SRPSKO VETERINARSKO DRUŠTVO FAKULTET VETERINARSKE MEDICINE ZBORNIK RADOVA I KRATKIH SADRŽAJA 17. SAVETOVANJE VETERINARA SRBIJE (sa medunarodnim ucešcem) Zlatibor 7. -10. septembar 2005. godine
Kratak sadržaj KONTROLA ZOONOZA NA FARMI Branka Vidic, R.Kljajic Kontrola zoonotskih agenasa kod životinja i ptica kao rezervoara infekcije ima za cilj redukciju rizika u sistemu kontrole bezbednosti hrane u okviru proizvodnje. kao i u ostalim fazama lanca ishrane. Proizvodnja i održavanje zdravog stocnog fonda zahteva dobru praksu prilikom uzgoja, što ukljucuje selekciju i veterinarsku kontrolu. Kljucni polazni faktor je hranivo, kao izvor hranljivih materija, bez prisustva patogenih organizama, i kao izbalansirana ishrana koja obezbeduje zdrav stocni fond. Bezbedna voda, odgovarajuca kontrola štetocina i divljih životinja kao i optimalna životna sredina u kojoj je stres sveden na minimum, predstavljaju vrlo bitne preduslove za dobro iskorišcavanje životinja. Farme nisu sterilna sredina i aktivnosti za smanjenje rizika od zoonoza moraju biti prakticne. ekonomski prihvatljive i fleksibilne, u zavisnosti od mogucnosti ozgajivaca. vrsta životinja koje se uzgajaju i epizootiologije samih zoonotskih agenasa u odredenim geografskim regionima. Edukacija farmera i uzgajivaca je kljucni momenat za uspešnu kontrolu zoonoze na farmi i to u smislu formiranja svesti o znucaju sprovodenja kontrolnih mera i o nacinu njihove primene, što ce dovesti do bolje uskladenost sa usvojenim protokolima i procedurama.ovakvo» shvatanje predstavlja prvi korak ka implementaciji longitudinalno integrisanog f pristupa obezbedenja zdravstveno ispravne hrane i kontroli zoonoza na farmama. ' Kljucne reci: biološka sigurnost, epizootiologija, zdravlje zapata, kontrola zoonoze Uvod Osigurati da hrana bude bezbedna od rizika koji sa sobom nose zoonotski agensi zahteva kontinuiranu kontrolu tokom celog procesa proizvodnje - od farme do trpeze. Da bi se smanjio rizik u sistemu upravljanja duž celog lanca ishrane vrlo je vazno da sve procedure mogu razumno, prakticno i ekonomicno da se primene na farmi. Zdravlje životinja koje su namenjene za ljudsku ishranu bezuslovno je povezano sa proizvodnjom zdravstveno ispravne hrane, dakle sa zdravljem ljudi. Povecanje broja stoke kao i intenzivniji promet u cilju komercijalne aktivnosti na globalnom tržištu hrane, pružaju mogucnost za nastanak i transmisiju infektivnih agenasa. Globalna distribucija hrane za životinje omogucava diseminaciju patogenih agenasa u odredene geografske oblasti, na pojedine farme i projemcive vrste životinja koje ranije nisu bile izložene tim agensima. Takode, promet i transport stoke izmedu farmi i razlicitih zemalja pogoduje širenju bolesti.
Zbornik radova i kratkih sadrzaja Potrošaci zahtevaju zdravstveno ispravnu hranu visokog kvaliteta, proizvedenu na nacin koji ne ugrožava životnu sredinu i uz maksimalno poštovanje standarda. Farme nisu sterilna sredina, ipak, podrazumeva se da stoka dobija bezbedno hranivo, vodu, optimalne uslove smeštaja i veterinarsku negu, da se poštuju standard! vezani za uklanjanje otpadnih materija, kao i da se vrši kontrola divljih životinja.postoje primarne bio-sigurnosne mere, zasnovane na proceni rizika. koje smanjuju incidenciju vecine zoonotskih agenasa i primenljive su u razlicitim subjektima koji se bave farmskim uzgojem životinja(2,3). Ipak, neke organizacije i zemlje zahtevaju dodatnu kontrolu u zavisnosti od epizootiologije zoonotskog agensa na njihovom podrucju i od intenziteta farmske aktivnosti.konstantno obezbedenje zdravstveno ispravnih proizvoda zahteva dobru komunikaciju izmedu institucija koje vrše procenu rizika, zakonodavnih ustanova i agencija za bezbednost hrane na globalnom nivou. Multidisciplinarni pristup u koji su ukljuceni svi cinioci u lancu ishrane dace i optimalne rezultate. Svi noviji medunarodni trgovinski sporazumi naglašavaju znacaj analize rizika i primene, u celom lancu ishrane, sistema prevencije zasnovanih na analizi hazarda i kriticnim kontrolnim tackama (6, 10). Dostignuca u biotehnologiji, narocito ona koja se odnose na razvoj brzih metoda za detekciju neželjenih kontaminanata, bioloških ili druge vrste, obezbeduju nov i praktican pristup sistemu obezbedenja zdravstvene ispravnosti hrane na osnovu statistician programa uzorkovanja, internih sistema kontrole kvaliteta i pravovremenih povratnih informacija prema farmama(7). Uredba o bezbednosti hrane Evropske komisije (3) potvrdila je neophodnost naucne zasnovanosti odluka koje se donose u okviru programa za zdravstvenu ispravnost hrane. U skladu sa tim, svi elementi analize rizika primenjuju se u svakoj fazi lanca ishrane, a pre svega u fazi pre klanja. Ovo poslednje znaci da se mora izvršiti implementacija programa za menadžment rizika na farmama (6). Potreba da se obezbedi zdravstvena ispravnost hrane životinjskog porekla u smislu potencijalnog rizika koji predstavlja transmisibilna spongioformna encefalopatija (TSE) životinja istakla je znacaj podataka koji se odnose na kvalitet i bezbednost hrane za životinje, mogucnost pracenja životinja koje se koriste za ljudsku ishranu i proizvoda od njih i dinamiku unutrašnje trgovine životinjama u svakoj zemlji i regionu. Ovaj pro -aktivni pristup služi kao model za nadzor zoonotskih agenasa koji se vezuju sa proizvodnjom životinja i on se odmah može primeniti u proceni rizika koji preti od brojnih agenasa iz hrane, kao što su Campylobacter spp., Toxoplasma spp. i Salmonella spp. Pristup kontroli zoonoza u zapatu ili jatu Procesi proizvodnje životinja za ljudsku ishranu doživele su korenite promene u poslednjih pedeset godina. Stepen promena varira od države do države, a u svetu od regiona do regiona, u pogledu razlika u samoj prirodi i kvalitetu 66
proizvoda koji su proizvedeni u razlicitim proizvodnim režimima u svakom pojedinaccnom regionu. Program! održavanja zdravlja zapata i upravljanja proizvodnjom su primeri ovog razvoja. Težište ovih programa je ekonomika farme, primena veterinarsko-zootehnickih mera, kao i proširenje saznanja o posledicama oboljenja kod životinja koje se koriste za ljudsku ishranu (7). Kljucni elementi u ovakvom programu obuhvataju procenu rizika i postavljanje prioriteta na samom pocetku, nakon cega sledi inspekcija farme i klinicki pregled životinja, monitoring podataka i analiza i prevencija problema u zapatu / jatu. Ovakav pristup se mora usvojiti u zavisnosti od vrste životinja i intenziteta farmske proizvodnje (2). Neke infekcije ne izazivaju morbiditet kod životinja (npr. Escherichia coli O157 i druge verocitotoksicne E. coli [VTEC]), ali mogu da izazovu teške bolesti kod ljudi, dok druga oboljenja kao što su bruceloza, salmoneloza i leptospiroza predstavljaju opasnost kako za zdravlje humane populacije, tako i za životinje. Uvodenjem programa kontrole i era dikacije, kao i dobre higijenske prakse u lancu ishrane, ustanovljena i još jedna kategorija zoonoza, naime one koje ukljucuju zoonotske agense koji se mogu smatrati "bolestima proizvodnje životinja" i koje imaju minimalni uticaj na javno zdravlje. Svest o postojanju zoonotskog hazarda mora biti prisutna i kod proizvodaca životinja i kod ljudi zaposlenih u industriji mesa, mlecnih proizvoda, i u živinarstvu. Primarni proizvodac je taj koji mora da preduzme sve mere da spreci ulaz patogenih agenasa na svoj posed. On je odgovoran za zdravlje svog zapata i mora da usvoji pozitivan stav prema zdravlju životinja na farmi, sa ciljem da se eliminiše ili svede na minimum izloženost zoonotskim agensima onih životinja koje su namenjene za proizvodnju hrane. Ovo je kljucna komponenta svih shema longitudinalnog integrisanog obezbedenja kvaliteta (LISA) koje se trenutno usvajaju u vecini razvijenih zemalja. Ovo cini integralni deo shema za obezbedenje kvaliteta hrane i obezbedenja bezbednosti i predstavlja prirodni pravac razvoja modeme farmske prakse i preventivne veterinarske medicine u pogledu proizvodnje hrane životinjskog porekla za ljudsku ishranu. Osnovni ciljevi su da hrana koja se proizvede na farmi bude i zdrava i konkurentna, da životinje kao sirovine za proizvodnju hrane ne bude ugrožena i da se sa životinjom postupa humano tokom njenog života. Kao prvo, održavanje integriteta zapata /jata kao posebnog entiteta, ako je moguce, predstavlja kljucni cilj kontrole zdravlja u proizvodnji životinja namenjenih za ishranu. Za pocetak, ako je potrebno prvo izvršiti nabavku stoke, neophodno je obezbediti da životinje poticu iz zapata ciji se zdravstveni status može što preciznije odrediti i pratiti i obezbediti mogucnost pracenja životinje i proizvoda od nje kroz ceo lanac ishrane. Mogucnost pracenja svih ulaza na farmu, kako robe tako i životinja, neophodna je u slucaju da vlasnik farme nije siguran u poreklo robe/životinja i ako nije siguran da su se u ranijim fazama ispoštovale mere dobre proizvodne prakse. 67
Zbornik radova i kratkih sadrzaja Nepravilna primena antimikrobnih sredstava može izazvati stvaranje multirezistentnih mikroorganizama koji mogu predstavljati problem za javno zdravlje i mogu negativno uticati na poverenje potrošaca(l). Tako su multirezistentni sojevi Salmonella newport i Salmonella typhimurium DT 104 predmet velike zabrinutosti kako kod ljudi tako i životinja. Antibiotic! su potrebni u procesu kontrole bolesti i prevencije, ali oni ne bi smeli biti zamena za dobru proizvodacku praksu i moraju se koristiti racionalno i uz stalni veterinarski nadzor. Poslednjih godina u severnoj Evropi povlacenje iz upotrebe antibiotika koji su se ranije koristili kao promoter! rasta nije imalo negativan uticaj na profit farmera. niti na zdravlje životinja kako kod proizvodnje svinja, tako i kod proizvodnje brojlera. Rezultat ovog pristupa je i smanjenje antimikrobne rezistencije kod životinja, ljudi i u proizvodima namenjenim za ljudsku ishranu (5, 8. 