ROYAL SOCIETY INQUIRY INTO INFECTIOUS DISEASES OF LIVESTOCK

Response from Institute for Animal Health (IAH) to call for detailed evidence

It is suggested that the priority exotic viral diseases which should be addressed by the Committee are those shown in Table 1. Emerging diseases should also be considered e.g. Nipah.

This document focuses primarily on foot-and-mouth disease (FMD) but the principles can equally well be applied to other diseases. The main features of bluetongue and African horse sickness, virus diseases transmitted by biting midges, are presented separately in Annex 1.

Table 1. The major livestock diseases of importance to the UK.

Disease	Present in EU	Risk for the UK	Vaccine available	Potential cost/harm	IAH research effort
Foot-and-mouth disease	S^1	M	Y	H	H
Swine vesicular disease	Y^2	M	N	L	L
Classical swine fever	Y	H	Y	M	L^3
African swine fever	Y^4	L	N	M	M
Bluetongue	Y^5	L^11	Y^9	M	L
African horse sickness	N	L^11	Y	L	L
Sheep & goatpox	S^6	L	Y	M	L
Avian influenza	S	M	Y	M	L
Newcastle disease	S	M	Y	M	-
Peste des petits ruminants	N^7	L	Y	M	L
Rabies	Y	L	Y	L^10	-^3
West Nile Fever	Y^8	M	N	L^10	-

¹Key: Y = yes M = medium

N = no H = high

S = sporadic L = low

² present in Italy only

³ most of the UKs research effort is at the VLA, Weybridge

⁴present in Sardinia only

⁵Greece, Spain, France and Italy

⁶sporadic in Greece

⁷present in Asiatic Turkey

⁸present in France

⁹attenuated vaccine available but not considered safe

¹⁰a zoonotic disease so important public health considerations

¹¹ low at present but will increase with global warming

7 Almost all of the diseases listed above are classified by the Office International des Ipizooties (OIE; world Organisation for Animal Health) as List A diseases.

7 By definition they have the potential for rapid and extensive spread, are likely to have serious socio-economic or public health consequence and are of major importance in the international trade of animals and animal products.

7 The UK does not vaccinate against any of these diseases and so its livestock population is fully susceptible. Any incursion would have devastating economic consequences on the industry as evidenced by the 2001 epidemic of FMD in the UK and by the 19978 epidemic of CSF centred on The Netherlands. Several of these diseases, e.g. classical swine fever (CSF), swine vesicular disease (SVD), African swine fever (ASF) and bluetongue (BT) are present in the EU. Others, e.g. foot-and-mouth disease (FMD), sheep and goat pox (SGP) and Newcastle disease (ND) occur sporadically and are mostly confined to the EUs borders with eastern and central Europe. Greece is the EU member state most often affected and outbreaks of FMD and SGP there have been attributed to the illegal movement of infected sheep or goats from Asiatic Turkey where those diseases are endemic. Other exotic viruses, including peste des petits ruminants (PPR) virus and ephemeral fever virus have also been isolated in Asiatic Turkey, increasing the risk that they might be introduced into the EU at any time.

7 The risk of entry of an exotic virus into the UK has increased during recent years. The demise of the Iron Curtain has created opportunities for animals and their products to be transported from central to western Europe. At the same time, the formation of the single market within the EU has facilitated movement across the member states. Illegal trade has also increased, with smugglers being attracted by the prospect of higher profits. The increase in travel, particularly to and from far-distant countries, is increasing the chances of importation of virus in products brought from those countries where the viruses are endemic. Global warming is likely to increase the northerly distribution of the insect vectors of bluetongue, African horse sickness and West Nile Fever virus and the risk for the UK of those diseases (see Annex 1).

2 DISEASE FREE STATUS

2.1 Should the country abandon the disease free concept?

No. FMDV causes severe suffering in UK breeds of cattle and pigs and long-term loss of yield. Although mortality in FMD is generally low, severe losses have been reported among young animals in epidemics outside the UK with mortality levels between 50% and 90%. Not controlling the disease is therefore not an option. Moreover, the virus is so infectious that there can only be one rational objective when dealing with an outbreak: eradication. Therefore, the UK cannot abandon the "disease-free concept" in its wider sense.

2.2 Is it realistic to maintain the disease free status?

Yes. This answer anticipates much of the evidence to come in later sections, but a powerful case for maintaining disease-free status can be made simply by looking at the successful record of the policy. Essentially the argument is as follows:

The only way to demonstrate convincingly that livestock are free of FMDV is for animals to be, not just healthy, but also susceptible (see 5.10). For this reason, disease-free status, according to OIE criteria which this Institute supports, is incompatible with the presence of anti-FMDV antibodies in livestock. This means that a country cannot both vaccinate and be accredited virus-free at the same time. It is unlikely that this rule will be relaxed until science has provided the means to prevent or reliably detect the carrier state (see 5.10).

In the light of this the above question can be rephrased: Will it be practicable for the UK to control FMD without relying on permanent vaccine cover? Many factors limit the usefulness of current vaccines (see 5.3), in addition to their inability to confer sterile immunity (5.3(i)). The need for permanent vaccine cover should be assessed in the light of those factors and of the record of vaccine-free control policies in the UK, and globally.

How have the non-vaccine-using countries fared over the past ten years?

Fifty eight nations world-wide either qualify currently for disease-free status or, like the UK, have been traditionally disease-free. These countries include the whole of the developed world. Over the past decade since continental Europe ceased routine vaccination, there have been a total of 13 virus introductions from outside this group of 58 countries and a further four cross-infections between members of the group. Most outbreaks were restricted to a small number of cases per country (in Europe the median = 12), with just four very large-scale epidemics of over 1,000 cases (Taiwan 1997, Uruguay 2000, Argentina 2001, UK 2001) recorded over the period. According to that record, a country can expect to be infected on average once every 34 years and to suffer a really serious epidemic once in almost two centuries. Most, at least, of the traditionally disease-free countries will view a strategy delivering that level of control as cost-effective, and are unlikely to abandon it collectively on either a global or regional basis, at least under present circumstances.

As for the UKs own history, it is noteworthy that the two worst epidemics on record, 1967/68 and 2001, were almost certainly associated with the importation of contaminated animal products. This is FMDVs classic mode of intercontinental travel (e.g. Durban 2000) and it is preventable by cheaper and more effective measures than routine, mass vaccination. In any case, the UK has little room for unilateral action. This is not to prejudge the usefulness of vaccination as a temporary adjunct to other eradication measures, but it can not make sense for a major trading nation like the UK, with geographical advantages of insularity and remoteness from endemic areas, to put her livestock industry at a perpetual disadvantage by abandoning accreditation unilaterally.

In summary, we do not judge the aim of maintaining disease-free status to be unrealistic. Rather the reverse.