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BLUETONGUE - EUROPE (09): BTV-8, IMPACT, VACCINATION
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A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases
<http://www.isid.org>
[1]
Date: Tue 19 Feb 2008
Source: Warmwell.com, quoting The Veterinary Record, 16 Feb 2008,
Letters [edited]
<http://www.warmwell.com/08feb18blayney.html>
Coordinating the approach to bluetongue
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Sir, The arrival of bluetongue virus (BTV) on these shores presents a
new disease challenge to veterinary surgeons and their clients.
The profession is naturally keen to learn what is being planned; with
that in mind, I am pleased to present the current state of play.
Government has engaged with various stakeholder groups in order to
develop the necessary strategy to deal with this disease. Veterinary
colleagues are involved in every area. A plan is close to completion,
at which point it must be presented to the European Commission for agreement.
It is likely, for a whole host of reasons, that the vaccination
strategy will be on a voluntary basis, although discussions with
regard to any financial assistance available from the European
Veterinary Fund continue.
Government is to be commended for underwriting an order of 22.5
million doses of BTV serotype 8 vaccine; the challenge facing the
stakeholder groups is how best to advise on its usage, and there are
several issues to be addressed. Under EU rules, vaccine may only be
administered in a BTV protection zone and not in the surveillance
zone. DEFRA has the authority to modify zones as it thinks
appropriate. Vaccine will be delivered as it is manufactured and released.
An adequate level of uptake is required to achieve significant
(national) herd immunity if the vaccination strategy is going to be
successful. Vaccine must be administered swiftly, such that levels of
immunity precede the further spread of the virus when the midge
population becomes active and temperatures are sufficiently high for
virus transmission to occur.
The role of the veterinary profession in addressing this disease
challenge is significant.
The vaccine will be licensed as a POM-V, to be administered to
animals under the care of a veterinary surgeon. It is likely that our
clients will be permitted to vaccinate their own animals, although
arrangements with regard to movement between zones or states (or
devolved national boundaries) may require veterinary certification.
The profession has the opportunity to demonstrate yet again the value
of a viable livestock veterinary sector to the nation. We must
persuade our clients of the necessity of mass vaccination and our
target must be 100 percent -- including all hobby farmers and keepers
of more exotic susceptible species. The local veterinary practice is
likely to be the first point of inquiry and has the opportunity to
influence the uptake of vaccine and the likely success of the
campaign; other industry stakeholders will also be working to spread
the necessary messages.
The pattern of disease that has been witnessed in northern Europe
leaves us in no doubt as to the gravity of the situation.
Anecdotally, it appears that the lamb crop in areas of northern
Europe may well be down by 30 percent. Cattle production has been
similarly adversely affected. Our fragile farming industry cannot
afford this. We are in a slightly better position in the UK since we
do have the opportunity to prevent or at least ameliorate the
development of the so-called phase 2, where the amount of virus
circulating in the midge population is sufficiently high to cause
high morbidity and mortality.
It is the aim of the BVA to keep its members apprised of developments
via The Veterinary Record and also the BVA website, which members may
wish to check for developments and further guidance from the BVA
Bluetongue Group. Please ensure that the BVA has your current e-mail
address in order to receive notification of developments, and sign up
to BVA e-news on
<http://www.bva.co.uk>.
[Byline: Nick Blayney, President, BVA,
7 Mansfield Street, London W1G 9NQ]
--
Communicated by:
ProMED-mail Rapporteur Mary Marshall
[The statement that only "anecdotal" information is available on the
effect of BTV-8 upon the production of cattle and sheep in Europe
illuminates the clear need for updated, scientifically based
information on the BTV-8 epizootic, which has already spread to 9
European countries. The following -- most recent available -- paper
is included to somewhat decrease the knowledge gap. - Mod.AS]
******
[2]
Date: Tue 19 Feb 2008
Source: The Veterinary Record, 20 Oct 2007, Letters (pages 571-572) [edited]
<http://veterinaryrecord.bvapublications.com/cgi/content/full/161/16/571-e>
(subscription required)
Mortality and case fatality during the recurrence of BTV-8 in
northern Europe in 2007
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SIR, Before 2006, the distribution of bluetongue virus (BTV) in
Europe was limited to south and south-east Europe. In July 2006, an
outbreak of BTV serotype 8 (BTV-8) affected more than 2000 holdings
across northern Europe (EFSA 2007). In April 2007, BTV-8 reappeared
(International Society for Infectious Diseases 2007a), and has since
spread rapidly, reaching the UK in September 2007. While there have
been suggestions that the severity of clinical signs in sheep and
cattle has increased in 2007 (International Society for Infectious
Diseases 2007b, c), no detailed analyses have been published
supporting such observations.