9). Vakcinacija može poboljšati imunološki status zapata i smanjiti rizik od oboljenja, a time i potrebu za antibioticima. Uslovi uzgoja, kao što je razdvajanje na starosne grupe, ishrana kolostrumom, izdvajanje bolesnih životinja i adekvatna dezinfekcija mogu spreciti širenje oboljenja i doprineti održanju zdravlja unutar zapata / jata. Odgovarajuce mere kontrole ekto- i endo-parazitoza sprecice pojavu kržljavaca kod životinja i njihovu prijemcivost za druge bolesti. Politika korišcenja lekova za životinje mora biti naucno zasnovana, detaljno dokumentovana i redovno kontrolisana (1). Uvodenje sistema upravljanja kvalitetom može biti jednostavnije u vecim preduzecima, gde se procedure mogu dokumentovati i gde se mogu usvojiti sistematicniji pristupi. Potvrda statusa (slobodno od bolesti) novih životinja koje su uvedene u zapat najbolje se postiže prethodnim testiranjem i izdvajanjem ovih životinja pre nego što se uvedu u zapat / jato. Ovaj koncept karantina najbolje je nastaviti i u okviru sistema proizvodnje, kada se radi o osobama koje nisu zaposlene na farmi, kojima se dopušta ograniceni pristup životinjama ili hranivu. Uvodenje sanitarnih pravila, ukljucujuci i primenu dezinficijenasa na kljucnim mestima, nošenje zaštitne odece i obuce, uz efikasnu kontrolu higijenske ispravnosti i kvaliteta hraniva i izvora vode, kontrolu glodara i štetocina, predstavljaju standardnu bio-sigurnostu praksu, koja je neophodna za održanje integriteta proizvodne jedinice. Praksa "sve unutra/sve napolje", uz blagovremeno izdvajanje svih klinicki obolelih životinja predstavlja direktan put ka unapredenju kontrole bolesti i prevencije na nivou zapata ili jata. Povecana kolicina osoke koja je neizbežna na farmama, a narocito njeno uklanjanje, predstavlja predmet od interesa za javno zdravlje pošto, za razliku od stajnjaka, ovakvi materijali ne mogu da se preraduju u kompost i velika je verovatnoca da sadrže veliki broj patogena koje izlucuju inficirane životinje. Sa stanovišta javnog zdravlja, posebnu pažnju treba posvetiti farmama sa velikim brojem životinja i farmama sa intenzivnim uslovima uzgoja. Ovo je slucaj narocito kod proizvodnje svinja i živine, gde je prevalentnost infekcije agensima kao što su salmonela i kampilobakter narocito izražena, bez obzira na cinjenicu da 68
Zbornik radova i kratkih sadrzaja je, u principu, stepen klinicki manifestne bolesti izazvane ovim agensima relativno nizak. 1995. godine grupa vodecih specijalista za javno zdravlje americke organizacije Animal Production Technical Analysis Group on Risk and Health Impact rangiala je patogene iz hrane na osnovu akutnih i hronicnih uticaja na zdravlje ljudi u SAD. Procenjeno je da su prvih šest na listi agenasa iz hrane bili: Salmonella spp. (non-typhoid), Campylobacter jejuni/coli, Toxoplasma gondii, E. coli O157:H7, Listeria monocytogenes, Yersinia enterocolitica i Trichinella spiralis. Od svih njih, Listeria je mikroorganizam koji predstavlja najveci izazov kad je u pitanju kontrola. Osim što je zoonotski agens, ona može biti ubikvitarna u vecini sredina. Ulazak životinje koja je inficirana ili kolonizovana nekom od ovih vrsta u pogon za proizvodnju mesa predstavlja rizik ne samo za bezbednost hrane nego i za radnike. Nedavno su Hensel i Neubauer (4) proširili ovu listu i ukljucili niz vimsnih agenasa, uzimajuci u obzir i dejstvo nedavnih promena u našoj zivotnoj sredini kao i industrijskih promena koje su povecale rizik za modernu farmsku praksu. Prevencija kontaminacije hrane zoonotskim agensima na nivou farme pre nego "detekcija/inspekcija" predstavlja osnovu za implementaciju programa za kontrolu zdravstvene ispravnosti hrane u preradi ili prometu i uvek ce ostati primarni cilj. Kod sistema zaštite proizvoda na "preharverst" nivou u integrisanom sistemu proizvodnje goveda, svinja i živine, ovi principi se vec primenjuju i od strane farmera i terenskog veterinara. Ovo treba sprovoditi tokom procene, npr. kvaliteta vode i hraniva, zdravlja životinja, dobrobiti životinja, nivoa sigurnosti pri izboru i upotrebi terapijskih sredstava kao i klinickog stanja životinja namenjenih za hranu i bezbednosti životne sredine, odnosno primena standarda u rukovanju otpadnim vodama poreklom od životinja i njihovim korišcenjem na farmi. Na taj nacin mogu se dobiti potrebni podaci o relativnoj bezbednosti životinje i mogucnosti njenog korišcenja za ljudsku ishranu. Ovakve informacije predstavljaju osnovni zahtev LISA-programa za zdravstvenu kontrolu hrane životinjskog porekla, koji sadrže sledece elementerodobrenje za proizvodni pogon, izvor vode i hranivo; identifikaciju i zdravstveni pregled životinja na farmi; veterinarsku potvrdu o zdravlju životinje prilikom ulaska na farmu; kontrolu transporta životinje; pregled ante-mortem na farmi; identifikacija i post-mortem pregled uginulih životinja; veterinarsku potvrdu o zdravstvenom stanju uginulih životinja; kontrolu rashladnih linija/linija za preradu/transport/distribuciju. Vecina mera biosigurnosti su opšte i nisu specificne za odredene zoonoze i one moraju biti deo dobre farmerske prakse. Tako npr. kontrola Campylobacter spp., i elementi kontrole kampilobaktera mogu se primeniti i na prevenciju drugih zoonotskih agenasa kod razlicitih životinjskih vrsta, narocito onih koje se drže u uslovima intenzivnog uzgoja. 69
