Hutber A M, Kitching R P, Conway D A
Computing Department, Institute for Animal Health, Pirbright, UK.
Trop Anim Health Prod. 1998 Aug;30(4):217-27. doi: 10.1023/a:1005071027414.
Foot-and-mouth disease (FMD) within Saudi Arabian dairy herds has been controlled for the past decade through vaccination. Data from 19 outbreaks on Saudi farms has suggested that the durability of these vaccines extended for 2.5 months, providing an 81-98% level of protection. Vaccination has nevertheless failed to prevent the establishment and sometimes persistence of the disease. This is probably because the highly contagious nature of FMD creates increasing levels of viral excretion during an outbreak, and the co-habitation in Saudi farms of affected/susceptible animals following diagnosis, predisposes the herds to re-infection. Pre-clinical excretion of the virus leads to the infection of additional in-contact susceptible animals prior to diagnosis, so the isolation of clinically infected animals does not guarantee a removal of infection. Saudi Arabian farms are subdivided into managed farm pens and isolation (away from the farm) of all animals in infected pens not only removes the infectious individuals showing clinical signs, but also those that are sub-clinical and excreting virus. Simulations suggest that removing all infectious animals from the herd significantly reduces the per cent infected in the herd.
在过去十年中，沙特阿拉伯奶牛群中的口蹄疫通过疫苗接种得到了控制。来自沙特农场19次疫情的数据表明，这些疫苗的有效期延长了2.5个月，提供了81%-98%的保护水平。然而，疫苗接种未能阻止该疾病的发生，有时也未能阻止其持续存在。这可能是因为口蹄疫的高传染性导致疫情期间病毒排泄水平不断增加，而且在沙特农场中，确诊后患病/易感动物共同饲养，使牛群易受再次感染。病毒的临床前排泄会导致在诊断前更多接触病毒的易感动物被感染，因此隔离临床感染动物并不能保证消除感染。沙特阿拉伯的农场被细分为管理的农场围栏，将感染围栏中的所有动物隔离（远离农场）不仅可以清除出现临床症状的感染个体，还可以清除那些亚临床且正在排泄病毒的个体。模拟结果表明，从牛群中清除所有感染动物可显著降低牛群中的感染百分比。
