Eukaryotes: Fungi, Algae, Protozoa, and Helminths

1. Eukaryotes: Fungi, Algae, Protozoa, and Helminths

2. 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

3. 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.

4. 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.

5. 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.

6. Examples of cutaneous mycosis: Ringworm • Ringworm is often thought to be caused by a worm simply because of it’s name. It’s 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.

7. 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 people’s 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.)

8. 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 owner’s 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/stachybotrys.htm

9. 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

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

11. 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.

12. 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.

13. 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.

14. 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.

15. 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 can’t possibly be dirty, it is too beautiful…. • Prevention and Rx: vaccine for animals, avoid drinking from freshwater sources. • Quinacrine or metronidazole

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

21. Helminths • 2 types: • 1. Platyhelminths: flatworms • 2. Nematoda: roundworms

22. 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.

23. Symptoms: penetration of organism causes itching as known as swimmer’s 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.

24. 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.

25. 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.

26. 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.

27. 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 person’s 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.

28. 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

29. 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

30. 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

31. 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

32. 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 body’s 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.

33. Bibliography • www.medline.com • www.med.sc.edu:85/parasitiology.htm • www.biosci.ohio-state.edu/~parasite.html