1. Chapter 17 -18 Parasites of the Human Body Fungi, Protozoa, Helminthes, Arthropods

2. 17.1 Characteristics of Fungi Fungi share a combination of characteristics. Fungal life cycles involve a growth phase and reproductive phase. Molds grow as long, tangled filaments of cells in visible colonies. Yeasts are unicellular fungi. Some forms are dimorphic, growing at filamentous molds or as unicellular pathogens. Figure 02B: Fungal Colonies Courtesy of John Pitt of CSIRO Food Science, Australia

3. Most fungi (except yeasts) exist as hyphae. Hyphae are similar to roots of a plant. A mycelium is a thick mass of hyphae. Fungal cell walls are composed of chitin. (Same as Fingernails and insect exoskeletons) Hyphae containing many nuclei are considered coenocytic. (multinuclear) Fungi are heterotrophic. Most are saprobes. (live On dead organic matter) Figure 03A: Hypha Structure © Dr. Dennis Kunkel/Visuals Unlimited

4. Fungal growth is influenced by several factors. Fungi take up nutrients through absorption. Most fungi are aerobic. (need oxygen) Most fungi grow best at around room temperature. - Psychrophilic fungi grow in the refrigerator. Many fungi thrive at slightly acidic pH (pH 5-6). Figure 04: Roquefort cheese. © Jones and Bartlett Publishers. Photographed by Kimberly Potvin

5. Sporulation occurs in fruiting bodies. Asexual reproductive structures develop at the ends of specialized hyphae. Many asexual spores (sporangiospores) develop in sacs called sporangia. Others produce unprotected spores (conidia) on conidiophores. Reproduction in fungi involves spore formation. Figure 06A: Sporangia of bread mold.

6. Ascomycetes account for 75% of known fungi, including: Baker’s yeast. The edible morel. The mold that produces penicillin. Candida albicans, the cause of thrush, diaper rash, and vaginitis. Figure 13A: Yeast cells for baking © Dr. John D. Cunningham/Visuals Unlimited Penicillin mold Thrush in mouth

7. Basidiomycetes are club fungi, including mushrooms and puffballs. Basidia on the gills of a mushroom cap contain sexually-produced basidiospores. Figure 17A: Mushroom gills

8. Figure 18: The Sexual Reproductive Cycle of a Typical Basidiomycete

9. Fungal toxins are called mycotoxins. Some fungi can be poisonous or deadly when consumed. Aspergillus flavus and A. parasiticus produce carcinogenic aflatoxins which contaminate many agricultural products. Ergotism is caused by Claviceps purpurea, which grows on grains. Ergot deposited in the grain can cause: –Numbness, hot and cold sensations –seizures, paralysis of nerve endings Lysergic acid diethylamide (LSD) is a derivative of an alkaloid in ergot. 17.3 Fungal Intoxications

10. Some mushrooms produce mycotoxins. Mushroom poisoning or mycetism - Mimic acetylcholine, affecting peripheral nervous system - Causes hallucinations - Produces intoxication Amanita causes about 90% of deaths from mushroom ingestion. - Produces cramping, vomiting, and diarrhea - In a week, leads to liver and kidney failure Figure 19A: Amanita phalloides © Niels-DK/Alamy Images

11. 17.4 Fungal Diseases of the Skin Dermatophytosis is an infection of the body surface Species called dermatophytes cause dermatophytosis (tinea infections/ringworm) on the skin, hair or nails. Contagious: They can be transmitted bycontact with: domestic animals, dirt. They grow best in warm, moist areas, such as locker rooms and swimming pools, and in skin folds. Symptoms include blister-like lesions with a thin fluid discharge. Treatment often involves changing the skin environment (moisture, pH, etc.) and medical creams. Figure 20B: Ringworm Commonly called athletes foot or jock itch

12. Candidiasis often is a mild, superficial infection. Candida albicans can cause candidiasis when: the immune system is compromised or microbial populations in the body change. Vulvovaginitis, often called a “yeast infection,” involves: itching, burning, reddening. swelling, odor, discharge. Figure 21A: Candida albicans

13. Excessive antibiotic use may decrease protective bacteria in the vagina and intestine, allowing C. albicans to flourish. Oral candidiasis (thrush) involves white curd- like growth on the mucous membranes of the mouth. Onychia involves hardening, browning, and distortion of fingernails. Figure 21B: Oral candidiasis Courtesy of CDC

