FMD 2007 – epidemiological enigmas

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The recent epidemiology report about 2007’s Foot and Mouth Disease is about as clear as mud to the non-expert. But there are some very interesting parts of the document, published 30th Sept by the National Emergency Epidemiology Group to inform Defra. A few examples follow. (Key: IP = infected premises. An outbreak.)

The report mentions Windsor Great Park – with famous Red Deer herds – has some areas within the Protection Zone and those have been closed to the public. But epidemiologists warn that FMD in the deer “may be mild and inapparent” as with sheep. However it says very little about wild deer, admitting, “The role of wildlife in this outbreak remains under review.”

The text highlights the way this strain of FMD (01 BFS) spreads rapidly and goes unnoticed. By the time lesions (ulcers) are 2 days old, the animal may have spread virus for 4 days. Defra’s advisors made it clear that lesion ages observed indicate some cases had been through ‘more than one generation’.

Point 21 says that at the 8th outbreak, only one animal was found with lesions typical of FMD, and these seemed to be 3 days old. It’s interesting that there were not many animals with Foot and Mouth Disease. {So these animals could have been cured.}

Point 27 states that epidemiological evidence suggests secondary spread has occured from IP5 to cause the later incidents IP6 – IP8, and perhaps some earlier cases too.

Point 29 exposes some of the evidence from gene studies. Pirbright scientists examined the genetic structure of FMD viruses found at different outbreak sites (IPs). Defra’s report states, “The results of full genome sequencing by colleagues at IAH Pirbright indicate the viruses isolated from IP3B, IP3C, IP4B, IP6, IP7 and IP8 are descendants of the isolate from IP5.” 

So the virus at site 5 went on to cause FMD outbreaks at several other places – and recent cases were not discovered in the same order they had occured. A spreadsheet on page 12 (Figure 2) shows a hypothetical account of how the disease spread from IP5. They describe the causal route to IP5 from Pirbright as being under investigation.

Download the epidemiology report HERE. (Adobe PDF)

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