Filaria
•
RONALD C. CABUDOY, MD, DPSP, DHPED
• wide geographic distribution
• B.malayi - endemic in Asia
• W. bancrofti has a larger
distribution – tropical areas,
worldwide
• According to World Health Organization statistics,
• 1 billion people in more than 80 countries
• More than 120 million people have been affected more
than 40 million of them are seriously incapacitated
and disfigured
• One third of the people infected with the disease live
in India,
• one third live in Africa,
• and most of the remaining affected people live in Asia,
islands in the Pacific Ocean, and the Americas.
Filaria
Wuchereria bancrofti - lymphatic
Brugia malayi
filariasis
Onchocerca volvulus – river blindness
Loa loa – eye worm
Wuchereria bancrofti
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1863 – Demarquay (hydrocele fluid)
1866 – Wucherer (chylous urine)
1872 – Lewis (peripheral blood)
1877 – Bancroft ( adult female)
1888- Sibthorpe (adult male)
1879 – Manson ( intermediate host)
The disease infects an estimated 100 million people and
its distribution is widespread,
- South America,
- Central Africa,
- Middle East,
- India
- South East Asia.
This is a disease of the lymphatic system causing a
condition known elephantiasis, in which the adult worms
cause damage to the lymphatic valve system which
causes the lymph to drain to the extremities invading
and swelling the subcutaneous tissue.
Brugia malayi
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1927 – Brug ( microflaria of another species)
1940 – Rao and Maplestone (adult male
and female)
1941- Bonne
1960 - Buckley
Brugia malayi is a filarial worm very similar in its
life cycle to W. bancrofti, except it is a zoonosis,
infecting other animals as well as humans.
With this parasite, depending on factors such as
vector species, host range, ecosystem and
geographical location the periodicity is less well
defined and is known as subperiodic. A
phenomenon also observed in some geographical
locations where W. bancrofti is found.
• Four stages of the disease are recognized.
1. The incubation period of 3 to 12 months in which there are
no symptoms.
2. The acute symptomatic stage in which some swelling of
the extremities may occur and this may be accompanied
by pain, weakness of arms and legs, headache, insomnia.
Fever is usually not present.
3. There is a period of recovery which is permanent if
reinfection does not occur.
4. If there is continued reinfection the cycle repeats and
elephantiasis may result.
Diagnosis, Treatment and Control
• The detection of microfilariae in a thick blood smear
• because of its periodic nature, several smears need to be
taken over a 24-hr period to confirm the presence of
filariasis.
• millepore filter
• intradermal skin tests using Dirofilaria immitis antigen
(drawback is that it cannot distinguish between past and
present infections)
• DEC, diethylcarbamazine is the drug of choice,
• kills the larvae and adults.
• The main draw back is there are frequently
adverse side reactions such as nausea, dizziness
and shaking.
• More recently Ivermectin has been used in trials
with promising results and fewer side effects.
• Chemotherapeutic control of filariasis has three
main objectives:
1.Reduced mortality
2.Reduced transmission by treating people with
microfilaremia
3.Interrupt transmission
Pathogenesis:
• The worms in the lymphatic system cause tissue changes
which
• restrict normal flow of lymph and result in swelling, fibrosis
and eventually secondary infections in the affected tissues.
• The lower extremities and groin are the parts most likely to
be affected. The adult worms live for several years.
Complications:
complications occurs as a result of the
lymphedema.
The most serious complication is massive infection
(cellulitis, lymphangitis).
Other complications include fibrosis (hardening) of
the affected tissue,
severe pain, gross disfigurement, sexual
dysfunction. Long term fibrosis or tissue
hardening can also cause venous thrombosis
(blood clot).
Management
1.Antibiotics to prevent secondary infections.
2.Pressure bandages to reduce swelling.
3.Surgical removal of infected tissues to improve lymph flow.
4.Chemotherapy to kill circulating microfilaria.
Diethylcarbamazine (Hetrazan)
5.Vector (intermediate host) control.
Wb
Onchocerca volvulus
• 1915 – Leukart
• 1919 - Brumpt
• 1927 – Blacklock (Simulium) IH
• Adult worms are commonly located in nodules
• Nodule may appear on any part of the body
– Region of pelvic arch
– Junction of long bones
– Temporal or occipital regions of scalp
• Adults reside typically in subcutis rather than lymphatics,
(subcutaneous tissue and eye)
• Typical lesion is onchocercoma
– Firm, round well circumscribed subcutaneous tumor.
– Composed of an outer layer of hyalinized and
vascularized fibrous tissue that encloses the adult worm
– 0.5-10cm in diameter or more
– Fully movable
Clinical Manifestations
• Skin
– Onchocercal dermatitis
• Immune and direct irritative mechanism
– Pruritus
– Altered pigmentation
Ocular Manifestations
• Depend on the duration and severity of infection
• Anatomic location of adult worm
– Sclerosing keratitis
– Anterior uveitis
– Punctate keratitis
– Iridocyclitis
– Symptoms- photophobia, gradual blurring of vision
– blindness
• Diagnosis
– Puncture of suspected tumor and discovery of microfilaria
in the aspirate
– Biopsy of small piece of epidermis
• Treatment
– Nodulectomy
– DEC and Suramin
– Antihistamine
– Corticosteroids
• Prognosis – good
• Prevention
– Vector control
– Insecticides
– Removal of nodules
Loa loa (eye worm)
• Humans acquires the infection from bite of IH (Chrysops
silacea or dimidiata)
• Forest and rubber plantation
• Adult worms normally live in subcutaneous tissue migrate
back and forth provoking temporary Inflammation (Fugitive or
calabar swelling
Causes eiosinophilia (50-70% of leukocytes)
Allergic reactions (caucasians)
Giant urticarial lesions of the skin and mucous
membrane (back, axilla, groin, breast, penis,
scalp, eyelids and bulbar conjunctiva)
Fever
Loaisis – traversing of the cornea beneath the
conjunctiva
• Other Ocular manifestations
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In Uganda
1. Conjunctival granulomata (Painless)
2. Edema of eyelids ( bung eye)
3. proptosis
• Diagnosis:
– Identification of microfilaria in peripheral smear
– Removal of adult worms from the skin of conjunctiva
Treatment:
- surgical removal
- Suramin
- DEC
Feature
Periodicity
W. bancrofti
nocturnal
B. malayi
nocturnal
Tail
tapering to delicateoften constricted
point, no terminal between 2 terminal
nuclei
nuclei
Loa loa
diurnal
tapering gradually, caudal
nuclei continuous with
those of the trunk
Appearance graceful sweepingstiff with secondary
curves
kinks
similar to malayi
Pathology
fugitive swelling of
subcutaneous tissue
regional lymphadenitis
similar to bancrofti
and lymphanditis
elephantiasis
Intermediate Culex, Anopheles Mnasonia, Anopheles Chrysops
host
Aedes,