Tuberkuloza: tuberkuloza kod goveda i njen znacaj kao uzroka bolesti kod ljudi predstavlja jedan od glavnih razloga za uvodenje metoda direktnog pregleda na liniji klanja i pasterizacije mleka i mlecnih proizvoda. Kao klinicki entitet kod goveda ovo oboljenje je danas skoro u potpunosti iskorenjeno u vecini razvijenih zemalja. Ipak, još uvek postoji incidencija izolata kod kojih je inficirano govece direkan izvor Mycobacterium bovis, a time i infekcije kod ljudi (4). U velikom broju zemalja u razvoju, gde se oboljenje kod goveda i srodnih vrsta ne kontroliše zbog nedostatka sredstava, ova bolest predstavlja istu, ako ne i vecu pretnju za ljudsko zdravlje kao i pre stotinu godina pošto su imunokompromitovani pojedinci narocito prijemcivi. Jedan od korisnih efekata nacionalnih programa za eradikaciju bovine tuberkuloze bio je i uklanjanje vecine inficiranih goveda pre nego što dostignu klinicku fazu bolesti, odnosno koristi se tuberkulinska proba.tuberkulin test je efikasan skrining-test i da može da predstavlja osnovu za uklanjanje reaktora na lokalnom ili regionalnom nivou u zemljama u kojima finansijska ogranicenja ne dopuštaju implementaciju nacionalnog programa eradikacije ovog oboljenja. U meduvremenu, potrebno je uložiti sve napore da se spreci ulazak infekcije u zapate goveda, ovaca, koza, jata živine iz okoline ili kontaktom sa divljim životinjama. Razdvajanje grla razlicite starosti, efikasna prerada dubriva, poštovanje sanitarnih mera ukljucujuci dezinfekciju i strogo kontrolisan program škartiranja obolelih životinja su od kljucnog znacaja za održavanja zapata ili jata slobodnim od tuberkuloze, narocito u regionima u kojima je prevalentnost tuberkuloze u populaciji životinja zabrinjavajuca. Paratuberkuloza: Mycobacterium avium paratuberculosis (MAP) je uzrocnik paratuberkuloze (Džonove bolesti), hronicnog neizlecivog oboljenja kod preživara, a postoji pretpostavka da MAP ima ulogu i u etiologiji Kronove bolesti, hronicne upale crevnog trakta kod ljudi. Ova hipoteza nije dokazana, ali opšti princip da obolele životinje ne bi trebalo koristiti za ljudsku ishranu bi trebalo poštovati. Ipak, kontrola Džonove bolesti u mlecnim zapatima je veoma komplikovana i zasnovana je na dva principa, naime, identifikaciji i eliminaciji inficiranih životinja i prevenciji novih infekcija. Kontrola ukljucuju sledece: odrediti prevalentnosti oboljenja u zapatu; škartirati klinicke i subklinicke slucajeve identifikovane pomocu seroloških testova; smanjiti kontakte izmedu novorodene teladi i njihovih majki ukoliko je status majke nepoznat; održavati farmu i njenu okolinu tako da se obezbedi da stoka ne pase na kontaminiranim pašnjacima; poštovati stroge kriterijume prilikom procene statusa novonabavljenih grla uz primenu seroloških testova i saznanja o statusu zapata iz kojih nova grla poticu; ukoliko je dozvoljeno, vakcinisati stoku kako bi se smanjilo izlucivanje mikroorganizma putem fekalija i kako bi se broj klinickih slucajeva sveo na minimum. VTEC je prisutna u crevima i fecesu zdravih goveda i ovaca, tako da ove životinje predstavljaju rezervoare infekcije za ljude. Domace životinje su rezervoari vecine VTEC, a goveda su glavni izvor E. coli O157:H7 i drugih VTEC. 70
Životinje koje su nosioci VTEC ne pokazuju klinicke znake bolesti, vizuelnim pregledom se ne razlikuju nosioci VTEC od ostalih životinja. Ove bakterije postale su deo normalne crevne flore zdrave stoke; u bilo kom trenutku odredeni procenat njih mogu biti HP-VTEC. Ovaj mikroorganizam može da preživi u zamljištu i nekoliko meseci (4). Slucajevi koji su se javljali u porodicama na farmi i medu posetiocima ovih farmi bili su uglavnom rezultat direktnog kontakta sa stokom ili fecesom ili konzumiranja nepasterizovanog mleka. Efekti koje praksa uzgoja ima na prevalentnost VTEC kod životinja još uvek su u velikoj meri nepoznati. Osim toga, do sada nije identifikovano stanje kliconoše koje bi bilo predmet odredenog interventnog programa. Zbog toga se eradikacija VTEC iz zapata u farmskim uslovima ne cini ostavrivom. Ipak, na farmama moguca je implementacija odredenih mera za smanjenje rizika od VTEC infekcija. Bruceloza: bruceloza je infektivno oboljenje ljudi i životinja, koje izazivaju bakterije roda Brucella spp. Infekcija izazvana ovim mikroorganizmom izaziva kontagiozni abortuse, kada dolazi do ekskrecije velikog broja mikroorganizama u okolinu. Infekcija se dobija od inficiranih ženki prilikom ili nakon abortusa, iz kontaminiranog mleka, prenosi sa seksualnim putem ili se dobija iz kontaminirane okoline. Inficirane životinje nose bakteriju u limfnim cvorovima, vimenu i uterusu, genitalijama i odgovarajucim limfnim cvorovima. Bakterija