Presentation on Epidemiology and control of filariasis (Lymphatic Filariasis) in India

1. Epidemiology and
Control of Filariasis
-Reshma Ann Mathew
1

2. FILARIASIS
 Filariasis refers to infection with filarial worms.
 It is transmitted to humans by the bite of infected
vector mosquitoes.
2
 Based on pathogenicity and habitat it classified
into:
1) Lymphatic filariasis
2) Subcutaneous filariasis
3) Serous cavity filariasis
4) Zoonotic filariasis

3. Lymphatic Filariasis
 It is a public health problem in India.
 Lymphatic filariasis is a vector-borne parasitic
disease.
 The disease is caused by thread-like, parasitic
filarial worms: Wuchereria bancrofti(about 95%
cases), Brugia malayi, and Brugia timori.
3

4. 4
Heavily infected areas include UP, Bihar,
Jharkhand, Andhra Pradesh, Orissa, TN,
Kerala and Gujarat.

5. It is endemic in many tropical & subtropical
countries like Africa, Asia, Western Pacific and
parts of America. 5

6. 1.4 billion people live in areas
with risk of infection
Out of them, 120
million are infected
and need treatment
Out of them, 40 million people are
with overt disease
15 million people
with lymphoedema
25 million men
with urogenital
swelling mainly
scrotal hydrocele
6

7. 7
 Mass drug administration (MDA) of DEC was
implemented in India since 2004
 In 2007, the strategy of MDA changed to DEC
plus albendazole.
 In 2012, the prevalence of microfilaria reduced
to less than 1% in 192 out of 250 implementation
units.

8.  The formal goal of the global lymphatic
filariasis programme:
i. to eliminate the disease as a public health
problem
ii. 2020 is the informal target date for interrupting
transmission.
8

9. Epidemiology
1) AGENT FACTORS-
 There are atleast 8 species of filarial parasites
that are specific to man.
 They are Wuchereria bancrofti, Brugia malayi,
Brugia timori, Onchocerca volvulus, Loa loa, T
perstans, T streptocerca, Mansonella ozzardi
 Out of these, the first 3 cause lymphatic
filariasis. 9

10. PERIODICITY-
 Both the microfilaria(Mf) of W. bancrofti and B.
malayi occurring in India display nocturnal
periodicity, i.e. appear in large no. at night,
retreat from blood stream during the day.
 The maximum density is reported between
10pm to 2am.
 This is a biological adaption to the nocturnal
biting habits of the vector mosquitoes. 10

11. LIFE CYCLE
Definitive host-Man, Intermediate host- Mosquito
 The adult worms (macrofilaria) are found in the
lymphatic system of man, where they may survive for
15yrs or more.
 During their lifespan, after mating, female worms
(viviparous) give birth to 50,000 immature
microfilariae(mf) per day into the blood circulation via
lymphatics. They may survive up to a year or more.
 Some of these microfilariae may be ingested by the
mosquitoes during their blood meal.
11

12.  Stages in the mosquito-
1) Exsheathing- The larva comes out of the sheath in
which it was enclosed. Occurs in stomach of the
mosquito.
2) First stage larva-The larva penetrates the stomach
wall of the mosquito, and migrate thoracic muscles
where it develops into a short thick form
3) Second stage larva-The larva moults and increase
in length
4) Third stage larva(INFECTIVE)-The larva
moults and develops into a long thin form which
migrates to the proboscis of the mosquito. The
mosquito is said to be infected.
12

13. 13

14. INCUBATION PERIOD
 The time interval from invasion of infective
larvae to the development of clinical
manifestations-CLINICAL INCUBATION
PERIOD
 It is about 8-16months
14

15. RESERVOIR OF INFECTION
 Although filarial infection occurs in animals, human
filariasis is not usually a zoonosis.
 In man, the source of infection is a person with
circulating Mf in peripheral blood.
 In filarial disease (late obstructive stages), Mf are
not found in the blood.
 The minimum level of Mf which will permit
infection of mosquitoes is not known.
15

