3. Lymphatic filariasis:
Lymphatic filariasis is a parasitic disease caused by infection with three
closely related nematode (roundworms) worms: W. bancrofti, B. malayi
and B. timori.
These species are responsible for two main types of LF:
Bancroftian Filariasis:(90%) Brugian Filariasis:
Causative
Agent:
Wuchereria bancrofti Brugia malayi and Brugia timori
Vector: Culex Quinquefasciatus
(A/K/A: C. Fatigans)
Mansonia
4. LIFE CYCLE:
The adult worms are usually found in lymphatic vessels of man.
The females are viviparous and give birth to as many as 50,000 Mf
per day.
The microfilariae circulate in peripheral blood and are available to
infect mosquito vectors when they come to feed.
Definitive Host: Man
Intermediate host: Mosquito
5. .
.
Lymphatic damage, scaring and obstruction: Severe swelling of the
legs, arms, breasts, or genitals.
Pain
Severe disability
Social stigma
Adult worms rest in the lymphatic vessels and causes hidden
damage to the lymphatic system.
6. Adult worms rest in the lymphatic vessels and disrupt the normal function of
the lymphatic system. The worms can live for approximately 6–8 years and,
during their lifetime, produce millions of microfilariae (immature larvae) that
circulate in the blood.
Mosquitoes are infected with microfilariae by ingesting blood when biting an
infected host. Microfilariae mature into infective larvae within the mosquito.
When infected mosquitoes bite people, mature parasite larvae are deposited
on the skin, from where they can enter the body. The larvae then migrate to
the lymphatic vessels where they develop into adult worms, thus continuing a
cycle of transmission.
7.
8. Epidemiology of Lymphatic filariasis:
This includes 15 million people with lymphoedema and 25 million men
with urogenital swelling principally scrotal hydrocele.
Global: More than 1.4 billion people live in areas where there is a risk
of infection, of whom 120 million are infected and in need of treatment,
including 40 million people with overt disease.(WHO)
Filariasis is a global problem.
Lymphatic filariasis is common in tropical and sub-tropical climates of
Africa, Asia, West pacific and parts of America, affecting over 73 countries.
9. Nepal:
Lymphatic filariasis is a public health problem in Nepal.
The disease is more prevalent in rural areas, predominantly affecting
poorer people.
Total endemic district in Nepal is: 61
Average prevalence of lymphatic filariasis: 13%
The disease has been detected from 300 feet above sea level in the
Terai to 5,800 feet above sea level in the Mid hills.
Terai > Hill
10.
11. Epidemiological determinants of LF:
Agent factors: Host factors: Environmental and social factors:
W. bancrofti
(90%),
B. malayi
B. timori.
Man is a natural
host.
AGE: LF affects all
ages.
SEX: Male >
Female
CLIMATE: Between 22- 38 °C
DRAINAGE: LF is associated with bad
drainage.
TOWN PLANNING: Inadequate sewage
disposal and lack of town planning.
Urbanization, industrialization,
Illiteracy, Poverty,
Poor sanitation.
12. PERIODICITY: Cyclical pattern of Mf in the bloodstream
The Mf of W. bancrofti and B. malayi have a nocturnal
periodicity, i.e., they appear in large numbers at night and
retreat from the blood stream during the day.
The maximum density of Mf in blood is reported between
10 pm and 2 am.
This is a biological adaptation to the nocturnal biting habits of the
vector mosquitoes.
13. RESERVOIR OF INFECTION:
In humans the source of infection: A person with circulating Mf in
peripheral blood.
The minimum level of Mf which will permit infection of mosquitoes: A
man with 1 Mf/ 40 cu. mm of blood is infective to 2.6% of the
mosquitoes which fed on him.
In filarial disease (late obstructive stages) Mf are not found in the
blood.
14. Mode of transmission of LF:
All three infections (W. bancrofti, B. malayi and B. timori)
are transmitted to man through the bites of infective
mosquitoes.
16. Clinical manifestations of LF:
Only a small proportion of infected individuals exhibit clinical signs.
The disease manifestations can be divided into 2 distinct clinical types :
A. LYMPHATIC FILARIASIS: Caused by
the parasite in the lymphatic system:
B. OCCULT FILARIASIS:
A/K/A: Cryptic filariasis
1. Asymptomatic amicrofilaraemia
2. Asymptomatic microfilaraemia
3. Stage of acute manifestations
4. Stage of chronic obstructive
lesions
Caused by a hypersensitivity reaction to filarial
antigens derived from Mf.
Classical clinical manifestations are not present.
Mf are not found in the blood.
The best known example is: Tropical Pulmonary
Eosinophilia(TPE).
17. LYMPHATIC FILARIASIS: Stages:
1. Asymptomatic amicrofilaraemia:
Clinical manifestations of the disease: (-)
Blood for Mf: (-)
2. Asymptomatic microfilaraemia:
Asymptomatic
Blood is positive for Mf.
Important source of infection in the community.
These carriers are usually detected by night blood examination.
18. LYMPHATIC FILARIASIS: Stages: Cont..
3. Stage of acute manifestations:
In the first months and years: Recurrent episodes of acute inflammation
in lymph glands and vessels.
