wuchereria NEW


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Wuchereria Dr.K.S.Kumudha Valli I yr P.G. MD Microbiology Madras Medical college Rajiv Gandhi GGH, Chennai – 3.

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Class Nematoda Order Spirurida Superfamily Filarioidea Genera: Wuchereria, Brugia, Onchocerca, Loa, Drofilaria, Mansonella. Adults live in tissues or body cavities of vertebrate host. Females produce microfilariae that circulate through the host. Undergo development in, and are transmitted by arthropod vectors.

Nematoda Characteristics:

Nematoda Characteristics Elongated, Cylindrical, unsegmented bodies Body covered with tough cuticle. Diecious Complete alimentary tract. Sexual reproduction .

Wuchereria bancrofti (Bancroft’s filaria) :

Wuchereria bancrofti (Bancroft’s filaria) Adult worms- Lymphatic vessels & lymph nodes Have preference for: Testicular tissue, Lymphatic glands of groin, labia and Mammary glands of females

Epidemiology :

Epidemiology Man is only known host Found in the tropics India West Indies Puerto rico Southern China Japan South America

Microfilariae -Morphology :

Microfilariae -Morphology Long, hair like, transparent Filiform shaped Male : 2.5-4 cms x 0.1mm , 2 spicules at tail end Female : 8-10 cms x 0.2-0.3 mm, narrow, pointed tail viviparous (gives birth to larvae ) Life span:5-10 yrs Colorless, blunt heads and pointed tails

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Embryo - 290 µm x 6-7µm *Hyaline sheath *Cuticle *Somatic cells or nuclei * # Nerve ring # Ant. V spot-represents rudimentary excretory system # Post. V spot-represents terminal part of alimentary canal *G (Genital) cells 1,2,3 &4-posterior *Innenkorper of Fulleborn or Central (Internal) body of Manson-spot-represents rudimentary alimentary canal

Life cycle:

Life cycle 2 hosts- man & mosquito Infective form- 3 rd stage larva POE- skin Def. host: man Microfilariae are produced 6-8months after infection with L3 larvae 5-18 months-sexually mature Intermed. Host: mosquito – Culex, Aedes & Anopheles 14 th day infective to man Microfilariae unsheath in mosquito gut, migrate to thoracic muscles, undergo two molts becoming L3 larvae in 10 to 11days.(Do not divide in vector – cyclodevelopmental biological transmission

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6-8months after infection with L3 larvae 5-18 months-sexually mature undergo two molts becoming L3 larvae in 10 to 11days


Microfilariae circulation in blood is periodic. Periodicity is characteristic of species (strain) and geographic area. Nocturnal Periodicity- microfilariae in blood are high during 10 pm – 4 am In most regions W. bancrofti exhibit nocturnal periodicity – Culex fatigans . In South Pacific they exhibit diurnal periodicity – Aedes polynensis ( subperiodic). Periodicity

Pathogenesis :

Pathogenesis Attributable to adult worms Mostly asymptomatic in early years Low grade fever -immune reaction to developing worms. Acute phase of infection -when microfilariae are released. Host responds to dying worms and worm byproducts. Lymph nodes become inflamed. Immune cell activation leads to fevers, chills toxemia …

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Lymphatic vessels become swollen, damaged and leaky (lymphedema). leakage of protein or fluid to surrounding tissues. Can have localized swellings in arms and legs. In males scrotum usually affected. Lymphangitis Lymphatic obstruction Lymph varix Elephantiasis

Clinical manifestations:

Clinical manifestations Asymptomatic Symptomatic Inflammatory Lymphangitis & lymphadenitis Obstructive Varicose LN, scrotum, hydrocele, chyluria, elephantiasis

Occult filariasis (Meyers- Kouwenaar syndrome):

Occult filariasis (Meyers- Kouwenaar syndrome) Massive eosinophilia Gen. lymphnode enlargement Hepatosplenomegaly Pulmonary symptoms Absence of microfilaremia Unusual host-reaction to filarial antigen, mf destroyed in tissues High titre of filarial- complement fixing antibody Clinical, haematological & serological manifestations respond readily to DEC

Tropical pulmonary eosinophilia ( Eosinophilic lung, Weingarten’s syndrome):

Tropical pulmonary eosinophilia ( Eosinophilic lung, Weingarten’s syndrome) Fever, Wt loss Paroxysmal cough Dyspnoea Splenomegaly CXR-miliary mottling in lung fields Demonstration of mf in Lung biopsy

Pathogenic lesions:

Pathogenic lesions Inflammation Dilatation of lymphatics-Lymphangiovarix Rupture of Lymphangiovarix Lymphorrhagia Chylorrhagia Hyperplasia of skin & conn. Tissue- Elephantiasis Secondary bacterial infection


Lymphangitis Epididymo-orchitis Funiculitis (spermatic cord) Retroperitoneal lymphangitis Lymphatics of upper & lower extremities

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Lymphadenitis Inflammation of regional LN Not painful, skin not adherent Filarial fever-3-5 days Hydrocele Chyluria Rupture of varicose chyle vessels thro. Mucus memb of urinary tract


Fibrotic constriction of afferent lymphatics Development of secondary channels. More lymph flows into tissue. Eventually calcification and blockade. Found in a small proportion of infected individuals. Often seen after prolonged exposure. Elephantiasis

Diagnosis and treatment:

Diagnosis and treatment Direct evidence Search for Microfilariae In peripheral blood Chylous urine Exudate of lymph varix Hydrocele fluid Search for Adult worms Bx lymph node Calcified worm in X ray

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Indirect evidence Allergic tests Blood exmn-eosinophilia Intradermal test Immunological tests CFT

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Samples should be collected at night Use of thick blood smears stained with hematoxylin or Giemsa. Mf not found in blood in: Elephantiasis, due to lymph obstruction After lymphangitis, due to death of adult worm During early allergic manifestation Occult filariasis

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Xenodiagnosis Demonstration of Mf in stomach blood of Mosquito after biting infected pt


Treatment Filaricidal On Adult worms : Mel.W( Arsenical preparation) On Mf : DEC ( Hetrazan) On Infective larvae and Immature Adult worms : para-Melaninyl phenyl stibonate (MSb)


Prevention: Destruction of mosquitos Reducing the rate of infection among insect vectors Treatment of carriers by using Hetrazan Protection against mosquito bites


OTHERS BRUGIA MALAYI: Seen in natives of sumatra. Distribution restricted. In India more in Kerela. BRUGIA TIMORI: Limited to timor. Mf larger than Mf malayi. Fails to take giemsa stain. Leison – development of draining abscesses by worms in lymph nodes----- scarring.

Distingushing features of Mf.bancrofti&Mf.malayi:

Distingushing features of Mf.bancrofti&Mf.malayi FEATURES Mf.bancrofti Mf.malayi Length 250 to 300µm 175 to 230µm Appearance Graceful,sweeping curves Kinky ,with secondary curves Cephalic space Length and breadth equal Almost twice as long as broad Stylet at anterior end Single Double Excretory pore Not prominent Prominent Nuclear column Discrete nuclei Blurred Tail tip Pointed ,free of nuclei Two distinct nuclei,one at tip,other subterminal Sheath Faintly stained Well stained

Mf.bancrofti Mf.malayi:

Mf.bancrofti Mf.malayi

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