L6: Parasites

Question 0

Do all parasites require a human host?

Answer 0

No, but can still infect them and cause disease.

Question 1

What type of host do many human parasites require to complete a life cycle?

Answer 1

Human and nonhuman

Question 2

Define vectors

Answer 2

Living transmitters of disease

Question 3

Parasitic disease prevalence may depend on…

Answer 3

Whether local conditions are favourable to arthropod breading.

Question 4

What are reservoirs

Answer 4

Sources of parasites in the environment

Question 5

Reservoirs are sources of parasites in the environment. Do they participate directly in transmission to humans?

Answer 5

No.

Question 6

Are Protozoa eukaryotic or prokaryotic?

Answer 6

Eukaryotic –> unicellular.

Question 7

What type of reproduction do Protozoa have?

Answer 7

Both asexual and sexual

Question 8

Are Protozoa motile?

Answer 8

Yes

Question 9

Describe Protozoa (5)

Answer 9

1) unicellular eukaryotes
2) lack cell walls
3) generally motile
4) reproduction can be sexual or asexual
5) trophozoite (feeding form) and cysts (not all species )

Question 10

What is the reservoir of malaria

Answer 10

Infected humans

Question 11

Malaria is caused by the species of……….

Answer 11

Plasmodium Protozoa

Question 12

Name the 4 species that cause malaria.

Answer 12

1) Plasmodium falciparum
2) Plasmodium vivax
3) Plasmodium ovale
4) Plasmodium malariae

Question 13

How does transmission occur in malaria?

Answer 13

Via the bite of infected female anopheline mosquitoes.

Question 14

Mosquito life cycle [1] –> Egg (3)

Answer 14

Laid on water,
Not resistant to drying,
Hatch 2-3 days

Question 15

Mosquito life cycle [2] –> Larvae (2)

Answer 15

Come to surface to breathe,

Prefer clean unpolluted water

Question 16

Mosquito life cycle [3] –> Pupae (2)

Answer 16

Come to surface to breathe,

Few days as pupa before adult emerges

Question 17

Mosquito life cycle [4] –> Adult

Answer 17

1) males live about 1 week
- -> mate within a few days –> lay eggs within 2-3 days of mating –> lay eggs and seek new mate.

2) females can live about 1 month

Question 18

What is the mosquito life style

Answer 18

Egg –> larvae –> pupae –> adult

Question 19

How do you get malaria? (4)

Answer 19

1) Mosquito ingests blood from infected person
2) 7-9 days pass
3) Mosquito bites and infects human
4) once infected symptoms typically develop 8-30 days later

Question 20

Imported malaria…

Answer 20

Brought to non-endemic area during incubation period.

Question 21

Induced malaria…

Answer 21

Blood transfusion or sharing needles among IV drug users

Question 22

How is plasmodia injected into the human bloodstream?

Answer 22

When Mosquitos bite and feed

Question 23

Plasmodia inhabit salivary glands of infected mosquitoes as what?

Answer 23

Sporozoites

Question 24

What cells do Sporozoites enter within 30 mins?

Answer 24

Liver cells

Question 25

What happens after sporozoites enter the liver cells? What is this called?

Answer 25

They multiply and mature during the next 8-14 days to very large numbers,

Hepatocellular cycle.

Question 26

After they have multiplied and matured, what are Sporozoites released into the blood as?

Answer 26

Merozoites

Question 27

What is a merozoite?

Answer 27

Form of sporozoite which can invade red blood cells

Question 28

What happens when a merozoite invades a red blood cell? (4) what is this cycle called?

Answer 28

1) divide + mature inside red blood cells
2) red blood cells burst after 2/3 days
3) –> new generation of infective merazoites
4) merazoites infect unparasited red blood cells
ERYTHROCYTIC CYCLE

Question 29

Parasites multiply asexually by ….. what type of reproduction?

Answer 29

Fission

Question 30

Parasites multiply asexually, by fission, where?

Answer 30

Liver and red blood cells.

Question 31

Some of the plasmodia in the blood can develop into forms capable of sexual reproduction… What is this called?

Answer 31

Gametocytes

Question 32

What is the factor of which the four malarial species vary in virulence?

Answer 32

They prefer blood cells of different ages

Question 33

What blood cell ages do each of the four malarial species prefer?

Answer 33

P. falciparum –> all ages, greatest mortality risk

P. vivax and P. ovale –> young red blood cells

P. malariae –> older red blood cells

Question 34

P. vivax and ovale are virtually identical clinically and morphologically. Why can they both cause relapses?

Answer 34

Due to dormant parasites –> hypnozoites

…..within liver cells.

Question 35

What happens to red blood cells when P.falciparum infects them?

Answer 35

Develop bumps on surface

Question 36

When p.falciparum infects red blood cells, bumps are developed on the surface, what happens next? (2)

Answer 36

1) surface molecules associated with bumps, bind to endothelial cells
2) parasited cells accumulate –> impeding blood flow

Question 37

Plasmodium infected red blood cells are less deformable, how is this linked with the spleen?

Answer 37

Spleen recognises older and less deformable cells –> removes them

Question 38

What are the main symptoms of malaria

Answer 38

Fever,chills, anemia

Question 39

What are two things that have been shown to restrict the growth of malarial parasites within red blood cells?

Answer 39

Thalassemia

Glucose 6-phosphate dehydrogenase deficiency

Question 40

What are the 5 diagnosis options for malaria?

Answer 40

1) stained blood films
2) clinical diagnosis
3) antigen detection tests
4) molecular tests
5) serology

Question 41

What do molecular tests detect?

Answer 41

Mixed infections

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