16. VECTORS OF LYMPHATIC FILARIASIS
 In India,
i. Culex (C. quinquefasciatus)- vector for
Bancroftian filariasis
ii. Mansonia(M. annulifers & M. uniformis)- vector
for Brugian filariasis
 Culex breeds in polluted water
 Mansonia is associated with certain aquatic plants
(such as Pistia stratiotes)
16
Culex
Mansonia

17. 2) HOST FACTORS-
Man is a natural host.
a) AGE
 All ages are susceptible to infection.
 The infection rates rise with age up to 20-30 yrs
and then level off
b) GENDER
 In most endemic areas, Mf rate is higher in men
c) MIGRATION
 Migration led to the extension of filariasis into
non-endemic areas
17

18. d) IMMUNITY
 Resistance is developed only after years of
exposure
e) SOCIAL FACTORS
 Lymphatic filariasis is associated with poor
sanitation, urbanization, migration of people,
etc.
18

19. 3) ENVIRONMENTAL FACTORS
a) CLIMATE –
 It influences the breeding of mosquitoes, their longevity and
the development of parasite in insect vector.
 Max. prevalence of the mosquito was seen between 22-38 °C
and relative humidity of 70%
b) DRAINAGE –
 Vectors breed profusely in polluted water.
c) TOWN PLANNING –
 Inadequate sewage disposal and lack of town planning have
aggravated the problems of filariasis in India.
 The common breeding places are open ditches, septic tanks,
ill-maintained drains.
19

20. 20

21. CLINICAL MANIFESTATIONS
 Only a small proportion of infected individuals
exhibit clinical signs
 They are of 2 types:
i. Lymphatic Filariasis- caused by the parasite in
the lymphatic system.
ii. Occult Filariasis- due to immune hyper-
responsiveness of the human host.
21

22. 1) LYMPHATIC FILARIASIS-
It has the following stages-
a) Asymptomatic amicrofilaremia- does not show
Mf or clinical manifestations of the disease.
b) Asymptomatic microfilaremia- Asymptomatic, but
blood is positive for Mf.
c) Stage of acute manifesations-
 Occurs in first few months and years
 Recurrent episodes of acute inflammation in
lymph glands & vessels
 Manifested as filarial fever, lymphangitis,
lymphadenitis, lymphoedema & epididymo-
orchitis(male).
22

23. d) Stage of chronic obstructive manifestations-
 Occurs 10-15yrs after the onset of first acute attack.
 Causes permanent structural changes due to fibrosis
and obstruction
of lymphatic vessels.
 Main clinical features are
hydrocele, elephantiasis &
chyluria.
 In Brugian filariasis, genitalia are
rarely involved. 23

24. 24

25. 25

26. 2) OCCULT FILARIASIS-
 The classical clinical manifestations are NOT
PRESENT and Mf are NOT FOUND in the
blood.
 Occurs due to hypersensitivity reaction to
filarial antigens derived from Mf.
 Eg: Tropical pulmonary eosinophilia.
26

27. LYMPHOEDEMA MANAGEMENT
1) Treatment for Uncomplicated ADLA( acute
dermato-lymphangioadenitis)
 Give analgesic-paracetamol (1g, 3-4times a
day)
 Give oral antibiotic-penicillin(1.5g in 3 divided
doses X 8days). In case of allergy to penicillin,
give oral erythromycin(1g, 3times a day)
 Clean the limb with antiseptic
 Check for any wounds, cuts, abscesses {give
antibiotic cream} and interdigital infection
{give antifungal cream}.
27

28.  Give advice on prevention of chronic
lymphoedema
 DO NOT give antifilarial medicine
 Home management- elevation of limb, drink
plenty of water, wriggling the toes, washing
the limb.
 Follow up after 2 days.
28

29. 2) Management Of Severe ADLA
 Refer patient to physician, he is given-
i. IV benzylpenicillin (Penicillin G)-3g, 3 times
a day, until fever subsides.
Then, oral phenoxymethylpenicillin
(Penicillin V)-750mg to 1g, 3times a day X
8days
ii. In case of allergy to penicillin, IV
erythromycin 1g 3times/day until fever
subsides.
Then, oral erythromycin 1g, 3times a day.
 Give anagesic/antipyretic-paracetamol
 DO NOT give antifilarial medicine.
29

