or compact. Most protozoa have an outer membrane called pellicle, the periplast, giving them definite shape. In some protozoa as amoebae, the cytoplasm is differentiated an outer hyaline layer known as ectoplasm and inner granular layer known as ectoplasm General Characters of Protozoa Nutrition: is either by diffusion through the body surface or by active contribution of pseudopodia, flagella and cilia. Respiration: mostly anaerobic. Excretion: is either by diffusion through the body surface or the waste products are collected in excretory vacuoles that discharge their content to the external environment. Secretion: protozoa secrete digestive enzymes, toxins, cytolysins and antigenic substances. Encystation: some protozoa may be found in an active motile feeding reproducing vegetative form (trophozoites) or in an inactive cyst form with resistant cyst wall. The trophozoites store food, stop movement and secrete resistant cyst wall. When the conditions become favorable excystation takes place. General Characters of Protozoa Reproduction (may be asexual or sexual) 1. Asexual: a) Simple binary: There is division of the nucleus into two segments followed by division of the cytoplasm as in amoebae, ciliates and flagellates. b) Multiple fission (Schizogony): There is division of the nucleus into multiple segments followed by division of the cytoplasm as in Plasmodia. c) Endodyogeny and Endopolygony are types of asexual reproduction in which, respectively, there is formation of two or more daughter cells within their mother cell membranes consuming the cytoplasm of the mother cells, e.g. Toxoplasma. 2. Sexual: a) Conjugation: where two organisms fuse together and exchange nuclear matter as in Balantidium coli. b) Gametogony: where there is formation of male and female gametocyte that fuse together to form zygote as in sporozoa. Class Organ of locomotion Sarcodina Pseudopodia: extension of the ectoplasm followed by extension of the “Rhizopoda” endoplasm at any point on the surface, e.g. Amoebae. Mastigophora Flagella: thread-like cytoplasmic extension that arise in the endoplasm from a Kinetoblast, e.g., Giardia, Trichomonas, Leishmania, and Trypanosoma. Ciliophora Cilia: hair-like threads that cover the whole surface, they arise from basal granules, just below the cell surface, e.g., Balantidium coli Apicomplexa No apparent motor organelles: but they move by gliding and twisting, by (Sporozoa) means of contractile microtubules, e.g., Plasmodium, Toxoplasma, and Cryptosporidium. Sarcodina Amoebae Entamoeba histolytica “Amoebiasis” Entamoeba histolytica Disease: Amoebiasis Distribution: Tropics and subtropics and temperate zones. Habitat: Large intestine, especially caecum and sigmoid colon. DH: Man. Morphology: 1. Trophozoite: 12-60 µm (average 30 µm), irregular with pseudopodia, actively progressive. Commensal lumen forms (minuta form) feed on bacteria and food debris, while tissue forms (magna form) feed on RBCs 2. Precyst: Rounded or oval, 10-20 µm, non-feeding, there are no RBCs 3. Cyst: Rounded with well developed cyst wall, 12-15 µ, it contains 1-4 nuclei, glycogen and chromatoid bodies Life cycle Infective stage: mature quadri- nucleate cyst. Mode of infection: ingestion of cysts in contaminated food or drinks or on contaminated hands (autoinfection). Cockroaches and House flies play an important role in transmission. Mastigophora Haemoflagellates Leishmania spp. “Leishmaniasis” General Characters of hemoflagellates: Live in the blood and tissue of man or reservoir hosts. Need a vector for transmission (heteroxenous) Locomotion is by a single flagellum that arises from a kinetoplast (blepharoblast and parabasal body). Multiplication is by longitudinal binary fission, with division of the kinetoplast followed by division of the nucleus and cytoplasm. Hemoflagellates include Leishmania and Trypanosoma spp. Hemoflagellates flagellates exist in two or more out of four forms Leishmania donovani complex (Visceral Leishmaniasis) Distribution: India , Mediterranean Coast, China Central Africa, South America. Disease: Visceral leishmaniasis, kala-azar Habitat: Macrophage-phagocyte system in all viscera (blood, spleen, liver, bone marrow, lymph node, skin, etc.). DH: Man. RH: Dogs and rodents in certain areas. Vector: Female sand fly of the genus Phlebotomus (in Old world) and genus Lutzomyia (in New world) Morphologic forms of Leishmania Morphology: Amastigote: in tissues of man and reservoir host. Promastigote: in insect and culture. Infective stage: Promastigotes. Mode of infection: - Bite of infected female sand fly of the genus Phlebotomus or Lutzomyia. - Rarely congenital and blood transfusion Mode of transmission: cyclopropagative, i.e. increase in number and change in morphology. (2-3 weeks in vector) Entamoeba histolytica Leishmania donovani Morphology Trophozoite (Tissue form, lumen form) Amastigotes in tissue of man and reservoir hosts Precyst Promastigote in sand fly vector and culture Cyst Habitat Large intestine, Caecum, sigmoid Macrophage-Phagocytic system in tissues and viscera colon DH Man Man (RH dogs and rodents) Vector No Female Sand fly Locomotion Pseudopodia Flagella Type of life cycle Monoxenous Heteroxenous Infective stage Quadri-nucleate cyst (containing 4 Promastigotes nuclei) Mode of infection Faeco-oral via ingestion of food or Bite of infected female sand fly drinks contaminated by huaman feces Diagnostic stage Trophozoites and cysts Amastigotes in specimens from tissue and promastigotes after culture for 2-3 weeks on NNN media