This document provides an overview of filariasis (lymphatic filariasis). It begins with an introduction and outlines the topics to be covered, which include epidemiology, morphology, transmission, life cycle, pathogenesis, diagnosis, prevention and control. It then delves into each topic in detail. Some key points are: lymphatic filariasis is caused by infection with filarial nematodes and transmitted by mosquitoes; it affects over 120 million people globally, with highest prevalence in South and Southeast Asia and Africa; microscopic examination of blood and tissue samples can detect microfilariae and adult worms. Prevention strategies include vector control, bed nets, repellents and mass drug administration, while treatment involves antifilarial drugs

1. FILARIASIS
PRAKASH DHAKAL
Public Health Microbiology
Tribhuvan University, Nepal

2. OUTLINE OF PRESENTATION
 Introduction
 Epidemiology
 Morphology
 Mode of transmission
 Life cycle
 Pathogenesis
 Signs and symptoms
 Laboratory diagnosis
 Prevention and Control
 Pictures

3. INTRODUCTION
 Filariasis is the pathological condition caused by
infection of filarial nematodes transmitted by
different vectors.
 Infection occurs in blood vessels, lymphatic
system , connective tissues and serous cavities of
man.
 Disease of tropical warm lands.
 Caused by different worms and are characterized
by different clinical features.

4. EPIDEMIOLOGY
 Lymphatic filariasis is caused by infection with
nematodes of the family Filarioidea: 90% of
infections are caused byWuchereria bancrofti and
most of the remainder by Brugia malayi.
 Humans are the exclusive host of infection
with W. bancrofti. Although certain strains of B.
malayi can also infect some animal species
(felines and monkeys), the life cycle in these
animals generally remains epidemiologically
distinct from that in humans.
 The major vectors of W. bancrofti are mosquitoes
of the genus Culex (in urban and semi-urban
areas), Anopheles (in rural areas of Africa and
elsewhere) and Aedes(in islands of the Pacific).

5.  The parasites of B. malayi are transmitted by various
species of the genusMansonia; in some areas,
anopheline mosquitoes are responsible for
transmitting infection. Brugian parasites are confined
to areas of east and south Asia, notably India,
Indonesia, Malaysia and the Philippines.
 An estimated 120 million people in tropical and
subtropical areas of the world are infected with
lymphatic filariasis; of these, almost 25 million men
have genital disease (most commonly hydrocele) and
almost 15 million, mostly women, have lymphoedema
or elephantiasis of the leg.
 Approximately 66% of those at risk of infection live in
the South-East Asia Region and 33% in the African
Region.
 In Nepal the disease is endemic in 61 districts .The
prevalence rate is 13 % ( from 0.1 % to 40 % )

7. An example in case of Nepal :
 A Sentinel surveillance study was carried out among 7,000 (Male-
3319, Female-3681) cases and tested for microfilaraemia. The total
number of Microfilaraemia positive cases was 55, and the number
were 20, 5,10,4,5,7 and 4 in Sindhupalchok, Nawalparasi,
Rupandehi, Palpa, Tanahu, Syangja and Gorkha districts
respectively. The total number of cases having symptoms and signs
is 176 and the number were 138,0,28,4,1,5 and 0 in Sindhupalchok,
Nawalparasi, Rependehi, Palpa, Tanahu, Syangja and Gorkha
districts respectively.
 The highest microfilariae infection rate was 2.0% in Sindhupalchowk
district which is significant in number as compared to other districts
and lowest 0.40% in Palpa and Gorkha districts. The highest number
of symptomatic cases was found in Sindhupalchowk district 138
(13.8%). One significant finding was that 55 persons were found to be
microfilaraemia positive but only 41persons had symptoms of
Lymphatic Filariasis and 14 microfilaraemia positive cases did not
have symptoms and signs of filariasis.
(Source : Fiariasis Elimination Programme, World Health
Organization/Epidemiological Disease Control Division, Teku,
Kathmandu )

8. MORPHOLOGY
Wuchereria bancrofti
 Adult worm are long hair like transparent
nematodes, filariform in shape with tapering
ends.
 Male measures 2.5 to 4 cm in length by 0.1 mm
in thickness and female measures 8 to 10 cm in
length and 0.3 mm in thickness.
 Tail end of male worm is curved ventrally while
that of female worm is narrow and abruptly
pointed.

10. Brugia malayi
 The adult females of B malayi resembles to W.
bancrofti but the adult males differ .
Brugia timori
 Similar to B. malayi .
Loa loa
 The male measures 3 cm in length and 0.35 mm in
breadth . The female measures 6 cm in length by 0.5
mm in breadth.

11. MODE OF TRANSMISSION
 Transmitted by vectors
 Bancroftian filariasis is transmitted by Culex,
Aedes and Anopheles mosquito.
 Malayan filariasis is transmitted by Anopheles
and Mansonia spp.
 Loiasis is transmitted by Tabonid or horse fly of
Chrysops spp.
 When the vectors suck blood from infected
person, the microfilariae reaches the of vector ,
which then enters the thorax where by
development of larvae takes place. Infective
larvae enters the mouth parts and are shed on
the skin of healthy human host when the vectors
takes blood meal.

12. LIFE CYCLE
Life cycle of Wuchereria bancrofti

13. Life cycle of Loa loa

14. LABORATORY DIAGNOSIS
 Samples includes :
Peripheral blood , Chylous urine, Exudate of lymph
varix, Hydrocele fluid,Lymph node biopsy, skin
specimen
 Microscopic examination :
It deals with the detection of microfilariae.
 Macroscopic examination :
detection of adult worm ( lypmh node biopsy )
 Haematological examination : eosoinophilic count is
done.
 Serological test : Complement fixation test is
performed.
 Intradermal test : immediate hypersensitivity test.
Filarial antigen is injected on skin. After 30 minutes
a weal over 2 cm appears.

15. PREVENTION AND CONTROL
Prevention :
 Destruction of breeding sites of vectors.
 Using bed nets while sleeping.
 Applying repellant creams on skin.
Control
 Treatment : diethylcarbamazine against filarial
worms. Paramethyl phenyl stibonate against
infective larvae. Arsenical preparation against
adult worm.
 Correction of lymphatic defect through surgery.
 Surveillance of disease in endemic areas.

16. PICTURES

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