A study of 60 outbreaks between 1992 and 2001
We received this from Dr Keith Sumption (CTVM, Edinburgh) who
thought it may
be of interest to a wider audience.
I have put this data together from studying FMD outbreaks reported to the
World Animal Health body since 1992.
In some regions the ratio of contiguous culling to infected places is high
and therefore the overall impact is much greater than the case numbers suggest.
The use of stamping-out alone is characterised by prolonged and widespread
outbreaks .
From studying 60 outbreaks internationally which occurred between 1992 and
the present, 22 of which were in non-vaccinating animal populations; the
scale (number of reported cases) of the England and Wales epidemic places
it at the second highest in the world in the last 10 years, after Taiwan in
1997. The Scottish epidemic ranks in fourth place internationally in this
period. If the
number of contiguous or dangerous contact farms where culling has occurred
are counted which at a conservative estimate ( MAFF had not made these
figures available at 19/4/01) for each case,
then our epidemic (1397 plus 4488 = 6985) exceeds Taiwan (6156), placing it
as worst in this period.
Taiwan abandoned slaughter only after 3.8 million pigs had been killed by
the army, at a rate up to 200,000 per day without gaining control. Note
that the ratio of farms where culling has been applied
to cases is higher in Scotland (740 farms compared to 160 cases at 21/4/01)
and some other areas of the country where the contiguous and 3 km culls
have been vigorously pursued. Therefore my estimate of the number of farms
where culling has occurred may well be an underestimate.
Of the last 22 outbreaks in non-vaccinated animal populations, each of
those which used vaccination and stamping out were controlled (last
recorded case) by 42 days of occurence of the first case.
Of those using slaughter only, half took longer than 50 days. Eight of the
10 longest outbreaks involved attempts to slaughter -only.
Three of the attempts to use slaughter only were abandoned and vaccination
introduced. No vaccination/stamping out attempts were abandoned part way
through,perhaps becuase most vaccinating
countries are relatively poor. Aggressive eradication after vaccination has
often not been followed through to regain disease freedom, again partly for
economic reasons, since the process of
eradication is costly and has to be balanced against the value of the
export market.
The majority of outbreaks successfully controlled by stamping-out alone
have been small (less than 30 cases), only exceeded by outbreaks in Italy
(55), Scotland (over 160), England, Wales and NI
(1230 and rising), and Taiwan (6156). Therefore outbreaks where
stamping-out is applied fall into two categories, small and very large. The
distribution of outbreaks in countries practising stamping-
out alone tend to be either extremely localised (where stamping-out has
been very rapidly applied in the first day or so after disease is
identified) or widespread, such as 7 regions of Italy in 1993, 9
districts of Greece in 1994, almost the entire island of Taiwan in 1997 and
in the current situation, a wide distribution in the UK, spreading also to
Ireland, the Netherlands and France from what is
considered a point source near Newcastle. In contrast where vaccination and
stamping out is
applied outbreaks tend to remain localised. An exception is in Algeria in
1999, where the infection spread widely in the first week before
vaccination was introduced, but vaccination from the end of this first week
limited the cases to 158, all occurring within 27 days of the first case.
This emphasises the importance of contingency plans and the readiness to
apply an effective policy from the first week of an outbreak to limit its
size and spread.
Not all use of vaccination has been effective in disease control; where
modified stamping out is applied (culling only of clinically affected
animals, ie proportion of herds), and ineffective movement controls, then
outbreaks can continue to spread or recurr later.
Vaccination alone, without movement controls or stamping-out of cases,
tends to result in endemic infection.
Most countries that have used vaccination have not sought afterwards to
follow the pathway of active eradication by identification of herds
containing residual infection, so we cannot compare stamping-out versus
stamping out with vaccination in countries of similar development status or
GNP. Uruguay achieved FMD freedom without vaccination in 12 months after a
cessation of mass vaccination in cattle, and has successfully used stamping
out alone to deal with a single case in 2000.