preživljava i šest meseci u kontaminiranom dubrivu i može se širiti sa farme na farmu. Oboljenje je, ili je bilo, predmet programa eradikacije u mnogim zemljama. Program! kontrole obuhvataju dva osnovna metoda, vakcinaciju i uklanjanje inficiranih i izloženih životinja na osnovu seroloških testova. Podršku ovim merama predstavlja i kontrola kre tanja životinja i karantin inficiranih farmi. Ukoliko se ne izvrši identifikacija inficiranih grla i one se blagovremeno ne iskljuce iz zapata, predstavljace izvor infekcije za druge životinje i ljude, direktno ili indirektno. Osim toga, vlasnici i njihove porodice, kao i osobe profesionalno izložene, mogu se infekcirati konzumiranjem sirovog mleka. Takode, mlecni proizvodi od nepasterizovanog mleka predstavljaju potencijalni izvor infekcije za potrošace. Pasterizacija cini mlecne proizvode bezbednim, ali ne rešava problem direktnog ili indirektnog puta transmisije na ljude. Zakljucak Rizici od zoonoza koji prate proizvodnju životinja namenjenih za ljudsku ishranu i industriju hrane mogu se javiti na farmama, u pogonima za proizvodnju hrane i u lancu distrib ucije. Svest o ulozi proizvodaca životinja namenjenih za ljudsku ishranu i cinilaca industrije hrane o postojanju ovakvog rizika u hrani predstavlja prvi korak ka njihovoj kontroli. Pozitivan stav prema zdravlju životinja na farmama u cilju eliminisanja i smanjenja izloženosti životinja ovakvim rizicima, uz ante- i post-mortem veterinarske preglede svih životinja u pogonima za preradu mesa efikasno uklanja obolele životinje iz lanca ishrane. Dobra higijenska praksa u 71
toku prerade i obrade mesa, a zatim i u toku pripreme hrane predstavlja još jednu sigurnosnu kariku u lancu do krajnjeg potrošaca. Fundamentalna i primenjena istraživanja su doprinela proizvodnji i isporuci zdrave hrane, prihvatljive za kupce. Ovakve mere se trenutno primenjuju u cilju prevencije i kontrole transmisije zoonotskih agenasa preko lanca ishrane. Efikasna kontrola pociva na implementaciji visokih higijenskih standarda u svim fazama proizvodnje, kako na farmama i u proizvodnim pogonima, tako i u svim elemeritima lanca ishrane. U torn smislu, uloga edukacije je nezaobilazan momenat i obaveza svih ucesnika u lancu ishrane i industriji hrane. Narocitu pažnju treba posvetiti obuci i edukaciji proizvodaca, saradnji sa veterinarima na terenu i ostalim savetodavnim telima kako bi se smanjio stepen izloženosti domacih životinja mikroorganizmima koji predstavljaju opasnost po javno zdravlje. U torn smislu, potreba da se otkloni opasnost koji predstavlja rastuca antimikrobna rezistencija, s obzirom da se lanac ishrane smatra veoma važnom putanjom pasivnog transfera rezistentnih patogena sa životinja na Ijude. Literatura 1. Abury-Damon H., Grent K., Sall-Ndiaye P., Che D., Cordeiro E., Bougnoux M.-E., Riguad E., Le Strat Y., Lemanissier V., Armand-Lefevre L., Delzescaux D., Desenclos J.-C, Lienard M.&Andermont A. (2004). - Antimicrobial resistance in commensal flora of pig farmers. Emerg. infect. Dis., 10 (5), 873-879. 2. Brand A., Noordhuizen J.P.T.M.&Schukken Y.H. (1996).-Herd health and production management in dairy practice. Wageningen Academic Publishers, Wageningen, 543 pp. 3. Commission of the European Communities (CEC) (2000). - White paper on food safety. COM (1999) 719 final. CEC, Brussels, 52 pp. 4. Hensel A. & Neubauer H. (2002). - Human pathogens associated with onfarm practices - implications for control and surveillance strategies. In Food safety assurance and veterinary public health, Vol. 1. Food safe ty assurance in the pre-harvest phase (F.J.M. Smudlers & J.D. Collins, eds). Wageningen Academic Publishers, Wageningen, 125-139. 5. Hinton M. H. & Rawlings C. (1996). - Factors affecting the microbial quality of meat, 1: disease status, production methods and transportation if the live animal. Proc. Meeting of CEC Concerted Action CT94-1456, 23-26 October 1995, Kaap Dorn. University of Bristol, 147 pp. 6. Noordhuizen J.P.T.M.&Welpelo H.J. (1996). - Sustainable improvement of animal health care by systematic quality risk management according to the HACCP concept. Vet. q.,18 (4), 121-126. 7. Noordhuizen J.P.T.M.&Collins J.D. (2002). - Pre-harvest health and quality monitoring, risk assessment and their relevance to the food chain. In Food 72
safety assurance and veterinary public health, Vol. 1. Food safety assurance in the pre-harvest phase (F.J.M. Smulders & J.D. Collins, eds). Wageningen Academic Publishers, Wageningen, 115-124. 8. Sorensen T. L. Wagener H. C. & Frimodt-Moller N. (2002). - Resistant bacteria in retail meats and antimicrobial use in animals. N. Engl. J. Med., 346 (10), 777-779. 9. Weirup M. (1998). - Preventive measures replace antibiotic growth promoters: ten years experience from Sweden APUA Newsletter, 16 (2), 1-4. 10. World Trade Organization (WTO) (1995). - Agreement on the application of sanitary and phytosanitary measures. World Trade Organization, Geneva.
