Inspection for Trichinella in the Eu - Food Safety or Export Concerns

The former 15 EU countries have been spending an estimated 570 million Euro yearly to inspect for Trichinella in pigs primarily raised on industrialized farms with negligible little risk of acquiring the parasite; human trichinellosis in the EU is generally caused by game meat, imported horse meat, or meat from local pigs raised outdoors. Occurrence of both pig and human trichinellosis has significantly higher prevalence in the newly associated eastern countries. Attempts are made to define Trichinella-free areas, but only certification of Trichinella-free pig production units/farms appears feasible. Because current serological detection methods are not suited for meat inspection, the classical direct detection methods and inactivation by freezing remain the methods of choice for inspection of pork in the new EU legislation, which is planned to go into force in early 2006. Automation of direct inspection methods may represent a cost effective alternative to certify pig farms free of Trichinella. Introduction Human trichinellosis is estimated to affect at least 11 million people globally, and based on the cost of previous outbreaks (Dupouy-Camet, 2000), the annual cost of the 3,0005,000 yearly human cases in EU (1990-2004) is many million Euro. Human trichinellosis have been increasing during the 1990s in the original EU member states, but especially so in the newly associated EU countries (Murrell and Pozio, 2000; Djordjevic et al., 2003). Almost exclusively the meat sources of infection in Europe have been horses, wild boar, and pigs bred on small farms or allowed to graze on open pasture (Pozio, 1998; Murrell and Pozio, 2000; Oivanen et al., 2002; Malakauskas et al., 2005). Most of such pigs (organic, ecological, free-ranging, etc.) are used for local or regional consumption only. Although animals for local and regional consumption has not required to be tested in the present EU legislation, but this will be changed in the future legislation. In addition, the illegal importation of infected pork and pork products has led to outbreaks of trichinellosis in Germany, Denmark, Italy and the UK (Pozio and Marucci, 2003; Hansen and Kristensen, 2004). As management scenarios differ widely in Europe, the typical management systems at risk in Western Europe are the free-range production and the small farm where pigs are raised for private consumption; in Eastern Europe it is the newly established private farms and the small backyard rearing which have gradually replaced the larger collective farms. The high number of infections in domestic pigs in east and central European countries represents a serious problem for the meat trade between EU countries, and most likely also for the general perception of the quality pig meat exported from the EU. Methods of Meat Inspection Although trichinoscopy, which is laborious, costly and not very sensitive, has gradually been replaced by artificial digestion methods in most industrialized slaughterhouses of Western Europe, it is still common many places in Central and East Europe, and in small slaughterhouses in Western Europe. The method does not detect the non-encapsulating T. pseudospiralis, which is widespread in European wildlife, representing a risk of infection of livestock in extensive production units as has occurred in farmed wild boars in Finland (Oivanen et al., 2002) and in a domestic pig herd in the Slovak Republic (Hurníková et al., 2005). Thus, the use of trichinoscopy as a method for Trichinella control in the EU will only be allowed as a transitional measure. Six artificial digestion methods have up to now been accepted by the EU, but in future legislation this number will be reduced to four: < The magnetic stirrer method (gold standard); < the “Stomacher” sedimentation method; < the “Stomacher” filtration technique; and < the “Trichomatic 35” automated digestion. These digestion methods are all very suitable for demonstrating Trichinella larvae in pork, but only the magnetic stirrer digestion has been subjected to validation studies (Forbes and Gajadhar, O R A L P R E S E N T A T IO N S 165 SafePork 2005 1999). All animals slaughtered in EU export accredited abattoirs should be examined according to one of these artificial digestion methods. The amount of meat that must be tested per animal in future is 1 g for pigs, 5 g for horses and wild boars, and 10 g for other game. Indirect (serological) test methods are at present not recommended as a substitute for direct (pooled sample digestion) methods of individual carcasses at slaughter (Gamble et al., 2000; 2004). Among others, serology cannot detect early infections in pigs (Kapel and Gamble, 2000). The sensitivity and specificity of such tests are obviously important for the validity of the test results, but the statistical predictive value of the test rely on the true prevalence in the population subjected to surveillance. In non-endemic areas, the positive-predictive value is extremely low and useless as a substitute for meat inspection. However, the negative predictive values in the same areas may be used for surveillance of farms under a pre-harvest control program (se below). Certification by Freezing (Only for Pork) Pork can be certified after freezing by either of three different methods, and in consideration of the size of the meat portions frozen. As larger pieces of meat have to be frozen for longer time periods (e.g. 20 days at -25°C), the procedure is a rather expensive substitute for inspection by digestion, but it may be suitable for meat that would anyway be sold frozen. In the future EU legislation, meat from wild boars, horses or game cannot be certified by freezing since they may hold cold tolerant species of Trichinella. Potentials for Pre-Harvest Control (Trichinella-Free Farming) The EU and USA have investigated strategies to limit meat inspection to pigs at risk (pigs on farms without rodent control and barriers to the surrounding fauna, pigs on pasture, etc). Before this can be realized, however, a system must be put in place which allows certification of pig farms as Trichinella-free, on the condition that they fulfill certain criteria. In the US, a pilot program for certifying pig herds is being conducted. In the future EU legislation, the following criteria (simplified) have been proposed for designating Trichinella-free pig farming: 1) All pigs, originating from certified breeders, are registered, identifiable at arrival and when leaving the farm; 2) production pigs never have access to pasture; 3) pig buildings are constructed to prevent rodents from entering and a rodent control program is enforced; 4) only feed from certified producers maintained in closed silos to prevent access by rodents is used; 5) waste food, containing meat products, is heated to inactivate Trichinella; 6) dead animals are disposed by sanitary means within 24 hours; and 7) introduced new animals originate from Trichinella-free farms or, alternatively, animals are held in quarantine and are examined serologically prior to introduction. In addition to the above “on-farm” requirements that have to be fulfilled by the operator of the farm, it will be a requirement that a competent authority shall periodically conduct audits ensuring that the farm meets the prescribed criteria. The same authority shall ensure that the individual Trichinella-free farm is monitored in a surveillance program, which verifies that pigs are indeed free of Trichinella. In addition, a risk based wildlife monitoring program on indicator animal species shall be conducted by an independent authority. Although the “on-farm” measures for certification and periodic audits are very similar between the US and EU initiatives, the surveillance of all individual Trichinella-free farms is not included in the US initiative. Instead, surveillance is conducted on a part of the national pig herd, which is less costly, but does not allow for any direct risk assessment in the Trichinella-free farming units. Also, the US initiative does not include regional monitoring programs of wildlife, which in the EU initiative provide data for the risk assessment on transmission from the surrounding fauna. Although risk of Trichinella transmission is eliminated in confined industrialized production, one single finding of Trichinella in animals raised in other management systems will presumably have a major impact on the export of animals from the same region, independently of its relative risk. For Trichinella-free farming such individual findings may exaggerate consumer perception of the risk much more than if pigs are individually inspected by meat inspection.