Dermatobia hominis引起癰瘡性蠅蛆症之簡介

Furuncular Myiasis Caused by Dermatobia hominis

Dermatobia hominis引起癰瘡性蠅蛆症，主要分佈是在中南美州。雌性成蟲在飛行中能擄獲吸血的節肢動物（如蚊子），釋放出卵以類似黏膠的物質吸附在 後者腹部上。這些吸血的節肢動物（稱為媒介昆蟲）在哺乳動物（牛是最常見）或禽鳥類皮膚吸血時會將這些卵放置於皮膚上，卵在宿主的體溫下能陸續孵化成幼蟲，從叮咬傷口或毛囊鑽入皮膚，到達皮下組織。幼蟲在皮下的洞穴依賴著動物的組織滲出液能活存5～12星期，透過其尾端的氣孔可以呼吸新鮮的空氣。成熟的幼蟲掉落到地上，在自然環境中變成蛹。約一個月後，蛹即能變為成蟲，可以進行交配，重複下一個生活史。處理的方法有擠壓傷口小結節中央小洞口旁，使幼蟲被推擠出來，但是幼蟲身體周圍的硬棘固定於宿主皮下周邊的組織，不易被取出。有些民俗療法塗抹傷口似乎有效，如凡士林、豬油、醃燻豬肉、指甲油等。比較大的幼蟲，還是需要手術切開取出。國際旅遊風氣盛行及台商海外投資的拓展，加上台灣很多邦交國是在中南美洲。臨床醫師對於該地區回台的國人或旅客，有表皮未癒合的傷口，需要警覺是否因馬蠅幼蟲感染造成疼痛的結節性傷口，才不致於作了很多不必要的檢查或抗生素的治療。

Furuncular myiasis, caused by Dermatobia hominis, is mainly distributed in the tropical areas of Central and South America. A female D. hominis adult can capture insects (such as mosquito) and attach her eggs to the underside of the insect with a glue-like substance. When the egg-carrying vector lands on the skin of a mammal or bird, the eggs hatch into larvae that penetrate the skin of the host by burrowing. The larva can live in a subcutaneous cyst for 5 to 12 weeks by feeding on the tissue exudates of the host and can breathe through 2 posterior spiracles. The mature larva crawls out of the host to pupate in soil. Approximately 1 month later, the adult fly emerges to complete the cycle. Myiasis can be cured by removal of the larva in a central pore of skin nodule. However, it is difficult to remove the larva because its anchoring spines will resist efforts to extract it. Some traditional methods available for the removal of larvae are to suffocate it with Vaseline, pork fat, bacon, fingernail polish, and so on. Bigger larva can probably be removed by surgical extraction. As travel to and foreign investment in endemic areas increase, clinicians should be aware of furuncular myiasis caused by D. hominis in those who have nonhealing nodular skin lesions after returning from endemic areas. Then, unnecessary examinations and antibiotics may be avoided in cases of infestation.