UG MBBS class on filariasis

1. Lymphatic Filariasis
Dr .C.SASHIDHARAN
Assistant Professor
Dept of Community Medicine
MAPIMS

2. Introduction
• Lymphatic filariasis,
• Commonly known as elephantiasis
• A neglected tropical disease.
• Infection occurs when filarial parasites are transmitted to humans through
mosquitoes.
• Infection is usually acquired in childhood causing hidden damage to the lymphatic
system.

3. Global Burden
• Currently, 1.4 billion people in 73 countries are living in areas that require
preventive chemotherapy to stop the spread of infection.
• Approximately 80% of these people are living in the following 10 countries:
Angola, Cameroon, Democratic Republic of the Congo, India, Indonesia,
Mozambique, Myanmar, Nigeria and the United Republic of Tanzania.

4. The disease manifestations range from none to both acute and chronic
manifestations
• Lymphangitis, lymphadenitis,
• elephantiasis of genitals, legs and arms or
• as a hypersensitivity state such as tropical pulmonary eosinophilia or
• as an atypical form such as filarial arthritis.
• Though not fatal, the disease is responsible for
considerable suffering, deformity and disability.

5. Epidemiological determinants
Agent factors:
There are at least 8 species of filarial parasites that are specific to man.

6. Causative Organism Vectors Diseases produced
Lymphatic W.Bancrofti culex Lym filariasis
Brugia malayi Mansonia Lym filariasis
B.timori Anopheles
Mansonia
Lym filariasis
Sub
cutaneous
Onchocerca volvulus, Simulum flies Sub cut nodules
River blindness
Loa loa Chrysopes Sub cut nodule
Mansonella streptocerca Culicoides Rarely
serous Mansonella perstans, Culicoides Rarely
M.ozzardi. culicoides Rarely

7. • Lymphatic filariasis is caused by infection with parasites classified as
nematodes (roundworms) of the family Filariodidea
1. Wuchereria bancrofti, which is responsible for 90% of the cases
2. Brugia malayi, which causes most of the remainder of the cases
3. Brugia timori, which also causes the disease.

8. Culex quinquefasciatus
Mansonia annulifera

9. PERIODICITY:
 The Mf of W. bancrofti and B.malayi occurring in .India display a
nocturnal periodicity.
 This is a biological adaptation to the nocturnal
habits of the vector mosquitoes
 The maximum density in blood is reported between 10 pm and 2 am
 When the sleeping habits of the host are altered, a reversal in periodicity
has been observed.

10. Wuchereria bancrofti
• the causative organism for filaria transmitted by the ubiquitous vector,
Culex quinquefasciatus,
• has been the most predominant infection contributing to 99.4% of the
problem in the country.
• Although the vector species breeds preferably in dirty and polluted
water, it can also breed in clear water in the absence of polluted water.
• The infection is prevalent in both urban and rural areas

11. Brugia malayi
• mainly rural areas due to peculiar breeding habits of the vector associated
with floating vegetation.
• Mansonia (Mansonioides) annulifera- principal vector M.(M).uniformis
is the secondary vector for transmission
• The breeding of these mosquitoes is associated with aquatic plants such as
Pistia stratiotes. In the absence of these plants, the vectors cannot breed.
• The vectorial role of M. (M). indiana is very limited due to its low
density.

12. • Both W. bancrofti and B. malayi infections in mainland India exhibit
nocturnal periodicity of microfilaraemia.

13. Life cycle
• Man is the definitive host and mosquito the intermediate host of
Bancroftian and Brugian filariasis.
• The adults worms are usually found in the lymphatic system of man. The
males are about 40 mm long and the females 50 to 100 mm long.
• The females are viviparous

14. • Adult worms lodge in the lymphatic system and disrupt the immune
system.
• The worms can live for an average of 6–8 years and, during their life time,
produce millions of microfilariae (immature larvae) that circulate in the
blood.

