ヒト結膜囊に寄生した東洋眼虫の形態的特徴

Morphological features of Thelazia callipaeda in the human conjunctiva

要約　目的：ヒト結膜囊に見出された線虫の微細構造を観察することで同定できた東洋眼虫の形態的特徴の報告。症例：12月に77歳女性の左結膜囊より3隻の線虫を摘出し，光顕と走査電顕により虫体を観察した。結果：3隻の虫体は白色の糸状であり，体表に横紋理がみられた。歯牙の欠如した6角形の口腔から二分されていない食道，腸管に続き，食道の中央部に神経輪を有していた。陰門とそれに続く子宮に多数の被鞘幼虫を認め，尾部に交接刺が存在しなかったことから東洋眼虫の雌と同定した。結論：冬季に摘出された東洋眼虫の雌の子宮には多数の幼虫が存在していたことから，媒介昆虫の活動する春季に第1期幼虫を産出できるように生活史を合わせたと考えられる。

Abstract.　Purpose：To report light microscopic and ultrastructural features of Thelazia callipaeda in the human conjunctiva. Case：A 77-year-old female presented with swelling of left eyelids since one month before. Three nematodes were isolated from the conjunctival sac early December. Results：Nematodes were white and thread-like. Transverse cuticular striations covered the whole body. Mouth opening had no tooth, showed a hexagonal profile, and led to non-bifurcated esophagus, nerve center and vulvar opening. Numerous sheathed larvae were present in the uterus. Spicule was not present in the cauda. From these features, the nematodes were identified with female Thelazia callipaeda. Conclusion：Presence of numerous larvated eggs in the female nematoda indicates that they are ready to release first-stage larvae in the next spring season when the vector insects become active.