Loa-Loa Onchocerca Volvulus Wuchereria Bancrofti History,Epidemiology,Morphology,Life cycle.

1. Tissue Nematodes
Filariasis

2. •Wuchereria bancrofti

3. • Early scientific milestones in filariasis history abroad include the following.
• 1863: Demarquay in Paris found microfilariae in hydrocele liquid of a Cuban.
• 1866: Wucherer found microfilariae in chyluria.
• 1872: Lewis found microfilariae in blood.
• 1877: Bancroft found a female adult filarial worm in the ulcer of lymph node of the arm.
• 1877: Manson found microfilariae in the stomach of bloodsucked mosquito, which was practically the “birth” of
medical entomology.
• 1879: Manson found microfilarial nocturnal periodicity.
• 1888: Sibthorpe found male adult worms.
• Those in Japan include the following.
• 1876: Erwin Von Baelz detected microfilariae in blood (in Tokyo).
• 1896: Yushitaro Matsuura found a female adult worm in an inguinal lymph node (in Kumamoto).
• 1903: Shichiro Hida found a male filaria in the left seminiferous hydrocele.
History

4. Epidemiology
• is the most widely distributed human filarial parasite in tropical .
• Lymphatic filariasis affects over 120 million people in 72 countries throughout the
tropics and sub-tropics of Asia, Africa, the Western Pacific, and parts of the Caribbean
and South America.
• In the Americas, only four countries are currently known to be endemic: Haiti, the
Dominican Republic, Guyana and Brazil.
• In the United States, Charleston, South Carolina, was the last known place with
lymphatic filariasis. The infection disappeared early in the 20th century. Currently, you
cannot get infected in the U.S.

5. Morphology
• W. bancrofti exists in three forms : adult , microfilarial and larval .
• the adult worms are thread like and live in lymphatic tissues of
humans as tightly coiled nodular masses .they have a small cuticle
and their ends are rounded .the average life span of adult worm is 4
to 5 years. female worms d liberates sheathed embryos ( microfilariae
). Microfilariae live in blood vessels and are actively motile they are
found in peripheral blood in 10 PM and 4 AM .they are covered with a
pink with a column of violet nuclei . these nuclei is absent at the head
and tail ends . Microfilariae develop in mosquitoes .

6. Life cycle
• W. bancrofti has a complex life cycle .Humans are the
definitive host while mosquitoes of genera Culex , Aedes and
Anopheles are the intermediate hosts .Infective form for
humans are the third stage larvae present in the mosquitoes.
These larvae are deposited on the skin of humans . near the
site of mosquitoes bite .later the larvae penetrate through
the puncture wound to reach subcutaneous tissue .these
larvae enter afferent lymphatics and reach the draining lymph
nodes to develop into adults in 3 to 15 months . the male
fertilized the female ; the gravid female then gives birth to
sheathed embryos (the microfilariae)

7. • microfilariae enter efferent
lymphatics to reach blood
circulation the sheathed
microfilariae are ingested by
mosquitoes along with their
blood meal . microfilariae lose
their sheath in stomach and then
penetrate the gut wall to reach
thorax of the mosquitoes , they
develop into the first stage then
the second stage and lastly the
infective third stage larvae .these
third stage larvae enter the
proboscis sheath ready to infect a
new host .
•

8. •Loa loa

9. History
• first described in 1770 by a French surgeon, Mongin, when he unsuccessfully tried to
excise a worm from the eye of a women in Santa Domingo.
• 1778 surgeon observed the eye worm in slaves being taken from Africa to the West Indies.
• Dr. Patrick Mason was the first to identify the microfilariae of Loa loa in 1890
• In 1895, Dr. Argyll Robertson was the first to connect the presence of "Calabar swellings,"
or raised bumps on the forearms and wrist, with Loa loa infection.

10. Epidemiology
• Loa loa parasites are found in West and Central Africa.

11. Morphology
• Although often referred to as the "eye worm," Loa loa adults
can be found in subcutaneous tissues in any part of the body,
as well as in the conjunctiva of the eye. The female produces
microfilaria, and the vector for the disease is a fly of the genus
Chrysops .
• The adult worms, which can measure 40-70 mm in length, can
migrate through the subcutaneous tissues causing
inflammation, and if the adults stay in one place for an
extended period of time they can provoke a noticeable
swelling, often called a "Calabar swelling." This species is
confined to parts of equatorial Africa.

