PCR results are diagnostic test results, not a diagnosis. The diagnostician is an investigator and should employ all of the tools at his command. An expert with experience in China reviews how ASF should be diagnosed.

PCR結(jié)果只是診斷試驗(yàn)結(jié)果，而不是診斷。診斷師是一名調(diào)查員，應(yīng)該根據(jù)他的命令使用所有的工具。一位在中國有經(jīng)驗(yàn)的專家回顧了如何診斷ASF。

African swine fever is a severe viral disease of pigs of all ages. In recent years it has devastated the swine industry in many different countries. ASF actually spreads rather slowly and it is possible to curtail its geographic spread by appropriate action. Early definitive diagnosis is a key element to avoid spread. An initial field diagnosis of African swine fever can be made from clinical signs and necropsy findings.

非洲豬瘟是各種年齡豬的一種嚴(yán)重的病毒性疾病。近年來，它在許多不同的國家摧毀了養(yǎng)豬業(yè)。ASF的傳播速度實(shí)際上相當(dāng)緩慢，可以通過適當(dāng)?shù)男袆?dòng)來限制其水平傳播。早期明確診斷是避免傳播的關(guān)鍵因素。非洲豬瘟的初步現(xiàn)場診斷可根據(jù)臨床癥狀和尸檢結(jié)果作出。

Clinical signs:

In the initial phase of the disease, animals are often found peracutely dead with cyanosis of the legs, ears, and the extremities. Often there is high fever 40 - 42° C, vomiting, diarrhea that may be bloody or black (Photo 1, right), depression, abortions (Photo 1, left), bloody nasal discharge (epistaxis), and increasing death losses.

臨床癥狀：

在疾病的最初階段，動(dòng)物經(jīng)常被發(fā)現(xiàn)死于腿部、耳朵和四肢的發(fā)紺。經(jīng)常有高燒40-42°C，嘔吐，腹瀉，可能是血或黑(圖1，右)，抑郁，流產(chǎn)(圖1，左)，血鼻分泌物(鼻出血)，并增加死亡損失。

Photo 1. Abortion storm (left) and bloody diarrhea in sows (right).

P 流產(chǎn)風(fēng)暴(左)和母豬流血腹瀉(右)。

The low virulence (vaccine) strains cause a mild chronic atypical form of the disease with few deaths. Females generally exhibit chronic respiratory disease and chronic infertility. The longer time course to obvious illness or lack of observed clinical signs among the chronic vaccine virus pigs is often interpreted by the farm as a long incubation period.

低毒力(疫苗)株導(dǎo)致一種輕微的慢性非典型疾病，幾乎沒有死亡。母豬一般表現(xiàn)為慢性呼吸道疾病和慢性不孕癥。慢性疫苗病毒豬出現(xiàn)明顯疾病或缺乏觀察到的臨床癥狀的時(shí)間較長，通常被農(nóng)場解釋為一個(gè)較長的潛伏期。

Lesions at necropsy

• Epiglottis and trachea may be reddened, and there is generally an interstitial pneumonia with inter-lobular edema. Sometimes there is a fibrinonecrotic pleuropneumonia that resembles APP.

• A fibrinous myocarditis and pericarditis may be present, and the thorax and abdomen may have an excessive amount of bloody or serosanguinous fluid.

• The mesenteric lymph nodes and particularly the gastro-hepatic nodes may be enlarged, edematous, and appear to be necro-hemorrhagic on the cut surface (Photo 2).

• The spleen may be enlarged with multiple infarcts present or it may be essentially normal.

• The liver often contains frank hemorrhages.

• The kidneys may have numerous infarcts, and petechial and ecchymotic hemorrhages (Photo 3). There may be a striking peri-renal edema. The fundic stomach is often severely reddened and eroded, and the spiral colon may be filled with a bloody content. It is not unusual to find paintbrush hemorrhages on the abdominal viscera.

• A fibrinous meningitis may be evident in the brain.

• 尸檢病灶

• 會(huì)厭炎和氣管可能發(fā)紅，一般有間質(zhì)性肺炎伴小葉間水腫。有時(shí)會(huì)出現(xiàn)類似APP的纖維蛋白變性胸膜肺炎。

• 可出現(xiàn)纖維性心肌炎和心包炎，胸部和腹部可能有過多的血或漿液。

• 腸系膜淋巴結(jié)，尤其是胃-肝淋巴結(jié)可能增大，水腫，并出現(xiàn)壞死出血性在切割表面(照片2)。

• 脾臟可能擴(kuò)大，多個(gè)梗死灶出現(xiàn)，或它可能基本上是正常的。

• 肝臟經(jīng)常有大量出血。

• 腎臟可能有許多梗塞，點(diǎn)狀出血和異位出血(圖3)?？赡苡忻黠@的腎周水腫。胃底部經(jīng)常嚴(yán)重發(fā)紅和糜爛，螺旋結(jié)腸可能充滿血淋淋的內(nèi)容物。在腹部內(nèi)臟上發(fā)現(xiàn)油漆刷出血并不少見。

• 纖維蛋白性腦膜炎在大腦中可能很明顯。

Photo 2. Hemorrhage and necrosis in gastrohepatic lymph node.

