Ocular Parasites

Question 1

What are chlamydia

Answer 1

Small bacteria without a cell wall

Obligate intracellular bacteria that can only grow within eukaryotic host cell

Question 2

Onset and treatment of neonatal conjunctivitis

Answer 2

1 week

14d tetracycline

Question 3

How do chlamydia divide?

Answer 3

Binary fission

Question 4

What serotype of chlamydia causes trachoma? What amino acid do they require

Answer 4

A-C

REquire tryptophan

Question 5

What serotypes cause adult inclusion conjunctivitis

Answer 5

D-K

Question 6

What do serotypes L1, L2, L3 cause? What amino acid do they require

Answer 6

Lymphogranuloma venereum

Require methionine

Question 7

What is the infectious form of chlamydia trachomatis

Answer 7

Elemental body - infectious form attacehs to host cell

Enclosed in cytoplasmic vesicle inside the host cell

Spared lysosmal degradation

Question 8

What is the replicative form of chlamydia trachomatis

Answer 8

Reticulate body - forms after 6-8h inside host cell

Divides for 24h then returns to elemental form

Question 9

How is chalmydia diagnosed?

Answer 9

Giemsa staining

Identifies basophilic intracytoplasmic inclusion bodies

ISolated from swabs transported in sucrose phosphate and inoculated on to McCoy cells

ELISA to detect inclusions

Question 10

How is chalmydia treated?

Answer 10

Tetracycline
Erythromycin
Rifampicin
Asithromycin
Sulphonamides

Question 11

What are protozoa

Answer 11

Unicellular eukaryotic parasites

E.g. toxoplasma gondii, acanthamoeba

Question 12

What is toxoplasma gondii

Answer 12

Intracellular parasite
Host is cat

Question 13

How can toxoplasma be spread?

Answer 13

Faecal spread of sporocysts from cat host, ingestion of uncooked meats or inhalation
Vertical transmission

Question 14

What is the lifecycle of toxoplasma?

Answer 14

Conversion of asexuallyy produced merozites to gametoccytes in cat intestinal epithelium

Microgametes produce oocysts - ecreted in faeces and spore in soil

eggs become infective after spourlation and ingenstion by intermediate host

Ingested sporozoites develop into tachyzoites in intermediate host
Divide rapidly and travel to the lymph nodes in WBCs

Extraintestical spread to skeletal muscle, brain, heart, eye

Merozoites
Haemtocytes
Ooccysts
Sporozoites
Tachyzoites -infective form
Bradyzoites - tissue cyst latent form

Question 15

How is toxoplasma treated

Answer 15

Pyrimethamine
Sulphadiazine
Clindamycin

steroid therapy for ocular inflammation

Question 16

What is acanthamoeba

Answer 16

Protozoa found in public water, swimming pools, hot tubs, fresh water ponds, lakes, bottled mineral water, soil

Cause indolent cornea ulceration

Question 17

Who does acanthamoeba most commonly affect

Answer 17

Soft contact lens wearers

Question 18

How does acanthaemoeba keratitis occur

Answer 18

Amoeba attaches to epithlelial surface
Epithelial defect may assist in adherence - mannose binding lectin
Stromal changes due to collagenase activity

Question 19

What does acanthamoeba grow on?

Answer 19

Non-nutrient agar covered with killed E.coli

Question 20

What are the forms of acanthamoeba?

Answer 20

Active trophozoite
Domran encysted form

Question 21

What is treatment fo acathamoeba?

Answer 21

Long

Antiseptic biocides

Polyhexamethylene biguanide PHMB

chlorhexidne

Aminoglycocides
Diaminideines
Imidazoles

Question 22

What is the immmune response to helminth infection

Answer 22

Antibody prodcution
Complement activation
Marked type I hypersensitivity with IgE response, mast cell degranulation, eosinophilia

Question 23

What are classification of helminths

Answer 23

Trematodes - schistosoma
Cetodes - Taenia, Echinococcus
Nematodes - toxocara, filaria, onchocerce, trichinella

Question 24

What are schistosomes

Answer 24

Contracted from snails
Immature worms enter lugns and mature here before spreading haematogenously

Can cause a granulomatous reaction in the adenexae

Question 25

What cestodes can cause retinal detachemtn

Answer 25

TAenia solium From pork

Question 26

What cestodes can cause orbital proptosis

Answer 26

Echinococcus granulosus From dog faeces

Question 27

Causes of toxocarisis? What does toxocara cani cause

Answer 27

Toxocara cnis Toxocara cati Round worms Chorioretinitis and uveitis

Question 28

What antibody can be detected in acute phase of toxocara

Answer 28

IgM

Question 29

What is treatment of toxocara canis

Answer 29

Thiabendazole Albendazole

Question 30

How is corneal epithelium damaged by acanthaemoeba

Answer 30

Mannose induced protein - protease with collagenase activity - daamges corneal epithlium

Question 31

What are filaria

Answer 31

Thread like parasites Promote specific IgG and marked IgE

Question 32

What is onchocerciasis

Answer 32

River blindness Most frequent helminth opthahlmic infection

Question 33

What spreads onchocerciasis

Answer 33

Black fly Humans definitive host

Question 34

Life cycle of onchocerciasis

Answer 34

Microfilaria mature to infective larvae in black fly Bites human - larvae transferred to skin Haematogenous spread to eye - corneal and conj infectionW

Question 35

What is the inflammatory repsonse in onchocerciasis

Answer 35

Mazzotti reaction - infalmmation to dead or dying microfilarias

Question 36

How is onchocerciasis traeted?

Answer 36

Ivermectin

Question 37

How is onchocerciasis prevented?

Answer 37

Black fly eradication with DDT spraying of river basins

Question 38

What is Loa loa

Answer 38

TRansmitted by deer fly Can infect eye in microfilarial stage and mature into adult worm

Question 39

What occurs in trchinella spiralis

Answer 39

Ingestion of udnercooked meat LArvae infect EOM Painful granulomatous reaction IFnlammatory myositis Intraocular spread - retinal haemorrhages, subretinal lesions, papilloedema

Question 40

How long can onchocerciasis last in skin?

Answer 40

30 months