Download - Lymphatic Filari
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Infection - 3 closely related Nematodes
◦ Wuchereria bancrofti
◦ Brugia malayi
◦ Brugia timori
* Transmitted by the bite of infected mosquito responsible for
considerable sufferings/deformity and disability
* All the parasites have similar life cycle in man
* Adults seen in Lymphatic vessels
* Offsprings seen in peripheral blood during night
Lymphatic Filariasis
Filarial worms
◦ Tissue dwelling parasites
Possess a unique life cycle stage – the microfilaria - between the
egg and J1
Egg microfilaria J1 J2 J3 J4 Adult
these are present in the bloodstream or skin of the definitive host.
Filarial worms utilize arthropods as vectors
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Epidemiology
95% cases due to Wuchereria bancrofti, other species include
Brugia malayi and Brugia timori
120m people infected in >80 countries in Africa, Asia, the Pacific
islands and South and Central America
40m of those infected are disfigured or severely incapacitated
W. bancrofti usually resides in deeper lymphatic system besides
in lower lymphatic system, with no natural or reservoir host
B.malayi usually resides in lower lymphatic system of limb,
can be transmitted to cats and rhesus monkeys
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• W. bancrofti- broad equatorial belt particularly
Africa, Middle East, Southeast Asia, Indo-Pacific islands, Parts of
Australia and South America
• Brugia malayi - Orient, South Pacific, and Southern Asia to India –
overlaps with W. bancrofti - but does not occur in Africa or South America
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Man – Natural Host
Age – All age (6 months) Max: 20-30 years
Sex – Higher in men
Migration – leading to extension of infection to non-endemic
areas
Immunity – may develop after long year of exposure (Basis of
immunity-not known)
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Associated with Urbanization, Poverty, Industrialization,
Illiteracy and Poor sanitation.
Climate: is an important factor which influences:
1. The breeding of mosquito
2. Longevity (Optimum temperature 20-300C & Humidity
70%)
3. The development of parasite in the vector
4. Sanitation, Town planning, Sewage & Drainage.
Adults:
Thread-like, smooth cuticle, filariform oesophagus.
Female: 10 cm x 0.2 mm. (2 sets of genitalia, vulva 1mm from
anterior end)
Male: 4 cm x 0.1 mm. (one set of genitalia, posterior end curved
with2 spicules)
Takes 6-12 months for females to
release microfilariae
Produce for 5-10 years
♀
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Micrifilariae:
Embryos laid by the female
250 X 8µm, with graceful curves with
rounded anterior & posterior ends
Have loose redundant sheath
No alimentary canal
The body contains columns of nuclei
The tail is free of nuclei
Life span about 2~3 months
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Vector:
Wuchereria bancrofti is mainly
transmitted by
◦ Culex in India, Anopheline &
Aedes mosquitoes in Africa
B. malayi and B. timori are
transmitted mainly by Mansonia and
Anopheles
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Anopheles
Aedes
Culex
Mansonia
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W. bancrofti -10 PM to 2 AM
B. malayi - 8 PM to 4 AM
Theories:
Adaptation between biting & microfilariae
+ve chemotaxis between mosquito
saliva & microfilariae
↑ CO2 in blood stimulates microfilariae
to migrate to peripheral blood
Khalil’s theory: Blockage theory
Nocturnal periodicity of microfilariae
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Pathology
• Adult worms live in the afferent lymphatic vessels and cause
severe disruption to the lymphatic system
• Scrotal damage and massive swelling may occur when adult
Wuchereria bancrofti lodge in the lymphatics of the spermatic
cord
• Late stage disease is typified by elephantiasis – painful and
disfiguring swelling of the limbs
• Trauma and secondary bacterial infection of affected tissues is
common
• Incubation period: 1 year.
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Manifestations are 2 types
1. Lymphatic Filariasis (Presence of Adult worms)
2. Occult Filariasis (Immuno hyper responsiveness)
None Asymptomatic
microfilaremia Filarial
fever
Chronic
pathology TPE
Clinical Spectrum
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There are 4 stages :
1. Asymptomatic amicrofilariaemic stage
2. Asymptomatic microfilariaemic stage
3. Stage of Acute manifestation
4. Stage of Obstructive (Chronic) lesions
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In endemic areas, a proportion of population does not show mf
or clinical manifestation even though they have some degree
of exposure to infective larva similar to those who become
infected.
