Protozoa

Question 1

What are protozoa

Answer 1

Single-celled, heterotrophic eukaryotes generally having an active trophozoite stage and a resting cyst stage
Includes: amoeba, flagellates, ciliates, and apicomplexa (sporozoa)

Question 2

Protozoa–> amoeba –> special characteristics?

Answer 2

Pseudopodia

Ex. Entamoeba histolytica and Naegleria fowleri

Question 3

Protozoa–> flagellates–> special characteristics?

Answer 3

Flagella
ex. Giardia lamblia
Trichomonas vaginalis
Trypanosoma brucei

Question 4

Protozoa–> ciliates–> special characteristics?

Answer 4

cilia

ex. Balantidium coli

Question 5

Protozoa–> Apicomplexa (Sporozoa)–> special characteristics?

Answer 5

No organelle of Locomotion!
Ex.
Plasmodium falciparum
Theileria (Babesia) microti

Question 6

Fungus–> Microspora–> special characteristics?

Answer 6

No organelle of locomotion
ex.Enterocytozoon bieneusi
Nosemia podocotyloidis*

Question 7

Amoeba- Intestinal (Diarrhea)

Answer 7

Water borne, transmitted by the faecal-oral route and cause diarrhea.

Question 8

Entamoeba histolytica

Answer 8

Amoeba

single nucleus, ingests rbcs (erythrophagocytosis)

may cause bloody diarrhea (amoebic dysentery) and ameobic abscesses in various organs

Cyst (infective stage) - cytoplasim contains dark chromatoidal bodies and 1 to 4 nuclei with central karyosome and peripheral chromatin (viable for 12 days if moist, 30 days in h2o, resists normal chlorine levels; DIES IF DRIED!)

Question 9

Entamoeba coli (non-pathogenic)

Answer 9

Amoeba

8 NUCLEI IN MATURE CYST

Question 10

Naegleria fowleri

Answer 10

Amoeba
in warm freshwater and soil near warm-water discharges of industrial plants and in unchlorinated pools
Thermotolerant (survives up to 45 deg.– infection more likely in summer)
3 forms: cyst, trophozoite (ameboid; infective stage for humans) and biflagellate (can be inhaled)

Question 11

Free Living Amoeba

Answer 11

Naegleria fowleri cyst has smooth, thick double wall: primary amebic meningoencephalitis (PAM), not keratitis

Acanthamoeba free living amoeba: cyst has wrinkled double wall: well characterized cause of keratitis & corneal ulceration

Balamuthia free living amoeba associated with granulomatous amebic encephalitis (GAE), not keratitis (cysts have a hexagonal wall)

Question 12

Giardia duodenalis

Answer 12

Flagellate
AKA G. intestinalis, G. lamblia)
Flagellated protozoan without mitochondria
Most common waterborne illness in United States
infective cysts : 2-4 nuclei
live in SI

Question 13

Trichomonas vaginalis

Answer 13

Flagellate
anaerobic
causes trichomoniasis (vaginitis, urethritis)
DO NOT HAVE A CYST STAGE!

complications of T. vaginalis in women include: preterm delivery, low birth weight, and increased mortality as well as predisposing to HIV infection and cervical cancer

Question 14

Leishmania

Answer 14

Flagellate
Live part of the life cycle in the gut of a fly as promastigote (INFECTIVE STAGE possessing a free flagellum and kinetoplast anterior to the nucleus) and the rest as an amastigote within vertebrate tissues (TISSUE STAGE LACKS LONG FLAGELLUM)

Question 15

Trypanosoma

Answer 15

Flagellate
Trypanosoma brucei

T. b. gambiense causes West African sleeping sickness (chronic: game are NOT reservoirs)

T. b. rhodesiensecauses East African sleeping sickness (acute: game are reservoirs)

Metacyclic trypomastigote is infective stage

T. cruzi causes New World (American) trypanosomiasis (Chagas Disease)

Acute: almost any organ is invaded causing anemia, nervous disorders, chills, muscle and bone pain, and death in three to four weeks.