Summary CONTROLING ZOONOSES AT FARM LEVEL Branka Vidic, R.Kla.jic Controlling zoonotic agents in animal and poultry reservoirs has the effect of reducing the challenge to food safety management systems in processing and further along the food chain. Producing and maintaining healthy stock requires good husbandry practices, which include stock selection and veterinary attention. Feed is a key input, both as a source of pathogen-free nutrients and as a balanced diet to maintain healthy livestock. Safe water, appropriate vermin and wildlife control and an optimum environment to reduce stress are important if animals are to perform. Farms are not sterile environments and initiatives to reduce the zoonotic hazards have to be practical, economically feasible and flexible, depending on the scale of the enterprise, the species being farmed, and the epidemiology of the zoonotic agents in the particular geographical region. Education of farmers and stockmen is crucial to successful on-farm control of zoonoses, as an understanding of why control measures are necessary, and how they can be applied, will improve compliance with protocols and procedures. This understanding is a first step towards the implementation of a longitudinal integrated food safety assurance approach to zoonosis control in the pre-harvest phase of the food chain. Key words: biosecurity, epizootiology, herd health, zonosis control. Introduction Ensuring that food is safe from the hazard of zoonotic agents requires controls along the entire continuum from farm to fork. To reduce the challenge to food safety management systems further along the food chain, it is important that everything that is reasonable, practical and economically feasible is achieved on the farm, in the pre-harvest phases. The health of food animals is inextricably linked to the production of safe food and the health of humans. Increasing stocking density, associated with the drive for the economies of scale required to maintain commercial viabilit y in an increasingly competitive global food market, presents the opportunity for build up, and transmission, of infectious agents. Furthermore, global distribution of animal feed permits the dissemination of pathogens to geographical areas, individual farms and susceptible livestock that were previously unexposed. In addition, livestock moving between lanns and between countries 4*
facilitates transmission of disease. This is often compounded by the stress associated with the transport and the mixing of strange groups of animals. Consumers seek safe food of good quality produced in enenvironmentallyfriendly way with the highest animal welfare standards possible. Farms are not sterile environmentsrhowever, an expectation that livestock will receive safe feed, safe water, effective effluent management is not unreasonable.there are primary biosecuriry measures, based on a risk assessment, that are applicable in different farming enterprises that will reduce the incidence of most zoonotic agents(2,3). Howevr, different enterprises and different countries require additional controls depending on the epidemiology on the zoonotic agents presents in their livestock and in the local human populations and the intensity of their farming operations. All recent international trade agreements have stressed the importance of risk analysis and the application throughout the food chain, of prevention systems based on hazard analysis and critical comtrol point( 6,10). Development in biotehnology notably those relating to rapid methods for the detection of unwanted contaminants, biological or otherwise, provide a new and practical approach to food safety assurance based on statistical sampling programmes, internal quality control systems and real-time feedback to farm ( 7). The Europen Commission White Paper on Food Safety (3) acknowlenged the need to ensure that there is a scientific basis for decision making within the food safety programme. Accordingly all the elements of risk analysis are seen to apply to each phase of the food chain, and to the pre-harvest phase in the first instance. The latter means that on-farm quality risk management programmes have to be developed and implemented (6). The need to ensure the safety of food of animal origin in respect of the potential risk posed by the TSE of animals has increased the importance of sound data on the quality itety each The > be imal ased, the and safety of animal feedstuffs, the traceability of food animal and their le in products and the dynamics of internal trade in animal in each country and region. This pro-active approach serves as a model for the surveillance of zoonotic agents as sociated with livestock production and has an immediate application in the assessment of the risk posed by a wide range of food-borne agents such as the Campylobacter spp. Toxoplasma spp. and Salmonella spp. A herd and flock health approach to zoonosis control Food animal production methods have undergone substantial changes over the past fifty years. The rate of change has varied from country to country and, worldwide, from region to region, with consequential differences in the nature and quality of the products produced under the different regimes in operation in each region. Herd health and production management programmes are examples of this development. The main focus of these programmes is on-farm economics and especially operational management through the application of velerinaryzootechnical skills and a wider knowledge of the commercial and societal 75
Zbornik radova i kratkih sadrzaja consequences of disease in the food-producing animal (7). Key elements in such a programme include risk assessment and priority setting at the start, followed by farm inspections and clinical examination of animals, data monitoring and herd/flock problem analysis and prevention. The approach has to be adapted depending on the species of animal involved and the intensity of the farming enterprise (2). Some infections cause no morbidity in animals (e.g. Escherichia coli O157 and other veroeytotoxigentc E. coli [VTEC]) yet can cause serious illness in humans, whereas other diseases such as brucellosis, salmonellosis and leptospirosis are important from both a public health and animal health standpoint. With the operation of control and eradication programmes and good hygiene practices in the food chain a further category of zoonoses has emerged, namely, those involving zoonotic agents that can now be regarded as animal production diseases that have a minimal impact on public health. Awareness on the part of food animal producers and the meat, poultry and dairy industries that zoonotic hazards exist is the first step towards their control. It is the primary producer who must take all reasonable measures to prevent the entry of pathogenic agents onto his or her holding. They are responsible for the health of their slock and must adopt a positive approach to animal health on the farm with the objective of eliminating or minimising exposure of food-producing animals to zoonotic agents. This is an essential component of the longitudinal integrated safety assurance (LISA) schemes now being adopted in many developed countries. This forms an integral part of food quality and safety assurance schemes and is a natural development of modern farming practice and veterinary preventive medicine in relation to the production of foods of animal origin for human consumption. As a starting