Chapter 5: Part 2

Question 1

Protozoa (member of the protist family)

Answer 1

• Eukaryotic cells; diverse group of 65000 species, vary in shape, lack a cell wall
• Chemoheterotophic; lack chloroplasts
• Unicellular; rarely colonial
• Most are harmless, free-living in a moist habitat (aquatic, damp soil)
• Some are animal parasites (human tissue habitat) and can be spread by insect vectors
• Cytoplasm divided into ectoplasm and endoplasm
• Feed by engulfing other microbes and organic matter

Question 2

Cyst

Answer 2

protected structure; contains larval stage

Question 3

Vegetative Form

Answer 3

active: Trophozoite

Question 4

Definitive Host

Answer 4

final host; harbors the adult

Question 5

Intermediate Host

Answer 5

secondary host; harbors a larval or intermediate form of parasite

Question 6

Infective Form

Answer 6

egg, larva, cyst, trophozoite (how it gets to you)

Question 7

Diagnostic Form

Answer 7

present in stool, migrates out of body

Question 8

Mechanical Vector

Answer 8

Passive

• passed on outside; not in body;fly goes on poop–>poop then lands on sandwich (hitches a ride); does not spend time in life cycle
• non-specific

Question 9

Biological Vector

Answer 9

Active

• spend life cycle in vector (host)
• specific

Question 10

General Life Cycle Exhibited by Many Protozoa

Answer 10

1. Cell rounds up, loses motility; drying, ;lack of nutrients
2. Early cyst wall formation (encystment)
3. Mature cyst (dormant, resting stage)
4. Moisture, nutrients restored; cyst wall breaks open (excystment)
5. Tropozoite is reactivated
6. Trophozoite (active feeding stage)

Question 11

Protozoan Identification

Answer 11

Classification is difficult because of diversity

• Simple grouping usually based on method of motility, reproduction, and life cycle
  1. Mastigophora
  2. Sarcodina
  3. Ciliophora
  4. Apicomplexa

Question 12

Protozoan Identification: Mastigophora

Answer 12

primarily flagellar motility, some flagellar and amoeboid; sexual reproduction (flagellate)

Question 13

Protozoan Identification: Sarcodina

Answer 13

primarily amoeba; asexual by fission; most are free-living; move by pseudopods

Question 14

Protozoan Identification: Ciliophora

Answer 14

cilia; trophozoites and cysts; most are free-living, harmless

Question 15

Protozoan Identification: Apicomplexa

Answer 15

motility is absent except male gametes; sexual and asexual reproduction; complex life cycle- all parasitic

Question 16

Amoeboid Protozoa

Answer 16

Amoebiasis: Entamoeba histolytica
-reservoir/ source: Human/ water and food
Brain Infection: Naegleria, Acanthamoeba- free living in water

Question 17

Infective Amoebas

Answer 17

Entamoeba histolytica- amoebic dysentery (bloody, pus diarrhea); worldwide

Question 18

Ciliated Protozoa

Answer 18

(ciliophora)

Balantidiosis: Balantidium coli- zoonotic in pigs

Question 19

Flagellated Protozoa

Answer 19

(mastigophora)

• Giardiasis: Giardia lamblia; reservoir/ source- zoonotic/water and food
• Trichomoniasis: T. hominis, T.vaginalis; reservoir/ source- humans
• Hemoflagellates
• Trypanosomiasis: Trypanosoma brucei, T. cruzi
• Leishmaniasis: Leishmania donovani, L. tropica, L. brasiliensis; reservoir/source- zoonotic/vector-borne

Question 20

Apicomplexan Protozoa

Answer 20

• Malaria: Plasmodium vivax, P. falciparum, P. malariae; reservoir/ source- human/vector-borne
• Toxoplasmosis; Toxoplasma gondii; reservoir/ source- zoonotic/ vector-borne
• Cryptosporidiosis: Cryptosporidium; free-living/water and food
• Cyclosporiasis: Cyclospora cayetanensis; water/ fresh produce

Question 21

Trypanosoma spp.: Trypanosoma brucei

Answer 21

• causes African Trypanosomiasis or African sleeping sickness
• vector: Glossina (Tsetse Fly)
• Central Nervous System Disease (coma)

Question 22

Trypanosoma spp.: Trypanosoma cruzi

Answer 22

• causes American Trypanosomiasis or Chagas Disease
• Vector: Triatoma infestants (kissing bug)
• Cardiovascular Disease

Question 23

Trypanosoma brucei Strains

Answer 23

• Trypanosoma brucei brucei: Equines, pigs, cattle, rodents
• Trypanosoma brucei gambiense: Humans, monkeys, dogs, pigs, antelopes: West and Central Africa
• Trypanosoma brucei rhodesiense: humans, wild game, pigs, rats(experiments); East and Central Africa

