 SKIN
AND EYE PARASITES
NEMATODA Order: Filariata
ONCHOCERCA VOLVULUS
onco1-ic
Onchocerca volvulus:
life cycle.
onco2-ic
O.volvulus:
geographic distribution.
onchocerciasis occurs especially in Tropical Africa,
between the 15° north and the 13° south (high endemicity in B.Faso and
Ghana).
Foci are present in Southern Arabia, Yemen and in America
(Mexico, Guatemala, Colombia, Ecuador, Brazil, Venezuela).
(Adapted and redrawn from: Onchocerciasis
and its control,
WHO Technical Report Series, No. 852, 1992.)
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onc2a-ic |
onc2b-ic |
onc2c-ic |
Simulidos2-ic |
onc2a: The infection
is transmitted by several species
of black flies of the genus Simulium.
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onc2a:
Simulium spp.: Courtesy of Bayer, from Bayer Manual of Pest Control |
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Simulidos2:
Simulium
spp.:
Courtesy of Dr. Gustavo A. Gini:
Quimico-Biologo, Microbiologist,
Bacteriology Professor at University
of del Valle of Guatemala; Former Chief of Microbiology Department
and Director of School of Chemical Biology
University of San Carlos of Guatemala. |
onc2b: Larva
of
Simulium
onc2c: Pupae of Simulium
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onc2b and onc2c:Courtesy
of Emeritus Professor Wallace Peters |
onco3-ic
O.volvulus is
the agent responsible of the "river blindness"
due to the presence of microfilariae in the ocular structures;
other clinical manifestations include pruritic dermatitis
with lichenification and thickening of skin.
(Sections of adults).
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Skin1-ic |
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Skin2-ic |
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In
early infections a itchy, erythematous, papular rash is frequent.
During the late stage of the disease skin depigmentation (Leopard
skin)
and hyperkeratosis occur.
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Images:
Skin1-ic,
Skin2-ic:
Courtesy of Dr. Gustavo A. Gini:
Quimico-Biologo, Microbiologist,
Bacteriology Professor at University
of del Valle of Guatemala; Former
Chief of Microbiology Department
and Director of School of Chemical
Biology
University of San Carlos of
Guatemala. |
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onco4-ic |
onco4a-ic |
onco4: O.volvulus:
the larvae enter the host tissues,
and develop to adults in subcutaneous nodules in about 1 year.
Nodules are usually found in the upper part of the body in the american
onchocerchiasis and in the pelvic region in the african form.
(Section of an adult female).
onco4a: Nodules containing O.volvulus
on the head of a man in Guatemala
onco5-ic
O.volvulus:
adult females measure 45-50 cm by 300 µm,
males 20-40 mm by 200 µm. Adults live for 8-10 years in nodules.
Nodules are surrounded by concentric bands of fibrous tissue.
onco6-ic
O.volvulus:
females contain eggs and larvae in different stages of development.
Microfilariae measure between 200 x 6 and 300 x 8 µm
and survive for about 6 months in hosts tissues.
(Section of an adult containing microfilariae).
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onco7-ic |
onco7a-ic |
O.volvulus:
after being released by the adult female microfilariae
escape to the subcutaneous tissues and the eye
and can be recovered with blood-free skin snips.
(Wet mount preparation).
onco7a: Mirofilaria
of
Onchocerca volvulus in saline containin skin snip
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onco8-ic |
onco8a-ic |
Skinbiopsy-ic |
Skinfragment-ic |
onco8: O.volvulus:
diagnosis of onchocerciasis is obtained
by fresh examination of blood-free skin snips.
onco8a: Taking a skin
snip in the diagnosis of onchocerciasis.
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Skinbiopsy and
Skinfragment:
Courtesy of Dr. Gustavo A. Gini:
Quimico-Biologo, Microbiologist,
Bacteriology Professor at University
of del Valle of Guatemala; Former Chief of Microbiology Department
and Director of School of Chemical Biology
University of San Carlos of Guatemala. |
onco8b-ic
O.volvulus:
biopsies must be kept in saline for 1 to 3 hours
to allow migration of microfilariae.
onco8c-ic
O.volvulus:
microfilariae can be recovered in saline and identified
on the basis of shape and size.
(Fresh examination)
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onco9-ic |
onco9a-ic |
onco9:
O.volvulus: microfilariae must be differentiated from
microfilariae
of M.streptocerca and M.ozzardi. Microfilariae of O.volvulus
are longer and do not have nuclei to the end of the tail.
(Giemsa stain).
onco9a: Microfilaria of O.volvulus
(Giemsa stain, X 300)
onc10-ic
O.volvulus:
detail of microfilaria, cephalic space.
(Giemsa stain).
onco11-ic
O.volvulus:
detail of microfilaria, typical caudal space:
the nuclei do not extend to the tip of the tail.
(Giemsa stain).
onco12-es-ic
Onchocerca volvulus:
skin snip, microfilaria, (400 X).
Treatment
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Ivermectin, that causes paralysis of worms by interfering with
neural ion channels, is the drug of choice. Ivermectine doesn’t
kill the adult worm, but reduces the microfilarial load, thus
decreasing the risk of blindness and the progression of the
disease. Ivermectine is administered at 150 micrograms/kg (max 12
mg) every 6-12 months to suppress ocular and dermal microfilarae.
The treatment of endosymbionts bacteria (Wolbachia) with
doxycicline seems promising and an exciting new therapeutic
approaches for the treatment of filariasis (Science 2002;296:1365;
BMJ 2003;306:207; JID 2005;192:1483)
Surgical Care: with nodulectomy adult worms can be surgically
removed; removal of all subcutaneous nodules may be curative but
not all nodules can be find. |
Guatemala: sequence of nodulectomy
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Yepocapa |
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| 10_noduloextraido |
11_nodulos |
12_adultosnodulos |
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Sequence of nodulectomy:
Courtesy of Dr. Gustavo A. Gini:
Quimico-Biologo, Microbiologist,
Bacteriology Professor at University
of del Valle of Guatemala; Former Chief of Microbiology Department
and Director of School of Chemical Biology
University of San Carlos of Guatemala. |
SKIN.... EYE....
 
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