1.
Onchocerca volvulus
• Kingdom: Animalia
• Phylum: Nematoda
• Class: Secernentea
• Order: Spirurida
• Family: Onchocercidae
• Genus: Onchocerca
• Species: Onchocerca volvulus

2.
Onchocerca volvulus
(The convoluted filaria)
• It is common in parts of tropical Africa and Central
America.
• Habitat: nodules in the subcutaneous tissue of
man.

3.
Morphology
• Adult worms are white, opalescent and
transparent with transverse striations on the
cuticle.
• Male measures 1.9-4.2 cm in length and has
coiled tail.
• The female is much longer,
measuring 33.5-50 cm in
length.
O. volvulus microfilaria: unsheathed with no nuclei
in the end of long pointed tail.

4.
Life cycle
• Definitive host: Man.
• Intermediate host: Black fly (Simulium).
• Humans become infected by bite of black fly,
which possesses in its mouth the infective 3rd
stage larvae.
• The larvae enter the skin through the punctured
wound and migrate to subcutaneous tissue in
which they moult twice and develop into adult
worms.

5.
• The adult worms live in deep fascia or in the
subcutaneous tissue.
• The females release actively motile, unsheathed
microfilariae which migrate to the skin and eyes of
infected subjects.
• When a black fly again bites diseased human, the
microfilariae migrate into thoracic muscles, they
moult twice and develop into infective larvae.
• The larvae migrate to the mouth parts of black fly
where they transmitted to humans at next blood
meal.

6.
Life cycle

7.
Pathogenesis and clinical signs
• The disease is known as river
blindness (association of vector with
rivers) due to invasion of the eye
lead to loss of vision, corneal and
retinal lesions.
• Skin itching because the
microfilariae live in superficial layers
of skin.

8.
Diagnosis
• Demonstration of the adult worms inside
nodules.
• Demonstration of microfilariae in skin snips.
• Serological tests: PCR.

9.
Treatment
• Surgical removable of detectable
nodules (nodulectomy).
• Suramin is the first successful drug for treatment
of onchocerciasis.
• Diethylcarbamazine is effective microfilaricidal
drug.

10.
Loa loa
• Kingdom: Animalia
• Phylum: Nematoda
• Class: Chromadorea
• Order: Spirurida
• Superfamily: Filarioidea
• Family: Onchocercidae
• Genus: Loa
• Species: Loa loa

11.
Loa Loa
(Africa eye worm)
• Disease: loiasis, Calabar swelling.
• It is restricted in distribution West and Central
Africa.
• Habitat: in subcutaneous connective tissues of
man.

12.
Morphology
• Adult worms are thin, whitish and
taper towards cephalic end.
• Male measures 30-34 mm x 0.35-
0.43 mm with ventrally curved
caudal end and narrow alae.
• The female, 40-70 mm x 0.5 mm
with vulva opens in cervical
region.
• Loa loa microfilaria: sheathed
with nuclei in extending to the
end of the tail.

13.
Life cycle
• Definitive host: Man.
• Intermediate host: Mango fly (Chrysops
dimidiata, C. silacea).
• Man infects by bite of infected female, the larvae
enter through punctured wound on the skin to
subcutaneous tissue, moult and develop to
mature adult worms (takes 6-12 months).
• The females produce microfilariae which reach
peripheral blood during the day time and
ingested by female Chrysops during blood meal,

14.
• They penetrate stomach wall and reach thoracic
muscles where they develop into infective
larvae.
• The infective larvae migrate to mouth parts of
Chrysops for transmission to human.

15.
Life cycle

16.
Pathogenesis and clinical signs
• Eye lesions: pain, impaired vision,
granuloma and oedema of eyelid.
• The worm live in subcutaneous connective
tissue and causing painless, oedematous
swelling known as fugitive or Calabar swelling
(measure 5-10 cm in diameter).

17.
Diagnosis
• Identification of microfilariae in peripheral blood
during day time.
• Detection or removal of adults from eye or
Calabar swelling.

18.
Treatment
• Surgical removal of adult worms.
• Diethylcarbamazine is the drug of choice.