Chapter 5....associated with the below chapters with respect to diseasesChapter 18-23 - Eukaryotic Organisms [Fungi, Protozoans, Helminths, & Arthropod Vectors] Features that distinguish protozoal & helminthic infections :1.)More important in tropical countries than in countries like the U. S. However, parasitic diseases arebecoming more prevalent in the U. S. as more infected people move here; also because people withimmune deficiencies such as AIDS are more susceptible to certain parasites.2.) How the immune system responds to these parasites is a mystery.An immune response is activated,but the immune system is seldom able to rid the body of them.3.) They have more complex life cycles, with multiple hosts involved. A.Some General Characteristics: eukaryotic cells nonmotile heterotrophic (use organic compounds a carbon source; they cant make their own sugars; nophotosynthesis) prefer more acidic conditions than bacteria can tolerate higher osmotic pressure and lower moisture than bacteria larger than bacteria and have more cellular and morphologic detail cannot tolerate the high temps. that bacteria can (fungal spores arent as resistant as bacterial spores) most are aerobic; some are facultative anaerobes (ex. yeasts) & some are anaerobes important in ecosystems as decomposers (called saprophytes - they obtain nutrients by decomposingdead & decaying matter); some are parasites, causing disease (mycosis; mycoses is plural); some producetoxins that cause disease (mycotoxicosis; mycotoxicoses is plural). major cause of plant diseases the study of fungi is mycology B.General Morphology: most, with exception of unicellular species, have a vegetative structure called a mycelium (amultinucleate mass of cytoplasm enclosed within a system of rigid, branched, tube-like filaments calledhyphae). hyphae can be coenocytic (undivided network of branching tubes) or have septa (cross walls). cells walls are composed of cellulose, chitin (contains nitrogen - also found in the exoskeletons ofinsects, crayfish, etc.), or a combination of the two. specific morphology will be discussed later for each group of fungi

C.Reproduction - Fungi are classified by how they reproduce (sexually or asexually).[functions of spores include dissemination and reproduction] 1. Asexual Reproduction - Occurs by elongation of hyphae, budding, or asexual spore production. Asexual spores are specialized cells that are dispersed & germinate in a favorable environment toproduce a new fungus; they are products of a type of cell division called mitosis (one cell divides toform 2 daughter cells that are identical to one another and to the original parent cell).Types: sporangiospores , conidiospores. 2.Sexual Reproduction - Occurs by producing sexual spores, which form following sexual fusion ofgametes (similar to sperm & eggs).Types:zygospores, ascospores, & basidiospores. D.2 General Groups of Fungi - Yeasts vs. Molds[These are descriptive terms, not taxonomic!These organisms belong to many groups of fungi.] 1.Yeasts - characteristics: nonfilamentous, unicellular reproduce asexually by budding reproduce sexually by producing various kinds of spores aerobic or facultative anaerobes used to prepare bread, wine, beer, etc.(fermentation of carbohydrates produces ethanol &carbon dioxide)ex. Saccharomyces cerevisiae(cervesa means beer in Spanish) some are pathogenic; ex. Candida albicans(causes yeast infections, thrush; see below) 2.Molds - characteristics: filamentous, multicellular have a vegetative structure called a mycelium (a multinucleate mass of cytoplasm enclosed withina system of rigid, branched, tube-like filaments called hyphae). hyphae can be coenocytic (undivided network of branching tubes) or have septa (cross walls). also possess reproductive hyphae which produce different kinds of spores (discussed above andbelow) see below for examples.

