Protozoa

Question 1

What are the 3 groups of protists?

Answer 1

1. Lobosea -amoebe
2. Chromalveotates - apicomplexa
3. Excavates - flagellates

Question 2

define: Sporogony
Schizogony
Gametogony

Answer 2

Sporogony - mitotic division forming sporozoites
Schizogony - splitting of schizont into merozoites
Gametogony - formation of gametes, meiosis

Question 3

Basic apicomplexan lifecycle

Answer 3

Micro and mega gamete formed, fuse to form Oocyst
Oocyst undergoes mitosis to for haploid sporozoites
Develop into schizont, schizogony occurs forming merozoites
Merozoites form gametes by gametogony.

Question 4

Which apicomplexan has infected 25-50% of global population?

Answer 4

Toxoplasma gondii, causes toxoplasmosis

Question 5

Describe the two forms of toxoplasma gondii

Answer 5

1. Tachyzoites - infects host cells and multiplies quickly in cell causing lysis and all are released.
2. Bradyzoites - Cyst filled w tiny parasites in brain, can become reactivated and release tachyzoites if immunosuppressed. No treatment, fatal.

Question 6

Life cycle of toxoplasma gondii

Answer 6

Felid def host.
Oocysts released in feces
Infects int host eg rodent. Various cell types infected by tachyzoites. Then formation of pseudocysts in tissue
Vertical transmission of tachyzoites by placenta to rodent offspring,
Eaten by Cat

Question 7

What happens if humans pass onto offspring

Answer 7

If to baby through placenta, can cause hydrocephalus

Question 8

Which apicomplexan parasite can you get from infected tap water?

Answer 8

Cryptosporidium

Can’t be removed by chlorination, needs very expensive filter.

Question 9

Cryptosporidium lifecycle

Answer 9

Thick walled oocyst exits host, next host ingests contaminated food or water.
In small intestine:
Oocyst releases 4 sporozoites and parasitise epithelial cells of GI tract.
Asexual multiplication forming merozoites cycle.
Merozoites undergo gametogony forming micro and megagamonts.
Fertilisation forms a zygote then oocysts

Question 10

Global state of malaria

Answer 10

3.2 billion people at risk from malaria
90% clinical cases in tropical Africa
1000 die every day from malaria, most <5 yo

Question 11

5 malaria parasites

Answer 11

1. Plasmodium falciparum (coma and death in 24 hours)
2. P. vivax
3. P. ovale
4. P. malariae
5. P. knowlesi

Question 12

Plasmodium lifecycle

Answer 12

1. Sporozoites injected into human by mosquito, penetrate liver cell
2. Undergo exoerythrocytic schizogony. Liver cell swells as more hypnozoites are formed inside it.
3. liver cell bursts, merozoites penetrate RBC
4. Erythrocytic schizogony occurs - asexual division inside RBC. RBC burst releasing Merozoites. Rhythmic bursting of RBC = cyces of fever. asexual cycle occurs indefinitely.
5. Some merozoites form macro and microgametes.
6. Mosquito takes up gametes, as blood cools inside mosquito exflagellation of microgametes occurs.
7. fertilisation of gametes (mosis def host)
8. Migrates to mos stomach and penetrates gut wall
9. forms oocyst on outer lining of gut. Oocyst moves through haemolymph to salivary gland.
   oocyst ruptures and frees sporozoites to penetrate salivary gland.

Question 13

How is Eimeria controlled?

Answer 13

Vaccination of livestock using attenuated eimeria - selected parasites completes only 1 round of schizogony.
Less crowded livestock

Question 14

What are symptoms of Eimeria?

Answer 14

bleeding from intestinal tract and diahhorea

Question 15

Lifecycle of Eimeria

Answer 15

1. oocyst passed out of host, forms 4 sporocysts inside it.
2. host ingests oocyst. In small int: sporozoites released and enter gut cells.
3. Schizogony occurs, forming merozoites, released out of gut cell. Usually 3-4 rounds of schizogony.
4. Merozoites form micro and mega gametes. Fertilisation takes place.
   5 Zygote forms and passed out of host as Oocyst.