The disease is the clinical manifestation of the infection which shows the active pre and replication of the parasite causing damage in the host. It may be mild, severe, fulminant(W tE J ), and in some cases may even cause death of the host The person who is infected with the parasite but without any clinical or sub clinical disea is referred to as a carrier PARASITIC ZOONOSES(人兽共患病) These are the infections which are naturally transmitted between the vertebrate animals and man. The condition usually includes those infections in which the proof of strong circumstantial evidence of transmission between the man and animals are documented PATHOGENESIS AND PATHOLOGY(发病机制与病理学 Pathogenesis(发病机制) of the parasitic diseases is a dynamic process and depends on the complex interaction of a variety of host and parasitic factors Host factors The host factor include 1) Nutritional status of the host, whether malnutrition or under nutrition 2) Immune response to parasitic infection 3) Immune status of the host whether there is immuno-suppression or not 4)The presence or absence of the co-existing disease or other physiological conditions such as pregnancy, 5) The age and level of the immunity at the time of infection Parasitic factors The parasitic factors include 1) Site of the attachment of the parasite and the size of the parasite. 2) Number of invading parasites, and 3)Parasite strain(pathogenic or non-pathogenic) and the growth, development and multiplication of parasites inside the human body and their metabolic products The parasites can cause disease in man in various ways as follows: trauma by adult worm larva, and egg(e. g, hookworm cause oozing of the blood at the site of attachment); Invasion and destruction of host cell( Plasmodium and Toxoplasma are obligate intracellular parasites of man they produce several enzymes which cause digestion and necrosis of host cells); Inflammatory reaction(many of the parasite induce inflammatory reactions in the host leading to the formation of various pathological lesions); Toxin( parasites like bacteria also produce toxins but they appear to have a minimal role in the pathogenesis of the disease processes; Allergic manifestation( many of the metabolic and excretory products of the parasites absorbed in the circulation, produce a variety of immunological and allergic manifestations in the sensitized hosts). Various pathogenic mechanisms in parasitic diseases are summarized in the below table I-1-2 The parasitic infections usually are designate by generic names of the parasites en asis or-osis.(e.g, Schistosoma infection is called as schistosomiasis) Table 1-1-2 Pathogenic Mechanisms in Parasitic Diseases Mechanism Parasitic diseases Trauma Strongyloidiasis, enterobiasis, taeniasis, clonorchiasis, schistosomiasis and hookworm infection7 The disease is the clinical manifestation of the infection which shows the active presence and replication of the parasite causing damage in the host. It may be mild, severe, fulminant（爆发 性的）,and in some cases may even cause death of the host. The person who is infected with the parasite but without any clinical or sub clinical diseases is referred to as a carrier. PARASITIC ZOONOSES(人兽共患病) These are the infections which are naturally transmitted between the vertebrate animals and man. The condition usually includes those infections in which the proof of strong circumstantial evidence of transmission between the man and animals are documented. PATHOGENESIS AND PATHOLOGY（发病机制与病理学） Pathogenesis（发病机制） of the parasitic diseases is a dynamic process and depends on the complex interaction of a variety of host and parasitic factors. Host factors The host factor include: 1) Nutritional status of the host, whether malnutrition or under nutrition. 2) Immune response to parasitic infection 3) Immune status of the host whether there is immuno-suppression or not. 4) The presence or absence of the co-existing disease or other physiological conditions such as pregnancy, and 5) The age and level of the immunity at the time of infection. Parasitic factors The parasitic factors include: 1) Site of the attachment of the parasite and the size of the parasite. 2) Number of invading parasites, and 3) Parasite strain(pathogenic or non-pathogenic) and the growth, development and multiplication of parasites inside the human body and their metabolic products. The parasites can cause disease in man in various ways as follows: trauma by adult worm, larva, and egg(e.g., hookworm cause oozing of the blood at the site of attachment); Invasion and destruction of host cell(Plasmodium and Toxoplasma are obligate intracellular parasites of man , they produce several enzymes which cause digestion and necrosis of host cells); Inflammatory reaction(many of the parasite induce inflammatory reactions in the host leading to the formation of various pathological lesions); Toxin(parasites like bacteria also produce toxins but they appear to have a minimal role in the pathogenesis of the disease processes; Allergic manifestation(many of the metabolic and excretory products of the parasites absorbed in the circulation, produce a variety of immunological and allergic manifestations in the sensitized hosts). Various pathogenic mechanisms in parasitic diseases are summarized in the below table Ⅰ-Ⅰ-2. The parasitic infections usually are designate by generic names of the parasites ending with -iasis or –osis. (e.g., Schistosoma infection is called as schistosomiasis) TableⅠ-Ⅰ-2 Pathogenic Mechanisms in Parasitic Diseases Mechanism Parasitic diseases Trauma Strongyloidiasis, enterobiasis, taeniasis,clonorchiasis, schistosomiasis and hookworm infection