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