Institute for Medical Microbiology, Immunology and Parasitology, University Hospital Bonn, 53105, Bonn, Germany.
Parasitol Res. 2009 Nov;105(6):1531-8. doi: 10.1007/s00436-009-1588-5. Epub 2009 Sep 26.
Drugs exist that show long-lasting inhibition of embryogenesis and microfilaria production or macrofilaricidal activity against Onchocerca volvulus. Therefore, the patients have to be followed-up for several years. Clinical drug trials have to be performed in areas with ongoing transmission to assess the efficacy on younger worms. In addition, future vaccine trials may also require demonstrating efficacy against establishment of new worms. For the evaluation of the efficacy, it is necessary to differentiate between older worms, which were exposed to the drug, and younger worms newly acquired after drug treatment or vaccination. Here, we describe criteria for the differentiation between young and old filariae based on histological studies of worms with a known age from travellers, or from children, or patients living in areas with interrupted transmission in Burkina Faso, Ghana or Uganda. Older worms were larger and presented degenerated tissues. Gomori's iron stain showed that the worms accumulated more iron with increasing age, first in the gut and later in other organs. Using an antibody against O. volvulus lysosomal aspartic protease, the gut of young worms was stained only weakly; whereas, it was stronger labelled in older worms, accompanied by additional staining of hypodermis and epithelia. Using morphological and immunohistological criteria, it was possible to differentiate young (1-3 years old) from older females and to identify young males.
有一些药物可以长时间抑制胚胎发生和微丝蚴的产生，或者对盘尾丝虫具有杀微丝蚴和杀成虫的活性。因此，患者需要随访数年。必须在正在传播的地区进行临床药物试验，以评估这些药物对幼龄虫的疗效。此外，未来的疫苗试验也可能需要证明其对新感染蠕虫的有效性。为了评估疗效，有必要区分已经接触过药物的老龄虫和药物治疗或疫苗接种后新获得的幼龄虫。在这里，我们根据旅行者、儿童或布基纳法索、加纳或乌干达中断传播地区的居民中已知年龄的蠕虫的组织学研究，描述了区分幼龄和老龄丝虫的标准。老龄虫较大，呈现退行性组织变化。Gomori 铁染色显示，随着年龄的增长，蠕虫积累的铁越来越多，首先是在肠道，然后是在其他器官。使用针对盘尾丝虫溶酶体天冬氨酸蛋白酶的抗体，仅能微弱地对幼龄虫的肠道进行染色；而在老龄虫中染色则更强，同时伴有真皮和上皮的额外染色。使用形态学和免疫组织化学标准，可以区分 1-3 岁的年轻雌虫和老龄雌虫，并识别年轻雄虫。
