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Det Norske Veritas

Interpretation of Rabies Risk Assessment: FinalReport

Report for Defra Report No: PP010969-1 16th May 2011

16th May 2011 Interpretation of Rabies Risk Assessment Defra

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Interptetation of Rabies RA Final Report 16-05-11.doc Reference to part of this report which may lead to misinterpretation is not permissible

Interpretation of Rabies Risk Assessment

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PP010969-1

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Summary: This report provides advice on how to interpret the results of a quantitative analysis of possible changes in the likelihood of rabies introduction to the UK. It identifies and quantifies suitable comparators to put the risk of rabies introduction into context with other risks that are experienced in the UK.

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16th May 2011

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Contents

1.0 Introduction ....................................................................................................2 1.1 Background ......................................................................................................2 1.2 Objective ..........................................................................................................2 1.3 Approach ..........................................................................................................2

2.0 The Pet Movement System ............................................................................3

3.0 The VLA Risk Assessment ............................................................................4 3.1 Key Messages..................................................................................................4 3.2 Limitations ........................................................................................................4 3.3 Probabilities......................................................................................................5 3.4 Uncertainties and Rounding .............................................................................5 3.5 Individual and Societal Risks............................................................................5

4.0 Approaches to Risk Comparison..................................................................7 4.1 Principles for Risk Comparison ........................................................................7 4.2 Perception of Rabies Risk in the UK ................................................................7 4.3 Criteria of Risk Acceptability.............................................................................8 4.4 Conversion into Fatality Risks ..........................................................................9 4.5 Conversion into Individual Risks.....................................................................10

5.0 Possible Comparators .................................................................................11 5.1 Other Rabies Risks.........................................................................................11 5.2 Other Exotic Animal Diseases ........................................................................12 5.3 Animal Bites ...................................................................................................13 5.4 Food-Borne Illnesses......................................................................................14 5.5 MRSA.............................................................................................................14 5.6 Lightning.........................................................................................................14 5.7 Road Accidents ..............................................................................................15 5.8 Air Accidents ..................................................................................................15

6.0 Conclusions..................................................................................................17

7.0 References ....................................................................................................19


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1.0 Introduction

1.1 Background

The Department for Environment Food and Rural Affairs (Defra) is considering the implications of the UK adopting the harmonised EU rules for non-commercial movement of pets, known as the EU Pet Movement Policy (EU PMP). This would replace the current quarantine laws for companion animals and the Pet Travel Scheme (PETS). This would involve some changes to the protection against rabies introduction. Defra therefore commissioned a quantitative risk assessment of the change in the likelihood of rabies introduction to the UK, which was completed by the Veterinary Laboratories Agency (VLA 2010). Defra has now commissioned Det Norske Veritas (DNV) to provide advice on how to interpret the results of the VLA study in a way that will clearly and correctly communicate it to interested parties.

1.2 Objective

The objective of the work is to identify and assess suitable comparators to put the risk of rabies introduction into context. DNV will review possible comparators and discuss their strengths and weaknesses with Defra, so as to increase the likelihood that the results will be correctly understood.

1.3 Approach

DNV first reviewed the VLA report to identify its key messages about the risk of rabies introduction. DNV and Defra then held a brief meeting on 12 April 2011 to identify possible comparators, and the additional information that would be needed to make use of them. The present document gives DNV’s review of these comparators and information gaps, and concludes with proposals for completing the comparison. In addition to DNV’s normal review process, the Draft Report has been reviewed by Professor Conrad Brunk, Professor of Philosophy at the University of Victoria, Canada, and an internationally respected commentator on the perception of risk.


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2.0 The Pet Movement System

The current system for the movement of cats and dogs into the UK divides the country of origin into three groups:

• EU Member States plus 8 ‘equivalent’ countries.

• Listed third counties, e.g. the USA and the Russian Federation.

• Unlisted third countries, i.e. all other countries.

Key elements of the current PETS/quarantine system are (in simple terms):

• Pets from EU Member States (and equivalents) and listed third countries require a rabies vaccination, a successful blood test, and then a 6-month wait before entering the UK.

• Pets from unlisted third countries must spend 6 months in quarantine, where they are vaccinated against rabies.

Key elements of the EUPMP, which may become the UK system from 2012, are:

• Pets from EU Member States (and equivalents) and listed third countries require a rabies vaccination, and then a 21-day wait before entering the UK. Compared to the current UK system, there is no requirement for a blood test, and the waiting time is reduced from 6 months to 21 days.

