Paragonimus westermani
| Paragonimus westermani | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Lungworm egg |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Paragonimus westermani | ||||||||||||
| ( Kerbert , 1878) |
Paragonimus westermani (sometimes also called lungworm ) is a suction worm that parasites humans and cancer-eating mammals . It causes pulmonary paragonimiasis in humans. It is estimated that around three million people worldwide have this condition.
distribution
Paragonimus westermani occurs in China, Taiwan, Laos, Korea, Japan, Thailand, the Philippines, Malaysia, Indonesia, India, Sri Lanka and the states of the former Soviet Union. Other species are known from Asia, Africa and Latin America. Since 2008, cases of paragonimiasis have been diagnosed in patients who have eaten raw crayfish in the state of Missouri , USA .
features
The adult parasites are fleshy, brown, and bean-shaped leeches. Their length is 8-16 mm, their width 4-8 mm and their thickness 2-6 mm. They are hermaphrodites and live in cysts of the lungs, rarely in other organs such as the brain. The genital pore lies behind the abdominal suction cup .
Life cycle
reservoir
The adult lung leeches live in the lung cysts of cats, dogs and many other carnivorous animals and produce eggs here, which are released into the open through coughing, with the sputum or after swallowing with the stool. If an egg reaches fresh water, it will develop into a miracidium in three weeks . After hatching, it penetrates a snail.
First intermediate host: snail
Usually water snails are affected as the first intermediate host, especially from the families Thiaridae , Pachychilidae, Pleuroceridae and Hydrobiidae. The development in the snail continues in several stages, called redia , until the cercariae that then emerge leave the snail and attack freshwater crabs or crabs.
Second intermediate host: freshwater crab and crab
The pathogens encapsulate themselves as metacercariae in the muscles and other organs of the shellfish .
Definitive host: Eaters of raw shellfish
Humans or other suitable ultimate hosts who eat the raw shellfish are invaded by the parasites, which, as metacercariae, have the ability to move through the wall of the duodenum into the abdominal cavity or liver. From here they penetrate through the diaphragm into the lungs and form a capsule in which they mature into adult lung fluids. Egg-laying begins after 8 to 10 weeks. The adult leeches can survive for 10 to 20 years, but mostly they die after a few years.
Harmful effect
Lung paragonimiasis manifests itself as an acute illness with fever, chills, night sweats, diarrhea, stomach and chest pain, cough and shortness of breath. The symptoms resolve spontaneously after a few weeks. The chronic phase of the disease begins after months or even years. Periodic coughing up of small amounts of blood in a tough, gelatinous sputum is considered characteristic. Fever and other general symptoms are common.
Ectopic settlements (in other organs) lead to abscesses in the abdomen and chest cavity, and if the brain is affected, epilepsy, encephalitis, meningitis, blindness and paralysis occur.
prevention
The consumption of raw or undercooked crabs or crab dishes should be avoided. Marinating and curing are definitely not reliable preventive measures.
See also : Parasites of humans
literature
- J. Dönges: Parasitology. With special consideration of human pathogenic forms . Thieme, Stuttgart 1988.
- H. Mehlhorn, G. Piekarski: Outline of parasite science . 6th edition. Heidelberg 2002.
