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Lymphatic filariasis

Lymphatic filariasis



Salient feature of Lymphatic Fileriasis that includes epidemiological and control aspects.

Salient feature of Lymphatic Fileriasis that includes epidemiological and control aspects.



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    Lymphatic filariasis Lymphatic filariasis Presentation Transcript

      • Wuchereria bancrofti (Nocturnal periodic) transmitted by Culex quinquefasciatus
      • Brugia malayi (Nocturnal periodic) transmitted by Mansonia mosquitoes
      • W. bancrofti (Diurnal subperiodic) transmitted by Aedes (Finlaya) niveus group of mosquitoes
      Species of Filarial Infections Prevalent in India Brugia malayi Wucheria bancrofiti
      • Wuchereria bancrofti (Lymphatic filaria)
      • Brugia malayi
      • Brugia timori
      • Loa loa
      • Onchocerca vovulus
      • Mansonella streptocerca (Serous cavity / membrane filariasis)
      • Mansonella ozzardi
      • Mansonella perstans
      • Types of Filarial worms
      • The word ‘fileria’ is derived from ‘ filer which means threadlike.
      • The disease has been in existance in India since 6 th century B.C.
      • In 1709,Clark in Cochin gave the name ‘Malabar leg’
      • In 1866, Wucherer in Brazil found microfileria in chylous urine.
      • In 1872,Lewes working in Calcutta found microfilariae in peripheral blood.
      • In 1876 Bancroft in Brisbane,Australia discovered the adult female.
      • Manson working in China in 1878 discovered the development of W.Broncofti in mosquitoes. Manson also discovered the phenomenon of ‘periodicity’ in filariasis.
      • In 1927,Bruge discovered the microfileriae of B. Malayi in Indonesia.
      • In 1940, Rao and Maplestone discovered the adults of B. malayi in India .
      • In 1946, Diethyle carbamazine, the most effective drug against filariasis was invented.
    • LF Disease Burden
      • LF persist as disease of poverty
      • 1.2 billion people at risk globally
      • 120 million infected and half with disease
      • 14 million with chronic lymphoedema and 25 million with hydrocele
      • India responsible for 38% of global burden and >70% cases in SEA Region
      • US$1.5 billion (Rs.4400 crores) economic loss in India alone
      • China: 6:1 return on its investment on LF elimination
    • Present Status of Filariasis in India
      • Estimates made on the basis of surveys carried out during the last five decades
      • 473 million are living in endemic areas
      • (348 in rural areas + 125 in urban areas)
      • 31 million microfilaria carriers
      • 23 million filaria disease cases
      • India contributes 38% of LF problem in the world and more than 70% in SEA Region
    • Mapping LF Distribution In Endemic Countries 54 countries completed
    • 54 countries completed 15 countries in progress 14 still unmapped Mapping LF Distribution In Endemic Countries
    • As of now, 42 countries under MDA Mapping LF Distribution In Endemic Countries
    • Fileriasis World pharmaceutical market > $400 bn in 2002 Neglected Diseases Most Neglected Diseases Global Diseases What are “neglected diseases”?
    • LIFE CYCLE OF W. Brancrofti IN HUMANS
      • The definitive host is the human,in whose lymphatic system the adult worms are harboured.live embryos(microfilariae) are discharged which find their way to blood stream.
      • The microfilariae are capable of living in the peripheral blood for a considerable time without undergoing any developmental metamorphosis.They are subsequently taken up by the female culicine mosquitoes during a blood meal.
      • The intermediate host is a mosquito, in which the microfilariae undergo further development,after which they become infective to human. A large number of species of mosquito belonging to the genus Culex,Aedes and Anopheles act as intermediate hosts for W.bancrofti and Brugia malayi.
      • Sheathed microfilerae ingested by the mosquito cast off their sheath quickly(ex-sheathing),penetrate the gut wall within an hour or two and migrate to the thoracic muscle. Here they rest and begin to grow.
      • In the next 2 days, the slender snake like organism changes to a thick,short, sausage-shaped form with a short,spiky tail known as first stage larva.
      • In next 3 to 7 days time the larva grows rapidly,moulds once or twice(second stage larva).
