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Ch 12 The Eukaryotes: Fungi Algae Protozoa Helminths
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Student Learning Outcomes
List the defining characteristics of fungi. Identify two beneficial and two harmful effects of fungi. List the defining characteristics of protozoa. Differentiate an intermediate host from a definitive host. List the distinguishing characteristics of the two classes of parasitic helminths, and give an example of each. Provide a rationale for the elaborate life cycles of parasitic worms. Define arthropod vector. Differentiate between a tick and a mosquito, and name a disease transmitted by each.
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FUNGI Chemoheterotroph, aerobic (molds) or facultatively anaerobic (yeasts) Mycology: Study of fungi Most decomposers, few parasites of plants and animals # of serious fungal infections increasing
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Characteristics Hyphae: Cell filaments, mostly septate Mycelium: Mass of hyphae Molds: mostly filamentous Yeasts: non-filamentous, unicellular fungi Budding yeasts divide asymmetrically. Dimorphic fungi: yeast-like at 37C, mold-like at 25C. Fungal spores are reproductive spores (unlike bacterial spores). Used to differentiate fungi. Growth in acidic, low-moisture, high osmotic pressure environments.
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Economic Effects of Fungi p. 341
The good: Saccharomyces cerevisiae: Bread, wine, HBV vaccine Trichoderma: Cellulase for clear fruit juice Taxomyces: Taxol Entomophaga: Biocontrol Paecilomyces: Kills termites The bad: Mold spoilage The ugly:
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Fungal Diseases – Mycoses
p. 335 Systemic mycosis: infection deep within body, affects many tissues and organs. Histoplasmosis and coccidiomycosis. Subcutaneous mycosis: Saprophytic fungi, e.g.: Sporotrichosis. Cutaneous mycosis = Dermatomycosis: affects keratin-containing tissues (hair, nails, skin). Superficial mycosis: localized on hair shafts and superficial skin cells. Opportunistic mycoses: caused by normal microbiota or fungi that are not usually pathogenic (E.g.: Candidiasis, Pneumocystis pneumonia, et.al.) usually systemic.
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Human eyelash with unknown fungus infection.
Minimal damage to skin or underlying tissues. However, if IS impaired, can encourage infecting fungus to proliferate.
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ALGAE Mostly Photoautotrophs in Ocean
Several forms of shellfish poisoning affecting fish, sea mammals and humans Toxins are ingested and concentrated by shellfish (e.g.: mussels, oysters, clams, scallops) Both may produce potent marine toxins
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Diseases due to marine toxins
Domoic Acid Intoxication (1st reported case in Canada, 1987) Diatomes Muscles Ho Diarrhea and memory loss. Also sea lions and birds Paralytic shellfish poisoning (PSP): Dinoflagellates of genus Alexandrium produce saxitoxins Diatomes Muscles/clams Ho Red tide Ciguatera poisoning: Dinoflagellate Gambierdiscus toxicus moves up food chain to large fish
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See p. 351 PROTOZOA Unicellular, eukaryotic chemoheterotrophs. Large and diverse group. Few are pathogenic. Found in soil and water and as normal microbiota in animals. Trophozoite: Vegetative form (feeding and growing). Asexual reproduction via fission, budding, or schizogony (multiple fission). Sexual reproduction via conjugation. Some protozoa can produce a cyst that provides protection during adverse environmental conditions.
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Some Medically Important Protozoa
Giardia lamblia (G. intestinalis or G. duodenalis). In ho and mammals. Diagnosis via cysts in feces Trichomonal vaginalis
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Apicomplexa: not mobile, intracellular Plasmodium , Babesia, Toxoplasma, Cryptosporidium (Clinical Focus p.355 2 3 Plasmodium vivax Life Cycle 8 7 6 Fig 12.20
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Euglenozoa: Hemoflagellates Trypanosoma
Move by flagella Hemoflagellates Sleeping sickness Chagas’ disease
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Amoebae Move by pseudopods
Entamoeba histolytica in human GI tract. ~ 10% carriers. Amoebic disentery. Acanthamoeba in water. Can infect cornea.
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HELMINTHS (Parasitic Worm)
Kingdom: Animalia Phylum: Platyhelminthes (flatworms) Class: Trematodes (flukes) Class: Cestodes (tapeworms) Phylum: Nematoda (roundworms) few are human parasites Anatomy and life cycle modified for parasitism Adult stage in definitive host. Each larval stage in specific intermediate host.
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Life Cycle of Helminths
Monoecious (hermaphroditic) Male and female reproductive systems in one animal Dioecious Separate male and female Egg larva(e) adult
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Platyhelminths Dorsoventrally flattened
Trematode, or fluke: Leaf-shaped; suckers attaches to host tissue Cestode, or tapeworm: Scolex (head), proglottids 4 suckers and rostellum with hooks Fig 12.27 Gravid proglottid with uterine branches
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Taenia solium Taenia saginata
Human definitive host; pig or cattle intermediate host.
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Echinococcus granulosus
Fig
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Human is …. Taenia saginata Echinococcus granulosus __________ Host
Cysticerci in beef muscle ___________ Host Echinococcus granulosus Adult in dog
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Nematodes Eggs infective for humans:
Roundworms have a complete digestive system Eggs infective for humans: Enterobius vermicularis (pinworm). Most common worm infection in US (30% of children, 16% of adults infected) Ascaris lumbricoides: Ascariasis. 2nd most common worm infection in US. (Most common worldwide; > 1 bio infected)
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Pinworm / Enterobius vermicularis
Fig12.29
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ova Pinworm (Enterobius vermicularis) in sigmoid colon
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Diagnosing Pinworm Disease
Do test immediately after waking up. Several samples might need to be examined. Since scratching of the anal area is common, samples taken from under the fingernails may also contain eggs. pinworm paddle
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Ascariasis Ascaris lumbricoides Soil transmitted – how do you get it?
Often no symptoms Worldwide in warm, moist areas Heavy infections can cause intestinal blockage and impair growth in children. Coughing??
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Larvae Infective for Humans
Fig 25.23 Larva penetrate host skin to blood and lymph to lungs, caughed up, swallowed , to intestine Hookworms Necator americanus and Ancylostoma duodenale
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The Heartworm Dirofilaria immitis
Primarily in dogs and cats human heart failure, also in human lungs Spread via mosquitoes Fig 12.30
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ARTHROPODS AS VECTORS Kingdom: Animalia
Phylum: Arthropoda (exoskeleton, jointed legs, segmented body) Class: Insecta (6 legs) Lice, fleas, mosquitoes Class: Arachnida (8 legs) Mites and ticks Arthropods that carry diseases are called vectors. Elimination of vectorborne diseases best via control or eradication of vectors. Fig 12.32
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Arthropod Vectors The End Mechanical transmission
Biological transmission Microbe multiplies in vector Definitive host Microbe’s sexual reproduction in vector The End
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