• Pets from unlisted third countries require a rabies vaccination, a 30-day wait, a successful blood test, and then a 3-month wait before entering the UK. Compared to the current UK system, there is no quarantine and the total waiting time is reduced from 6 months to 4 months.

Both the current PETS/quarantine system and the EUPMP apply to cats, dogs and ferrets.


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3.0 The VLA Risk Assessment

3.1 Key Messages

The key messages from the VLA risk assessment about the effects of the change from the current PETS/quarantine system to the EUPMP are:

• The annual probability of rabies introduction will increase. Assuming 100% compliance with all regulations, VLA estimates there would be a 60-fold increase in the annual probability of rabies introduction. If there were only 90% compliance with all regulations, there would be a 4-fold increase, although this is from a higher base and produces a higher overall risk. The degree of compliance has not been quantified, but it is reported that the current level of compliance is close to 100%.

• The annual probability of rabies introduction is very low and will remain very low after the change. Assuming 100% compliance, VLA estimates there would be one rabies introduction every 211 years under the EUPMP as compared with one every 13272 years under the current PETS and quarantine scheme. If there were only 90% compliance it is estimated that there would be one rabies introduction every 170 years. These are best-estimates, and VLA estimates that there is 95% confidence that the frequency of rabies introduction would be less than one rabies introduction every 147 years, even in the 90% compliance scenario.

DNV recommends that these messages should be given equal prominence, i.e. the probability will increase, but it will still be very low after the increase. Misinterpretation could result if either message is unduly emphasised.

The key question that arises from these messages is: how significant is a probability of rabies introduction of 1 in 211 years? In other words, what is the basis for describing this as “very low”? This is in fact a judgement made by DNV as a result of the present study, in which the risk has been found to be lower than other comparable risks. Suitable comparators are discussed below. The term “very low” is chosen from the following probability categories that are used by Defra (based on EFSA 2006).

Probability category Interpretation Negligible Event is so rare that it does not merit to be considered Very low Event is very rare but cannot be excluded Low Event is rare but does occur Medium Event occurs regularly High Event occurs very often Very high Event occurs almost certainly

3.2 Limitations

The VLA study could properly be described as an analysis of the “probability” of rabies introduction, and the effects on this of the change from the current PETS/quarantine system to the EUPMP. In other words, it estimates the chance that a rabies-infected animal will enter the UK.


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The true “risk” of rabies introduction should also consider the consequences, i.e. the harm that might be caused by rabies introduction. This step is particularly important when comparing with other risks. However, it was not within the scope of the VLA study.

An “assessment” of the risk should also evaluate the significance of this risk, which would convert the probabilities above into value judgements such as “high” or “low”. Although VLA describes the risk as “low”, this was not the outcome of any systematic process. The present study addresses this step.

The interpretation of the results of the VLA study is also affected by the likely degree of compliance with the regulations as noted above. Whilst this has not been quantified, the evidence suggests that the current level of compliance is high and would be expected to be higher with the simpler EUPMP. For this reason, this study has focussed on the results for 100% compliance.

3.3 Probabilities

The probability of an event such as a rabies introduction can be expressed in several different ways. In the VLA study, the results are given as annual probabilities (i.e. numbers less than 1, in which smaller numbers imply lower risks). They are also converted into occurrence intervals (i.e. numbers of years between events, in which higher numbers imply lower risks). For example, an annual probability of rabies introduction of 5 x 10-3 is one chance in 200 in each year, which is equivalent to an average of one rabies introduction every 200 years if conditions remain constant. DNV uses probabilities for calculations, but recognises that occurrence intervals may be easier to understand for selected key results.

3.4 Uncertainties and Rounding

Results from all risk assessments are uncertain. In the VLA report all risk assessment results are given together with confidence ranges on the probabilities. For example, the expectation of one rabies introduction every 211 years is supplemented by the confidence range 177 to 247 years. This means that there is a 90% chance that the true value of the occurrence interval would be between 177 and 247 years. While this is appropriate for a scientific report, the present report rounds such numbers to 200 years (except where needed for traceability), because this avoids false precision whilst also being easier to understand.

All the comparators that could be used are also uncertain. The present report rounds such numbers to 2 significant figures, because in most cases the confidence ranges are not well defined. In future work, these could be defined in more detail, but this is unlikely to help the interpretation of the results.

3.5 Individual and Societal Risks

When evaluating risks, it is important to distinguish between individual and societal risks, otherwise confusion may result. The two types are defined as follows:

• Societal risks refer to the total risk in the whole of society from a particular hazard. For example, the VLA study gives the total probability of rabies introduction resulting from all pet movements into the UK. Another societal risk would be the expected number of human rabies cases in the UK. These societal risks are typically of greatest interest to governments.


