The patient is a native of Kenya who recently spent 9 months in Croatia and presents with progressively decreased vision in the left eye over 3 weeks. Exam finds eczematoid dermatitis and hypopigmentation of the legs with sclerosing keratitis of the left cornea. Labs show 90% eosinophilia. The document discusses onchocerciasis, caused by the filarial nematode Onchocerca volvulus transmitted by blackflies in equatorial Africa and other regions. Clinical manifestations include skin lesions, subcutaneous nodules, and eye involvement that can lead to blindness. Diagnosis involves skin snip biopsy and treatment is diethylcarbamazine or ivermectin

1. HX
●3 wk hx/o progressively decreased visual
acuity OS
●Intense puritius X 2 months
●Native Kenya from RURAL region near
running water
●In Croatia X 9 mo’s

2. Exam/Laboratory
●Eczematoid dermatitis and
hypopigmentation over legs
●Sclerosing keratitis of inferior temporal
quadrant cornea OS
●Visual Acuity 20/20 OD & 20/200 OS
●90% Eosinophilia on peripheral smear

3. Onchocerciasis
Frank Meissner, LtCol, USAF, MC, FS
Emergency Medicine

4. The fact that illness is associated
with the poor-who are, from the
perspective of the privileged,
aliens in one's midst-reinforces
the association of illness with the
foreign: with an exotic, often
primitive place.
Susan Sontag

5. Biology
●Onchocerca volvulus - Causative Agent
●TISSUE dwelling parasite- filarial
nematode
●Family Onchocercidae

6. Epidemiology
●Equatorial Africa
●Elevated regions of Mexico and
Guatemala
●Smaller foci in Saudi Arabia, Yemen,
Brazil, Ecuador, and Venezuela

7. Pathology
●Adult worms reside in subcutaneous
tissues
●Often enclosed in fibrous nodules
●Microfilariae, which in this species lack
an enveloping sheath
●Released from female adults
●Localize in skin and subcutaneous
tissues

8. Clinical Features I
●Skin is frequently involved
●Pruritus most common clinical
manifestation
●Wrinkling and skin atrophy

9. Clinical Features II
●Hypopigmentation or hyperpigmentation
●Papulovesicular lesions & localized
areas of eczematoid dermatitis
●Firm, nontender subcutaneous nodules
(over boney prominences)

10. Clinical Findings III
●Blindness most feared complication
●1.5K per 100K (endemic region) vs .25K
per 100K (base risk)
●Some areas 10% of adult population
blinded
●Conjunctivitis with photophobia
●Common and earliest finding

11. Clinical Findings IV
●Punctate keratitis (10-15%)
(accumulation of inflammatory cells
around dying microfilariae) usually no
sequlae
●Sclerosing keratitis (5%) and
chorioretinal lesions (5%) cause
blindness
●Anterior uveitis, iridocyclitis (5%) and

12. Vector
●Simulium species (blackflies)
●Simulium damnosum (major African
vector)
●No reservior host
●Estimated 30 million infected in Africa

13. Laboratory Diagnosis I
●Small piece of superficial skin obtained
by excision or punch biopsy weighed
●Incubated for several hours in saline or
tissue culture media
●Microfilariae that exit the skin are then
counted in the fluid
●Count of more than 100 microfilariae
per milligram of skin= heavy infection

14. Laboratory Diagnosis II
●50 mg provocative dose of
diethylcarbamazine
●Subsequent onset of symptoms, which
include pruritus, rash, fever, and
conjunctivitis= Mazzotti reaction
●Eosinophilia is often prominent during
onchocerciasis

15. Treatment I
●Diethylcarbamazine (DEC) 2 wks of 3 to
4 mg/(kg*day) in 2 divided doses
●25 mg test dose prior to giving
theraputic dose
●Pretreatment of patient with
corticosteroids and ASA reduce somatic
side-effects
●Microfilaricidal agent ONLY
●Leads to symptomatic improvement and

16. Treatment II
●Ivermectin, given orally in a single dose
of 150 mg/kg
●This dose is repeated every six to 12
months
●Nodulectomy for large nodules (remove
the adult worms)

17. Life Cycle I
●INNOCULATION by the bite of female
blackfly
●Infective larvae develope into adult
worms
●Coil into spherical bundles with 2-3
females + one to two males
●Gravid females release microfiliariae

18. Life Cycle II
●Microfiliariae migrate to host tissues
(esp dermis)
●Transmission intitiated by bite of fly onto
infected individual
●Microfiliariae migrate to BlackFly
thoracic muscles and become larvae
(6-8 d’s)
●Larvae migrate to head of fly and cycle

19. Conclusions
●Geographic Medicine NOT Tropical
Medicine
●Modern aircraft and mobile patients
make these diagnosises to consider
●Knowledge of parasitic infections
important

20. Meissner 6 W’s- ID Hx/o
●WHERE & WHEN? (travel history)
●You did WHAT WITH WHO, WHERE ?!!!!!!!!
(sexual history)
●WACKY WAYS to WASTE time?
(avocational/occupational history)
●WEIRD and non-WEIRD WILDLIFE?
(Zoonoses)
●Wolfing WHAT? (food and ingestion history)
●WEAK-knead WIMP