Under Article 1.1.2.3 of the World Organisation for Animal Health
(OIE) Terrestrial Animal Health Code (OIE 2007), countries affected
by a notifiable disease are required to submit regular reports to the
OIE. These reports are publicly available through the World Animal
Health Information Database.
The reports include the numbers of susceptible animals, cases (i.e.,
animals showing clinical or serological evidence of BTV infection)
and dead animals for each holding, and are the most accurate data
generally available for most of the affected countries, except the
Netherlands, where only the 1st outbreak of 2007 has been reported so far.
Using the reports from Belgium, Germany, France and Luxembourg
between 6 Jul 2007 (1st reported case in a non-sentinel herd) and 31
Aug 2007 (last report at the time of writing), we estimated mortality
and case fatality in sheep and cattle, with 95 percent confidence intervals.
"Mortality" was defined as the probability of a susceptible animal on
an affected holding dying from bluetongue, and "case fatality" as the
probability of a case dying from the disease (Thrusfield 1995).
The mortality and case fatality varied between species and countries
(Table 1*).
Our analysis shows that the severity of the bluetongue epidemic has
not increased dramatically from last year [2007], with an average
observed mortality of less than 0.2 percent in cattle and less than 3
percent in sheep, compared with reports of 0.1 percent and 3 percent
mortality for cattle and sheep respectively in 2006 (Elbers and
others 2007). In contrast, case fatality has increased considerably
in sheep, from 18 percent to 37.5 percent, but is more moderate in
cattle with less than 5 percent of animals dying of the disease
(lower than the 9 percent reported last year). Estimates are similar
in Germany, Belgium and Luxembourg, but very different in France,
where no deaths have been reported despite a total of 134 cases, some
only identified by serology.
The apparent increase in case fatality in sheep in 2007 could be
attributable to a change in the virus since 2006 or an increase in
concurrent non-BTV-related infections. Because mortality remains
similar, the results could also indicate a reduction in the level of
clinical cases actually reported, possibly due to refined case
definitions or the overwhelming workload of local veterinary
officers. This work indicates the need for epidemiological claims to
be based on transparent datasets, as well as for international
standardisation of case definitions and for data collection and
sharing via organisations such as the OIE.
*TABLE 1:
Estimates and 95 percent confidence intervals (CIs) for mortality and
case fatality due to bluetongue in each country and species
Country/ Species/ Mortality (percent) (95percent CI)/ Case fatality
(percent) (95percent CI)
1. Belgium/ Cattle/ 0.18 (0.11-0.28)/ 4.97 (3-7.62)
Belgium/ Sheep/ 2.42 (2.13-3.74)/ 30.08 (26.94-33.34)
2. France/ Cattle/ 0 (0-0.01)/ 0 (0-1.25)
France/ Sheep/ 0 (0-1.49)/ 0 (0-8.36)
3. Germany/ Cattle/ 0.0493 (0.02-0.1)/ 2.93 (1.27-5.59)
Germany/ Sheep/ 1.45 (1.15-1.80)/ 36.41 (30.03-43.12)
4. Luxembourg/ Cattle/ 0.04 (0-0.18)/ 0.0345 (0.2-14.32)
Luxembourg/ Sheep/ 1.14 (0.28-2.93)/ 37.50 (10.96-70.97)
References
- EFSA (2007) Bluetongue Serotype 8 Epidemic Bulletin. Bulletin 15.
. Accessed 15 Oct 2007
- ELBERS, A. R. W., MINTIENS, K., STAUBACH, C., GERBIER, G.,
MEISWINKEL, R., HENDRICKX,G., BACKX, A., CONRATHS, F. J., MEROC, E.,
DUCHEYNE, E., GETHMANN, J., HEESTERBEEK, J. A. P., DE CLERQ, K.,
UNGER, F. & STEGEMAN, J. A. (2007) Bluetongue virus serotype 8
epidemic in north-western Europe in 2006: preliminary findings.
Proceedings of the Society for Veterinary Epidemiology and Preventive
Medicine. Eds D. J. Mellor, J. R. Newton.
