westermani卫氏并殖吸虫.ppt

Paragonimus These worms’ reproductive organs 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. In china, there are two species of lung flukes of medical importance: Paragonimus westermani(卫氏并殖吸虫）, Pagumogonimus skrjabini(斯氏狸殖吸虫). Paragonimus westermani This worm was first found in a tiger’s lung in India in 1877. It is the main kind of lung flukes infecting man. In our country it is prevalent in 22 provinces, city and autonomic region except Xinjiang, Xizang, Qinghai, Gansu, Ningxia, Inner Mongolia and Shandong. I. morphology 1. Adult: The body is elliptic, dorsally it is convex, ventrally it is flattened, reddish-brown in color, about 7.5-12×4-6×1-3 mm (length:width=2:1). It looks like half a peanut. The sizes of two suckers are sub-equal. The ventral sucker is located in the central position of the body. Two testes, the ovary and the uterus are situated side by side. The vitellaria is well developed. The excretory bladder extends forward to the level of pharynx. The digestive tract is divided into two ceca. .? The oval ova have an operculum and are 80-110 by 48-80 μm. It is golden yellow in color. The shell is uneven in thickness. The content is an ovum and more than 10 yolk cells. II. Life cycle 1. Infective stage: metacercaria 2. Infective mode: eating raw fresh water crabs and crayfish with metacercariae 3. Infective route: by mouth 4. Site of inhabitation: lungs 5. Intermediate hosts: 1st int. host is melania snail(川卷螺). 2nd int. hosts are crab and crayfish. 6. Reservoir hosts: carnivores such as tiger, lion, wolf, fox, dog, leopard, cat and etc 7. Life span: 5-6 years III. Pathology and Symptomatology Adults inhabit lungs, although other organs are also involved. 1. Pathological lesions may be classified into 4 stages: (1)Invading and migrating stage: After excystatio