| In recent years,the process of large-scale pig farming has been greatly accelerated in China,with the proportion of large-scale pig farming increasing from 45% to 65%.Although large-scale pig farms are far superior to traditional pig farms in terms of hardware facilities and epidemic prevention conditions,the overly intensive farming density poses various difficulties in handling epidemics,often resulting in significant losses.Porcine epidemic diarrhea virus(PEDV)is an important pathogen that causes diarrhea in pigs of different ages.It is one of the most common and high incidence viral diseases in large-scale pig farms,characterized by high pathogenicity and high mortality.Relevant studies have shown that after infection with PEDV,the main diseased organs are the small intestine and stomach.As the infection progresses,the small intestine segment expands,the small intestine becomes congested,the intestinal mucosa falls off,the intestinal wall becomes thin and shiny,and the mesentery becomes congested and edematous;Pathological damage such as congestion at the bottom of the stomach.As an important secreted protein in the body,Ig A can effectively protect piglets from PEDV infection.At the same time,Ig A can be vertically transmitted to piglets through milk secretion,enabling piglets to obtain immunity.That is,high antibody levels of Ig A can protect piglets from PEDV infection or lower the infection and mortality rates,while adult pigs can also reduce PEDV infection by only increasing Ig G antibodies in the serum.Therefore,in addition to doing a good job in biosafety measures,feeding management,daily disinfection,and other work,the most important measures for preventing and controlling PEDV in large-scale pig farms are to regularly monitor the Ig A and Ig G antibody levels of pig herds,timely adjust the immunization plan and conduct real-time detection as needed.In this study,11 standard pig farms,which experienced PED from 2020 to 2022 and being in Shandong and Anhui provinces of a group company,were selected as the research objects.By collecting fecal samples from diarrhoeal pig herds for clinical symptom identification,pathological anatomy,colloidal gold detection,RT-PCR technology to detect pathogens,and through gene sequencing and homology analysis,analysis of epidemic strains of diarrhea in pig farms provides a basis for vaccine selection,strong virus domestication of backup sows,and exploration of the feasibility of delaying delivery with allyl progestin.To monitor Ig A antibodies in colostrum of sows and Ig G antibodies in serum of reserve sows,optimize biosafety measures,adjust immunization plans,and manage reserve pigs,and explore comprehensive prevention and control measures for epidemic diarrhea in large-scale pig farms.The positive rate of PEDV was tested on the samples submitted by each pig farm,among which the incidence rate of sows was 1%-35%;The incidence rate of reserve sows is2%-26%;The incidence rate of suckling piglets is 6%-93%.The results of gene sequencing analysis of PEDV isolates were as follows: Xiajinchang had 99.5% homology with NHTa-2020,Ningjinchang had 99.8% homology with NHTa-2020,and 94.3%-96.2%homology with SD-M;Linyichang has 98.8% homology with SD-M isolate and 96.4%-97.5% homology with NHTa-2020;The homology between Feicheng Farm and NHTa-2020 is99.1%.Dong’echang has 99.8% homology with NHTa-2020 and 96.3% homology with JA1102;Yangguchang has 98.8% homology with NHTa-2020 and 95.3% homology with CV777;Wuhechang has 99.1% homology with NHTa-2020 and 96.7% homology with AH2012;The homology between Xiaoxian Farm and AH2012 is 96.2%;Xiangshanchang has98.7% homology with NHTa-2020 and 95.7% homology with AH2012;Suixichang has98.6% homology with AH-M and 95.6% homology with NHTa-2020.Based on the above sequencing results,a commercially available vaccine with similar homology was selected for each pig farm to optimize the immunization plan,and the group Qingdao Pig Research Institute NHTa-2020 strain of virulent virus was selected for backup pig domestication,with100 pigs per pig farm.According to statistics,the incidence rate of sows is 1%-35%;The incidence rate of reserve sows is 2%-26%;The incidence rate of suckling piglets is 6%-93%,and the death rate is 15%-68%.The piglet mortality rate of sows with 1-2 and 6 or more births is over 24%,and the piglet mortality rate of sows with 3-5 births is controlled within 18%.The mortality rate of suckling piglets is concentrated at 3-8 days and above,with a loss of 48% at 3-8 days,and 37% of piglets are actively killed as worthless pigs above 9days.Through the detection of Ig A and Ig G antibody levels in pig herds,it was found that the smaller the average OD value of antibody,the higher the dispersion of antibody,the higher the incidence rate of pig farms and the mortality of suckling piglets.During the outbreak period of the pig farm,the average OD value of Ig A antibody in colostrum of sows produced was0.897-2.589,the dispersion of Ig A antibody in colostrum was 14-82,the average OD value of Ig G antibody in serum of backup sows was 0.675-2.226,and the Ig G antibody in serum was18-84.After comprehensive prevention and control measures were taken,the average OD value of Ig A antibody in colostrum of production sows was>1.5,the dispersion of Ig A antibody in colostrum was<30,the average OD value of Ig G antibody in serum of backup sows was>1.5,and the Ig G antibody in serum was<30.The antibody level in pigs significantly increased and the uniformity was good.The pre weaning mortality rate of suckling piglets was 4.3%-7.5%,and the average weaning weight was 6.3-7.5Kg,returning to normal levels."The rate of stillbirth after delaying delivery for more than 4 days is more than 22%.The longer the delay,the higher the rate of stillbirth.For more than 6 fetuses,the rate of stillbirth increases positively with the increase in the number of births.As a measure to gain the time of immune response for the body’s emergency immunization,it is not recommended to use allyl progestin during labor to delay the delivery for more than 4 days.By comparing the frequency of PEDV detected in the environment before and after taking comprehensive prevention and control measures,the case fatality rate of pigs,the average OD value and antibody dispersion of Ig A antibody in colostrum,the average OD value and antibody dispersion of Ig G antibody in the serum of reserve pigs,the incidence rate and mortality rate of incidence rate of suckling piglets,and other important data,the following conclusions can be drawn: the incidence rate and mortality rate of pigs are negatively related to the level of body antibody,and the incidence rate rate of pigs with low antibody level is high The mortality rate is high.Comprehensive prevention and control measures can significantly improve the Ig A level in colostrum of sows and the Ig G antibody level in serum of reserve pigs,effectively protecting the safe entry of lactating piglets and reserve sows.Focusing on "raising,preventing,inspecting,and treating" and "eliminating infectious sources,cutting off transmission routes,and protecting susceptible animals",large-scale pig farms continuously improve the health level of pig herds,reduce disease losses,and assist in full production by optimizing biosafety measures,regular monitoring,and timely adjusting immunization plans based on sequencing results,strong virus domestication of backup pigs,feeding back,strengthening daily health care and disinfection,and symptomatic support and treatment. |
PDF Full Text Request