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<body><div class="header"><p class="header"><b>APHIS Risk Consideration on the Necessity of the 40-Day Post Collection Holding Period for Swine Semen Imported from the European Union</b></p>
</div>
<p><b>APHIS Risk Considerations on the Necessity of the 40 Day Post-Collection Holding Period for Swine Semen Imported from the European Union </b></p>
<p><img src="embedded:image1.jpg" alt="image1.jpg"><b><i> </i></b></p>
<p><b>Animal and Plant Health Inspection Service </b></p>
<p><b>Veterinary Services </b></p>
<p><b>June 2008 </b></p>
<p><b><u>Table of Contents</u></b> 
</p>
<table><tbody><tr>	<td><p><b></b></p>
</td>	<td><p>Page</p>
</td></tr>
<tr>	<td><p><b>List of Abbreviations and Definitions</b></p>
</td>	<td><p>2 </p>
</td></tr>
<tr>	<td><p><b>Executive Summary</b></p>
</td>	<td><p>3 </p>
</td></tr>
<tr>	<td><p><b>Introduction</b></p>
</td>	<td><p>5</p>
</td></tr>
<tr>	<td><p><b>Classical swine fever (CSF) and classical swine fever virus (CSFV)  </b></p>
</td>	<td><p>6 </p>
</td></tr>
<tr>	<td><p><b>Current APHIS restrictions  </b></p>
</td>	<td><p>8</p>
</td></tr>
<tr>	<td><p><b>The 40 -day post collection holding period </b></p>
</td>	<td><p>8  </p>
</td></tr>
<tr>	<td><p><b>Swine semen for artificial insemination</b></p>
</td>	<td><p>9</p>
</td></tr>
<tr>	<td><p><b>Current EU restrictions</b></p>
</td>	<td><p>9</p>
</td></tr>
<tr>	<td><p><b>Impact of APHIS restrictions</b></p>
</td>	<td><p>12</p>
</td></tr>
<tr>	<td><p><b>Conclusions</b></p>
</td>	<td><p>14</p>
</td></tr>
<tr>	<td><p><b>References</b></p>
</td>	<td><p>16</p>
</td></tr>
</tbody></table>
<p><b><u>Abbreviations and Definitions</u></b></p>
<p>AIC   




Artificial Insemination Center  
</p>
<p>APHIS   



Animal and Plant Health Inspection Service 
</p>
<p>APHIS-defined EU CSF region
Currently includes Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Republic of Ireland, Italy, Latvia, Lithuania, Luxembourg, Netherlands, Poland, Portugal, Spain, Sweden and the United Kingdom
</p>
<p>CFR




Code of Federal Regulations</p>
<p>CSF 




Classical swine fever
</p>
<p>CSFV  



Classical swine fever virus 
</p>
<p>EC




European Commission
</p>
<p>EU   




European Union 
</p>
<p>EU CSF region


Same as APHIS-defined EU CSF region
</p>
<p>EU-15
Includes the 15 MS that comprised the EU in 2004 (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Republic of Ireland,  Italy, Luxembourg, Netherlands, Portugal, Spain, Sweden and the United Kingdom)
</p>
<p>FR
 



Federal Register
</p>
<p>MS




Member State
</p>
<p>OIE




World Organization for Animal Health</p>
<p><b>Executive Summary</b></p>
<p>The Animal and Plant Health Inspection Service (APHIS) has been requested to reevaluate the need for the 40-day post collection holding period (40-day hold) for swine semen from the APHIS-defined EU CSF region.  To prevent the introduction of classical swine fever (CSF) into the United States (US) the Animal and Plant Health Inspection Service (APHIS) has in place a set of restrictions on the importation of swine, pork and pork products, including breeding swine and swine semen, from the European Union (EU) (9 CFR 94.24 and 9 CFR 98.38).  In brief, the restrictions for swine semen are similar to those for swine, pork and pork products with the additional requirement that prior to shipment swine semen be held for a period of at least 40 days after semen collection and that the donor boar, along with all other swine at the semen collection center, be observed by the center veterinarian of clinical signs of CSF (9 CFR 98.38).  
</p>
<p>At the time the regulation was developed, APHIS assumed that the 40 day hold requirement would not be overly burdensome for exporters of swine semen or otherwise inhibit trade.  However, APHIS subsequently became aware that viability of swine semen held for 40 days is an issue; in fact, holding fresh swine semen for 40 days renders it useless because methods to preserve fresh swine semen for 40 days do not exist and the use of frozen semen has not proven, as yet, to be practical in swine production.   