◦ Laboratory diagnostic techniques are not able to determine whether they
are infected or free.
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Considerable proportions are asymptomatic for months and
years
◦ they have circulating microfilariae
◦ important source of infection
◦ can be detected by Night Blood Survey and other suitable
procedures
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During initial months and years, there are recurrent episodes of
Acute inflammation in the lymph vessel/node of the limb &
scrotum that are related to bacterial & fungal super infections of
the tissue that are already compromised lymphatic function.
Clinical manifestations are consisting of:
1. Filarial fever
2. Lymphangitis
3. Lymphadinitis
4. Epididimo orchitis
Occult or Cryptic filariasis, in classical clinical manifestation
mf will be absent. Occult filariasis is believed to be the result
of hyper responsiveness to filarial antigens derived from mf.
Seen more in males.
◦ Patients present with paroxysmal cough and wheezing, low grade fever,
scanty sputum with occasional haemoptysis, adenopathy and increased
eosinophilia.
◦ X-ray shows diffused nodular mottling and interstial thickening
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Lymphoedema is classified into 7 stages on the basis of the presence
& absence of the following:
1. Oedema
2. Folds
3. Knobs
4. Mossy foot
5. Disability
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Swelling reverses at night
Skin folds-Absent
Appearance of Skin-Smooth,
Normal
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Swelling not reversible at
night
Skin folds-Absent
Appearance of skin-
Smooth, Normal
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Swelling not reversible at
night
Skin folds-Shallow
Appearance of skin-
Smooth, Normal
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Swelling not reversible at night
Skin folds-Shallow
Appearance of skin
- Irregular,
* Knobs, Nodules
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Swelling not reversible at
night
Skin folds-Deep
Appearance of skin –
Smooth or Irregular
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Swelling not reversible
at night
Skin folds-Absent,
Shallow, Deep
Appearance of skin
*Wart-like lesions on
foot or top of the toes
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Swelling not reversible at night
Skin folds-Deep
Appearance of skin-Irregular
Needs help for daily activities -
Walking, bathing, using
bathrooms, dependent on
family or health care systems
b) Chronic phase:
Hydrocele:
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Obstruction of lymphatics:
Distension & varicosities of l.v.
distal to obstruction.
Lymphatic edema.
Rupture of distended lymphatics.
Elephantiasis.
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Obstructive phase photos
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Clinical.
Microscopy
◦ Microfilariae in Giemsa stained thick blood films
Knott’s technique
◦ Microfilariae in chylous urine or hydrocele
Adults in lymph nodes
High eosinophilia
Serology - ICT
DEC Provocative test
Molecular techniques
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Imaging techniques:
1-Ultrasonography
2- Lymphoscintography
Calcification of inguinal lymph nodes
Obstruction of Cisterna
chyli or its tributeries
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Diethyl carbamazine (DEC): 6 mg/kg/day/12 days
(affects adults & mf). Repeated /6 months: till no mfmia.
Antihistaminics & corticosteroids.
Ivermectin: 150µg/kg body weight (Single oral dose).
Repeated /6 or 12 months (affects mf)
• Other treatment options are
– ivermectin
– combination of DEC and albendazole
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• Diethylcarbamazine (DEC) rapidly kills microfilariae and will
kill adult worms if given in full dosage over 3 weeks
• Release of antigens from dying microfilaria causes allergic-type
reactions – add an antihistamine and aspirin to treatment
regimen
Symptomatic treatment.
Surgical management.
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Prevention and control
• Rapid diagnosis and treatment of infected individuals
• Mass drug administration to at risk communities
• Vector control:
• eliminate mosquito breeding sites through improved
sanitation and enviromental management
• Personal protection against mosquito bites by
• insecticides,
• Bed nets and
• repellants
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Heartworms (Dirofilaria immitis)
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Unsheathed
microfilaria in dog
blood -
DIAGNOSTIC
Adult male:
6-12 inches
long
Adult female:
12-16 inches
long
Adults coiled
in right side of
dog heart
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HUMAN INFECTIONS of Dirofilaria immitis are rare (~70 cases).
Larvae are killed by the host reaction and scar tissue nodules
form in lungs around worms
• Symptoms are coughing and chest pain.
In only 4 cases were adult worms recovered from the human heart.
These were found incidentally at autopsy and were not related to
the death of the patient.
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