As I’ve watched events unfold in England with regards to the recent Foot and Mouth Disease (FMD) outbreak, I’m struck by a couple of issues that I think deserve further consideration as USDA and the U.S. animal agriculture industries continue to develop response plans for an outbreak here.
The latest epidemiology report concludes that the premises identified as IP5, the fifth premises confirmed positive for FMD, may have been infected directly from the Pirbright site or IP1 or IP2 through fomite transmission. It is theorized that the virus was carried on a vehicle that had driven through contaminated waste water leaking from a discharge pipe originating from either the Institute of Animal Health lab or the Merial facility on the site. I find it concerning that it was possible for live virus to travel miles on the vehicle, be deposited on the roadway, picked up from the roadway by another fomite and brought into contact with susceptible animals in sufficient quantity to result in infection and clinical disease. Given this scenario, I question the effectiveness of 3km (1.9 miles) Protection zones and 10km (6.2 miles) Surveillance zones. It also emphasizes the importance of disinfecting vehicles and the dangers of transporting potentially contaminated materials. Not to mention the highly infectious nature of this virus.
Secondly, the report also indicates that IP5 was inspected by animal health experts at least 3 times before the clinical signs of the disease were detected. I bring this point up only to illustrate the potential difficulty in diagnosing this disease in the field based on clinical signs. Although I do not know the particulars of which animals were exhibiting clinical signs in this case or the level of expertise of the inspectors regarding either identifying the clinical signs associated with FMD or the species of animals they were inspecting, it raises a concern that is present in the management of all foreign animal disease outbreaks.
During the 2001 FMD outbreak in the UK I spent a month working with the Ministry of Agriculture, Fisheries and Food (MAFF, the predecessor of Defra) in Wales. One of the things I learned is that an outbreak of any significant size will require a large number of veterinary professionals. Very few of these folks will have ever seen the disease before in the field and many will not be familiar with working with the species involved.
Diagnosing FMD in sheep based on clinical signs is difficult particularly if they are affected by orf (soremouth or contagious ecthyma) or if they have been consuming rough forage both of which can cause lesions resembling FMD ulcers. The consumption of rough forage, such as thistles, briars, twigs, etc., becomes an increasing problem the longer the animals are confined to a pasture due to movement restrictions without access to other rations. In addition, sheep often do not exhibit the severe clinical signs more common in cattle and pigs. A lack of experience working with sheep also makes a thorough examination difficult. Unfamiliarity with the anatomy or "normal" idiosyncrasies of a species and methods of sampling and restraint also contribute to misdiagnosis or incomplete or inaccurate examinations. All of these factors contribute to making an accurate "clinically negative" diagnosis less than straightforward.
In this case, however, if the herd was examined 3 times (presumably by different investigators) it is concerning that the presence of the disease went undetected. A rapid on-farm screening test would greatly enhance the accuracy of herd examination. I would also note that making a clinical diagnosis of FMD is relatively easy compared to diagnosing a mildly virulent Classical Swine Fever which would be almost impossible given CSF’s clinical similarity to many common swine ailments.
Lastly, given that this outbreak arose accidentally from what should be a highly secure site with years of expertise managing the virus, should this factor into the U.S. Department of Homeland Security’s plan to construct the National Bio and Agro-defense Facility (NBAF), Plum Island’s replacement, on the U.S. mainland? Does being on an island reduce the likelihood of a similar outbreak in U.S. livestock? Or, do the significant challenges associated with continuing to operate Plum Island (i.e. high cost, inconvenience, occasional inaccessibility, security challenges, high cost of living, etc.) outweigh the likelihood of an accidental release? These are questions that I believe the U.S. livestock industry should be considering now as DHS continues to formulate plans for the future of foreign animal disease diagnosis, prevention and training.
As always, I’d welcome your comments (email: comments@aasv.org).