All 6 entries tagged Epidemiology
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September 12, 2007
DEFRA has confirmed what nobody wanted to hear – foot and mouth has struck in Surrey again. The BBC were reporting it a while before the official announcement came, but I guess they have better spies than I do!
The new case is about 10 miles from Pirbright, some distance from the cases we saw in August. The strain is, as yet, unknown, but I think the assumption until proven otherwise must be that this will be the same O1 BFS67 strain that leaked from the Pirbright site to cause the earlier outbreak. The HSE’s final report into biosecurity at Pirbright makes for uncomfortable reading – while we will never know which of the three facilities on-site leaked the virus, it seems that there were several significant failings in the category 4 biosecurity arrangements on that site which combined with heavy flooding to cause the outbreak.
What’s got me scratching my head is the time-lag before this outbreak; indeed, when I heard this morning there was a suspect case, I was assuming it would turn out not to be confirmed. FMDV (the virus that causes foot and mouth) doesn’t survive for long in the environment, so why has this case appeared now, given the last infected animals were culled on the 9th of August? The OIE’s handy summary gives 14 days as the upper end of the incubation period. It can survive in the environment if conditions are suitable for up to a month, but the previous infectious premises will have been rigorously disinfected.
I think that means that direct transmission from the August infectious premises is fairly unlikely to be the cause of this outbreak. I can’t find another more plausible hypothesis, though; did more contaminated soil leave Pirbright during the recent past (surely not, biosecurity was substantially tightened up during the HSE investigation)? are there other infectious animals out there that we haven’t spotted (again, this new case is only just outside the old surveillance zone, so animals nearby would have been inspected regularly)? Even if it is direct transmission from the previous infected farms, how did the virus escape disinfection? At this stage, we will have to wait and see. Easier to do as an epidemiologist than as a farmer, trying to get back on track after the previous round of movement restrictions…
August 20, 2007
Writing about web page http://www2.warwick.ac.uk/newsandevents/audio/?podcastItem=footandmouth.mp3
Last week I was interviewed about foot and mouth disease (and my research, which doesn’t address foot and mouth specifically, but rather looks at the impact of livestock movements on the dynamics of farm animal diseases more generally) by Tom Abbott of the Communications Office.
I find I tend to “dry up” the moment someone points a microphone (or, worse, a camera) at me, but I think the interview went reasonably well, and it helped that Tom had done his homework about the current outbreak. In any case, you can hear the edited result here. It’s always a bit odd hearing your own voice played back to you!
August 08, 2007
Writing about web page http://www.hse.gov.uk/news/archive/07aug/pirbright.htm
DEFRA have confirmed that a second farm has been culled, and foot and mouth disease confirmed. The second farm is within the original Protection Zone, so this doesn’t represent a significant geographic spread. There’s an interesting question as to whether this is another primary case, or whether it was infected by the first farm. It may never be possible to answer this unambiguously, but everyone will be hoping it’s another primary case, as that would mean that there have been no secondary cases so far still. This would be good, as it would mean that the current containment policies appear to be working.
The Health and Safety Executive has published its initial report on the suspected biosecurity breaches at the Pirbright site. I noted yesterday that Pirbright was the likely source of this outbreak, and I’m a little disappointed to note that the HSE report doesn’t tell us much more than what we already knew or could surmise. It rules out airborne spread as a “negligible likelihood”. The likelihood of waterborne spread is also assessed to be “negligable”, although further investigations are being carried out.
That leaves human movement as “a real possibility”. Again, further investigations are being carried out. That would be embarrasing if it were shown to be the case! The tabloids have been making much of the HSE’s failure to rule out deliberate sabotage, but that seems unlikely to me: if you wanted to release FMD, you wouldn’t pick a bit of Surrey that’s only lightly populated by livestock farms to do it in, and you’d pick a time of year when there were more movements of animals going on. Hopefully we’ll actually have some useful findings from the HSE in due course…
August 06, 2007
I’ve just got back from the Society for Mathematical Biology annual meeting in San Jose; my colleagues and I were a little concerned to hear of a confirmed outbreak of foot and mouth disease (FMD) on a farm in Surrey last Friday.
It’s too early to say for definite how this outbreak will pan out, but a few things can be noted now. Firstly, the government moved quickly – following initial reports, a temporary restriction zone (1km) was put in place at around noon on Friday, and by 9pm FMD had been confirmed, and movements of susceptible cattle halted nation-wide. This is marked contrast to previous epidemics in 1951,1967, and 2001, when (as noted by the enquiries that followed each outbreak) movement restrictions were not put in place rapidly enough, which made those outbreaks considerably worse than they might otherwise have been.
There is no sign as yet of secondary cases, which is positive (although given a normal latent period of 3-6 days, we cannot be sure that there won’t be some still to come); we don’t have much live data to go on as yet, but given movement data from previous years and the local geography, spread outside the current 10km Surveillance Zone seems unlikely. I hope I don’t end up eating my words…!
