Introduction to Parasites

Question 1

What is a parasite

Answer 1

An organism that lives in another organism (host) and gets its food at the expense of this host
They are simple organisms but more complex than bacteria and consist of a wide range of pathogens

Question 2

Where can parasites cause infections

Answer 2

Tropics
Subtropics
Temperate climated

Question 3

What parasitic disease causes the most deaths globally

Answer 3

Malaria

Question 4

What are the three main groups of parasites

Answer 4

Protozoa
Helminths (worms)
Arthropods

Question 5

What type of organisms are classified as protozoa

Answer 5

Malaria
Amoebae
Flagellates

Question 6

What type of organisms are classified as helminths (worms)

Answer 6

Roundworms
Tapeworms
Flukes

Question 7

What type of organisms are classified as arthropods

Answer 7

Lice
Ticks
Mites

Question 8

What are protozoa

Answer 8

Microscopic one celled organisms
Can be free-living or parasitic in nature
Can multiply in humans

Question 9

How can protozoa be transmitted

Answer 9

Fecal-oral route

Arthropod vector

Question 10

Why type of protozoa use the fecal-oral route transmission

Answer 10

Protozoa that live in a human’s intestine

Question 11

Why type of protozoa use the arthropod vector transmission

Answer 11

Protozoa that live in the blood or tissue of a human

Question 12

What are roundworms also known as

Answer 12

Nematodes

Question 13

What are tapeworms also known as

Answer 13

Cestodes

Question 14

What are flatworms also known as

Answer 14

Trematodes

Question 15

How can a definitive diagnosis be made

Answer 15

From the identification of parasites in the host tissue or excreta should be obtained
Using microscopy to identify the different stages (i.e. parasites, cysts and ova) in the faeces

Question 16

Why should serology be used instead of a culture

Answer 16

Culture is rarely possible

Serology can be useful to detect antibodies (e.g. when parasite is located in deep tissue sites

Question 17

Give examples of protozoan infections

Answer 17

Malaria
Amoebic Dysentery
Leishmaniasis

Question 18

What is malaria

Answer 18

A mosquito-borne disease (uses Anopheles mosquito as its vector) caused by a parasite

Question 19

What do patients with malaria normally experience

Answer 19

Fever
Chills
Flu-like illnesses
If left untreated they may develop severe complications and die

Question 20

How many types of the plasmodium species are there which can cause malaria

Answer 20

4

Question 21

Which plasmodium species has the highest mortality rate for malaria

Answer 21

P. falciparum

Question 22

What types of blood films will be used for malaria

Answer 22

Thick and thin giemsa stained blood films will show the infected red cells

Question 23

What are parasite infected red blood cells called

Answer 23

Parasitaemia

Question 24

Describe the life cycle for malaria

Answer 24

Sporozoites are injected under the skin by the mosquito
This travels through the blood and will enter the liver where it matures and re-enters the circulation as merozoites
They invade red cells, multiply and lyse to reinvade more red cells

Question 25

What happens to the crescent shaped gametocytes produced in the malaria life cycle

Answer 25

They are taken up by the mosquito

Question 26

How can malaria be prevented

Answer 26

Use of insecticide treated mosquito nets (ITNs) | Prophylaxis

Question 27

How many cases of amoebic dysentery are there a year

Answer 27

200-400 million cases/yr | 100,000 deaths/yr

Question 28

What is amoebic dysentery

Answer 28

An infection which causes diarrhoea with blood/pus | The trophozoite ingests red cells by removing pseudopodia (‘hot stool’)

Question 29

When are the symptoms of amoebic dysentery most common

Answer 29

During an infection by Entamoeba histolytica

Question 30

What can be seen under a microscope in amoebic dysentery

Answer 30

Cysts formed in the stool

Question 31

What does Entamoeba histolytica cause clinically

Answer 31

Intestinal and extra-intestinal infections | Liver abscess filled with reddish-brown pus in late disease

