"Hua overflows from the surface, and the pie comes from the quality". Huapai Biotech Group adheres to the development vision of "integrating advanced biotechnology and casting century-old vaccine quality", and strives to make greater contributions to China's animal epidemic prevention, zoonotic disease prevention and control, and animal-derived food safetyIn this issue, we will share the prevention and control measures of porcine respiratory syndrome (PRDC).
Porcine respiratory syndrome (PRDC) is a respiratory disease of the pig caused by both infectious and non-infectious factors, resulting in serious health problems in the pig herd and serious economic losses in the pig farm. Infectious factors include viruses, bacteria, mycoplasma, etc., porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), swine influenza virus (SIV), porcine pseudorabies virus (PRV), Mycoplasma hyopneumoniae (M.).HYO), Pasteurella multocida suis (PM), Haemophilus parasuis (HPS), Streptococcus suis (S. suis).S), pathogens such as Actinobacillus pleuropneumoniae (APP) in pigs, and non-infectious factors include various environmental factors, such as temperature, dust, ammonia, carbon dioxide, bacteria in the air and pig management.
After the occurrence of respiratory diseases in pigs, lung lesions occur, affecting growth performance, feed conversion rate decreased by 10%-30%, pig herd weight gain was slow, and slaughter was delayed by 15-60 daysSecondary or concurrent various viral and bacterial diseases, resulting in an incidence of 40%-80% and a mortality rate of more than 20%.Pigs carry related pathogens for a long time and become the source of infection;The dosage of the drug increases, the cost increases;The use of vaccines has increased, and labor costs have increased. It seriously affects the economic benefits of pig farms, and the economic losses are huge.
1 Pathogen analysis of PRDC.
From 2017 to 2021, Qi Sun et al. analyzed 1307 PRDC disease materials from 269 pig farms in China, PRRSV, PCV2, HPS, SS is the most common pathogenic pathogen in PRDC pigs in China, and the detection rates were as follows. 54%；The detection rate of PRRSV, PCV2 and HPS in piglets was high, and the detection rate of PM and APP in fat pigs was highPRRSV, PCV2 positive herd, PM, HPS, SThe detection rate is higher. The downside is that the survey did not include Mycoplasma hyopneumoniae (M.V.)HYO).
In 2014-2016, Jessica Ruggeri et al. analyzed 1658 PRDC lung samples from 863 farms in Italy, of which 931 were weaned piglets and 727 were fattened pigs (see table below). Weaned piglets are susceptible to S. infections、prrsv、m.H.R. (Mycoplasma hyorhinis) and HPS, MHR (Mycoplasma hyoris hyoris) is the most common pathogen in the lungs of weaned piglets, with a detection rate of 987%；PRRSV, HPS, and SThe detection rates of s in the lungs of diseased weaned piglets were as follows: 3% and 453%, and the detection rate in the lungs of weaned piglets without lesions was respectively. 2% and 348%。
Fattening pigs are more susceptible to PM, S. infectionS, PCV2 and MHYO, where, mHYO and PCV2 were the most common pathogens in the lungs of diseased fattening pigs, with detection rates of 68., respectively5% and 437%；prrsv、s.The detection rates of S and PM in the lungs of diseased fattening pigs were % and 26., respectively3%, and the detection rate in the lungs of fattening pigs without lesions was respectively. 7% and 147%。
2 PRRSV, PCV2 and MAnalysis of the importance of HYO in PRDC.
Jessica Ruggeri et al. analyzed the pathological changes caused by various pathogens of **RDC in Italian pigs from 2014 to 2016. The pathological changes of PRDC mainly include bronchostromal pneumonia (BIP), cataract bronchopneumonia (CBP), interstitial pneumonia (IP), purulent bronchopneumonia (PBP), pericarditis (PE), pleurisy (PL), and pleural pneumonia (PP).
PRRSV caused severe lung and serous lesions, and the detection rate of different lesions in weaned piglets was higher than that in fattening piglets, and the detection rates of PP and PE in weaned piglets were respectively. 7%；The detection rates of CBP and PL in fattening pigs were respectively. 7%；The highest detection rate was PL (66.).7%) and BIP (62.).5%）。
PCV2 was more likely to cause lung and serous lesions in fattened piglets, and the detection rates of PE and CBP in weaned piglets were respectively. 3%, the detection rates of CBP and PBP in fattening pigs were respectively. 3%。
m.HYO did not cause lung and serous lesions in weaned piglets, and the detection rates of PBP and CBP in weaned piglets were respectively. 9%；m.HYO can cause lesions in 65% to 90% of lung and serosa lesions, and the IP detection rate is 444%。
PRRSV, PCV2 and MHYO can cause severe pathological damage in PRDC, cause severe immunosuppression, and secondary severe bacterial infection, which is one of the three important pathogens in PRDC.
