Post on 30-Dec-2015
Ch 12The
Eukaryotes: FungiAlgae
Protozoa Helminths
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.
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
Characteristics
Hyphae: Cell filaments, mostly septate
Mycelium: Mass of hyphaeMolds: mostly filamentousYeasts: non-filamentous,
unicellular fungiBudding 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.
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:
Fungal Diseases – Mycoses
1. Systemic mycosis: infection deep within body, affects many tissues and organs. Histoplasmosis and coccidiomycosis.
2. Subcutaneous mycosis: Saprophytic fungi, e.g.: Sporotrichosis.
3. Cutaneous mycosis = Dermatomycosis: affects keratin-containing tissues (hair, nails, skin).
4. 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.
p. 335
Human eyelash with unknown fungus infection.
Minimal damage to skin or underlying tissues.
However, if IS impaired, can encourage infecting fungus to proliferate.
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)
p. 343/44
Both may produce potent marine
toxins
Diseases due to marine toxins Domoic Acid Intoxication (1st reported case in
Canada, 1987) Diatomes Muscles HoDiarrhea and memory loss. Also sea lions and birds
Paralytic shellfish poisoning (PSP): Dinoflagellates of genus Alexandrium produce
saxitoxins Diatomes Muscles/clams Ho
Ciguatera poisoning: Dinoflagellate Gambierdiscus toxicus moves up food chain to large fish
Red tide
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.
See p. 351
Some Medically Important Protozoa Giardia lamblia (G. intestinalis or G. duodenalis). In
ho and mammals. Diagnosis via cysts in feces Trichomonal vaginalis
2
3
67
8
Fig 12.20
Apicomplexa: not mobile, intracellularPlasmodium , Babesia, Toxoplasma, Cryptosporidium (Clinical Focus p.355
Plasmodium vivax Life Cycle
Euglenozoa: HemoflagellatesTrypanosoma
Move by flagella Hemoflagellates
Sleeping sickness
Chagas’ disease
Amoebae Move by pseudopods
Entamoeba histolytica in human GI tract. ~ 10% carriers. Amoebic disentery.
Acanthamoeba in water. Can infect cornea.
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.
Life Cycle of Helminths
Monoecious (hermaphroditic) Male and female reproductive systems in one animal
Dioecious Separate male and female
Egg larva(e) adult
PlatyhelminthsDorsoventrally flattened
1. Trematode, or fluke: Leaf-shaped; suckers attaches to host tissue
2. Cestode, or tapeworm: Scolex (head), proglottids
4 suckers and rostellum with hooks
Gravid proglottid with uterine branches
Fig 12.27
Taenia soliumTaenia saginata
Human definitive host;
pig or cattle intermediate host.
Echinococcus granulosus
Fig. 12. 28
__________ HostTaenia saginata
Cysticerci in beef muscle
___________ HostEchinococcus granulosus
Adult in dog
Human is ….
NematodesRoundworms 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)
Fig12.29
Pinworm / Enterobius vermicularis
Pinworm (Enterobius vermicularis) in sigmoid colon
ova
Diagnosing Pinworm DiseaseDo 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??
Larvae Infective for HumansFig 25.23
Hookworms Necator americanus and Ancylostoma duodenale
Primarily in dogs and cats human heart failure,
also in human lungs
Spread via mosquitoes
Fig 12.30
The Heartworm Dirofilaria immitis
ARTHROPODS AS VECTORSKingdom: 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
Arthropod Vectors Mechanical transmission Biological transmission
Microbe multiplies in vector
Definitive host Microbe’s sexual reproduction in vector
The End