15. LIFE CYCLE OF FILARIAL PARASITE
exsheathing

16. RESERVOIR OF INFECTION
• Although filarial infections occur in animals. Human filariasis is not
usually a zoonosis
• Animal reservoirs of Brugia,
present in monkeys, cats and dogs; these animals are believed to acquire
their infections from man. and they are not regarded as important sources
of infection to man

17. Host factors
•Man is the natural host
•Age:
All ages are susceptible to infection
• infected early in childhood
microfilaremia peaks between 15-20years
plateaus in adult life.
declines in middle and old age

18. • Sex : Equally susceptible
• Immunity: Man may develop resistance to infection only after many years of
exposure
• SOCIAL FACTORS : Lymphatic filariasis is often associated with
urbanization, industrialization, migration of people, illiteracy, poverty and
poor sanitation

19. Environmental factors
Climate:
• It influences the breeding of mosquitoes, their longevity and also determines
the development of the parasite in the insect vector
• Tropical climate favorable
• Humidity: 80%
• Temperature: 20- 40 degrees

20. • DRAINAGE:
lymphatic filariasis is associated with bad drainage. The vectors breed
profusely in polluted water
• Town Planning : The common breeding places are cesspools, sokage pits.
ill-maintained drains, septic tanks, open ditches

21. Vectors of lymphatic filariasis
• The main vectors in India are : C. quinquefasciatus(C. fatigans) for
Bancroftian filariasis,
• Monsonia (mansonoides) mosquitoes (e.g.., M.annulifers and M.Uniformis) for
Brugian filariasis.

22. MODE OF TRANSMISSION
Bite of infected mosquitoes (culex quinquefasciatus)
INCUBATION PERIOD
 Pre patent period- Time interval between inoculation of the infective
microfilaria and the first appearance of microfilaria in peripheral blood

23.  Extrinsic incubation period- Time taken from the entry of microfilaria
in mosquito till the development of infective 3rd stage larva
 Clinical incubation period- Time interval from invasion of microfilaria
till the development of clinical manifestations i.e.,8 to 16months

24. DISEASE MANIFESTATION
Divided into 2 distinct clinical types:
1)Lymphatic filariasis caused by the parasite in the lymphatic system
2)Occult Filariasis caused by immune hyperresponsiveness of the
human host(eg. Tropical pulomonary eosinophilia)

25. LYMPHATIC FILARIASIS
1. Asymptomatic amicrofilaraemia - does not show Mf or clinical manifestations
of the disease.
2. Asymptomatic microfilaraemia – asymptomatic but blood is positive for Mf.
Important source of infection in the community.

26. 3. Stage of acute manifestation – first months and yrs there are recurrent
episodes of acute inflammation in the lymph glands and vessels
4. Stage of chronic obstructive lesion – develops 10-15 yrs from the onset
of the first acute attack. Due to fibrosis and obstruction of the lymphatic
vessels causing permanent structural changes.

27. Occult or Cryptic filariasis refers to filarial infections in which the classical
clinical manifestations are absent and Mf are not found in the blood .
Believed to result from a hypersensitivity reaction to filarial Ag derived from
Mf.

28. • A definitive diagnosis can be made only by detection of the parasites.
• Identification of microfilariae in a blood
smear by microscopic examination.
• The microfilariae exhibit nocturnal periodicity with surges of circulating
microfilariae at night. Blood collection should be done at night to coincide with
the appearance of the microfilariae.