Question 24

Trypanosoma brucei Strains: Trypanosoma brucei brucei

Answer 24

equines, pigs, cattle, rodents

Question 25

Trypanosoma brucei Strains: Trypanosoma brucei gambiense

Answer 25

humans, monkeys, dogs, pigs, antelopes | -West and Central Africa

Question 26

Trypanosoma brucei Strains: Trypanosoma brucei rhodesiense

Answer 26

humans, wild game, pigs, rats(experiments) | -East and Central Africa

Question 27

Life Cycle: Toxoplasma gondii

Answer 27

1. infected raw meat, rodents, birds, other animals, and contaminated soil contain Toxoplasma gondii trophozoites and/ or cysts 2. Oocysts in urine and feces; cat consumes raw meat or contaminated soil. Parasite undergoes sexual reproduction only in cats 3. Oocysts in cat urine and feces further mature into sporocysts in litter box, sandbox, or soil 4. infected pregnant woman transmits T. gondii infection to fetus 5. Congenital defects: brain damage, blindness, and mental retardation due to destruction by feeding trophozoites 6. immunocompromised patients may develop severe CNS damage or seizures or may die

Question 28

Sandfly Transmission Cycle

Answer 28

- Human, other mammalian host - Free and intracellular amastigotes in a macrophage - sand fly becomes infected by biting host - promastigote stages in the gut of the sand fly

Question 29

Helminths

Answer 29

- eukaryotic - multicellular animals - Phylum Platyhelminthes: flat worms - Phylum Nematoda: round worms

Question 30

Phylum Platyhelminthes

Answer 30

- flat worms; no body cavity - incomplete digestive system - mostly monoecious (hermaphroditic) - greatly reduced systems except reproductive - very efficient reproductive system (eggs and sperm) - Classification: 1. Class Turbellaria: free living 2. Class Cestode: tapeworms 3. Class Trematode: flukes

Question 31

Phylum Platyhelminthes: Class Turbellaria

Answer 31

free living

Question 32

Phylum Platyhelminthes: Class Cestode

Answer 32

tapeworms

Question 33

Phylum Platyhelminthes: Class Trematode

Answer 33

flukes

Question 34

Helminth Classification and Identification

Answer 34

- classify according to shape, size, organ development, presence of hooks, suckers, or other special structures, mode of reproduction, hosts, and appearance of eggs and larvae - identify by microscopic detection of worm, larvae, or eggs

Question 35

Monoecious

Answer 35

in 1 body there is both sets of sex organisms (ovaries + testes in 1 organism)

Question 36

Dioecious

Answer 36

2 houses; 1 male 1 female

Question 37

Life Cycle: Schistosoma japonicum (blood fluke)

Answer 37

schistosomiasis -exception: Reproduction- dioecious -exception: mode of transmission- penetration of skin 1. fertilized eggs leave intestinal wall and pass to outside in feces 2. eggs hatch in water 3. free swimming miracidium enters snail (alternate host) and develops into a sporocyst 4. sporocyst develop into cercaria and are released into water 5. cercaria enter the body, lose their tails, and encyst as metacercaria 6.maturation into adult worm occurs 7. worms mate and lay eggs in hepatic portal blood vessels 8. male worm holds female within a cleft in his body Cycle starts again

Question 38

Cestodes

Answer 38

``` Tapeworms Classification -Structure: scolex, proglottids -Scolex- has hooks and/or suckers -Proglottids- body segments -both male and female organs in each proglottid: hermaphroditic aka monoecious -Newest segments near the head -Older segments come out with feces ```

Question 39

Cestodes: Scolex

Answer 39

head | -has hooks and/ or suckers

Question 40

Cestodes: Proglottids

Answer 40

body segments - both male and female organs in each proglottid: hermaphroditic aka monoecious - Newest segments near the head - Older segments come out with feces

Question 41

Life Cycle of Beef Tapeworm

Answer 41

Taeia saginata Disease: Taeniasis 1. Eggs are passed in feces along with egg-filled proglottid 2. feces disintegrate, leaving eggs on grass 3. cow becomes infected when it eats contaminated grass 4. eggs hatch; larvae burrow through intestinal wall, enter bloodstream, and encyst in muscles as cysticerci 5. cysticercus (infective embryo in meat) 6. Cysticerci are ingested in rare or undercooked meat 7. adult worm attaches to mucosa of small intestine 8. new proglottids form immediately behind scolex. Old proglottids break off at the far end of worm, then eggs are passed again

Question 42

Phylum Nematoda

Answer 42

- roundworms - nonsegmented (smooth) - Reproduction: dioecious; sexual and internal - sexual dimorphic - Habitats: marine, freshwater, damp soil, moist plant tissues, animal tissues - Size: less than 1 mm to more than a meter (blunt at anterior end; tip at posterior

Question 43

Life Cycle of pinworm Enterobius vermicularis

Answer 43

- mode of transmission: ingestion (ingest eggs) - eggs into mouth - go into intestines to mature - male + female mate - female migrates out through anus + lay eggs (can wiggle back into body) (symptom- itchy butt)

Question 44

Distribution and Importance of Parasitic Worms

Answer 44

- approximately 50 species parasitize humans - distributed worldwide; some restricted to certain geographic regions with higher incidence in tropics - primarily acquired through ingestion of larvae or eggs in food; from soil or water; - exception: larvae penetrate the skin; some are carried by vectors - afflict billions of humans