Wiener Tierärztliche Monatsschrift Veterinary Medicine ...

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Wiener Tierärztliche Monatsschrift – Veterinary Medicine Austria 99 (2012)

From the Department of Veterinary Medicine, Faculty of Agriculture, University of Novi Sad, Novi Sad, Serbia

Trichinella and trichinellosis in the European Union

S. BUNCIC

received August 1, 2012accepted for publication September 3, 2012

Keywords: pigs, horses, wild boar, meat inspection, meat safety.

Summary

The domestic pig is the most important source of human Trichinella infection in the European Union (EU) and worldwide. Trichinella epidemiology is com-monly de� ned by two cycles; ,domestic’ (in pigs on-farm) and ,sylvatic’ (in wildlife). In industrial indoor far-ming with good hygienic practices and ef� cient management including biosecurity (,integrated pro-duction’), Trichinella transmission via the domestic cycle is unlikely in the EU situation. In cases of of-� cially recognised Trichinella-free holdings or negli-gible Trichinella risk regions, testing for this parasite at meat inspection is not mandatory for slaughter pigs originating from integrated production. In other cases, testing of slaughtered pigs for Trichinella is a very important component of the current Trichinella control system. Recently, European Food Safety Au-thority (EFSA) has published scienti� c documents proposing generic Trichinella-related pork safety as-surance framework, the main elements of which in-clude: Trichinella-risk categorization of incoming pig batches; either testing of carcasses or their Trichinel-la-inactivation treatments in the case of higher risk batches; and neither testing nor treatments for low risk batches. In conjunction with this framework, EFSA also proposed Trichinella-related harmonized epidemiological indicators (HEI) to be used as the main mechanism for the risk categorisation and mo-nitoring by the risk managers (regulators). On the other hand, in endemic regions where the practice of producing home-made uncooked products from meats of uninspected domestic and/or wild pigs exists, it represents a major risk for human trichinello-sis. In such a situation, the farmers, the hunters and the consumers should be educated about trichinello-sis-prevention measures applicable in such a setting.

Schlüsselwörter: Schweine, Pferde, Wildschweine, Fleischuntersuchung, Fleischsicherheit.

Zusammenfassung

Trichinella und Trichinellose in der Europäischen Union

Das Hausschwein ist die wichtigste Quelle für Infektio-nen des Menschen mit Trichinella innerhalb der EU sowie weltweit. Die Epidemiologie von Trichinella kann man üb-licherweise durch zwei Zyklen charakterisieren: den „do-mestischen Zyklus“ (bei Hausschweinen auf dem Bauern-hof) und den „sylvatischen Zyklus“ (bei Wildtieren). Bei intensiver Tierhaltung mit Guter Hygienischer Praxis, ef� -zientem Management und insbesondere biologischer Si-cherheit („integrierte Produktion“), ist die Übertragung von Trichinella durch den domestischen Zyklus innerhalb der EU sehr unwahrscheinlich. Sofern amtlich Trichinella-freie Betriebe oder Regionen mit vernachlässigbarem Tri-chinella-Risiko festgestellt wurden, ist die Untersuchung auf diesen Parasiten bei der amtlichen Fleischuntersu-chung nicht mehr vorgeschrieben für Schlachtschweine aus integrierter Produktion. In allen anderen Fällen ist die Untersuchung auf Trichinella ein sehr wichtiger Bestand-teil des gegenwärtigen Trichinella-Kontrollsystems. Kürz-lich hat die EFSA wissenschaftliche Stellungnahmen ver-öffentlicht, die allgemeine Trichinella-bezogene Sicher-heitsmaßnahmen beinhalten. Die wesentlichen Elemente sind: die Risikokategorisierung von angelieferten Schlachtgruppen von Hausschweinen hinsichtlich Trichi-nella; entweder Untersuchung von Schlachttierkörpern auf Trichinella oder eine Behandlung zur Inaktivierung von Trichinella bei Gruppen mit höherem Risiko; weder Unter-suchung noch Behandlung bei Gruppen mit niedrigem Risiko. In Zusammenhang mit diesen Vorschlägen hat die EFSA vorgeschlagen, harmonisierte epidemiologische In-dikatoren (HEI) bezüglich Trichinella zu nutzen als die wichtigsten Hilfsmittel für die Risikokategorisierung und das Monitoring durch die Risikomanager (Gesetzgeber). Andererseits stellt die Trichinellose des Menschen ein be-sonderes Risiko dar in Regionen mit endemischem Trichi-nella-Vorkommen, in denen hausgemachte Lebensmittel, die nicht ausreichend erhitzt werden, aus dem Fleisch von nicht untersuchten Haus- oder Wildschweinen hergestellt werden. In solchen Fällen sollten die Bauern, die Jäger und die Verbraucher über Maßnahmen zur Verhinderung einer Trichinellose aufgeklärt werden.

