This document was produced by MAFF as a specific response to the FMD outbreak in the UK in 2001 and was made available on their website. Risk Assessments and specific recommendations related to the conditions in the field at the time and should be viewed in this context as they may not be applicable to outbreaks occuring under different circumstances.
Foot and mouth disease
04 June 2001

MAFF: Veterinary Risk Assessment No.18: What is the risk of causing new outbreaks of fmd through collection and transport of bull semen and artificial insemination of cows?

1. Summary of risk assessment - major risk factors (full risk assessment: see annex 1)

There is a risk of causing new outbreaks of FMD through artificial insemination of cattle. The factors considered to have most influence on this risk are

• failure to quarantine bulls for period well in excess of FMD incubation period prior to entrance to main herd
• failure to clinically examine bulls regularly
• undetected infection in animals at AI centre
• failure to keep good records on donating bulls state of health
• failure to ensure semen is stored for period well in excess of FMD incubation period prior to use
• failure to check records on bulls state of health subsequent to semen collection before use of semen
• failure to locate AI centre away from susceptible animals
• failure in perimeter security of AI centre
• failure in building security, including failure in air filtration
• failure in containment of bulls
• failure of personnel to follow appropriate hygiene and quarantine measures
• failure in AI centre waste disposal
• failure to adequately seal collection bottles and distribution flasks
• failure in disinfection of collection room, drains, collection vessel, sample tubes and packaging
• disinfection of vehicles/personnel on entry and leaving AI centre (and client farms)
• method of distribution (i.e. delivery of semen for storage and use by farm personnel, or delivery by an insemination service) and whether or not distribution vehicles/personnel enter centre/farms
• number of farms visited on any one distribution route
• handling practices which may result in spillage/breakage during distribution
• failure of hygiene at insemination
• distribution route includes premises with undetected infection
• proximity of distribution route to IP or DC

Of these, the major factors are

• undetected infection in animals at AI centre
• failure to quarantine bulls for period well in excess of FMD incubation period prior to entrance to main herd
• failure to clinically examine bulls regularly
• failure to keep good records on donating bulls state of health
• failure to ensure semen is stored for period well in excess of FMD incubation period prior to use
• failure to check records on bulls state of health subsequent to semen collection before use of semen
• failure to locate AI centre away from susceptible animals
• distribution route includes premises with undetected infection, particularly if insemination service

2. Summary of risk management options

a) Reducing the risk of the spread of disease via infected semen

The risk of bulls at semen collection centres becoming infected with FMD is reduced by the biosecurity measures required in the conditions of the centre operating licences. The quarantine of frozen semen for a period greater than the incubation period of FMD is a powerful tool to prevent dissemination of infection by semen produced by bulls incubating disease. If disease develops, the semen produced by all bulls on the centre in the previous 30 days can be destroyed before it can be distributed. In contrast, fresh semen cannot effectively be quarantined before distribution. If a bull stud became infected, the distribution of fresh semen collected in the days before clinical disease was recognised would represent a significant risk of spreading FMD.

The risk may be reduced by the following measures:

i. requiring high biosecurity standards at the collection centre
ii. ensuring collection centre staff have no contact with FMD susceptible stock elsewhere
iii. ensuring animals are brought on to the centre only after a period in quarantine isolated to FMD standards
iv. ensuring that no semen collected on farms is processed in the centre
v. requiring high standards of hygiene during the processing of semen
vi. requiring veterinary supervision of the stud with regular documented stock inspections
vii. preventing the distribution of any fresh semen. Under current legislation we can only do this if the collection centre is within an infected area. The operation of Council Directive 88/407 requires us to allow the distribution of unquarantined fresh semen, but the FMD Order requires a licence for the movement of any semen into, out of or within an infected area.
viii. requiring all semen to be frozen and held in biosecure storage for 30 days before distribution. Semen to be destroyed if any bull on the centre develops FMD within this period.

b) Reducing the risk of spread of disease by semen contaminated after its production

The containers in which frozen semen is stored and transported could become contaminated at many points during the distribution chain. Although this risk cannot readily be quantified it is probably very small under normal operating conditions. Furthermore, the risk is slight that any contamination would constitute an infectious dose for cattle when administered by AI. It may be significantly reduced by standard hygienic practices, but ensuring proper compliance with these is difficult.

The risk that the interior of semen storage / transport flasks may have been contaminated by carelessness or with malicious intent cannot be entirely eliminated. Where there is doubt over the potential contamination of the interior of a semen flask, the options are either to destroy the semen or attempt decontamination. The latter is only practical where the semen is of considerable value.