</p>
<p>Artificial insemination is widely practiced throughout the swine industry affording U.S. swine producers broad access to global genetics.  Approximately 99% of swine semen used for artificial insemination is as a fresh extended chilled product with a usable lifespan of only 1 to 5 days after collection.  Preservation of viable swine semen for longer time periods requires alternative storage methods such as freezing (cryopreservation).  These preservation methods are not practical because swine semen is highly sensitive to freezing and thawing resulting in unacceptable decreases in viability and fertility.  As a result, the 40 day post collection holding period for swine semen is an barrier for US swine producers, impeding access to needed swine genetics available through the importation of swine semen from the EU. 
</p>
<p>Based on previous evaluations AHPIS considers the “APHIS-defined EU CSF region” as a single region for CSF. The basis for this is the existence of an open-border trading policy within the EU, with uniform application of all EU regulations in every EU-Member State (MS).  APHIS previously determined that the EU quarantine decisions, with respect to areas affected by CSF, would provide the basis for the U.S. import restrictions with respect to CSF and prior to export of swine products from the region, the competent veterinary authority of the individual MS would certify compliance with both the EU and U.S. requirements. In addition, APHIS regulations prohibit the importation of swine or swine products, including swine semen, for at least 6 months from areas that had been under restrictions (quarantine) for an outbreak of CSF.
</p>
<p>Since the initial APHIS risk analysis, APHIS has added a 6-month restriction on importation of swine and swine products from an affected region following an outbreak. In addition, significant changes have been made in the harmonized EU regulations to strengthen its controls for CSF, including; additional controls on the intra-community trade of swine semen, the immediately halt of swine semen movements from semen collection centers within all restriction (quarantine) zones established during an outbreak of CSF, and additional testing requirements for all animals in swine semen centers prior to releasing CSF restriction (quarantine) areas.  
</p>
<p>APHIS has now evaluated the subsequent changes to both APHIS and EU regulations and determined that there are adequate risk mitigations in place and that the 40-day holding period after collection is not a practical or necessary restriction.  APHIS now considers that the 40-day post collection holding period for on swine semen to be an unnecessary and impractical mitigation step that should be removed from the regulations for the APHIS-defined EU CSF region.  </p>
<p><b><i>Introduction</i></b></p>
<p>To prevent the introduction of classical swine fever (CSF) into the United States (US) the Animal and Plant Health Inspection Service (APHIS) has in place a set of restrictions on the importation of swine, pork and pork products, including breeding swine and swine semen, from the European Union (EU) (9 CFR 94.24 and 9 CFR 98.38).  In these regulations, APHIS recognized a region within the EU to be at low risk for CSF and required a series of mitigations to address the low but ongoing risk related to the presence of the Classical Swine Fever Virus (CSFV) in some wild boar populations [2-11].  </p>
<p>Based on the existence of an open-border trading policy within the EU, with uniform application of all EU regulations in every EU-Member State (MS), APHIS previously determined that for CSF the EU quarantine decisions would provide the basis for the U.S. import restrictions whenever an outbreak of CSF occurs in the EU.  Prior to export of swine products from the region, the competent veterinary authority of the individual MS must certify compliance with both the EU and U.S. requirements. This region initially included the 15 Member States (MS) comprising the EU in 2004 and was referred to as the EU-15.  Since that time additional MS including the Czech Republic, Latvia, Lithuania and Poland have been added and the region is referred in the Code of Federal Regulations (CFR) as the APHIS-defined EU CSF region.</p>
<p>In brief, the restrictions in the CFR for swine semen are similar to those for swine, pork and pork products with the additional restriction for swine semen of a holding period of at least 40 days after semen collection of the swine semen and donor boar, along with all other swine at the semen collection center, for observation by the center veterinarian of clinical signs of CSF (9 CFR 98.38) prior to shipment.  </p>
<p>APHIS has been requested to reevaluate the need for the 40-day post collection holding period (40-day hold) for swine semen from the APHIS-defined EU CSF region. At the time the regulation was developed, APHIS assumed that the 40 day hold requirement would not be overly burdensome for producers of swine semen or otherwise inhibit trade.  However, APHIS subsequently became aware that viability of swine semen held for 40 days is an issue; in fact, holding fresh swine semen for 40 days renders it useless because methods to preserve fresh swine semen for 40 days do not exist and the use of frozen semen has not proven, as yet, to be practical in swine production [30, 33].   