Abbreviations: ECDC = European Centre for Disease Pre-vention and Control; EFSA = European Food Safety Autho-rity; EU = European Union; FCI = Food Chain Information; HACCP = Hazard Analysis and Critical Control Points; HEI = Harmonized Epidemiological Indicators; NBL = Newborn larvae

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IntroductionTrichinella spp. are meat borne infectious parasites

(nematode worms) transmissible from animals to man (zoonoses). Natural Trichinella infections in more than 100 species of mammals, seven avian species, and three reptile species have been reported (POZIO, 2005).

The genus Trichinella includes species T. spiralis T1, T. nativa T2 (and related genotype Trichinella T6), T. britovi T3 (and related genotypes Trichinella T8, T9), T. pseudospiralis T4, T. nelsoni T7, T. murrelli T5, T. papuae T10 and T. zimbabwensis T11 (EFSA, 2004; BUNCIC and MIRILOVIC, 2011). All the species of the genus are known to infect mammals (mostly carnivo-res), rodents and omnivores including pigs, and occa-sionally also herbivores (e.g. horses), but T. pseudo-spiralis also can infect birds and both T. papuae and T. zimbabwensis also can infect reptiles (EFSA, 2004). In pigs in Europe, T. spiralis is of the highest concern; followed by T. britovi and T. pseudospiralis.

Only the larval stage of the parasite is infectious; the infection occurs only via the ingestion of the mu-scle tissue containing the larvae (Fig. 1).

Human trichinellosis

The human disease

Humans infected with Trichinella can develop seri-ous symptoms and life-threatening disease. Although

the most important source of human infection world-wide is domestic pig, meats of wild boars and horses were also implicated in human trichinellosis outbreaks over the past few decades (EFSA, 2004). Overall, a majority of all cases of human trichinellosis worldwide have been caused by consumption of pork. Because human Trichinella infection usually occurs after in-gestion of raw/undercooked meats and meat pro-ducts, it is strongly associated with eating habits and tradition in respect to preparation of traditional dishes based on raw or undercooked meat or raw meat-de-rived products (GOTTSTEIN et al., 2009). Furthermo-re, exposure to Trichinella is higher in hunters and their social associates if the raw game meat is not tested for the parasitic larvae before consumption. The important trichinellosis epidemiological factors also include: ever increasing human migrations world-wide as it can lead to wider spread of certain ,risky practices’ with food (e.g. consumption of raw meats/meat products); importation of non-controlled meat from endemic to non-endemic countries; and intro-duction of new food preparation practices involving raw meat (GOTTSTEIN et al., 2009).

The seriousness of Trichinella infection in humans depends on the number of ingested viable larvae. The infection can be asymptomatic in cases of ingestion of only a low number of larvae, but ingestion of larger numbers of larvae (e.g. hundreds) results in clinical symptoms of the disease. There are basically two dif-ferent groups of symptoms in humans, according to

the lifecycle of this parasite. When meat containing Trichinel-la larvae (� rst larval stage, L1) is ingested, larvae are released due to the action of pepsin and hydrochloric acid in the sto-mach. The L1 larvae arriving in the duodenum develop via L2, L3 and L4 stages into the adult male and female parasites within around two days. During this de-velopment, parasitic stages are already embedded in the intesti-nal mucosa and the human host will experience gastroenteritis (diarrhoea, abdominal pain; the ,intestinal phase’). After copula-tion, female adult worms release newborn larvae (NBL), which en-ter the lymphatic and blood ves-sels of the host. With the blood stream, NBL are transported to striated skeletal muscles, which are their de� nite location. The NBL penetrate into muscle cells (which are then transformed into ,nurse cells’), and develop into the infective L1 stage. Migrating Fig. 1: Life cycle of Trichinella (Source: http://www.dpd.cdc.gov/dpdx)

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NBL provoke a range of immunological, pathological and metabolic disturbances in the human host, resulting in various acute clinical manifestations (the ,muscular phase’). These acute stage reactions can be followed by chronic-stage trichinellosis (GOTTSTEIN et al., 2009).

Human trichinellosis can be successfully treated, but only when the therapy with antihelmintics (e.g. al-bendazole and mebendazole) is applied very early so to eliminate the larval or adult stages of Trichinella sp. during the intestinal phase. On the other hand, once the NBL reaches the striated muscles and becomes encysted there (advanced disease phase), the effects of the therapy are poorly elucidated to date. In most trichinellosis patients, the symptoms disappear within two to six months, but heavy infections may be fatal in spite of therapy i.e. the lethality may be up to 5% (GOTTSTEIN et al., 2009).

The occurrence of human trichinellosis in EU

Human trichinellosis commonly occurs in the form of outbreaks rather than sporadic cases, and the EU situation is brie� y indicated below using data reported through the EU monitoring system for zoonoses and zoonotic agents and published by EFSA/ECDC (2012).

