This ppt contains all the information about the epidemiology of lymphatic filariasis. It is useful for students of the medical field learning Preventive and social medicine, Swasthavritta (Ayurved), and everyone who is interested in knowing about it.

1. Lymphatic Filariasis
Dr. Shubhangi S. Kshirsagar
Assistant professor
Department of Swasthavritta & Yoga
drssksagar@gmail.com

2. Lymphatic Filariasis
▪ The term lymphatic filariasis covers infection
with three closely related nematode worms -
W. bancrafti, B. malayi and B. timori.
▪ Transmitted to man by bite of infected
mosquito
▪ All three parasites have Similar life cycle in
man-adult worm living in lymphatic vessels
with their offspring, the microfilariae circulate
in peripheral blood and are available to infect
mosquito vectors when they come to feed.

3. Culex mosquito
Disease manifestation -
✓ None to both acute & chronic
✓ Not fatal
✓ Responsible for considerable suffering, deformity
& disability.
Mansonia mosquito

6. Periodicity
1. W. Bancrafti and B. malayi (India )
▪ Nocturnal periodicity ( appear in large numbers at
night and retreat from blood stream during day.
▪ Maximum density of Mf – 10pm to 2am
▪ If sleeping habit of the host is altered – reversal
periodicity
2. In south Pacific islands & limited foci in Nicobar
islands Thialand, Viatnam - W. bancrafti micrifilaria
are not periodic (subperiodic) and detectable
throughout 24hrs with slight peak during day or
night.
3. B. malayi – subperiodic in Malaysia & Indonesia.

7. Life cycle
▪ Man – definite host
▪ Mosquito – intermediate host
▪ The adult worm found in the lymphatic system of
man
▪ Male – 40mm long
▪ Female – 50 -100mm long
▪ Viviparous – gives birth to as many as 50000Mf per
day which find their way into blood circulation via
lymphatics
▪ Life span of Mf is not known, probably upto year or
more.
▪ Adult worm may survive for 15 years

8. Life cycle
• Mosquito cycle begins when the Mf are picked up
by the vector mosquito during feeding.
• The following stages of development takes place in
the vector
a. Exsheathing – larva comes out of sheath – within 1-
2 hr of ingestion. It occurs in stomach of mosquito.
b. First stage larva- larva is able to penetrate the
stomach wall of mosquito (6-12hrs) and migrate to
thoracic muscle where it grows & develops into a
sausage shaped form ( short, thick)

9. c. Second stage larva
▪ Larva moults and increase in length (long, thick)
with the development of an alimentary canal, but is
relatively inactive.
d. Third stage larva
▪ Final moult to third stage larva or infective larva
(long, thin) which may be found in any part of the
insect. It is highly active or motile.
▪ When it migrates to proboscis of the mosquito, it is
ready to be transmitted to new host and mosquito is
said to be infective.
➢ Extrinsic incubation period – 10-14days
➢ In human host, infective larva develops into adult
male & female worms

10. Reservoir of infection
1. Animal –
▪ Brugia – monkey, cat, dog
▪ Bancrafti – no animal reservoir
2. Human –
▪ Circulating Microfilaria in peripheral blood
▪ Filarial disease last stage – Microfilaria not
found in blood

11. Host factors
1. Age – infects all age
Infection rate rise with age of 20-30yrs
Decrease in middle & older age
2. Sex – Higher in men
3. Migration
4. Immunity – Man may develop resistance to
infection only after many years of exposure.
5.Social factors – associated with industrialization,
poverty, literacy, poor sanitation

12. Environmental factors
1. Climate –Climate influences the breeding of
mosquitoes, their longevity and also determines
the development of the parasite in the insect
vector. The maximum prevalence of C. fatigans
was observed when the temperature was
between 22 to 38 deg. C and optimum longevity
when the relative humidity was 70 %.
2. Drainage –
✓ Associated with bad drainage, polluted water
✓ Vector breed profusely in polluted water
3. Town planning- Lack of town planning,
inadequate sewage disposal

