Research and analysis

Risk assessment on the importation of ovine and caprine unpasteurised milk and dairy products from Spain to Great Britain during a sheep pox and goat pox outbreak

Published 26 January 2024

Date of risk assessment: 11 November 2022

This document was authored by Dr Catherine McCarthy and Dr Alex Royden on behalf of the UK Office for Sanitary and Phytosanitary Trade Assurance, Defra. Expert opinion and peer review were provided by the Animal and Plant Health Agency (APHA) and Defra.

Executive summary 

Sheep pox and goat pox (SPGP) was confirmed at a premises in Andalucía, Spain, on 18 September 2022. This is the first case in Spain since 1968 and is the first confirmation of the disease in the European Union (EU) and geographical Europe (excluding Turkey) since 2018. There is a substantial degree of uncertainty around the spread outside of these regions, as well as the date and source of infection.  

This veterinary risk assessment provides a qualitative assessment of the risk of a sheep or a goat in Great Britain (England, Scotland and Wales) becoming infected with SPGP virus from the legal importation of a single consignment of unpasteurised milk or dairy products from sheep or goats in Spain. 

This risk assessment assumes the reasonable worst-case scenario where an infected but undetected farm exports unpasteurised milk or dairy products to Great Britain. A particular concern is that artisan producers may travel to Great Britain to sell unpasteurised dairy products at cheese fairs or gatherings.

The likelihood of a sheep or goat in Great Britain being infected with the Sheep Pox and Goat Pox virus from the importation of a single consignment containing unpasteurised ovine or caprine milk or dairy products from an infected and undetected flock in Spain is assessed as Very Low (High uncertainty).

The likelihood of infection through a single consignment of the following is assessed as very low:^{[footnote 1]} 

• unpasteurised milk 
• dairy products  
• packaging 
• workers’ clothing or shoes   

As this assessment considers the risk from a single consignment, the overall risk to Great Britain would be aggregated by the volume of trade from Spain. Trade volumes are out of scope of this assessment due to uncertainty in the data. However, trade volumes should be considered when interpreting the overall result and risk to Great Britain. Other forms of transmission, such as imports of live animals, wool or untreated hides, personal imports, and illegal trade, are not in scope of this risk assessment. 

The largest sources of uncertainty relate to mechanical transmission of the virus through insect vectors and the rate of littering of milk and dairy products in areas of Great Britain where sheep and goats may graze. 

Further risk mitigation options could include: 

• tighter controls on imports from the EU  
• implementing biosecurity measures at cheese fairs 
• enhanced communication with members of the public on the importance of not littering in the countryside 
• raising awareness that it is illegal to feed catering waste, kitchen scraps, meat and meat products to sheep and goats

Aims 

This veterinary risk assessment provides a qualitative assessment of the risk of a sheep or a goat in Great Britain becoming infected with SPGP virus from the legal importation of a single consignment of unpasteurised milk or dairy products from sheep or goats in Spain.  

The specific risk is that the importation of unpasteurised milk and dairy products, their packaging, and fomites, for example people, vehicles, and equipment, contaminated with SPGP virus could cause outbreaks of disease in the susceptible sheep and goat population in Great Britain. A particular concern is that artisan producers may travel to Great Britain to sell unpasteurised dairy products at cheese fairs or gatherings.  

Other routes of transmission, such as imports of live animals, wool or untreated hides, personal imports, and illegal trade, are outside of the scope of this risk assessment. This assessment does not consider further spread of the virus once a sheep or goat in Great Britain becomes infected. The results of this assessment will be used to inform decisions on restrictions of milk and dairy products from affected regions.

Risk question 

What is the likelihood of a sheep or goat in Great Britain being infected with the SPGP virus from the importation of a single consignment containing unpasteurised ovine or caprine milk or dairy products from an infected and undetected farm in Spain? 

Hazard identification 

The hazard is SPGP virus. Sheep pox and goat pox are considered as a single disease by the World Organisation for Animal Health (WOAH) and can only be differentiated through viral genome sequencing. As this has not been done in the current outbreak, it is referred to throughout this assessment as the generic term, sheep pox and goat pox (SPGP).^{[footnote 2]} 

Risk estimate: very low 

The likelihood of a sheep or goat in Great Britain being infected with SPGP through the importation of unpasteurised milk or dairy products is assessed as very low (defined as “very rare but cannot be excluded”). The likelihood of infection through unpasteurised milk, dairy products, contaminated packaging and contaminated clothing or shoes were all assessed as very low. The likelihood of infection through contaminated vehicles or equipment were assessed as negligible.