point, maintenance of the integrity of the herd or flock as a distinct and self-contained entity, if possible, remains a key objective of health control in food animal production. To begin with, where stock has to be purchased, it is essential to ascertain the origin of such stock so as to define as far as possible the health status of the herd of origin and to ensure the traceability of the animal and its produce as it moves through the food chain. Traceability of all inputs to the fanning enterprise, both goods and stock, is important because if a farm manager is unaware of the origin of inputs, he/she cannot be assured that best practices were adhered to in its production. Selective pressure associated with the inappropriate use of antimicrobials can generate multidrug-resislant organisms which can become a public health problem (1). For example, multiresistant strains of Salmonella newporl and Salmonella typhimurium DT 104 are a cause of major concern for both humans and animals. Antibiotics are necessary to control disease and prevent animal suffering, but they should not be a substitute for good husbandry practices and should be used prudently under veterinary supervision. In recent years in Northern 76
Europe the withdrawal from use of antimicrobials used in the past for growth promotion has had no negative consequences for farmers' profits or animal health in the case of both pig and broiler production. The effect of such withdrawal in countries has been a decrease in antimicrobial resistance in animals, food products and humans (5, 8, 9). Vaccination can raise herd immunity and reduce the risk of disease and the consequent need for antibiotics. Husbandry practices such as segregating age cohorts, feeding colostrum, isolating sick animals and adequate disinfeciion can prevent the spread of disease and contribute to maintaining the health of the herd or flock. Appropriate ecto- and endo-parasile control prevent animals becoming debilitated and more susceptible to other diseases. Policies for the use of animal remedies should be science-based and all use should be documented and continuously reviewed (1). Operating a quality management system can be easier in larger enterprises where procedures can be documented and a more regimented approach adopted. Confirmation of the disease-free status of recently purchased animals is best achieved through pre -purchase testing and segregation before such animals are allowed to join the flock/herd. This concept of quarantine is best continued throughout the production system, with persons other than farm personnel directly engaged on the farm being allowed only limited access to animals or feedstuff's. The enforcement of sanitation rules including the use of disinfectants at key points and the wearing of protective clothing and lootwear, together with effective controls on the hygienic quality of feedstuffs and water sources, including rodent and pest control, are standard biosecurity practices which are necessary if the integrity of the production unit is to be maintained. The practice of an "all in/all out" policy of stock movement together with the early segregation of all clinically ill animals offer a direct means of enforcing disease control and prevention at the herd or tfock level. The increased volume of animal slurries produced on farms and in particular, their disposal, is a cause of public health concern since, unlike manure, such materials are not composted and are likely to contain high numbers of pathogens voided by infected animals.the need for care in dealing with animals kept under intensive conditions or in large numbers on the farm is therefore all the greater, from the public health viewpoint. This is especially the case in both pig and poultry production, where the prevalence of infection with such agents as salmonellas and campylobacters may be considerable, irrespective of the fact that, generally, the extent of clinical disease associated with these infections is low. In 1995 a group of leading public health specialists in the Animal Production Technical Analysis Group on Risk and Health Impact in the United States of America (USA) ranked food-borne pathogens according to acute and chronic human health effects in the USA. The top six priority food-borne agents were adjudged to be: Salmonella spp. (non-typhoid), Campylobacter jejuni/coli, Toxoplasma gondii, E. coli O157:H7, Listeria monocytogenes and jointly, 77
Yersinia enterocolitica and Trichinella spiralis. Of these, Listeria is a particularly challenging organism to control as, in addition to being a zoonotic agent, it can be ubiquitous in many environments. The entry of animals infected or colonised with some ol these species into meat plants poses risks for operatives, in addition to the food safety risks. More recently, Hensel and Neubauer (4) extended this list to include a number of viral agents and also considered the effects of recent environmental and industrial changes that have increased risks associated with modern on-farm practices. The prevention of contamination of the food product with zoonotic hazards at farm level rather than the "detection/inspection" which is intrinsic to the implementation of food safety control programmes at factory or "post-harvest" level, is and remains, a primary objective. In achieving product protection at the "pre-harvest" level in integrated systems of beef, pig and poultry production, these principles will already have been applied by both the farm manager and the field veterinarian. This will have been carried out in the course of assessing, for example, water and feed quality, animal health and performance records, animal welfare, the level of safety applied in the choice and use of therapeutic agents, and the clinical condition of the food animals, as well as the safety of the environment as affected by the standard of animal effluent management and utilisation on the farm. On this basis a reasoned conclusion can be reached concerning the (relative) safety of the food animal and its suitability for slaughter for human consumption. Such information is a basic requirement of LISA-based programmes and for the extended health control of foods of animal origin, which includes the following elements: approval of production holding, water supply and feedstuffs; on-farm identification and health examination of animals; veterinary certification of animal health at the farm gate; animal transport controls; in-plant ante-mortem examination; carcass identification and post-mortem examination; veterinary health certification of carcass and offals; coldline/processing/transport/clistribution controls. Many brosecurity measures are general and nol specific to particular zoonoses and should be part of good farming practice. The control of Campylobacler spp., but elements of campylobacter control can be applied in principle to the prevention of exposure to other zoonotic agents in a variety of animals, particularly those reared under intensive conditions. Tuberculosis in cattle and its importance as a cause of disease in some human populations represents one of the principal reasons for the introduction of direct inspection methods for meat control and the pasteurisation of dairy products. As a clinical entity in cattle this disease has now been almost completely eradicated in most developed countries. Isolated incidences in which there is direct involvement of infected cattle as the source of Mycobacterium bovis infection in humans still occur (4). In a number of developing countries, where the disease in 78
