Protozoan Microorganisms

Question 1

What is parasitology? +what type of cells are parasites?

Answer 1

*study of parasites
*protozoa/helminth, ectoparasites are eukaryotic cells

Question 2

What is an endo-parasite?

Answer 2

• Inside of the host’s body - Permanently
• Some anaerobes, some aerobes
  ▪ CLASSES → Protozoa and helminths

Question 3

What is an echo-parasite?

Answer 3

• on the OUTER surface of the host’s body – temporary or permanent
• Aerobes
• Some ectoparasites serve as vectors of pathogens
  ▪ CLASSES → ticks, fleas, lice, and mites

Question 4

What are the general details of protozoa?

Answer 4

*monocellular
* mostly asexual (binary fission) and sexual reproduction
* different groups according to their locomotion modes

Question 5

What are the general details about helminths?

Answer 5

*pluricellular → parasitic worms (usually visible)
* sexual reproduction only
*move through muscular contractions

Question 6

What are some general characteristics of protozoa?

Answer 6

• Monocellular eukaryotic cells (2-100 μM)
• Diverse oxygen requirements
• All protozoa are chemoheterotrophs
  ▪ Similar requirements of the mammalian cells
• Either free-living or parasitic with many hosts
  ▪ ~ 20 human pathogens
  ▪ Animal and plant hosts, including pets

Question 7

What are some protozoa cell characteristics?

Answer 7

• Similar intracellular composition to eukaryotic mammalian cells,
  with some exceptions:
• Do not contain cell wall, but some contain a pellicle
  ▪ a flexible, proteinaceous covering
• Contains vacuoles
• The plasma membrane contains different structure for
  movement:
  ✓ Pseudopods → temporary plasma membrane extensions
  ✓ Cilia
  ✓ Flagella

Question 8

What are the two stages a protozoa exists in?

Answer 8

• vegetative (trophozoite)
  *dormant (cyst)

Question 9

What are details of this vegetative protozoa state?

Answer 9

• Motile, vegetative
  (active) form
• Actively feed & multiply
• Pathogenic form

Question 10

What are details of this dormant protozoa state?

Answer 10

• External, non-active form
• Protection against stress
  ▪ It forms an unusual cell wall
• Non-parasitic form - means of
  transfer between hosts
• High resistance against
  disinfection and therapeutics

Question 11

What is the transmission cycle like for enteric protozoa?

Answer 11

occurs through a faecal-oral route
▪ Contaminated food
▪ Contaminated water
▪ Domestic pets
▪ Sewage/waste water

Question 12

What are the different types of protozoa and their motility mode?

Answer 12

1: amoeba - through pseudopods
2: flagellates - use flagella
3: ciliates - use cilia
4: sporozoa - non motile, spore- producing

Question 13

How do amebae work?

Answer 13

• Move by extending pseudopods
  ▪ arm-like projection of the cell membrane
• Engulf food with pseudopods and phagocytize
  ▪ Entamoeba histolytica - feeds on red blood cells

Question 14

How do flagellates work?

Answer 14

*possess one or more flagella for locomotion and sensation
*target different human tracts:
- interstinal and genitourinary
- blood and tissue flagellates

Question 15

What is the transmission of blood borne protozoa?

Answer 15

• In humans, Leishmania spp. parasitise
  in mononuclear phagocytic cells
  ▪ macrophages, monocytes
• Leishmania species spread through the bite of sand flies (vectors)

Question 16

What are the type of leishmaniasis diseases?

Answer 16

*cutaneous
*mucosal
*visceral

Question 17

What does the cutaneous leishmaniasis do?

Answer 17

*affects skin → causing skin ulcers

Question 18

What does the mucosal leishmaniasis do?

Answer 18

• affects the mucous membranes of the nose and mouth, causing sores and destroying tissues

Question 19

What does the visceral leishmaniasis do?

Answer 19

*affects the internal organs, particularly the bone marrow, lymph nodes, liver and spleen
* fatal if left untreated in over 95% of cases

Question 20

What is plasmodium spp?

Answer 20

*agent responsible for malaria - major most deadly protozoa causing disease
*obligate intracellular parasite - sporozoan
* 4 species responsible – P. falciparum, P. vivax, P. malariae and P. ovale
* P. falciparum causes the most severe disease and is the most common (86%)

Question 21

How is malaria spread?

Answer 21

• Spread to humans by the bite of female mosquitoes
  (of the genus Anopheles)
• Blood transfusions
• Mother to foetus

Question 22

What are the symptoms of malaria?

Answer 22

• Acute febrile illness
  ▪ Symptoms start after 10-14
  days from mosquito’s bite
• Serious complications may occur
  ▪ cerebral malaria
  ▪ severe anaemia
  ▪ death if untreated/misdiagnosed

Question 23

What are some malaria control measures?

Answer 23

• 2 vaccines (prevents 70-30% of cases)
• antimalarial preventative drugs (90% reduction in risk, lasts 4 weeks)
• personal protection against mosquitoes (spray, 50%)
• environmental mosquito controls (destroy their eggs)

Question 24

What is malaria treatment based on?

Answer 24

▪ Type of infecting Plasmodium species.
o different drug susceptibility
▪ Clinical status of the patients
o disease severity, comorbidities
▪ Previous use of antimalarial drugs
▪ Drug resistance

Question 25

What are the hardships of antiprotozoal drugs?

Answer 25

• Protozoa are eukaryotes like
  human cells → difficult to treat
• Most mechanisms of action are
  not completely elucidated
• Some antiprotozoal drugs
  cause serious toxic effects (e.g.
  Mefloquine no longer recommended)
• Most have not proven to be safe
  for pregnant patients