</p>
<p>The APHIS regulations were put in place, in part, in response to the 1997-1998 CSF outbreaks in the Netherlands.  These outbreaks were the most severe and prolonged CSF outbreaks experienced in the EU in recent history and occurred in an area with a high concentration of swine and swine farms.  The outbreaks started in February 1997 and continued until March 1998. During the outbreaks, a total of 429 swine holdings became infected with CSFV and were depopulated.  In addition, approximately 1300 herds were slaughtered preemptively. By the time the outbreak was fully eradicated, a total of nearly 11 million pigs were killed at an estimated cost exceeding several billion US dollars [25, 27].  
</p>
<p>Included in the Netherlands outbreaks were two related artificial insemination centers (AICs), one of which was an export-oriented EU-approved center.  These AICs were located within the 3 km protection zone established around the first infected farm identified in the outbreak.  Over 25,000 doses of semen [42] from the infected AICs was shipped to 1680 herds before the shipment of semen was halted. It was concluded that artificial insemination with contaminated semen from the infected AICs was the most likely source of CSF infection for 21 to 36 of the 1680 herds receiving potentially infected semen [32, 43].  
</p>
<p><b><i>Classical swine fever (CSF) and classical swine fever virus (CSFV)<u>  </u></i></b></p>
<p>Classical swine fever (CSF) is caused by infection with the classical swine fever virus (CSFV), a member of the family Flaviviridae, genus <i>Pestivirus</i> [31, 37].  CSFV is hardy and stable over a wide range of pH (between pH 4 and 10) [41] and temperature [28].  CSFV may remain viable in chilled pork products for up to 3 months and in frozen pork products up to 4 years [26] and may be preserved at -70oC for years with minimal loss of titer especially if cryoprotectants are used [26].  Survival of CSF virus in semen has been estimated in experimental studies to be 12-72 hours at 20oC and one month to several years at 4oC or below [28].   
</p>
<p>The typical route of infection is oronasal and the infective dose by the oronasal route may be quite low but dependent on the virulence of the strain of the infecting virus [20, 39-41].  The highest risk for CSF infection comes from direct contact with infected pigs (typically young pigs) or infected wild boar populations, contact with transportation equipment or people in direct contact with infected swine or as a “neighborhood” infection for holdings within 500 to 1000 meters of an infected premises [37].  
</p>
<p>Direct or indirect contact with CSF infected wild boar populations remain an important factor in the epidemiology of CSF infection of domestic swine in the EU [23, 36, 37, 39].  Wild boar populations in parts of the EU remain a known risk for continuing CSF outbreaks in the region and control measures in the EU are critical for the overall control of CSF throughout the EU [29, 36, 37].  Of the CSF outbreaks in the 1990s in Germany, nearly 70% were primary or single outbreaks associated with direct or indirect contact with infected wild boar, and an additional 20% were associated with illegal feeding of swill or catering waste.  In Germany, multiple or secondary outbreaks occurred primarily in areas with higher pig concentration, especially in areas of high pig density (more than 250 pigs/km2) and were associated with the movement of infected pigs or neighborhood contacts with infected farms, with the highest risk for neighborhood infection being associated with farms located within approximately 500 meters of an infected holding [29].   
</p>
<p>However, these are factors that are not likely to pose the same risk for approved artificial insemination centers (AIC) because of the additional biosecurity measures in place that prevent contact with animals outside the facility and prohibit the feeding of catering waste. The likelihood that an outbreak of CSF will originate from an EU approved AIC is very low, although the virus can be transmitted to the AIC if it is located in an area under restrictions for an outbreak of CSF [13]. 
</p>
<p>Transmission of CSF infection through artificial insemination with virus contaminated semen has been found to occur under both natural and experimental conditions [22, 28, 30, 32].  However, the detection of CSFV in semen by the standard technique for CSFV isolation in cell culture remains difficult due to the cytotoxic effect of boar semen on cell culture [28].  In experimentally infected boars, CSFV was isolated from semen by modification of the standard virus isolation technique [22, 28] or by reverse transcription-polymerase chain reaction (RT-PCR) [14].  The virus titer in the semen of experimentally infected boars was found to be rather low although the titer of virus added to raw unextended boar semen was undiminished after storage at 48oC or -70oC overnight [22].  It is possible that the titer of CSFV may be too low to detect by standard methods, especially during a subclinical infection, although the infective dose of CSFV through artificial insemination remains unknown. [13, 22, 28].   