圖2.胃肝淋巴結(jié)出血壞死。

Photo 3. Edema and petechial hemorrhages in kidney.

圖3.腎臟水腫和點(diǎn)狀出血。

The severity of the lesions among pigs is variable and it is generally suggested that multiple pigs be opened.

Necropsy should be done with a professional concern for biosafety, but necropsy does not introduce unique disease hazards to an infected farm and does provide valuable information not attainable by less aggressive diagnostic approaches.

豬的皮膚損傷的嚴(yán)重程度是不同的，而且 一般建議打開多頭豬。

尸檢應(yīng)該在專業(yè)上關(guān)注生物安全，但尸檢不會(huì)給受感染的農(nóng)場帶來獨(dú)特的疾病危害，而且確實(shí)提供了不那么積極的診斷方法無法獲得的寶貴信息。

Laboratory techniques

PCR: The diagnosis of ASF is usually verified by a positive nucleic acid test and by the ruling out of other common causes of similar lesions. The most common is PCR for the P72 gene. Lung (preferred sample in our lab), kidney, spleen, lymph node, serum, and blood are all excellent test samples for PCR. Oral swabs and oral fluids are extremely popular but the amount of virus is several logs less than what is generally found in blood and tissue, so false-negative results are rather common. Fluorescent qPCR and conventional PCR are employed for testing. Conventional PCR offers a convenient route to gene sequencing.

實(shí)驗(yàn)室技術(shù)

PCR： ASF的診斷通常由陽性核酸試驗(yàn)和排除其他常見的類似病變的原因來證實(shí)。最常見的是P72基因的PCR。肺(實(shí)驗(yàn)室首選樣本)、腎、脾、淋巴結(jié)、血清和血液都是PCR的最佳檢測樣本?？谇皇米雍屯僖悍浅Ａ餍校遣《镜臄?shù)量比在血液和組織中通常發(fā)現(xiàn)的要少一些，所以假陰性結(jié)果是相當(dāng)常見的。熒光定量PCR和常規(guī)PCR檢測。傳統(tǒng)的PCR技術(shù)為基因測序提供了一條方便的途徑。

Where the gene deleted vaccine has been used deliberately or the gene deleted virus strain variant has been introduced accidentally, nucleic acid testing may fail in some animals because the amount of virus that is produced is much lower compared to the wild-type field virus. However, where good samples are available from tissue or blood, a nucleic acid test for the deleted genes of the vaccine virus can be done. After a positive test for the P72 gene, a PCR test for the gene deleted vaccine looking for the presence of DNA from MGF 360 – 505 R and CD2v can be done to determine if the problem virus is the field virus or the gene deleted vaccine virus.

如果基因缺失疫苗是人為故意使用的，或者基因缺失病毒變異株是偶然引入的，那么核酸檢測在某些動(dòng)物身上可能會(huì)失敗，因?yàn)榕c野生病毒相比，產(chǎn)生的病毒數(shù)量要低得多。然而，如果可以從組織或血液中獲得良好的樣本，就可以對疫苗病毒的缺失基因進(jìn)行核酸測試。在對P72基因進(jìn)行陽性檢測后，對基因缺失疫苗進(jìn)行PCR檢測，尋找MGF 360~505 R和CD2v中是否存在DNA，以確定問題病毒是野毒還是基因缺失疫苗病毒。

Loop-mediated isothermal amplification (LAMP) offers a rapid, cheap, flexible, and extremely sensitive nucleic acid alternative that requires little specialized equipment, and seems well-favoured for mass testing such as monitoring/screening at slaughter.

環(huán)介導(dǎo)等溫放大(LAMP) 它提供了一種快速、廉價(jià)、靈活和極其敏感的核酸替代品，幾乎不需要專門的設(shè)備，而且似乎很適合大規(guī)模檢測，如屠宰時(shí)的監(jiān)測/篩選。

Serology may be used to determine if the animals have been exposed to the ASF virus when the time course from infection to testing has been long enough that the period of viremia and presence of virus in the tissues has passed or if good samples from necropsy are not available.

