L17. Eukaryotic Parasites 1

Question 1

What is a parasite?

Answer 1

A plant, animal or organism that is completely metabolically dependent on another living organism to live

Question 2

What is an ectoparasite?

Give examples [3]

Answer 2

A parasite that lives on the outside of its host

Eg. Flea, Ticks and Mites

Question 3

What are the four type of host depending on the life cycles of parasite with it?

Answer 3

1. Definitive Host
2. Intermediate Host
3. Paratenic Host
4. Reservoir Host

Question 4

What is a definitive host?

Answer 4

A host in which the host lives its complete life cycle within from ‘birth’ to maturation and including replication

Question 5

What is an intermediate host?

Answer 5

A host in which the organism develops and matures in but does NOT undergo replication within (ie. does not reach sexual maturity)

Question 6

What is a Paratenic Host?

Answer 6

A host in which the organism is able to live but in an inert or ineffective way. There is no maturity or development.

Question 7

What is a Reservoir Host?

Answer 7

(secondary host) harbours the parasite only for a short transition period, during which (usually) some developmental stage is completed
= they don’t form a necessary part of the cycle.

Question 8

What are lice? What is infection with lice called?

Answer 8

Considered an insect
Obligate, blood-sucking parasites
Infection is called SPEDICULOSIS

Question 9

What are the three types of lice that affect humans? How is each one spread?

Answer 9

Pediculus humanis = body louse spread by laying eggs in the clothing
Pediculus capitis = head louse spread by contact
Pediculus pubis = crabs (pubic hair), spread by contact

Question 10

What differentiates Pediculus capitus from Pediculus pubis?

Answer 10

Colonise head vs. pubic hair and these differ only in the shape of the base of the hair (oval vs. round)

Question 11

Describe the life cycle of lice

Answer 11

1. Adult lays eggs that attach to the base of the hair shaft and the eggs hatch within a week
2. Lice mature over 2-3 weeks until females hatch more eggs

Question 12

What is the itch in lice caused by?

Answer 12

The saliva attachment of the lice to the hair

Question 13

What are the symptoms of spediculosis?

Answer 13

Itch
Macula rashes
Secondary infection

Question 14

How is lice detected?
How is it treated?
How is the disease controlled?

Answer 14

Detection of eggs
Treated using topical insecticides (in shampoo)
Controlled by treating infected people

Question 15

What are mites?
Give an example of an itch mite
What is infection with this mite called?

Answer 15

Very small arachnids (

Question 16

Where to the mites infect?

How are they spread?

Answer 16

Tunnels in vulnerable parts of the epidermis; favouring fingerwebs, elbows, axillae, genitals

Spread by contact - highly contagious

Question 17

What are the symptoms of scabies?

Answer 17

Very significant itch

Dermatitis

Question 18

What is the treatment of scabies?

Describe disease control of scabies

Answer 18

Treatment is by Ivermectin and topical scabicides

Disease control includes treatment of infected people AND sterilisation of clothes and beddings

Question 19

Describe the life cycle of scabies

Answer 19

Adult females deposit eggs into the skin and eggs hatch and lavae molt into nymphs and are found in burrows of the skin. Mating and egg laying recurrs

Question 20

What are ticks? How do they impact in infectious diseases?

Answer 20

Ticks are arachnids that acts as vectors of infectious agents like viruses, rikettsia, bacterial and protozoal)

Question 21

What kind of hosts are humans to ticks?

Answer 21

Humans are incidental hosts

They are rarely part of the tick life cycle but the ticks will infect humans in order to get a blood meal (female only)

Question 22

What kind of disease can tick infection cause?

Answer 22

Ascending paralysis caused by toxins: Ixodes holocyclus

Question 23

What is the distribution of tick infections?

Answer 23

Eastern Australia
North America
Some parts of Europe

Question 24

What is the diagnosis and treatment of ticks?

Describe disease control

Answer 24

Diagnosed by tick detection
Treatment is by removal of the tick
Disease Control is to wear clothing (high socks, long pants), repellents and examination of the body after exposure

Question 25

What is a protozoa?

Answer 25

A complex, unicellular organism that is mainly non-parasitic but cause disease in humans

Question 26

What are the three major protozoa that cause human disease?

Answer 26

Entamoeba histolytica
Giardia intestinalis (and lamblia)
Toxoplasma gondii

Question 27

Protozoa exist in 2 different forms. What are they?

Answer 27

Trophozoite: active stage that develops and is able to replicate

Cyst: a highly robust form that can survive externally to the host but is unable to replicate

Question 28

What is Entamoeba histolytica infection?

Answer 28

The most common protozoal infection

It is an amoeba causing amoeabiasis

Question 29

How is Entamoeba histolytica spread?

Describe its life cycle

Answer 29

It is spread by faecal-oral route (contaminated water sources)

Cysts and trophozoites are passed in feces . Cysts are typically found in formed stool, whereas trophozoites are typically found in diarrheal stool. Infection by Entamoeba histolytica occurs by ingestion of mature cysts which excyst into trophozoites in the gut

The trophozoites invade the tissues in the colon causing ameobic dysentry and they may cause extra-intestinal infections (liver and brain)

Question 30

What are the symptoms of enamoeba histoyltica?

Answer 30

Prolonged watery diarrhoea and dysentry

Can cause liver abscess

Question 31

What causes giardiasis?

Answer 31

Giardia intestinalis

Question 32

Describe giardia

Answer 32

Flagellate (freely moving) primitive eukaryotes with very long lived cysts

Question 33

How is giardia intestinalis spread?

Answer 33

faecal oral transmission

zoonotic transmission

Question 34

What are the symptoms of Giardia intestinalis?

Answer 34

Some people can be asymptomatic carriers
Can cause subacute, acute and chronic diarrhoea
Sometimes bloody diarrhoea

Question 35

How is the diagnosis of giardia made?
What is the treatment?
What is disease control?

Answer 35

Cysts are detected in stool
Treated with TINIDAZOLE
Disease control is by clean water and sewage treatment
Reinfection is common (no immunity development)

Question 36

What is Toxoplasmia gondii?

Answer 36

An obligate intracellular parasite that is very common in cats

Question 37

What does toxoplasmia gondii infect?

Answer 37

All mammals and birds
High sexual reproduction in cats: cats are the definitive host where the organism reaches sexual maturity with high secretion of viable toxoplasma from it

Question 38

How is Toxoplasma gondii spread?

Answer 38

Most infections are from ingestion of undercooked meat (the animal being eaten was infected) and some ingestion from contaminated water.

The toxoplasma migrates through the gut into the tissues and causes cystic forms in the tissues (ingested). Problematic in transplant settings.

Question 39

How long does infection last?

What are the symptoms?

Answer 39

Infection persists for life and is ASYMPTOMATIC except for in immunocompromised individuals where it can cause ocular disease and CNS lesios

Question 40

What kind of infection is the problem for?

Answer 40

Infection congenitally can be very serious

Question 41

What is the risk to the mother and child (pregnacy) in toxoplasma gondii infection

Answer 41

If mother is Ab+ for it before pregnant then there is no significance.
If the mother is Ab- and then becomes infected during pregnancy there is significant risk to the foetus
- early = abortion and later trimesters = psychomotor retardnation and blindness

Question 42

What is the diagnosis method?
What is the treatment available for Toxoplasma gondii?
Describe Disease control

Answer 42

Diagnosis is by serology
Treatment is often not used (but can use Bactrim)
Disease control is avoidance of cats and cooking meat properly