All About Lymphatic Filariasis

Filariasis is caused by several round, coiled and thread-like parasitic worms belonging to the family filaridea.These parasites aftergetting deposited on skin penetrate on their own or through the opening created by mosquito bites to reach the lymphatic system. The disease is caused by the nematode worm, either Wuchereria bancrofti or Brugia malayi and transmitted by ubiquitous mosquito species Culex quinquefasciatus and Mansonia  annulifera/M.uniformis respectively. The disease manifests often in bizarre swelling of legs, and hydrocele and is the cause of a great deal of social stigma. Filariasis is caused by several round, coiled and thread-like parasitic worms belonging to the family filaridea. These parasites after getting deposited on skin penetrate on their own or through the opening created by mosquito bites to reach the lymphatic system.

Brugian filariasis: Lymphadenitis (swollen and painful lymphnode) occurs episodically, most commonly affecting one inguinal lymph node at a time. The infection lasts for several days and usually heals spontaneously. The frequency of episodes may vary from 1-2 attacks per year to several attacks per month. Sometimes lymphadenitis is followed by a characteristic retrograde lymphangitis. The infection may spread to the surrounding tissues, and occasionally involves the whole thigh or entire limb. The infected lymph node may become an abscess, ulcerate, and heal with  fibrotic scarring. The acute clinical course with its complications may last from several weeks to 3 months. Characteristically, elephantiasis involves the leg below the knee but occasionally it affects the arm below the elbow. Genital lesions or chyluria (milky colour urine) do not occur in brugian filariasis.

Bancroftian filariasis: The lymphatic vessels of the male genitalia are most commonly affected in bancroftian filariasis, producingepisodic funiculitis (inflammation of the spermatic cord), epididymitis and orchitis. Adenolymphangitis of the extremities is less common.Hydrocele is the most common sign of chronic bancroftian filariasis, followed by lymphoedema, elephantiasis and chyluria. The swelling involves the whole leg, the whole arm, the scrotum, the vulva or the breast. The fluid of hydrocele and chyluric patients may contain microfilariae, even when they are absent from the blood. Chyluria occurs intermittently and is more pronounced after a heavy meal. It is often symptomless, but some patients complain of fatigue and weight loss, resulting from loss of fat and protein.

Lymphatic filariasis (LF)

Photo Lymphatic Filariasis (LF), commonly known as elephantiasis is a disfiguring and disabling disease,usually acquired in childhood. In the early stages, there are either no symptoms or non-specific symptoms.Although there are no outward symptoms, the lymphatic system is damaged. This stage can last for several years. Infected persons sustain the transmission of the disease. The long term physical consequences are painful swollen limbs (lymphoedema or elephantiasis). Hydrocele in males is also common in endemic areas.

Due to damaged lymphatic system, patients with lymphoedema have frequent attacks of infection causing high fever and severe pain. Patients may be bed-ridden for several days and normalroutine activities become difficult.Such attacks not only cause acute physical suffering but also directly impede the earning capacity of the individual.Lymphatic filariasis is estimated to be one of the leading causes of disability worldwide.Elimination of the disease is an important tool for poverty alleviation and economic development.

Filaria vectors

C.quinquefasciatus is the vector of W.bancrofti in the mainland. C.quinquefasciatus breeds in association with human habitations and is the domestic pest mosquitoes, preferring polluted waters, such as sewage and sullage water collections including cess pools, cess pits, drains and septic tanks. In the absence of such type of water collections, they can breed in comparatively clean water collections also.

The eggs are laid in rafts containing 150-40 eggs each depending on quality and quantity of blood meal taken. At the optimum temperature of 250C to 300C, the eggs hatch within 24 to 48 hours. The youngest stage is the first instar larva which moults to subsequent instars each within 24-48 hours at optimum temperature. There are four instars in the larval stages, and all the instars are voracious eaters, taking anything and everything of microscopic size into the buccal cavity by instant vibration of its feeding brushes. They are mainly bottom feeders but may feed from the surface also.

The IV instar at the end of its stage gives rise to a comma shaped pupa, which lasts upto 24-48 hours at optimal condition. Pupae do not feed but are very active, respiring through its pair of breathing trumpets. The pupa emerges into an adult mosquito, through a longitudinal slit formed between the two trumpets. The entire cycle from egg to emergence of adult is completed in 10-14 days.