As this assessment considers the risk from a single consignment, the overall risk to Great Britain would be aggregated by the volume of trade from Spain. As trade volumes are not accurately monitored from the EU at this time, this value is highly uncertain and were out of scope in this assessment. However, trade volumes will have an impact on the overall result and risk to Great Britain of a sheep or goat in Great Britain being infected with SPGP through the import of unpasteurised milk or dairy products. 

Uncertainty: high 

There is a high level of uncertainty. The largest sources of uncertainty are mechanical transmission of the virus through insect vectors and the rate of littering of dairy products in areas of Great Britain where sheep and goats may graze.

Assumptions 

The results of this risk assessment are based on assumptions, which would increase the risk if not met.  

As in WOAH guidelines, sheep pox and goat pox cannot be differentiated serologically. The virus in the current outbreak has not yet been sequenced. Therefore, although all the cases to date have involved sheep, the term sheep pox and goat pox (SPGP) has been used throughout. This risk assessment considers the risk to both sheep and goats in Great Britain.^{[footnote 2]} 

Known infected premises (IPs) in Spain are restricted by the relevant competent authority and are not able to export unpasteurised milk and milk products to Great Britain. This risk assessment assumes the reasonable worst-case scenario where an infected but undetected farm exports unpasteurised milk or dairy products to Great Britain. 

Risk mitigations 

Various risk mitigation options could be considered to reduce the risk of a sheep or goat in Great Britain being infected with SPGP through the importation of unpasteurised milk or dairy products. These include: 

1. Placing restrictions on the import of unpasteurised milk and dairy products into Great Britain from affected countries. 
2. Enhancing biosecurity at cheese fairs and farmer gatherings with foot dips and hand washing facilities. 
3. Ensuring milk and dairy products are consumed in entirety at cheese fairs and farmer gatherings or considered as animal by-products and destroyed accordingly.  
4. Enhanced communication with members of the public on the importance of not littering in the countryside and raising awareness that it is illegal to feed catering waste, kitchen scraps, meat and meat products to sheep and goats.

Risk assessment 

Background 

This background information is specific to the current SPGP outbreak in Spain and the risk of incursion to Great Britain through contaminated unpasteurised milk and dairy products.  

The risk assessment is designed to be applicable to future outbreaks. However, specific factors related to future outbreaks should be considered before applying the findings to other outbreaks.  

Spain is the second highest producer of sheep and goat’s milk in the EU, producing 508.3 million litres of sheep milk and 468.6 million litres of goat milk in 2020 ​(Iglesias and Andres, 2022)​. Spain has a population of 1,403,850 milking goats and 2,420,000 milking sheep. Approximately 98.2% of goat milk and 92.5% of sheep milk are used for cheese production​ (Martinez, et al., 2011)​.  

SPGP was confirmed at a premises in Andalucía, Spain, on 18 September 2022. This is the first case in Spain since 1968 and is the first declaration of the disease in the EU and geographical Europe (excluding Turkey) since 2018 ​(WOAH, 2022)​. The virus is present in Africa, the Middle East, and Asia. Early reports suggest the virus in the current Spanish outbreak could be related to the strains circulating in Northern Africa ​(Martin, 2022)​.  

As of 21 October 2022, there have been 17 confirmed outbreaks in four municipalities in south-eastern Spain (five outbreaks in Municipality Benamaurel, three in Cúllar, one in Baza and eight in Villaescusa de Haro) ​(Martin, 2022)​. There is a substantial degree of uncertainty around spread outside of these regions, as well as the date and source of infection. These regions represent areas with dense sheep populations, many of which are grazing at pasture. A model developed in 2014 by the European Food Safety Authority investigated the probability that SPGP would spread if introduced into the Iberian Peninsula. It found that there would be a high probability of spread throughout Spain, into France, and further afield within 6 to 12 months if using default disease control measures, including early detection of outbreaks, culling and movement restrictions ​(EFSA, 2014)​.  

During the current outbreak in Spain, known IPs are placed under restrictions which prohibit them from exporting products of animal origin to Great Britain. This risk assessment assumes the reasonable worst-case scenario where an infected but undetected farm sends unpasteurised milk or dairy products to Great Britain.  