</p>
<p>CSFV appears to be shed into the semen during the early, viremic phase of infection, prior to the formation of detectable serum antibodies [21, 28] which generally do not appear until about 1 week after viremia (or detection of the virus by virus isolation in the blood) [24].  In boars experimentally infected with CSFV via the oronasal route, CSFV nucleic acid was detected in semen between 5 and 11 days post infection and persisted in some boars up to 63 days post infection [14, 21, 28].  The experimentally infected boars remained clinically healthy or exhibited only minor clinical signs but developed serum neutralizing antibodies in the typical timeframe of between 14 and 21 days after inoculation [21, 28].   
</p>
<p>Clinical signs of CSF in adult swine are not pathognomonic and the disease may be subclinical or very mild, especially compared to the clinical signs generally seen in younger swine.  Depending on the virulence of the strain of infecting CSFV, adult swine may show only a transient fever during the viremic phase of infection which may contribute to delays in the diagnosis of CSF on swine holdings where only adult swine are present [27].  Viremia and shedding of virus into semen could occur before clinical signs become apparent either in individual donor boars or before infection within the AIC would be detected [13].  Failure to diagnose CSF infection in the boar herd could potentially allow the infection to be spread unnoticed to many vulnerable sow herds if the AIC continues to ship potentially contaminated semen [28]. 
</p>
<p>In approved AICs the biosecurity measures and control of animal movements into the centers with preadmission testing and quarantine help prevent the exposure of animals in the AIC to the CSF virus.  The likelihood that an outbreak of CSF will originate within approved AIC is very low, although the virus can be transmitted to the AIC if it is located in the immediate area of an outbreak [13].  In general, controls aimed at exclusion of and surveillance for CSFV in AICs are considered the most effective risk mitigation for preventing the transmission of CSF through semen imported from the EU used for artificial insemination. APHIS considers that controls aimed at exclusion of and surveillance for CSFV in artificial insemination centers provide the most appropriate risk mitigation. </p>
<p><b><i>Current APHIS Regulation  </i></b></p>
<p>The following restrictions apply to the importation of swine semen into the United States from the EU, as found in 9 CFR 98.38:   
</p>
<p>•The semen must come from a semen collection center approved for export by the competent veterinary authority of the Member State within the APHIS-defined EU CSF region. 
</p>
<p>•The semen must not have been collected from a donor boar in region or zone under restriction for the presence of CSF in either domestic swine or wild boar.  
</p>
<p>o Importation of semen is restricted from the time of detection until the designation of the zone as a restricted zone is removed by the competent veterinary authority of an EU MS of the APHIS-defined EU CSF region or until 6 months following depopulation of the swine on affected premises in the restricted zone and the cleaning and disinfection of the last affected premises in the zone, whichever is later.   
</p>
<p>o Restrictions are removed from zones established because of the detection of CSF in wild boar at the time designated by the competent veterinary authority of the individual MS.  
</p>
<p>o Semen must not have been collected from a donor boar that transited restricted areas or was commingled with swine that at any time were in any of the regions or zones under restriction for CSF. 
</p>
<p>•The donor boar must be held in isolation for at least 30 days prior to entering the semen collection center and must have been tested with negative results with a CSF test approved by the Office International des Epizooties (World Organization for Animal Health, OIE). 
</p>
<p>•No equipment or materials used in transporting the donor boar from the farm of origin to the semen collection center may have been used previously for transporting swine that do not meet the requirements of this section, unless such equipment or materials have first been cleaned and disinfected. 
</p>
<p>•Except for semen collected from swine in Denmark, Finland, the Republic of Ireland, Sweden, or the United Kingdom, the donor boar must be held at the semen collection center and observed by the center veterinarian for at least 40 days following collection of the semen, and, along with all other swine at the semen collection center, exhibit no clinical signs of CSF. 
</p>
<p>•The semen must be accompanied by a certificate issued by a salaried veterinary officer of the competent veterinary authority of the MS within the APHIS-defined EU CSF region, stating that all of these provisions have been met. 
</p>
<p>With the exception of the 40 day post collection holding period, these restrictions are similar to those required by APHIS for importation of pork, pork products and live breeding swine from the APHIS-defined EU CSF region found in 9 CFR 94.24 and 94.25.  