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• Individual risks refer to the risk to specific or average individuals from the hazard. Examples include the probability that an individual pet might introduce rabies, or the probability that an individual person in the UK might catch rabies. These probabilities are not given in the VLA study. However, they are very important for individuals when attempting to evaluate risks.

Because the UK population is approximately 62 million, the average individual risk (if expressed as a probability) is 62 million times lower than the total societal risk. This difference should make it easy to distinguish the two, but it also explains why confusion between them may give very misleading conclusions.


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4.0 Approaches to Risk Comparison

4.1 Principles for Risk Comparison

Comparison with other risks that are experienced in daily life is one way of evaluating the significance of the risk of rabies introduction, and is the main focus of the present study.

Because risk is a complex issue it can be difficult to compare two risks. The principle for evaluating a risk through comparison with another should be to select a comparator that is similar in all respects except its probability. This means that the comparator should have a similar exposure pattern, identical consequences and be perceived in a similar way to the risk that is being evaluated. The simple magnitude of a risk is only one among many characteristics that influence perceptions of its acceptability (e.g., familiarity, controllability, voluntariness, trust, etc.). Given such similarity, it is then appropriate to compare the probability of occurrence of the comparator with the risk under evaluation. For practical purposes, the comparator should also be well known, and stable over a long period.

In reality, it is virtually impossible to find a comparator that meets all these requirements. It is therefore appropriate to consider a range of comparators, and bear in mind the differences in exposure, consequences and perceptions that may affect whether or not they are helpful to evaluate the risk of rabies introduction.

In the present study, the most critical requirement is that the comparator should have identical consequences. It is virtually impossible to find a direct comparator for the likelihood of rabies introduction from non-commercial movement of pets, because there are no other significant sources of the introduction of rabies. Therefore, it is necessary to convert the probabilities of rabies introduction into a risk of public health impacts that have a wider range of potential comparators. This conversion is considered below.

4.2 Perception of Rabies Risk in the UK

Another factor that may need to be taken into account in presenting the results of the risk assessment is the way in which the risk of rabies is perceived by the general public. When anticipating public reaction to changes in a risk it is important to determine if there is a significant “baseline” assumption in the public mind that could be triggered by the change. If this baseline is reinforced by strong social norms, it can turn out to be the most critical factor in risk acceptance. It could be argued that the “baseline” of acceptable risk of rabies in the UK at the moment is one in which the public perception is that the UK is essentially “rabies free”, and has been for some time. If there is a general awareness in the population that the UK enjoys a risk-free status with respect to this disease that is unique in the world, and there is a certain sense of national pride in this status, this could serve as the kind of social norm that would make the “baseline” perception the most salient one in terms of the response to the very small increase in rabies risk entailed by the adoption of the EUPMP. In other words, the public perception could be that the adoption of the EUPMP compromises the uniquely “clean” status of the nation.

It is not known to what extent this “baseline” issue could influence public perception of the risk change, but Defra needs to be aware of this possibility.


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4.3 Criteria of Risk Acceptability

Risk assessments normally evaluate the significance of the estimated risks by comparing them to criteria of risk acceptability. Risk criteria are the standards that are used to translate risk estimates (e.g. 10-5 per year) into value judgements about the acceptability of risk (e.g. "tolerable risk") which can be set against other value judgements (e.g. "high economic benefits") in a decision-making process.

Risk acceptability criteria are potentially useful for the present study because they represent standards that can be used to evaluate many different risks on an accepted common basis. Unfortunately, risks are so diverse that no universally appropriate criteria exist, and Defra has no specific criteria that are applicable to the risk of rabies introduction.

Among the various widely-used sets of risk acceptability criteria, the most appropriate for the present study were established by the Health and Safety Executive (HSE 2001). These are part of a tolerability of risk framework that divides risks into three bands (Figure 1):

• “Unacceptable risks”, which are intolerable whatever benefits the activity may bring, and risk reduction measures are essential whatever their cost.

• Risks that are “Tolerable if ALARP” - where risks should be reduced until they are “as low as reasonably practicable”, after taking account of the costs and benefits of further risk reduction.

