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''Ascaridia'' is the name of a genus of parasitic nematodes. Members of the genus are primarily intestinal parasites of birds.〔Yamaguti, S. (1961). '' Systema Helminthum. 3. The nematodes of vertebrates''. Interscience Publishers, New York and London, pp. 1261〕 There are three well known species, namely, ''A. galli'' found mostly in chicken, ''A. dissimilis'' in turkeys, and ''A. columbae'' in pigeons. Lesser known species such as ''A. hermaphrodita'', ''A. sergiomeirai'', ''A. ornata'', ''A. nicobarensis'' and ''A. platyceri'' are found in parrots.〔Kajerova V, Barus V, Literak I (2004). (Nematodes from the genus ''Ascaridia'' parasitizing psittaciform birds: a review and determination key ). ''Vet. Med. – Czech'', 49 (6): 217–223.〕 Among these ''A. galli'' is the most important and most pathogenic species, responsible for 'ascaridiasis' of poultry.〔Griffiths HJ (1978). ''A Handbook of Veterinary Parasitology: Domestic Animals of North America''. University of Minnesota Press, Minneapolis, Minnesota, USA, pp. 46-47.〕 The eggs of these nematodes are characterized by a thick shell, smooth and ellipsoidal, and composed of three distinct layers. The eggs of ''A. dissimilis'' is marginally bigger than ''A. galli'' and ''A. columbae'' in marginally smaller. All these ascarid eggs are very similar in appearance to ''Heterakis gallinarum''. All three species exhibit a direct life cycle involving the release of eggs into the soil and the subsequent re-ingestion of them in food. ''A. columbae'' may also migrate through the liver. ==Clinical signs & diagnosis== Symptoms of heavy infection include anorexia, diarrhea, stunted growth, listlessness, a change in behavior and enteritis. Heavy infections can cause a partial or total obstruction of the gastrointestinal tract. Laying hens may produce soft eggs with thin and misshapened shells. Clinical signs are more common in young chickens less than three months old as older chicken develop some resistance to infection. Infection may be diagnosed on clinical signs and fecal examination. Alternatively, postmortem examination should demonstrate enteritis - caused by the emergence of larvae from the mucosa. The gastrointestinal tract may also be distended in chronic cases. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ascaridia」の詳細全文を読む スポンサード リンク
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