In the EU in 2010, a total of 13 Trichinella out-breaks were reported by three member states, out of which six (comprising 77 cases in total) occurred in Lithuania. For the Trichinella outbreaks, 27.5% of all cases were hospitalised, with no fatalities repor-ted. The number of Trichinella outbreaks in the EU decreased in 2010 compared with 2009, mainly due to the decrease in the outbreaks reported by Ro-mania – from 31 in 2009 to just three in 2010.

In the EU in 2010, a total of 394 cases of human trichinellosis were reported, out of which 223 cases (0.5 per 100,000 population) were con� rmed inclu-ding three imported cases. The difference between total reported cases and con� rmed human cases is due to the fact that, in outbreaks, only some cases among those showing clinical signs of trichinellosis are laboratory con� rmed whilst the remaining are considered as epidemiologically linked to the con� r-med cases. Interestingly, the number of human trichi-nellosis cases (394) in the EU in 2010 decreased al-most 2-fold as compared with 748 cases reported in 2009. Among EU member states, the highest inciden-ces of human trichinellosis were reported in Romania followed by Lithuania; together these comprised 71.3% of all con� rmed EU cases.

Consumption of pork was the main suspected ve-hicle in 90.1% of con� rmed EU trichinellosis cases in which the source was reported; other meat and other wild/game meat accounted for the remainder. Among those con� rmed human cases for which information on Trichinella species was provided, 58.5% was caused by T. spiralis and no cases due to T. nativa or T. pseudospiralis were reported.

Trichinella in animals

Transmission in animal populations

Normally, infected animals do not show clinical signs of the disease. Therefore, in most European countries, slaughtered pigs, horses, wild boar and other wildlife intended for human consumption are tested for Trichinella at meat inspection. Trichinella transmission in animals is commonly de� ned by two cycles; ,domestic’ and ,sylvatic’. The domestic and sylvatic cycles can function either independently from each other or interactively (POZIO, 2007).

Domestic Trichinella cycle The domestic cycle involves domestic pigs that can become infected through feeding on not/under-cooked swill, scraps and other organic wastes that contain pork, and/or improperly disposed carrion, and/or synanthropic animals such as rodents. It is considered (EFSA, 2005b) that Trichinella transmissi-on via the domestic cycle is unlikely in industrial – particularly indoor – farming systems. The reason is because such systems involve application of ef� cient biosecurity measures and good hygienic practices preventing or greatly reducing the chances of Trichi-nella transmission to domestic pigs. However, where such control measures do not exist or are poorly im-plemented, e.g. on small farms with pigs raised out-doors or having access to the outdoors, the domestic cycle becomes a very important scenario for Trichi-nella transmission.

Sylvatic Trichinella cycle The sylvatic cycle involves wildlife hosts i.e. a range of wild carnivorous and omnivorous animal species. Among the wildlife, Trichinella is transmitted through feeding on prey animals containing the larvae, and/or infested carrion of the same species (,cannibalism’), and/or infested carrion of other species. Namely, Tri-chinella larvae can survive in decaying muscles of dead animals for long time and be viable and infective at the moment of ingestion of the muscles by the next host.

Interaction between domestic and sylvatic cyclesIn situations where improper management in segre-gating animal husbandry and wildlife exists, a switch from wild animals to domestic animals can occur (GOTTSTEIN et al., 2009). This interaction between the cycles usually leads to increases in Trichinella oc-currences in susceptible food animals and, conse-quently, in humans. The risk of such between-cycles interaction can be – directly or indirectly – increased with increasing globalization including more extensi-ve movements of livestock, food and people. Theglobalization can bring problems with maintaining the traceability and the completeness/reliability of the

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food chain information e.g. on production systems and biosecurity levels on farms where pigs/meat ori-ginate, which all can cause problems in international meat trade.

Other differences between the Trichinella cyclesSome other aspects can also differ between dome-stic and sylvatic cycles. For example, some reports indicate that the Trichinella infective dose for pigs is higher (around 50,000) than for foxes (around 500 lar-vae), and that the average larval burden in an infected host is higher in pigs (around 950) than in foxes (around 20) (OLSEN et al., 1964; KAPEL et al., 1995). In other words, it seems that the infectivity can vary with Trichinella species-animal species combinations and can differ between pigs and wild animals (Tab. 1).

The EU situation in respect to occurrence of Trichi-nella in animal populations is brie� y indicated below using data reported through the EU monitoring sys-tem for zoonoses and zoonotic agents and published by EFSA/ECDC (2012).

Trichinella in animals intended for food in the EUAccording to Commission Regulation (EC) No 2075/2005, carcasses of domestic swine, horses, wild boar and other farmed or wild animal species su-sceptible to Trichinella infestation are systematically sampled at slaughter as part of meat inspection and tested for Trichinella. Thus, most of the reported data are derived from meat inspection.