• “Broadly acceptable risks”, which are so low that they would be expected to be acceptable to most people, and no further risk reduction is needed. In this region, it may be appropriate to increase the risk in order to meet other objectives

Figure 1 Tolerability of Risk Framework (HSE 2001)

Negligible Risk

UNACCEPTABLERISK

TOLERABLE RISK IF ALARP(as low as reasonably practicable)

BROADLY ACCEPTABLE RISK

Further effort to reduce risk not normally necessary

Tolerable only if risk reduction is impractical or if its cost is grossly disproportionate to the reduction in risk achieved

Risk cannot be justified except in extraordinary circumstances

Incr

easi

ng r

isk

The criteria that separate the bands vary according to whether the exposed person is a worker involved in the risk generation (say, a veterinary worker) or a member of the public. The risks are expressed as the risk of fatality per person per year, and are summarised as:

Maximum tolerable risk for workers 10-3 per person-year Maximum tolerable risk for the public 10-4 per person-year Broadly acceptable risk 10-6 per person-year

These are criteria for “individual risks”, which are considered widely applicable because they embody a notion of equality. It has proved much more difficult to develop widely applicable


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criteria for “societal risks”, although they are often reflected in criteria that balance costs and benefits in the ALARP region.

To make use of these criteria would require the probabilities of rabies introduction to be converted into a true annual risk for the most exposed worker and member of the public.

4.4 Conversion into Fatality Risks

Both the risk acceptability criteria and risk comparison approaches would be facilitated if the results in the VLA report were expressed as risks of health impacts such as death of workers and members of the public. The approach for doing this is outlined below.

The VLA report gives the probability that a rabies-infected animal enters the UK. This might lead to a fatality if all the following circumstances occur:

• The animal develops the disease. This typically takes 1-2 months following infection, during which time the animal is not infective.

• The animal wounds one or more people. Infection is most likely through saliva entering bites or scratches, or occasionally open wounds or mucous membranes.

• The person is not protected by pre-exposure vaccination. Vaccination is effective but not widely used, and loses its effectiveness over several years.

• The person does not receive appropriate medical attention. Post-exposure treatment may include disinfection, a hyper-immune serum or post-exposure vaccination.

If symptoms develop, there is no cure and death usually occurs within days.

Analysis of these factors would allow an estimate of the probability of fatality given that a rabies-infected animal enters the UK. This would require a significant assessment in itself, but for the purpose of this report and to enable some comparisons to be made, probability values have been estimated from rabies experience in other countries.

In 2009, 872 animals with rabies or unspecified Lyssavirus were recorded in 24 of the Member States of the EU. These were mainly (79%) in wild animals, primarily foxes, but included 87 cases in pets. In the same period there was only one human fatality from rabies, which was due to an untreated fox bite (EFSA 2011). This indicates a probability of fatality from infected pets of less than 1/87 = 0.011, or perhaps as low as 1/872 = 1.1 x 10-3. Similar results are obtained for the four years 2005 through 2009 as shown below, although in 2007 the data on rabies in animals were not complete for some Member States. This indicates that there were 12 human cases with a total of 916 cases in pets for these five years, giving an overall rate of 0.013 human rabies cases per case in pet animals. A rounded value of 0.01 is used in the analysis below.

There were 18 cases of rabies in dogs imported into the European Union and Switzerland during 2001-2010 (Johnson et al 2011), but none of these infected humans. This indicates a probability less than 1/18 = 0.056. However, the value above is based on a larger set of cases and is considered more realistic.


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Summary of reported cases of classical rabies or unspecified Lyssavirus in animals in the EU Member States and human rabies cases for 2005 to 2009

2009 2008 2007 2006 2005

Total rabies cases in all animals 872 1504 365 2981 2590

Rabies cases in pets (cats and dogs) 87 136 76 353 264

Human rabies cases 1 4 3 0 4

Source EFSA (2011, 2010, 2009, 2008 & 2007)

For comparison, in 2009 the USA recorded 6690 rabid animals, including 381 pets, but only 3 human fatalities from rabies, none of which were due to pets (Blanton et al 2010). This could indicate a probability of fatality of less than 1/381 = 2.6 x 10-3, or perhaps as low as 3/6690 = 4.5 x 10-4. However, because rabies is less well known in the UK, it is prudent to use the higher value from the EU.

This means that the result from the VLA study of one rabies introduction every 211 years under the EUPMP corresponds to one fatality every 211/0.01 = 21,100 years,.

4.5 Conversion into Individual Risks

The risk estimate above of 1 fatality every 21,100 years refers to the total societal risk in the UK. The risk to individual people is much lower. The population of the UK is approximately 62 million. Therefore the estimated fatality risk from rabies introduction under the EUPMP corresponds to an annual risk of rabies for an average individual of 1/(21,100 x 62 million) = 7.6 x 10-13 per year. Given the uncertainty and possible over-estimate in the probability of fatality, this is rounded to 10-12 per year.