E.Classification of Some of the Lower Fungi: 1.Zygomycetes: a. Characteristics:coenocytic hyphae, produce sporangiospores (asexual spores) & zygospores(sexual spores).b.Ex.Rhizopus nigricans- black mold that develops on stale bread; the tiny black dots on themold are the sporangia, which hold the sporangiospores; sporangia look like tiny mushroomcaps.c. can be opportunistic; some are pathogenic in the immnocompromised F.Classification of Some of the Higher Fungi: 1.Ascomycetes (Sac Fungi) a. Characteristics:includes molds with septate hyphae and some yeasts; ascospores (sexualspores) develop within sacs called asci (sing. ascus); also produce conidiospores (asexualspores). b.Examples:1.)Saccharomyces cerevisiae- yeast is used to make beer, bread, wine; cervesa meansbeer in Spanish.2.) Trichophyton - causes athlete's foot (tinea pedis); ringworm of the feet; other speciesinfect different parts of the body (dandruff, nail fungus, jock itch)3.) Penicilliumspp. - conidiospores form long chains on branching conidiophores, creating abrush-like structure that looks like a broom (penicillus means brush"); some speciesproduce the antibiotic penicillin.4.) Aspergillusspp. - form long chains on a globelike conidiophore; cause aspergillosis, apulmonary disease of animals & humans; infection is often secondary to tuberculosis,immunodeficiency, & steroid therapy.5.) Histoplasma capsulatum - causes Mississippi Valley fever (histoplasmosis); can getfrom bird droppings and bat guano; endemic disease in this area; pulmonary disease.6.) Candida albicans- part of our natural flora; opportunistic; becomes a problem whendefenses are weakened or balance of microbes is upset (ex. from antibiotic treatment);cause of vaginal & intestinal yeast infections & thrush in the mouth ("cottage cheesepatches") - called candidiasis. 2.Basidiomycetes (Club Fungi)a. Characteristics:many form basidiocarps (mushrooms, puffballs, or shelflike bodies ontrees); some are molds, a few are yeasts; produce conidiospores; also produce basidiospores(sexual spores); basidiospores form on the "gills" of mushroom basidiocarps. b. Examples:1.)Amanita- poisonous mushroom; toxin causes a mycotoxicosis2.) Cryptococcus- yeast cells surrounded by a capsule; causes fatal meningitis(cryptococcosis); transmission inhalation of contaminated dust; found in 8% of AIDSpatients. 3.Deuteromycetes (Imperfect Fungi)a. Characteristics:called the imperfect fungi because no sexual stage has been observed; weput them in this group until a sexual stage is observed; these fungi grow as yeasts or molds;identify on basis of shape & arrangement of their conidiospores (asexual spores); somespecies are pathogenic; many of these fungi have recently been placed in other phyla. G.Dimorphic Fungi - Some fungi switch between a single-celled yeast phase of growth & a mycelial phase(called dimorphism); discovered by Pasteur; some species will switch if oxygen supply decreases.Pathogenicdimorphic fungi are mycelial outside of the host & single-celled inside the host.With pathogenic species, itis usually high body temperature that causes the switch.Candida changes in response to the higher nutrientconcentrations found in the body.The problem with dimorphism is that single cells are more readily spreadin bloodstream, leading to systemic infections. H.Mycoses (Fungal Diseases) Humans usually acquire fungal disease from nature; they are not highly contagious. mycotoxicosis vs. opportunistic mycoses: See above for diseases Some produce toxins that are hallucinogenic; ex. muscarin - produced by a mushroom Some produce toxins that are highly poisonous; ex.1.)Claviceps (rye mold) - produces ergot; causes death to anyone eating bread made fromcontaminated rye; LSD is made form fruiting structures (causes hallucinations)2.) Aspergillus produces aflatoxin; which grows in many plant materials; low levels of toxin canbe carcinogenic.3.) Amanita- poisonous mushroom I.Antibiotics:Penicillins produced by Penicillium ; Cephalosporins produced by Cephalosporium.

A.General Characteristics: Unicellular eukaryotes. The protistan lineages continue into the kingdoms of plants, fungi, and animals. Limited to a moist environment because they lack a cell wall Heterotrophs Most reproduce asexually by fission (one cell divides to form 2 identical daughter cells & budding; some(ex. Plasmodium that causes malaria) under go schizogony (multiple fission).Sexual reproduction occursby conjugation, the fusion of vegetative cells, or by the fusion of specialized gametes calledgametocytes. Some have complex life cycles, requiring multiple hosts and changing their morphology (ex. Plasmodium uses the mosquito as an intermediate host) Trophozoite - active, motile, feeding stage of protozoans; parasitic stage that causes the disease in thehost. Cyst - resistant, inactive stage; how diseases are usually transmitted by the fecal-oral route; usuallymore useful than trophozoites for lab identification. B.Classification:[based on mode of locomotion or motility] 1.Mastigophora or Zoomastigophora (move by means of flagella)a. Trypanosoma gambiense - infects the blood and tissue fluids; causes African sleepingsickness (it leads to the loss of consciousness and death when it invades theCNS); can alsoinfect cattle; vector is the tsetse fly.b.Giardia lamblia- body has the appearance of a human face (4 eyes are nuclei); have 2-6flagella; form cysts; causes a waterborne dysentery (traveler's diarrhea); one of the dontdrink the water diseases; firs sigh is usually an explosive, foul-smelling watery diarrheafollowed by copious amounts of campers are a high-risk group because of a sylvatic cycle(parasite is found in mountain streams contaminated with human feces or animal feces,especially beavers).c.Trichomonas vaginalis- causes vulvovaginitis; numerous flagella