A particular concern is that artisan producers may travel to Great Britain to sell unpasteurised dairy products at cheese fairs or gatherings. This risk assessment will not consider trade volumes and will assess the risk per consignment of unpasteurised milk and dairy products. Other routes of transmission, such as imports of live animals, wool or untreated hides, personal imports, and illegal trade are not considered in this risk assessment.

Risk pathways flow chart 

The risk pathways by which sheep and goats in Great Britain could become infected with SPGP virus through the movement of unpasteurised milk and dairy products is shown in the risk pathway diagram (Figure 1). 

Each risk pathway considers the following stages of the risk pathway diagram: 

1. Risk pathway 1 - Risk of sheep or goats being infected by sheep or goat milk containing SPGP virus considers stages 1.1 to 1.5. 
2. Risk pathway 2 - Risk of sheep or goats being infected by sheep or goat dairy products containing SPGP virus considers stages 2.1 to 2.6. 
3. Risk pathway 3 - Risk of sheep or goats being infected by packaging contaminated with SPGP virus considers stages 3.1 to 3.6. 
4. Risk pathway 4 - Risk of sheep or goats being infected by clothing or shoes contaminated with SPGP virus considers stages 4.1 to 4.6. 
5. Risk pathway 5 - Risk of sheep or goats being infected by vehicles or equipment contaminated with SPGP virus considers stages 5.1 to 5.6.

Figure 1:  Risk pathway diagram for SPGP infection in a sheep or goat in Great Britain through the importation of unpasteurised milk and dairy products from an infected but undetected farm in Spain. 

A particular concern is that artisan producers may travel to Great Britain to sell unpasteurised dairy products at cheese fairs or gatherings.

Figure 1 shows the risk pathway starting with a sheep flock in Spain becoming infected with SPGP virus and initially considers the likelihood that this infection is undetected. The risk pathways then consider the likelihood that the SPGP virus is present in milk or that the farm environment is contaminated during milking or processing or packaging of dairy products. The likelihood of the virus being transported to Great Britain in milk or dairy products or on fomites is then considered and ends with assessing the likelihood of SPGP infection occurring in sheep and/or goats in Great Britain.

Likelihood estimates and uncertainties for each step on the risk pathways 

The likelihood estimates and uncertainties for each step on the risk pathways outlined in Figure 1 are detailed below.

Risk pathway 1: Risk of sheep or goats being infected by sheep or goat milk containing SPGP virus 

There are 5 steps.

1.1 Likelihood infection is undetected

This step considers the likelihood that animals are not showing clinical signs, or that clinical signs are undetected by farmers.  

The first clinical signs of SPGP are high fever and nasal and ocular discharge. The incubation period is generally 21 days ​(OIE, 2010)​ but can vary between 4 and 21 days ​(Gitao, et al., 2017)​. Affected animals exhibit weight loss, reduced milk production, depression, and lethargy. Mortality can be highly variable and is often around 10%​ (Spickler, 2017)​, but can approach 100% in susceptible animals ​(Spickler, 2017)​.  

The virus is consistently shed in nasal, oral, and ocular secretions from 6 to 8 days post-infection (dpi). At 6 dpi, visible clinical signs, such as skin lesions on the face and body, start to appear. SPGP virus causes highly characteristic clinical signs of cutaneous disease with papules, pustules, and nodules between 0.5cm to 3cm in diameter. Animals with mild clinical disease, which may only have a few pox lesions on the skin and mucous membranes, do not spread the virus as effectively as animals with severe clinical signs.  

There is no viral carrier state and animals that recover from SPGP have lifelong immunity ​(Kitching, 2004)​. It is assumed that asymptomatic flocks are in the pre-clinical infection stage, which may last a few days, rather than a long-term carrier state. Infected animals that have not yet developed clinical signs are infectious and would go undetected in the flock. As skin lesions take a few days to develop, animals without obvious clinical signs or skin lesions may still be milked. The milk could subsequently enter the food chain. 

Dairy sheep and goat flocks are handled at least once a day for milking. Clinical signs in dairy animals are less likely to be missed by farmers than in animals produced primarily for meat, which may be grazing at pasture and less frequently handled. A decrease in flock milk production, a common clinical sign of SPGP, would be immediately detected in a dairy flock. 