12. Life Cycle:
• The vector for Loa loa filariasis are flies from
two species of the genus Chrysops, C. silacea
and C. dimidiata. During a blood meal, an
infected fly (genus Chrysops, day-biting flies)
introduces third-stage filarial larvae onto the
skin of the human host, where they
penetrate into the bite wound (1) . The larvae
develop into adults that commonly reside in
subcutaneous tissue (2) .

13. • . Adults produce microfilariae measuring 250 to
300 μm by 6 to 8 μm, which are sheathed and
have diurnal periodicity. Microfilariae have
been recovered from spinal fluids, urine, and
sputum. During the day they are found in
peripheral blood, but during the noncirculation
phase, they are found in the lungs (3)

14. • The fly ingests microfilariae during a blood
meal (4) . After ingestion, the microfilariae
lose their sheaths and migrate from the fly’s
midgut through the hemocoel to the thoracic
muscles of the arthropod (5) . There the
microfilariae develop into first-stage larvae
(6) and subsequently into third-stage infective
larvae (7) . The third-stage infective larvae
migrate to the fly’s proboscis (8) and can
infect another human when the fly takes a
blood meal (1)

16. •Onchocerca volvulus

17. history:
• 1874 The subcutaneous microfilaria are discovered by John O’Neill, an Irish Naval surgeon, while examining
skin-snips from craw-craw patients in Ghana.
• 1893 Zoologist Rudolf Leuckart first describes the morphology of adult worms in subcutaneous nodules.
• 1890 Patrick Manson observes and identifies the adult worms.
• 1904 Emile Brumpt recognizes that the microfilariae come from the adult worms living in subcutaneous
nodules and that the infection occurs most commonly along river banks.
• 1917 Rodolfo Robles publishes findings on a “new disease” from Guatemala associated with subcutaneous
nodules, anterior ocular lesions, dermatitis, and microfilariae.
• 1920 The role of microfilariae in causing skin lesions is established by A. Lacroix and Jean Montpellier.
• 1923 Scottish parasitologist Breadablane Blacklock working in Sierra Leone, establishes that O. Volvulus (and
therefore onchocerciasis) is transmitted by sand flies .
• 1932 Jean Hissette describes the link between microfilaria and blindness in the Belgian Congo.

18. distribution
• O .volvulus is found in tropical Africa , Central America and Yemen in Asia and is the second most
common cause of infectious blindness or river blindness.
• Onchocerciasis occurs mainly in tropical areas. More than 99% of infected people live in 31
countries in sub-Saharan Africa: Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African
Republic, Chad, Republic of Congo, Côte d’Ivoire, Democratic Republic of the Congo, Equatorial
Guinea, Ethiopia, Gabon, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Malawi, Mali, Mozambique,
Niger, Nigeria, Rwanda, Senegal, Sierra Leone, South Sudan, Sudan, Togo, Uganda, United Republic
of Tanzania.
• Onchocerciasis is also transmitted in Brazil, Venezuela (Bolivarian Republic of) and Yemen.

19. Morphology :
• O .volvulus exists in 3 forms : adult, microfilarae
and larval. adult worms lived knotted together
and produce nodules in the subcutenous tissues
of humans and causes river blindness. the
average life span of the adult worms is 9 years .
the adults mature , mate and the gravid female
releases unsheathed embryos ( microfilariae ).
Microfilariae measure 150 to 360 µm × 5 to 9
µm and the nuclei do not extend to the tail tip .

20. Life cycle
O .volvulus has a complex life cycle . it
requires two intermediate hosts to
complete life cycle . Humans are the
definitive host and black flies of the genus
Simulium damnusum act as the
intermediate hosts . the infective form for
humans are the infective larvae present in
the proboscis of the black flies .the
infective larvae deposited on the humans
skin when the infected flies bite. then the
larvae penetrate through the bite wound to
enter the subcutaneous tissues

21. • they develop into mature adults in 7
months to 3 years .the male fertilized
female worm and the gravid female
produce many unsheathed microfilariae .
Microfilariae leave the nodules and spread
to the subcutaneous tissue , dermis , and
eye . the microfilariae present in large
number in dermis . the black fly sucks
microfilariae during its meal .after
ingestion the microfilariae penetrate the
gut and enter the thoracic muscles they
molt here to become infective larvae . the
infective larvae then find their way to
enter proboscis of the black fly .