at 21°C Prevention and TTT of patients + Food hygiene + TTT of patients + Vector control + eradication of Control Personal hygiene infected reservoir hosts (dogs and rodents) ARTHROPODS General Characters of Arthropods Bilaterally symmetrical. Body is segmented. Have paired articulated appendages (legs, antenna). Body is covered by chitinous exoskeleton. Have a body cavity (haemocoele) with haemolymph (blood) in which the internal organs float. Metamorphosis (Development): Complete (Holometabolous) Incomplete (Hemimetabolous) immature stages differ morphologically from immature stages are morphologically similar to adults. adults. Classification Class Insecta Arachnida Crustacea Body Composed of head, Composed of Cephalothorax and thorax and abdomen abdomen Antenna 1 pair Absent 2 pairs Legs 3 pairs (Hexapoda) 4 pairs (Octapoda) 4-5 pairs Wings Absent, one or two Absent Absent pairs Example Mosquitoes, flies, Ticks, mites, Cyclops bugs, lice, fleas scorpions, spiders :  Causing a disease  Vector transmitting a disease(s) Causing a disease  Entomophobia  Dermatitis and allergic skin manifestations  Envenomization (poisons inoculation)  Myiasis  Scabies Vector transmitting diseases Modes of Transmission  Mechanical transmission The arthropod is passive carrier  Biological transmission The arthropod is an obligatory vector, forming an integral part of the life cycle of the pathogen Types of Mechanical Transmission : 1. Direct (by inoculation= syringe-like): The arthropod bites an infected person, picks up the organisms and inoculates it into another healthy person, e.g., Stomoxys (Stable fly) transmits trypanosomes. 2. Indirect (by contamination): The arthropod carries the organisms passively on its body, mouth parts and hairs and transmits them to human's food or wounds, e.g., Musca (housefly) transmits bacteria, viruses, helminthic eggs and protozoal cysts. Types of Biological Transmission: 1. Propagative: Organisms multiply inside the vector, e.g., yellow fever virus inside Aedes mosquitoes and plague bacilli inside flea 2. Cyclopropagative: Organisms multiply and undergo developmental changes inside the vector, e.g., Plasmodium spp. inside female Anopheles and hemoflagellates inside their vectors. Types of Biological Transmission: 3. Cyclodevelopmental: Organisms undergo developmental changes without multiplication inside the vector, e.g., microfilariae of Wuchereria bancrofti, Onchocerca volvulus and Loa loa inside Culex, Simulium and Chryspos, respectively. 4. Transovarian: The organisms are transmitted from infected mother arthropod to offspring through eggs, e.g., Tick borne diseases. Ways of transmission: 1. By inoculation of organisms with saliva while taking a blood meal 2. Faecal contamination of wounds: 3. By crushing of infected arthropod on human skin 4. By ingestion of infected arthropod 5. By rubbing of contaminated finger against conjunctiva and mucous membrane 6. By inhalation of air borne infected faeces Control 1. Physical: as wire screening, plastering of cracks, changing environmental conditions to be un-suitable for breeding of the arthropods 2. Chemical: Insecticides, repellants 3. Biological: use insects’ enemies 4. Genetic: to produce sterile male Class: Insecta Order: Diptera Mosquitoes Adult: 4-10 mm; body is formed of head, thorax and abdomen Head carries a pair compound eyes, 15 segmented antennae with dense hairs in male (plumose antenna) and few hairs in female (pilose antenna) adults, and 4-segmeted maxillary palps (Mx. P). Thorax is formed of 3 segments; prothorax, mesothorax and metathorax. Each segment carries a pair of legs. Mesothorax carries a pair of wings. Abdomen is 10 segments, the last 2 are modified into male (claspers) and female (cerci) Adult Mosquitoes (Culex and Anopheles spp.) Distribution: Worldwide, being more common in warm and temperate countries but can be found in cold countries, too. Life Cycle: Complete metamorphosis (Egg----Larva----Pupa----Adult) Bionomics: Male is vegetarian, female is blood sucker. Male dies after copulation, female live for 6-8 weeks under suitable env. conditions. In winter they may undergo hibernation. Egg, larva and pupa are aquatic stages. Pupa is non-feeding. Some mosquitoes prefer animal blood (Zoophilic), while other prefer human blood (anthropophilic). Culex spp. have annoying hum while Anopheles spp. have silent have. Culex and Anopheles spp. are in- and outdoors feeders, they bite mostly at night. They breed in water pools, swamps, rice field, or on any collections of water containing inorganic matters. Important Egyptian mosquitoes include: Culex pipiens, A. pharoensis, A. sergenti, A. multicolor. Mosquitoes (Culex and Anopheles spp.) Medical Importance: Causing a disease: dermatitis due to mosquitoes’ bite Vector: Culex are the vector of bancroftian filariasis, Rift valley fever, & viral encephalitis while Anopheles spp. are the vector of malaria and Malayan filariasis. Control: - Aquatic stages: Elimination of breeding places and use of insecticides. Pupa is non feeder; it is not killed by stomach poison insecticides as Paris green. Use of Biological enemies as Gambusia fish. Microbial insecticides as Bacillus thuringiensis -Adult stages: Wire screening, bed nets, and light traps. Use of repellants and insecticides as DDT and Gammexane, Organophosphorus as Malathione, Carbamates as Sevin and Baygon. Sterilization of males so females are not fertilized. Genetic control to breed infertile females. THANK YOU

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