Chronic: symptoms 10–30 years after the initial infection including enlargement of the ventricles of the heart leading to heart failure

Question 16

Balantidium coli

Answer 16

Ciliate

Most infections occur in developing countries where feces are more likely contact food and drinking water

Diagnosis can be made by finding ciliated trophozoites in stool or tissue. Cysts, infective stage, are rarely found.

Question 17

Apicomplexa

Answer 17

a host is infected –> parasites divide to produce sporozoites that enter its cells–> the cells burst, releasing merozoites which infect new cells.

This may occur several times, until gamonts are produced, forming gametes that fuse to create new cysts.

Comprise bulk of sporozoa
disease include:
Malaria (plasmodium spp.): blood
Theileriosis/Babesiosis (Theileria microti): Blood
Toxoplasmosis (Toxoplasma gondii): Tissue

Question 18

Cryptosporidium

Answer 18

Apicomplexa

Commonly found in HIV-positive patients presenting with diarrhea

Oocyst (infective stage) can survive for lengthy periods outside a host.

Exhibit partial acid fast staining

Can resist many common disinfectants (chlorine-based)

UV at low doses or boiling will inactivate it

Question 19

Cyclospora cayetanensis

Answer 19

Apicomplexa

humans are the only host

lifecycle = intracellularly within the host’s epithelial cells and GI tract

Transmitted through the fecal-oral route, infection causes watery, and sometimes explosive, diarrhea

The oocysts not immediately infectious; sporulation can take from 1-many weeks (person-to-person transmission is not a likely problem– outbreaks linked to imported fresh produce).

Question 20

Plasmodium (RBC parasite)– the 5 types

Answer 20

Apicomplexa

• transmitted via anapheles mosquitoes

Recrudescence: symptoms return due to parasites surviving in blood due to ineffective treatment

Relapse: symptoms reappear after parasite eliminated due to dormant hypnozoites in liver cells (P vivax and ovale)

1. P. falciparum: responsible for 50% of all malaria cases; nearly all morbidity & mortality from severe malaria (tropics and subtropics)
2. P. vivax: widest geo distribution; rare in Africa; cause of 43% of malaria cases; can lead to death due to splenomegaly
   Tertian - 2 days (fever)
   relapses (hypnozoites)
3. P. ovale curtisi/wallikeri: rare; tropical africa and west coast
   Tertian - 2 days (fever)
   relapses (hypnozoites)
4. P. malariae: 7% of malaria cases; only in sub-tropical climates
   (quartan - 3 days (fever))
5. P. knowlesi: primarily in malaria in macaques but also infects humans

Question 21

Toxoplasma gondii

Answer 21

Apicomplexa

Hosts: Felidae family (tigers, lions, bobcats, domestic cat…)

Humans can be infected by

• eating uncooked meat
• consuming food or water contaminated by cat feces
• blood transfusion or organ transplantation
• transPLACENTALLY mother to fetus
• “non cat stage” has low host specificity and can infect any mammal

undergo development in cats to form zygote containing cysts aka OOCYSTS –> cat sheds oocysts for only 1-2 weeks following infection which become infective in 1-5 days

In humans:

Most = asymptomatic.
Mild fever, sore muscles swollen glands and lymph nodes, similar to mononucleosis.

Immunocompromised = higher risk

Congenital infection = blindness, hydrocephalus, seizures and mental retardation.

3rd most common lethal food poisoning.

Question 22

Metronidazole

Answer 22

Treats the Protozoa Giardia, E. histolytica, and Trichomonas.

**Works on trophozoites and not cysts.
Also works on anaerobic bacteria

Limited to obligate ANAEROBES
Drug becomes reduced by pyruvate : erredoxin oxidoreductase system–> reduced intermediate compounds + free radicals

Reduced compounds interact with host cell DNA and result in breakage and destabilization of DNA helix and decay into inactive end products

Free radicals damage cellular proteins