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Eukaryotes: Fungi, Algae, Protozoa, and Helminths


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Title: Eukaryotes: Fungi, Algae, Protozoa, and Helminths

Eukaryotes Fungi, Algae, Protozoa, and Helminths
Characteristics of Fungi
  • Macroscopic Fungi (mushrooms)
  • Microscopic Fungi (molds and yeasts)
  • Dimorphic can be either hyphae or yeast
  • Hyphae long, threadlike cells
  • Mycelium hyphae grow to form filamentous mass
    visible to unaided eye (The fuzzy mold you see
    growing on old food).
  • Filamentous fungi can reproduce sexually and
    asexually by the formation of spores
  • Spores can either be sexual or asexual

  • Asexual spores are formed from hyphae.
  • They are an exact copy of the parent, no genetic
  • Sexual spores are formed by fusion of 2 opposite
    mating strains of the same species of fungus.
  • Spores are important in the identification of
    pathogenic strains of fungi because they have
    their own individual structures that can be
    identified microscopically.

Fungal Diseases
  • Any fungal infection is called a mycosis.
  • Mycoses (plural form of mycosis) are grouped into
    5 categories
  • 1. Systemic deep w/in body affecting multiple
    organs or tissues
  • Route of transmission is inhalation of spores.
  • Ex. Coccidioidomycosis a form of pneumonia that
    is most commonly found in AIDS patients. It
    generally can be found in the lungs of a healthy
    individual without causing infection. Pneumonia
    caused by this organism became a widely
    recognized symptom of AIDS infection.

  • 2. Subcutaneous beneath the skin
  • Route of transmission is direct implantation of
    spores into puncture wound in the skin.
  • http//
  • See the above website for a description and
    pictures of an example of a subcutaneous
  • 3. Cutaneous epidermis, hair and nails
  • Route of transmission is human to human, animal
    to human, or direct contact with infected hair
    and epidermal cells.

  • Examples of cutaneous mycosis Ringworm
  • Ringworm is often thought to be caused by a worm
    simply because of its name. Its true
    classification is that of a fungal infection.
  • Tinea Capitis infection of the scalp
  • Tinea Barbae infection of the beard
  • Tinea Corporis infection of the body
  • Tinea Cruris infection of the groin
  • Tinea Pedis infection of the feet
  • Tinea Manuum infection of the hands
  • Tinea Unguium infection of the nails
  • Symptoms http//
  • See the above web address for great pictures and
    descriptions of symptoms for each infection.

  • General Transmission direct or indirect contact
    with other infected humans or animals.
  • Diagnosis A piece of skin, hair or nail will be
    sent to a lab to grow the fungus in a test tube
  • Prevention and Rx avoid contact, keep
    susceptible skin areas dry
  • Try to remove shoes when possible to dry out
  • Avoid touching places such as locker room
    floors or other public places with bare feet.
  • Never borrow other peoples shoes.
  • Have pets checked if areas of hair loss are seen.
  • Topical antifungal agents are the first choice of
    treatment in mild infections. In moderate to
    severe cases an oral antifungal is prescribed.
  • http// (This is where I found
    my info on diagnosis and prevention.)

  • 4. Superficial Localized along hair shafts and
    surface epidermal cells
  • Prevalent in tropical climates
  • 5. Opportunistic
  • Pneumocystis An additional type of fungal
    pneumonia found primarily in HIV infected
  • Stachybotrys mold growing on water-damaged
    walls of homes. This is the mold responsible for
    making home owners insurance rates sky rocket in
  • Can cause fatal pulmonary hemorrhage in infants
    when spores are inhaled
  • See the following web address for transmission,
    symptoms, and safe handling procedures.

  • Yeast infections by Candida albicans
  • Thrush common infection of the mouth in infants
    and toddlers or other immuno-compromised
  • Symptoms
  • Ulcer/skin lesion in the mouth (usually on the
    tongue or inner cheeks)
  • Painful
  • Slightly raised area
  • Creamy white appearance
  • May appear curd-like ("cottage cheese"
  • Dry mouth
  • Diagnosis physical examination by a physician
  • Treatment oral antifungal medication

  • Antifungals
  • Block replication and speed up skin loss
  • Some mimick structures found in the fungal cells
    preventing cell division or replication.

  • Algae are very useful but also cause some food
  • The agar used in media is extracted from red
  • Thickeners called carageenen, used in ice cream
    and evaporated milk, are derived from red algae
    called Irish Moss.