The risk from a rabies introduction would not be spread uniformly through the population, as it would be largest for people travelling internationally with pets. In the absence of any data, it is assumed that such people would be 10x more at risk than average. For them the individual risk of death from rabies would be 10-11 per year.

Comparing with the HSE criteria above, it is concluded that the individual risk is 100,000 times lower than would be considered broadly acceptable, even for the most exposed individuals.


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5.0 Possible Comparators

5.1 Other Rabies Risks

5.1.1 Rabies in the UK

Other sources of rabies form a good comparator because they involve the same disease with the same consequences and hence may be perceived in the same way. However, different forms of transmission may result from different types of exposure (e.g. occupational or travel-related).

Rabies is extremely rare in the UK. The last case of classical rabies acquired in the UK from an animal bite was in 1902. However, in 2002 a licensed bat handler died in Scotland from a rabies-like bat virus (HPA 2011). This is difficult to express as an average risk, but an average societal risk of 1 in 100 years would be a simple interpretation.

Most rabies cases in the UK are acquired abroad. Since 1946 there have been 24 cases in the UK, all imported (HPA 2011). This is approximately 0.4 cases per year. Increased travel may be expected to have increased the rate. However, there were 4 cases during 2001-10 (HPA 2011), which is approximately the same rate. The average individual risk is 0.4/62 million = 6.5 x 10-9 per year.

Table 1 summarises the individual and societal risks of human rabies in the UK.

Table 1 Background Rabies Risks

SOURCE INDIVIDUAL RISK (per year)

UK SOCIETAL RISK (per year)

From pets under the EUPMP 1.1 x 10-11 6.6 x 10-4

All sources acquired in the UK 1.6 x 10-10 0.01 All sources 6.5 x 10-9 0.4

From this, it is concluded that the estimated average risk of death from rabies introductions under the EUPMP is approximately 8400 times less than the current average risk of death from all sources of rabies in the UK.

5.1.2 Rabies in Other Countries

In the USA during 1981-2000, there were 42 human fatalities from rabies of which 62% were acquired from bats and 31% from dogs while overseas. This is an average of 2.1 per year. With an average population of 250 million during this period, the average individual risk is 2.1/250 million = 6.0 x 10-9 per year. More recent data identified 4 human cases, of which 3 were fatal in during Jan 2009 - July 2010 (Blanton et al 2010). With a population of 307 million, the average individual risk is 3 x (12/19) /307 million = 6.2 x 10-9 per year.

In Europe, canine rabies has been eliminated, although it still exists in uncontrolled animals in neighbouring countries. Rabies is also present in bats. The incidence of human rabies is approximately 5 per year (Bourhey et al 2005). With a population of 850 million, the average individual risk is 5/850 million = 5.9 x 10-9 per year.


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World-wide, there are estimated to be about 55,000 cases of rabies per year, mainly in developing countries (HPA 2011). With a population of 6.7 billion, the average individual risk is 55000/6.7 billion = 8.2 x 10-6 per year.

From this, it is concluded that the average risk of death from all sources of rabies in the UK is similar to the risk in the USA and Europe as a whole, and approximately 1200 times less than elsewhere in the world.

5.2 Other Exotic Animal Diseases

5.2.1 Exotic Diseases of Pets

Other exotic diseases that may be carried by pets and may affect humans could be used as comparators. There are several such diseases, which may form useful comparators for Defra. However, none are as well known as rabies, and so they are unlikely to be very helpful for the public in interpreting risk.

A qualitative risk assessment (Taylor et al 2006) identified the following as the 5 most “high risk” diseases: echinococcosis, babesiosis, dirofilariosis, leishmaniosis and ehrlichiosis. Two of these are identified as pathogenic to humans: echinococcosis and ehrlichiosis. No quantitative risk estimates are available at present.

5.2.2 BSE

Bovine spongiform encephalopathy (BSE) is considered as a comparator because it is well known, and pathogenic to humans in the form of variant Creutzfeldt-Jakob Disease (vCJD), which is invariably fatal and hence arouses a high level of concern, which has some similarity to rabies. However, the risks of vCJD have changed substantially as a result of control measures introduced since the BSE epidemic of 1996, and therefore it may be misleading as a comparator. The strong opinions about BSE/vCJD may also serve to confuse any attempt to use it to clarify rabies risks.