Question 32

How many Leishmaniasis species are there

Answer 32

Several

Question 33

What can the Leishmaniasis species cause

Answer 33

Cutaneous or muco-cutaneous Leishmaniasis | Visceral Leishmaniasis

Question 34

What can Cutaneous or muco-cutaneous Leishmaniasis cause

Answer 34

Skin or mucosal ulceration

Question 35

What can visceral Leishmaniasis cause

Answer 35

Fever Weight loss Hepato-splenomegaly

Question 36

What is the Leishmaniasis species infection caused by

Answer 36

Sand-fly bite

Question 37

How can a Leishmaniasis species infection be diagnonised

Answer 37

Through the histology of biopsied materials

Question 38

Give examples of nematodes

Answer 38

Enterobiasis | Ascaris lumbricoides

Question 39

How does enterobiasis present and where is it mainly found

Answer 39

1cm Threadlike Found in children

Question 40

How can enterobiasis be diagnosed

Answer 40

By pressing adhesive sellotape against the perianal region in the morning By seeing ova under a microscope

Question 41

How do ascaris lumbricoides work

Answer 41

Through their ingested eggs which hatch in the intestines The larvae are carried through circulation into the lungs and swallowed again causing adult worms to develop in and inhibit the small intestine

Question 42

How can ascaris lumbricoides be diagnosed

Answer 42

Ova can be seen in faeces by microscopy

Question 43

State some features of ascaris lumbricoides

Answer 43

Largest nematode in the human intestine measuring between 15-35 cm in length Often asymptomatic but can cause transient pulmonary symptoms (Loefller’s syndrome). Mass of worms can obstruct the small intestine or common bile duct

Question 44

Where can cestodes be found

Answer 44

Taenia saginata (beef) Taenia solium (pork)

Question 45

How does cestodes enter taenia saginata (beef) and taenia solium (pork)

Answer 45

Larval cysts are ingested in the meats which act as intermediate hosts

Question 46

What is the adult tapeworm caused by larval cysts definitive host

Answer 46

Humans

Question 47

What are tissues cysts in humans infected with T. solium called and how do they occur

Answer 47

Cysticercosis | Through the ingestion of T. solium eggs

Question 48

How can T. solium be diagnosed

Answer 48

Ova in stools on microscopy

Question 49

What is the echinococcus species (tapeworms) carried by

Answer 49

Dogs Wolves Foxes

Question 50

How does the echinococcus species enter the human body

Answer 50

Humans ingest eggs through dog faeces The eggs hatch and enter circulation A hydatid cyst forms in liver

Question 51

How must the cyst caused by the echinococcus species be removed

Answer 51

Surgical resection which must remove the whole cyst

Question 52

What is Trematodes Schistosomiasis and how many species are there

Answer 52

A type of helminths | 3 main ones

Question 53

What are the three main species of Schistosomiasis

Answer 53

S. haematobium (bladder) S. mansoni (intestinal) S. japonicum (intestinal)

Question 54

Where are Schistosomiasis found in high quantities

Answer 54

Fresh water

Question 55

What is important for the Schistosomiasis life cycle

Answer 55

Snails

Question 56

Describe the Schistosomiasis life cycle

Answer 56

The Schistosomiasis eggs (ova) are excreted in urine or faeces Miracidia is released in freash water They penetrate the body of a snail, which acts as an intermediate host Cercaria emerge from the snails after 4-6 weeks They then penetrate human skin causing swimmer’s itch and migrate through the lungs to the liver. In the liver they mature into worms (schistosomes) which migrate to mesenteric or bladder venules to lay eggs which cause inflammation in the bladder or intestinal wall

Question 57

What is the most severe kind of schistosomiasis

Answer 57

Schistosoma japonicum

Question 58

What does schistosoma haematobium cause

Answer 58

Haematuria | Bladder cancer

Question 59

What is a helminth infection normally accompanied by

Answer 59

Eosinophilia | Elevated IgE