Protozoa, Slime Molds & Helminths Chapter 5 & 23 Talaro

Protozoa 65,000 species Heterotrophic Eukaryotic Most are unicellular, colonies are rare Most have locomotive structures flagella, cilia, or pseudopods Vary in shape Typically inhabit water or soil

Protozoa Trophozoite Cyst Asexual and sexual reproduction Motile feeding stage Cyst A dormant resistant stage Asexual and sexual reproduction Most propagate by simple asexual cell division of the trophozoite Many undergo formation of a cyst Others have a complex life cycle that includes asexual & sexual phases Majority are NOT pathogens Some are animal parasites & can be spread by insect vectors

Zoonosis An infectious disease in animals that can be transmitted to people. The natural reservoir for the infectious agent is an animal. The apical complex include structures that allow the parasite to enter other cells. Anterior vesicles that secrete digestive enzymes.

Flagellated Protozoa Motility by flagella alone or by both flagella & amoeboid motion Several parasites Giardia Trichomonas Trypanosoma Leishmania attachment

Trichomonas Small, pear-shaped cells 4 anterior flagella & an undulating membrane Exists only in trophozoite form 3 species infect humans T. vaginalis T. tenax T. hominis

Trichomonas vaginalis Causes an STD called trichomoniasis Reservoir is human urogenital tract 50% of infected are asymptomatic Strict parasite, cannot survive long outside of host 3 million cases/year Female symptoms Foul-smelling, green-to-yellow discharge Vulvitis Cervicitis Urinary frequency & pain Male symptoms Urethritis, thin, milky discharge, occasionally prostate infection Flagyl (Metronidazole) Interferes with DNA synthesis

Giardia lamblia Unique symmetrical heart shaped cells Cysts are small, compact, and multinucleate Cysts can survive for 2 months in environment Cysts enter duodenum, geminate, & travel to jejunum to feed & multiply Spread through contaiminated water & food Fecal oral contamination Giardiasis Diarrhea, abdominal pain Diagnosis is difficult because organism is shed in feces intermittently

Hemoflagellates Live in blood & tissues of human host Obligate parasites Incite life-threatening and debilitating zoonoses Spread by blood-sucking insects that serve as intermediate hosts Acquired in specific tropical regions Have complicated life cycles & undergo morphological changes Trypanosoma T. brucei (causes sleeping sickness) - T. cruzi (causes Chagas disease) Leishmania (causes Leishmaniasis)

Infective Trypanosoma cruzi Diagnostic large fully formed stage no flagella Infective anterior flagellum undulating membrane Diagnostic Trypanosoma cruzi

Trypanosoma brucei Causes African Sleeping Sickness Spread by tsetse flies Harbored by reservoir mammals Biting of fly inoculates skin with trypanosome, which multiplies in blood & damages spleen, lymph nodes & brain Chronic disease symptoms are sleep disturbances, tremors, paralysis & coma

Trypanosoma cruzi Chagas disease Kissing bug is the vector Reduviid / Assassin Bugs re·du·vi·id (family Reduvidae, subfamily Triatominae (Triatomine Bugs)) Infection occurs when bug feces are inoculated into a cutaneous portal Local lesion, fever, & swelling of lymph nodes, spleen, & liver Heart muscle & large intestine harbor masses of amastigotes Divide by binary fission Chronic inflammation occurs in the organs Especially heart & brain

Chagas Disease

Leishmania Leishmaniasis is a zoonosis transmitted among mammalian hosts by female sand flies that require a blood meal to produce eggs Infected macrophages carry the pathogen into the skin & bloodstream, giving rise to fever, enlarged organs & anemia Kala azar is the most severe & fatal form Viscera or the internal organs, particularly the liver, spleen, bone marrow & lymph nodes

Amoeboid Protozoa Amoeba Radiolarian Entamoeba histolytica Pseudopods Shelled ameba Entamoeba histolytica Incites dysentery, abdominal pain, fever, diarrhea & weight loss Carried by 10% of world population Asymptomatic in 90% of patients

Entamoeba histolytica Alternates between a large trophozoite, motile by means of pseudopods & a smaller nonmotile cyst Humans are the primary hosts Ingested Cysts are swallowed & enter the small intestine; alkaline pH & digestive juices stimulate cyst to release 4 trophozoites Trophozoites attach, multiply, actively move about & feed Ameba may secrete enzymes that dissolve tissues & penetrate deeper layers of the mucosa

Amebic Dysentery Entamoeba histolytica

Entamoeba histolytica

Ciliated Protozoa Trophozoites have cilia Majority are nonpathogens Balantidium coli An occupant of the intestines of domestic animals such as pigs & cattle Acquired by ingesting cyst-containing food or water

Balantidium coli Trophozoite erodes intestine & elicits intestinal symptoms Healthy humans are resistant Rarely penetrates intestine or enters blood

Apicomplexan Protozoa Non-motile in mature stage Male gametes are motile Alternate between sexual & asexual phases & between different animal hosts All members are parasitic Most form specialized infective bodies that are transmitted by arthropod vectors, food, water, or other means Plasmodium Toxoplasma Cryptosporidium

Plasmodium 300-500 million new cases each year Causes malaria Female Anopheles mosquito is the vector Obligate intracellular sporozoan 4 species: P. malariae, P. vivax, P. falciparum & P. ovale 300-500 million new cases each year 2 million deaths each year

Plasmodium Infective forms for humans (sporozoites) enter blood with mosquito saliva, penetrate liver cells, multiply, and form hundreds of merozoites, which multiply in & lyse RBCs. Symptoms include episodes of chills-fever-sweating, anemia, and organ enlargement.