There were 170 deaths from vCJD in the UK during 1995-2010, but the rate has declined from a peak of 28 in 2000 to 3 in 2010 (NCJDRSU 2011). With a population of 62 million, the average individual risk could be expressed as 3/62 million = 4.8 x 10-8 per year. Since most current cases resulted from exposure during the 1990s, which remains undetectable, this may be interpreted as the average individual risk of developing the disease from earlier exposure.

From this, it is concluded that the estimated risk of death from rabies introductions under the EUPMP is approximately 60,000 times less than the current average risk of death from vCJD.

5.2.3 Exotic Diseases of Livestock

Other exotic diseases that may be carried by livestock could be used as comparators. There are several such diseases, which are relatively well known although, like rabies, they are rare in the UK. However, their exposure and consequence patterns are very different, and in particular they do not normally infect humans. Therefore they may not be very helpful to compare with fatality risks from rabies.

A quantitative risk assessment (Gosling et al 2010) estimated the occurrence intervals for the diseases shown in Table 2. It also included probabilities that the outbreaks are major, which


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may be likened to the probability of a fatality from a rabies introduction. The table shows the median and 90% confidence range for each parameter.

Table 2 Occurrence Intervals for Exotic Diseases of Livestock

Disease Main species affected Average interval between outbreaks

% probability that outbreak is major

1 2 Avian influenza Poultry (0.43,2.5) (1.5,2.7)

1 2 Bluetongue Sheep, goats, cattle (0.38,5.1) (0.56,6.3)

3 2 Newcastle disease Poultry (0.97,9.8) (0.54,6.3)

10 75 Classical swine fever Pigs (6.1,16) (39,95)

25 5 Foot-and-mouth disease Cattle, sheep, pigs (10,59) (2.3,7.9)

20 95 African swine fever Pigs (8.6,50) (76,100)

25 50 Swine vesicular disease Pigs (10,59) (15,80)

50 75 African horse sickness Horses (18,126) (38,95)

From this, it is concluded that the estimated probability of rabies introduction under the EUPMP is approximately 8 times less than the probability of introduction of foot-and-mouth disease and 200 times less than the probability of introduction of avian influenza.

5.3 Animal Bites

Animal bites are relatively common, and may be a useful comparator since rabies infections will be a subset of them.

Most animal bites are from dogs. The rate of dog bites is estimated as 740 per 100,000 people (Morgan & Palmer 2007). There are estimated to be 250,000 cases who attend minor injuries or emergency units, and 2.6 per 100,000 need hospital admission. UK mortality is uncertain, but in the USA it is estimated as 7.1 per 100 million people (Morgan & Palmer 2007). These figures are summarised as individual and societal risks in Table 3.

Table 3 Dog Bite Risks

CONSEQUENCE INDIVIDUAL RISK (per year)


All cases 7.4 x 10-3 460,000 Emergency treatment 4.0 x 10-3 250,000 Hospital admission 2.6 x 10-5 1,600 Fatality 7.1 x 10-8 4

Hence the estimated risk of death from rabies is approximately 90,000 times less than the total risk of death from dog bites.


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5.4 Food-Borne Illnesses

Food-borne illness may be a useful comparator because, as with rabies from pets, it involves an extreme case of a type of exposure that is common and does not normally arouse concern.

Including all cases of food-borne illness caused by bacteria, viruses, parasites and other ‘unknown’ agents, annual estimates for food-borne illness in the UK are about one million cases, 20,000 hospital admissions and 500 deaths each year (FSA 2010). These figures are summarised as individual and societal risks in Table 4, based on the current UK population of 62 million.

Table 4 Food-Borne Illness Risks



All cases 1.6 x 10-2 1,000,000 Hospital admission 3.2 x 10-4 20,000 Fatality 8.1 x 10-6 500

From this, it is concluded that the estimated risk of death from rabies introductions under the EUPMP is approximately 11 million times less than the current average risk of death from food-borne illness.

5.5 MRSA

Meticillin-resistant Staphylococcus aureus (MRSA) is a common skin bacterium that is resistant to some antibiotics. MRSA mainly affects older people with existing illnesses, and hence is quite different from rabies, so it may not be a very useful comparator.

There were 781 deaths in the UK in 2009 in which the death certificate mentioned MRSA, which has reduced from 1600 in 2006 (ONS 2011). With a population of 62 million, the average individual risk could be expressed as 781/62 million = 1.3 x 10-5 per year.

From this, it is concluded that the estimated risk of death from rabies introductions under the EUPMP is approximately 16 million times less than the current average risk of death from MRSA.

