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Paragonimus westermani 卫氏并殖吸虫

Paragonimus westermani 卫氏并殖吸虫. (lung fluke, 肺吸虫 ). Introduction. The reproductive organs of paragonimus stand side by side Adult worms usually live in the lungs of man and carnivores causing paragonimiasis ， so they are also called lung flukes

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Paragonimus westermani 卫氏并殖吸虫

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  1. Paragonimus westermani卫氏并殖吸虫 (lung fluke,肺吸虫)

  2. Introduction • The reproductive organs of paragonimus stand side by side • Adult worms usually live in the lungs of man and carnivores causing paragonimiasis，so they are also called lung flukes • It is essentially a zoonosis, reservoir hosts including dogs, cats and tigers • In china, there are two species of lung flukes of medical importance: Paragonimus westermani, Pagumogonimus skrjabini

  3. Introduction • Paragonimus westermani was first found in a Bengal tiger’s lung in India in 1877 • It is the main kind of lung flukes infecting man • In China, P. westermani prevalent in 23 provinces, city and autonomic region except Xinjiang, Xizang, Qinghai, Gansu, Ningxia, Inner Mongolia and Shandong

  4. Introduction Infection occurs in Asia (especially in China, Korea, India, Japan, Laos, Philippines, Sri Lanka, Thailand, Viet-Nam), Central-West Africa, South America (Ecuador, Perù, Venezuela)

  5. Morphology Adult worm • Elliptic, dorsally convex while ventrally flattened as half of a peanut • Reddish-brown in color • About 7.5-124-61-3 mm (length:width=2:1) • The ventral sucker is located in the central position of the body • Two testes, the ovary and the uterus are situated side by side – characteristic configuration

  6. Oral sucker ventral sucker ceca ovary uterus Vitelline follicles Testes

  7. Oralsucker spines Excretory pouch ventralsucker

  8. Egg Morphology • Size about 10055µm • Thick and asymmetric shell • A distinct operculum • An ovum surrounded by more than 10 yolk cells operculum ovum yolk cell shell

  9. Morphology

  10. Life cycle

  11. Life cycle • Infective stage: metacercaria • Infective route: oral consumption (eating raw fresh water crabs and crayfish with metacercariae) • Development in definitive hosts including pre-adult migration • Site of inhabitation: lungs

  12. Life cycle • Two intermediate hosts • 1st int. host is melania snail • 2nd int. hosts are crab and crayfish • Ectopic parasitism caused by worm wandering – cerebral, abdominal, etc • Eggs discharged with sputum or feces • Reservoir hosts: carnivores such as tiger, wolf, fox, dog, leopard, cat, etc

  13. 1st int. host cercaria

  14. Life cycle 2nd int. host Crab (Eriocheir sinensis) Crayfish

  15. Pathogenesis • Stages take responsibility -- adult and pre-adult worms (migration and lodging) • Pathology including cell infiltration  granuloma formation  encapsulation (lung: duct to bronchiole) abscess stage cystic stage scar formation

  16. Pathogenesis Dog infected with Paragonimus westermani shows multiple worm nodules.

  17. Pathogenesis Dog infected with Paragonimus westermani shows worm nodules and an opening from which an adult worm escaped.

  18. Pathogenesis A computerized tomography shows multiple calcified density in the right frontal and temporal areas of chronic cerebral paragonimiasis patient.

  19. Clinical features • Paragonimiasis may be classified into 4 types • Pulmonary type: the symptoms resemble pulmonary tuberculosis with low fever, loss of appetite, night sweating, chest pain, loss of weight and rusty sputum • Abdominal type: abdominal pain，diarrhea or dysentery with blood and mucus • Subcutaneous type: the wandering and painless subcutaneous nodules • Brain type: epilepsy, hemiplegia, aphasia

  20. Diagnosis • History of eating raw crustaceans (crabs or crayfish) • Etiological diagnosis – finding eggs in sputum and feces • Sputum examination: • Direct sputum smear • Alkali digestive method (10%NaOH) • Stool examination: • Direct fecal smear • Alkali digestion • Water sedimentation method • Biopsy for Subcutaneous type • CT for brain type • Immunological tests for reference

  21. Treatment and Prevention • Treatment: • praziquantel • Prevention: • Treat patients and carriers • Avoid eating raw fresh water crabs and crayfish • Avoid sputum and stool getting into water • Control of reservoir hosts

  22. Pagumogonimus skrjabini • A unique species only endemic in China, about 15 provinces reported cases • Pathology mainly caused by the wandering pre-adult worm • Subcutaneoustype is the most common clinical features • Diagnosis through skin biopsy • Praziquantel is the choice for treatment

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