Transmission of Lymphatic Filariasis

The adult produces millions of very small immature larvae known as microfilariae, which circulate in the peripheral blood with marked nocturnal periodicity. The worms usually live and produce microfilariae for 5-8 years.

Adult Filarial Worms (Macrofilariae)inhabitinglymphatic system of man

Lymphatic filariasis is transmitted through mosquito bites.

The persons having circulating microfilariae are outwardly healthy but transmit the infectionto others through mosquitoes.

The persons with chronic filarial swellings suffer severely from the disease but no longer transmit the infection.

In India, 99.4% of the cases are caused by the species - Wuchereria bancrofti whereas Brugia malayi is responsible for 0.6% of the problem.

In the adult stage, filarial worms live in the vessels of the lymphatic system. Lymphatic system is the network of lymph nodes and lymph vessels that maintains the fluid balance between the tissues and the blood which is an essential element of the body's immune defense system.


Photo Man is the definitive host i.e. where the mature adult male and femaleparasitesmate and produce microfilariae whereas the mosquito is the intermediate host. The adult parasites are usually found in the lymphatic system of man. They give birth to as many as 50,000 microfilariae per day, which find their way into blood circulation. The life span of microfilaria is not exactly known which preferably may survive up to a couple of months.

The parasite cycle in the mosquito begins when the microfilariae are picked up by the vector mosquitoes during their feeding on the infected person (microfilaria carrier). The microfilaria in mosquito develops into three stages and under optimum conditions of temperature and humidity; the duration of the cycle in the mosquito (extensive incubation period) is about 10-14 days. When the infective mosquito feeds on other human host, the infective larvae are deposited at thesite of mosquito bite from where the infective larvae get into lymphatic system. In the human host, the infective larvae develop into adult male and female worms. The adult worms survive for about 5-8 years or sometimes as long as 15 years or more.

Magnitude of disease

Filariasis has been a major public health problem in India next only to malaria.The disease was recorded in India as early as 6th century B.C. by the famous Indian physician, Susruta in his book Susruta Samhita. In 7th century A.D., Madhavakara described signs and symptoms of the disease in his treatise 'Madhava Nidhana' which hold good even today.In 1709, Clarke called elephantoid legs in Cochin as Malabar legs.

The discovery of microfilariae (mf) in the peripheral blood was made first by Lewis in 1872 in Calcutta (Kolkata).

Indigenous cases have been reported from about 250 districts in 20 states/Union Territories.

The North-Western States/UTs namely Jammu & Kashmir, Himachal Pradesh, Punjab, Haryana, Chandigarh, Rajasthan, Delhi and Uttaranchal and North-Eastern States namely Sikkim, ArunachalPradesh, Nagaland, Meghalaya, Mizoram, Manipur and Tripura are known to be free from indigenously acquired filarial infection.

Cases of filariasis have been recorded from Andhra Pradesh, Assam, Bihar, Chhattisgarh, Goa, Jharkhand, Karnataka, Gujarat, Kerala, Madhya Pradesh, Maharashtra, Orissa, Tamil Nadu, Uttar Pradesh, West Bengal, Pondicherry, Andaman & Nicobar Islands, Daman & Diu, Dadra & Nagar Haveli and Lakshadweep.


Endemic district 250
(in 20 States/UTs)
Population: 600 Million

National Filaria Control Programme (NFCP)

After pilot project in Orissa from 1949 to 1954, the National Filaria Control Programme (NFCP) was launched in the country in 1955 with the objective of delimiting the problem, to undertake control measures in endemic areas and to train personnel to man the programme. The main control measures were mass DEC administration, antilarval measures in urban areas and indoor residual spray in rural areas. The NFCP set-up and population protected are given in the table below:

