Filariasis - Lymphatic Filariasis (Elephantiasis)
Lymphatic filariasis parasitic disease, considered as a neglected tropical disease (NTD), caused by microscopic, thread-like filarial worms.
Filariasis
is tropical,
parasitic disease that affects the lymph nodes and lymph vessels of human.
Lymphatic filariasis is caused by
parasites classified as nematodes (roundworms) of the family Filariodidea.
The two species of worms most
often associated with infection are; Wuchereria bancrofti and Brugia
malayi. Wuchereria bancrofti, which is responsible for infection 90% of
the cases.
Lymphatic filariasis is spread by infected mosquitoes to human. Their bites deposit a parasite that travels to the lymph system of body and adult worms only live in the lymph nodes and lymph vessels (human lymph system). Lymphatic filariasis is spread from person to person by bite of mosquitoes.
Epidemiological Triad
Agent – The
causative agent of filariasis is microfilariae of wuchereria bancrofti (W.
bancrofti) and Brugia malayi (B. Malayi) in india.
Lymphatic filariasis is
a vector-borne disease, being transmitted by infected mosquitoes (e.g.
Culex quinquefasciatus, Anopheles and Aedes mosquitoes)and several black fly
species. The main vector is Culex quinquefasciatus in india.
Host factor- All ages is susceptible, but infection rate is
more with age of 20-30 years. Human is the (definitive
host) and mosquito is the (intermediate host).
Environmental factors- Bad drainage or ill
maintained drainage, Inadequate sewage disposal, Septic tanks, Open
ditches drainage, Breeding place such as cess pools, soakage -
pits, Poor environmental sanitation.
Causes of Filariasis
Filariasis is a tropical infectious disease caused by the round
worm parasites (nematode); Wuchereria bancrofti or Brugia malayi.
The infection spreads from human to human by
infected mosquito bites. The adult worm lives in the human lymph node and lymph
vessels and produces a number of microscopic worms, known as microfilariae.
Microfilariae circulate in the human blood and infect the mosquito when bites a
human who is infected.
Mode of Transmission
Culex mosqitos or Mansonia mosquito pick up the
microfilaria of Wuchereria Bancrofti, Brugia malayi when bites an
infected person.
Microfilariae (the
minute larva of a filaria ) grow and develop in body of
mosquito vector. When bites a healthy person, the larval worms pass
from the mosquito into the human skin, and circulating to the lymph
vessels.
Filariasis disease spreads
from man to man by mosquito bites. When a mosquito bites a person who infected
with lymphatic filariasis, microscopic worms circulating in the
person's blood enter and infect the mosquito.
1. Man To mosquito
To man
2. Infected man bitten
by Culex mosquito
3.
Mosquito infects man
Lymphatic filariasis
disease, is a vector-borne disease and being transmitted by
mosquitoes (e.g. Culex, Anopheles and Aedes mosquitoes).
Incubation Period
The incubation period is can be vary, short
as about 4 weeks or as long as about 8-16 months.
Life Cycle
1. When a mosquito bites to a man who has
lymphatic filariasis.
2. Microfilariae grow and
develop mature into infective larvae within the mosquito.
3. When infected mosquitoes
bite to man, mature parasite larvae are deposited on the skin from where they
can enter the body.
4. The larvae then circulate to the lymphatic
vessels where they develop into adult worms.
5. The larvae matures in a six to twelve
months period into the adult filariae which can live up to fifteen
years and producing microfilariae.
6. The adult worms release millions of
microfilariae into the blood of people. People with microfilariae in their
blood can be the source of infection to others, thus continuing a cycle
of transmission.