Toxoplasma gondii Causes toxoplasmosis Obligate parasite with extensive distribution Lives naturally in cats that harbor oocysts in the GI tract Acquired by ingesting raw meats or substances contaminated by cat feces Most cases of toxoplasmosis go unnoticed except in the fetus & AIDS patients which can suffer brain & heart damage

Cryptosporidium An intestinal pathogen Infects a variety of animals Exists in tissue & oocyst phases 1990s – 370,000 cases in Milwaukee, WI due to contaminated water Causes enteric symptoms AIDS patients may suffer chronic persistent diarrhea

Slime Molds Two classifications - cellular and plasmodial Motile Not pathogens Ingest food by endocytosis Form spores on erect fruiting bodies Cellular slime molds only undergo asexual reproduction Plasmodial slime molds undergo both sexual and asexual reproduction

Cellular Slime Molds - Asexual Unusual life cycle - both amebal and fungal-like characteristics Favorable conditions allow amebal growth Unfavorable conditions cause some cells to generate cAMP Cells migrate toward cAMP and aggregate – form a pseudoplasmodium ‘Slug’ moves toward light - differentiates Spores generate in cap Released to germinate as amoebal form under favorable conditions

Cellular Slime Mold migrates Amebas congregate toward cAMP Amebas disseminated as spores migrates Amebas congregate toward cAMP

Plasmodial (acellular) Slime Molds Large cell with many nuclei - PLASMODIUM Moves as giant amoeba engulfing organic matter and bacteria Distributes nutrients through cytoplasmic streaming Form stalks and reproductive structures under starvation conditions Sporangium with spores Nuclei undergo meiosis, spores released under favorable conditions Fuse to form diploid cells, cells fuse to make plasmodium

Plasmodial Slime Molds

Parasitic Helminths Multicellular parasitic animals Adult worms mate & produce fertilized eggs that hatch into larvae that mature in several stages to adults The sexes may separate or hermaphroditic Adults live in the definitive host Eggs & larvae may develop in the same host, external environment or an intermediate host A transport host experiences no parasitic development Have mouthparts for attachment to or digestion of host tissues Most have well-developed sex organs that produce eggs and sperm 50 species parasitize humans Acquired though ingestion of larvae or eggs in food; from soil or water; some are carried by insect vectors Afflict billions of humans

Major Groups of Helminths Roundworms (nematodes) - cylindrical, a complete digestive tract, a protective surface cuticle, spines & hooks on mouth; excretory & nervous systems poorly developed Flatworms – flat, no definite body cavity; digestive tract a blind pouch; simple excretory & nervous systems Cestodes (tapeworms) Trematodes or flukes, are flattened , nonsegmented worms with sucking mouthparts

Roundworms Filamentous with protective cuticles, circular muscles, a complete digestive tract, & separate sexes Ascaris lumbricoides Trichuris trichiura Enterobius vermicularis –pinworm Hookworms Strongyloides stercoralis Trichinella spiralis – raw pork… Filarial worms

Ascaris lumbricoides A large (up to 30 mm long) intestinal roundworm 1 billion cases worldwide Most cases in the US occur in the southeastern states Indigenous to humans Ascaris spends its larval & adult stages in humans & releases embryonic eggs in feces, which are spread to other humans Ingested eggs hatch into larvae & burrow through the intestine into circulation & travel to the lungs & pharynx & are swallowed Adult worms complete cycle in intestines

Ascaris

Hookworms

Ascaris lumbricoides

Ascaris lumbricoides Worms retain motility, do not attach Severe inflammatory reactions mark the migratory route Allergic reactions can occur Heavy worm loads can retard physical & mental development

Tapeworms Flatworms Long, very thin, ribbonlike bodies composed of sacs (proglottids) & a scolex (head) that grips the intestine Each proglottid is an independent unit adapted to absorbing food & making & releasing eggs Taenia saginata Taenia solium

Taenia saginata Beef tapeworm Very large, up to 2,000 proglottids Humans are the definitive host Animals are infected by grazing on land contaminated with human feces Infection occurs from eating raw beef in which the larval form has encysted Larva attaches to the small intestine & becomes an adult Causes few symptoms – sometimes weight loss despite good appetite

Taenia solium Pork tapeworm Infects humans through ingesting cysts or eggs Eggs hatch in intestine, releasing tapeworm larva that migrate to all tissues & encyst Most damaging if they lodge in heart muscle, eye, or brain May cause seizures, psychiatric disturbances

Taenia solium