Tropical Ophthalmology. Part Three of Three

1. Tropical Ophthalmology.Part Three of Three Dr. Steve Waller UniformedServicesUniversity of HealthSciences Bethesda, Maryland, USA stephen.waller@usuhs.mil

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

4. Leprosy • neurotrophic cornea • entropion • can have uveitis in lepromatous disease

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

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

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)

9. Manifestationsand 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

11. Excision of subconjunctival loa loa worm

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

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 • 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

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 15-30 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 14-24 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

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

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

26. trophozoite and cyst

27. clinical appearance

28. Signs and symptoms radial keratoneuritis: infiltrate along radial corneal nerves • 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

32. Questions? stephen.waller@usuhs.mil