Sitting in New Zealand, which as of 15 June had had its 24th consecutive day of no new cases and had no active cases of coronavirus, I feel very privileged, especially when I look at the UK where the death rate per head of population is among the highest in the world. I suspect it will be many years before the reasons for the failure of the UK to effectively control SARS-CoV-2 will be identified, but it is still worth looking at the response in New Zealand and comparing issues in disease control in cattle.
Herd immunity reflects the idea that once enough animals have been exposed the disease transmission is effectively controlled. The problem is that herd immunity is not an end state but part of a dynamic process. In some diseases, herd immunity wanes and disease comes back (BVD and Mycoplasma spp.), in others we never seem to get there (possibly bovine TB). So, herd immunity is not an end in itself, and there are no cattle diseases that have ever been successfully controlled by natural herd immunity, so it seems strange to hear people suggesting it as a stopgap measure for coronavirus. The approach in NZ was the opposite — stamp down on transmission and minimise community spread as soon as possible. This was effectively the same approach used to control M. bovis — elimination of community spread based on a model that suggested getting herd immunity would cost over NZ $1.2 billion (£600 000).
Testing and tracing is the cornerstone of any disease control programme that aims to limit disease spread. The COVID-19 outbreak has shown that across the world public health programmes have failed to plan effective testing and tracing programmes. The concept that a test is useful only when you get a result should be obvious! Like the UK's programme, New Zealand's test and trace response wouldn't win any awards, but because they started earlier the initial failure was less important. The same applied at the start of the Mycoplasma spp. outbreak: there was a lack of resources and poor co-ordination; however, lessons have been learned and testing and tracing is now very effective (helped by the reduction in new cases). For COVID-19, it's not clear that the testing and tracing could cope any better with another New Zealand outbreak.
Of course the major difference between coronavirus testing and tracing and that for a veterinary disease is the legal requirement to record all livestock movements. This is hugely beneficial — and the complete failure of the New Zealand national identification programme (NAIT) to effectively track cattle movements highlights this. This is never going to be feasible for most human movements, even with the introduction of government apps and QR codes.
Biocontainment was the clear goal of the New Zealand COVID-19 lockdown. It was a clear decision with clear guidelines which was adhered to by almost everybody. This has been one of the successes of the Mycoplasma response too — strict movement controls starting when the farm becomes a suspect farm. This approach needs to be applied as long as the risk is present. Dropping biocontainment too quickly risks the disease returning and returning. Such decisions are easier where the biocontainment results in effective prevention of community transmission. Once you control a disease you need to stop it coming back. For New Zealand border security is crucial. Quarantine of arrivals was the first measure applied and will be the last measure to be completely lifted. Biosecurity can come at a significant cost. International tourism is a huge money earner for New Zealand, second only to the dairy industry. The current restrictions on travel, which only allow essential workers to come in, are costing a huge amount of money. The contrast with veterinary biosecurity is illuminating. The Mycoplasma spp. outbreak has effectively permanently ended live cattle imports into New Zealand, but the cattle industry can cope with just importing germplasm and relying principally on home-grown genetics. New Zealand cannot replace overseas tourists with home-grown ones!
So, how do we move back to nearer normal? For New Zealand it seems to be to wait for herd immunity through vaccination.