L17. Eukaryotic Parasites 1 Flashcards
What is a parasite?
A plant, animal or organism that is completely metabolically dependent on another living organism to live
What is an ectoparasite?
Give examples [3]
A parasite that lives on the outside of its host
Eg. Flea, Ticks and Mites
What are the four type of host depending on the life cycles of parasite with it?
- Definitive Host
- Intermediate Host
- Paratenic Host
- Reservoir Host
What is a definitive host?
A host in which the host lives its complete life cycle within from ‘birth’ to maturation and including replication
What is an intermediate host?
A host in which the organism develops and matures in but does NOT undergo replication within (ie. does not reach sexual maturity)
What is a Paratenic Host?
A host in which the organism is able to live but in an inert or ineffective way. There is no maturity or development.
What is a Reservoir Host?
(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.
What are lice? What is infection with lice called?
Considered an insect
Obligate, blood-sucking parasites
Infection is called SPEDICULOSIS
What are the three types of lice that affect humans? How is each one spread?
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
What differentiates Pediculus capitus from Pediculus pubis?
Colonise head vs. pubic hair and these differ only in the shape of the base of the hair (oval vs. round)
Describe the life cycle of lice
- Adult lays eggs that attach to the base of the hair shaft and the eggs hatch within a week
- Lice mature over 2-3 weeks until females hatch more eggs
What is the itch in lice caused by?
The saliva attachment of the lice to the hair
What are the symptoms of spediculosis?
Itch
Macula rashes
Secondary infection
How is lice detected?
How is it treated?
How is the disease controlled?
Detection of eggs
Treated using topical insecticides (in shampoo)
Controlled by treating infected people
What are mites?
Give an example of an itch mite
What is infection with this mite called?
Very small arachnids (
Where to the mites infect?
How are they spread?
Tunnels in vulnerable parts of the epidermis; favouring fingerwebs, elbows, axillae, genitals
Spread by contact - highly contagious
What are the symptoms of scabies?
Very significant itch
Dermatitis
What is the treatment of scabies?
Describe disease control of scabies
Treatment is by Ivermectin and topical scabicides
Disease control includes treatment of infected people AND sterilisation of clothes and beddings
Describe the life cycle of scabies
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
What are ticks? How do they impact in infectious diseases?
Ticks are arachnids that acts as vectors of infectious agents like viruses, rikettsia, bacterial and protozoal)
What kind of hosts are humans to ticks?
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)
What kind of disease can tick infection cause?
Ascending paralysis caused by toxins: Ixodes holocyclus
What is the distribution of tick infections?
Eastern Australia
North America
Some parts of Europe
What is the diagnosis and treatment of ticks?
Describe disease control
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
What is a protozoa?
A complex, unicellular organism that is mainly non-parasitic but cause disease in humans
What are the three major protozoa that cause human disease?
Entamoeba histolytica
Giardia intestinalis (and lamblia)
Toxoplasma gondii
Protozoa exist in 2 different forms. What are they?
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
What is Entamoeba histolytica infection?
The most common protozoal infection
It is an amoeba causing amoeabiasis
How is Entamoeba histolytica spread?
Describe its life cycle
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)
What are the symptoms of enamoeba histoyltica?
Prolonged watery diarrhoea and dysentry
Can cause liver abscess
What causes giardiasis?
Giardia intestinalis
Describe giardia
Flagellate (freely moving) primitive eukaryotes with very long lived cysts
How is giardia intestinalis spread?
faecal oral transmission
zoonotic transmission
What are the symptoms of Giardia intestinalis?
Some people can be asymptomatic carriers
Can cause subacute, acute and chronic diarrhoea
Sometimes bloody diarrhoea
How is the diagnosis of giardia made?
What is the treatment?
What is disease control?
Cysts are detected in stool
Treated with TINIDAZOLE
Disease control is by clean water and sewage treatment
Reinfection is common (no immunity development)
What is Toxoplasmia gondii?
An obligate intracellular parasite that is very common in cats
What does toxoplasmia gondii infect?
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
How is Toxoplasma gondii spread?
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.
How long does infection last?
What are the symptoms?
Infection persists for life and is ASYMPTOMATIC except for in immunocompromised individuals where it can cause ocular disease and CNS lesios
What kind of infection is the problem for?
Infection congenitally can be very serious
What is the risk to the mother and child (pregnacy) in toxoplasma gondii infection
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
What is the diagnosis method?
What is the treatment available for Toxoplasma gondii?
Describe Disease control
Diagnosis is by serology
Treatment is often not used (but can use Bactrim)
Disease control is avoidance of cats and cooking meat properly
