Dealing with disease in cows and people

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).