2.1 Analysis of the importance of PRRSV in PRDC.
In 2021, Dengshuai Zhao et al. reviewed the relationship between PRRSV and important pathogens in PRDC, and PRRSV has a synergistic effect with other pathogens, which can enhance the replication ability of other pathogens, lead to more severe inflammatory response and pathological damage, and play an important role in PRDC.
2.1.1 Relationship between PRRSV and PCV2.
The co-infection rate of PRRSV and PCV2 is high. In 2019, Chen N et al. tested 159 dead pig samples from 8 provinces and cities in China, and found that the co-infection rate of PRRSV, CSFV, PCV2, and PCV3 (porcine circovirus type 3) reached 1572%；The co-infection rate of PRRSV and PCV2 reached 1069%。Drlet R et al. (2003) study on proliferative and necrotizing pneumonia (PNP) lesions showed that PRRSV and PCV2 co-infection in weaned piglets was up to 42%. Hernandez Reyes et al. in 2018 showed that the test results were 51PRRSV was detected in 9% of cases of multisystem exhaustion syndrome (PMWS) in weaned piglets, and co-infection with PRRSV and PCV2 was detected in farms where lesions occurred. Therefore, we believe that PRRSV and PCV2 co-infection is one of the main causes of circovirus-associated disease (PCVAD).
Niederwerder MC et al. (2016) mentioned that both PRRSV and PCV2 target the immune cells of the host, disrupting their immune function, leading to increased susceptibility to primary and secondary pathogens, which may affect host growth performance and the morbidity and mortality of related diseases. In a 2013 study, Fan P et al. found that piglets had the highest viral load and the most severe clinical signs after PCV2 vaccination 1 week after HP-PRRSV, with a mortality rate of 60%.In further studies, it was found that PCV2 infection in pigs infected with HP-PRRSV enhanced the replication of both viruses and led to more severe clinical signs and lesions. These results suggest that there is a synergistic effect in PRRSV and PCV2 co-infection.
2.1.2 Relationship between PRRSV and CSFV.
The co-infection rate of PRRSV and CSFV in intensive pig farms is low, but PRRSV infection in the field can lead to CSFV vaccination failure. Chen et al. (2019) hypothesized that PRRSV infection led to the upregulation of pro-inflammatory cytokines in vitro, specifically TNF-, and inhibition of CSFV replication, which was the reason for the failure of PRRSV-induced swine fever vaccination. However, there were no data from in vivo experiments in the study, and the cells used were PAM39, a cell line based on 3D4 21, which was not primary cultured cells. It is still difficult to select a suitable model for co-infection studies, and as a result, the lack of suitable host cells limits this study.
2.1.3 Relationship between PRRSV and SIV.
Pol JM et al. (1996) demonstrated that co-infection with PRRSV and SIV resulted in more severe inflammation of the bronchial wall, but PRRSV had little effect on SIV replication. A 2003 study by Choi YK et al. showed that 109 PRRSV-positive samples were detected in 636 SIV-positive cases, with a co-infection rate of 17%, and that PRRSV and SIV co-infection led to more severe clinical symptoms and growth retardation.
2.1.4 Relationship of PRRSV to HPS.
PRRSV infection can predispose pigs to secondary infections by destroying PAM cells and inducing inflammation of the nasal mucosa. The high detection rate of HPS in PRRSV-infected pig farms suggests that PRRSV infection increases susceptibility to HPS. K**Anova L et al. (2015) confirmed that co-infection with PRRSV and HPS can increase the expression of pro-inflammatory cytokines such as TNF-, IL-1, IL-8 and other pro-inflammatory cytokines in PAM cells, and at the protein level, it was also confirmed that co-infection with PRRSV and HPS increases IL-1 levels. At present, L1 PRRSV is the dominant strain in the pig herd, which is easy to mutate and recombine, and good prevention and control of PRRS plays an important role in the prevention and control of HPS.
