Eukaryotes: Fungi, Algae, Protozoa, and Helminths

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Eukaryotes Fungi, Algae, Protozoa, and Helminths
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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

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• Asexual spores are formed from hyphae.
• They are an exact copy of the parent, no genetic
  variation.
• 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.

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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.

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• 2. Subcutaneous beneath the skin
• Route of transmission is direct implantation of
  spores into puncture wound in the skin.
• http//dermnetnz.org/fungal/fungi-general.html
• See the above website for a description and
  pictures of an example of a subcutaneous
  infection.
• 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.

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• 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//dermnetnz.org/fungal/tinea.html
• See the above web address for great pictures and
  descriptions of symptoms for each infection.

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• 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
  feet.
• 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//familydoctor.org (This is where I found
  my info on diagnosis and prevention.)

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• 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
  patients.
• Stachybotrys mold growing on water-damaged
  walls of homes. This is the mold responsible for
  making home owners insurance rates sky rocket in
  Texas.
• Can cause fatal pulmonary hemorrhage in infants
  when spores are inhaled
• See the following web address for transmission,
  symptoms, and safe handling procedures.
  http//www.idph.state.il.us/envhealth/factsheets/s
  tachybotrys.htm

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• Yeast infections by Candida albicans
• Thrush common infection of the mouth in infants
  and toddlers or other immuno-compromised
  individuals.
• 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"
  appearance)
• Dry mouth
• Diagnosis physical examination by a physician
• Treatment oral antifungal medication

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

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Algae

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

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• Dinoflagellates (unicellular algae called
  plankton)
• 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.

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Protozoa

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

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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
  partner.
• Prevention and Rx no vaccine, metronidazole.
• Metronidazole interferes with anaerobic
  metabolism.

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• Giardia lamblia found in small intestines of
  humans and other mammals
• Signs and Symptoms
• Diarrhea of long duration, abdominal pain and
  flatulence
• 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

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Medically Important Amoeba

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

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• 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.

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• 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.

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• Other examples
• Toxoplasma gondii Can cause infections in utero
  when women clean feline litter boxes while
  pregnant.
• Approximately 50 of cats are infected with this
  organism.
• 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.

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• 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
  retina.
• 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.

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Helminths

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

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Platyhelminths

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

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

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• 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
  worm.

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• 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.

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Nematodes

• Also known as roundworms.
• Cylindrical and tapered at each end (like an
  earthworm).
• 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.

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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.

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• 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
  microscopically
• Parents usually have to do this since the eggs
  are deposited in the early morning hours.
• Treatment mebendazole

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Larvae Infective for Humans

• Necator americanus hookworm, live in small
  intestine
• 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

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• 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

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• 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

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• See pae 362-363 in your textbook for a good
  summary of drugs used to treat eukaryotic
  infections.
• 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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Bibliography

• www.medline.com
• www.med.sc.edu85/parasitiology.htm
• www.biosci.ohio-state.edu/parasite.html