Personnel delivering uncontaminated semen who do not handle livestock are no more of an inherent risk than those who deliver, for example, groceries or the post.

The risk may be reduced by the following measures:

i. ensuring semen is quarantined and stored in biosecure conditions, ideally in dedicated stores in an urban environment
ii. ensuring personnel engaged in semen storage and distribution do not have contact with FMD susceptible species
iii. ensuring that semen is not returned to "clean" stores after exposure to field conditions
iv. ensuring that shipping vessels used to transport semen into infected areas are emptied before leaving the infected area and disinfected before re-use
v. ensuring that semen is delivered at the perimeter of the farm in a vessel which is either disinfected inside and out before leaving the farm, or is left on the farm
vi. ensuring that itinerant inseminators carry only sufficient semen for immediate needs
vii. ensuring itinerant inseminators do not take their "field flasks" onto farms

c) Reducing the risk of disease being spread by itinerant inseminators

The greatest risk in practice is the spread of infection not by contaminated semen but on the person, clothes, vehicle or equipment of an itinerant inseminator. These technicians who handle infected cattle on one premises may carry infection to other premises visited subsequently. The risk can be eliminated by prohibiting visits by itinerant inseminators. There will be some risk if the practice is permitted, but practical hygienic measures should reduce it to an acceptable level. The risks are the same for other itinerant personnel who handle livestock - e.g. veterinary surgeons, embryo transfer technicians, lay foot trimmers etc, and the stock owner should take responsibility for ensuring that personnel who are asked to treat or handle animals have taken the precautions needed to prevent the inadvertent spread of FMD.

The risk may be reduced by the following measures:

i. ensuring inseminators park their vehicles at the entrance to the farm and take on to the farm only the semen required
ii. ensuring that inseminators wear full disinfectable outer protective clothing and footwear. This should include a hat which is either disposable or disinfectable, and should include a face mask.
iii. ensuring that inseminators carry out full personal disinfection routines on entering and on leaving the farm
iv. ensuring disposable equipment (used plastic sleeves, empty straws, used AI sheaths) is left on the farm for disposal by incineration
v. ensuring the AI gun is disinfected or sterilised between each farm
vi. refusing to permit any inseminator visits in infected areas

3. Recommended action

a) Reducing the risk of the spread of disease via infected semen

Most of the measures discussed in section 2 are already in place via the normal application of the Artificial Insemination of Cattle (Animal Health) (England and Wales) Regulations 1985 and the corresponding Scotland Regulations, which implement the provisions of Council Directive 88/407. Collection centre veterinarians have responded to the current emergency by enhancing the biosecurity awareness of the centre staff.

Measures iii), iv) and vii) are not fully in force at present.

Measure iii): isolation facilities are required for bulls added to collection centres, but the standard of isolation in existing facilities would probably not prevent the spread of FMD to animals in the main accommodation. This constitutes a greater hazard of spreading disease beyond the stud if the distribution of fresh semen is permitted. No bulls have been added to centres during the emergency so far.

Recommendation 1: unless movements of fresh semen are precluded, no animals should be added to bull studs until the end of the emergency. If movements of fresh semen are precluded ( recommendation 3), movement of bulls to the stud should be permitted but only under the conditions equivalent to those of the longer distance movement scheme in addition to the normal licensing requirements.

Measure iv): all licences for on-farm collection of semen were withdrawn at the start of the emergency, and none have been issued since. Enquiries are now being received.

Recommendation 2: until the emergency is over, on-farm collection of bovine semen should be permitted only in exceptional circumstances (e.g. as a precaution against the loss of a valuable blood line), and with suitable licence conditions to ensure that the health status of the processing centre is fully protected. These should preclude the semen being processed on a centre which has resident bulls, and prevent personnel who have visited the farm from returning to the centre for at least five days.

Measure vii):

Recommendation 3: no bovine semen should be distributed without first having been frozen and quarantined. No licences should therefore be issued to facilitate the use of fresh unfrozen bovine semen in AI during the FMD emergency. No bulls should be approved to move on to a centre (see recommendation 1) unless the licensee gives an undertaking not to distribute any fresh semen.

b) Reducing the risk of spread of disease by semen contaminated after its production

Risk management options 2.b.i - iii are in theory already in place as part of the implementation of the 1985 AI Regulations. Options 2.b.iv, v & vii have been implemented within infected areas as conditions of licences issued under Art 19 of the Foot-and-Mouth Disease Order (as amended). Many of these licence conditions are in practice difficult or impossible to police or to enforce, in that the licence holder is not the person who handles the semen or inseminates the cows.