2.Sarcodina (move by means of pseudopodia or "false feet" - temporary extensions of the cell bodycaused by protein filaments of the cytoskeleton pushing on the cell membrane); feed on algae,bacteria, and other protozoans by phagocytosis.a. Amoeba proteus - freshwater; not pathogenicb.Entamoeba histolytica - causes amoebic dysentery; usually acquired by consuming fecallycontaminated water or food; flies and cockroaches can also be mechanical vectors; producecysts; first protozoan to be shown to be a pathogen (1875); one of the dont drink the waterdiseases; trophozoites may invade the intestinal mucosa where they can cause ulceration andescape into the blood vessels; they may allow bacteria in fecal material to enter the bodycavity and cause peritonitis.c. Naegleria fowleri - causes amoebic meningioencephalitis; usually seen in swimmers.d.Acanthamoeba polyphaga accumulates on the water surface of contaminated hot tubs whentubs are covered; cause ulceration of the eyes and skin; can invade the central nervous systemand cause meningioencephalitis. 3. Ciliophora(move by means of cilia)a. Paramecium caudatum- freshwater; not pathogenicb.Balantidium coli- only ciliophoran that causes disease; produces cysts; causes diarrhea oflarge intestine; rare except in the Philippines; symptoms are similar to those of amoebicdysentery. 4. Apicomplexa or Sporozoa or Haemosporina - Basically nonmotile.All have an infectious, sporelikestage (sporozoite) that is often transmitted to new hosts by an insect vector.All are parasitic(obligate parasites - cannot live apart from the host).Some have elaborate life cycles, changingbody form (trophozoite, sporozoite, merozoite); life cycle includes schizogony (multiple fission). Examplesa. Plasmodium vivax- causes malaria; vector is the mosquito; kills 1-3.5 million people each year;malaria = bad air; used to infect people with malaria to stop the progression of syphilis (feverswould kill the bacteria).b.Toxoplasma gondii- causes toxoplasmosis; humans acquire the disease by consuming cysts inthe meat of infected animals or ingesting material contaminated by cat feces containing theparasite (can get it from cleaning the litter box - doctors warn pregnant women not to dothis).c. Cryptosporidium - form cysts; cause enteritis & diarrhea; can occur in water supplies; can alsobe transmitted by fecal-oral transmission from kittens/puppies; resistant to chlorine (it cansurvive full-strength Chlorox!); threat only AIDS patients and those immunocompromised; noeffective treatment found.d.Pneumocystis carinii- may be a fungus!!; causes pneumocystis pneumonia; spread inrespiratory droplets; common in AIDS patients.

III.HELMINTHS Flatworms & Roundworms General Characteristics:AnimalsCephalization - concentration of sensory receptors toward the anterior end.Organ/system level or organization/Sexual reproduction.Most flatworms are monoecious (male & female reproductive organs in same animal).Roundworms are dioceious (separate sexes). A. Platyhelminthes (Flatworms = Trematodes + Cestodes) - most are free-living; marine and freshwater;predators, scavengers, or parasitic; some have regenerative capabilities. Trematoda(Flukes) - all parasitic of vertebrates; have complex life cycles that include sexual andasexual phases; they require at least 2 kinds of organisms to complete the cycle - they reach sexualmaturity in a primary or definitive host (always a vertebrate), their larval stages develop or becomeencysted in an intermediate host (usually an invertebrate).1. a. Clonorchis sinensis(Chinese or Human Liver Fluke)Adults live in bile ducts (in the liver) of humans (definitive host)Intermediate hosts:snail (first) and fish (second)Life cycle:a snail ingests the eggs; the eggs hatch & release a larval stage which goes throughseveral transformation before finally forming a tadpole-like cercariae; the cercariae borethrough the flesh of the snail, & escape into the water; they swim until they find theappropriate species of fish; they encyst in the muscle tissues of the fish (formingmetacercariae); the adult flukes develop in livers of humans who eat raw, infected fish; eggsof the parasite are excreted in the feces; when human feces end up in ponds, etc., snailsingest the eggs & the cycle repeats itself.] b. Schistosoma mansoni(Schistosomes or Blood Flukes) - adults live in circulatory system; spiny eggsbreak through the blood vessel wall and through the gut wall to be expelled in feces; eggs hatch intocercaria in water; cercaria then penetrate skin when a person is bathing or swimming; cause spleenand liver enlargement, dysentery, and cirrhosis of the liver Cestoda (Tapeworms) - intestinal parasites of vertebrates; no digestive system like in trematodes &nematodes; they absorb nutrients through their tegument!2. Morphology:scolex (head) with suckers and/or hooks (for attachment), proglottids (body units - eachone has male and female reproductive organs):immature proglottids (closest to the scolex), matureproglottids (next closest to the scolex), and gravid proglottids (furthest from the scolex - in theseproglottids, the uterus is filled with eggs).