Infected animals with high viral titres with clinical signs and lesions are not likely to go undetected on farm. The reported outbreaks from Greece and Bulgaria in 2013 to 2014 estimated the within herd or flock prevalence to be between 6.6% and 8.3%. In the 2014 outbreak in Greece, flocks with as few as one case in 284 sheep were reported. In the current Spanish outbreak, a flock with just one case in 890 sheep was reported ​(WOAH, 2022)​. This suggests that farmers are good at spotting clinical cases, and the probability of not identifying an infected animal with clinical symptoms is low. 

Movement controls, enhanced biosecurity, and passive surveillance are all in place in the restricted zones in Spain ​(Martin, 2022)​. There is uncertainty around the extent of passive or active surveillance outside of the restricted areas. Nonetheless, the frequent handling of dairy sheep and goats, large milk production losses, and characteristic clinical signs mean disease is unlikely to go undetected in milking herds and flocks. 

Therefore, the likelihood that infection is undetected is low. The uncertainty is low as there are excellent data available on viral pathogenesis and clinical presentation.

1.2 Likelihood virus present in milk

SPGP virus has been isolated from milk during the early stages of disease ​(EFSA, 2014)​. SPGP is reported to cause enlargement of the udder and abortion in severe cases. Sucking lambs and kids have been proven to become infected from the milk and the skin of the teats ​(EFSA, 2014)​, although vertical transmission is not well documented ​(Spickler, 2017)​. A recent expert opinion by the European Food Safety Authority found that there was a high probability that the SPGP virus can be spread by unpasteurised milk and dairy products ​(EFSA, 2022)​. 

It is unclear whether the virus is actively shed into milk, or whether milk becomes contaminated during milking. SPGP is a systemic disease with cell-associated viraemia which precedes the appearance of lesions and marked lymphadenopathy. Disseminated infection of the skin is the result of viraemia and subsequent systemic viral spread ​(EFSA, 2014)​. It is likely that blood monocytes are important in spreading virus to secondary sites of infection. 

Given that monocytes are a small component (approximately 3%) of the somatic cell count of ewe’s milk ​(Vasicek, et al., 2019)​, it is possible that SPGP is actively shed in milk.  

The virus is also shed in urine and faeces from 4 dpi ​(Bowden, et al., 2008)​, which may contaminate milk. Normal skin in an infected sheep or goat has been found to contain high levels of the virus​ (Bowden, et al., 2008)​. Skin papules which cover the body, or may be restricted to the groin, axilla, and perineum, contain high levels of virus. Therefore, it is highly likely that virus will enter the milk, either through active secretion or through urine, faeces, or skin contamination. 

The likelihood that virus is present in milk is very high. The uncertainty is low as there are good data available on the viral pathogenesis of SPGP and the presence of SPGP in milk and dairy products.

1.3 Likelihood virus survives transport to Great Britain in milk

This risk assessment only considers unpasteurised milk and dairy products. Unpasteurised sheep and goat milk may be bottled or processed into dairy products (including cheese) either on the farm, or in an external premises. Approximately 98.2% of goat milk and 92.5% of sheep milk in Spain are used for cheese production ​(Martinez, et al., 2011)​. Very little unpasteurised milk is believed to be exported to Great Britain from Spain.  

SPGP virus survives between pH 6.6 and 8.6. Viral loads show no significant reduction in titre after 5 days at 37°C within this pH range ​(EFSA, 2014)​. The mean pH of ovine milk samples is 6.66 (min 6.61 to max 6.72) whereas the mean pH of caprine milk samples is 6.50 (min 6.38 to max 6.59) ​(Elbagerma, et al., 2014)​. Although the exact pH will vary depending on factors such as the breed of sheep or goat and on-farm husbandry, these pH values are within the limits that SPGP is known to survive. There is uncertainty around the duration of transport to Great Britain for unpasteurised milk but is likely to be under 5 days and may be as little as 12 hours. The virus is susceptible to direct sunlight but can persist for up to 6 months if protected from sunlight (EFSA 2014). Dairy products are most likely to be transported in refrigerated containers on vehicles or ships. At temperatures below 37°C in dark and refrigerated containers, it is assumed that little or no inactivation of the virus would occur during transportation.   

Therefore, the likelihood that the virus survives transport to Great Britain is very high. The uncertainty is low as good data are available on SPGP virus survival at different pH values.

1.4 Likelihood susceptible host is exposed to the virus through milk or dairy products

It is possible that flocks grazing on publicly accessible countryside may contact contaminated milk or dairy products from littering following picnics or during outdoor activities such as rambling and dog walking. This is not assumed to be a regular occurrence.  However, there is uncertainty around the rate of littering of milk and dairy products in areas of Great Britain where sheep and goats may graze. 