</p>
<p><b><i>  The 40 Day Post-Collection Holding Period </i></b></p>
<p>The 40 day post collection holding period is consistent with the OIE standard for swine semen imported from regions free of CSF in domestic pigs with wild boar populations [38].  For regions free of CSF in domestic pigs but with wild boar populations, OIE recommends that donor boars be kept in a region free of CSF since birth or for at least 3 months prior to collection and show no clinical signs of CSF on the day of collection of the semen and for the following 40 days. For swine semen from regions considered to be free of CSF the OIE recommends that the donor animals be kept in a country, zone or compartment free of CSF since birth or for at least 3 months prior to collection and showed no clinical signs of CSF on the day of collection of the semen.  The OIE general guidelines for swine semen recommend that swine semen for export should be stored in liquid nitrogen for at least 28 days [38]. </p>
<p><b><i>Swine semen for artificial insemination</i></b></p>
<p>Approximately 99% of all swine semen collected for use in artificial insemination is used as fresh extended chilled semen with little variation worldwide in the methods used for packaging and insemination of liquid swine semen.  Fresh extended chilled semen is intended for use within 1 to 5 days of collection because the fertility of fresh semen declines rapidly with prolonged storage.  Even the use of proprietary commercial swine semen extenders cannot preserve the fertility of fresh chilled semen beyond a maximum of 10 days after collection [1, 12, 30 33, 35].  
</p>
<p>Techniques for cryopreservation (freezing) of swine semen have been available since 1975.  However, less than 1% of all swine semen is used as frozen semen because boar semen is highly sensitive to chilling, freezing and thawing [12].  There is a marked decrease in fertility with frozen swine semen compared with fresh semen, resulting in both lower farrowing rates and smaller litter size [33, 35].  As a result most protocols for using frozen semen in swine remain experimental and suggest the use of two to three times the standard inseminating volume, multiple inseminations, alternative insemination schedules relative to ovulation in the sow, and/or alternative insemination techniques [30, 34, 35].  
</p>
<p>Although there has been considerable interest in the potential use of frozen swine semen, much needs to be improved before frozen swine semen is more widely used [35].  Efforts to develop practical alternative and breeding management techniques to allow for the use of frozen swine semen have attempted to overcome the limited lifespan of thawed spermatozoa in the female reproductive tract.  
</p>
<p>Until the techniques for freezing and utilization of swine semen can be further developed, the use of fresh swine semen remains the most practical way to import swine genetics for use in US swine production and denies the US pork industry ready access to European swine genetics.  This suggests that the requirement to hold fresh swine semen for at least 40 days following collection is not a practical risk mitigation step and should be reevaluated.  
</p>
<p><b><i> Current EU Restrictions  </i></b></p>
<p>In response to the 1997-1998 CSF outbreaks in the Netherlands, a number of changes were made to EU legislation establishing control measures for CSF within the EU and to the legislation controlling the intra-Community trade of swine semen [15-18].  The most significant impacts include the implementation of more restrictive movement controls during an outbreak with additional testing requirements for animals in an AIC before release of the restriction area and resumption of semen shipments. Since the outbreak, EU legislation has been amended  to add specific conditions for approval and supervision of AICs; testing and quarantine of swine prior to admission to an AIC; routine periodic CSF surveillance requirements for swine at an AIC; conditions for semen collection and movement control restrictions; and CSF testing requirements during an outbreak. </p>
<p>In summary, the EU legislation regulating AICs now includes the following requirements for swine semen intended for intra-community trade, some of which are discussed in more detail later:   
</p>
<p>·  During an outbreak no semen from any AICs within a CSF surveillance or protection zones can move.
</p>
<p>· All boars in AICs within surveillance or protection zone must be clinically examined and serologically tested individually before the restriction zones are lifted and the AIC resumes shipment of semen.</p>
<p>· All EU approved AICs are inspected by an official veterinarian at least twice a year and must be under the permanent supervision of a center veterinarian who approves the entry of all animals.  
</p>
<p>· The movement of all animals in and out of the AIC must be recorded. 
</p>
<p>· Only boars originating from herds which were not in areas under restrictions for CSF can enter an approved AIC.   
</p>
<p>· Before admission to approved AIC, boars must be tested and found negative for CSF and quarantined for at least 30 days.  The testing must be done by an EC approved method in a laboratory approved by the MS.   
</p>
<p>· Routine periodic compulsory serologic testing of boars in the AIC for CSF. 
</p>
<p>· Clinical observation of boars at the time of collection. 