In the EU in 2010, Trichinella was found in a total of 199 domestic pigs out of 211.378,305 tested pigs (0.00009% positive). For positive domestic pigs, their origin was reported either as non-controlled housing

conditions or was not speci� ed. The majority of Tri-chinella � ndings in domestic pigs in EU in 2010 were from Romania, but positive � ndings have been decre-asing in recent years in that country.

In respect to farmed wild boar, 26 were reported as positive among 36,871 tested (0.07%) in the EU in 2010, which was around a 777-fold higher occurrence than in domestic pigs during the same period. Among hunted wild boar, 988 were reported as positive out of 724,640 tested (0.14%) in the EU in 2010, which was a 2-fold higher occurrence than in farmed wild boar and around 1,555-fold higher than in domestic pigs during the same period.

In respect to slaughtered solipeds, most of data re-ported in EU in 2010 were related to horses but some data also to unspeci� ed solipeds; only in one country (Italy) data also related to donkeys. In total, 159,213 solipeds were tested, and only Bulgaria and Romania reported one Trichinella-positive horse each.

Trichinella in wildlife other than wild boarThe main source of data for those wild animal species is the monitoring of Trichinella in wildlife. In the EU in 2010, the highest reported occurrence of Trichinella in the most commonly reported wildlife species was in racoon dogs (27.9% positive out of 208) followed by bears (4.8% out of 589) and foxes (1.1% out of 9,569). Some Trichinella positive � ndings were also reported for other wildlife species: badgers, birds (including falcons, goshawks and eagles), coypu, deer, lynx, martens, minks, mou� on, otters, rats, seals, stoats, wolverines, wolves, and unspeci� ed wild animals; making a combined occurrence of 3.6% among 2,761 tested.

Trichinella species

Domestic animals Wildlife Birds

Pigs Horses Wild boars Rats Foxes

T. spiralis +++* +++ +++ +++ +++ -

T. nativa - ? + + +++ -

T. britovi ++ + ++ ++ +++ -

T. pseudospiralis + ++ ++ ++ +++ +

Tab. 1: Trichinella infectivity variations in animals (adapted from KAPEL and GAMBLE, 2000; TRICHIPORSE, 2005; EFSA, 2005a)

*Infectivity: +++ highest; + lowest; - negligible

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Trichinella control measures along the meat chain

On farm control measures

Wildlife-related control measuresWhere Trichinella is present in wildlife, the likelihood of the contacts between domestic pig and wildlife will determine the risk caused by the wildlife reservoir. Surveillance of wildlife reservoirs is usually based on collecting and testing foxes, but it may include ra-coon dogs in some areas. Nevertheless, there arelarge variations in Trichinella prevalence in wildlife even within individual countries. Furthermore, due to mobility of wildlife and other variable factors, the geo-graphical area to which one wishes to make inferen-ces on the prevalence in wildlife based on wildlife sur-veys is dif� cult to de� ne (EFSA, 2005b). Overall, monitoring of a wildlife reservoir can be helpful in as-sessing its potential as source for Trichinella exposu-res of domestic pigs, and in considering any related risk-reduction measures. However, there are dif� cul-ties in using wildlife monitoring to verify the absence of Trichinella in wildlife.

It appears that the only measure that can be imple-mented to reduce the prevalence of infection among wildlife is to instruct hunters to avoid leaving animal carcasses and/or entrails in the � eld; a practice which increases the probability of transmission to new hosts (GOTTSTEIN et al., 2009). Furthermore, continuous rodent control in the areas/locations enabling dome-stic pig exposure is another very important aspect of Trichinella reservoir control.

Farming system-related control measuresThere are three main types of pig operations in the EU: integrated farms, piglet producing farms and fat-tening farms (EFSA, 2005b). On integrated farms,birth, weaning and fattening of pigs occur in the same farm. On piglet producing farms, birth and weaning (about 45–60 days, i.e. up to about 25 kg) occur on a farm and then pigs are moved to a fattening or inter-mediate farm. On fattening farms, pigs are introduced at about 25 kg and raised for slaughter. The period in the fattening farms and slaughter weight will vary considerably from country to country and type of production system. It is also possible that the piglet is � rst moved to an intermediate farm (for three to four months) and then thereafter to a � nishing farm (for about four months).