Population protected under NFCP and the set-up as on 01-03-2002

Sl.No. State/UTs Population Protected (in million) Filaria Control Units Survey Units Filaria Clinics
1. Andhra Pradesh 6.03 29 2 5
2. Assam 0.31 1 1 0
3. Bihar 8.40 35 2 38
4. Chhatisgarh Nil 0 0 0
5. Goa 0.37 4 0 6
6. Gujarat 3.91 9 0 7
7. Jharkhand        
8. Karnataka 0.72 6 1 19
9. Kerala 4.45 16 2 9
10. Madhya Pradesh 0.74 9 3 8
11. Maharashtra 6.52 16 6 10
12. Orissa 2.54 15 2 15
13. Tamil Nadu 9.44 21 1 42
14. Uttar Pradesh 7.33 29 2 34
15. West Bengal 1.53 10 4 3
16. Pondicherry 0.54 2 0 0
17. A&N Islands 0.06 1 1 1
18. Daman & Diu 0.03 2 0 2
19. Lakshadweep 0.01 1 0 0
20. Dadra & N' Haveli Nil 0 0 0


  • Recurrent anti-larval measures at weekly intervals.
  • Environmental methods including source reduction by filling ditches, pits, low lying areas, deweeding, desilting, etc.
  • Biological control of mosquito breeding through larvivorous fish.
  • Anti-parasitic measures through 'detection' and 'treatment' of microfilaria carriers and disease person with DEC by Filaria Clinics in towns covered under the programme.
Revised Strategy

Annual Mass Drug Administrationwith single dose of DEC was taken up as a pilot project covering 41 million population in 1996-97 and extended to 74 million population. This strategy was to be continued for 5 years or more to the population excluding children below two years, pregnant women and seriously ill persons in affected areas to interrupt transmission of disease.

Interruption of transmission of filariasis by Annual MDA for 5 years or more to the population except:

- children below 2 years
- pregnant women
- seriously ill persons
  (DEC + Albendazole in selected distt & DEC in other distt)
Morbidity Management

- Home based management of lymphoedema cases and
- up-scaling of hydrocele operations in the identified CHCs / District hospitals/ medical colleges.

National Goal

The National Health Policy 2002 aims at Elimination of Lymphatic Filariasis by 2015.

Morbidity Management

Sl No. LF endemic district 2007 2008 2009 2010 2011 2012
% coverage against eligible population % coverage against eligible population % coverage against eligible population % coverage against eligible population % coverage against eligible population % coverage against eligible population
1 Andhra Pradesh 89.13 91.96 91.85 92.50 92.74 93.30
2 Assam 78.32 81.34 ND 76.08 76.75 79.02
3 Bihar 77.23 ND 77.91 78.61 ND MDA done but report not yet received
4 Chhattisgarh 89.53 91.30 91.53 92.99 90.06 YD
5 Goa 97.83 96.44 95.37 94.63 96.21 MDA stopped
6 Gujarat 92.11 93.25 97.63 98.33 97.66 99.39
7 Jharkhand 79.03 84.62 85.99 63.64 86.53 Sep-13
8 Karnataka 89.67 90.53 89.30 91.46 91.81 93.84
9 Kerala 92.19 93.67 77.81 81.91 89.62 80.90
10 Madhya Pradesh 88.48 90.14 87.59 90.74 89.27 87.43
11 Maharashtra 88.53 91.05 89.51 89.38 89.28 89.30
12 Orissa 88.47 85.43 89.81 90.63 90.55 Oct-13
13 Tamil Nadu 77.22 88.80 94.13 ND 93.58 94.68(4 dist.)
14 Uttar Pradesh 79.87 81.67 ND 81.04 80.45 83.32
15 West Bengal 76.63 77.79 86.93 ND 79.23 YD
16 Pondicherry 96.30 97.01 96.02 96.92 97.14 MDA stopped
17 A & N Islands 98.73 94.10 91.40 77.12 90.15 90.06
18 Daman & Diu 93.27 91.85 91.56 92.04 90.89 MDA stopped
19 D & Nagar Haveli 94.16 96.67 95.84 96.20 98.51 96.88
20 Lakshadweep 81.81 82.63 83.86 80.09 73.94 YD
  Total 82.80 86.16 86.70 84.37 87.88 87.54
ND : Not Done | YD : Yet to do | RN: Report Not received

For any scientific publication, if this quoated or used for any analysis purposes, Dte.NVBDCP prior permission must be sought.