14. Fungal Diseases of the Lower Respiratory Tract Cryptococcosis usually occurs in immunocompromised individuals. Cryptococcus neoformans is found in urban soil and pigeon droppings. Inhaled cells penetrate to the air sacs of lungs. Cells can (rarely) pass into the bloodstream, infecting the brain and meninges. C. neoformans

15. Histoplasmosis can produce a respiratory and systemic disease. It is found in dry, dusty soil, chicken coops, and bat caves. Most people suffer only mild influenza-like symptoms. Figure 24A: H. capsulatum Courtesy of Dr. Libero Ajello/CDC

16. Blastomycosis usually is acquired via the respiratory route. It is associated with dusty soil and bird droppings. It can cause lung and skin infections. Inhalation causes: lung lesions. persistent cough. chest pains. It can cause chronic pneumonia and may disseminate to other organs in AIDS patients.

17. Diversity among Protozoa

18. Classification and Characteristics of Protists The protists are a perplexing group of microorganisms. Most are unicellular. Many are free-living, thriving in environments with water. Green algae have chloroplasts and perform photosynthesis. Some dinoflagellates cause red tides. Figure 03B: Radiolarians.

19. Amoebas are mostly free-living. Amoeboid motion occurs by the formation of pseudopods. Pseudopods also form food vacuoles for ingestion. Ciliates are covered with rows of hair-like cilia. Contractile vacuoles eliminate excess water. Figure 05A: An Amoeba and a Ciliate © M I (Spike) Walker/Alamy Images Classification and Characteristics of Protists

20. Parasite life cycles have some unique features. The infective form of some protozoa is a trophozoite, others a cyst. The sexual cycle occurs in the definitive host. The asexual cycle occurs in the intermediate host. Figure 07: The Life Cycle of Plasmodium. Vector = carrier or intermediate host of a disease

21. Several protozoal parasites cause diseases of the digestive system. Amoebiasis is the second leading cause of death from parasitic disease caused by Entameoba histolytica. Cysts enter the body through food or water contaminated with feces. Lesions may form, causing amoebic dysentery with pain, bloody stools, and fever. Rarely, parasites can spread to other organs and cause fatal abscesses. 18.2 Protozoal Diseases of the Skin, and the Digestive and Urinary Tracts

22. Figure 09: The Course of Amoebiasis Due to Entamoeba histolytica

23. Cryptosporidium parvum Figure 25.19 Intestinal parasite Waterborne Found in cattle Attach to intestinal lining Cause watery diarrhea Acid-fast Oocysts Resistant to chlorine

24. Trichomonas vaginalis no cyst stage Trichomoniasis - STD Giardia lamblia intestinal malabsorption Traveler's diarrhea, day care centers, hikers Flagellate Protozoans Figure 12.17b-d

25. A protozoan parasite also infects the urinary tract. Trichomoniasis is often transmitted through sexual contact. It is caused by Trichomonas vaginalis. Physical and chemical factors can encourage establishment in the female vagina and male urethra and prostate. Females experience: Itching, burning, discharge, odor. Males may be asymptomatic. Figure 12: Trichomonas vaginalis © Dr. Dennis Kunkel/Visuals Unlimited

26. 18.3 Protozoal Diseases of the Blood and Nervous System: Malaria The Plasmodium parasite infects the blood. Malaria affects 300-500 million people. This protozoa lives inside the red blood cells and destroys them, causing anemia and death. People get malaria by being bitten by an infective female Anopheles mosquito Figure 01: Malaria Cases (per 100,000) by Country - 2008 Source: Data from the WHO/Malaria Department.

27. Death can occur due to: loss of RBCs. anemia. RBC clustering in small vessels, causing clots in the brain, kidneys, heart and liver. Quinine is used for treatment. Figure 13. Plasmodium Life Cycle

28. Plasmodium Figure 12.19 Infected mosquito bites human; sporozoites migrate through bloodstream to liver of human Sporozoites undergo schizogony in liver cell; merozoites are produced Merozoites released into bloodsteam from liver may infect new red blood cells Merozoites are released when red blood cell ruptures; some merozoites infect new red blood cells, and some develop into male and female gametocytes 12 3 4 6 Asexual reproduction Intermediate host Merozoite develops into ring stage in red blood cell Ring stage Merozoites Another mosquito bites infected human and ingests gametocytes 7 5 Ring stage grows and divides, producing merozoites Definitive host In mosquito’s digestive tract, gametocytes unite to form zygote 8 Male gametocyte Female gametocyte Zygote Sexual reproduction Resulting sporozoites migrate to salivary glands of mosquito 9 Sporozoites in salivary gland

