M: Parasitic Infections of the Eye - Week 10 Flashcards
Name 5 situations where you might suspect parasites in the eye/appendages
- infections in contact lens uses: that aren’t responding to antibiotics
- immunocompromised person
- returned traveler/migrant from developing country
- zoonosis: contact with animals (esp. faeces)
- sexual partner has similar/other genital lesions
How might a travelling person acquire parasites? Name 3 ways
- bitten by insects
- swam in rivers/lakes
- consumed ‘exotic’/raw/undercooked food (frogs, snakes, seafood)
Define parasitism
a living organism (parasite) living on/in another living organism (host), causing harm to the host
Define commensalism
an association between two organisms in which one benefits and the other derives neither benefit nor harm.
Define symbiosis
interaction between two different organisms living in close physical association, typically to the advantage of both.
What kingdom to parasites belong to?
Animal kingdom
How can parasites be broadly classified?
As unicellular or multicellular
What are unicellular parasites called? What are multicellular parasites called?
unicellular = Protozoa. multicellular = Metazoa
What 2 categories can we classify metazoa?
- Helminths (worms)
- Arthopods (insects)
In what 5 categories can we classify protozoa?
- Amoeba
- Flagellates
- Cilliates
- Sporozoa
- Microsporidia
In what 2 broad categories can we classify helminths?
- Platyhelminths (flat worms)
- Nematohelminths (round worms) (i.e. nematodes)
In what 2 categories can we classify platyhelminths?
- Trematodes (leaf shaped)
- Cestodes (tape shaped)
Define the following: A: Definitive host B: Intermediate host C: Incidental/Accidental host D: Reservoir/Natural host
A: carries adult or sexual stage of parasite
B: carries all or part of larval or asexual stage of parasite. Sometimes,2 intermediate hosts
C: host is not necessary for parasite’s survival. In fact it is a ‘dead end’ for parasite
D: other animals which normally harbour the parasite and are part of life cycle
What is a Vector? What forms can it be in? (2)
A vector is one of two hosts. Usually an arthropod.
it may be:
- biological (in which part of life cycle is passed), or
- mechanical (life cycle not passed)
In what 2 categories can we classify Arthropods (in the eye)?
- Ectoparasites
- Vectors
Name 4 Ectoparasites (that can colonise the eye). And name the conditions they are associated with (4)
- Itch mite (scabies)
- Mite (demodex)
- Pubic lice (“crabs”)
- Fly larvae (ophthalmomylasis)
Name 5 vectors. And name the parasites they transmit [in brackets] (5)
- Sandflies (leishmania)
- Tse-tsefly (trypanasome)
- Deerfly (Loa Loa)
- Blackfly (onchocerca)
- Fleas/ticks/mosquito (filarial worms)
List 4 ways a parasitic infection of the lids can present
- swelling
- cysts
- distorted eyelids
- crusted lesions
List 1 way a parasitic infection of the following areas present:
- cornea
- conjunctiva
- lacrimal gland
- optic nerve
- retina/choroid
- keratitis
- conjunctivitis
- davryocystitis
- neuritis
- retinoscope-choroiditis
List 2 ways a parasitic infection of the orbit can present
- cyst
- nodule
Name 6 parasites that can affect the eyelid
- Leishmania
- Taenia cysticercosis
- Spirometra
- Pubic lice (‘crabs’)
- Sarcoptes scabei
- Demodex
(also - ‘bot’ fly)
Name 4 parasites that can affect the cornea
- acanthamoeba
- microsporidia
- leishmania
- trypanosoma
Name 5 parasites that can affect the conjunctiva
- microsporidia
- leishmania
- ‘bot’ fly
- loa loa
- animal filarial worms
Name 2 parasites that can affect the lacrimal gland
- Schistosoma
- Cysticercosis
Name 1 parasite that can affect the optic nerve
- gnathostoma
Name 5 parasites that can affect the retina/choroid
- toxoplasma
- toxocara
- angiostrongylus
- onchocerca
- pneumocystis
Name 3 parasites that can affect the orbit
- taenia cysticercosis
- hydatid cyst
- trichenella
For Acanthamoeba species of parasite, describe the following:
A: Describe it. What does it infect?
B: Transmission
C: Diagnosis (2)
A: a soil amoeba - infects cornea B: contamination due to poor lens hygeine C: - demo of amoeba in corneal scrapings - culture on non-nutrient agar
For Acanthamoeba species of parasite, describe the following:
- list 4 symptoms
- irritation of eye, pain, photophobia
- blurring of vision – blindness
- conjunctivitis
- complications like ulceration, bacterial infection
For Acanthamoeba species of parasite, describe the following:
- list treatment options (2)
- surgical debridement with/without keratoplasty (surgery if severe)
- complex medical topical therapy
How easily can we get rid of acanthamoeba?
Very difficult to get rid of. The longer you wait, the more difficult it is to treat
Name 2 other soil amoeba we can encounter as contaminants. How do we differentiate these from acanthamoeba? (2)
- calpoda sp., and hartmanella sp.
Diagnosis: - demo of amoeba from CL or CL-case or fluid (differentiated on morphology)
- PCR may be available in some reference labs
How do we manage the 2 other soil amoeba that we can encounter as contaminants? (2)
- nil treatment for patient (i.e. no treatment)
- change lens, attention to cleaning
For Toxoplasma gondii, describe the following:
A: describe it.
