lesson six

Question 1

protozoa

Answer 1

• parasite
• one-celled eukaryotes

Question 2

metazoa

Answer 2

• parasite
• multicellular animals

Question 3

ectoparasites

Answer 3

• free living bugs

Question 4

protozoa

Answer 4

• some have a cyst form with a tough protective layer outside of the cytoplasmic membrane
• growing form in many species called trophozoite (no cell wall)
• cyst form may also be called an oocyst

Question 5

protozoan: entamoeba histolytica

Answer 5

• agent of amoebic dysentery
• primary food: RBC (ulcer formation and bloody diarrhea)
• both trophozoite and cysts form
• cysts high degree of resistance to chlorine
• can be treated with nitroimidazole

Question 6

protozoan: giardia lamblia

Answer 6

• flagellate; causative agent of giardiasis (bever fever)
• intestinal upsets, flatulence, nausea, abdominal cramps, diarrhea
• cyst and trophozoite
• cysts high resistance to chlorine
• treated with nitroimidazoles

Question 7

protozoan: trichomonas vaginalis

Answer 7

• flagellate, mobile
• no cyst stage, person to person infection- sexual transmission
• found in vagina and male urethra
• intense itching, inflammation of tissues
• treated with nitroamidozoles

Question 8

protozoan: acanthamoeba sp

Answer 8

• grows in water, exists as cyst form in dust
• important for contact lens wearers
• eye loss outcome of infection
• cysts and trophozoite stage in humans

Question 9

protozoan: cryptosporidium parvum

Answer 9

• cows, rats, dogs, cats, to people
• chronic diarrhea, sever in immunocompromised
• must us ZN stain
  oocysts have high resistance to chlorine
• no good treatment

Question 10

protozoan: toxoplasma gondii

Answer 10

• cat feces contain oocysts
• tissue cysts containing the protozoan can form in other animals
• acquired from undercooked meat or from contact with cat feces
• serious for fetes in pregnancy (first trimester)

Question 11

protozoan: trypansoma

Answer 11

• blood parasites, transmission mostly vectors
  1. T. brucei gambiense causes african sleeping sickness (africa-tsetse fly)
  2. T. cruzi causes chaga’s disease in south america (kissing bug)

Question 12

protozoan: leishmania sp.

Answer 12

• 20 different species, all transmitted by sand fly vector
• visceral, cutaneous and mucocutaneous syndromes
  live and develop in macrophages

Question 13

protozoan: plasmodium sp.

Answer 13

• cause of malaria
• 4 main types, all transmitted by anopheles
• most dangerous is p. falciparum (infects all ages of RBC)
• mosquito carries the sprozoite in saliva, this enters the blood stream, then liver cells within 30 min

Question 14

symptoms of falciparum malaria

Answer 14

-fever and chills caused by release of toxic
breakdown products when the RBCs rupture and
release developing parasites
-sequestration (sticky collections) of parasites
and red blood cells occlude capillaries causing
organ death. This is due to a virulence factor
called PfEMP1

Question 15

severe consequences of p. falciparum malaria

Answer 15

• cerebral malaria: clumping and occlusion of blood vessels
• anemia: caused by lysis of RBC
• kidney failure: caused by high levels of hemoglobin breakdown products

Question 16

worms=metazoa

Answer 16

1. nematodes: intestinal and blood
2. trematodes
3. cestodes

Question 17

metazoa: nematodes

Answer 17

• roundworms with complete digestive system
• two categories
  a) eggs are the infective stage
  b) larva are the infective stage

Question 18

nematodes: enterobius vermicularis (pinworm)

Answer 18

• eggs are the infective stage
• spends whole life cycle in human
• live in large intestine, females migrate to anus
  produces a glue to stick eggs to the skin
• transmitted by direct contact with eggs or ingestion of eggs stirred up in dust