2.1.5 PRRSV with Ss.
Auray G et al. (2016) confirmed that PRRSV infection can increase the risk of SSusceptibility, PRRSV infection inhibits the cellular immune function of PAM and affects the clearance of S. in pigsThe ability of the s, resulting in sS spread more widely in tissues, more severe clinical symptoms appear, and morbidity and mortality increase;The study did a detailed study of inflammatory factors, PRRSV infection after SSecondary infection led to additive effects of CCL4, CCL14, CCL20, and IL-15, and the synergistic effect of IL-6, CCL5, and TNF- was significantly upregulated, SSecondary infection enhances the inflammatory response mediated by PRRSV infection.
s.Early infection with S can increase the clinical symptoms of PRRS. Sun Yf et al. confirmed in 2020 that early infection with SS increases the virulence of the HP-PRRSV MLV-like strain, causing an excessive inflammatory response and tissue damage, leading to increased morbidity and mortality in piglets.
2.2 Analysis of the importance of PCV2 in PRDC.
2.2.1 PCV2 causes severe immunosuppression.
In 2013, Xiang-Jin Meng discussed the immunosuppression caused by PCV2, which showed that PCV2 infection and replication in lymphoid tissues can damage the structure of lymphofollicles, leading to lymphocyte failure and being replaced by histiocytes, and PCV2 can lead to severe immunosuppression by destroying lymphofollicles and reducing the number of white blood cells. The severity of lymphocyte failure is positively correlated with the number of PCV2 antigens detected in the affected tissues. Evidence of PCV2 replication has been confirmed in the bronchial and inguinal lymph nodes, tissues of the bronchi, tonsils, lungs, liver, kidneys, spleen, and thymus. In PRDC, PCV2 causes immunosuppression, which is very susceptible to various bacterial diseases, leading to increased mortality in the herd.
2.2.2 PCV2 causes serious secondary infections.
From 2017 to 2019, Haodan Zhu et al. analyzed 898 lung and nasal swab samples from eastern provinces of China, PRRSV, PCV2, HPS, and SThe detection rates of S and APP in lung samples were as follows. 5% and 11%；Concurrent and secondary infections caused by PCV2 are severe, PCv2+PRRSV 478%、pcv2+s.s 18.1%、pcv2+hps 1.1%、prrsv+s.s 21.3%、s.s+hps 2.1%、pcv2+prrsv+s.s 14.9%、pcv2+s.s+hps 1.1%。
2.3 Mycoplasma hyopneumoniae (m.).Analysis of the importance of HYO in PRDC.
2.3.1 m.HYO is the most important bacterial pathogen in PRDC.
Mycoplasma hyopneumoniae (M. hyopneumoniae)HYO) itself can cause bronchiciliary degeneration and an overreaction of the local immune system in the lungs, triggering a strong inflammatory response that causes lung damageDestruction of cilia leads to dysfunction of the mucociliary defense system;Loss of mucociliary apparatus and failure of mucosal clearance results in increased colonization of Pasteurella multocida and other secondary bacteria;In addition, infection m. was foundHYO inhibits the efficiency of phagocytic cells in the lungs;m.HYO impairs the respiratory tract's ability to respond to other pathogens and increases the severity and duration of respiratory illnesses induced by other pathogens.
2.3.2 m.Synergy between HYO and PCV2.
Opriessnig et al. confirmed in 2004 that pigs were infected with M. firstHYO, reinfection with PCV2, makes the lung and lymphoid tissue damage caused by PCV2 more severe, resulting in more severe PCVAD. SEO et al. confirmed in 2014 that under test conditions, mHYO caused more severe PCV2 viremia, but PCV2 had no effect on the symptoms of Mycoplasma suis pneumonia;Six-week-old pigs were immunized with Mycoplasma hyopneumoniae vaccine and circovirus type 2 vaccine, followed by MHYO and PCV2 challenged, and no synergistic clinical symptoms appeared. Chae et al. confirmed in 2005 that M. was infected firstHYO leads to enhanced PCV2 replication, severe pathological damage, and more severe PCVAD, so immunization against Mycoplasma hyopneumoniae vaccine reduces M. mPCV2 replication was enhanced and pathological damage was severe due to HYO infection.
2.3.3 m.Synergistic effect of HYO with PRRSV.
Park et al. confirmed in 2014 that MHYO potentiates pneumonia caused by PRRSV, whereas PRRSV does not enhance MPneumonia caused by HYO. Compared with PRRSV alone, there was a significant difference in PRRSV and MHYO mixed infection, mHYO is able to increase the level of PRRSV viremia. In PRRSV and MIn HYO co-infection, PRRSV does not enhance MProliferation of HYO.
Moreau confirmed in 2004 that PRRSV and MIn hyo-over-infected pigs, the degree of pneumonia and viremia caused by PRRSV remained low, in order to reduce the level of viraemia caused by PRRSV and MLung inflammation in HYO dual infection, which can be immunized against Mycoplasma hyopneumoniae pneumonia vaccine before weaning, can reduce the replication (viral load) of PRRSV virus in pigs with double infection and improve production performance. So in real production, in PRRSV and MIn the HYO dual-infection herd, immunization against Mycoplasma suis pneumonia vaccine can reduce the harm caused by PRRSV infection.