For livestock economists it is the duration of the loss of the status of
FMD freedom that must be compared when the use of vaccination is
considered. From the foregoing, vaccination tends to limit outbreaks to
less than 6 weeks, and the time to proven freedom of infection from herds
thereafter depends on the organisation of the surveillance activities,
since a dossier of information to prove evidence of FMD absence is vital to
re-opening international trade whether vaccination - or slaughter only -is
used.
In other words after stamping-out there is no guarantee that trade restrictions will be lifted and FMD freedom regained unless the surveillance
activities, and culling of animals carrying infection, is continued after
the last case. Stamping-out also results in a prolonged period (with
economic hardship) for each farmer where livestock have been culled before
re-stocking can safely occur, compared to vaccination. How long it will
take in the UK to regain international trade is very uncertain. In the
1967-8 outbreak cases occurred when animals were re-stocked onto farms
which had been infected 3 or 4 months earlier. The tail of outbreaks using
stamping out can therefore be prolonged, and unless carrier sheep
and cattle are identified and slaughtered it is possible that these will
act as source later in the year for new outbreaks. It is therefore very likely that the EU will insist on screening sheep populations
in the UK and culling of flocks which test positive, a process that will
take many months after the last reported case of clinical FMD has been
reported. The continuation of culling after the last case is
not something that most farmers are aware of.
Given the intended review of slaughter only policy by the EU, the UK is
therefore becoming a record breaker and should the review of the
non-vaccination policy result in changes in European policy,
with its knock-on effect on the world animal health body's own
recommendations, set to make history as the last application in Europe -and
possibly worldwide - of a slaughter only policy to a large scale FMD
epidemic - but only if the current policy pursued in Brussels changes to
vaccination after this epidemic.
Keith Sumption
Centre for Tropical Veterinary Medicine, University of Edinburgh
Easter Bush, Roslin, Midlothian,EH25 9RG Scotland UK
FAX: 44-131-445-5099, tel 131-650-7969
Letters from the Netherlands.....
24th April 2001:
Dear colleagues,
From Resie I heard that you are interested in getting "FMD experiences" from the Netherlands, to "enlighten" the vacc-non-vacc discussion in the UK. I think you know that between 1952 and 1992 yearly FMD vaccinations were compulsory here, and I participated for several years in these campaigns in the early seventies, both as a student and as a locum and assistant in several vet. practices. Very much a routine job, always in January when cattle are usually indoors; farmers knew you were coming, so there was someone to help you to get the job done quickly. Hardly any stories of vaccination reactions and the like, with an inactivated vaccine not so exceptional. Pigs and sheep were never vaccinated, apparently there was no need for it, with all the cattle protected. Consumers, at that time, were maybe less "aware" and critical about their food than these days, and I cannot recall any remarks or complaints, but even now I never hear any consumer (or -organisation) complain that products from animal origin ALWAYS come from animals vaccinated for some diseases (think of all poultry vaccines!). It is simply not an issue like dioxin, Salmonella enteritidis or antibiotic residues. And, by the way, antibodies and memory cells are, in my opinion, just digestible proteins! These days I feel ashamed to be a veterinarian, who did nothing to prevent the non-vaccination policy when this was decided upon 12 years ago! All the talking about "sustainable" agriculture of the last years appears to be purely theoretical with the ongoing destruction of healthy animals! I do not know whether you received the following messages and documents already, which we were mailing around few weeks ago. Maybe you can add them to your website?
Success and best regards, Ineke Puls, DVM, Boxtel, The Netherlands.
22nd April 2000: The Dutch sister organization of The RCVS,
The KNMvD has already pledged it full support for the return to vaccinating, in
case the current attempts to Eradication appear ineffective, whereas
the Dutch Minister of Agriculture has promised to at least try to open the
vaccinating debate in Brussels.
Marcus Van Doorn MRCVS