It is illegal to feed catering waste, kitchen scraps, meat, or meat products to farmed animals in Great Britain. However, this is known to occur in pigs and poultry kept as pets. There are no data available on the frequency of feeding kitchen waste to sheep or goats in Great Britain but is not thought to be common in these species due to their herbivorous diet.  

SPGP transmission occurs by aerosols through inhalation of large airborne respiratory droplets of infectious virus and direct contact with skin lesions, nasal secretions, and fomites ​(Spickler, 2017)​. Transmission has not been documented through ingestion of contaminated milk or dairy products but could occur through sores or wounds in the mouth. Goats are more likely than sheep to consume any foodstuffs they can access, including dairy products. Due to their inquisitive nature, goats may have a slightly greater likelihood of exposure through ingestion of contaminated product compared to sheep. Goats browse at higher levels and from people’s hands. In contrast, sheep tend to graze at ground level. 

Mechanical transmission of SPGP by insect vectors has been demonstrated in laboratory studies ​(Spickler, 2017)​. It is possible that insects such as flies may consume milk or dairy products and subsequently infect sheep through mechanical transmission on a skin wound, or by causing direct damage through blowfly strike. Blowfly strike is thought to affect 1.5% ewes and 3% of lambs in the United Kingdom each year, with at least 75% farms reporting cases annually ​(NADIS, 2022)​. Although transmission of SPGP is largely driven by close contact, transmission by mechanical vectors cannot be excluded. 

The likelihood that a susceptible host is exposed to the virus through milk or dairy products is very low. The uncertainty is high as there are no data available on the feeding practices of pet sheep or goats, or the rate of littering in the countryside. There is also high uncertainty in efficacy of transmission by mechanical vectors.

1.5 Likelihood infection in sheep or goats in Great Britain

No detailed data are available for the infectious dose of SPGP virus. Therefore, the likelihood of infection occurring in sheep or goats in Great Britain is high with high uncertainty.

Risk pathway 2:  Risk of sheep or goats being infected by sheep or goat dairy products containing SPGP virus 

There are 6 steps.

2.1 Likelihood infection is undetected 

Read Step 1.1. The likelihood that infection is undetected is low with low uncertainty.  

2.2 Likelihood virus is present in milk 

Read Step 1.2. The likelihood that infection is undetected is very high with low uncertainty.

2.3 Likelihood virus survives further processing into dairy products

In Spain, approximately 98.2% of goat milk and 92.5% of sheep milk is used for cheese production ​(Martinez, et al., 2011)​. There is considerable variability in the maturation time of different cheeses. Manchego cheese is matured for between one month and 2 years, depending on the type ​(ForeverBarcelona, 2022)​. The most common type, Manchego Curado, is matured for between 6 to 9 months. Soft cheeses have a shorter maturation time, for example feta matures for 14 to 20 days. 

Dairy products, including curds, whey, and cheese, are acidic due to lactic acid produced by bacterial cultures during fermentation. Feta has a pH of 4.4 to 4.6 ​(Brands, 2022)​. Similarly, the average pH of cottage cheese prepared from sheep milk is 3.7, whereas cottage cheese from goat milk is 3.6 ​(Ahmed, 2016)​. The survival of SPGP virus in low pH conditions is uncertain but is not thought to be stable. SPGP survives best between pH 6.6 and 8.6 ​(EFSA, 2014)​. Therefore, survival rates in cheese are likely to be lower than in milk, which is less acidic.  

There is high variability and uncertainty around the types and average pH of cheese produced and the degree of pasteurisation and maturation practices of different cheeses. There are also little data available on viral load and survival times in acidic conditions and processed dairy products.

Therefore, the likelihood the virus survives further processing into dairy products is very low with high uncertainty.

2.4 Likelihood virus survives transport to Great Britain in dairy products 

There is uncertainty around precise survival times of SPGP virus at low pH, though the virus is not thought to be stable in acidic conditions ​(EFSA, 2014)​. Therefore, SPGP survival during transport to Great Britain is likely to be low. However, the journey time between Spain and Great Britain may be short and is likely to be under five days and may be as little as 12 hours.  

Therefore, the likelihood the virus survives transport to Great Britain in dairy products is low. The uncertainty is high as the survival times in acidic conditions are unknown.