The strain isolated from the culled animals is very similar to the 1967 epidemic’s strain, which isn’t thought to be currently “at large”, raising the question of where it came from. The nearby laboratory site at Pirbright seems a likely candidate, althought that has yet to be confirmed. The Institute for Animal Health, the world reference laboratory for FMD (amongst other things!) is on that site, as is Merial’s FMD vaccine manufacture plant. Both have 1967-strain FMDV, the latter in rather larger quantities than the former. Both have strict biosecurity controls; it will be interesting to see the results of the HSE’s investigation, due tomorrow.
In the mean time, we can just wait and see what unfolds. Interesting times…
May 16, 2007
One of the joys of academic life is going to conferences. Organising committees tend to pick pleasant bits of the world, and your grant will usually fly you there and back, and pay for the conference hotel. Sometimes you can even use a bit of holiday time up while you’re out there! I’ll elide for a moment the fact that the hotel is often in a rather out-of-the-way place, you usually have to pay for your own food and drink, and that your grant won’t pay for your spouse to join you…
Recently, I went to a conference in Corfu, where I presented a poster about some of the work I did for my PhD (if you’re interested, an A4 version for you to print out and put on your wall is here. ). These days, however, you can’t take a poster tube into the cabin with you, as it’s a security risk (so they say). I slightly nervously committed it to the plane’s hold, and hoped it would make it to the other end. It did, and was quite well received at the conference.
Getting it home again was another matter; my poster tube eventually popped out of the “outsize baggage” claim at LHR, with part of the lid missing (which means the label with my address was gone, and that it’ll no longer keep water out). So, I queue at the euphemistically-named “baggage enquiries point”, and a slightly confused lady fights with their tickybox-system which has not category for poster-tubes. Eventually, she fills out a form in triplicate, and attaches a note explaining what the item actually is. Someone will be in touch in the next couple of days, she says, and they will arrange someone to come and inspect the damage and to decide on repair or replacement.
That seems a lot of effort for a £35 poster tube, but hey. Anyhow, in due course I phone them back to inquire what’s going on, and explain everything again to someone who seems unable to find my records from the first time round. She says someone will call within a fortnight to arrange to come and look at it. Yesterday at work, I get a call “Err, was anyone at home this afternoon?” “No.” “Oh. When could you be around?”. So, this morning, I worked from home until there was a knock at the door, and a cheery man says “I’ve got a case for you”. I look at his large box, and say. “I don’t think that’s right”. I show him the damaged poster tube and observe that it’s unlikely to be packaged up in a box the size he’s put down in my porch.
He opens his box and confirms that it was a large suitcase they were trying to deliver. He makes a note, is very apologetic, and departs.
I wonder when I’ll get my new poster tube? I also wonder whether it wouldn’t have just been easier for them to let me replace it myself and send them the bill!
February 05, 2007
Unless you have a policy of avoiding the news entirely, you can’t have failed to notice that “Bird ‘flu” is making headlines again. The highly pathogenic H5N1 strain has been confirmed in turkeys on a farm in Suffolk, which is now being culled out. An awful lot of ink (and electrons) has been spilled already on the subject, so I shall try and be concise! Personally, I’ve been pleased to see that the press have been finding epidemiologists to ask about what’s going on rather than just speculating wildly, which is what we’ve tended to see in the past.
The big question, in my opinion, is where this outbreak came from. The affected unit, like most industrial poultry farms, has tight biosecurity, designed to keep wildlife (rodents and birds) out. Speculative reports have suggested a wild bird got into a ventillation shaft (or managed to excrete virus-laden faeces in precisely the right location), but that seems unlikely to me – it’s not really the time of year for birds to be migrating into Suffolk, and any such bird would still have to get into the unit. The only other option would be imported birds which were infected overseas, but the EU has quite serious restrictions on the import of live birds. DEFRA are pursuing the investigation very seriously, and hopefully we’ll have an answer soon.
The risk to human health isn’t high, though. Granted, this strain does have a high mortality rate in people, but it has, so far, proved difficult to catch. Unless you’re working with poultry, you’re unlikely to be exposed to any great extent. Of course, it might yet mutate into a form that is readily transmissible between people, but it hasn’t yet, and I’m inclined to the opinion that it’s not terribly likely to do so in the near future. It is a matter of chance, though, and the more cases in birds, the more people will get infected, and the more opportunity for such a mutation to take place.
DEFRA will be worried about the possibility of H5N1 getting into the wild bird population, which would be a difficult situation – that would put free-range and other outdoor-reared poultry at risk, and be difficult to eradicate.
For more detail on the subject, see DEFRA’s pages here, which include an advice line, and directions for what to do if you find dead ducks, geese, swans or waders.