a chronic parasitic disease
filarial nematode Onchocerca volvulus.
multiple organ systems
cutaneous and ophthalmologic
multiple organ systems
primarily affects people living near fast-
flowing rivers where blackflies breed.
Africa, Central and South America, and the
~ 18 million people are currently infected.
Of those infected:-
◦ about 1.5% are blind,
◦ additional 2.8% have severe visual
◦ Greater morbidity with age is the result of cumulative
exposure in endemic areas.
◦ Blindness tends to occur in adulthood after many
years of infection.
humans are the only definitive hosts.
Simulium black flies - obligate intermediate
The species Simulium damnosum in africa
African Simulium species tend to bite the ribs,
hips, iliac crests and lower limbs,
Female worm length ranges from 30-80
Male adult worms are usually 3-5 cm in
migrate between various subcutaneous
nodules to inseminate females.
life span of up to 14 years for adults
MF live for 6-30 months;
the female worms produce 1000-3000 MF daily.
can migrate throughout the subcutaneous tissues
they have a particular affinity for ocular tissues.
most die without completing their life cycle.
with heavy infection, as many as 100,000 MF die each
The predominant immune response is production of
antibodies against dead/dying MF
LIFE CYCLELIFE CYCLE
Blackflies bite an individual infected with O.volvulus.
Fly saliva acts as a chemoattractant for microfilariae in
the surrounding subcutaneous tissues
The microfilariae develope in the thoracic muscles
within the blackfly,
in a 2- to 3-week period they become infective-stage
fully develop in the labium of the proboscis of the fly
which passes larvae to another human when taking a
In the human host, the larvae developesto male and
female adult worms
years after initial infection.
initial bite go unnoticed.
A 1- to 2-year latent period afer initial bite
Pruritus is the most common early symptom
Lymphadenopathy inguinal and femoral regions→ .
Subcutaneous nodules → (onchocercomata)
Visual symptoms itching, redness, photophobia, and→
vision loss and frank→ blindness
range from early mild inflammatory lesions to chronic
debilitating cutaneous and ophthalmic lesions.
◦ refers to the various cutaneous findings
◦ classified into 6 diseases
1. Acute papular onchodermatitis (APOD)
2. Chronic papular onchodermatitis (CPOD)
3. Lichenified onchodermatitis (LOD)
ACUTE PAPULAR DERMATITISACUTE PAPULAR DERMATITIS
Widespread small pruritic papules that may
progress to vesicles and/or pustules in the most
There may be associated erythema and edema.
most often involves the face, shoulders, trunk, and
CHRONIC PAPULAR DERMATITISCHRONIC PAPULAR DERMATITIS
Larger (3 to 9 mm in diam.), flat-topped,
lichenoid papules distributed
Pruritus is common
may be present.
hyperpigmented papules, regional
lymphadenopathy, and edema
The most commonly affected anatomic
areas are the buttocks, shoulders, and
LICHENIFIED ONCHODERMATITISLICHENIFIED ONCHODERMATITIS
an intensely pruritic dermatitis
excoriations and hyperpigmented and hyperkeratotic
papules and plaques.
Become lichenified in time
The plaques have an asymmetric distribution
lower extremity is the most commonly affected
There is often associated lymphadenopathy.
Atrophy, also known as “lizard skin”
degeneration of elastic fibers and other
structural elements of the skin due to
The skin appears wrinkled and thin
most commonly the buttocks and, less
commonly, the extremities.
It may develop after any of the patterns
described previously, or arise de novo.
is also known as “leopard skin.”
common finding in advanced onchocerciasis.
lesions resemble vitiligo
is ass. with perifollicular pigmentation
Pruritus is rarely seen
commonly found on the shins bilaterally.
useful method to screen for onchocerciasis in
Less commonly the buttocks, lateral groin,
and lower abdomen are involved.
Palpable onchocercal nodules containing the
involve the deep dermis and subcutaneous
are typically asymptomatic
occur over bony prominences such as
◦ the skull, -iliac crest,
◦ knee, -rib,
◦ sacrum, -scapula
OCULAR FINDINGSOCULAR FINDINGS
◦ MF enter the eye by direct invasion from the
conjunctiva into the sclera or cornea.
◦ inflammatory responses to MF
◦ intense host immune inflammatory reaction
◦ intensifies when MF die.
◦ causes the following ocular findings, which are
dermatitis, subcutaneous nodules, or ocular lesions.
Peripheral eosinophilia and elevated IgE levels are
Identification of the MF in a skin snip (100% specific)
6 samples are usually obtained: 1 from each scapula,
iliac crest, and lateral calf
Demonstration of adult worms in an excised nodule.
Free floating MF can easily be seen in the anterior
chamber of the eye on slit- lamp examination.
◦ Performed when infection is suspected and skin snip test results are
◦ 6 mg of DEC is administered
◦ Pt. observed for development of pruritus with or without erythema
◦ indicates the death of microfilariae in the skin.
◦ The reaction may occur from 15 minutes to 24 hours after DEC
◦ Severe reactions may occur in both the skin and the eyes, and other
adverse effects include vomiting, conjunctivitis, hypotension, and
DEC patch test
◦ A mixture of 10% DEC and Nivea cream is applied under an occlusive
◦ the occurrence of a localized inflammatory response indicates a
positive test result.
◦ This test is a safer alternative to the Mazzotti test.
◦ sensitivity is 30-80%.
Microscopic examination of excised
cross-sections of adult worms and a
collection of eosinophils and lymphocytes
at the periphery of the nodule.
and sometimes giant cells tend to
accumulate around the worms.
Calcification may also be seen
The current mainstay of treatment is
Mass treatment campaigns (WHO)
◦ ivermectin is a microfilaricide
◦ and does not kill adult worms,
◦ does not cure the disease.
◦ significantly reduces microfilarial burden
◦ decreases transmission and
◦ 150 mcg/kg/d PO as single dose q6-12mo
◦ administered for the life span of the adult worm.
Doxycycline 100 mg/d administered
for 6-8 weeks
targets bacteria of the Wolbachia
species, known endosymbionts in
Reduces microfilarial loads,
sterilizes adult worms,
decreases adult worm viability.
Diethyl carbamazine kills the MF and is
given as follows:-
first 3 days 1mg/kg body weight once;
Next 4 days 2mg/kg body weight once;
second week 4mg/kg body weight three
times a day;
third week 4mg/kg body weight three
times a day.
In heavily infected patients,
or in those with severe dermatitis
or with eye involvement,
prednisone 40mg should be given at a daily
dose in adults, starting the day before DEC and
continuing for a few days until the reaction has
Ocular reactions need treatment with
corticosteroid eye drops and mydriatics.
◦ Extremely toxic
◦ in selected individuals for curative treatment of severe hyperreactive
onchodermatitis uncontrolled by repeated ivermectin treatment.
◦ is a drug that kills adult worms and MF
◦ Parenteral/IV: >60 kg: 0.2 g week 1; 0.4 g week 2; 0.6 g week 3; 0.8 g
week 4; 1 g week 5 and 6; total dose 4 g
nodulectomy, usually combined with a microfilaricide.
◦ larvicides to reduce the black fly population.
Mass treatment with ivermectin
◦ is employed in areas of high endemicity
◦ reduces the microfilarial burden in the
Education of people in endemic areas