wuchereria bencrofti

13 DECEMBER 2016
AASIFIBRAHIM786@GMAIL.COM /
ASIFKANTH89@GMAIL.COM

Wuchereria bancrofti is a human parasitic roundworm that is the
major cause of lymphatic filariasis., that infect the lymphatic system to
cause lymphatic filariasis. Filarial worms are spread by a variety
of mosquito vector species. W. bancroftiis the most prevalent and
affects over 120 million people, primarily in Central Africa and the Nile
delta, South and Central America, the tropical regions of Asia including
southern China, and the Pacific islands. If left untreated, the infection
can develop into a chronic disease called elephantiasis. In rare
conditions it also causes tropical eosinophilia, an asthmatic disease.
Limited treatment modalities exist and no vaccines have been
developed.
13 DECEMBER 2016

As a dioecious worm, W. bancrofti exhibits sexual
dimorphism. The adult worm is long, cylindrical,
slender, and smooth with rounded ends. It is white in
colour and almost transparent. The body is quite
delicate making it difficult to remove from tissues. It
has a short cephalic or head region connected to the
main body by a short neck which appears as a
constriction. There are dark spots which are
dispersed nuclei throughout the body cavity, with no
nuclei at the tail tip. Male and female can be
differentiated by size and structure of tail tip.
13 DECEMBER 2016

 The male worm is smaller, 40 millimetres (1.6 in) long and 100 micrometres
(0.0039 in) wide, and features a ventrally curved tail. The tip of the tail has 15 pairs
of minute caudal papillae, the sensory organs. The anal region is an elaborate
structure consisting of 12 pairs of papillae, of which 8 are in front and 4 are behind
the anus.
 In contrast, the female is 60 millimetres (2.4 in) to 100 millimetres (3.9 in) long and
300 micrometres (0.012 in) wide, nearly three times larger in diameter than the
male. Its tail gradually tapers and rounded at the tip. There are no additional
sensory structures. Its vulva lies towards the anterior region, about 0.25 mm from
the head. Adult male and female are most often coiled together and are difficult to
separate. Females are ovoviviparous and can produce thousands of juveniles known
as microfilariae
 The microfilaria is a miniature adult and retains the egg membrane as a sheath, and
is often considered an advanced embryo. It measures 280 μm long and 25 μm wide.
It appears quite structureless 'in vivo', but histological staining makes its primitive
gut, nerve ring and muscles apparent
13 DECEMBER 2016

 W. bancrofti carry out their life cycle in two hosts.
 Human beings serve as the definitive host and
 mosquitoes as their intermediate hosts.
 The adult parasites reside in the lymphatics of the human host. They are
found mostly in the afferent lymphatic channels of the lymph glands in the
lower part of the body. The first-stage larvae, known as microfilariae, are
present in the circulation.
 The microfilariae are found mainly in the peripheral blood and can be found
at peak amounts from 10 p.m. to 4 a.m. They migrate between the deep and
the peripheral circulation exhibiting unique diurnal periodicity. During the day,
they are present in the deep veins, and during the night, they migrate to the
peripheral circulation. The cause of this periodicity remains unknown,
13 DECEMBER 2016

 The microfilariae are transferred into a vector, which are most
commonly mosquito species of the
genera Culex, Anopheles, Mansonia, and Aedes. Inside the
mosquito, the microfilariae mature into motile larvae called
juveniles. When the infected mosquito has its next blood
meal, W. bancrofti is egested via the mosquito’s proboscis into
the blood stream of the new human host. The larvae move
through the lymphatic system to regional lymph nodes,
predominantly in the legs and genital area. The larvae develop
into adult worms over the course of a year, and reach sexual
maturity in the afferent lymphatic vessels. After mating, the adult
female worm can produce thousands of microfilariae that
migrate into the bloodstream. A mosquito vector can bite the
infected human host, ingest the microfilariae, and thus repeat
the life cycle
13 DECEMBER 2016

 The pathogenesis of W. bancrofti infection is dependent on the immune system and
inflammatory responses of the host. After infection, the worms will mature within 6–
8 months, male and female worms will mate and then release the microfilariae.
These microfilariae can be released for up to ten years
 The asymptomatic phase usually consists of high microfilaremia infection
 In the inflammatory (acute) phase, the antigens from the female adult worms elicit
inflammatory responses. The worms in the lymph channels disrupt the flow of the
lymph, causing lymphedema. The individual will exhibit fever, chills, skin
infections, painful lymph nodes, and tender skin of the lymphedematous extremity.
 The obstructive (chronic) phase is marked by lymph varices, lymph
scrotum, hydrocele, chyluria (lymph in urine), and elephantiasis. Microfilariae are
not normally present in this phase.
13 DECEMBER 2016

Prevention focuses on protecting against
mosquito bites in endemic regions. Insect
repellents and mosquito nets are useful to
protect against mosquito bites. Public
education efforts must also be made within the
endemic areas of the world to successfully
lower the prevalence of W. bancrofti infections.
13 DECEMBER 2016

aasifibrahim786@gmail.com
asifkanth89@gmail.com
Mob.9070262786 /
9018533143
13 DECEMBER 2016

wuchereria bencrofti

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