Option 2.b.vi is incompatible with a normal, commercial inseminator service, since the inseminator does not know before setting out on a round of calls what semen will be required during the day. Clients expect to be able to call the inseminator at short notice and for semen from a wide range of bulls to be available.

Expert advice from the Institute for Animal Health Pirbright Laboratory is that inadvertent contamination of the interior of a semen flask (even an inseminator's flask opened on an infected premises) is unlikely to introduce sufficient virus into the interior of the flask to constitute an infectious dose for a cow when administered per vaginam. However, this potential risk has not been quantified or assessed experimentally. The risk of contaminating a storage flask (as opposed to a field flask) is greatest if the flask is regularly opened in a protection zone before preliminary cleansing and disinfection has been completed on the infected premises.

Recommendation 4: Unless there is a strong presumption of contamination of the interior of the flask, the use of semen from storage flasks in licensed premises situated in infected areas should in general not be prevented. Its movement is subject to licences under Art 19 of the FMD Order. Where the premises are situated within the protection zone, in order to minimise "traffic" into the storage flask, the semen should be moved under licence out of the protection zone to a biosecure temporary store in the infected area.

Recommendation 5: The use of semen which is in an inseminator's field flask in an infected area should be permitted under licence, subject to precautions as follows:

Semen may be used: -

• 15 days after the flask was last opened in the infected area, provided that none of the premises visited 7 days before the flask was last opened has subsequently been declared an infected premises, or
• after the semen straws have been "washed" through two changes of clean liquid nitrogen, and the interior of the flask has been disinfected.

c) Reducing the risk of disease being spread by itinerant inseminators

No visits by itinerant inseminators have been permitted in any infected area during the emergency. While this does eliminate the possibility of disease spread by licensed inseminators, it is highly disruptive to cattle farming. Besides undermining the economic viability of many farms, the inability to breed cattle threatens the milk supply in the early part of next year. Measures have been put in place to enable some breeding activity to take place, but severe difficulties will remain until inseminator services are resumed. This makes it likely that at least some farmers will resort to illegal means of breeding their cattle, with increased disease risks.

Despite the possible increase in disease risk, there are strong arguments in favour of permitting at least some inseminator visits in infected areas. The necessary hygienic precautions would need to be applied by licence conditions which under current legislation would apply to the licensee and not to the inseminator in person. Policing and enforcement would therefore be difficult. However, clients who choose to use an inseminator should be aware of the risk in doing so, and should take responsibility for ensuring that inseminators comply with licence conditions and operate hygienically whilst on their farm.

Recommendation 6: itinerant inseminator visits should be resumed in an infected area, subject to licence conditions including measures 2.c.i - c.v, when there have been no new cases in the area for at least 3 weeks, and preliminary cleansing and disinfection has been completed on the infected premises.

When preliminary cleansing and disinfection was completed more than 21 days previously on all infected premises in a group of linked protection zones, inseminator visits should be permitted to premises within the associated infected area or part of a larger infected area.

Visits should not be permitted to premises in surveillance zones around protection zones which do not meet this criterion.

Inseminators who work in an infected area would not be permitted also to work outside the infected area or in a different infected area.

Summary of recommendations.

Recommendation 1: movement of bulls to the stud should be permitted but only under the conditions equivalent to those of the longer distance movement scheme in addition to the normal licensing requirements.

Recommendation 2: until the emergency is over, on-farm collection of bovine semen should be permitted only in exceptional circumstances.

Recommendation 3: no bovine semen should be distributed without first having been frozen and quarantined.

Recommendation 4: the use of semen from storage flasks in licensed premises situated in infected areas should in general not be prevented.

Recommendation 5: The use of semen which is in an inseminator's field flask in an infected area should be permitted under licence, subject to precautions.

Recommendation 6: itinerant inseminator visits should be allowed to resume in an infected area, subject to licence conditions including measures c.i - c.v, when there have been no new cases in the area for at least 3 weeks, and preliminary cleansing and disinfection has been completed on the infected premises.

Recommended by: -

L A S Gibson
K C Taylor

ANNEX 1. RISK ASSESSMENT FOR THE RISK QUESTION:

What is the risk of causing new outbreaks of fmd through collection and transport of bull semen and artificial insemination of cows?

This risk assessment considers the various steps that are required for a new outbreak of FMD to occur through collection of bull semen and cattle AI. The probability of a new outbreak is dependent on the combined probabilities of the occurrence of each of the individual steps on the specific risk pathway. Risk pathways are represented diagramatically in figure 1.