General life cycle of tapeworms: the gravid proglottids break off and are passed in the definitive host'sfeces; larval forms hatch when the eggs are ingested by the intermediate host; larvae then encyst in theintermediate host (called a cysticercus or bladder worm); adult worms usually develop in the definitivehost when raw or poorly cooked infected meat is eaten.Examples: a. Taenia solium(pork tapeworm) reaches a length of 2-7 meters; primary host: humans, etc.;intermediate host: swineHumans can be infected with the adults by consuming rare pork containing cysticerci larvae;larvae then develop into adults in digestive tract of the human.Humans can also be infected with larval forms when they accidentally ingest eggs (they get themfrom other infected humans who contaminate food, etc. with the eggs when they dont use properhygiene after going to the bathroom).In this case every organ in the body may harborcysticerci.When a cysticercus dies, it releases toxins and usually causes a severe allergicreaction, which is sometimes fatal. b.Taenia saginata(beef tapeworm) reaches a length of 5-25 meters; primary host: humans, etc.;intermediate host:cattle, sheep, etc.; life cycle similar to that of T. solium above; beef riddleswith encysted larvae is called measly beef. c. Echinococcus granulosus(dog tapeworm); small - only 3 proglottids long; typical life cycle: dogs are infected by adults when they eat raw butchered livestock containing larvae (ex. rawbones, etc.)eggs are passed in feces of dog; livestock eat vegetation with eggs when grazinglarvae hatch and encyst in the muscle tissue of livestock Humans can get hydatid cysts (larvae) from ingesting the eggs (the eggs are passed in feces of dog,dog licks himself, then dog licks your face).These cysts develop in the liver, lungs, and brain.Eachfluid-filledcyst, containing many larvae, can reach the size of a grapefruit. d.Dipylidium caninum(dog & cat tapeworm) - often seen in children; flea is the intermediate host - iteats the eggs on an animal; larvae develop in flea; if a dog, cat, or human ingests the flea, the adultwill develop.Note:Larvae are not transmitted through the bite of the flea!! e. Hymenolepis nana (dwarf tapeworm) - most common tapeworm of humans in the world; intermediatehost is a grain beetle; humans can ingest the eggs in cereals and other foods that contain parts ofthe insects; intermediate host is optional (meaning that if you ingest the eggs of this worm, you getan adult infection).

B.Nematoda (Nematodes) General characteristics:Nematodes are everywhere!!!!They are freeliving in soil, fresh & salt water, & are parasitic in plantsand animals.Dioecious (separate sexes).Possess a nonliving cuticle, which is secreted by the epidermis and is resistant to the digestiveenzymes of the hosts.More highly developed than flatworms.Adults do not latch onto the host like the tapeworms. 1. Ascaris lumbricoides (intestinal roundworm of pigs, horses, humans)largest intestinal nematode in humans.disease is called ascariasisEggs can remain viable even in preservative!Females are longer; males are shorter & have a hooked posterior end. 2. Enterobius vermicularis(pinworm)parasitizes large intestine of humans (especially children)at night the females migrate to the perianal region to lay eggstheir presence there causes itchinghosts become infected by accidentally ingesting the eggs. 3. Ancylostoma caninum & Necator americanus(hook worms)larvae can penetrate the skin of a barefoot persononce inside, the larvae travels through the bloodstream to the lungs, moves up the trachea, iscoughed up & swallowed; it matures in the small intestine.Ancyclostoma has fangs; Necator has cutting plates. 4. Trichinella spiralis(pork roundworm)humans usually become infected by eating insufficiently cooked porklarvae are encysted in the muscle tissues of the pigcauses trichinosis; larval migration can cause death. 5. Wucheria bancrofti adults live in lymph nodes where obstruction of lymph vessels leads to grotesque enlargement ofthese nodes & to a condition called elephantiasisa mosquito is the intermediate host. 6. Dirofilaria immitis- causes heartworm disease in dogs; a few cases in humans & cats; mosquito isintermediate host. 7. Trichuris trichiura - (whipworm) - adults partially embed in the mucosa of the large intestine; each adultproduces 1,000-7,000 eggs/day! Return to Chp. index