B: Transmission (2)
A: a small intracellular protozoa
B:
- contact with cats (esp. kittens) - definitive host
- eating undercooked meat (many species of animals act as intermediate hosts)
For Toxoplasma gondii, describe the following:
A: List the 2 clinical presentations and explain them
- congenital: severe fetal disease, chorioretinitis
2. acquired: usually asymptomatic in the eye of immunocompetent people. Can reactivate if immunocompromised
Which presentation of toxoplasma gondii infection is more common?
acquired
How long may cysts last in immunocompetent people with toxoplasma gondii infection?
cysts may persist for life
What is the primary source of infection of toxoplasma gondii in people who are immunocompromised?
transplant
What proportion of the australian population is infected with toxoplasma gondii?
30-50%
For Toxoplasma gondii, describe the following:
- list 5 means of diagnosis
- serology: demo of antibodies in serum (expect rise in titre of IgG and IgM)
- histopathology of tissue
- culture: tedious, not routine
- PCR: tissue or vitreous
- if foetal infection: PCR on amniotic fluid/foetal blood
What is the main diagnostic test used for toxoplasma gondii?
PCR
For Toxoplasma gondii, describe the following:
- list treatment options (3)
For foetal infection:
- termination of fetus (esp. if 1 or 2 trimesters)
- spiramycin to mother (difficult to get)
For reactivated disease:
- pyrimethamine + sulfadiazine + prednisolone
In regards to Taenia solium, describe the following:
A: describe the parasite
B: transmission
C: diagnosis (2)
A: pig tape worm
B: ingestion of eggs shed by human tapeworm carrier
C: a combination of radiology + serology. Also FNA for histopathology or antigen detection
In regards to Taenia solium, describe the following:
- treatment (2)
depending on location of lesion, treatment is either surgical and/or treatment with praziquantel or albendazole + steroids
In regards to Taenia solium, describe the following:
- clinical presentation (3)
- usually in skeletal muscles with no symptoms
- eyes rarely involved: if involved - scotoma, or space occupying lesion (SOL) or cyst
What might you see on a scan of the orbital tissues in a person with ocular cysticercosis?
White spots, which are ocular cysts. The more white spots the more severe it is
In regards to Toxocara canis, describe the following:
A: describe the parasite
B: transmission
C: diagnosis (2)
A: a dog round worm
B: accidental infection by larvae entering through skin and deposit in CNS or eye or other tissue
C: serology or FNA for histopath or antigen detection
In regards to Toxocara canis, describe the following:
- clinical presentation (3)
- severity depends on site
- retino-choroiditis (ocular larva migrans) – nastiest form
- granuloma resembling tumour
In regards to Toxocara canis, describe the following:
- treatment (2)
depending on location of lesion, treatment is either conservative/symptomatic. If near the macula, treatment with anti-parasitic drugs + steroids is required
Name the 2 most common filarial worm of canids
- Dirofilaria immitis (most common)
- Acanthocheilonema reconditum
Name 1 way that ocular larva migrans can present
diffuse unilateral subacute neuroretiniits
How common are accidental infections in humans? Other animals?
uncommon in humans. More common in other animals
In regards to Phthirus pubis, describe the following:
A: describe the parasite
B: transmission
C: diagnosis
A: an arthropod - infests pubic, axillary, truncal hair and eyelashes
B: person to person by direct physical contact (STI)
C: demonstration of lice or eggs (stuck to hair)
In regards to Phthirus pubis, describe the following:
D: list 2 symptoms
E: list 3 treatment options
D: pruritis, macules/papules with excoriation
E:
- 1% permethrin to all hair bearing areas (except eyes)
- eyelashes: remove with forceps
- clothes, bed linen: hot wash
In regards to Demodex folliculorum or D.brevis, describe the following:
A: describe the parasite
B: transmission
C: diagnosis
A: an arthropod (eyelash mite)
B: person to person, autoinfection: numbers increase with age - infects skin (mainly face) and eyelashes
C: demo of mite in skin scrapings or biopsy
In regards to Demodex folliculorum or D.brevis, describe the following:
- list 4 clinical presentations
- folliculitis
- blepharitis (anterior or posterior)
- blepharo-conjunctivitis
- corneal lesions
In regards to Demodex folliculorum or D.brevis, describe the following:
- treatment options (3)
- topical teatree oil/ointment (for skin only)
- ivermectin single dose (12ug)
- Oral doxcycyclin for 2ndary bacteria (symbiotic/infection)
In what age group does demodex folliculorum or D.brevis usually occur?
Usually in older people
In regards to Sarcoptes scabei, describe the following:
A: describe the parasite
B: transmission (2)
C: diagnosis (3)
A: an arthropod (itch mite) - infects skin
B: person to person (poor hygeine) or by sexual contact
C: demo of mite, eggs or faecal pellets
In regards to Sarcoptes scabei, describe the following:
D: list symptoms (3)
- severe pruritis
- erythematous papules
- crusted nodules and plaques
In regards to Sarcoptes scabei, describe the following:
E: treatment (4)
- topical 5% permethrin from head to sole, repeat (not on face or eyes)
- Ivermectin is to be taken orally
- also treat close contacts and
- hot wash clothes and bed linen