Question 19

nematodes: ascaris lumbricoides

Answer 19

• large round worms
• live in intestine of pigs, cows, horses
• eggs in soil very hardy (thick protein coat)
  infection by eggs
• diagnosis of infection by examination of feces

Question 20

nematodes: hookworms

Answer 20

• larvae as infectious stage
• enter intact skin of bare feet
• →lymph & circulatory system,
  → lungs, → coughed up and
  swallowed down to the small
  intestine, where they attach by
  hooks on the scolex
• cause anemia
• only found in warm climates

Question 21

nematodes: anisakis

Answer 21

• accidentally infect humans in larval form
• fish nematodes
• rare type of infection
• prevention: heat or blast freeze, cleaning of fish asap

Question 22

nematodes: trichinella spiralis

Answer 22

• larvae infectious
• ingestion of encysted larvae in undercooked pork, boar, bear, walrus
• larvae encyst in striated muscle fibers
• muscle weakness is a dominant symptom

Question 23

blood nematodes (filaria)

Answer 23

1. lymphatic filariasis: adult worms live in lymph tissue
2. onchocerciases: adult worms live in subcutaneous tissue
   - microfilariae: (offspring) circulate through bloodstream or migrate through subcutaneous tissue
   - transmission by mosquitoes

Question 24

trematodes: schistosoma

Answer 24

• human is infected by cercarae that penetrate intact skin in fresh water ponds
• adult worms hide from host immune system under a
  coat of protein acquired from the host
• worms reside in the venous plexus of bladder or
  intestine, depending on species.
• eggs cause inflammation

Question 25

schistosoma: s. haematobium

Answer 25

urinary schistosomiasis (bilharzia) -results in inflammation of bladder wall, chronic sequalae- cancer - Africa, Middle East

Question 26

schistosoma: s.japonicum

Answer 26

- intestinal parasite - found in far east

Question 27

schistosoma: s. mansoni

Answer 27

- intestinal parasite - found in africa, SA, caribbean over 250 million people infected

Question 28

swimmers itch

Answer 28

- Caused by a duck schistosome - These cercariae do not enter the human circulation, self-limiting, causes skin itching due to the immune response

Question 29

c. cestodes (tapeworms)

Answer 29

- intestinal parasites, dependent on host for nutrients, no digestive system - head, or “scolex” has suckers or hooks for attachment to gastric mucosa - body consists of segments called proglottids, each of which contains male and female reproductive organs - acquired by eating inadequately cooked contaminated beef, pork or fish

Question 30

tapeworms cause two types of disease

Answer 30

1. intestinal infection: mild, produced by pork, beef, fish or rodent 2. deep tissue infection: serious, pork or dog tapeworm

Question 31

c. cestodes: taenia saginata

Answer 31

- beef tapeworm life cycles requires both human and cattle - infectious tissue larvae ingested by humans in infested meat - eggs passed in feces - mild symptoms

Question 32

c. cestodes: taenia solium

Answer 32

- pork tapeworm - intermediate host is pig - cerebral cysts cause cysticercosis - person to person transmission 2 modes of infection: - eggs: hatching in intestine then escape and penetrate body tissues - larvae: result in adult worm in intestine

Question 33

c. cestodes: echinococcus granulosus

Answer 33

- dog tapeworm - small, humans are dead end hosts - larva develops into hydatid cyst with hundreds of worm parts but cannot form a whole tapeworm in humans

Question 34

ectoparasites

Answer 34

- live on skin - do not enter deep tissues - secondary infections due to scratching

Question 35

ectoparasites: scabies

Answer 35

- mites burrow into skin, feed, life span 30 days, mate, lay eggs - host defenses cause inflammation and itching - elbows, fingers, breasts, groin, buttocks

Question 36

ectoparasites: lice or crabs

Answer 36

- surface dwellers - penetrate skin with mouth, suck blood - female glues eggs to hair shafts - eggs hatch in 5-10 days - secondary infections when lice feces are crushed into wounds