1.最近的一項(xiàng)研究再次證實(shí)：胞內(nèi)勞森氏菌存在于大多數(shù)歐洲畜群中

最近對(duì)去年暴發(fā)腹瀉的144個(gè)歐洲豬群進(jìn)行的一項(xiàng)調(diào)查發(fā)現(xiàn)，高達(dá)90%的豬群曾接觸過胞內(nèi)勞森氏菌。¹。從這項(xiàng)研究中可以清楚地看出，胞內(nèi)勞森氏菌普遍存在，而且是一個(gè)非常嚴(yán)重的問題。

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2.受感染的豬會(huì)迅速感染豬舍中的其他豬

在評(píng)估未接種疫苗的豬體內(nèi)勞森氏菌的傳播率時(shí)，科學(xué)家們表明，一只被感染的豬每周能夠感染三頭易感豬。²。在未受保護(hù)的豬群中，受感染豬的數(shù)量每周可以增加三倍。?

3.接種疫苗可減少勞森氏菌胞內(nèi)傳播

重要的是實(shí)施系統(tǒng)的疫苗接種計(jì)劃，以減輕回腸炎的傳播以及相關(guān)的生長遲緩情況。在一項(xiàng)研究中²，與未受保護(hù)的豬群相比，口服活疫苗可以顯著降低傳播率。

4.局部免疫對(duì)于防止胞內(nèi)勞森氏菌至關(guān)重要

胞內(nèi)勞森氏菌感染僅限于腸道，這就是為什么局部免疫 - 即僅限于特定器官或組織的免疫 - 至關(guān)重要的原因。一種理想的針對(duì)回腸炎的疫苗應(yīng)該能夠引發(fā)平衡的免疫反應(yīng) - 包括局部免疫和細(xì)胞免疫 - 從而消除病原體。口服疫苗已被證明可在腸道層面誘導(dǎo)早期局部免疫。³。

5.胞內(nèi)勞森氏菌感染對(duì)腸道微生物組的破壞會(huì)對(duì)豬的健康和生產(chǎn)力產(chǎn)生廣泛的影響

眾所周知，腸道消化菌群（或微生物群）會(huì)影響豬的健康和生產(chǎn)力，而胞內(nèi)勞森氏菌感染似乎會(huì)產(chǎn)生令人不安的影響。感染會(huì)增加對(duì)沙門氏菌的易感性。⁴。這對(duì)你的養(yǎng)殖場來說意味著什么？很簡單：胞內(nèi)勞森氏菌的行為就像是其他病菌的開門者。

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6.口服疫苗可減少胞內(nèi)勞森菌的脫落，并影響微生物組?

接種了疫苗的豬的微生物群落似乎與未接種疫苗和患病豬的微生物群落不同⁵。這種變化與胞內(nèi)勞森氏菌糞便脫落的急劇減少有關(guān)，表明口服疫苗可以對(duì)腸道微生物組的組成、豬的生產(chǎn)能力和病原體的傳播產(chǎn)生積極影響^6,7。

7.豬肉生產(chǎn)商需要針對(duì)回腸炎采取定期控制措施

所有這些科學(xué)發(fā)現(xiàn)對(duì)你的養(yǎng)殖場意味著什么？隨著我們減少對(duì)抗生素的依賴，很明顯我們需要對(duì)胞內(nèi)勞森氏菌實(shí)施定期控制措施。口服疫苗是一種簡單、對(duì)豬友好、有效且具有成本效益的方法，可減輕養(yǎng)殖場的回腸炎負(fù)擔(dān)?？梢宰稍兡愕墨F醫(yī)，了解如何為你實(shí)施最佳控制方案。

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參考文獻(xiàn)

¹?Arnold et al 2019:?Prevalence of Lawsonia intracellularis in pig herds in different European countries (nih.gov)

²?Vasquez et al, 2019: Impact of vaccination on transmission of Lawsonia intracellularis

Erika Vasquez¹?; Robert Valeris¹?; Dana Beckler²?; Fabio Vannucci¹?
50th Annual Meeting of the American Association of Swine Veterinarians (Orlando; March 9-12, 2019)
¹College of Veterinary Medicine, University of Minnesota;?²Gut Bugs, Inc, Minnesota?

