MIIM - Parasites Causing Ocular Infections - Week 10 Flashcards
In what 5 situations would you suspect parasites in the eye/appendages? Explain each if applicable (6).
Infection in contact lens users
- not responding to antibiotics
- poor/doubtful CL hygiene
Immunocompromised patients
-malignancy, HIV, steroids etc
Returning traveller/migrant from a developing country
- insect bites
- swam in a river/lake
- consumed exotic raw/undercooked food
zoonosis: contact with animals/faeces
- poor/doubtful hygiene
Sexual partner has similar lesions (including around the genitals)
Define parasitism.
A living organism living in/on another living organism, gaining benefit at the expense of the host.
Define commensalism.
Living in/on a host with no harm to the host.
Define symbiosis.
Two mutual orgnaisms gaining benefit from one another, where both are dependent on one another.
Are parasites necessarily micro-organisms?
No, they can be in the animal kingdom as well.
Briefly describe the classification of parasites, including uni/multicellular forms (3).
Unicellular - protozoa
Multicellular - metazoa
-helminths (worms)
-arthropods (insects)
Define definitive host.
Carrier of adult or sexual stage of the parasite
Define intermediate host.
Carrier of all or part of the larval or asexual stage of the parasite
Can there be multiple intermediate hosts or is the limit just one?
Sometimes there are two
Define incidental/accidental host.
Host is not necessarily for the parasite’s survival
Define reservoir/natural host.
Animals which normally harbour the parasite and are part of its life-cycle
Define the two types of vectors.
Biological - in which part of the life cycle is passed
Mechanical - life cycle is not passed
What are the usual vectors for parasites?
Arthropods
What is the taxonomy of acanthamoeba?
Unicellular protozoa - a soil amoeba.
What structure of the eye does acanthamoeba infect?
The cornea
How is acanthamoeba transmitted?
Poor contact lens hygiene
Name 5 symptoms of an acanthamoeba infection.
Irritation Pain Photophobia Blurry vision (leading to blindness) Conjunctivitis
Name two secondary complications of an acanthamoeba infection.
Ulceration
Bacterial infection
What are two ways to diagnose an acanthamoeba infection (laboratory)?
Demo of amoeba in corneal scrapings
Culture on non-nutrient agar
In what two ways can an acanthamoeba infection be treated (3)?
Surgical debridement ± keratoplasty
Complex medical topical therapy
Do all amoeba cause keratitis?
No
Do all amoeba infection require extensive surgical care?
No, some just require changing lens and paying more attention to CL hygiene.
What is the taxonomy of toxoplasma gondii?
A small intracellular protozoa
How is toxoplasma gondii transmitted (2)?
Contact with cats, especially kittens
Eating undercooked meat