cattle and related species is not controlled due to lack of national funds, the disease poses the same if not a greater threat to human health as it did a century ago in most developed countries of today, since immuno-compromised individuals are particularly susceptible. One of the beneficial effects of national bovine tuberculosis eradication programmes has been the effective removal of most infected cattle before they reach the clinical stages of the disease and before the major organs show overt signs of involvement. Animals which show a high responsiveness to bovine tuberculin are the animals most likely to display gross lesions at slaughter. This demonstrates that the tuberculin test is an effective screening test and it may, therefore, provide a basis for the strategic removal of reactors at local or regional level in countries in which financial constraints prevent the implementation of a national eradication programme for this disease. Meanwhile, every effort should be made to prevent the entry of such infection into herds of cattle and, in some regions, sheep flocks and herds of goats and deer as well, through the unwitting purchase of infected stock or contact with neighbouring infected herds or flocks and tuberculous wildlife. Segregation of stock of differing ages, effective composting of manure, attention to sanitary issues, including disinfection and a prudent culling programme, are of significant importance in maintaining a tuberculosis-free herd or flock, particularly in regions in which the prevalence of tuberculosis in the animal population is a concern. Paratuberculosis (Johne's disease). Mycobacterium avium paratuberculosis (MAP) is the causative agent of paratuberculosis (Johne's disease), a production disease in ruminants, and a hypothesis exists that MAP may be involved in the aetiology ot Crohn's disease, a chronic inflammatory bowel disease in humans. The hypothesis is not proven, but the general principle that diseased animals should not be used as a source of food for humans should be adhered to. However, control ot Johne's disease in dairy herds is difficult and is based on two principles, namely, the identification and elimination of infected animals and the prevention of new infections. Essential to this process is a clear understanding on the part of the herd owner of the fundamental processes involved. These include the following: determining the prevalence ot the disease in the herd; culling clinical and subclmical cases identified by the diagnostic tests available; reducing the contact between newborn calves and their dams where the status of the dam is unknown; managing the farm and its environment so as to ensure that stock do not graze on contaminated pasture; strictly assessing the status of bought-in stock based on serological testing and the history of the herd of origin; vaccinating, where permitted, to reduce faecal shedding of ihe organism and the number of clinical cases. Verocytotoxigenic Escherichia coli.the VTEC is present in the gut and faeces of healthy cattle and sheep and these animals therefore act as reservoirs 79
from which humans can become infected. Livestock are a reservoir for most VTEC, with cattle being the principal source of E. coli O157:H7 and other VTEC. Studies from the United Kingdom (UK) and the USA have shown that VTEC is, at least occasionally, present on most farms. The organism can survive in soil for several months (4). Cases in farm families and farm visitors have resulted from direct contact with livestock or faeces or from drinking unpasteurised milk. The effects of animal husbandry practices on the prevalence of VTEC in animals are to a considerable extent unknown. Moreover, no defined carrier state has been identified which can be targeted for an intervention programme. Therefore, eradication of VTEC from the farm livestock or farm environment does not seem to be a reasonable goal. However, risk reduction measures can be implemented onfarm to minimise the risk of VTEC infections. Brucellosis is an infectious disease of man and animals, mainly cattle, caused by the bacterium, Brucella spp. Infection with this organism causes contagious abortion in cows and deer when large numbers of organisms are shed into the environment. Infection is acquired from infected females at, or following, abortion, from contaminated milk, sexually transmitted or acquired from a contaminated environment. Infected animals harbour the bacterium in their lymph nodes, udder and uterus, and in the case of bulls, the male genitalia and related lymph nodes. The bacterium survives for upwards of six months in contaminated slurry and can be spread from farm to farm, and can infect people, during spreading. The disease is or has been the subject of an eradication programme in many countries. Control programmes employ two principal methods, namely, vaccination and the removal for slaughter of infected and exposed animals based on serological testing. These measures are supported by movement controls and quarantine on infected farms. Unless infected cows are identified early, and are removed immediately, they are a source of infection for other animals and people, either through direct or indirect exposure. Furthermore, farmers and their families, along with their workers, can be exposed to infection by drinking raw milk. Likewise, dairy products made from unpasteurised milk are a possible source of this infection for consumers. Pasteurisation makes dairy products safe, but does not deal with the issue of the direct or indirect contact routes of transmission to humans. Conclusion Zoonotic hazards that are associated with food animal production and food processing may arise on the farm, in the food plant and in the distribution chain. Awareness on the part of food animal producers and the members of the food industry that such hazards may exist in foods is the first step towards their control. A positive approach to animal health on the farm with the objective of eliminating
or minimising exposure of food-producing animals to these hazards, supported by ante-and post-mortem veterinary examination of all food animals at meat plants, effectively removes overtly diseased animals from the food chain. Good hygiene practices throughout processing and, finally, cooking, provide further safeguards for the consumer. Such measures as are currently employed to prevent or control the transmission of zoonotic agents via the food chain in the post-harvest phases are unlikely to be successful in isolation. Effective control relies upon the implementation of a consistently high level of production hygiene at all stages of production both on the farm and in the processing plant, and throughout the remainder of the food chain. In this respect the role of education remains paramount for all stakeholders at every level of the food industry. In particular, attention is drawn to the need for training and education of the food animal producer, as it is possible by this means, and with the collaboration of veterinary practices and other advisory agencies, to reduce the level of exposure of livestock to microorganisms which are of public health concern. In this regard the need to address the dangers posed by the emergence of antimicrobial resistance as an important route for the passive transfer of resistant pathogens from animals to humans.