The overall risk of transmission of Trichinella to pigs in the case of industrialized indoor farms is very small (EFSA, 2005b), and particularly on those farms that satisfy criteria set for ’controlled housing conditions and integrated production systems’ as de� ned accor-ding to the food chain information (FCI) and indicated in related regulations (Regulation (EC) No 1244/2007). This is due to application of a range of Trichinella risk-

reduction measures, among which the particularly important ones are: chances of contacts of domestic pigs with wild omnivores/carnivores are reduced to minimum through indoor housing and ef� cient biose-curity; and exposure of pigs is also reduced to mini-mum through exclusion of uncooked meat-containing materials from the feed (good farming/hygiene practi-ce) (SCVMRPH, 2001). Where such risk-reduction measures are lacking or insuf� cient (e.g. outdoor, ex-tensive or backyard raised animals), the risk of trans-mission of Trichinella to pigs/farmed boar is certainly higher (EFSA, 2005b).

In respect to potential for the vertical transmission of Trichinella from sows to piglets, in an experimental study involving oral infection of sows during gestation and testing of their offspring, no larvae were reco-vered from piglets or foetuses (WEBSTER, 2003). Hence, the vertical transmission risk is considered as negligible (EFSA, 2005b).

However, in the case where T. spiralis is present in the environment, rodents may transmit the infection to piglets, even those that are not weaned; this risk for piglets would be correlated with the risk for sows and boars on the premises.

Risk categorization of regions and related moni-toring/surveillance In a recent scienti� c report published by EFSA (PO-ZIO et al., 2010), an improved system for categorizati-on of farming regions including applicable Trichinella monitoring/surveillance is proposed, the main as-pects of which are extracted below. The proposed monitoring scheme relies on ’compartmentalisation’ to identify regions and categories of animals at lower risk of Trichinella in which reduced testing could be carried out without compromising public health.

Region 1: ,Endemic’ – Trichinella is present and circulating in livestock and wildlife unless proven otherwise. In countries where Trichinella is circula-ting, all Trichinella-susceptible animals destined for human consumption should be tested by arti� cial di-gestion, according to the EC Regulation (EC) No 2075/2005. If all animals for consumption are monito-red, there is considered to be little extra bene� t in the monitoring of other wildlife. In this situation other wildlife does not need to be monitored - but wildlife should still be tested if it is destined for human con-sumption. In this category, individual holdings may apply for Trichinella-free certi� cation in accordance with current EC Regulation (EC) No 2075/2005.

Region 2: ‚Low-risk’ – This region does not fall in line with current EC regulations and is a newly propo-sed category. ’Low-risk’ refers to the risk of Trichinel-la in fattening pigs from controlled housing. Regions in this group must provide evidence that the surveil-lance sensitivity is 95% or greater in fattening pigs from controlled housing. All sows and boar, plus fat-tening pigs from outdoor and non-controlled indoor

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housing and wildlife for human consumption should still be tested as stipulated under EC Regulation (EC) No 2075/2005. Once an area has been granted low risk status, a statistically signi� cant sample of fatte-ning pigs from controlled housing should be samp-led. Sampling should be strati� ed by slaughterhouse throughput to ensure a representative sample of the population.

Region 3: ,Negligible risk’ – This category compri-ses 3a and 3b subcategories. In 3a subcategory, re-gions in which there is negligible risk that Trichinella is present in the de� ned livestock population should submit evidence that there is negligible risk that Tri-chinella is present in the controlled fattening pig po-pulation, given the design prevalence of less than one per million. One method of providing this evidence is to show that the sensitivity of the surveillance in pigs from controlled housing is high e.g. 99%. In 3b sub-category, the region should submit evidence that the likely occurrence of Trichinella in the controlled-housing pig population is less than one per million and furthermore the criteria are ful� lled as set out in Regulation (EC) No 2075/2005. One method of provi-ding this evidence is to show that the sensitivity of the surveillance in pigs is high e.g. 99%. In either 3a or 3b status, fattening pigs from farms that comply with the de� nition of controlled housing do not require testing. Sows and boar from these farms will all need to be tested. Furthermore, wildlife meant for human con-sumption needs to be tested in accordance with cur-rent Community legislation.

At-abattoir control measures

Current EU of� cial meat inspection in respect toTrichinella

The current Trichinella controls at abattoir level in the EU are according to the Commission Regulation (EC) No 2075/2005 laying down speci� c rules on of� cial controls for Trichinella in meat. For the purposes of the Regulation, ,Trichinella’ means any nematode be-longing to species of the genus Trichinella, and meat from animals infested with larvae of any Trichinella species is to be declared un� t for human consumpti-on (Regulation (EC) No 854/2004).

Carcasses of domestic swine should be systemati-cally tested for Trichinella in slaughterhouses as part of the post mortem examination. However, those fat-tening pigs that come: a) from holdings of� cially re-cognised by the competent authority as Trichinella-free; or b) from a region where the risk of Trichinella in domestic swine is of� cially recognised as negligible; are exempt from the Trichinella testing. For recogniti-on of these holding- or region-related categories, speci� c conditions enlisted in the Regulation must be met. Nevertheless, the Regulation states that such recognition is only feasible in Member States with a history of very low disease prevalence.

