Eukaryotic Parasites 1 Flashcards
What is a parasite?
a plant or animal that lives on or in another living organism on which it is metabolically dependent
What are ectoparasites?
parasites which get metabolic benefit from interaction with cutaneous surface - most are insects such as lice or arachnids such as mites and ticks
What is the definitive host?
the host in which the parasite reaches sexual maturity
What is the intermediate host?
a host in which development occurs but the parasite does not reach sexual maturity
What is the paratenic host?
a host where the parasite does not undergo development
What is the reservoir host?
an animal that is infected with a parasite that also infects people
What are three species of lice?
pediculus humanis, p. capitis, phthirus pubis
What type of parasite are lice?
obligate blood sucking insect
What is an infection by live called?
pediculosis
What is the pediculus humanis?
A body louse that lives on body hair but lays eggs on clothing
What is the p. capitis?
A head louse - lays eggs at the base of hair stalks
What is p. pubis?
a pubic louse - can only attach and lady eggs on oval shaped hairs so can’t infect the head
What is the life cycle of p. capitis?
louse emerges from the egg, goes through malting, becomes sexually mature and reproduces and then lays eggs on the hair shaft - whole life cycle on the hair
What is irritant about lice?
Both the lice themselves and their malt
What is the distribution of lice?
worldwide
What is the treatment of lice?
topical insecticides
What is sarcoptes scabei?
A type of mite - causes scabies - an arachnid not an insect
Where do scabies typically infect?
They form tunnels in the epidermis of finger webs, elbows, axillae, genitals
How are scabies spread?
Contact
What is the life cycle of scabies?
adult females deposit eggs as they burrow, eggs hatch and release larvae, larvae malt and mature into adults to lay eggs again - eggs are transferred by scratching area around the burrow
What is the distribution of scabies?
worldwide
What is the treatment for scabies?
ivermectin or topical scabicides - and hot water wash clothing and bedding to avoid reinfection
Why are ticks important in disease?
Because they are a vector for many infectious diseases
What direct disease can ticks cause?
paralysis - either localised or generalised ascending
Are humans the natural host for ticks?
no
How is paralysis from ticks treated?
Removal of tick
What are protozoa?
Single cells organisms that are mainly non parasitic
Why are protozoa not truly parasitic?
because they can live outside the host
What are the two forms the protozoa exist as?
trophozoites and cysts
What is entamoeba histolytica?
an amoeba which invades the colon but can spread through the blood to the brain or liver and cause abscess
How is entamoeba transferred?
fecal-oral transmission - ingested as cysts
What is the distribution of entameoba histolytica?
worldwide - but unlikely in places with sewage treatment
What are the symptoms of infection by entameoba histolytica?
prolonged watery diarrhoea or may present as more acute bloody diarrhoea - or mate present with symptoms of abscess
What is the treatment for entameoba histolytica?
metronidozole and paromomycin and drainage of abscess
Do humans develop immunity to entameoba histolytica?
very little
What is giardia intestinalis?
a flagellate protozoa parasite that causes diarrhoea and malabsorption
How is giardia intestinalis spread?
Either via fecal-oral transmission or zoonotic transmission (e.g. possums contaminating rainwater tanks)
What is the distribution of giardia intestinalis?
worldwide
What is the treatment of giardia intestinalis?
tinidazole
How is giardia intestinalis diagnosed?
microscopy of faeces to look or cysts or serological test of feaces
Do humans develop an immunity to giardia intestinalis?
No
What is toxoplasma gondii?
an obligate intracellular parasite that can infect all mammals and many birds
What is the clinical presentation of toxoplasma gondii?
In people with a normal immune system there is insignificant presentation - mild cervical lymphadenopathy and mild fever that is self resolving
Who is at risk with a toxoplasma gondii infection?
immunocompromised patients - can cause CNS lesions or ocular disease and can be fatal
How do you get an infection with toxoplasma gondii?
usually from undercooked meat
How long does an infection of toxoplasma gondii last?
it is lifelong
In what animals do toxoplasma gondii sexually reproduce?
cats
Why should pregnant women avoid infection?
Because an acute infection during pregnancy can lead to miscarriage or foetal abnormalities
What is the distribution of toxoplasma gondii?
worldwide
What is the treatment of toxoplasma gondii?
In an immunocompromised patient use bactrim