Trend of Average Microfilaria rates (%) in the State since 2004

Sl. No. States/UTs 2004 2005 2006 2007 2008 2009 2010 2011 2012
1 Andhra Pradesh 1.36 0.74 0.69 0.24 0.38 0.45 0.35 0.21 2.20
2 Assam ND 0.04 0.19 1.46 0.88 0.81 1.06 0.17 0.23
3 Bihar 1.5 2.15 1.38 0.68 NR 1.07 0.94 NR 1.56
4 Chhattisgarh ND 1.96 ND 0.61 0.45 0.54 0.35 0.10 0.10
5 Goa 0.11 0.04 0.02 0.08 0.01 0.00 0.01 0.00 MDA stopped
6 Gujarat 0.22 0.84 0.81 0.35 0.83 0.92 0.46 0.52 0.24
7 Jharkhand ND 0.84 1.40 1.34 1.10 1.11 0.82 0.64 YD
8 Karnataka 1.87 0.84 0.69 1.15 1.07 0.93 0.89 0.83 0.65
9 Kerala 0.68 0.5 0.67 0.65 0.29 0.39 0.17 0.14 0.21
10 Madhya Pradesh 0.83 0.4 0.38 0.70 0.36 0.40 0.19 0.23 0.09
11 Maharashtra 1.13 1.45 1.13 0.83 0.35 0.46 0.53 0.51 0.43
12 Orissa 2.6 2.37 1.11 0.99 0.74 0.69 0.40 0.43 0.19
13 Tamil Nadu 0.04 0.38 0.39 0.29 0.15 0.12 0.07 0.09 NR
14 Uttar Pradesh 1.77 1.01 0.83 0.32 0.41 ND 0.29 0.24 0.38
15 West Bengal 4.74 4.1 2.72 2.83 0.89 0.48 0.44 0.57 YD
16 A&N Islands 1.4 0.09 0.15 0.34 0.19 0.46 0.10 0.12 0.17
17 D & N Haveli 1.96 2.01 2.91 3.47 1.82 1.23 0.95 1.79 0.71
18 Daman & Diu 0.47 0.14 0.27 0.09 0.13 0.07 0.06 0.07 MDA stopped
19 Lakshadweep 1.19 0.09 0.07 0.02 0.27 0.00 0.00 NR NR
20 Pondicherry 0.42 0.5 0.15 0.06 0.03 0.00 0.00 0.00 MDA stopped
  National Average 1.24 1.02 0.98 0.64 0.53 0.65 0.41 0.37 0.45
ND : Not Done || NR: Not Reported
For any scientific publication, if this quoated or used for any analysis purposes, Dte.NVBDCP prior permission must be sought.


The strategy for achieving the goal of elimination is by Annual Mass Drug Administration of Anti Filarial Drugs (DEC+Albendazole) for 5 years or more to the population excluding children below two years, pregnant women and seriously ill persons in affected areas to interrupt transmission of disease.

Home based management of cases who already have the disease and hydrocelectomy operations in identified CHCs and hospitals.

Mass Drug Administration

MDA - 2004

Mass Drug Administration of single dose of DEC was launched as National Filaria Day (NFD) on 5th June 2004 by Dr. A. Ramadoss, Hon'ble Union Minister for Health & Family Welfare in Thane district in Maharashtra . Smt. P. Lakshmi, Hon'ble Union Minister of State for Health & Family Welfare initiated the MDA in Raibareilly district in Uttar Pradesh.In all, 76 districts in 15 states observed MDA on 5th June 2004. In the subsequent months, MDA was completed in 190 districts during 2004. The remaining 12 districts (1 district of Andhra Pradesh and 11 districts of Kerala) took up MDA during February-March 2005.

During the year 2004, 202 filaria endemic districts with a population of about 468 million were targeted under Mass Drug Administration (MDA) for the elimination of lymphatic filariasis. As per reports received from 202 districts, 276 million persons were administered a dose of DEC against eligible population of 378 million, showing a coverage rate of 73%.

Status of MDA - 2005

During the year 2005, 243 filaria endemic districts with a population of over 500 million were targeted. The MDA campaign was launched on 11 November in Jubilee Hall in Hyderabad by Dr. Anbumani Ramadoss, Hon'ble Union Minister for Health & Family Welfare, GoI. The launch ceremony was attended by Smt. Panabaka Lakshmi, Hon'ble Union Minister of State for Health & Family Welfare, GoI, Sh. Konijeti Rosaiah, Hon'ble Minister for Finance, Health, Medical & Family Welfare, Govt. of Andhra Pradesh, Sh. T.K. Dewan, Chief Secretary, Govt. of Andhra Pradesh, Dr. I.V. Subba Rao, Principal Secretary (HM&FW), Govt. of Andhra Pradesh, Dr. P.S. Reddy, Director of Health Services, Andhra Pradesh and Dr. P.L. Joshi, Director, NVBDCP, Delhi. The Hon'ble Minister during the launching of NFD appealed to the public to make this effort as social movement so that country could be made free from lymphatic filariasis by 2015, the goal set in the National Health Policy (2002).