1. Culex mosquitos
2. Infected a person having microfilariae in
peripheral blood
3. microfilariae are picked up by mosquito by
bite
4. Mosquito bites to healthy human
5. After an incubation period
6. Cause filaria in the human host
Pathophysiology of Filariasis
The pathogenic effect are
produced by adult worm (living/dead) of parasite -
1. The larval form of the
parasite transmits the disease to humans by the bite of a mosquito
2. Larvae then enters the
patient's blood through the skin wound
3. Spread to the
different sites such as lymphatic vessels
Affected lymph node and lymph
vessel
4. Cause obstruction and
Dilation of Lymphatic vessels, cause granulomatous lesions
5. Infections of lymphatics (Lymphangitis)
6. Obstruction of the lymph nodes, obstruction of the lymph flow
7. Chronic inflammation may
lead to hardening of the lymphatic vessels (fibrosis)
8. Swell especially the legs and external genitals
9. Lymphoedema pitting (Grade
1)
10. Lymphoedema non- pitting
(Grade 2)
11. Elephantiasis (Grade 3)
Clinical Manifestation
In the early stages of the
infection, the patient clinical manifestation are -
1. High Fever
2. Shaking chills
3. Body aches
4. Headaches
5. Skin lesions
6. Swollen lymph nodes
7. Hypersensitivity reactions
Chronic Conditions
1. Lymphadenitis - Enlargement one or more lymph node
2. Swelling in
the legs, arms and genitalia especially, legs and external genitals
3. Lymphangitis is an
inflammation of the lymphatic system
4. Lymphoedema - localized
swelling of the body caused by an abnormal accumulation of lymph
Attacks may also be
associated by acute inflammation of the genitalia in males -
1. Inflammation, pain and
swelling of the testes (orchitis)
2. Sperm track
(funiculitis)
3. Sperm ducts
(epididymitis)
4. Scrotum may
become abnormally swollen and painful
5. Epididymo-orchitis
- Inflammation of tube that carries and stores sperm, and/or of the testicle
When fibrosis and obstruction of lymphatic
vessels occur due to chronic stage, which develop after 10-15 years after acute
attack, in such cases, clinical manifestation are-
1. Hydrocele- accumulation
of fluid in the scrotum
2. Elephantiasis - enlargement of an area of the body, enlarged due to obstruction of the lymphatic vessels, causing accumulation of fluid, arms and legs are the areas most often affected.
3. Chyluria - presence
of lymphatic fluid in the urine
4. Abnormally enlarged
lymphatic vessels (varices)
Progressive edema (elephantiasis)
can affect in Female -
Female external genitalia;
(vulva), breasts, and/or arms and legs. Chronic edema may result abnormally
thick skin.
Types of Filaria Infection
1. Lymphatic filariasis
A. Asymptomatic microfilaremia - patients remain asymptomatic for months and/or for years.
B. symptomatic filariasis - presents with the symptoms
a. Acute manifestation
b. Chronic manifestation (lesion
manifestation)
2. Occult filariasis
Associated characteristic
histological changes. such as Hypersensitivity reaction
Diagnostic Evaluation
Filariasis is diagnosed in
microfilaraemic cases primarily through direct observation of microfilariae in
the peripheral blood.
Microfilariae cause
lymphatic filariasis that circulate in the blood at night
(called nocturnal periodicity).
1. Thick blood film
2. Serological tests – detect antobodies to
microfilariae
ELISA - Enzyme-linked immunoassay
IFAT - Immuno - Fluorescence Antibody Test
CFT - Complement fixation test
IHAT - Indirect hemagglutination
test
Now a days, antigen are detected in blood
or urine
3. DEC (diethyl- carbamazine) provation
test – detect microfilariae in day time
4. Filariasis Antigen Test
Urine examination- urine sample of chyluria
5. Lymph node sample from an infected individual.
6. PCR
Treatment of Filariasis
Currently there is no vaccine available to
prevent cure for lymphatic filariasis infection in human.
Antiparasitic drugs may be
effective in eliminating the worm. If the disease is left untreated,
obstruction of the lymph flow will cause swell to particular areas of the body
especially the legs and external genitals. Symptoms are primarily a response to
adult worms that cause inflammation and obstruction of the lymph flow.
Drugs Treatment of Filariasis
Di-Ethyl- Carbamazine (DEC) . This medication
causes the disappearance of microfilariae from circulation and is effective in
killing microfilariae.
More drugs are: Ivermectin, Albendazole, and
Diethylcarbamazine. These drugs get from rid of the larval worm, to inhibit
reproduction of the adult worm, or to kill the adult worm.
Surgical Treatment of Filariasis
Surgery may be performed to
treat some people with filariasis who develop an abnormal accumulation of fluid
in the scrotum (hydrocele).
Note - DEC should not be administered to patients who may also
have onchocerciasis (river
blindness) as DEC can
worsen onchocercal eye disease.
In patients with loiasis (related to Loa loa microfilarial
density; skin
and eye disease), DEC can cause serious
adverse reactions, including encephalopathy.
Drug of choice -
Where onchoceriasis is present, Ivermectin is the drug of choice to treat
lymphatic filariasis.
Prevention and Control
In the tropical areas, mosquito
control is an important part of prevention of filariasis.
The best way to prevent
lymphatic filariasis is to
1. Identification of cases and carriers
a. Clinical parameters- Incidence and
prevalence rate
b. Parasitological parameters – Measures
microfilarial rate
2. Control of mosquito
a. Anti-larval measures
b. Anti-adult measures
3. Personal protection- Prevent from mosquito bites
4. Environmental sanitation
Know the signs and symptoms
of Malaria, caused by Plasmodium
parasites, transmitted to human through the bites of infected female Anopheles
mosquitoes.
0 Comments