XIII Flagellates (2005) A. Hemoflagellates (Chapter 5) 1. Classification of trypanosomes a. Phylum Euglenazoa b. Subphylum Kinetoplasta * c.

Transcription

1 XIII Flagellates (2005) A. Hemoflagellates (Chapter 5) 1. Classification of trypanosomes a. Phylum Euglenazoa b. Subphylum Kinetoplasta * c. Class Trypanosomatida d. Important genera (1) Trypanosoma (2) Leishmania 2. Characteristics a. TRYP = hole, flagella embedded in an invagination = flagellar pocket b. Leaf-like c. One flagellum (1) Anterior is the free end (2). Location of pocket determines form (Life cycle may have more than one form) d. Forms (1) AMASTIGOTE (a) A = without (b) No flagellum (c) Usually intracellular Picture Slide #1: Amastigote; Fig 5.3a, p.63 (2) PROMASTIGOTE (a) PRO = forward (b) Pocket on anterior end (c) (d) Usually occurs in vitro, = cultures Considered most generalized form or form most closely resembling the ancestor of trypanosomes Picture Slide #2: Promastigote; Fig 5.3e, p 63 (3) EPIMASTIGOTE (a) EPI = upon (b) Pocket slightly anterior to nucleus (4) TRYPOMASTIGOTE (a) Pocket posterior (b) Flagellum attached to length of cell (c) Considered the most complex or specialized form Picture Slide #3: Epimastigote; Fig 5.3c, p. 63 Picture Slide #4: Trypomastigote; Fig 5.3f, p. 63 e. Important organelles (pp 46-48) (1). KINETOPLAST (a) (b) (c) (d) KINETO = movement Diagnostic of trypanosomes Near base of flagellum Modified mitochondrion

2 (e) Contains more extracellular DNA than any organelle in any ` other eukaryotic cell Picture Slide #5: Kinetoplast; Fig 5.1, p 62 (2). UNDULATING MEMBRANE (a) Membrane connecting most of flagellum to body; sail (b) Epimastigotes & trypanomastigotes only f. Methods used to infect hosts (1). Salivarian trypanosomes (a). Develop in vector s salivary glands (b). Accompany saliva into new host when vector bites (c) Example: Trypanosoma brucei African sleeping sickness (2) Stercorian trypanosomes (a) In vector s intestine (b) Leave insect in feces (c) Invasion methods 1) Burrow through skin 2) Enter bite lesion (d) Example: T. cruzi, Chaga s disease 3. Trypanosomes that infect humans a. T. cruzi (pp 70-76) = Chagas disease (1) Distribution (a) Kills 43,000 annually in Central & South America (b) 12/500 Rio Grande Valley, Texas in 1970 s (c) DNA detected in mummies from the Andes (oldest 4,000 years) (2) Reservoir hosts (a) Dogs & cats (b) Armadillos & opossums in Southern US (3) Vector = kissing bug, Family Reduviidae (a) During day in home wall crevices (b) Bites sleepers near mouth (c) Defecates when feeding (d) Victim scratches bite & smears trypanosomes in feces into eye or wound (4) Life-cycle in human (a) Mastigotes in blood Picture Slide #6: Chaga s Disease Vector, Rhodnius, The Kissing Bug; Found in crevices in homes, feeds at night Picture Slide #7: Trypanosomes among blood cells (b) Amastigotes intracellular in muscle & reticuloendothelial cells = macrophages (c) Multiply in host cells (d) Escape host macrophages (5) Pathology (a) Destroy cardiac muscle 2

3 (b) In chronic cases (20 years), peristalsis of digestive tract ceases due to nerve damage [= megacolon] Picture Slide #8: T. cruzi amastigotes, Heart tissue Quotation Slide #9: From: Pringle, H. 1998, Discover, The Sickness of Mummies, p [Reinhard] examined the body a 1,150-year old mummy, the body of a man 35 to 45 years old, exhumed form the northern fringe of the Chihuahuan Desert, near the Texas-Mexico border... [The]food [in the large intestine] occupied nearly a cubic foot of space in the man s pelvic girdle crowding out the kidneys and the bladder and jamming up against the spine. There was so much pressure from the food that there is actually an indentation the colon from the bones of the spine, says Reinhard. And the man must never have been able to urinate either. He had no body functions. What a horrible way to die. b. T. brucei brucei, T. brucei gambiense, & T. brucei rhodesiense (pp 65-69) (1) African sleeping sickness (2) Vector (a) Tsetse flies (b) Glossina (Family Muscidae) (3) Hosts (a) Ungulate (= hoofed) mammals (b) Humans (4) Distribution (a) (b) Central Africa Historically large regions of Africa were sparsely settled because of T. brucei Picture Slide #10: Distribution of sleeping sickness; Fig 5.5, p. 66 Picture Slide #11: Parasitology in The Far Side Quotation Slide #12: From Jared Diamond (1997) Guns, Germs, and Steel p Africa s north-south axis also seriously impeded the spread of livestock. Equatorial Africa s tsetse flies, carrying trypanosomes to which native African wild mammals are resistant, proved devastating to introduced Eurasian and North African species of livestock. The cows that the Bantu acquired from the tsetse-free Sahel zone failed to survive the Bantu expansion through the equatorial forest. Although horses had already reached Egypt around 1800 B.C. and transformed North African warfare soon thereafter, they did not cross the Sahara to drive the rise of the cavalry-mounted West African kingdoms until the first millennium A.D., and they never spread south through the tsetse fly zone. While cattle, sheep, and goats had already reached the northern edge of the Serengeti in the third millennium B.C., it took more than 2,000 years beyond that for livestock to cross the Serengeti and reach southern Africa. Quotation Slide #13: From Frederick Cartwright (1972) Disease and History p David Livingston wrote that the tsetse fly was fatal to horses and cattle and a barrier to progress ; because of nagana [=sleeping sickness], the horse could not be used for transport in Equatorial Africa; all cross country journeys had to made on foot, goods were carried on the heads of natives. 3