      • On the 10 th or 11 th day the metamorphosis becomes complete,the tail atrophies to a mere stump with fully developed digestive and genital system. This is the third stage larva.At this stage it is infective to humans and enters the proboscis sheath of the mosquito on or about 14 th day
      Note :- It should be noted that one microfilaria gives rise to one infective larva in the proboscis sheath. There may be several larvae remaining coiled up’ waiting for an opportunity to infect human while the mosquito is having its blood meal.
    • Salient points of Life cycle
      • It requires many infective bites to become the microfilariae carrier.
      • The microfilariae carriers are asymptomatic for 5-6 years
      • The chronic disease cases are mostly negative for microfilariamea
      • The microfilariamea exhibit nocturnal periodicity in main land India.
      • The incubation interval is nearly 1 year.
    • Salient points of Life cycle…. Contd.
      • Size of adult worm female 8-10 cm in length. 0.3 to 0.4 mm in thickness.
      • Male is 2.5-4 cm in length and 0.1 mm in thickness.
      • L1 (Sausag stage)-124 to 250 micrones in length. 2 days for development
      • L2 (Preinfective stage)- 225-330 micrones in length. 3-7 days for development
      • L3 (Infective stage) – 1500-2000 micrones in length. 8-10 days for development.
      Development of human filariastic parasite is in the thoracic muscle of the mosquito which is an intermediate host unlike in respect of malaria parasite.
      • MODE OF INFECTION :- Innoculative method, through the bite of certain culicine mosquitoes.
      • TRANSMITTING AGENT :- Female mosquitoes of the species Culicine/Aedes/Anopheles depending
      • upon their geogrophical prevalence.
      • INFECTIVE FORMS :- Third stage larvae of developing microfilariae.
      • PORTAL OF ENTRY :- Skin
      • SITE OF LOCALISATION :- Lymphatic system of the host, superior or inferior extremities according to the site of bite., most commonely of inguino-scrotal region.
      • Mode of transmission :-Transmitted by the bite of an infected mosquito.The parasite(infective larvae) is deposited near the site of the puncture,gets attractedby the warmth of the body,penitrates the skin on its own and enters the lymphatic system through the capillaries.
      • Biological incubation period(pre patent period ):- This lasts for one to one and half years During this period the infective larvae(third stage) grows to adult forms and becomes sexually mature.
      • Patent period:- Being viviparous,gives birth to microfilarae which subsequently appear in peripheral blood.
      • Periodicity:- The mf of W.bancrofti and B. malayi may display a nocturnal periodicity and appear in large numbers at night and are either absent or scarce during the day. The maximum density of mf in blood is reported between (10 pm) to (2 am to 4 am) which may be due to the blood searching activities and biting rhythm of the vector during the time.
      • Man is the natural host
      • Age :- All ages are susceptible to infection. Infection rates tend
      • to rise up to age 20-30,but not there after- may be due to the fact that some of the persons developing the disease become –ve for mf.
      • Sex :- Sex does not appear to influence the infection rate.
      • Density of infection :- It is reported to be one mf per40 c.mm of blood
      • is infective to 2.6 percent of mosquitoes feeding on him.
      • Migration of people :- This has led to extension of the disease into areas previously non endemic.
      • Immunity :- Man may develop resistanse to infection and superinfection -- immunological basis still unknown.
      • Social factors :- Rapid unplanned urbanization, population movement and sleeping habits. The swelling of legs and other parts of body causes suffering,stigma and reduced working capacity of the patients.
    • Life cycle of Culex mosquito Egg laying Egg raft Larvae Pupa Adult
    • Breeding places of Culex quinquefasciatus, the vector for filariasis
    • Serious about eliminating LF ??…….always look out…..keep on searching for it…….so circumspection/vigilance is the key word…….
      …… .. THANKS
      • Acknowledgements :
      • WHO
      • CDC
      • NVBDCP
      • NCDC
    • Knowing is not enough; we must apply. Willing is not enough; we must do. (Goethe)