Food and Veterinary Service, LV 1050 Riga, Latvia.
Institute of Food Safety, Animal Health and Environment "BIOR", LV 1076 Riga, Latvia.
Viruses. 2024 Feb 22;16(3):334. doi: 10.3390/v16030334.
In the event of an outbreak of African swine fever (ASF) in pig farms, the European Union (EU) legislation requires the establishment of a restricted zone, consisting of a protection zone with a radius of at least 3 km and a surveillance zone with a radius of at least 10 km around the outbreak. The main purpose of the restricted zone is to stop the spread of the disease by detecting further outbreaks. We evaluated the effectiveness and necessity of the restricted zone in the Baltic States by looking at how many secondary outbreaks were detected inside and outside the protection and surveillance zones and by what means. Secondary outbreaks are outbreaks with an epidemiological link to a primary outbreak while a primary outbreak is an outbreak that is not epidemiologically linked to any previous outbreak. From 2014 to 2023, a total of 272 outbreaks in domestic pigs were confirmed, where 263 (96.7%) were primary outbreaks and 9 (3.3%) were secondary outbreaks. Eight of the secondary outbreaks were detected by epidemiological enquiry and one by passive surveillance. Epidemiological enquiries are legally required investigations on an outbreak farm to find out when and how the virus entered the farm and to obtain information on contact farms where the ASF virus may have been spread. Of the eight secondary outbreaks detected by epidemiological investigations, six were within the protection zone, one was within the surveillance zone and one outside the restricted zone. Epidemiological investigations were therefore the most effective means of detecting secondary outbreaks, whether inside or outside the restricted zones, while active surveillance was not effective. Active surveillance are legally prescribed activities carried out by the competent authorities in the restricted zones. Furthermore, as ASF is no longer a rare and exotic disease in the EU, it could be listed as a "Category B" disease, which in turn would allow for more flexibility and "tailor-made" control measures, e.g., regarding the size of the restricted zone.
在养猪场发生非洲猪瘟 (ASF) 疫情时，欧盟 (EU) 法规要求建立一个限制区，该限制区由一个保护半径至少为 3 公里的保护区和一个监测半径至少为 10 公里的监测区组成。限制区的主要目的是通过检测进一步的疫情爆发来阻止疾病的传播。我们通过查看在保护和监测区内外检测到的继发性疫情数量以及通过何种手段来评估在波罗的海国家实施限制区的有效性和必要性。继发性疫情是与原发性疫情有流行病学联系的疫情，而原发性疫情是与任何先前疫情没有流行病学联系的疫情。2014 年至 2023 年，共确认国内猪只发生 272 起疫情，其中 263 起（96.7%）为原发性疫情，9 起（3.3%）为继发性疫情。其中 8 起继发性疫情是通过流行病学调查发现的，1 起是通过被动监测发现的。流行病学调查是对疫情农场进行的法律要求的调查，以了解病毒何时以及如何进入农场，并获取可能传播 ASF 病毒的接触农场的信息。在通过流行病学调查发现的 8 起继发性疫情中，有 6 起发生在保护区内，1 起发生在监测区内，1 起发生在限制区外。因此，流行病学调查是检测限制区内外继发性疫情最有效的手段，而主动监测则无效。主动监测是指主管当局在限制区内进行的法定规定活动。此外，由于 ASF 在欧盟不再是一种罕见和外来疾病，它可以被列为“B 类”疾病，这反过来又可以允许更灵活和“定制”的控制措施，例如，关于限制区的大小。