5.6 Lightning

Death from lightning is a useful comparator for many risks because it is an unlikely event that is readily-understood, with widespread exposure and no strong perception issues.

Average societal risks in the UK during 1993-99 were 49 people per year struck by lightning including 3 people per year killed (Elsom 2001). These figures are summarised as individual and societal risks in Table 5, based on the UK population at the time of 58.2 million.


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Table 5 Risks from Lightning



Struck by lightning 8.4 x 10-7 49 Fatality 5.2 x 10-8 3

From this, it is concluded that the estimated risk of death from rabies introductions under the EUPMP is approximately 70,000 times less than the current average risk of death from being struck by lightning.

5.7 Road Accidents

Death from road accidents is a useful comparator for many risks because it is one of the most common accidental causes of death. However, the exposure to risk on the road varies widely (e.g. between professional drivers and non-drivers), and the perception of risk from drivers is affected by their perception of having a high degree of control over the risks. It may be expected that a more useful comparison would be the risk to pedestrians, although their exposure is also variable and they also have a significant degree of control over their risks (e.g. deciding how and where to cross the road).

Average societal risks in Great Britain in 2009 were 2,222 people killed in road accidents, including 500 pedestrian deaths (DfT 2010). The pedestrian casualties are summarised as individual and societal risks in Table 6, based on the GB population of 60 million.

Table 6 Risks to Pedestrians from Road Accidents


GB SOCIETAL RISK (per year)

All casualties 4.5 x 10-4 26,887 Fatal or serious injury 1.0 x 10-4 6,045 Fatality 8.3 x 10-6 500

From this, it is concluded that the estimated risk of death from rabies introductions under the EUPMP is approximately 11 million times less than the current average risk of death from being struck by a road vehicle.

5.8 Air Accidents

Death from accidents during air travel may be a useful comparator because it is well-known and, like rabies, involves a high probability of death. On the other hand, the exposure is very different, since most people fly only on specific brief occasions. Unlike the other risks above, it is also difficult to isolate the risks of air travel that are connected with the UK, so world averages are commonly used, which may over-estimate the risks in the UK.

The fatal accident frequency on large Western-built commercial jet aircraft during 2000-09 was 0.46 per million flights (Boeing 2010). DNV’s analysis of this data indicates an average probability of fatality for people on board in these events of 0.787. Hence the average fatality probability is 3.6 x 10-7 per flight. UK air passenger traffic is approximately 240 million per year (CAA 2008). Compared to the UK population of 62 million, this is an average of 4 flights per person per year. Hence the average fatality risk is 1.4 x 10-6 per year.


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From this, it is concluded that the estimated risk of death from rabies introductions under the EUPMP is approximately 2 million times less than the current average risk of death in an aircraft accident.


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6.0 Conclusions

A short study has been carried out to aid the interpretation of the results of the quantitative risk assessment on the change in likelihood of rabies introduction into the United Kingdom as a consequence of adopting the existing harmonised European Community rules for the non-commercial movement of pet animals carried out by the VLA (VLA, 2010). The results have been compared with risk criteria and a range of risk comparators.

1. The VLA QRA study estimated the chance of a rabies-infected animal entering the UK under the EUPMP, with 100% compliance, was once in 211 years and that this represents a 60-fold increase from the present UK PETS/quarantine system.

2. This is approximately 8 times less than the probability of introduction of foot-and-mouth disease and 200 times less than the probability of introduction of avian influenza.

3. In order to compare this risk of introduction of rabies with risk criteria and other risk comparators some additional assumptions were made to estimate the expected maximum number of human fatalities that could result from the introduction of one rabies-infected animal. One rabies introduction every 211 years was estimated to be equivalent to one human fatality every 21,000 years. This is estimated to be equivalent to an individual risk of death in the most exposed population (those travelling with pet animals) of about 10-11 per year. This is an approximate estimate, and it would be desirable to improve it, although this is not likely to significantly affect the conclusions below.

4. Comparison of this risk with the HSE individual risk criteria indicate that the risk of death from rabies introduction under the EUPMP is some 100,000 times lower than would be considered broadly acceptable, even for the most exposed individuals;

5. Comparisons with other risks indicate that the estimated average risk of death from rabies introduction under the EUPMP is:

a. approximately 8400 times less than the current average risk of death from all sources of rabies in the UK;

b. approximately 60,000 times less than the current average risk of death from vCJD;

c. approximately 90,000 times less than the total risk of death from dog bites;

d. approximately 11 million times less than the current average risk of death from food-borne illness;

e. approximately 16 million times less than the current average risk of death from MRSA;

f. approximately 70,000 times less than the current average risk of death from being struck by lightning;

g. approximately 11 million times less than the current average risk of death from being struck by a road vehicle;


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h. approximately 2 million times less than the current average risk of death in an aircraft accident.

