Medical Complex, Indian Council of Medical Research-Vector Control Research Centre (ICMR-VCRC), Indira Nagar, Puducherry, 605006, India.
Indian Council of Medical Research, Ramalingaswami Bhawan, Ansari Nagar, New Delhi, 110029, India.
Parasit Vectors. 2022 Jun 21;15(1):221. doi: 10.1186/s13071-022-05345-0.
ICMR-Vector Control Research Centre, Puducherry, India, developed two colonies of Aedes aegypti infected with wMel and wAlbB Wolbacia strains called Ae. aegypti (Pud) lines for dengue control. The sensitivity of wMel and wAlbB strains in Ae. aegypti (Pud) lines to heat stress was studied.
wMel and wAlbB infected and uninfected Ae. aegypti larvae (first to fourth instars) were reared in the laboratory to adults at 26 °C, 30 °C, 36 °C and 40 °C constant temperatures and also 26-30 °C, 26-36 °C and 26-40 °C diurnal cyclic temperatures. The adults were tested for Wolbachia infection. Experiments were also carried out rearing the larvae under simulated field conditions in summer (April and June) under sunlight using fully open and half open bowls and also under sunlight and natural shade.
At 36 °C and 40 °C constant temperatures, complete larval mortality was observed. At 30 °C and 26 °C, no larval mortality occurred, but Wolbachia density was relatively low in wMel infected males compared to control (maintained at 26 ± 1 °C). At diurnal cyclic temperature of 26-40 °C, Wolbachia density was reduced in males of both the (Pud) lines, but not in females. At 26-36 °C, reduction in Wolbachia density was observed in wMel males but not in wAlbB males. At 26-30 °C, no significant reduction in Wolbachia density was observed with wMel and wAlbB strains. In simulated field conditions (April), under sunlight, the daytime water temperature reached a maximum of 35.7 °C in both full and half open bowls. No larval mortality occurred. Wolbachia frequency and density was reduced in wMel-infected Ae. aegypti (Pud) males from both type of bowls and in females from full open bowls, and in wAlbB males from half open bowls. In June, rearing of larvae under sunlight, the first-instar larvae experienced a maximum daytime water temperature of > 38 °C that caused complete mortality. No larval mortality was observed in bowls kept under shade (< 32 °C).
Exposure of larvae to higher rearing temperatures in the laboratory and simulated-field conditions reduced the densities of wMel and wAlbB strains particularly in males, but the impact was more pronounced for wMel strain. The actual effect of heat stress on the stability of these two Wolbachia strains needs to be tested under natural field conditions.
印度医学研究理事会-病媒控制研究中心在印度本地培育了两个携带 wMel 和 wAlbB Wolbachia 菌株的埃及伊蚊（Aedes aegypti）种群，称为 Ae. aegypti（Pud）系，用于登革热控制。本研究旨在研究 wMel 和 wAlbB 菌株在 Ae. aegypti（Pud）系中的耐热性。
实验室中，用 26°C、30°C、36°C 和 40°C 恒温以及 26-30°C、26-36°C 和 26-40°C 昼夜循环温度饲养感染和未感染 wMel 和 wAlbB 的埃及伊蚊（Aedes aegypti）幼虫（1-4 龄）至成虫。对 Wolbachia 感染情况进行检测。实验还在夏季（4 月和 6 月）的野外条件下进行，使用完全开放和半开放碗以及自然光和自然阴影，在模拟的野外条件下饲养幼虫。
在 36°C 和 40°C 恒温下，完全观察到幼虫死亡。在 30°C 和 26°C 时，幼虫没有死亡，但与对照组（保持在 26°C±1°C）相比，wMel 感染雄蚊中的 Wolbachia 密度相对较低。在昼夜循环温度为 26-40°C 时，两种（Pud）系的雄蚊中 Wolbachia 密度降低，但雌蚊中没有降低。在 26-36°C 时，wMel 雄蚊中 Wolbachia 密度降低，但 wAlbB 雄蚊中没有降低。在 26-30°C 时，wMel 和 wAlbB 菌株的 Wolbachia 密度没有显著降低。在模拟野外条件（4 月）下，在阳光下，全日水温在全开放和半开放碗中均达到 35.7°C 的最大值。幼虫没有死亡。在全开放碗中，wMel 感染的 Ae. aegypti（Pud）雄蚊和雌蚊以及半开放碗中的 wAlbB 雄蚊的 Wolbachia 频率和密度均降低。在 6 月，在阳光下饲养幼虫，初孵幼虫经历的日间水温最高可达>38°C，导致完全死亡。在阴凉处（<32°C）的碗中，幼虫没有死亡。
实验室和模拟野外条件下幼虫暴露于较高的饲养温度会降低 wMel 和 wAlbB 菌株的密度，特别是在雄蚊中，但对 wMel 菌株的影响更为明显。需要在自然野外条件下测试热应激对这两种 Wolbachia 菌株稳定性的实际影响。