13. Vectors
▪ Culex, Anaphelus, Ades serves as vectors for
W. Bancrafti
▪ Mansonia, Anophelus serves as vector for
Brugia
▪ Main vector in India
1. Culex fatigans – Bancraftian filariasis
2. Mansonia – Brugian filariasis

14. The breeding of Mansonia is associated with
certain aquatic plant – Pista stratiotes.

15. Mode of transmission
Filariasis is transmitted by-
Bite of infected vector mosquito
Parasite deposited near the site of puncture
Punctures skin/penetrate skin
Reach to lymphatic system

16. Incubation period
▪ The time interval from invasion of infective
larvae to the development of clinical
manifestations is known as the clinical
incubation period.
▪ This period is 8 to 16 months or longer

17. Clinical manifestation – 2 clinical types
A. Lymphatic filariasis
▪ Caused by the parasite in the
lymphatic system
▪ Stages in lymphatic filariasis
are -
1. Asymptomatic amicrofilaria
2. Asymptomatic microfilaria
3. Stage of acute manifestation
4. Stage of chronic obstructive
lesion
B. Occult filariasis
Caused by immune
hyper
responsiveness of
human host
Ex. Tropical
pulmonary
esinophilia

18. Lymphatic filariasis
1. Asymptomatic amicrofilaria
In endemic areas –proportion of population does not
shows Mf or clinical manifestation of disease –
although they have same degree of exposure.
2. Asymptomatic microfilaria
▪ Asymptomatic but blood positive for Mf
microfilaria.
▪ They may remain without any symptoms for
many months or years.
▪ Important source of infection in the community.
▪ Carrier detected by night blood exam.

19. 3. Stage of acute manifestation
In first month & years –there are recurrent episode
of acute inflammation in lymph glands & vessels.
Clinical manifestation-
▪ Filarial fever
▪ Lymphangitis, lymphadenitis, lymphoedema of
various part of the body
▪ Male – epidymo-orchitis

20. 4. Stage of chronic obstructive lesions
▪ It develops 10-15years from onset first acute attack.
▪ This phase is due to fibrosis & obstruction of
lymphatic vessels causing permanent structural
damage.
▪ In chronic Bancraftian filariasis, the main clinical
features are hydrocele, elephantitis and chyluria.
▪ Elephantitis may affect the legs, scrotum, arm, penis,
vulva& breast usually in order of decreasing
frequency.
▪ Prevalence of Chyluria is usually very low.
▪ Brugian filariasis – similar to Bancraftian fileriasis,
but genitalia are rarely involved.

23. Lymphoedema treatment
1. Treatment for uncomplicated ADLA
(Acute dermato lymphangioadenitis)
▪ Give analgesic such as paracetamol
▪ Give oral antibiotic such as amoxicillin for at
least 8 days.
▪ Clean the limb with antiseptic.
▪ Check for any wounds, cuts, abscesses and
interdigital infection (especially between the
toes) and Clean with antiseptic.
▪ If local superficial skin infection is found
give antibiotic cream, apply antifungal cream
if interdigital infection is present.

24. ▪ Give advice about prevention of chronic
lymphoedema caused by lymphatic filariasis;
▪ Do not give antifilarial medicine.
▪ Home management includes drinking plenty
of water, rest, elevation of the limb, wriggling
the toes, cooling the limb with cold water and
washing the limb if the patient can do it; an
▪ Follow-up after 2 days at home.
▪ If situation does not improve, then refer the
patient to physician

25. Management of severe ADLA
▪ Refer the patient to physician immediately to
receive following antibiotic treatment-
✓ Benzylpenicillin (Penicillin G) 5 million units
given 3 times a day
✓ Phenoxymethylpenicillin (penicillin V) 750 mg to
1gm given 3 times/day.
✓ In case of allergy to penicillin, give IV
erythromycin1g 3 times/day until fever subsides,
then give oral erythromycin 1g given 3 times/day
▪ Give analgesic /antipyretic such as paracetamol
▪ Do not give any antifilarial medicine

