FILARIAL Worms - Y2S2 Rumala.PPT

7/23/2019 FILARIAL Worms - Y2S2 Rumala.PPT

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Filarial Worms

Rumala Morel

Dept. of ParasitologyPeradeniya

Y2S2


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Teaching Learning Objectives:

Name the major tissue nematodes of humans indicating their

location in the human body.

List the major characteristics of the filarial parasites of

humans indicating those found in Sri Lanka

Name the vectors of those parasites found in Sri Lanka

Outline the life cycle of a typical filarial parasite

Describe the life cycle ofWuchereria bancrofti

Describe the phenomenon Periodicity of microfilaria

State the stages that cause pathogenic effects

Identify stages of diagnostic importance

Outline laboratory methods of visualization/identification of

parasites/products

Identify points in the life cycle where preventive measures

are applicable


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FILARIAL WORMS: Filariasis

tissue nematodes

adults thread like;

female embryos (early first stage larvae)microfilariae (mf)

transmitted by insect vectors adults in different habitats in body

mf in blood/ subcutaneous tissue


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Human filarial parasites grouped according to

HABITAT of the ADULT WORM in man

Lymphatic filariae

Subcutaneous filariae

filarial infections of the body cavities& associated tissue


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LIFE CYCLE

MAN

2 moults Adults

mfin blood /subcutaneous tissueINSECT VECTOR2-moults

NO multiplication

Infective larva-L3


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Microfilaria- periodicity

In some species mf in peripheral blood only

during certain times during 24 h period.

Non periodic

Periodic - nocturnally

- diurnally

Sub periodic- mf present at all timesbut peak nocturnally or during daytime


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Periodicity of microfilaria

physiological adaptation to biting habits of vector

Mf bldpatency

6h 12h 24h 2h 6h

Nocturnally

periodic

Non

periodic

Diurnally

periodic

Sub periodic


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LYMPHATIC FILARIAEmosquito borne

adults in lymphatics / mf in blood

Wucherer ia bancro ft i-widespread tropics

Brug ia malayi- SE Asia, India

Brugia t imor i- Timor island,other islands nearby


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Lymphoedema


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Distribution of lymphatic filariae

Sub periodic W. b


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Dog filarial worm

Dirof i lar ia repens- zoonosis in Sri Lanka

Filarial infections of Man in Sri Lanka

Bancroftianfilariasis- W banc rof t i

(nocturnally periodic)


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Wucherer ia bancro f t i(nocturnally periodic)

High prevalence in hot,humid, tropics.

associated with poor urbanization

Vector-common urban mosquito

Culex qu inquefasc iatus

In E Africa- vector rural-Anopheles gambiaePacific islands- diurnally sub periodic

vector day biting -Aedes spp


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life span 7-16 yrs


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Larva developing in the

mosquito thoracic muscle


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Infective larvae L3 emerging from proboscis

of mosquito


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Adults of

Wuchereria bancrofti

are long and threadlike.MALES (left) measure

up to 40 mm long

and FEMALES (right)

are 80-100 mm long.


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tail nuclei

Wucherer ia bancro f t i-mf Brugia malayi

300 x10 m 260 m

Lie- graceful curves kinked (acute angles)

head space- short long

nuclei- countable, overlapping,tail nuclei+

head space


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Laboratory Diagnosis of Filariasis:

Direct Detection of mf in bloodThick film- 10pm-2 am (20-60l)

wet mount/ stain Giemsa

Concentration-

Knotts method-1ml blood +2% formalin, centrifuge,

examine deposit for mf

Membrane filtration- pore size 5m

Detection of adults in biopsy- rare

Detection of Filarial Specific Ab

Detection of Circulating Filarial Ag.

Indirect


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A). Detection of filarial antibodies in serum

Indirect immunofluorescent test- IFA/FATAntigen used - microfilariae ofW bancrofti

sections of adult worms (cattle filariae)

ELISA (enzyme linked immunosorbent assay)

Disadvantage: Ab long lasting

B). Detection of Circulating Filarial AgAntigen detection ELISA

Immunochromatographic [ICT] Card Test

INDIRECT TESTS


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Antigen detection strip (card) tests- RDTs

Sample origin

(whole blood

serum/plasma)

polyclonal Ab

+ colloidal gold

Mab

W banc rof t i

T C

absorbent pad

test control

RDT = Rapid Detection Tests

Immunochromatographic Card Test=


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ImmunochromatographicCard Test