3 Prevention and control measures of PRDC.
Comprehensive measures should be taken to prevent and control PRDC, mainly including the following aspects: strict biosecurity measures, strengthening feeding management, effective control of secondary infections, and immunization of important diseases.
3.1 Strict biosecurity measures.
Farm biosecurity is the foundation of all disease prevention and control, and is the most effective and lowest-cost health management measure. Large-scale pig farms should do a good job in biosecurity monitoring and evaluation according to the pressure of disease prevention and control in pig farms, do a good job in personnel training, implement production safety measures in place, strengthen the control of **, vehicle flow, logistics, water, feed, pig flow and harmful organisms, cut off the transmission route, and prevent the introduction of new strains. It is forbidden to introduce positive replacement breeding pigs to ensure that foreign boars** are not poisonous. According to the actual situation of the pig farm, formulate scientific and effective biosecurity measures.
3.2. Strengthen feeding management.
Do a good job in the domestication of gilts with PRRS, introduce double-negative gilts, and avoid multi-batch, multi-**, and large-scale introduction. Through vaccine immunization, the acclimation time is guaranteed, and antibodies and antigens are detected many times before mixing, and antibodies and antigens can only be mixed after they are qualified.
Do a good job of heat preservation, ventilation and humidity control, reduce the stress caused by high temperature and temperature difference, and discharge all kinds of harmful gases in timeMulti-point feeding, all-in, all-out, early weaning, reducing feeding density, etc.;Improves reproductive rhythms;Ensure that the gestational age structure is reasonable;To ensure nutrition, pigs are fed with feed with different nutritional values at different stages.
3.3. Effective control of secondary infections.
Effective drugs are indispensable measures for the prevention and control of PRDC, and the selection of appropriate drugs can carry out three-shot health care for piglets, and carry out drug health care before and after weaning and fattening stage, so as to improve pig immunity, reduce stress and reduce secondary infection.
3.4. Do a good job of immunization against important pathogens.
prrsv、pcv2、m.HYO is the three most important pathogens of PRDC, and it is necessary to do a good job of immunization. Huapai Biotech has a mature and effective combined immunization program for PRRS, ring and mycoplasma.
3.4.1 PRRS Double Blue Combination Immunization Regimen.
Gilts: 120-140 days old immunized 1 head of Blue Jingling, with an interval of 3-4 weeks, 1 part of Blue Jingling + 2ml of Huatai Blue.
Multiparous sows: unstable field (1414 program): first health care for 1 week, immunization of Lan Jingling 1 head, 7 days apart, and then health care for 1 week, Lan Jingling 1 head + Hualantai 2ml;
Stable field (1441 program): 14 days postpartum immunization of 1 head of Lanjingling, 40-50 days of pregnancy Hualantai 2ml;Or Lan Jingling and Hua Lantai alternate immunity.
Piglets: 14 days old, 1 head of Lan Jingling, 28 days old Hua Lan Tai 2ml;Or 2-3 weeks old, 1 head of Lanjingling + 1ml of Hualantai.
3.4.2 Circular and mycoplasma immunization protocols.
Gilts: 3-4ml of Huanhuankang + Zhilungtong mixed injection, or 1ml of Yuanzhitai.
Multiparous sows: Huanhuan Kang 2ml, 3 times a year.
Piglets: Severely infected: 7-14 days old, 1ml of Huanhuan Kang + 1ml of Zhilungtong, or 1ml of Yuanzhitai;21-28 days old: Huanhuan Kang 1ml + Zhilungtong 1ml, or Yuanzhitai 1ml.
Field with low infection pressure: 14-21 days old, 1ml of Huanhuan Kang + 1ml of Zhilangtong, or 1ml of Yuanzhitai.
3.4.3 Combined Immunization Regimen of Cyclozhilan Radius.
Gilts: 120-140 days old: Yuanzhitai 1ml + Lanjingling 1 head;At an interval of 3-4 weeks, 1ml of Yuanzhitai + 1 head of Lanjingling 2ml of Hualantai.
Multiparous sows: Huanhuankang 2ml + Lanjingling 1 head, Yuanzhitai 1ml + Hualantai 2ml, alternately immunized every 3 months.
Piglets: 14-21 days old, 1ml of Yuanzhitai + 1 head of Lanjingling + 1ml of Hualantai.