Furthermore, carcasses of horses, wild boar and

other farmed and wild animal species susceptible to Trichinella infestation should also be systematically tested in slaughterhouses or game-handling estab-lishments as part of the post mortem meat inspec-tion. Such testing does not have to be carried out where the competent authority has ascertained by risk assessment that the risk of Trichinella infestation of a particular farmed or wild species is negligible.

To prevent any potential spread of Trichinella larvae from abattoir to outside, the regulations require that carcasses and other parts of an animal intended for human or animal consumption that contain striated muscle tissue must not leave the premises before the negative result of the Trichinella examination. On the other hand, animal waste and animal by-products not intended for human consumption and not containing striated muscle may leave the premises before the Trichinella result, but the competent authority may re-quire a Trichinella testing or prior inactivation treat-ment before giving the permission.

Trichinella-related meat safety assurance frame-work proposed by EFSA

In the recent EFSA Scienti� c Opinion on revision of meat inspection in swine (EFSA, 2011a), Trichinella is ranked as a pork-borne hazard of medium priority (comparably, Salmonella is high priority) requiring de-velopment and implementation of speci� c control measures. A generic carcass meat safety assurance framework was described in the Opinion, the main points of which are extracted below. The at-abattoir strategy to achieve the target of no viable forms of Trichinella in the � nal pork carcasses is based on two main elements, as illustrated in Figure 2:

a) risk-categorisation of incoming pig batches in respect to the parasites before slaughter; and

b) application of measures to control presence or infectivity of the parasites in meat during the abattoir process.

This meat safety assurance framework proposed by EFSA is currently being considered by the Euro-pean Commission, as to whether and when it should be converted into new EU legislation.

The low risk batches of incoming pigs in respect to Trichinella could be slaughtered and processed wit-hout application of Trichinella-control measures in abattoirs, as long as the allocation of the low risk ca-tegory to the batches was based on: i) suf� cient and reliable FCI including Trichinella historical testing data; and ii) application of hazard-speci� c harmo-nised epidemiological criteria (see below); so that both ensure that there is no Trichinella in � nal carcas-ses.

In contrast, the higher risk batches of incoming pigs in respect to Trichinella would have to be subjected to additional post-slaughter measures ensuring the ab-sence of their viable forms in meat. These post-slaughter measures may be based on: a) carcass

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Fig. 2: Main elements of generic pork (carcass) safety assurance with respect to Trichinella (adapted from EFSA, 2011a)

Meat freezing inactivation of T. spiralis Meat cooking inactivation of T. spiralis

Core temperature (°C) Required duration Core temperature (°C) Required duration

-17.8 106 hours 49.0 21 hours

-20.6 82 hours 50.0 9.5 hours

-23.3 63 hours 52.2 2 hours

-26.1 48 hours 54.5 30 minutes



-34.5 8 hours 60.0 1 minute

-37.2 0.5 hours 62.2 instantaneous

Tab. 2: Inactivation of Trichinella spiralis by freezing and cooking (adapted from EFSA, 2004)

sampling and laboratory Trichinella examination, in the same manner as described in the current EU re-gulations; or b) on heat or freezing treatments that ensure complete inactivation (killing) of the larvae in the meat (Tab. 2). The treatments can be applied: i) post-chilling but pre-boning of carcasses; or ii) post-boning. The latter option may be problematic in res-pect to ensuring full traceability and that every – even the smallest – piece of meat separated during boning

is subjected to the inactivation treatment. Where the treatments are used, their time-temperature parame-ters must be speci� ed and their effectiveness valida-ted, monitored and veri� ed within the HACCP-based meat safety system.

When setting the criteria de� ning lower or higher Trichinella risk categories – which is a risk manage-ment/regulatory responsibility – analysis of FCI and corresponding Harmonized Epidemiological Indica-

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tors (HEI), related sampling plans and methods for each of the hazards need to be taken into account. They are described in related EFSA’s Scienti� c Re-port (EFSA, 2011b), the main points of which are ext-racted here and summarized in Tab. 3.

The lack of Trichinella infection in domestic pigs from of� cially recognised controlled housing condi-tions in the EU and the sporadic circulation of these parasites, mainly in free-ranging and backyard pigs of less than one quarter of the Member States, deter-mines that, in domestic pigs destined for human con-sumption, the HEIs are based on a single main risk factor: the type of production system.