Ag detectionELISA plate


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ICT card test

Immunochromatographic card test-

detects specific circulating W bancroftiAgin serum/whole bloodusing monoclonalAb IgG4

simple, no equipment required quick results Rs. 1600/test


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Filariasis in Sri Lanka-

1937-39: Brug ia malayipredominant

1947: Anti Filariasis Campaign

1960s: Brugian filariasis eradicated

control of larval breeding

residual action of DDT on adults

treatment with DEC

Bancroftian filariasis is the ONLY

lymphatic filariasis in SL now

C fi


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LF is endemic

in eight of the

25 districts.

Confined to

urbanized

coastal belt:9.5 million

(50%)

populationexposed

inland foci:

Gampaha,

Warakapola

Veyangoda


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Global Elimination of Lymphatic

Filariasis

Global Programme to Eliminate Lymphatic Filariasis -WHO 1998

Global Alliance to Eliminate Lymphatic Filariasis - 2000

public-private partnership WHO, national Ministries of Health,

Private drug companies donating albendazole &ivermectin (Mectizan)

NGOs 1 billion at risk population

> 120 million people are already infected

> 40 million incapacitated or disfigured

B fti fil i i t l i S i L k


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Bancroftian filariasis control in Sri Lanka

vector control:

prevent mosquito breeding

clear drains, cess pits, sealing of septic tanks

larviciding with insecticides, larvivorous fish

Selective treatment of mf + caseswith 2-week DEC (6 mg/kg)

Mass chemotherapy- eradication of parasite by

killing mf and disrupting transmission- continued for4-5 years

Morbidity controlclinics disability management

training

C l i f i t b di it


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Culex quinquefasciatusbreeding sitesDirty water in blocked drains, cess pits etc.


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Brug ia malayi -Confined to Asia

Not detected in Sri Lanka since 1962

a

du

Adults in lymphatics of lower limbs, groin. Rare in genitalia.Mf sheathed, characteristic morphology

Pre patent period- 1-3 months

Sub periodic form

- SE Asia-zoonoses

(monkeys,dogs & cats)

B malayi- nocturnally periodic

Vector:Mansonia species

Female mosquito ofMansoniaspp

lays eggs on the under surface of

leaves of water plants

eg. Pistia, Salvinia, Eichonia


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Subcutaneous filariasis of humansdifferent fly vectors

mf in blood / subcutaneous tissuebiting habits of vector

Onchocerca vo lvulus-Onchocerciasis

Major public health problem - tropical Africavector- black flies, mf subcutaneous

Loa loa- Tabanids, mf in blood

Body cavities:

Mansonella spp- culicoides, mf in blood

Di f i l i Di fil i i


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Dirof i lar ia repens -Dirofilariasis

Zoonotic filariasis in Sri Lanka

a common subcutaneous filarial infection of dogs in

Sri Lanka

Transmitted by several species of mosquitoes

Aedes, Armigeres & Mansonia spp.

Human disease common

Causes subcutaneous nodules

due to granulomatous reaction

to adult worm

but

not known to

produce microfilariae

in humans

D.repens adult

100 200


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Cross-sections ofDirofilaria sp. from a subcutaneous nodule

stained with hematoxylin and eosin (H&E).

100x 200x

O h i i Ri Bli d


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Onchocerciasis = River Blindness

Simulium (black fly

fast flowing riversRiver Volta-W Africa


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mffcauses eye lesions:

blindness

In skin: itching, depigmentationloss of elasticity

Adults cause subcutaneous nodules

Loa loa loasis


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Loa loa- loasisAdults in subcutaneous tissue

Mf in blood- diurnally periodic

transmitted by blood sucking day-biting fliesVectors: Tabanid flies

Confined to Tropical Africa where vectors arefound

Mf in blood

Adult worm under

the conjunctiva- 10 mmTransient swellings-days


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Tabanid fly

adult worm under

the conjunctiva


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Filarial worms

-Wucherar ia bancro f t i[SRI LANKA]

Brugia malayi

Subcutaneous filariae- Onchocerca volvulus [River blindness]

- Loa loa

- Dirofilaria repens [ZOONOSIS in SRI LANKA] filarial infections of the body cavities

& associated tissue

Lymphatic filariae

FILARIAL Worms - Y2S2 Rumala.PPT

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