29. MANAGEMENT
Lymphoedema management:
In areas with lymphatic filariasis, improving the quality of life by activities such
as –
-early detection of lymphoedema
-caring for the skin by washing
-drying the affected limb or area
-preventing and treating entry lesions and providing lymph drainage by
elevating the limb and exercising

31. Guidelines by WHO to manage ADLA (Acute Dermatolymphangioadenitis)
:
-Treatment for uncomplicated ADLA
-Treatment for complicated ADLA

32. • Treatment for uncomplicated ADLA
 Give analgesic- paracetamol (1gm 3times a day)
 Give oral antibiotic-amoxicillin (1.5gm in 3doses) or oral penicillin
should be given for 8 days
 Clean the limb with antiseptic

33.  Any superficial infection antibiotic or antifungal cream should be applied
 Give advice on prevention of lymph edema
 DO NOT GIVE Anti filarial medicine
 Home management and follow up after 2 days

34. Treatment for complicated ADLA
 Refer the patient to physician immediately
 Antibiotic treatment-iv penicillin G 5million units or procaine benzyl
penicillin 2million units
 Give analgesic or antipyretic
 Do not give anti filarial medicine during acute attacks.

36. Antifilarial treatment
• All people with filariasis who are positive in the immunochromatographic
test or have microfilaraemia should receive anti-filarial drug treatment to
eliminate microfilariae

37. Regimens
• (i) a single dose of a combination of
albendazole (400 mg) with ivermectin (150–200 µg/kg) in areas where
onchocerciasis
is co-endemic
• In areas where onchocerciasis is non co-endemic, either
(ii) a single dose of a combination albendazole (400 mg) plus
diethylcarbamazine (6 mg/kg) or
(iii) diethylcarbamazine 6 mg/kg alone for 12 days

38. FILARIA SURVEY
Mass blood survey-
• Thick film- Giemsa stained
• Membrane filter concentration- for detecting low density
microfilaraemia in blood
• DEC provocation test- Mf can be induced to appear in blood in the day
time by administering DEC 100mg orally. Blood may be examined 1hr
after the administration.

39. 2. Clinical survey- examined for clinical manifestations
3. Serological tests- detection of parasite antigens in patients blood or urine,
CFT
4. Imaging - CT,MRI may reveal "Filarial Dance Sign" in Chylus fluid. X-
ray can show calcified adult worm in lymphatics

40. 5. Xenodiagnosis: the mosquitoes are allowed to feed on the patient and then
dissected 2 weeks later
6. Epidemiological survey

41. Assessment of filaria control programme
Clinical parameters-
 Incidence of acute manifestations
 Prevalence of chronic manifestations
Parasitological parameters-
 Microfilaria rate
 Filarial endemicity rate
 Microfilaria density
 Average infestation rate

42. Entomological parameters-
 Vector density per 10 man hour catch
 Percentage of mosquitoes positive for all stages of development
 Percentage of mosquitoes positive for infective larvae
 Types of larval breeding places

43. Filaria control in the community- Chemotherapy
 Mass treatment-every member of the community irrespective of infection
are treated with DEC
 Selective treatment-DEC is given to those who are microfilaria positive
 DEC medicated salt-fortified common salt medicated with 1-4gm DEC
per kg is used in endemic areas
 Ivermectin-oral dose of 20-400micro gm per kg is effective in clearing
Mf

44. Filaria control in the community- Vector control
• Antilarval measures-
-Chemical control: mosquito larvicidal oil
Pyrosene oil-E
Organophosphorous compounds
Removal of pistia plant
Minor environmental measures

45. • Antiadult measures-pyrethrum is used as space spray,
• Personal prophylaxis-avoid mosquito bites by using mosquito nets and
repellants

46. Elimination of Filariasis

47. Interrupting transmission
• Annual mass administration of a combination of two drugs to entire
populations at risk.
• Albendazole (400 mg)
plus
either diethylcarbamazine (6 mg/kg)
in areas without onchocerciasis or loiasis,
or
ivermectin (150–200 µg/kg) in areas
where onchocerciasis and lymphatic filariasis are co-endemic

49. Previous year questions
• Long question :
• (1) Discuss the epidemiology, prevention and
control of Lymphatic Filariasis.
• Short Notes :
• (1) Clinical Spectrum of Filariasis
• (2) Treatment of Lymphatic Filariasis and mass treatment regimen.

50. Thank you