Fever
Lymphangitis: Inflammation of lymphatic vessels.
Lymphadenitis: Enlargement of one or more lymph nodes.
Lymphoedema of the various parts of the body.
Epididymo-orchitis in the male.
19. LYMPHATIC FILARIASIS: Stages: Cont..
4. Stage of chronic obstructive lesions:
The chronic stage usually develops 10-15 years from the onset of
the first acute attack.
This phase is due to damage, fibrosis and obstruction of lymphatic
vessels causing permanent structural changes.
Elephantiasis may affect the legs, scrotum, arms, penis, vulva and
breasts, usually in that order of decreasing frequency.
Lymphatic damage, fibrosis and obstruction: Severe swelling of the
legs, scrotum, arms, genitals , breasts.
20. Diagnosis of lymphatic filariasis:
1. Blood smear (The thick film): Capillary blood and examined for Mf
2. Membrane filter concentration (MFC) methods: Blood is collected by
venipuncture and filtering large volumes of blood.
3. DEC (Diethylcarbamazine) provocation test (100 mg DEC oral):
Mf can be induced to appear in blood in the daytime by administering DEC
100 mg orally.
Mf begin to reach their peak within 15 minutes and begin to decrease 2
hours later.
Ideal time of taking blood is: 8:30 pm- 12.00 midnight
21. Lymphoedema management:
TREATMENT FOR UNCOMPLICATED ADLA:
(ADLA: Acute dermato-lymphangioadenitis)
TREATMENT FOR SEVERE ADLA:
Analgesic (Paracetamol)
Oral Antibiotics (Amoxicillin/ erythromycin) x 8 days
Elevation of the limb and exercise.
Clean the limb with antiseptic.
Check for any wounds, cuts, abscesses and interdigital
infection (especially between the toes): Antiseptic,
Antibiotic cream.
Home management: Plenty of water, wriggling the
toes, washing the limb, cooling the limb with cold water.
Do not give antifilarial medicine.
iv Benzylpenicillin (Penicillin G) 5 million
Unit x TDS X 8 days OR
im Procain benzylpenicillin 5 million units
x BID x 8days. OR
IV erythromycin 1gm x TDS
Analgesic (Paracetamol)
Do not give any antifilarial medicine.
23. CONTROL MEASURES:
1. Chemotherapy:
Diethylcarbamazine (DEC)= 6 mg/kg body
Mass drug administration (MDA) is given single dose annually for 4-6
years.
A. Mass drug administration (Mass Deworming) to control the infection:
DEC + Albendazole. OR
Ivermectin + Albendazole
Except: Children < 2 years , Pregnant women, seriously ill patients.
B. DEC-medicated salt: 1-4 g DEC/kg of salt and duration of treatment is 6-9 months.
24.
25. CONTROL MEASURES:
2. Vector control (Mosquito Control):
A. Physical Methods:
Source Reduction (Best): Elimination of breeding place.
Use of mosquito nets
Wearing of full sleeves shirts and full pants
Use of mosquito repellent: creams, liquids, coils, mats
B. Chemical Methods:
Antiadult measures (Nerve/ Contact Poison): DDT, Pyrethrum, Malathion
Antilarval measures: Paris Green (Stomach Poison)
C. Biological Methods: Gambusia, Lebister, Poecilia (All are Larvivorous Fishes)
Gambusia
26. • The strategy to interrupt transmission of the disease calls for mass
administration of a 2-drug regimen (ivermectin or DEC plus
.albendazole) administration as a single dose annually for 4-6 years.
• The current hypothesis is that reducing the prevalence of
microfilaraemia in humans to < 1 per cent will stop transmission.
• One provisional set of guidelines for stopping treatment would
require 2 5 annual rounds of MDA with coverage of 2 65 per cent of
the total population
27. MCQ
Q. The vector for transmission of Bancroftian filaria is:
• (a) Culex fatigans
• (b) Aedes aegypti
• (c) Mansonoides annulifers
• (d) Anopheles stephensi
29. MCQ
• Q. DEC is used extensively in the chemotherapy of Filariasis.
It is most effective against:
• (a) Microfilariae
• (b) Adult worm
• (c) Infective stage larvae
• (d) All of the above
31. MCQ
• Q. The currently given regimen for Bancroftian filariasis is:
• (a) DEC – 6 mg/ Kg / day × 21 days
• (b) DEC – 6 mg/ Kg / day × 12 days
• (c) DEC – 100 mg/ day × 21 days
• (d) DEC – 100 mg/ day × 12 days
Infection is usually acquired in childhood and causes hidden damage to the lymphatic system. Social stigma: A set of negative belief: people may face discrimination and isolation due to physical manifestation
An overt infection refers to an infection that manifests with visible symptoms or clinical signs.
Inadequate sewage disposal and lack of town planning have aggravated the problem of filariasis
This is a biological adaptation to the nocturnal biting habits of the vector mosquitoes.
The mosquito cycle begins when the Mf are picked up by the vector mosquito during feeding.
Diagnosis is mainly through…. Diethylcarbamazine (DEC)=