HEI 1 and 2 (indicated in Tab. 3) target domestic pigs of all ages slaughtered for human consumption that do not originate from of� cially recognised controlled housing conditions. The testing of these pigs takes place in slaughterhouses using the magnetic stirrer method for pooled-sample digestion and would re� ect the Trichinella status of the farms. Testing the pigs by serology using an ELISA method is not proposed due to the high number of false positive test results (cross-reactions) caused by the presence of other parasitic infections and the risk of some false negative test re-sults in animals with a low infection level (EFSA, 2011b). The use of the western blot method to con� rm the ELISA-positive sera is regarded as too expensive. Fur-thermore, the use of the muscle juice samples instead of serum samples is not a suitable alternative due to

the lower concentration (about ten times less) of anti-bodies in the muscles than in the serum (EFSA, 2011b). However, ELISA tests on pig serum may be useful in monitoring Trichinella spp. infection in domestic pigs moved from a lower to a higher status farm i.e. pigs originating from a non-of� cially recognised Trichinella-free farm that are introduced into an of� cially recogni-sed Trichinella-free farm (EFSA, 2011b).

Available data demonstrates that the risk of Trichi-nella spp. infection of pigs from of� cially recognised controlled housing conditions is negligible. For this reason, HEI 3 (Tab. 3) proposes audits of the housing and biosecurity standards of the farm.

HEI 4 (Tab. 3) targets wildlife in order to address the risk of transmission of infection from wild animals to pigs. The main animal species covered are wild boars and bears intended for human consumption, since meat from these species is addressed by meat ins-pection. Other susceptible, carnivore mammal wild-life species can be covered depending on the rele-vant wildlife population of a country.

The above mentioned HEIs can be used alone or in different combinations depending on the risk manager’s decision and the epidemiological situation.

Domestic/consumer level measures

Raw/undercooked pork and raw/uncooked products thereof, originating from pigs in endemic regions that have not been tested for Trichinella – for whatever

Indicators (animal/ food category/other) Food chain stage Analytical /diagnostic method Specimen

HEI 1: Trichinella in free-range and backyard pigs (both fattening and breeding pigs)

slaughterhouse arti� cial digestion1 meat

HEI 2: Trichinella in pigs from non- of� cially recognised controlled housing conditions (both fattening and breeding pigs)

slaughterhouse arti� cial digestion1 meat

HEI 3: Farms with of� cially recognised controlled housing conditions and Trichinella free status1

farm auditing

HEI 4: Trichinella in wildlife (e.g. wild boar, bear, raccoon dog, fox, jackal, wolf, lynx, wild cats, genet, mustelids)

environment arti� cial digestion1 meat

Tab. 3: Harmonised epidemiological indicators (HEI) for Trichinella (EFSA, 2011b)

1 For example, according to the Commission Regulation (EC) No 2075/2005.

345


ReferencesBUNCIC, S., MIRILOVIC, M. (2011): Trichinellosis in wild and

domestic pigs and public health; a Serbian perspective. In:PAULSEN, P., BAUER, A., VODNANSKY, M., WINKELMAYER, R., SMULDERS, F.J.M. (eds.). Game Meat Hygiene in Focus: Microbiology, Epidemiology, Risk Analysis and Quality Assu-rance. Wageningen Academic Publishers, Wageningen, The Netherlands, p. 143–156.

EFSA (2004): The suitability and details of freezing methods to allow human consumption of meat infected with Trichinella or Cysticercus. The EFSA Journal 142, 1–51.

EFSA (2005a): Risk assessment of a revised inspection of slaugh-ter animals in areas with low prevalence of Trichinella. The EFSA Journal 200, 1–41.

EFSA (2005b) Feasibility of establishing Trichinella–free areas, and if feasible on the risk increase to public health of not exami-ning pigs from those areas for Trichinella spp. The EFSA Journal 277, 1–37.

EFSA (2011a): Scienti� c Opinion on the public health hazards to be covered by inspection of meat (swine). The EFSA Journal 9(10), 2351.

EFSA (2011b): Technical speci� cations on harmonised epidemio-logical indicators for public health hazards to be covered by meat inspection of swine. The EFSA Journal 9(10), 2371.

EFSA/ECDC (2012): Trichinella. In: European Food Safety Au-thority, European Centre for Disease Prevention and Control; The European Union Summary Report on Trends and Sources of Zoonoses, Zoonotic Agents and Food-borne Outbreaks in 2010; The EFSA Journal 10, 2597. 243–255.

GARI–TOUSSAINT, M., TIEULIE, N., BALDIN, J.L. (2004): Trichi-nellose a Trichinella britovi dans les Alpes-Maritimes apres con-sommation de viande de sanglier congelee, automne 2003. Bull Epidemiol Hebd 21, 87–88.

GOTTSTEIN, B., POZIO, E., NOCKLER, K. (2009): Epidemiology, Diagnosis, Treatment, and Control of Trichinellosis. Clin Micro-biol Rev 22, 127–145.

KAPEL, C.M.O., GAMBLE, H.R. (2000): Infectivity, persistence, and antibody response to domestic and sylvatic. Trichinella spp. in experimentally infected pigs. Int J Parasitol 30, 215–221.

