Parazitizm dar biologiya yak shakli hamzistii organizmhoi gunogun (rastaniho, hayvonot va mikroorganizmho)-ro guyand, ki dar jarayoni op yake (parazit) digare (homil)-ro chun muhiti zindagi va manbai gizo istifoda mebarad. Vobasta ba joi zist Parazitizm du khel meshavad: Parazitizmi beruni yo ektoparazitizm (parazit dar rui badani homil zindagi mekunad) va Parazitizmi daruni yo e n d o p a r a z i t i z m (parazit dar dokhili uzvu boftahoi homil hayot meguzaronad). Kana, shabush, pashsha va gayra parazithoi beruni, pahnkirmho, kirmk jigarmak, plazmodiya va gayra parazithoi daruni meboshand.
Baze parazitho yak davrai muayyani hayot va bazei digarashon boshand, tamomi hayotashonro dar organizmi homil meguzaronand. Rohhoi paydoishi Parazitizm khele gunogunand. Manbahoi on hamzistii organizmhoi gunogun, kommensalizm, simbioz, tasodufan furu burdani parazit, sokin shudani yak organizm ba organiami digar va gayra meboshand. Parazitizm va chorahoi ziddi on,ro parazitologiya, virusologiya, fitopatologiya va mikrobiologiya meomuzad. Namudu guruhhoi parazitho nihoyat bisyorand. Onho aksaran ba homiloni khud zarar rasonda, bemorihoi guaoguni odamu hayvonot va nabototro va vujud meorand.
Parazitizmi hayvonot. Namudhoi paraziti dar aksar guruhhoi hayvonot (ba gayr az suzanpustho va kiftpoyho) duchor meshavand. Masalan, az khordadorho minoga va mikennaho, inchunin baze kurshalarakho hayoti nimparaziti meguzaronand. Hatto guruhu sinfhoi jonvarone hastand, ki hama parazitand. Masalan, az mavjudoti soddatarin—sporovikho, az kirmhoi pahn — trematoda va monogeneyaho az hasharot — kayk, shabush va gayra. Darajai zarari parazitho ba organizmi homil har khel ast.
Bazan organizmi homil mumkin ast ba bemori giriftor nashavad, vale on manbai siroyati parazit ast. Nabototu hayvonoti gunogun homiloni parazit shuda metavonand. Aksar vaqt yak homil az chand namudi parazit siroyat meyobad. Jomea parazithoi yak homilro parazitotsenoz menomand.
Baze endoparazitho davrai muayyani inkishofashonro dar muhiti beruna guzaronida, bad ba organizmi homil vorid meshavad. Masalan, kirmhoi lunda dar khok inkishof meyoband, bad ba organizmi homil guzashta, ba voya merasand va afzoish mekunand. Aksar vaqt parazitho dar davomi yak davrai hayoti khud 2 va yo 3 homilro ivaz mekunand.
Pahnshavii geografii parazitho ba pahnshavii homiloni onho va khususiyati fizikiyu geografii muhiti mahal vobasta ast. Binobar in dar hududi areali khud parazitho dar hama jo neyu dar mavzehoi muayyan duchor meshavand. Ba pahnshavii parazitho tarzi hayoti homiloni onho (tarzi gizogiri, migratsiya, khob va gayra), iqlimi areal va omilhoi digar niz tasir mekunand.
Parazitizmi rastaniho. Bisyor zanburugho, bakteriyaho, virusho, rastanihoi guldoru baze obsabzhoi parazit malumand. Rastanihoi parazit faqat dar bayni ushna, sarakhs va rastanihoi luchtukhm to hol muayyan nashudaand. Homiloni rastanihoi parazit na faqat rastaniho, balki hayvonot va odam ham meboshand. Dar badani odam asosan bakteriyaho va baze zanburugho paraziti mekunand. Bakteriyahoi parazit ba bemorihoi sil, khunok, angina, dizenteriya, toun, vabo va gayra sabab meshavand; zanburugho boshand, asosan pustu muy va qisman shush, chashm va uzvhoi digarro illatnok mekunand.
Rastanihoe, ki paraziti digar rastanihoyand du khel meshavand: khloro- filldor va bekhlorofill. Rastanihoi paraziti khlorofilldor az homiloni khud faqat obu namakhoi mineraliro jabbida megirand va khudashon dar prosessi fotosintez moddahoi organiki tayyor mekunand. Rastanihoi paraziti bekhlorofill purra parazitand, onho az homil ham gizoi organiki va ham gizoi gayri organikiro mejabband. Dar bayni rastanihoi parazit parazithoi tasodufi (f a k u l t a t i v i) va hauiui (obligati)-ro farq mekunand. Parazithoi tasodufi ba rastanihoi az numu monda yo qismhoi az numumondan onho (masalan, meva) va parazithoi haqiqi boshand, ba rastanihon solimi numukunanda zarar merasonand.
Omuzishi jabhahoi gunoguni Parazitizm (davrahoi hayoti parazitho, rohhoi siroyati onho, ekologiyai homiloni parazitho va gayra) dar muborizai ziddi parazitho — angezandahoi bemorihoi gunoguni odam va chorvo, alalkhusus, baroi peshgirii in bemoriho ahamiyati kalon dorad.
Ad.: Pavlovskiy E. P.. Obshie problemi parazitologii i zoologii, M.— L., 1961; Dogel V. A., Obshaya parazitologiya. L., 1962; Baratov
Sh. B., Podkojnie ovodi krupnogo rogatogo skota v Tadjikistane. D., 1972.