2.5 Likelihood susceptible host is exposed to the virus through milk or dairy products 

Read Step 1.4. The likelihood is very low with high uncertainty. 

2.6 Likelihood infection in sheep or goats in Great Britain 

Read Step 1.5. The likelihood is high with high uncertainty.

Risk pathway 3: Risk of sheep or goats being infected by packaging contaminated with SPGP virus 

There are 6 steps.

3.1 Likelihood infection is undetected 

Read Step 1.1. The likelihood is low with low uncertainty. 

3.2 Likelihood environment is contaminated during milking, processing or packaging

The SPGP virus is consistently shed in nasal, oral, and ocular secretions from 6 to 8 days dpi ​(Spickler, 2017)​. The papules and scabs of infected animals are likely to contain very high levels of virus, while the healthy skin of infected animals is likely to contain medium levels of virus ​(Bowden, et al., 2008)​. The virus is shed in urine and faeces from 4 dpi ​(Bowden, et al., 2008)​. 

Milking and processing plants can become heavily contaminated with skin, urine, faeces, or milk from infected sheep and goats. This is particularly the case where products are produced on the dairy farms themselves rather than in separate processing facilities due to the increased risk of cross-contamination.  

Artisan cheeses are often produced in small quantities in traditional settings, but there is uncertainty about the level of hygiene standards implemented in these types of premises compared to those implemented in large commercial cheese production premises.  

The likelihood the environment is contaminated during milking, processing, or packaging is high. The uncertainty is medium as there are no data available on hygiene practices within sheep or goat dairy facilities in Spain.

3.3 Likelihood packaging material contaminated with virus 

Packaging can become contaminated from processing plants with poor hygiene practices. There is uncertainty about the consistency of hygiene practices implemented across different types of processing plants. These contaminated products may cross-contaminate other products, particularly in high throughput packaging facilities or in small-scale facilities with limited hygiene practices. 

Therefore, the likelihood packaging material is contaminated with virus is medium. The uncertainty is medium as there are no data available on hygiene practices within sheep or goat dairy facilities in Spain.

3.4 Likelihood virus survives transport to Great Britain on packaging material 

SPGP virus is viable for extended periods in the environment. The virus is susceptible to direct sunlight but can persist for up to 6 months if protected from sunlight (EFSA 2014). Storage periods of less than 6 months, for example during maturation or storage of cheese, are unlikely to affect viral survival. SPGP virus can also survive several freeze-thaw cycles, although infectivity may be reduced. SPGP virus is known to survive desiccation and dry conditions, such as those on the outer packaging of dairy products during transport. Dairy products are most likely to be transported in refrigerated containers on vehicles or ships. At temperatures below 37°C in dark, refrigerated containers, it is assumed that little or no inactivation of the virus would occur during transportation.  

Therefore, the likelihood the virus survives transport to Great Britain on packaging material is high. Whilst the transport and storage conditions are unknown, the uncertainty is low as several studies document the long survival period of SPGP virus.

3.5 Likelihood susceptible host is exposed to the virus through milk or dairy products 

Read Step 1.4. The likelihood is very low with high uncertainty. 

3.6 Likelihood infection in sheep or goats in Great Britain 

Read Step 1.5. The likelihood is high with high uncertainty.

Risk pathway 4:  Risk of sheep or goats being infected by clothing or shoes contaminated with SPGP virus 

There are 6 steps.

4.1 Likelihood infection is undetected 

Read Step 1.1. The likelihood is low with low uncertainty. 

4.2 Likelihood environment is contaminated during milking, processing or packaging 

Read Step 3.2. The likelihood is high with medium uncertainty.

4.3 Likelihood clothing or shoes contaminated with virus

Clothing or shoes can become contaminated during milking, processing, or packaging. Skin cells, urine and faeces from infected animals contain high levels of virus ​(Bowden, et al., 2008)​. The virus is highly likely to transfer onto workers’ skin, clothing, or footwear, especially if workers are involved in milking animals or handling wool. There is uncertainty around the use or extent of personal protective equipment and biosecurity on farms, the use of which would reduce the likelihood of viral contamination.   

Therefore, the likelihood that clothing or shoes are contaminated with the virus is high. The uncertainty is medium as the high shedding rates from the skin of infected animals are well documented but there is uncertainty around the use and extent of biosecurity on farms.

