TRANSMISSION OF PARASITES It depend upon: Source or reservoir of infection, and Mode of transmission Source ofinfection(传染源 1)Humans Humans is the source or reservoir in a majority of parasitic infections(e. g taeniasis, amoebiasis, etc). The condition in which the infection is transmitted from one infected man to another man is called anthroponosis(人类传染病) 2)Animal In many of the parasitic diseases, animals act as the source of infection. The condition where infection is transmitted from animals to humans is called zoonoses人兽共患病 (eg, hydatid disease包虫病) Mode of transmission(传播方式) Transmission of infection fiom one host to another; cause by a certain form of the parasite is known as the infective stage. The infective stage of various parasites many be transmitted fiom one host to another in the following ways 1)Oral route Ingestion of food, water and vegetable: The infection is transmitted orally by ingestion of food, water or vegetables contaminated by the faeces that contain the infective stages of the parasite. This mode of transmission is referred to as faecal-oral route(e.g, cysts of Giardia intestinalis贾第虫 and Entamoeba histolytica溶组织阿米巴; ova of Ascaris lumbricoides蛔虫, Trichuris trichura鞭虫 and Enterobius vermicularis蛲虫) ngestion of raw or undercooked meat: The infection is transmitted orally also by ingestion of raw or undercooked meat harbouring the infective stage of the parasite(e. g, pork containing cysticercus cellulosae猪囊尾蚴, the larval stage of Taenia solium猪带绦虫) Ingestion of raw or uncooked fish and crab: Infection is transmitted by ingestion of raw or infective stage of the parasite(e. g, crab or cray fish containing the metacercariae of Paragonimus esterman卫氏并殖吸虫i, fish harbouring the metacercariae囊蚴 of Clonorchis sinensis华支睾 吸虫/肝吸虫,etc) Ingestion of raw or under cooked water plants: Infection can be transmitted bt eating raw or under cooked water plants harbouring the infective form of the parasite(e.g, water chest nuts, etc containing metacercariae of Fasciolopsis buski布氏姜片虫 and Fasciola hepatica肝片形吸虫) 2) Penetration of the skin and mucous membrane The infection is transmitted by A)Penetration of the intact skin by filariformlarvae2i#h)of hookworm, Sreongyloides stercoralis on coming in contact with faecally polluted soil, and B) Piercing the skin by cercariae of Schistosoma japonicum日本血吸虫, S mansoni曼氏 血吸虫andS. haematobium埃及血吸虫 on coming in contact with infected water. 3)Inoculation by an arthropod vector The infection also can be transmitted by A) ne blood by Anopheles( 疟原虫) B) Inoculation into the skin by mosquitoes( vectors for Wuchereria bancrofti斑氏丝虫 Brugia malayi马来丝虫 Trichomonas is transmitted by sexual contact. Frequently, Entamoeba also is transmitted by sexual contact among homosexuals(同性恋) HOST-PARASITE EXISTENCE Establishment of the parasite in its host is referred to as an infection The outcome of the infection is highly variable. It may be(a) sub-clinical latent infection,(b) clinical disease or(c) carrier(携带者) 66 TRANSMISSION OF PARASITES It depend upon: Source or reservoir of infection, and Mode of transmission. Source of infection（传染源） 1) Humans Humans is the source or reservoir in a majority of parasitic infections(e.g., taeniasis, amoebiasis, etc). The condition in which the infection is transmitted from one infected man to another man is called anthroponoses(人类传染病). 2) Animal In many of the parasitic diseases, animals act as the source of infection. The condition where infection is transmitted from animals to humans is called zoonoses 人兽共患病 (e.g., hydatid disease 包虫病). Mode of transmission（传播方式） Transmission of infection from one host to another, cause by a certain form of the parasite is known as the infective stage. The infective stage of various parasites many be transmitted from one host to another in the following ways. 1) Oral route Ingestion of food, water and vegetable: The infection is transmitted orally by ingestion of food, water or vegetables contaminated by the faeces that contain the infective stages of the parasite. This mode of transmission is referred to as faecal-oral route(e.g., cysts of Giardia intestinalis 贾第虫 and Entamoeba histolytica 溶组织阿米巴； ova of Ascaris lumbricoides 蛔虫, Trichuris trichura 鞭虫 and Enterobius vermicularis 蛲虫). Ingestion of raw or undercooked meat: The infection is transmitted orally also by ingestion of raw or undercooked meat harbouring the infective stage of the parasite(e.g., pork containing cysticercus cellulosae 猪囊尾蚴, the larval stage of Taenia solium 猪带绦虫). Ingestion of raw or uncooked fish and crab: Infection is transmitted by ingestion of raw or under cooked fish and crab containing the infective stage of the parasite(e.g., crab containing the infective stage of the parasite(e.g., crab or cray fish containing the metacercariae of Paragonimus westerman卫氏并殖吸虫i, fish harbouring the metacercariae 囊蚴of Clonorchis sinensis华支睾 吸虫/肝吸虫, etc). Ingestion of raw or under cooked water plants: Infection can be transmitted bt eating raw or under cooked water plants harbouring the infective form of the parasite(e.g., water chest nuts, etc., containing metacercariae of Fasciolopsis buski 布氏姜片虫 and Fasciola hepatica 肝片形吸虫). 2) Penetration of the skin and mucous membrane The infection is transmitted by A) Penetration of the intact skin by filariformlarvae（丝状蚴）of hookworm, Sreongyloides stercoralis on coming in contact with faecally polluted soil, and B) Piercing the skin by cercariae of Schistosoma japonicum 日本血吸虫, S. mansoni 曼氏 血吸虫 and S. haematobium 埃及血吸虫 on coming in contact with infected water. 3) Inoculation by an arthropod vector The infection also can be transmitted by A) Inoculation into the blood by Anopheles(vector for Plasmodium 疟原虫). B) Inoculation into the skin by mosquitoes(vectors for Wuchereria bancrofti 斑氏丝虫, Brugia malayi 马来丝虫 etc). 4) Sexual contact Trichomonas is transmitted by sexual contact. Frequently, Entamoeba also is transmitted by sexual contact among homosexuals（同性恋）. HOST-PARASITE EXISTENCE Establishment of the parasite in its host is referred to as an infection. The outcome of the infection is highly variable. It may be(a) sub-clinical latent infection, (b) clinical disease or (c) carrier（携带者）