</p>
<p><u>Movement controls</u>:  During the 1997-1998 CSF outbreaks in the Netherlands, the movement of semen from within the control and surveillance zones was not restricted.  Prior to 1998, swine semen continued to be shipped from areas under CSF restrictions into areas not under restriction.  This lack of movement restrictions reflected previous EU experience during the 1970s and 1980s when AICs had remained free from infection during multiple CSF epizootics.  As a result of the lack of movement restriction more that semen left the restriction zones from 2 AICs prior to identification of the presence of CSFV in the within the first infected AIC.  The other infected AIC was a related enterprise that handled semen from the first AIC.  Infected semen from these two AICs was considered to be the source of infection for between 21 and 36 farms as the result of the 25,000 doses of potentially infected semen that was sent to 1680 farms during the outbreak.  [32]. 
</p>
<p>Under current EU regulation there are several important movement controls designed to control CSF, including movement restrictions on semen during CSF outbreaks in either domestic swine or wild boar [16].  The shipment of swine semen is immediately halted from any AIC within an established restriction zone.  Movement of semen is also halted as soon as the presence of CSF in an AIC is suspected.  Restrictions are also placed on the movement of animals, people and vehicles entering or leaving holdings under suspicion of CSF and all movement is subject to written authorization of the competent authority. 
</p>
<p>Movement continues to be controlled once the presence of CSF is confirmed on a holding.  Protection (control) and surveillance zones are established around the infected holding and the shipment of semen from all AIC within these zones is halted and an epidemiologic investigation is then conducted to track the movement of persons, vehicles, pigs, carcasses, semen, meat or other material which could have transported the virus to or from the holdings in question.  
</p>
<p><u>Diagnostic testing procedures and sampling</u>:  Current EU regulation requires the clinical examination and sampling of pigs on all suspected holdings [15].  In the case of an AIC, all animals in the AIC must be tested individually, in comparison to other swine facilities, such as growing facilities, where sampling is required to support the 95% confidence of detection but does not require testing 100% of individuals present.  
</p>
<p>All boars in an AIC that are killed as a preventive measure must be tested for CSF.  On a holding were CSF is suspected all boars must be sampled individually.  Boars in AICs within a restriction zone must all be clinically examined and serologically sampled before lifting the restriction and resumption of movement of animals or semen may occur.  Following repopulation after an outbreak, boars must be serologically tested at a level to detect infection with the prevalence of 10% with 95% confidence. </p>
<p><u>Pre-admission testing and quarantine prior to entering an AIC</u>: EU regulations were amended to require that all boars admitted to an AIC be sourced from herds that are not situated in areas restricted due to CSF or other disease [17]. All boars must be quarantined at least 30 days prior to admission in a non-restricted area, and tested for CSF in the 30 days prior to quarantine. Boars must move directly to the AIC from the quarantine accommodation and show no signs of clinical disease on the day of entry.  
</p>
<p><u>Serologic testing</u>: Periodic routine compulsory serologic testing for CSF for animals kept at an approved AIC is required [17]. All animals must be tested at least once during their stay in the AIC and at least once a year if they stay longer than 12 months in the AIC.  Routine serology of the AIC population is done every three months and must include 25% of the animals in the AIC as selected by the center veterinarian to be representative of the total population of the center.  Every animal must also be tested for CSF when leaving the center and this testing can be done at the abattoir.   
</p>
<p>Periodic serology is useful because laboratory confirmation of the presence of CSFV is generally necessary in populations of adult swine, even for secondary cases during large outbreaks, although no diagnostic method is able to detect all infected pigs [24, 39, 40].  In herds of adult animals serology may be necessary to detect the presence of CSFV as the clinical signs of CSF may be much milder than in younger populations and therefore more difficult to recognize clinically.  During the Netherlands outbreak, it was observed that many adult swine were febrile only for a brief time during the early viremic phase of infection and that these clinical signs could easily be missed in individual animals [20, 39].  
</p>
<p>Serology is of particular value during times when CSF has not been present for an extended time period in a region and would not be considered as a primary differential diagnosis [13].  An individual animal infected with CSFV typically shows clinical signs between 2 and 14 days after exposure to the virus but does not develop serologically detectable antibodies for at least 10 to 14 days but may take up to 21 days [1, 20].  In an experimental infection CSFV was found in semen beginning at 7 to 14 days post infection of boars using RT-PCR which corresponds to the time of viremia [14].   