28. Filaria survey
Routine survey -5-7% population
Evaluation survey – 20% population
1. Mass blood survey
2. Clinical survey
3. Serological tests - to detect antibodies to Mf
4. Xenodiagnosis
5. Entomological survey

29. Mass blood survey/night blood survey
Diagnosis depends on demonstration of living
parasite in human body.
a. Thick film – capillary blood – 8:30pm to 12 am
b. Membrane filter concentration (MFC)
✓ Venepuncture – filtering large volume of blood
✓ For detection of low density Mf
c. DEC provocation test
✓ Administration of DEC 100mg orally
✓ Mf begins to reach their peak 15 minutes and
begin to decrease 2 hours later.
✓ Blood may be examined 1 hr after administration
of DEC

30. Control measures
▪ The current strategy of filariasis control is
based on –
1. Chemotherapy
a. Diethylcarbamazine
b. Filaria control in the community
c. Ivermectin
2. Vector control

31. 1. Chemotherapy
a. Diethylcarbamazine (DEC)
▪ Effective in killing Mf
▪ Safe
▪ Oral – rapidly absorbed
▪ Reaches peak blood level within 1-2hrs
▪ Rapidly excreted
Type of filariasis DEC dose
Bancrafian filariasis 6mg/Kg body weight for 12 days
Brugian filariasis 3-6mg/Kg body weight

32. b. Filaria control in the community
Filaria control
in the
community
Mass therapy
Selective
treatment
DEC
medicated
salt

33. i. Mass therapy
▪ DEC is given to almost everyone in the
community irrespective of whether they have
microfilaraemia, disease manifestations or no
signs of infection
▪ Contraindication - children under 2 years,
pregnant women and seriously ill patients.
▪ Dose - 6 mg/kg body weight
▪ Indicated in highly endemic areas.

34. ii. Selective treatment
▪ For Mf positive
▪ Indicated in low endemic areas
▪ Dose – 6mg/Kg per body weight for 12days
In endemic areas, treatment must be repeated at
specified intervals; usually every 2yrs.
iii. DEC medicated salt
Common salt medicated with 1-4gm of DEC per Kg
for 6-9months

35. c. Ivermectin
▪ Ivermectin is a semisynthetic macrolide
antibiotic with a broad spectrum of activity
against a variety of nematodes and
ectoparasites.
▪ Dose - 150-200 µg/kg of body weight
▪ Not used in India, used in Africa

36. 2. Vector control
▪ Vector control may be beneficial, when used in
conjunction with mass treatment.
▪ The most important element in vector control is
the reduction of target mosquito population in
order to stop or reduce transmission quickly.
▪ It consist of
i. Anti larval measures
ii. Anti adult measures
iii. Personal prophylaxis

37. i. Anti-larval measures
Elimination of breeding places by providing adequate
sanitation & underground waste water disposal
system
a. Chemical control
▪ Mosquito larvicidal oil
▪ Pyrosene oil- E
▪ Organophosphrous larvicides
b. Removal of Pistia plant ( Mansonia)
▪ Mosquito breeding is controlled by (for mansonia
mosquito) converting ponds to fish or lotus culture.
▪ Herbicide shell weed killer D – for destroying the
aquatic vegetation.

38. c. Minor environmental measures - Filling up
ditches, drainage of stagnant water , adequate
maintenance of septic tank & soakage pit.
ii. Anti-adult measures
Pyrethrum space spray
iii. Personal prophylaxis - avoidance of
mosquito bites (reduction of man-mosquito
contact) by using -
✓ Mosquito nets
✓ Screenings
✓ repellents

39. Thank You !