4.4 Likelihood virus survives transport to Great Britain on clothing or shoes 

It is possible that farm workers or people involved in packaging or processing dairy products may work in both Great Britain and Spain. These workers may use the same clothing or shoes in both countries. Alternatively, a person working in one country may visit friends or family in another country. The SPGP virus can survive for as long as 6 months in the environment ​(EFSA, 2014)​. However, it is likely that clothes and shoes will be washed between farms and processing facilities. The virus is susceptible to common disinfectants and high temperatures ​(EFSA, 2014). It is also susceptible to highly alkaline or acidic pH. The virus should be deactivated by hand washing and ordinary disinfection practices.  

Artisan cheese producers could become contaminated in Spain and attend events in Great Britain where there is a gathering of other farmers and producers in communal areas, such as cheese fairs. However, it is unlikely that the same clothing would be worn in Great Britain without washing the clothes beforehand. 

Therefore, the likelihood that the virus survives transport to Great Britain on clothing or shoes is very low. The uncertainty is medium as the susceptibility of SPGP virus to common disinfectants is well documented. However, there is uncertainty around biosecurity practices between farms.

4.5 Likelihood susceptible host is exposed to the virus through clothing or shoes 

It is probable that farm workers would spread the SPGP virus through contaminated clothing if this were to contact skin abrasions or wounds in sheep or goats. 

Therefore, the likelihood that a susceptible host is exposed to the virus through clothing or shoes is medium. The uncertainty is low as fomites are known to transmit the virus. 

4.6 Likelihood infection in sheep or goats in Great Britain 

Read Step 1.5. The likelihood is high with high uncertainty.

Risk pathway 5: Risk of sheep or goats being infected by vehicles or equipment contaminated with SPGP virus 

There are 6 steps.

5.1 Likelihood infection is undetected 

Read Step 1.1. The likelihood is low with low uncertainty. 

5.2 Likelihood environment is contaminated during milking, processing or packaging 

Read Step 3.2. The likelihood is high with medium uncertainty. 

5.3 Likelihood vehicles or equipment contaminated with virus 

Vehicles or equipment can become contaminated during milking, processing, or packaging. Skin cells, urine, and faeces from infected animals contain high levels of virus ​(Bowden, et al., 2008)​. Virus is likely to transfer onto any equipment in direct contact with animals. 

The likelihood that vehicles or equipment are contaminated with virus is medium. The uncertainty is low as shedding rates in skin are well documented.

5.4 Likelihood virus survives transport to Great Britain on vehicles or equipment 

It is possible that farm workers or people involved in packaging or processing dairy products may work in both Great Britain and Spain and may use the same vehicles or equipment in both countries. This risk assessment only considers vehicles and equipment specifically used in milking, processing, or packaging of dairy products. There are few mobile pieces of equipment used for milking or the production of dairy products. It is highly unlikely that equipment used for milking, processing, or packaging milk or dairy products would be transported to Great Britain.    

The likelihood the virus survives transport to Great Britain on vehicles or equipment is negligible with low uncertainty. There is a low level of uncertainty around the frequency of transport of equipment or vehicles from Spain to Great Britain.

5.5 Likelihood susceptible host is exposed to the virus through vehicles or equipment 

If milking equipment were to become contaminated with milk or skin cells from an infected sheep or goat, then this will almost certainly expose another animal if reused without thorough prior disinfection. 

Therefore, the likelihood a susceptible host is exposed to the virus through vehicles or equipment is very high. The uncertainty is low as fomites are known to transmit the virus. 

5.6 Likelihood infection in sheep or goats in Great Britain 

Read Step 1.5. The likelihood is high with high uncertainty.

Final risk and likelihood estimation 

The overall likelihood of a sheep or goat in Great Britain being infected with SPGP through the importation of unpasteurised milk or dairy products is assessed as very low. Scores for individual pathways are shown in Table 4. These have been determined by combining the individual stage risk scores using the risk matrix in Table 5. The overall risk estimate for the overall risk question is determined as the pathway with the highest risk estimate. 

There is a high level of uncertainty. The largest source of uncertainty relates to mechanical transmission of the virus through insect vectors and the rate of littering of dairy products in areas of Great Britain where sheep and goats may graze.