- Dipoli, Finland, March 28 to 30, 2007. p 304
- INTERNATIONAL SOCIETY FOR INFECTIOUS DISEASES (2007a) ProMED-mail
archive number: 20070713.2250. . Accessed 13 Jul 2007
- INTERNATIONAL SOCIETY FOR INFECTIOUS DISEASES (2007b) ProMED-mail
archive number: 20070828.2817. . Accessed 28 Aug 2007
- INTERNATIONAL SOCIETY FOR INFECTIOUS DISEASES (2007c) ProMED-mail
archive number: 20070902.2891. . Accessed 2 Sep 2007
- OIE (2007) Terrestrial Animal Health Code.
. Accessed 15 Oct 2007
- THRUSFIELD, M. V. (1995) Veterinary Epidemiology. 2nd edn. Oxford,
Blackwell Science
--
Contributed by:
C. Szmaragd, A. Wilson, S. Carpenter, P. P. C. Mertens, P. S. Mellor,
S. Gubbins
Institute for Animal Health
Pirbright Laboratory
Ash Road
Pirbright, Surrey GU24 0NF
[The scarcity of published observations and indeed scientific papers
related to the BTV-8 epizootic in Western Europe is manifested by the
following list of 4 most recent papers available on the PubMed
website. They are:
1. Elbers AR, Backx A, Ekker HM, van der Spek AN, van Rijn PA.
Performance of clinical signs to detect bluetongue virus serotype 8
outbreaks in cattle and sheep during the 2006-epidemic in The
Netherlands. Vet Microbiol. 17 Nov 2007.
2. Batten CA, Bachanek-Bankowska K, Bin-Tarif A, Kgosana L, Swain
AJ, Corteyn M, Darpel K, Mellor PS, Elliott HG, Oura CA. Bluetongue
virus: European Community inter-laboratory comparison tests to
evaluate ELISA and RT-PCR detection methods.
Vet Microbiol. 17 Nov 2007.
3. Szmaragd C, Wilson A, Carpenter S, Mertens PP, Mellor PS, Gubbins
S. Mortality and case fatality during the recurrence of BTV-8 in
northern Europe in 2007.
Vet Rec. 20 Oct 2007; 161(16):571-2. [This letter to editors, which
is included in item 2 above, is in fact the only available paper
dealing with the 2007 outbreak; it appeared before the introduction
of the disease into England, Denmark and Switzerland.]
4. Darpel KE, Batten CA, Veronesi E, Shaw AE, Anthony S,
Bachanek-Bankowska K, Kgosana L, bin-Tarif A, Carpenter S,
Muller-Doblies UU, Takamatsu HH, Mellor PS, Mertens PP, Oura CA.
Clinical signs and pathology shown by British sheep and cattle
infected with bluetongue virus serotype 8 derived from the 2006
outbreak in northern Europe. Vet Rec. 25 Aug 2007; 161(8):253-61.
To address the need for updated data on the clinical aspects and
epidemiology of BTV-8 and on its short- and long-term economic and
animal-welfare implications, and in view of the concern that other
vector-borne viruses will follow, ProMED-mail will appreciate
receiving relevant, original data collected by clinicians and others
in large and small ruminants, from all affected countries.
One cannot escape comparing the rate of attention (and number of
papers) relating to the BTV-8 2006-2007 epizootic in Europe, to those
which accompanied the West Nile virus introduction into and spread
within the USA in 1999-2001. Clearly, the zoonotic aspect of WNV
rendered this virus its high ranking public attention. However, the
low rate of attention (and research effort) paid in Europe to the
BTV-8 epizootic, already identified in 8 industrialised, western
European countries, seems to reflect the decreased public interest in
agriculture in general and in non-zoonotic animal diseases in
particular. Most unfortunate to Europe's farmers. - Mod.AS]
[see also:
Bluetongue - Europe (08): BTV-8, UK ex Netherlands, serology 20080217.0637
Bluetongue - Europe (07): BTV-8, UK (England), France 20080214.0589
Bluetongue - Europe (06): BTV-8, UK (England) 20080209.0522
Bluetongue - Europe (03): BTV-8, Spain, OIE 20080119.0233
Bluetongue - Europe (02): BTV-8, vaccination 20080118.0231
Bluetongue - Europe: BTV-8, vaccination, vector-free period 20080117.0215
2007
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Bluetongue - Europe (67): BTV-8, vector-free period 20071230.4185
Bluetongue - Europe (66): BTV-8, UK (Scotland) ex Germany 20071229.4167
Bluetongue - Europe (65): BTV-8, update, UK 20071222.4118
Bluetongue - Europe (64): BTV-8, research, UK ex Germany 20071219.4080
2006
----
Bluetongue - Europe (14): new vector 20061024.3042
Bluetongue - Europe (11): vector 20061016.2978]
....................arn/ejp/mpp
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