ミクフロィラリア末梢血内出現の季節的消長に関する研究 : 特に環境温度の仔虫出現に及ぼす影響

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Many investigators of the past discussed on the seasonal fluctuation in the number of microfilaria emigrating into the peripheral circulation. To study this seasonal change, the author calculated monthly the exact population density of D. immitis microfilaria. Microfilaria density was expressed by a total number of the larva in the blood which was taken at every two hour for 24 hours. Monthly fluctuation pattern of the population showed a peak count in the summer season, usually around July and August, and then it gradually went down to the minimum at the coldest winter season, in January and February, approximately one-tenth or one-twentieth of the maximum count. It was confirmed, therefore, that microfilaria density in the peripheral blood markedly varied according to the season as other investigators already reported. However, the reasonable explanation for this phenomenon has not appeared in the past. In this observation, increase and decrease in the number of microfilaria seemed to depend on the atmospheric temperature. As part of studies on this subject, therefore, the influence of environmental temperature to the density of emigrating microfilaria was experimentally investigated by changing the temperature of the room where the animals were kept. When the room temperature was suddenly raised and maintained at 25.0℃ for about one month in winter, microfilaria increased in the number as many as several times of the initial count within two weeks and continued the same high level throughout the period of exposure to the temperature, when the temperature was lowered from 25.0℃ to 5.0℃, the microfilaria density rapidly dropped down to the initial level. The animals always maintained their normal body temperature without regard to change of the room temperature. On the other hand, raising of the room temperature has brought a significant increase of respiratory rate of animals being about twenty to thirty per minutes. Increase in the number of microfilaria caused by raising of temperature was more significant at night and the nocturnal periodicity seemed to be rather distinct. Blood of the infected dog containing the numerous larva was transfused intravenously into some non-infected dogs and rabbits in which the microfilaria could survive for long time showing a nocturnal periodicity. On this fresh hosts, there was also demonstrated a similar effect of the atmospheric temperature upon the number of emigrating microfilaria. These findings may indicate that raising of the atmospheric temperature stimulates the emigration of microfilaria into the peripheral circulation from lung capillaries and the seasonal variation in the number of microfilaria is attributed to the seasonal change of atmospheric temperature.著者は1ケ年に亘り,末梢血内に出現するD. immitis仔虫の数の季節的消長と日内周期性を観察し,更に自然感染犬,仔虫を移注した未感染犬,家兎について出現仔虫数と環境温度との関係を実験的に追究した.自然感染犬での出現仔虫数は季節により,著明な差がみられ,1,2月に最も少く,7,8月にはその約10乃至20倍に激増する.自然感染犬を入れた室温を5℃から25℃に上昇させると仔虫数はすみやかに増加し,20日前後のきわめて短期間に5℃の時の約6～50倍に増加する.再び室温を5℃に下げると仔虫数は急激な減少を示し,5℃の時の値にかえる傾向がみられる.しかしこの間,24時間内の仔虫の出現は常に正常の夜間出現性が認められる.室温の上昇で犬の呼吸数は著明に増加するが,体温は一定に保たれている.仔虫を移注した未感染犬や家兎でも同様の仔虫数に対する環境気温の影響がみられる.以上の実験結果から, D. immitis仔虫の数の季節的変動は環境温度の変動に原因することが確証された.
長崎大学熱帯医学研究所,Institute of Tropical Medicine, Nagasaki Universityの論文
1971-03-15

ミクフロィラリア末梢血内出現の季節的消長に関する研究 : 特に環境温度の仔虫出現に及ぼす影響

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