4 (5) Disease forms (a) Gambian or chronic form 1) Lasts years 2) Circulatory, nervous, & lymphatic systems attacked 3) Victim weak & sleepy 4) Mortality high (b) Rhodesian or acute form 1) Death w/in a year 2) Severe cardiac damage 3) Nervous & lymphatic systems not greatly affected c. Leishmania tropica & L. major, pp (1) CUTANEOUS LEISHMANIASIS or oriental sores (2) Tropics & subtropics (3) Vectors are sand flies; Phlebotomus (4) Cutaneous infections (5) Not lethal d Leishmania donovani (= L. braziliensis & L. mexicana) pp (1) VISCERAL LEISHMANIASIS or kala-azar (2) Vectors are sand flies (3) Dogs are reservoir hosts (4) Asia, Africa, Central & South America (5) Tissues attacked (a) Reticuloendothelial cells (b) Spleen, liver & intestinal villi (6) Can be fatal 5. Coat-of-many-colors a Vertebrate immune system, pp (1) Cell surfaces coated with glycoproteins (= antigens) (2) B-cells make molecules (= antibodies) that bind to antigens on surfaces of foreign cells (3) Death of foreign cells (a) Antigen-antibody coating can kill foreign cells outright (b) Antigen-antibody coating marks cells for destruction by Killer T- cells (c) Process requires time b Subversion of immune system by trypanosomes (1) Trypanosomes have many genes that code for surface proteins (variable surface glycoproteins = VSGs) (2) Host immune system will eventually eliminate most common strain (99% of trypanosome population) which bears VSG #1 (3) Surviving trypanosomes carry VSG #2 and their uninhibited reproduction results in a 2nd peak of infection (4) Host responds to VSG #2 strain (5) Cycle repeats until (a) Host is resistant to all VSGs (b) Weakened host dies. 4

5 B. Body cavity flagellates (Chapter 6) 1 Giardia duodenalis (= G. lamblia & G. intestinalis) a Taxonomy (1) Phylum Retortamonada (2) Order Diplomonadida * (3) Family Hexamitidae b Characteristics (Face) (1) Two nuclei & 2 large endosomes (= nucleoli); eyes of face (2) Four pairs of flagella (3) Ventral adhesive disc c Direct life-cycle d Transmission usually by drinking cysts e Found in small intestine of mammals (1) Attach to surface of epithelial cells in lumen (2) Physically interferes with ability of host cells to absorb nutrients by covering external surface of absorptive cells f Pathology (1) Intestinal cramping (2) Diarrhea (3) Not fatal g. One of 10 most common human parasites Picture Slide #14: Giardia intestinalis trophozoite; Fig 6.5, p Trichomonads a b c Taxonomy (1) Phylum Axostylata (2) Order Trichomonadida (TRICHO = hair) (3) Family Trichomonadidae Characteristics (1) PARABASAL BODY (a) Attached to kinetosomes of flagella (b) Homologous to Golgi apparatus (c) Sometimes wound around axostyle (d) Not homologous to kinetosome of trypanosomes (2) AXOSTYLE: Filament that passes through body projecting from the posterior (3) Several (3-5) flagella (4) An undulating membrane Trichomonas vaginalis (1) Transmitted sexually (2) Location (a) (b) (3) Symptoms include white discharge (4) Morbidity of infant during childbirth Upper portion of vagina around cervix Male urethra & prostate gland Picture Slide #15: Trichomonas vaginalis; Fig. 6.12b, p. 96 c Pentatrichomonas (=Trichomonas) hominis 5

6 (1) Located in large intestine of humans, dogs & cats (2) Usually 5 anterior flagella (3) Worldwide (4) No pathologies known 6