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Epidemiology and Clinical Manifestations of Lymphatic Filariasis

Epidemiology and Clinical Manifestations of Lymphatic Filariasis. Dr. Dilip Kumar Das Associate Professor, Community Medicine R. G. Kar Medical College, Kolkata, West Bengal. What is Lymphatic Filariasis?.

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Epidemiology and Clinical Manifestations of Lymphatic Filariasis

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  1. Epidemiology and Clinical Manifestations of Lymphatic Filariasis Dr. Dilip Kumar Das Associate Professor, Community Medicine R. G. Kar Medical College, Kolkata, West Bengal

  2. What is Lymphatic Filariasis? • Lymphatic filariasis is a disfiguring, disabling communicable human disease caused by the thread like nematode parasitic filarial worms. • A leading cause of permanent and long-term disability in the world • A cause of major social and economic burden

  3. Global Burden

  4. Globally……… • Affects 83 countries in the world • About 1.2 billion people at risk of infection • 120 million people have some form of the disease • 40 million are incapacitated/disfigured • SEAR: 60 million infected, 31 million have clinical manifestations • More than one third of the infected people in India

  5. Filarial Endemicity in India Endemic districts with MF rate 1% and above Low endemic districts with MF rate below 1% Districtsunder survey Non-endemic districts

  6. In India……. • 250 districts in 20 states/UTs are endemic • 600 million people are at risk of infection • 6 million attacks of acute filarial disease per year • 20 million one or more chronic filarial lesions • Highly endemic states: Uttar Pradesh, Bihar, Jharkhand, Andhra Pradesh, Orissa, Tamilnadu, Kerala, Gujarat.

  7. Basic Epidemiology of LF Agent : • Filarial parasite: Nematode • 3 of 8 species cause Lymphatic Filariasis • Wuchereriabancrofti, Brugiamalayi, Brugiatimori • In India: W. bancrofti (99.4%) and B. malayi (0.6%) cause LF • Develops in two hosts: Man – Primary (definitive) host Mosquito – Secondary (intermediate) host Periodicity Nocturnally Periodic Diurnally Sub-periodic

  8. Basic Epidemiology of LF… Host : - Man is the natural host. - All ages are susceptible to infection. - Adults are more frequently and more heavily infected than children - Mf rate is higher in men - Filaria disease appears in a small percentage of infected individuals. - Urbanization, industrialization, migration of people and specific habits are some of the social factors associated with filariasis.

  9. Basic Epidemiology of LF… Vectors : • BancroftianFilariasis (nocturnally periodic): Culexquinquefasciatus. • Brugian (Malayan) Filariasis: Mansonoidesannulifera, M. uniformis, M. indiana. • BancroftianFilariasis (Diurnally sub-periodic): Ochlarotatus (Finlaya) niveus group • C. quinquefasciatus generally breed in dirty and polluted water (stagnant drains, cesspools, septic tanks, burrow pits etc). Mansonoides breed in water bodies containing certain aquatic plants • C. quinquefasciatus is highly anthrophilic, an indoor rester (endophilic) and bites at midnight.

  10. Basic Epidemiology of LF… Environment: • Prevalent both in urban and rural areas • Climate influences the breeding and longevity of vector mosquitoes and also determines the development of parasite in the vector • Bad drainage, inadequate sewage disposal, lack of town planning increase vector breeding

  11. How is LF transmitted?

  12. Incubation Period • Extrinsic incubation period: Time interval for microfilariae to develop inside the mosquito to 3rd stage infective larvae. (10 – 14 days) • Pre-patent period: Time interval between introduction of infective larvae and the first appearance of detectable Mf in the peripheral blood. (12 –18 months) • Clinical incubation period: Time interval from invasion of infective larvae to the development of clinical manifestations. (8 – 16 months)

  13. Clinical Manifestations • Lymphatic Filariasis • Stage of invasion • Asymptomatic/carrier stage • Stage of acute manifestations • Stage of chronic manifestations • Ocult Filariasis

  14. Clinical features • Recurrent attacks • Filarial fever • Lymphangitis • Lymphadenitis • Epididymo-orchitis in males • Mastitis in females • Lymphoedema • Elephantiasis • Hydrocele • Chyluria

  15. Acute Filarial Lymphangitis

  16. Acute dermatolymphangioadenitis

  17. After the “acute attack”

  18. Entry lesions common in Lymphoedema InjuryCandidiasis PyodermaParonychia Fissure foot Eczema Insect bites

  19. Entry lesions can cause acute attacks

  20. Chronic obstructive lesions:Elephantiasis

  21. LF is a social evil… Disfigurement of limbs and genitalia leads to • Stigma • Anxiety • Ostracization • Psychological trauma • Sexual dysfunction The disease impedes • Mobility • Travel • Educational opportunities • Employment opportunities • Marriage prospects

  22. Global economic loss at US $ 2 billion per annum India loses 1.2 billion man days annually Estimated economic loss in India alone is US $ 850 million per year The economic loss is equivalent to 0.05% of GNP A major cause of poverty in the regions LF drains the economy…

  23. How can LF be diagnosed? • Clinical examination for filarial symptoms • Detection of microfilariae in mf carriers - Thick blood film (20 c.mm) microscopy at night (8-30 PM – 12 AM) - MFC method - DEC provocation test • Antigen detection Immunochromatographic test (ICT): Field friendly, sensitive and specific, easy to perform and can be done at any time during the day or night • DNA based molecular techniques

  24. Microfilariae in peripheral blood

  25. Filaria Survey Prevalence of Filariasis can be estimated by • Clinical Survey • Parasitological Survey • Entomological Survey

  26. Parasitological indices • Microfilaria rate: No of slides +ve for mf Total number of slides examined • Average mf density Total number of mf among +ve blood smears Number of +ve blood smears • Disease rate No of persons +ve for disease Total number of persons examined x 100 x 100

  27. Entomological indices • 10 man hour density No of male & female Cx. Quinquefasciatus collected Time (in hours) spent on mosquito collection • Vector infection rate - Percentage of female vector mosquitoes +ve for L-1/L-2/ L-3 stage larvae • Vector infectivity rate - Percentage of female vector mosquitoes +ve for infective larvae (L-3 stage) • Average number of infective larvae per infective mosquito x 10

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