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. It is the main kind of lung flukes infecting man
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 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. Oral sucker
spines
Excretory pouch
ventral sucker

8. Egg Size about 10055µm Thick and asymmetric shell
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. Two intermediate hosts 1st int. host is melania snail
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. Dog infected with Paragonimus westermani shows multiple worm nodules.
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

21. 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

22. Treatment and Prevention
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

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