Paragonimus westermani is ordinarily known as lung fluke is native to Asia and South America. It was first isolated from two tigers that died in the zoo in Europe in 1878. It was isolated from humans after many years in Formosa. The sycophant is known to cause a food-borne infection known as Paragonimiasis which causes a sub-acute inflammatory disease of lung. It has a wide geographical distribution. More than 30 species of trematodes belonging to the genus Paragonimus are known to infect both humans and animals. Out of these 10 are known to infect humans and this species is also known as oriental lung fluke.
The sycophant resembles a coffee bean in its shape, size and body colouration when alive. Adult worms are 7.5 mm to 12 mm long and 4 mm to 6 mm wide. The skin or tegument of the worm is armed with scale like spines. The oral and ventral suckers are similar in size. Excretory bladder arises from the posterior end of the pharynx. The testes are lobed and are placed adjacent to each other at the posterior end. The ovaries are also lobed and are placed at the centre of the body of the worm. The uterus is placed next to acetabulum which is associated to vas deferens. The vitelline glands produce yolk for the eggs and are placed from pharynx towards the posterior end of the body.
Fluke
The eggs of the sycophant portion 80 to 120 µm in distance by 45 to 70 µm width. They are ovoid or elongate, yellow coloured with thick shell and are asymmetrical with one end slightly flat. At the large end operculum is in fact descriptive and the opposite end is somewhat thickened. They are unembryonted when passed straight through sputum or faeces. The cercariae are used for difference in the middle of separate species. They have a large posterior sucker and the covering of the body is armed with spines. Metacercariae are regularly encysted in the tissue and they also bear two suckers with outer portion of the body bearing spines. The adults are reddish-brown in colour with well advanced suckers and are hermaphroditic.
The adult fluke was discovered in man by Ringer in 1879 and the eggs were isolated from the sputum by Manson and Erwin von Baelz in 1880. The names of the species are given after the name of Mr. P. Westermani a zookeeper who noted the sycophant in Bengal tiger in an Amsterdam Zoo. Unembryonated eggs pass out whether straight through faeces or sputum of man or any feline animal. After two weeks the eggs hatch into miracidia. This enters into the body of the first intermediate host which is a snail of the genus Melania. Within the snail mother sporocyst is formed which produces mother rediae which produces daughter rediae. Ultimately crawling cercariae are released in the surrounding water. They then enter the body of a fresh water crab and encyst in the muscles to become metaceracariae. When consumed raw or improperly cooked by man or feline animals the metacercariae becomes adult after reaching the lungs.
Reservoir hosts of the sycophant are some carnivores for example felids, canids, viverrids, mustelids, some rodents and pigs. Humans get infection after eating raw or improperly cooked crab's meat containing encysted metacercariae. The incubation period of the infection may range from 65-90 days. The infection may lasts for about 20 years in humans. Once in the lung the sycophant stimulates an inflammatory response and covers itself in the granulation tissue forming a capsule. The capsules if enter into spinal cord may cause paralysis and if enter heart may lead to death.
The symptoms are localized in the pulmonary law and are characterized by bad cough, bronchitis, and blood in sputum. The eggs can be isolated by the little test of sputum. They can be identified only after 2-3 months of entry of the worm. Eggs can be recovered from biopsy. Praziquantel and Biothionol are the promising drugs. Arresting of infection includes sanitary food preparing by encouraging safer cooking techniques and more sanitary handling of potentially contaminated seafood. Elimination of snail host is also very important.
Paragonimus Westermanii: Oriental Lung Fluke