The probability that new outbreaks of FMD are caused through collection and transport of bull semen and artificial insemination of cows is similar to the probability that new outbreaks of FMD are caused through collection and transport of boar semen and artificial insemination of sows. This probability and its associated risk factors are assessed in FMD7. However, in the case of bull semen, there are several risk factors which differ from those presented in FMD7. This risk assessment will focus on those differences, and it should therefore be read in conjunction with FMD7.

For each step in FMD7, the important risk factors are described and an assessment is made of their influence on the associated probability. An assessment of the magnitude of the probability is not made unless available evidence has been presented. The overall result is a summary of the factors which are assessed as having the greatest influence on the probability of a new outbreak. These factors, in addition to those described here, should be considered when a risk management decision is made.

For the current assessment, expert advice has been taken from the previous FMD risk assessments, in particular FMD7 and from further discussions with experts on AI. Additional advice is by personal communication from:

• L Gibson (MAFF, Page St., UK, March 2001)
• A Donaldson (FMD World Reference Laboratory, Pirbright, UK, March 2001)
• P Kitching (FMD World Reference Laboratory, Pirbright, UK, March 2001)
• R Kirkwood (Royal Veterinary College, London, UK, March 2001)

1. Bovine AI: major features and the major differences from porcine AI.

There are relatively few stud bulls in this country. Around 600 are approved per year, but most will only be active for a short time. There are an estimated 80 long term stud bulls. A substantial quantity of dairy semen is imported (60-80%), although most beef breed semen is produced at home.

Bulls entering a semen collecting centre are quarantined for a period of 30 days prior to entering the main accommodation centre, although these isolation facilities are not generally of the standard required to isolate them from FMD.

The semen is diluted so that each ejaculate provides between 80 and 800 inseminating doses (with an average of approximately 300 doses). Unlike boar semen, bull semen can be frozen and stored for a period of quarantine to ensure that the bull is free from disease before the samples are used. Legislation allows unfrozen semen to be distributed immediately although in practice this occurs rarely. Therefore, after collection cattle semen is almost always frozen and quarantined for at least 30 days prior to use. If disease is detected in a bull during this period, the semen in quarantine can then be destroyed.

A significant quantity of the semen will be used within a few months after the 30 day period, but much will not be used for a year. A significant quantity will be kept for several years before use (bull semen can be stored indefinitely). Semen is not routinely tested for FMD.

Semen is delivered to the farm by inseminators, who may carry between a few hundred and several thousand straws of semen in their flasks, or by delivery staff/couriers who need have no livestock contact. Whereas there are very few itinerant pig inseminators, the majority of farms rely on visiting inseminators. The inseminator may visit, depending on the time of year, between 5 and 30 farms per day. Insemination, which in cattle is a relatively invasive procedure (requiring a rectal examination to manipulate the insemination catheter), may be undertaken by the inseminator or by staff on the farm.

In addition, approximately 5000 farmers have their own frozen stores of bull semen. The number of doses they keep is limited to three times the number of breeding cows they have.

2. Probability of a new outbreak of FMD occurring as a result of cattle AI

As already indicated, this assessment is based on FMD7, the risk assessment for porcine AI. The following table includes only those factors which are likely to be additional or different to those for pigs.

Conclusions

The probability of causing a new outbreak of FMD by infected semen used in cattle AI is most dependent on the use of an undetected infected stud bull at the AI center. This probability is reduced both by implementing an appropriate period of quarantine when introducing a new bull (provided it is not exposed to infection whilst in quarantine), and allowing an adequate period prior to semen being distributed. The usual 30 days prior to semen use is considered adequate for clinical symptoms of FMD in the bull to be identified.

Due to the quarantine of the stud bull, and the storage of frozen semen, the probability that semen is infected at the point of use is exceptionally low. However, the consequence and impact of a stud bull being infected but undetected, and its semen distributed and used, could be very high (due to dilutions).

Contamination is the other possible method of spread. Reducing the numbers of semen straws held by inseminators in their flasks will reduce the probability that straws may be exposed and subsequently contaminated as the inseminator travels from farm to farm. Ensuring that appropriate hygiene precautions are undertaken by the inseminator (including with respect to equipment and flask) will also reduce this probability.

In addition, the probability of contamination at any stage will also be reduced by reducing the number of farm visits per day made by the inseminator and by the insemination procedure being undertaken by home farm staff.

Risk assessment authors:
L Gallagher
C Livesey
Dr L Kelly
Dr M Wooldridge