</p>
<p>The systematic routine serological approach adopted by the EC uses the total population of the AIC to monitor for the presence of CSF rather than relying on serology from individual donor animals or observation of clinical signs, thereby increasing the likelihood of detecting the presence of CSFV in an AIC [19]. However, routine serology is of particular value to detect the presence of CSFV in adult populations where there may be no clinical signs or when CSF has not occurred for an extended time period and would not be considered as a primary differential diagnosis [13].  </p>
<p><u>Clinical observation</u>:  Semen may be obtained only from animals which show no clinical signs of disease on the day the semen is collected. From a disease control standpoint the day of collection is the most useful time period to clinically observation the animals in order to prevent the shipment of contaminated semen because the early or viremic phase of CSF infection is most likely time for the virus to be present in semen and is concurrent with the most likely time for expression of clinical signs [28, 37].   
</p>
<p><u>Summary</u>:  Current EU legislation specifies the conditions for approval and supervision of AICs, pre-admission quarantine and testing of boars, serologic testing for CSF, clinical observation of donor boars, and movement controls.  These measures substantially mitigate the risk of CSF infected or exposed animals entering approved AIC; controls the risk that CSFV had entered an AIC undetected; and puts in place movement restrictions when CSF outbreaks are suspected and provide additional risk mitigation for the prevention of contamination and distribution of swine semen with the CSF virus. APHIS considers that these measures serve to adequately decrease the likelihood of importing swine semen contaminated with CSFV.  
</p>
<p><b><i>Impact of APHIS restrictions  </i></b></p>
<p>The impact of the changes made in APHIS regulation of the importation of swine semen from the APHIS-defined EU CSF region warrants review for the risk mitigation they provide.  Specifically, 9 CFR 98.38 requires certification by EC officials that the entry of animals into AIC be controlled, movement restrictions imposed during and after outbreaks, and that the health status must be verified by the competent veterinary authority of the exporting country [2-11].  
</p>
<p>In addition, APHIS has recognized in previous assessments that CSFV is circulating in segments of the wild boar population in some of the EU-MS and that in the future occasional outbreaks may occur due to direct or indirect contact with infected wild boar.  Since 2006, APHIS has in place a restriction on the movement of semen and donor boars out of zones under restriction for the presence of CSF in domestic swine for at least 6 months after the cleaning and disinfections of the last affected premises in the restricted zone.  </p>
<p><u>Certification of health status of donor boars entering AIC</u>:  APHIS has in place several restrictions on the importation of swine semen from the APHIS-defined EU CSF region designed to mitigate the risk of entry of animals infected with or exposed to CSFV into AICs.  In that regard, the competent EU veterinary authority must certify that boars have never lived in any region or zone under restrictions for the presence of CSF in domestic swine or wild boar and have not been commingled with swine from any area under restriction.  All boars must have been individually tested for CSF and found to be negative prior to entering quarantine and must be quarantined for at least 30 days prior to entering the AIC.  Vehicles used to transport boars from their farm of origin to the AIC must be certified to not have been previously used for transporting swine from areas under restrictions, unless cleaned and disinfected.  
</p>
<p><u>Movement Controls and Certification</u>:  APHIS regulation require the competent EU authority to certify that semen was not shipped from AICs in areas affected by CSF in either domestic swine or wild boar.  This prevents the shipment of semen from any AIC within either a control or surveillance zone.  Previous APHIS assessments found the risk mitigations and control zones established by the EU veterinary officials in the APHIS-defined EU CSF region to be adequate to prevent widespread exposure and/or establishment of the disease and determined it would recognize the geographical boundaries of the controls imposed by the EC related to CSF infection control measures [2-7].  
</p>
<p>In 2006, APHIS added a restriction on the shipment of semen from an area previously under restrictions for CSF in domestic swine for an additional 6 months following the depopulation, cleaning and disinfecting of the last infecting premises in the restriction zone [3, 4].  The additional 6 month extension of restrictions allows for the detection of the entry of the virus into an AIC even if it was not clinically apparent or when the clinical signs of CSF are minimal.  This delay would allow for the development and detection of serologic response, which typically take up to14 days to develop [19, 26].  APHIS considers that the additional 6 month time period restricting exporting of semen from areas previously under restriction for CSF in domestic swine to be a strong mitigation step to effectively mitigate the risk of importing CSFV through infected swine semen. 
</p>
<p><u>Certification of swine semen shipments</u>:  APHIS regulations require that the competent EU authorities certify that swine semen is from a semen collection center approved for export by the competent veterinary authority of the MS.  Shipments must be accompanied by a certificate issued and signed by a salaried veterinary officer of the exporting MS.  In addition, the certificate must also verify that all conditions in APHIS regulations are met, including that the semen did not originate from an area that has been under restrictions for CSF in domestic swine for the last 6 months. 
