Reisen W K, Lothrop H D, Hardy J L
Arbovirus Research Program, School of Public Health, University of California, Berkeley 94720, USA.
J Med Entomol. 1995 May;32(3):316-27. doi: 10.1093/jmedent/32.3.316.
Population dynamics and bionomics of host-seeking Culex tarsalis Coquillett were studied in the Imperial and Coachella valleys of California during periods in 1991 and 1992 when western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses were transmitted to sentinel chickens. Female abundance was greatest during the spring and fall, before and after most virus transmission occurred and was not correlated with temperature, humidity, or rainfall. Parity rates were highest during late summer when virus activity peaked and were lowest during December when females may enter a short-term reproductive diapause. Although most likely underestimated, the proportion of older multiparous females were collected at a consistent, but low level throughout the year. Changes in the parity rate seemed to be influenced primarily by the proportions of 1-parous females. Survivorship estimated from the parity rate (adjusted to account for autogeny) was highest in winter; however, the proportion of females surviving to potentially transmit either WEE or SLE virus was highest in summer and early fall. Wing length decreased in summer as an inverse correlate of temperature and increased as a function of female age, implying that larger females lived longest. However, autogenous females were larger than anautogenous females at emergence and only parous autogenous females were collected host seeking, thereby confounding the relationship between size and age. The proportion of females testing positive for fructose was greatest during winter and lowest during summer, perhaps affecting survivorship and blood-feeding avidity. The vector competence (infection, dissemination and transmission rates, and ID50) of females collected host seeking or emerging from field-collected pupae for WEE or SLE viruses remained similar over time, even though the wing length of females used in these experiments differed among samples. We conclude that in nature virus transmission progressed efficiently during midsummer because elevated temperatures shortened the extrinsic incubation period without markedly decreasing survivorship resulting in an increased proportion of females surviving extrinsic incubation to become infective.
1991年和1992年期间，在加利福尼亚州的帝王谷和科切拉谷对寻找宿主的西方马脑炎病毒（WEE）和圣路易斯脑炎病毒（SLE）传播给哨兵鸡时的致倦库蚊的种群动态和生物学特性进行了研究。雌蚊数量在春季和秋季最多，此时大多数病毒传播发生之前和之后，且与温度、湿度或降雨量无关。产次率在夏末病毒活动达到峰值时最高，在12月雌蚊可能进入短期生殖滞育时最低。尽管很可能被低估，但老龄多产雌蚊的比例在全年都以一致但较低的水平被捕获。产次率的变化似乎主要受一产雌蚊比例的影响。根据产次率估算的存活率（调整以考虑自生现象）在冬季最高；然而，存活下来有可能传播WEE或SLE病毒的雌蚊比例在夏季和初秋最高。翅长在夏季随着温度的反比关系而减小，并随着雌蚊年龄的增长而增加，这意味着体型较大的雌蚊寿命最长。然而，自生雌蚊在羽化时比非自生雌蚊体型大，并且只有经产自生雌蚊在寻找宿主时被捕获，从而混淆了体型与年龄之间的关系。检测果糖呈阳性的雌蚊比例在冬季最大，在夏季最小，这可能影响存活率和吸血积极性。从寻找宿主或从野外采集的蛹羽化的雌蚊对WEE或SLE病毒的媒介能力（感染、传播和传播率以及半数感染剂量）随时间保持相似，尽管这些实验中使用的雌蚊翅长在不同样本之间有所不同。我们得出结论，在自然界中，病毒传播在仲夏期间高效进行，因为温度升高缩短了外在潜伏期，而没有显著降低存活率，导致存活到外在潜伏期结束并具有感染性的雌蚊比例增加。
