Lymphatic filariasis

Dr Snigdha Pattnaik.

Associate professor

Dept of Community medicine

• Lymphatic filariasis :infection with 3 nematode worm.

• W.bancrofti

• B.malayi

• B.timori

• Manifestation :acute and chronic.

• Lymphigitis,lymphadenitis,elephantiasis of legs and arms, and tropical eosinophilia

• Endemic in 83 countries

• 1.2 billion at risk

• More than 120 million people infected

• More than 25 million men suffer from genital symptoms

• More than 15 million people suffer from lymphoedema or elephantiasis of the leg

Agent factors

• Humans are the definitive host for the worms tha• There are no known reservoirs for W.bancrofti.• B.malayi has been found in monkeys, & cats.• PERIODICITY :nocturnal periodicity.

Definitive Host

• Humans are the definitive host for the worms that cause lymphatic filariasis

• There are no known reservoirs for W.bancrofti.• B.malayi has been found in macaques, leaf

monkeys, and cats

• Intermediate Host• W.bancrofti is transmitted by Culex .• B.malayi and B.Timori is transmitted by Anopheles

and Mansonia species.

• W.bancrofti is a sexually dimorphic species.

• The adult male worm is long and slender, between four and five centimeters in length, a tenth of a centimeter in diameter, and has a curved tail.

• The female is six to ten centimeters long, and three times larger in diameter than the male.

• Microfilariae are sheathed, and approximately 245 to 300 µm in length.

Wuchereria Life Cycle

• Man is natural host.• All age are suseptible to infection.• Filerial disease appears in a small percentage of

infected individuals.• Mf is higher in men.• Migration of people helps in spread of disease in

non endemic area.• Man develop immunity after yrs of infection.• Lymphatic fileriasis is associated with

urbanization, industrialisation ,poverty and poor sanitation.

Enviromental factors

• 22-38 degreecent and relative humidity of 70% is favorable.

• Lymphatic fileriasis is associated with bad drainage. vector breed profusely in polluted water.

Vectors of lymphatic filariasis

• W.bancrofti, B.malayi and B.timori transmitted by the bites of infective mosquito..

• Pre patent period: interval between inoculation of infective larvae and the first appearance of detectable mf .

• Clinical in cubation period :time interval from invasion of infective larvae to the development of clinical manifestation

• 8-16 mnths.

Clinical manifestations• Asymptomatic amicrofilaraemia :exposed

people in endemic area do not show Mf or clinical manifestation of disease.

• Asymptomatic microfilaraemia: blood is positive for Mf, but no symptoms.

• carriers.• Stage of acute manifestation: recurrent

episode of acute inflammation in lymph gland and vessels.

• Filerial fever, lymphangitis, lymphadenitis, lymphoedema and epididymoorchitis..

• Stage of chronic obstructive lesion: develops 10- 15 yrs acute attack.

• Due to fibrosis and obstruction of lymphatic vessel, causing permanent structural change.

• Hydrocele, elephantiasis and chyluria.

OCCULT FILARIASIS

• Tropical pulmonary eosinophilia.

• Hypersensitive to filarial antigen.

Management of Acute dermatolymphangioadinitis(ADLA)

• Analgesics.

• Antibiotic ,since majority of acute episodes appears to be of bacterial etiology.

• local hygiene measures with or without local antibiotic and antifungal agents to be promoted to prevent ADL so as to permit the reversal of lymph edema.

• home management includes drinking plenty of water,rest,elevation of limb,cooling the limb with cool water.

• Hydrocele Management :diagnosis and surgery.

H

Filaria survey

• Mass blood survey :

• Thick film 20cc blood at midnight

Thick smear prepared

Dehaemoglobinised and stained

• Membrane filtration test:low density microfileraemia.

• DEC provocation test

• Clinical survey.

• Xenodiagnosis

• Entomological survey

Control measure

• Chemotherapy :Diethylcarbamazine

• Vector control.

• Chemotherapy :DEC -6g/kg body wt per day orally for 12 days.

• Effective in killing Mf.

• No effect in on adult worm and infective larvae.

National Filaria Control Programme

launched in 1955 for the control of bancroftian  filariasis with the objectives of undertaking

surveys in known endemic areas,

 large scale control measures in selected areas and

 training of personnel required to man the programme

• Antivector measures to continue in all the NFCP towns as complimentary to antiparasitic measures

• mf carriers detected in filaria clinics and elsewhere to receive the standard dose of 6 mg/kg body wt. per day for 12 days

 

• mass drug administration with diethylcarbamazine (DEC),

• The DEC dosage adopted in   the programme is 6mg/kg body wt. per day for 12 days

• DEC medicated salt project with 0.2% concentration was concluded at Karaikal, Pondicherry which gave significant reduction in microfilaraemia

Vector control

• ANTI LARVAL MEASURE: ellimination of breeding place

• Chemical control: larvicidal oil,pyrosene oil,organophosporous larvicide.

• REMOVAL OF PISTIA PLANT.

• ENVIROMENTAL MEASURES.

• ANTI ADULT MEASURES:DDT,HCH

• PERSONAL PROPHYLAXIS.

 Revised Strategy for the control of Lymphatic Filariasis in India:

•   Single day mass therapy at a dose of 6 mg/kg body wt. annually.

•      Management of acute and chronic filariasis through referral services at selective centres.

•      IEC for inculcating individual/community based protective and preventive measures for filaria control

ASSESSMENT OF FILARIA CONTROL PROGRAMME

• CLINICAL PARAMETERS :incidence of acute manifestations and prevalence of chronic manifestation.

• PARASITOLOGICAL PARAMETERS :• Microfilerae rates.• Microfilerae density• Average infestation rate• ENTOMOLOGICAL PARAMETERS :vector

density,annual biting rate,larval breeding places.