野豬--家豬的傳播
Wild boar-to-pig transmission
實驗研究表明，野豬和家豬一樣容易受到亞美尼亞(2008)和車臣(2009)的強毒性ASFV毒株的感染(Gabriel等人，2011年，Blome等人，2012年，Pietschmann等人，2015年)。口路(劑量為106 TCID50)、鼻路(劑量為3-25 HAD50/ml)和肌注(劑量為103 HAD50/ml)感染都導致了100%的死亡率。野豬出現了與家豬類似的非特異性臨床症狀，包括發燒、食慾減退、腹瀉和精神不振，並在7至9天內死亡，不分日齡和性別。
Experimental studies demonstrated that wild boars were as susceptible as domestic pigs to ASFV infection using highly virulent ASFV strains from Armenia (2008) and Chechnya (2009) (Gabriel and others 2011, Blome and others 2012, Pietschmann and others 2015). Oral (dose of 106 TCID50), nasal (dose of 3 to 25 HAD50/ml) and intramuscular (dose of 103 HAD50/ml) infections resulted in 100 per cent mortality. Wild boars developed non-specific clinical signs, similar to those observed in domestic pigs, including fever, loss of appetite, diarrhoea and lethargy and died within seven to nine days, regardless of age or sex.
最近的兩項實驗研究表明，直接接觸具有傳染性的野豬是一種有效到家豬的ASFV傳播途徑。與用亞美尼亞或車臣毒株感染的野豬直接接觸的易感豬在接觸後6至12天具有傳染性(Gabriel等人，2011年，Pietschmann等人，2015年)。當將易感豬放在相鄰的欄裡，防止直接接觸時，傳播發生在接觸後21天(Pietschmann等，2015年)。作者用亞美尼亞ASFV毒株(Pietschmann等人，2015年)估計出野豬群體與家豬群體之間在直接接觸和間接接觸時的R0分別為5.0 (95% CI 1.4 - 10.7)和0.5 (95% CI 0.1 - 1.3)(表2)。在俄羅斯ASFV爆發期間，野豬群之間的傳播動力學最近被量化為R0為1.58 (95% CI 1.1 - 3.8)(表2)(Iglesias等人2015)。
Two recent experimental studies indicated that direct contact with infectious wild boars is an effective ASFV transmission route to domestic pigs. Susceptible pigs housed in direct contact with infected wild boars with the ASFV strains from Armenia or Chechnya became infectious after six to 12 dpe (Gabriel and others 2011, Pietschmann and others 2015). When susceptible pigs were sepa- rated from the infectious wild boars in an adjacent pen to prevent direct contact, the transmission occurred after 21 dpe (Pietschmann and others 2015). The author estimated the R0 between groups of wild boars and domestic pigs using the Armenia ASFV strain (Pietschmann and others 2015) at 5.0 (95 per cent CI 1.4 to 10.7) and 0.5 (95 per cent CI 0.1 to 1.3) in direct and indirect contact scenarios, respectively (Table 2). During ASF outbreaks in Russia, the dynamics of ASFV transmission between groups of wild boars was recently quantified by the R0 at 1.58 (95 per cent CI 1.1 to 3.8) (Table 2) (Iglesias and others 2015).
針對受感染的野豬向家豬傳播ASFV有幾項田間觀察。在俄羅斯，有些ASF疫情最初是在野豬中發現的，後來才在家豬中發現，並且，在受ASF感染的農場附近發現了ASF致死的野豬(Gogin等人，2013年)。最近的一項研究表明，在俄羅斯西北部地區，家豬和野豬的ASF病例在空間上是相關的(Vergne等人，2015年)。例如，在靠近喬治亞的俄羅斯，靠近白俄羅斯的波蘭和立陶宛，以及靠近俄羅斯的烏克蘭，都發現了大量感染ASFV的野豬屍體(Gallardo等人，2014年)。對此的一種解釋是，近來為了減少野豬的數量而在該地區進行的密集狩獵導致了野豬日常的獵食範圍發生了重大變化(因為野豬試圖從聚集地逃跑) (Sodeikat和Pohlmeyer 2007, Thurfjell等人，2013年)，這就可能促進了ASFV的遠距離傳播。
There are several field observations about the possible contribution of infected wild boars to the spread of ASFV to domestic pigs. In Russia, some ASF cases were primarily detected in wild boars before being observed in domestic pigs, and the death of wild boars caused by ASF was observed in the vicinity of ASF-affected farms (Gogin and others 2013). A recent study has demonstrated that ASF cases in domestic pigs and wild boars were spatially correlated in the north west areas of Russia (Vergne and others 2015). High numbers of infected wild boar carcases were found close to national borders, for example, in Russia close to Georgia, in Poland and Lithuania close to Belarus and in Ukraine close to Russia (Gallardo and others 2014). One explanation proffered for this is that the recent attempts to reduce the number of wild boars in the region using intensive hunting practices have induced significant changes in the daily scavenging distance around the home of wild boar populations as they are trying to escape (Sodeikat and Pohlmeyer 2007, Thurfjell and others 2013), and these potentially facilitated ASFV spread over longer distances.
因此，ASFV很可能通過接觸傳染性野豬、被養殖戶或獵人不當處理的具有傳染性的自由放養豬、受感染家豬或野豬的屍體而在野豬之間傳播。然而，目前還不清楚ASFV是否能在這些野豬群中持續存在。例如，最近的分析表明，在俄羅斯西南部地區的野豬中，ASF病例之間不存在時空相關性，這表明ASFV在野豬群中的持續存在的時間有限(Lange等人2014年)，而這與俄羅斯西北部的結果是相反的。
ASFV is therefore likely to transmit between wild boars by contact with infectious wild boars, infectious free-ranging pigs or carcases of infected pigs or wild boars improperly disposed of by farmers or hunters. However, it remains unclear whether ASFV can be sustained in these wild boar populations. For example, in contrast to results from north-west Russia, recent analyses showed that there was no spacetime interactions among ASF cases in wild boars in south-west areas of Russia, suggesting the limited persistence of ASFV in wild boar populations (Lange and others 2014).