29. Plasmodium

30. Hemoflagellates Trypanosoma African sleeping sickness or Chagas disease Transmitted by tsetse flies or reduviid bugs Leishmania leishmaniasis – “Baghdad Boil”- Desert Storm Transmitted by sand fly vector

31. Schistosoma – blood fluke

32. 18.4 The Multicellular Helminths and Helminthic Infections (WORMS) Flatworms (Phylum Platyhelminthes) do not have respiratory or circulatory structures, or a digestive tract. Trematodes, including flukes, have complex life cycles and often 2 hosts. Eggs develop into larvae (miracidia) in water, which invade snails. Trematodes evade the immune system by having a surface similar to host cells. Figure 18A: (A) Light micrograph of a liver fluke. © Sinclair Stammers/Photo Researchers, Inc.

33. Helminths - WORMS Life Stages egg, larva, adult; complex life cycles infective stage: egg or larva definitive host: harbors adult stage intermediate hosts: may be more than one Classifications: Nematodes - roundworms Platyhelminthes - flatworms Trematodes - flukes- nonsegmented Cestodes - tapeworms- segmented

34. Cestodes, including tapeworms, have a head region called a scolex. Fertilized eggs are produced in the proglottids (individual body segments) distal from the scolex, which break off and spread eggs. Each section is hermaphroditic and can produce eggs independently. Tapeworms generally live in the host’s intestine, absorbing nutrients and absorb directly. Figure 18 (C) T. saginata showing the suckers and hooks © Dennis Kunkel Microscopy, Inc./Phototake/Alamy Images

35. Nematodes - roundworms Ascaris lumbricoides- adult stage

36. Roundworms (Phylum Nematoda) live in every habitat on Earth. Damage to the host often occurs by large worm burdens in vessels or intestines. Figure 19: Roundworms in intestines. © R.F. Ashley/Visuals Unlimited

37. Trichinella

38. Cestodes - Tapeworms Figure 12.27 Tapeworm parts: Scolex head with attachment site Proglottids body segments with testes and ovaries Taenia saginata beef tapeworm Taenia solium pork tapeworm cysticercosis

39. Tapeworms survive in the human intestines. Beef and pork tapeworm disease are caused by Taenia saginata and T. solium, respectively. They are acquired by eating poorly cooked beef or pork. The scolex attached to the intestine, causing obstruction and mild diarrhea. Longest is 37 feet long..

40. Enterobius - Pinworm Figure 12.29

41. Figure 22: Diagnosing Pinworm Disease.

43. Hookworms have a set of hooks or suckers to attach to the upper intestine. Hookworms suck blood from intestinal capillaries. This causes blood loss and anemia. Humans are the only host. Larvae in soil penetrate the skin of bare feet and enter the bloodstream. You get this by playing outside without shoes on. Figure 24: A Hookworm. © Dennis Kunkel Microscopy, Inc./Phototake/Alamy Images

44. Filariasis is caused by Wuchereria bancrofti. It is transmitted by mosquitoes. Larvae infect the lymphatic system. –They damage vessels and glands. After years of infestation, arms, legs, and scrotum swell and distort. elephantiasis, Figure 26: Elephantiasis. © John Greim/Photo Researchers, Inc.

45. Kingdom: Animalia Phylum: Arthropoda (exoskeleton, jointed legs) Class: Insecta (6 legs) –Lice, fleas, mosquitoes Class: Arachnida (8 legs) –Mites and ticks –May transmit diseases (vectors) Arthropods as Vectors Figure 12.31, 32

46. Arthropod Vectors Figure 23.24

47. Arachnids Adult arachnids have four pairs of legs Ticks and mites resemble each other morphologically Ticks are the most important arachnid vectors Serve as vectors for bacterial, viral, and protozoan diseases Second only to mosquitoes in the number of diseases they transmit Transmit Lyme disease, Rocky Mountain spotted fever, tularemia, relapsing fever, and tick-borne encephalitis Parasitic mites are found wherever humans and animals coexist Transmit rickettsial diseases among animals and humans

48. Insects Adults have three pairs of legs as well as a head, thorax, and abdomen Fleas Most fleas are not associated with humans but a few do feed on humans Bubonic Plague is the most significant disease transmitted by fleas. Killed ½ of Europe in middle ages Body lice Parasites that can also transmit disease Most common among poor or overcrowded communities

49. Insects Flies Among the most common insects Those that transmit disease are generally bloodsuckers Mosquitoes Most important arthropod vector of disease Carry some of the world’s most devastating diseases

50. Eukaryotic Microbes Table 12.1