30. 30

31. 31

32. HYDROCELE MANAGEMENT
 The individuals are referred for diagnosis and
surgery done if necessary.
 Men have a good prognosis with early
hydrocele and corrective surgery can be
undertaken even with local anaesthetic.
 Quality pre- and post-operative care are
important components that help make this
surgery successful. For other genital damage,
more complicated surgery is often required.
 Unfortunately, however, hydrocele surgery is
often too expensive for those afflicted with LF.
32

33. Filaria Survey
 It is done for routine survey or survey for
evalution.
 The NICD (National Institute of Communicable
Diseases) standard is to examine 5-7% of the
population for routine surveys and 20% for
evaluation studies.
 It consists of-
1) Mass blood survey
2) Clinical survey
3) Serological tests
4) Xenodiagnosis
5) Entomological survey
33

34. 1) Mass Blood Survey-
 It depends upon the demonstration of living parasites
in the human body. Night blood surveys are done
i. Thick film-
 Most commonly used method
 20mm3 of blood is collected by a deep finger
prick between 8.30pm and 12 mid-night.
 The blood films are dehaemoglobinised, stained,
dried and examined for Mf under low power.
ii. Membrane filter concentration-
 Most sensitive method for detecting low density
microfilariaemia.
34

35. iii. DEC provocation test-
 Mf can be induced to appear in blood in the
daytime by administering DEC100mg
orally.
 Mf begin to reach their peak within
15minutes and begin to decrease 2hrs
later.
35

36. 2) Clinical Survey
 People are examined for clinical manifestations
of filariasis.
3) Serological tests
 To detect antibodies to Mf and adults using
immunoflorescent and complement fixing
techniques.
 But , CANNOT DISTINGUISH between past
and present infection, and heavy and light
parasite loads.
36

37. 4) Xenodiagnosis
 Mosquitoes are allowed to feed on the patient,
and then dissected 2weeks later.
5) Entomological survey
 It consists of:
i. general mosquito collection from houses
ii. dissection of female vector species for
detection of developmental forms of the parasite
iii. Study of the extent and type of breeding
places.
37

38. Assessment of Filarial Control Programmes
 It can be assessed using:
1) Clinical parameters
2) Parasitological parameters
3) Entomological parameters
38

39. 1) CLINICAL PARAMETERS
Incidence of acute manifestations and
prevalence of chronic manifestations are
measured.
2) PARASITOLOGICAL PARAMETERS
i. Microfilaria rate- It is the % of people
showing Mf in their peripheral blood in the
sample population.
39

40. ii. Filarial endemicity rate- It is the % of people
examined showing microfilariae in their blood, or
disease manifestation or both.
iii. Microfilarial density- It is the no. of Mf per unit
volume of blood in samples from individual people.
 It indicates the intensity of infection
iv. Average infestation rate- It is the average no. of Mf
per positive slide.
 It indicates the prevalence of microfilaraemia in
the population.
40

41. 3) ENTOMOLOGICAL PARAMETERS
They comprise
i. Vector density per 10 man-hour catch
ii. % of mosquitoes positive for all stages of
development
iii. % of mosquitoes positive for infective larvae
iv. Annual biting rate
v. Types of larval breeding places
41

42. Control Measures
 Previously, even after full regimen of
Diethylcarbamazine(DEC), some microfilariae still
persisted in the body. So it was difficult to prevent
the spread of filariasis.
 So it is supplemented by an effective vector control
programme.
 The current strategy is based on-
i. Chemotheraphy
ii. Vector control
42

43. CHEMOTHERAPY
1) DEC
2) Filaria control
in the
community
a) Mass Therapy
b) Selective
Treatment
c) DEC-
medicated salt
3) Ivermectin
43

44. 1) DEC
 It is safe and effective.
 Given in divided doses after meals
 Rapidly absorbed
 Reaches peak blood levels in 1-2hrs
 Rapidly excreted
44
Filariasis Dose
1) Bancroftian filariasis 6mg/kg body weight per
day orally for 12 days
2) Brugian filariasis 3-6mg/kg body weight per
day orally for 12 days

