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Tropical Ophthalmology. Part Three of Three

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1 Tropical Ophthalmology. Part Three of Three
Dr. Steve Waller Uniformed Services University of Health Sciences Bethesda, Maryland, USA

2 Unusual tropical eye diseases
Not commonly found in U.S., even in teaching hospitals Five examples: atypical tuberculosis (TB) leprosy manzanillo keratopathy loa loa conjunctivitis tarantula keratopathy

3 Atypical TB after LASIK or transplant, steroid gtts
incidence resurging Large bacterial corneal ulcer with anterior chamber purulent hypopyon gtts = eyedrops

4 Leprosy neurotrophic cornea entropion
can have uveitis in lepromatous disease Upper left: inturned lashes (entropion) causing corneal scarring Middle: classic ‘leonine facies’ with lid and facial droop from neuromuscular atrophy Upper right: insensate (neurotrophic) cornea with sterile ulcer from absence of blink reflex. Lower right: infection in neurotrophic eye Lepromatous is multi-bacillary form; tuberculoid is pauci-bacillary

5 Manzanillo tree sap keratopathy
Manzanillo or “beach apple” tree common to Caribbean, east coast of Florida Sap is milky latex vesicant known for delayed dermal effects; folk medicine for conjunctivitis Acute ocular effects first described in US troops during WWII Other natural blistering agents: cantharidine (beetle) – no known antidote poison ivy/oak podophyllum (mandrake root)

6 case seen in military hospital in San Antonio
Scarring and fine vessels around peripheral cornea due to past manzanillo sap exposure. Not likely to progress or disable patient in future.

7 Vesicant toxicity to cornea
Mustard gas: alkylation crosslinks DNA and denatures protein clinical effect: cornea edema ischemia secondary melt or ulcer World War I scene, France Main toxicity in WWI France was pulmonary, with secondary pneumonia often fatal in pre-antibiotic era. Small number of English soldiers were blinded; vast majority recovered with no disability. Some rural areas of France were quarantined for decades after mustard exposure.

8 Loa loa: the “eye worm” Filarial nematode of West and Central Africa
mango fly (Chrysops), bites at dawn/dusk 20 million infected, >30% in hyperendemic areas adult worms live for 20 years, up to 60 mm long subcutaneous or subconjunctival migration “Calabar swelling” from allergic angioedema (named for eastern Nigeria seaport) Another reason to cover your arms and legs at dawn and dusk in the tropics! Photo shows sub-conjunctival adult worm in west African patient. Worm is active and movement is painful. Calabar is port in eastern Nigeria, ancient and tied to slave trade

9 Manifestations and life cycle
pruritis, skin tracks fever meningitis larvae travel in vessels mango fly stages 1-4 years to mature

10 Prevention, Diagnosis, Treatment
Prevention: avoid vector contact, apply insecticide to mango groves Diagnosis: clinical or find microfilariae on Wright or Giemsa stains of daytime blood Treatment: surgery, ivermectin*, albendazole*, mebendazole* * off label use All three medications are broad-spectrum antihelminthics, but there is no FDA recommendation in their product inserts for use in cases of loa loa opthalmic or systemic disease.

11 Excision of subconjunctival loa loa worm
Left photo: adult excised from under conjunctiva under local anestesia Worm is about 5 cm (2”) long

12 Tarantula keratopathy
Uriticating hairs - dorsal abdomen ‘Cloud’ of hairs easily rubbed off

13 diagnose  by history of exposure and pain without  inflammation
fine barbed hairs in cornea, can migrate to retina Barbed hairs make one-way trip into eye, can cause local inflammation in posterior segment of eye

14 Zoonotic eye diseases Preferred host is non-human
Paratenic (dead-end) visit by parasite, but damage still done! Two examples: Toxocara vitreoretinopathy orbital myiasis

15 Ocular larva migrans (Toxocara canis or cati)
Worldwide distribution Risk factor: exposure to canine/feline feces sandbox is infective up to one year after feces deposited

16 Toxocara life cycle adults in canine intestine fecal contact by human
eggs hatch in GI tract migrate in blood vessels exits at end organ brain, eye liver lungs

