フィラリア仔虫の脱鞘現象について(I)

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Previous investigators have discussed the relationship between microfilarial periodicity and presence of microfilaria sheath. The author in making microscopic observations during the study of this relationship observed an interesting phenomenon: the kinds of ensheathed microfilaria such as Wuchereria bancrofti, Brugia malayi and B. pahangi actively cast off their sheath in vitro, if some certain environmental conditions were given. Microfilariae were observed to swarm together in boundary area between the blood cell sediment and the blood plasma in a test tube. The microfilariae were taken out by a pipette, put on the agar plate and the behavior was observed at room temperature of about 20℃. Under a phase contrast microscope, the intact microfilariae were clearly found to have a delicate sheath membrane fitting over the cuticle. After a certain time, the microfilariae began to take a peculiar pendular movement going back and forth inside the sheath. Under the repeated strong attacks of the larva, the top of the sheath was torn and microfilaria body escaped slowly through the resulting opening. The naked microfilaria moved around lively in snake like movement dragging the sheath. Some of them moved more vigorously on the agar plate and naturally migrated into the agar in violent spiral movement if the concentration of agar was 0.5 per cent. The author has counted the number of the naked microfilariae every two hours. In bancroftian microfilaria, 41.3 per cent of them already casted off their sheath in the first two hours, 65.9 per cent at 4 hours and 80.4 per cent within 8 hours respectively after placed on the agar plate. In pahangi microfilaria, incidence of the naked larva reached to 83.8 per cent within two hours. The author found that this exsheathing phenomenon also occured on the thick blood smears which were prevented from drying. The blood smears containing microfilariae were kept in a moist chamber without delay after taking them from patients or animals, and they were taken out of there at two hour intervals to dry and to staine. The smears of W. bancrofti microfilariae were stained with silver deposition technique and again with hematoxyline. The sheath was distinguishably visible as a silver blue stained membrane. The sheath of B. malayi and B. pahangi microfilaria could be stained better with Giemsa solution. It was observed that the exsheathing occured progressively during incubation according to increase of the period. In the specimens of bancroftian microfilaria, naked larvae appeared in 50.9% of the population at 4th hour, in 75.6% at 10th hour and finally in 93.7% at 20th hour showing that microfilariae cast off their sheath actively on the thick blood drops placed on the slide glass. In malayan microfilaria, similar process was also found, the rate reaching to 80.2% within 20 hours. On the other hand, in pahangi microfilaria, the rate was less than 10% even in the specimens which were incubated for 16 hours or more.著者はW. bancrofti, B.malayi, B.pahangiなどの有鞘仔虫を乾燥を防いだ濃厚血液標本や,寒天板上におくと被鞘内で虫体は特有の前後運動をおこし,大部分の仔虫が被鞘の先端から積極的に高率に脱出し.脱鞘した仔虫は活発な前進蛇行運動を行い寒天層に穿入する習性を有することを確認し,その経過を記載した宿主体内で脱鞘がおこるか否かわからないが,仔虫の感染,宿主体内での処理,更には仔虫出現の周期性の機序を考える上に重要な現象と考えられる.
長崎大学熱帯医学研究所,Institute of Tropical Medicine, Nagasaki Universityの論文
1971-09-30

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