  • Dinoflagellates (unicellular algae called
  • Dinoflagellates belonging to genus Alexandrium
    produce neurotoxins that cause paralytic
    shellfish poisoning.
  • Mollusks and clams eat algae and the neurotoxin
    is concentrated inside. When humans eat mollusks
    and clams that have eaten this type of algae they
    can become sick.
  • Current recommendations to avoid sickness are to
    avoid harvesting mollusks and clams during a red
    tide. A ride tide is caused by a large
    concentration of dinoflagellates in the water.

  • Protozoa are unicellular eukaryotic organisms
    that inhabit water and soil.
  • The feeding and growing stage is called the
  • Under adverse conditions some protozoa produce a
    protective capsule called a cyst.

Medically Important Phyla of Protozoa
  • Archaezoa
  • Trichomonas vaginalis found in vagina and male
    urinary tract.
  • Signs and Symptoms
  • Asymptomatic in 50 of infections
  • Females, White to Green discharge, chronic
    infection may lead to infertility.
  • Transmission sexual intercourse with infected
  • Prevention and Rx no vaccine, metronidazole.
  • Metronidazole interferes with anaerobic

  • Giardia lamblia found in small intestines of
    humans and other mammals
  • Signs and Symptoms
  • Diarrhea of long duration, abdominal pain and
  • Stools greasy, malodorous quality to them
  • Transmission Excreted in feces and survives in
    environment until ingested by host. For example,
    an infected animal wanders down to a beautiful
    mountain stream to take a drink and defecates
    while there. An unsuspecting hiker sees the
    beautiful mountain stream and decides to have a
    drink because it cant possibly be dirty, it is
    too beautiful.
  • Prevention and Rx vaccine for animals, avoid
    drinking from freshwater sources.
  • Quinacrine or metronidazole

Medically Important Amoeba
  • Rhizopoda (aka amoeba)
  • Apicomplexan obligate intracellular parasites,
    in other words, they can only live inside host
  • Plasmodium causative agent of malaria
  • Transmitted through bite of anopheles mosquito
  • Life Cycle of malaria see Fig. 20.15 in your
  • Transmission spread by the bite of an infected
    female Anopheles mosquito and sometimes through
    shared needles, blood transfusions and from
    mother to fetus.

  • Signs and Symptoms 10-16 day incubation period.
  • Malaise, fatigue, vague aches and nausea with or
    without diarrhea, followed by bouts of chills,
    fever and sweating.
  • Diagnosis examination of blood smears
    microscopically as well as history of travel in
    endemic areas.
  • Treatment Quinine, chloroquine. There mode of
    action is unknown. Long term therapy using
    primaquine or proguanil can eventually eliminate
    the parasite from the liver.
  • Prevention long term mosquito control by
    getting rid of standing water used for breeding,
    spraying insecticides.
  • Humans can prevent infection by using netting,
    screens, repellants to keep mosquitoes out and
    remaining indoors at night.

  • Prophylatic drugs can also be taken as a
    preventative measure but are usually too
    expensive for people in developing countries
  • Malaria is an important and deadly disease.
  • 300 million to 500 million new cases are reported
    each year (how many unreported?).
  • 90 of the new cases are reported in Africa where
    the people cannot afford drugs for prevention.
  • Almost 2 million children and young adults die
    from this disease each year.
  • 1,000 to 2,000 new cases a year are seen in the
    United States.

  • Other examples
  • Toxoplasma gondii Can cause infections in utero
    when women clean feline litter boxes while
  • Approximately 50 of cats are infected with this
  • Through the course of the infection the cat will
    begin to shed oocysts (infective form of pathogen
    shed in the feces).
  • Oocysts are very resistant to adverse
    environmental conditions and can remain infective
    for months.
  • Humans can also be infected via raw meat that is
    infected with the organism.

  • Signs and symptoms most cases are asymptomatic
    or marked by mild symptoms such as sore throat,
    swollen lymph nodes, low grade fever.
  • It is known to be transmitted tranplacentally.
    There is a 33 chance of transmission from mother
    to fetus, ultimately causing stillbirth, liver
    failure, hydrocephalus, convulsions, damage to
  • Diagnosis check serum for antibodies.
  • Treatment pyrimathamine, sulfadiazine or both
    in combination.
  • Prevention Adequate cooking of meat, washing
    hands after handling cats or cat feces.

