Paragonimus
westermani is one of the lung-fluke that parasitizes the human lungs in
many parts of the world. It causes the infection called paragonimiasis
(lung-fluke disease)
westermani is one of the lung-fluke that parasitizes the human lungs in
many parts of the world. It causes the infection called paragonimiasis
(lung-fluke disease)
Geographical distribution
P. westermani is locally
found in the Far East, Japan, China, Korea and Thailand. It is endemic in West
Africa especially in Nigeria, Zaire, the Cameroon, Congo and the Nile region of
North Africa.
found in the Far East, Japan, China, Korea and Thailand. It is endemic in West
Africa especially in Nigeria, Zaire, the Cameroon, Congo and the Nile region of
North Africa.
Morphology
The worms are flashy reddish-brown in colour almost
oval in shape (resembling one-half of a pea) and are covered with short spines.
They are hermaphrodites and measures about 1.2cm (7 – 12mm) in length 4 – 6mm
in breath and 5mm thick. Like other trematodes. It possesses an oral and
ventral sucker. Yellow in colour and measures about 90u by 50u. the eggs are
usually found in sputum and faeces, with each containing a fertilized
unsegmented ovum.
oval in shape (resembling one-half of a pea) and are covered with short spines.
They are hermaphrodites and measures about 1.2cm (7 – 12mm) in length 4 – 6mm
in breath and 5mm thick. Like other trematodes. It possesses an oral and
ventral sucker. Yellow in colour and measures about 90u by 50u. the eggs are
usually found in sputum and faeces, with each containing a fertilized
unsegmented ovum.
Life cycle
The adult
worm which mainly lives in the pocket of the lungs in pairs produce large
number of eggs which are passes out in chocolate coloured (rusty) sputum or faeces
of the patient. If passed into fresh water, the hatch in about 3 weeks at a
temperature of about 25 – 300C to release the miracidium. The
miracidum are ingested by the snail vector. Within the snail, the miracidum
develops into a sporacyst and later to two generations of radaii (i.e mother
and daughter radaii) each of which is capable of liberating 20 – 30 cercarlae
in about 78 days of being ingested by the snail. The cercariae which is
released possesses a stumpy tail and the body is covered with minute spines.
Rather than attack a new host, it swims and invades the crabs and crawfish
where they encyst and form a metacercarriae in its muscles stage of the worm
and man acquires the infection by eating and infected crab or fish (crustacean)
raw or inadequately cooked. The metacercariae is liberated in the upper part of
the small intestine (jijenum). It penetrates the intestinal wall and moves
across the peretonial cavity to enter the lungs through the diaphragm and
pleural cavity. . Once in the lungs, it attains maturity in 2 – 3 months, from
the time of ingestion.
worm which mainly lives in the pocket of the lungs in pairs produce large
number of eggs which are passes out in chocolate coloured (rusty) sputum or faeces
of the patient. If passed into fresh water, the hatch in about 3 weeks at a
temperature of about 25 – 300C to release the miracidium. The
miracidum are ingested by the snail vector. Within the snail, the miracidum
develops into a sporacyst and later to two generations of radaii (i.e mother
and daughter radaii) each of which is capable of liberating 20 – 30 cercarlae
in about 78 days of being ingested by the snail. The cercariae which is
released possesses a stumpy tail and the body is covered with minute spines.
Rather than attack a new host, it swims and invades the crabs and crawfish
where they encyst and form a metacercarriae in its muscles stage of the worm
and man acquires the infection by eating and infected crab or fish (crustacean)
raw or inadequately cooked. The metacercariae is liberated in the upper part of
the small intestine (jijenum). It penetrates the intestinal wall and moves
across the peretonial cavity to enter the lungs through the diaphragm and
pleural cavity. . Once in the lungs, it attains maturity in 2 – 3 months, from
the time of ingestion.
Mode of Transmission
Through the ingestion of flesh or juices of raw
or half cooked crab or crayfish which contains metacercariar
or half cooked crab or crayfish which contains metacercariar
Prevention and control
·
Sanitary disposal of faeces through the
provision of toilet
Sanitary disposal of faeces through the
provision of toilet
·
Avoid expectorating sputum or faeces into
sources of water supplies especially surface sources.
Avoid expectorating sputum or faeces into
sources of water supplies especially surface sources.
·
Treatment of the human reservoir of infection.
Treatment of the human reservoir of infection.
·
Health Education
Health Education
·
Use of mollescide to kill snail.
Use of mollescide to kill snail.