</p>
<p><u>Summary</u>:  Current APHIS regulations specify the pre-admission quarantine and testing of boars to certify the health status of donor boars entering the AIC, clinical observation of the donor boar and all other animals in the AIC at the time of semen collection, movement controls and certification of swine semen shipments by the veterinary authority that the semen did not originate from an area under any restrictions for CSF in domestic swine for the last 6 months.  Taken together these measures substantially mitigate the risk of CSF infected or exposed animals entering approved AICs; mitigate the risk that CSFV had entered an AIC undetected; and puts in place movement restrictions when CSF outbreaks are suspected and provide additional risk mitigation for the prevention of contamination and distribution of swine semen with the CSF virus. APHIS considers that these measures serve to adequately mitigate the risk of importing swine semen contaminated with CSFV.  
</p>
<p><b><i>Conclusions  </i></b></p>
<p>APHIS considers that based on current regulations the risk of importing semen potentially contaminated with CSFV from the APHIS-defined EU CSF region is low and concludes that the 40-day post collection holding period is not a necessary risk mitigation step.  APHIS considers the risk of CSF infection from importation of swine semen from approved AICs in the APHIS-defined EU CSF region to be low under the restrictions contained in 9 CFR 98.38.  APHIS had concluded that mitigations in place for the importation of swine and swine products are adequate and appropriate for the importation of swine semen without the need of a 40-day post collection holding period. </p>
<p>In brief, these restrictions include:  
</p>
<p>•Swine semen can only be imported from an AIC approved for export by the competent veterinary authority of the APHIS-defined EU CSF region MS and must be accompanied by a certificate issued by a salaried veterinary officer of the APHIS-defined EU CSF region MS, stating that these provisions have been met. 
</p>
<p>•The donor boar must not have lived in any region or zone or have been commingled with swine from regions under restriction for the presence of CSF in domestic swine or wild boar.   
</p>
<p>•For areas previously under restriction for CSF in domestic swine these restrictions will remain in place for 6 months following depopulation of the swine on affected premises in the restricted zone and the cleaning and disinfection of the last infected premises in the zone.  
</p>
<p>•Prior to entering an AIC the donor boar must be tested for CSF and held in isolation for at least 30 days before entering the semen collection center. 
</p>
<p>APHIS considers the EU control measures to be effective, despite the residual CSF reservoir in wild boar.  APHIS previously recognized the APHIS-defined EU CSF region as a single region for CSF in which control measures are harmonized and binding for all MS and for which appropriate restrictions on exports can be placed. The EU measures include regulating the entry of boars into an approved AIC, including testing and quarantine procedures, periodic routine serological surveillance for CSF in approved AICs and testing of all animals in an approved AIC with a restriction zone before lifting movement controls work together to prevent the incursion of the CSFV virus.  In addition APHIS has in place an additional 6 month period before exports of swine and swine products, including swine semen, from a restricted zone following the cleaning and disinfection of the last infected premises in the zone can be resumed.  </p>
<p>APHIS considers that the controls in place in both APHIS regulation and EU legislation and consistent with recognition of the APHIS-defined EU CSF region as a single region for CSF control, make it unnecessary for swine semen collected in approved semen collection center to be subject to a 40 day post collection holding period prior to export to the Unites States.  APHIS has concluded that swine semen imported from the APHIS-defined EU CSF region without a 40-day post collection period is at low risk for the introduction of CSFV into the US.</p>
<p><b>References</b>: 
</p>
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</p>
<p>2. APHIS (2007) Importation of Live Swine, Swine Semen, Pork and Pork Products from the Czech Republic, Latvia, Lithuania and Poland.  Final Rule. U.S. Department of Agriculture, Animal and Plant Health Inspection Service. Published November 28, 2007: 72 FR 67227.
</p>
<p>3. APHIS (2006). Final rule: Importation of swine and swine product from the European Union [Docket 02-046-2]. U.S. Department of Agriculture, Animal and Plant Health Inspection Service. Published May 19, 2006: 71 FR 29061-29072. 
</p>
<p>4. APHIS (2005) Importation of Swine and Swine Products From the European Union Proposed rule. U.S. Department of Agriculture, Animal and Plant Health Inspection Service. Published April 8, 2005: 70 FR 17928
</p>
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</p>
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</p>
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</p>
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</p>
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</p>
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</p>
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</p>
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</p>
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</p>
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</p>
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</p>
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