45.  DEC is effective in killing Microfilaria.
 Adverse effects-
i. Due to the drug itself- headache, nausea,
vomiting, etc. They are seen few hours after the
first dose, but do not last for more than 3 days.
ii. Allergic reactions due to destruction of
microfilariae and adult worms-fever, local
inflammations around dead worms, orchitis,
lymphadenitis and hydrocele. They occur later and
last longer.
 If these drugs are given in spaced doses, the
adverse reactions are much less frequent and less
intense.
45

46. 2) Filaria control in the community
2) Filaria control
in the community
a) Mass Therapy
b) Selective
Treatment
c) DEC-
medicated salt
46

47. a) Mass therapy-
 DEC is given to everyone in the community
irrespective of whether they have
microfilaraemia, disease manifestation or no
signs of infection; except children under 2yrs,
pregnant women and seriously ill patients.
 Dose: DEC 6mg/kg body weight
 Indicated in highly endemic areas
47

48. b) Selective treatment
 DEC given only to those who are Mf positive.
 More suitable in low endemicity areas
 Dose: 6mg DEC per kg body weight daily for
12 doses
 In endemic areas, it should be repeated every
2yrs
48

49. 3) DEC-medicated salt-
 Common salt is medicated with 1-4g of DEC per
kg.
49

50. 3) Ivermectin
 It is a semisynthetic macrolide antibiotic with
broad spectrum activity against nematodes and
ectoparasites.
 It is NOT USED in India, used in Africa
 In normal people, there is no drug toxicity. But,
in microfilaraemic patients, there may be
reactions due to inflammatory response due to
the dying microfilariae.
50

51. Vector Control
 Vector control is beneficial when used in
conjunction with mass treatment.
 The most important step is to reduce the target
mosquito population to stop or reduce the
transmission.
 It consists of:
i. Anti-larval measures
ii. Anti-adult measures
iii. Personal prophylaxis
51

52. 1) Anti-larval measure
 It consists of –
a) CHEMICAL CONTROL-
i. Mosquito larvicidal oil
 Active against all pre-adult stages
 Used to control Culex
 Very expensive than others
ii. Pyrosene oil-E
 It is a pyrethrum based emulsifiable
larvicide
iii. OP larvicides
 Widely used, but resistance developed
against many
 Eg: temephos, fenthion.
52
MLO
Temephos
Fenthion

53. b) REMOVAL OF PISTIA PLANT-
 To control breeding of Mansonia mosquitoes
 Done by either converting the pond to fish or
lotus culture (OR) using herbicides such as Shell
Weed Killer D
c) MINOR ENVIRONMENTAL MEASURES-
 It includes:
i. Drainage of stagnant water
ii. Adequate maintenance of septic tanks
53
Pistia plant

54. 2) Anti-Adult measures
 Previously, DDT was used. But, it has
been discontinued
 Pyrethrum is now used as a space spray.
54

55. 3) Personal prophylaxis
 Avoidance of mosquito bites by using
mosquito nets
 Screening
 Repellents
55

56. INTEGRATED VECTOR CONTROL
 None of the vector controls applied alone
is likely to bring about filariasis control. It
has to be an integrated approach.
1) Development of annual drug treatment
2) Intensive personal hygiene
3) DEC-medicated salt
4) Development of insecticide sprays
56

57. NATIONAL FILARIA CONTROL
PROGRAMME
 It is operational since 1955
 In June 1978, it was merged with malaria scheme.
 Filaria control strategy includes
i. vector control through anti-larval operations
ii. Source reduction
iii. Detection and treatment of
microfilaria carriers
iv. Morbidity management
57

58.  The strategy is through:
i. Annual Mass Drug Administration(MDA)
ii. Home based management- of lymphoedema
and upscaling of hydrocele operations.
 To achieve elimination, in 2004 the Govt. of
India launched annual MDA with single dose of
DEC along with home based foot care and
hydrocele operation
 The co-administration of DEC + Albendazole
was introduced in 2007
58

59. 59