Klaus Depner
Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, 17493 Greifswald-Riems, Germany; e-mail: Klaus.Depner@fli.de
Izvor: Knjiga sažetaka simpozija “Afrička svinjska kuga – stanje i izazovi”
Nova i vrlo teška epizootija pojavila se u Gruziji 2007. godine, proširila se na Kavkaz i Rusku Federaciju te nedavno dospjela do Europske unije i Kine. U mnogim zemljama bolest je postala endemska u domaćih i divljih svinja. U populacijama divljih svinja ASK pokazuje perzistenciju vezanu na stanište, gubeći tendenciju dinamičnog širenja u prostoru. Kada je ASK prodrla u Europsku uniju predviđala su se dva glavna epidemiološka scenarija:
- (i) zbog visoke smrtnosti bolest bi mogla spontano nestati iz lokalne populacije divljih svinja, ili
- (ii) slično kao kod bjesnoće, epidemijski val vrlo brzo bi se kretao prema zapadu zahvaćajući velika područja Europe.
Obje hipoteze su se međutim pokazale pogrešnima. Virus nije spontano iščeznuo, niti je poprimio obilježje epidemijskog vala. Suprotno tome, zaraza se zadržava lokalno u divljih svinja s postojanom, niskom prevalencijom ispod 5%.
Gledajući retrospektivno mogu se uočiti dva glavna načina širenja bolesti:
- (i) polagani prijenos izravnim dodirom preko nosne sluznice javlja se lokalno u populacijama divljih svinja i
- (ii) skokovi u pojavi često u razmacima većim od stotinu kilometara.
Za lokalno širenje izravnim dodirom preko nosne sluznice u populacijama divljih svinja izračunata brzina prijenosa iznosi 2-5 km mjesečno.
Veliki tenacitet virusu osigurava dugo preživljavanje u okolišu, velika smrtnost u svinja omogućuje njegovu veliku izloženost u populaciji, a relativno niska kontagioznost sprječava nagli i potpuni nestanak populacije domaćina. Interakcija između ta tri parametra povećava lokalnu perzistenciju i geografsko širenje virusa što predstavlja izazov za njegovo iskorjenjivanje.
Ključne riječi: afrička svinjska kuga, epidemiologija, prijenos, perzistencija
African swine fever: a global view and the current challenge
Klaus Depner
Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, 17493 Greifswald-Riems, Germany
E-mail: Klaus.Depner@fli.de
A frican swine fever (ASF) is considered internationally as one of the most dangerous animal diseases of swine, affecting trade and having serious socio-economic impact on people‘s livelihood. No drugs or vaccines are available to fight ASF. The most recent and severe epidemic which started in Georgia in 2007, spread throughout the Caucasus and the Russian Federation, reaching the European Union and China. In many countries the disease has become endemic in domestic pigs and wild boar. In wild boar populations ASF shows a pattern of habitat bound persistence lacking a tendency of dynamic spatial spread.
When ASF entered the EU two main epidemiological scenarios were forecasted: i) due to the high lethality the disease would spontaneously fade out from the local wild boar population or, ii) alternatively an epidemic wave, rabies-like, would start moving westward very rapidly, affecting large areas of Europe. However, both epidemiological hypotheses proved to be wrong. The virus did not fade out nor assumed an epidemic wave behavior. On the contrary the infection survived locally in wild boar with a steady, low prevalence below 5%.
Retrospectively, two main patterns of disease spread became evident: (i) slow, nose-to-nose spread occurring locally in wild boar populations and (ii) outbreak jumps, often more than hundreds of kilometers. For the local nose-to-nose spread in wild boar populations a transmission speed of 2-5 km/month has been calculated.
The high tenacity of the virus ensures its long term persistence in the environment, high case fatality rate makes the virus largely available, and the relatively low contagiousity prevents the rapid and complete depletion of the host population. The interaction of these three parameters maximizes both local persistence and geographical spread of the virus making its eradication a challenge.
Humans are recognized as the main cause of both long-distance transmission and virus introduction into domestic pig farms. Thus, it has become crucial to include social science when planning prevention-, control-, and eradication-measures. By considering only the biological particularities of the disease, contagiousity, tenacity and case fatality rate, but ignoring the human aspects, the epidemic will not be controlled.
Keywords: African swine fever, epidemiology, transmission, persistence
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