血清學(xué) 可用于確定動(dòng)物是否接觸過ASF病毒，而從感染到檢測的時(shí)間已經(jīng)足夠長，以致病毒血癥和病毒在組織中的存在時(shí)間已過，或無法從尸檢中獲得良好的樣本。

There are a number of ELISA kits available to look for the presence of antibody to P 72, P 30, and other ASF antigens. Such test kits are often used to identify and typically cull groups of females that have been vaccinated deliberately or accidentally exposed to the illegal vaccine virus.

有一些 ELISA法 試劑盒可用于尋找抗P72，P30和其他ASF抗原的抗體。這類試劑盒通常被用來識(shí)別和典型地挑選被故意接種或意外接觸非法疫苗病毒的母豬。

There is an antigen capture ELISA card test, but it is severely lacking in sensitivity, and its use is generally limited to those cases where a quick false negative result is desired.

On histopathologic examination there is a generalized vasculitis with infarction, hemorrhage, and thrombosis in multiple organs, particularly the lung, spleen, lymph nodes, kidneys, brain, and gut. There is massive lymphoid destruction in the lymph nodes and spleen, and vacuolation of alveolar macrophages. Necrosis and ulceration of the colonic epithelium is common (Photo 4).

T檢測卡 是一個(gè)抗原捕獲ELISA卡試驗(yàn)，但它是嚴(yán)重缺乏敏感性，它的使用一般限于那些情況下，快速假陰性的結(jié)果是想要的。

在……上面 組織病理學(xué)檢查 在多個(gè)器官，特別是肺、脾、淋巴結(jié)、腎臟、腦和腸道中，有一種伴有梗死、出血和血栓形成的廣泛性血管炎。淋巴結(jié)和脾臟有大量淋巴樣破壞，肺泡巨噬細(xì)胞空泡化。結(jié)腸上皮壞死和潰瘍是常見的(圖4)。

Photo 4. Vascular thrombosis, infarction, ulceration in colonic mucosa.

圖4.血管血栓形成、梗死、結(jié)腸粘膜潰瘍。

The use of histopathology to verify the typical chronic lesions of the gene-deleted vaccine can be very useful. Pigs that have received those vaccines for ASF will usually have chronic-active healing and fibrosing vascular lesions including thrombi and infarcts in the gut, liver, lymphoid tissues, heart, and kidneys. The lymph nodes may have areas of hemorrhage, necrosis and lymphoid destruction and fibrosing and healing zones. Vaccinated breeding animals may have massive zones of lung necrosis and fibrosis that are often mistaken for chronic APP. The vaccine virus might not kill the pig but the pig is often unable to clear itself of the vaccine virus.

使用 組織病理學(xué)檢查基因缺失疫苗的典型慢性病變 非常有用。接種了ASF疫苗的豬通常會(huì)有慢性活躍的愈合和纖維化血管病變，包括腸、肝、淋巴組織、心臟和腎臟中的血栓和梗死。淋巴結(jié)可能有出血，壞死和淋巴樣破壞，纖維化和愈合區(qū)。接種疫苗的繁殖動(dòng)物可能有大量的肺壞死和纖維化區(qū)域，這些區(qū)域往往被誤認(rèn)為慢性APP。疫苗病毒可能不會(huì)死豬，但豬通常無法清除疫苗病毒。

One should remember that PCR is a great tool but not infallible, and, relative to the actual farm situation, is not 100% accurate. This not to say that PCR is unreliable. Au contraire... but still, PCR results are diagnostic test results not a diagnosis. Thediagnostician is an investigator and should employ all of the tools at his command. When ASF is suspected, some care in biosafety is indicated as always, and even more so. But there are several ASF look-alike diseases and generally speaking a diagnosis of the actual cause of the problem is required in addition to a negative test for ASF, which may require more observational intervention than popping out an inguinal node or exteriorizing the spleen through a keyhole incision.

人們應(yīng)當(dāng)記住，PCR是一個(gè)很好的工具，但不是絕對正確的，而且相對于實(shí)際的農(nóng)場情況，并不是100%的準(zhǔn)確。這并不是說PCR是不可靠的。反差..。不過， P CR結(jié)果是診斷測試結(jié)果，而不是診斷。 這個(gè) 診斷師是一名調(diào)查員，應(yīng)該在他的指揮下使用所有的工具。當(dāng)懷疑ASF時(shí)，生物安全方面的一些關(guān)注將一如既往，甚至更多。但是有幾種ASF看起來相似的疾病，一般來說，除了對ASF的陰性測試外，還需要診斷出問題的實(shí)際原因，這可能需要更多的觀察干預(yù)，而不是通過鎖孔切口突出腹股溝結(jié)節(jié)或脾臟。