6. This range of risk comparisons presents a consistent picture, so that it is reasonable to conclude that the risk to the UK population resulting from the introduction of rabies infected animals under the EUPMP remains very low.

7. The strong public perception of the UK having a special “rabies free” status could mean that there is a greater resistance to change than might otherwise be expected, as the adoption of the EUPMP could be seen to compromise the uniquely “clean” status of the nation. This possibility needs to be taken into account in presenting the results.


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7.0 References

Blanton, J.D., Palmer, D. & Rupprecht, C.E. (2010), “Rabies Surveillance in the United States during 2009”, J Am Vet Med Assoc, vol 237, no 6, 15 September 2010.

Boeing (2010), “Statistical Summary of Commercial Jet Airplane Accidents, Worldwide Operations, 1959-2009”, Boeing Commercial Airplane Group, July 2010.

Bourhy, H., Dacheux, L., Strady, C. & Mailles, A. (2005), “Rabies in Europe in 2005”, Eurosurveillance, vol 10, no 11, 1 November 2005.

CAA (2008), “Recent Trends in Growth of UK Air Passenger Demand”< Civil Aviation Authority, January 2008.

Elsom, D.M. (2001), “Deaths and Injuries Caused by Lightning in the United Kingdom: Analyses of Two Databases”, Atmospheric Research, vol 56, no 1-4, January 2001.

EFSA (2006), “Scientific Statement on Migratory Birds and Their Possible Role in the Spread of Highly Pathogenic Avian Influenza”, European Food Safety Authority EFSA-Q-2005-243, adopted 4 April 2006.

EFSA (2011), “The European Union Summary Report on Trends and Sources of Zoonoses, Zoonotic Agents and Food-Borne Outbreaks in 2009”, EFSA Journal 2011; 9(3):2090.

EFSA (2010), “The Community Summary Report: Trends and Sources of Zoonoses, Zoonotic Agents and Food-Borne Outbreaks in 2008”, EFSA Journal 2018; 8(1):1496.

EFSA (2009), “The Community Summary Report: Trends and Sources of Zoonoses, Zoonotic Agents in the European Union in 2007”, EFSA Journal (2009), 223.

EFSA (2008), “The Community Summary Report on Trends and Sources of Zoonoses, Zoonotic Agents, Antimicrobial resistance and Food-Borne Outbreaks in the European Union in 2006”, EFSA Journal (2007), 130.

EFSA (2007), “The Community Summary Report on Trends and Sources of Zoonoses, Zoonotic Agents, Antimicrobial resistance and Food-Borne Outbreaks in the European Union in 2005”, EFSA Journal (2006), 94.

FSA (2010), “Annual Report of the Chief Scientist 2009/10”, Food Standards Agency, September 2010

Gosling, J.P., Hart, A., Mouat, D., Sabirovic, M., & Simmons, A. (2010), “Quantifying uncertainty about the cost of exotic diseases using expert elicitation”. Technical report, The Food and Environment Research Agency. Submitted to Risk Analysis.

HPA (2011), “Rabies: Frequently Asked Questions”, Health Protection Agency, http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/Rabies/GeneralInformation/ClassicalRabiesFAQs/ (Accessed April 2011)

HSE (2001), “Reducing Risks, Protecting People – HSE’s Decision-Making Process”, Health & Safety Executive, HSE Books.


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Johnson, N. et al (2011), “Imported Rabies, European Union and Switzerland, 2001-2010”, Emerging Infectious Diseases, vol 17, no 4, April 2011.

NCJDRSU (2011), “CJD Statistics”, National Creutzfeldt-Jakob Disease Research & Surveillance Unit ,http://www.cjd.ed.ac.uk/figures.htm (Accessed April 2011)

Morgan & Palmer (2007), “Dog Bites”, BMJ, 334(7590): 413–417, 24 February 2007.

Taylor, M.A. et al (2006), “Qualitative Veterinary Risk Assessment: Introduction of Exotic Diseases (other than Rabies) in the UK”, Veterinary Surveillance Team Report, 3 August 2006.

VLA (2010), “A Quantitative Risk Assessment on the Change in Likelihood of Rabies Introduction into the United Kingdom as a Consequence of Adopting the Existing Harmonised Community Rules for the Non-Commercial Movement of Pet Animals”, Veterinary Laboratories Agency, 31 August 2010.

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