Department of Veterinary Medical Sciences, University of Bologna, 40064 Bologna, Italy.
Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia-Romagna, 25124 Brescia, Italy.
Viruses. 2023 Aug 20;15(8):1771. doi: 10.3390/v15081771.
West Nile (WNV) and Usutu (USUV) viruses are two mosquito-borne viruses belonging to the family and genus Flavivirus. The natural transmission cycle of WNV and USUV involves mosquitoes and birds, while mammals are thought to be accidental hosts. The goal of this study was to report-in the context of "off-season monitoring" and passive surveillance-the detection of WNV and USUV RNA in wild birds. To this end, we analyzed biological samples of wild birds in Northern Italy, from October to May, hence outside of the regional monitoring period (June-September). The virological investigations for the detection of USUV and WNV RNA were performed using real-time PCR on frozen samples of the brain, myocardium, kidney, and spleen. In a total sample of 164 wild birds belonging to 27 different species, sequences of both viruses were detected: four birds (2.44%) were positive for WNV and five (3.05%) for USUV. Off-season infections of WNV and especially USUV are still widely discussed and only a few studies have been published to date. To the best of our knowledge, this study is the first report on the detection of USUV RNA until December 22nd. Although further studies are required, our results confirm the viral circulation out-of-season of Flavivirus in wild birds, suggesting reconsidering the epidemiological monitoring period based on each individual climate zone and taking into consideration global warming which will play an important role in the epidemiology of vector-borne diseases.
西尼罗河（WNV）和乌苏图（USUV）病毒是两种蚊媒病毒，属于 和属 Flavivirus。WNV 和 USUV 的自然传播周期涉及蚊子和鸟类，而哺乳动物被认为是偶然宿主。本研究的目的是报告在“淡季监测”和被动监测的背景下，野生鸟类中WNV 和 USUV RNA 的检测情况。为此，我们分析了意大利北部的野生鸟类生物样本，时间为 10 月至 5 月，即在地区监测期（6 月至 9 月）之外。使用实时 PCR 对冷冻的大脑、心肌、肾脏和脾脏样本进行了针对 USUV 和 WNV RNA 的病毒学检测。在总共 164 只属于 27 个不同物种的野生鸟类样本中，检测到了两种病毒的序列：4 只鸟（2.44%）WNV 阳性，5 只（3.05%）USUV 阳性。WNV 和特别是 USUV 的淡季感染仍在广泛讨论中，迄今为止只有少数研究发表。据我们所知，这是迄今为止首次报告检测到 USUV RNA 直到 12 月 22 日。尽管还需要进一步研究，但我们的结果证实了 Flavivirus 在野生鸟类中的季节性传播，这表明应根据每个单独的气候带重新考虑流行病学监测期，并考虑到全球变暖，这将在虫媒疾病的流行病学中发挥重要作用。