  • 2 types
  • 1. Platyhelminths flatworms
  • 2. Nematoda roundworms

  • Divided into 2 classes
  • 1. Trematodes (aka lung, liver, blood flukes)
  • Have flat, leaf shaped bodies
  • Have ventral suckers and oral suckers for
  • Ex. Schistosomiasis
  • Approximately 250 million people infected.
  • Adult worms are 10-20mm long.
  • Transmission skin penetration by organism in
    fresh water.

  • Symptoms penetration of organism causes itching
    as known as swimmers itch.
  • Spenomegaly, blockage of the bladder
  • In severe cases may cause life threatening
  • Diagnosis Microscopic examination of eggs.
  • Treatment Praziquantel is the drug of choice.

  • 2. Cestodes (tapeworms, intestinal parasites)
  • The head (or scolex) has suckers for attachment,
    some species also have small hooks for attachment
  • Body made up of segments called proglotids that
    contain both male and female reproductive organs.
  • Mature proglotids are basically sacs of eggs.
  • Ex. Taenia saginata beef tapeworm, live in
    humans, transmission through consumption of
    undercooked meat. Adult worms can be up to 4-6
    meters long.
  • Ex. Taenia solium pork tapeworm, transmission
    through consumption of undercooked meat. Adult
    worms are slightly smaller than the beef tape

  • Symptoms light infection are asymptomatic
  • Heavier infections may produce abdominal
    discomfort, vomiting, and diarrhea.
  • Contrary to popular belief, tape worms do not
    usually contribute to significant weight loss.
  • Complications can arise when heavy infections
    cause intestinal blockage.
  • Diagnosis recovery of eggs from stool or
    perianal area.
  • Treatment Praziquantel
  • Some drugs used to treat helminth infections
    paralyze the infecting organism.
  • Niclosamides inhibit ATP production.

  • Also known as roundworms.
  • Cylindrical and tapered at each end (like an
  • Most species have a male and female, generally
    males are smaller than females.
  • Classified according to whether the egg or the
    larva is infective in humans.

Eggs infective for humans
  • Enterobius vermicularis pinworms
  • Adult pinworms found in intestine, female
    migrates to anus to deposit eggs at night. A
    single female can produce more than 10,000 eggs.
  • Transmitted by ingestion of eggs through
    contaminated clothing, bedding, carpet, etc. The
    infected persons hands will also be contaminated
    with the eggs and provide a route for reinfection
    of the infected individual and dispersal of eggs
    to new victims.
  • When an individual is diagnosed with pinworms the
    whole family is generally treated.

  • Signs and symptoms perianal itching
  • Diagnosis Graham sticky-tape method
  • Transparent tape is placed on perianal skin the
    sticky side picks up eggs, then examined
  • Parents usually have to do this since the eggs
    are deposited in the early morning hours.
  • Treatment mebendazole

Larvae Infective for Humans
  • Necator americanus hookworm, live in small
  • Eggs excreted in feces
  • Larvae hatch in soil and enters host through skin
  • Moves to lungs through blood and lymph vessel
  • Coughed up on sputum, swallowed and carried to
    small intestine
  • Diagnosis based on presence of eggs in feces
  • Avoid hookworm infections by wearing shoes

  • Adult worms live in the lumen of the small
    intestine, where they attach to the intestinal
    wall with resultant blood loss by the host.
  • Most adult worms are eliminated in 1 to 2 years,
    but longevity records can reach several years.
  • The most significant complication due to a
    hookworm infection is the anemia due to the large
    amount of blood lost to the worm

  • Trichinella spiralis referred to as trichinosis
  • Acquired by eating larvae in poorly cooked pork
  • Larvae mature into adults in small intestine and
    sexually reproduce
  • Eggs develop in female and she gives birth to
    live nematodes
  • Larvae enter blood and lymph vessels and migrate
    throughout body
  • Encyst in muscles and other tissue and remain
    there until ingested by another host
  • Diagnosis is made microscopically muscle biopsy
    examined for larvae

  • See pae 362-363 in your textbook for a good
    summary of drugs used to treat eukaryotic
  • The most important thing to understand when
    treating eukaryotic infections is that their
    cellular structure is very similar to our own
    bodys cellular structure. Finding targets that
    are different enough to not cause harm to our
    body is very difficult. As a result many drugs
    can cause harmful side-effects.

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