Table 4: Individual risk pathway estimates and uncertainties

Risk Pathway	Stages considered	Conditional probabilities	Risk estimate	Uncertainty Estimate
1. Risk of sheep or goats being infected by sheep or goat milk containing SPGP virus.	1.1 x 1.2 x 1.3 x 1.4 x 1.5	Low x Very High x Very High x Very Low x High	Very Low	High
2. Risk of sheep or goats being infected by sheep or goat dairy products containing SPGP virus.	2.1 x 2.2 x 2.3 x 2.4 x 2.5 x 2.6	Low x Very High x Very Low x Low x Very Low x High	Very Low	High
3. Risk of sheep or goats being infected by packaging contaminated with SPGP virus.	3.1 x 3.2 x 3.3 x 3.4 x 3.5 x 3.6	Low x High x Medium x High x Very Low x High	Very Low	High
4. Risk of sheep or goats being infected by clothing or shoes contaminated with SPGP virus.	4.1 x 4.2 x 4.3 x 4.4 x 4.5 x 4.6	Low x High x High x Very Low x Medium x High	Very Low	High
5. Risk of sheep or goats being infected by vehicles or equipment contaminated with SPGP virus.	5.1 x 5.2 x 5.3 x 5.4 x 5.5 x 5.6	Low x High x Medium x Negligible x Very High x High	Negligible	High
Overall Estimate	All stages (Risk Pathways 1 to 5) considered	Highest risk estimate/uncertainty of Risk Pathways 1 to 5	Very Low	High

Table 5: Matrix for the multiplication of two qualitative likelihoods (Gale et al., 2010)

	Result of Likelihood 1: Negligible	Result of Likelihood 1: Very Low	Result of Likelihood 1: Low	Result of Likelihood 1: Medium	Result of Likelihood 1: High	Result of Likelihood 1: Very High
Result of Likelihood 2: Negligible	Negligible	Negligible	Negligible	Negligible	Negligible	Negligible
Result of Likelihood 2: Very Low	Negligible	Very Low*	Very Low*	Very Low	Very Low	Very Low
Result of Likelihood 2: Low	Negligible	Very Low*	Low	Low	Low	Low
Result of Likelihood 2: Medium	Negligible	Very Low	Low	Medium	Medium	Medium
Result of Likelihood 2: High	Negligible	Very Low	Low	Medium	High	High
Result of Likelihood 2: Very High	Negligible	Very Low	Low	Medium	High	Very High

*If multiplying successive likelihoods together, particularly low likelihoods, a modified matrix may be used as given in Gale et al., (2014) which allows for an improved estimation of risk accounting for basic mathematical principles; those likelihoods marked with an * are reduced to negligible.

References 

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​​​Appendices

The terminology used to define the qualitative likelihoods used in this risk assessment is based on those by EFSA (2006) and OIE (2004). This is supplemented by expanded descriptions to assist in interpretation and use of the EFSA (2006) terms.  

Table 6: Definitions for the qualitative risk terms used in this assessment, based on EFSA (2006) and OIE (2012)

Risk level	Definition
Negligible	Event is so rare, does not merit consideration
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

Table 7: Qualitative categories for expressing uncertainty given the available evidence; based on definitions within the literature (EFSA, 2006; ECDC, 2011, Spiegelhalter and Riesch, 2011) 

Uncertainty category and definition	Type of information or evidence to support uncertainty category
Low: Further information is very unlikely to change our confidence in the probability estimate	- Extensive data from peer reviewed studies on this pathogen or strain of pathogen giving similar results, for example survival time of pathogen in the environment  - Expert opinion with a consensus of opinion between experts  - Authorised documentation such as transport records, animal movement records etc. which verify timelines  - Meteorological information from recognised source  - Documentation of veterinary checks of animals on/off premises  - Laboratory study information from this outbreak  - Epidemiological information from this outbreak
Medium: Further information is likely to have an important impact on our confidence in the probability estimate	- Some data from peer reviewed studies on this pathogen or strain of pathogen but the results may be highly variable  - Evidence from previous observational studies/surveillance reports/outbreak reports  - Individual expert opinion  - Some documentation but it may not be accurate or comprehensive  - Evidence from observations, personal communications recorded from this outbreak
High: Further information is very likely to have an important impact on our confidence in the probability estimate	- Scarce or no data from peer reviewed studies on this pathogen or strain of pathogen  - Evidence from unpublished reports, observations, personal communication  - Individual non-expert opinion  - No documentation available

1. Very low is defined as: the likelihood of infection through unpasteurised milk or dairy products is “very rare, but cannot be excluded”. ↩

2. Since this risk assessment was completed, sequencing has confirmed this outbreak is a sheep pox virus. ↩ ↩²