1. Protozoa, Slime Molds & Helminths
Chapter 5 & 23
Talaro

2. 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

3. 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

4. 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.

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

6. 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

7. 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

8. 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

9. 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)

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

11. 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

12. 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

13. Chagas Disease

14. 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

16. 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

17. 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

18. Amebic Dysentery
Entamoeba histolytica

19. Entamoeba histolytica

20. 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

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

22. 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

23. 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
million new cases each year
2 million deaths each year

24. 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.

26. 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

27. 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

28. 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

29. 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

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

31. 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

32. Plasmodial Slime Molds

33. 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

34. 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

35. 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

36. 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

37. Ascaris

38. Hookworms

39. Ascaris lumbricoides

40. 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

41. 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

42. 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

44. 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

45. Taenia
solium