KAPEL, C.M.O., HENRIKSEN, S.A., BERG, T.B., NANSEN, P. (1995): Trichinella infections in arctic foxes from Greenland: stu-dies and re� ections on predilection sites of muscle larvae. Int J Helmintol 69, 325–330.

OLSEN, B.S., VILLELLA, J.B., GOULD, S.E. (1964): Contribution of Trichinella spiralis in muscles of experimentally infected swine. J Parasit 50, 489–495.

POZIO, E. (2005): The broad spectrum of Trichinella hosts: from cold– to warm–blooded animals. Vet Parasitol 132, 3–11.

POZIO, E. (2007): World distribution of Trichinella spp. infections in animals and humans. Vet Parasitol 149, 3–21.

POZIO, E., ALBAN, L., BOES, J., BOIREAU, P., BOUÉ, F.,

CLAES, M., COOK, A.J.C., DORNY, P., ENEMARK, H., VAN DERGIESSEN, J., HUNT, K.R., HOWELL, M., KIRJUSINA, M., NÖCKLER, K., ROSSI, P., SMITH, G.C., SNOW, L., TAYLOR, M.A., THEODOROPOULOS, G., VALLÉE, I., VIEIRA-PINTO, M.M., ZIMMER, I-A. (2010): Development of harmonised sche-mes for the monitoring and reporting of Trichinella in animals and foodstuffs in the European Union. Scienti� c Report sub-mitted to EFSA, 12th February 2010. European Food Safety Authority, Parma, Italy.

POZIO, E., VARESE, P., GOMEZ MORALES, M.A., CROPPO, G.P., PELLCCIA, D., BRUSCHI, F. (1993): Comparison of human tri-chinellosis caused by Trichinella spiralis and by Trichinella bri-tovi. Amer J Trop Med and Hyg 48, 568–575.

SCVMRPH (2001): The Opinion of the Scienti� c Committee on Veterinary Measures relating to Public Health on Trichinellosis, epidemiology, methods of detection and Trichinella–free pig production - Adopted 21st–22nd November 2001.

TRICHIPORSE (2005): European Commission, Health and Consu-mer Protection Directorate–General, Project ’TrichiPorse: Safe pork and horse meat on EU markets – early and unbiased dia-gnostic tests for Trichinella’. Quoted by EFSA (2005a): EU con-tract (QLRT-2000–01156), and NAS extension with Lithuanian partner (01/02/2003).

WEBSTER, P. (2003): Infection biology of Trichinella – with spe-cial emphasis on vertical transmission and the intestinal sta-ge. PhD Thesis, Danish Centre for Experimental Parasitology, The Royal Veterinary and Agricultural University. Copenhagen, Denmark.

Legal regulationsRegulation (EC) No 854/2004 of the European Parliament and of

the Council of 29th April 2004 laying down speci� c rules for the organisation of of� cial controls on products of animal origin in-tended for human consumption Of� cial Journal of the European Union L 226:83-127.

Commission Regulation (EC) No 2075/2005 of 5th December 2005 laying down speci� c rules on of� cial controls for Trichinella in meat. Of� cial Journal of the European Union L 338:60-82.

Commission Regulation (EC) No 1244/2007 of 24th October 2007 amending Regulation (EC) No 2074/2005 as regards implemen-ting measures for certain products of animal origin intended for human consumption and laying down speci� c rules on of� cial controls for the inspection of meat

Corresponding author´s address:Sava Buncic, Department of Veterinary Medicine, Faculty of Agriculture, Trg D. Obradovica 8, 21000 Novi Sad, Serbia e-Mail: [email protected]

reason – should preferably not be consumed by the consumer. This situation is of particular interest in en-demic countries with higher proportions of small-scale(,backyard’) pig farming, and where a cultural habit exists of preparing uncooked meat products under do-mestic (uncontrolled) arrangements, using meat from uninspected ,backyard’ pigs or even hunted wild boar (BUNCIC and MIRILOVIC, 2011).

Although all feasible efforts should be made to dis-courage the ,home-making of raw products from un-inspected pork’ practice, certain cultural preferences and/or various negative socio-economic factors and/or lack of proper information can make total eliminati-on of such practices unrealistic in the short-to-

medium term in some countries. As an important pre-ventative measure in the meantime, the farmers, the hunters and the consumers should be educated and advised: to freeze the pork (including from wild boars) before its further home-processing into uncooked products, or; to cook the product before consumpti-on, or both (BUNCIC and MIRILOVIC, 2011). With res-pect to home-made fermented, dry sausages (sala-mis) where cooking either before or after preparation is traditionally unacceptable for sensory qualities rea-sons, but where the Trichinella-inactivation effects of the curing are unreliable, the advice to keep the sau-sages in the freezer for some time before consump-tion would be bene� cial.

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