On 11 November 2005, 157districts observed MDA as 4 districts in West Bengal and 14 districts of Tamil Nadu could not observe MDA due to unprecedented rains & flood; 38 districts of Bihar due to elections and 30 districts of Uttar Pradesh due to lack of preparedness. The 4 districts of West Bengal and 38 districts of Bihar however, observed MDA on 22.12.2005 whereas remaining 30 districts of Uttar Pradesh observed MDA on 08.01.2006. Thus 229 districts observed MDA-2005 and Tamil Nadu did not observe MDA-2005 in 14 districts.

During the year 2005 the coverage of 71% was achived against the eligible population of 455 million.

MDA - 2006

National Filaria Day was observed on 22nd December, 2006 for Elimination of Lymphatic Filariasis. Annual single dose of DEC tablets will be administered to all the population living in filaria endemic areas except children below 2 years, pregnant women and seriously ill persons. The mop up round for Mass Drug Administration(MDA) will be carried out on 23rd and 24th December, 2006. During this year only 15 States/UTs could observed MDA with 61% coverage against eligible population of 369 million. The states namely Tamil Nadu, Kerala, West Bengal, Chattisgarh and Pondicherry could not observed MDA.

MDA - 2007

National Filaria Day was observed on 15th November and all the 250 Filaria endemic districts have been covered under MDA with a coverage of 82% against eligible population of 518 million.

MDA - 2008

MDA 2008 was observed on 11th November 2008, however, some states rescheduled the date observed in December, January and February. Tamil Nadu could observe after election. Bihar has not observed MDA 2008 in all the 38 filaria endemic districts. The coverage of eligible population was 86.03% in MDA 2008.

MDA - 2009

Mass Drug Administration (MDA) - 2009 round was staggered starting since 11th November, 2009 and 18 states/UTs observed. State of Uttar Pradesh and Assam could not observe MDA. The reported coverage of MDA by states is 86.70%.

MDA - 2010

Mass Drug Administration (MDA)-2010 round was implemented in 18 out of 20 endemic states/UTs. Tamil Nadu and West Bengal could not observe MDA. The overall coverage reported from 18 states is 84.38%.

MDA - 2011

Mass Drug Administration (MDA) - 2011 round started since Nov, 2011 and 18 out of 20 States have completed with average coverage of about 87.89%. MDA 2011 round in Jharkhand is scheduled on 24th 28th September, 2012. Bihar could not observe MDA-2011 round and in Uttar Pradesh was observed in 14 out of 50 endemic districts.

MDA - 2012

MDA-2012 round started in November 2012. Out of 20 endemic states/UTs, MDA was to be observed in 17 except Goa, Puducherry and Daman & Diu as these were found to be fit for Transmission Assessment Survey (TAS). Transmission Assessment Survey conducted in Goa Puducherry & 1 district of Tamil Nadu and these districts passed for MDA stoppage.

Upscaling Mass Drug Administration


2005: Tamil Nadu in 14 districts not done.
2006: Chhattisgarh (9 districts), Kerala (11 districts), Tamil Nadu(14 districts), West Bengal (12 districts) and Puducherry Not done.
2008: Bihar, 38 districts not done.
2009: Assam (7 districts) and Uttar Pradesh (50 districts) not done.
2010: Tamil Nadu (20 districts) and West Bengal (12 districts) not done.
2011: Bihar (38 districts) and Uttar Pradesh (36 districts) not done. Report of 8 districts (Chattisgarh) yet to be received. Jharkhand (15 districts) yet to observe MDA.
2012: Out of 17 states and UTs, 11 States have completed MDA 2012 round. Out of which 10 states/UTs have reported over all coverage of 87%. In rest 6 states preparation for MDA is in progress.