Experimental design
A seeder-pig sentinel model was used (Figure 1). Ninety pigs were divided into three groups: orally vaccinated (Enterisol Ileitis); intramuscularly vaccinated (Porcilis Ileitis) and non-vaccinated. Day 21 post-vaccination, nine seeder pigs were challenged with L. intracellularis. Day 7 post-inoculation, seeder pigs were commingled as described in Figure 1.
Transmission rate and expected probabilities of shedding were assessed with the susceptible-infectious model. Animals were considered infectious when fecal quantitative polymerase chain reaction was equal or more than 103L. intracellularis per gram of feces (Collins et al, 2001).
In practical terms, this would roughly represent a threshold cycle of 31 or less based on the PCR assay offered by the University of Minnesota Veterinary Diagnostic Laboratory.

Results and practical implications

• Vaccination against L. intracellularis has been applied over the years with successful reduction of the clinical signs and fecal shedding, and resulting in significant improvement of growth performance in vaccinated animals.
• The assessment of the transmission rate under a non-vaccinated scenario showed that one infectious pig (shedding more than 103 bacteria per gram of feces) is able to transmit L. intracellularis to three susceptible pigs per week.
• From a practical standpoint, if pigs from infected and na?ve flows are commingled at 10 weeks of age (end of the nursery phase) the number of infected pigs triplicate within the population every week.
• The results revealed that the chronic nature of the Lawsonia infection at the individual level is also reflected in the transmission of the disease at the population level characterizing a prolonged spreading of the infection in the finishing barn.
• Although the Lawsonia infection can impact the productive performance in the first weeks of the finishing phase when na?ve pigs just started getting infected, the clinical diagnosis is only evident when most of the na?ve population is infected and some animals are exhibiting diarrhea. This typical clinical scenario is usually observed only at later stages of the finishing phase when the animals are approaching the marketing age and it can misrepresent the actual impact of the disease in terms of performance throughout the growing-finishing phase.
• In the present study, transmission rates were significantly reduced in both vaccinated groups: 1.8 infected pig per week in the orally-vaccinated and 1.7 infected pig per week in the intramuscularly-vaccinated group.
• The model used to predict transmission over time also showed decreasing in the period of fecal shedding of Lawsonia in both vaccinated groups. While the median period of shedding in non-vaccinated animals was 11.2 weeks, orally- and intramuscularly-vaccinated animals showed 6.3 and 8.3 weeks, respectively.

These results highlight the importance of implementing vaccination programs at system level rather than site-specific interventions. This strategy prevents the risk of commingling batches of pigs from vaccinated and non-vaccinated sources, therefore reducing the impact of the disease in downstream flows.

³?Nogueira et al, 2013:?Immunological responses to vaccination following experimental Lawsonia intracellularis virulent challenge in pigs - ScienceDirect

⁴?Beloeil et al, 2004:?Risk factors for Salmonella enterica subsp. enterica shedding by market-age pigs in French farrow-to-finish herds - ScienceDirect

⁵?Guevarra et al, 2021:?Oral Vaccination against Lawsonia intracellularis Changes the Intestinal Microbiome in Weaned Piglets

⁶?Leite et al, 2021:?Frontiers | Oral Vaccination Reduces the Effects of Lawsonia intracellularis Challenge on the Swine Small and Large Intestine Microbiome | Veterinary Science (frontiersin.org)

⁷?Helm et al, 2021:?Lawsonia intracellularis infected enterocytes lack sucrase-isomaltase which contributes to reduced pig digestive capacity | Veterinary Research | Full Text (biomedcentral.com)