17 Manifestations Visceral larva migrans Ocular larva migrans Treatment
Uveitis, hypopyon Macular / peripheral granuloma Vascular occlusive disease Treatment Steroids, laser if larva alive Value of antihelminthics unclear

18 Myiasis Infestation of tissue or cavities by maggot (Diptera)
Internal: subretinal migratory tracks External: lids or conjunctiva Orbital: debilitated patient, abscess Treatment is excision

19 Photo essay: anterior orbital myiasis caused by human botfly (Dermatobia hominis).
Goodman RL, Montalvo MA, Reed JB, Scribbick FW, McHugh CP, Beatty RL, Aviles R. Arch Ophthalmol Jul;118(7):

20 Dermatobia hominis AKA human botfly, torsalo (Central America), ‘beef worm’ (Belize), ‘mosquito worm’ Habitat: forests and river valleys in Latin America, imported to USA case in Dallas County, TX, 2003 Hosts: man, cattle, dogs, birds

21 Dermatobia hominis Life cycle of 3-4 months
Female attaches eggs to a fly, mosquito, or (rarely) tick, who then transmit to egg to human host 1mm ‘bot’ hatch, enter host at bite grows over 6-12 weeks to 20 mm Mature larvae exit furuncle opening, drops to ground, pupates for days Adult does not eat, mates within one day, and lives only one week

22 Larva Furuncular myiasis: movement often observed within opening
Two oral hooks at distal end, two dark respiratory ‘spiracles’ near skin break Adult fly: ½”, yellow, resembles a bee

23 Ophthalmomyiasis externa
Treatment: Occlude breathing tube with beeswax, gum, ointment, fat, drop of nicotine Excision Subretinal larva: argon laser Real Texas cowboys just spit a little chewin’ twobacky on the breathin’ hole….

24 Iatrogenic Diseases Rabies in corneal transplant
Most recent case - Iran, 1996 8 reported cases (one US case in 1979) implications for regulation and eye banking in developed and developing world In November 2011, I could only find 8 reported cases of transplanted rabies in literature. Oregon case from 1979, France 1980, Thailand 1981, India 1990’s and Iran 1996.

25 Acanthamoeba Keratitis
Ubiquitous, warm water Homemade contact lens solutions and hot tubs Chronic pain and ulcer Medications (all off label use): Brolene (0.1% propamidine), PHBG 0.02% , neomycin, miconazole, others Photo: Esmeraldas province, Ecuador Brolene not available in US, except from CDC on humanitarian need basis. PHBG (polyhexabiguanide) is a swimming pool cleaning chemical, both though an appropriate pool store and filtered/diluted for ophthalmic use. Neomycin and miconazole are diluted forms of IV solutions. None of these medications has FDA product insert recommendation for use in amoebic keratitis.

26 trophozoite and cyst Upper left is schematic of active form (trophozoite) and cysts; lower left is electron microscope photo of cysts. Right hand photo shows trophozoites migrating across microbiology plate of non-nutrient agar and E. coli, the classic positive lab finding.

27 clinical appearance Upper photo shows stromal infiltate in upper 2/3rds of cornea and adjacent scleral inflammation Lower left photo shows classic ring infiltrate but no scleral involvement Lower right photo shows post-op corneal transplant, enlarged nearly to sclera in effort to capture entire infection. Sutures and incision near sclera and its vascular supply greatly increase risk of transplant rejection.

28 Signs and symptoms radial keratoneuritis: infiltrate along
radial corneal nerves Amoeba use nerves as ‘highway’ to migrate within stroma – apparent cause of pain and inflammatory neuritis pain out of proportion to findings paracentral ring infiltrate prior medical failure or diagnosis of HSV

29 Working Together International partnerships are key!
Address the cultural gap in research Common understanding of disease Common understanding of ‘science’

30 The good news Increasing access to eye surgery
Inexpensive intraocular lenses now available worldwide Ivermectin and the UN’s Onchocerciasis Control Program Improving nutrition Increasing opportunities for service

31 Summary Epidemiology: still much needless suffering around the world
Synergy: culture and disease Environment: protection is affordable Exotics: rare but important Iatrogenics: preventable The future is bright Taj Mahal from downriver

32 Questions? Sandanista monument in Managua Go to Part I of this lecture
Go to Part I of this lecture Go to Part II of this lecture

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