丝虫是由节肢动物传播的一类线虫,寄生于人体的已知有8种,其中班氏丝虫和马来丝虫引起的淋巴丝虫病（Filariasis)及由盘尾丝虫所致的"河盲症"对人类危害最严重。我国只有前两种：班氏吴策线虫（Wuchereria bancrofti)和马来布鲁线虫（Brugia malayi)。
一、形态
成虫
乳白色，细长如丝线，体长不到1cm；雄虫尾端卷曲半到3圈，具交合刺。雌虫大于雄虫，尾端直。
班氏与马来微丝蚴形态鉴别
|
项目 |
班氏微丝蚴 |
马来微丝蚴 |
| 体态 头隙 尾核 |
柔和，弯曲 较大较短，长短于宽；清晰可数 无 |
硬直，大弯上有小弯 较长，长大于宽；不易数清 有2个，前后排列 |
Microfilaria of Wuchereria bancrofti
stained with haematoxylin. Sheath is visible at the posterior end. ×400. Enlarged by 5.4.
Microfilaria of Wuchereria bancrofti
stained with Giemsa. Sheath is not stained, but appears as an empty space. ×400. Enlarged by 5.4.
Microfilaria of Brugia malayi
stained with Giemsa. The sheath takes a dark pink stain. ×400. Enlarged by 5.4.
Microfilaria of Brugia malayi
showing the terminal nuclei and the darkly staining sheath. Giemsa. ×800. Enlarged by 5.4.
Microfilaria of Brugia malayi
showing the terminal nuclei. Acridine orange. ×800. Enlarged by 5.4.
感染期幼虫又叫丝状蚴，寄生于蚊体内，为感染阶段。
