Investigation And Analysis Of Toxoplasma Gondii Infection In Chicken Products In Shandong Province

Toxoplasma Gondii is an obligate intracellular parasitic protozoan.It is an important zoonotic pathogen.It has many host types and is popular worldwide.It has potential threat for healthy development of human health and animal husbandry.Meat products carrying Toxoplasma gondii are one of the most important ways for humans to infect Toxoplasma gondii.Therefore,understanding the infection of Toxoplasma gondii in livestock and poultry has a very important public health significance.Shandong Province is a province with a large population and a large chicken farm.Chicken meat products are one of the main meat products of Shandong residents,and the consumption is very large.The food safety issue of chicken products has always been the focus of public attention.At present,there are many investigations on the infection of Toxoplasma gondii in poultry at home and abroad,but there are few studies on Toxoplasm a infection in poultry farming in Shandong Province.In 2000 and 2008,there were reports of Toxoplasma gondii infection in Shandong Province,but the sample size was small and there was a lack of comparison of Toxoplasma infection rates in different culture methods.In addition,the results of the investigation of Toxoplasma infections do not fully reflect the safety risks of food,because most of the chicken products sol don the market have been frozen,and Toxoplasma may lose or reduce the ability to infect after freezing.In order to understand the infection of Toxoplasma gondii in chicken products in Shandong Province and conduct corresponding food safety risk assessment,this study collected 1653 samples of large-scale cultured and free-range chickens from eight prefecture-level cities in Shandong Province for investigation of Toxoplasm a gondii infection.The differences in Toxoplasma infections between large-scale culture and free-range breeding methods were compared,and the food risks were evaluated by mouse infection experiments.This study has been divided into three parts:1.Nested PCR to detect Toxoplasma infection.With the Toxoplasma gondii ITS-1gene as the target gene,the primers were optimized and improved based on the toxoplasma nested PCR detection method in this laboratory,and the PCR reaction system and reaction conditions used in this study were determined.2.Investigation of Toxoplasma infection in parts of Shandong Province.In this study,1653 chicken heart samples were randomly collected from more than 20 counties in 8 prefecture-level cities including Linyi City,Weifang City,Liaocheng City,Binzhou City,Yantai City,Weihai City,Heze City and Zibo City.Phenol-chloroform-isoamyl alcohol extraction of sample DNA as a template for molecular biological detection using established nested PCR.The PCR results showed that 204 of the 1653 chicken heart samples accounted for 12.34% of the positive samples.The experimental results show that the infection of Toxoplasma gondii in chickens is common in Shandong Province.The positive rates of Linyi City,Weifang City,Liaocheng City,Binzhou City,Yantai City,Weihai City,Heze City and Zibo City are 13.33%(36/270).),20.98%(64/305),6.67%(12/180),9.23%(12/130),7.69%(13/143),11.11%(30/270),9.41%(16/170),10.73%(22/205),the positive rate ranged from 6.67% to 20.98%,and the positive rate of Toxoplasma gondii infection in different regions was significantly different(P<0.05).Further statistical analysis was carried out on the detection rate of Toxoplasm a gondii in the samples of large-scale cultured and free-range chicken products.The results showed that the infection status of Toxoplasma gondii under different culture methods was quite different,among which the large-scale cultured chicken products Toxoplasma gondii The infection rate was 9.33%,and the detection rate of Toxoplasma gondii in free-range chicken products was 14.95 %.There are also large differences in the detection rates of Toxoplasma gondii in large-scale farming and free-range chicken products.The positive rates of Toxoplasma gondii infection in large-scale breeding in Linyi City,Weifang City,Liaocheng City,Binzhou City,Yantai City,Weihai City,Heze City and Zibo City were 10.83 %,13.13 %,5.56 %,5.00 %,6.66 %,9.17 %,7.78 %;the positive rates of free-range chickens were 15.33%,29.65%,7.78%,12.86%,10.84 %,12.67 %,11.25 %,11.85 %.The results showed that the infection rate of Toxoplasma gondii in the free-range chickens in Shandong Province was significantly higher than that in the large-scale farmed chickens.This may be due to the high probability of contact with polluted water sources and feeds by free-range feeding methods,which reflected the environment to some extent.Toxoplasma contamination.3.Mouse infection experiments.Chickens infected with Toxoplasma gondii in the sample were infected with mice to assess their food safety.A portion of the PCR-positive samples from large-scale culture and free-range chicken products were picked for tissue mashing,and the mashed samples were inoculated with SPF Kunming rats by or al or intraperitoneal injection.Each sample was blindly transmitted for three generations.The heart,liver,spleen and brain tissue of Kunming rats were detected by nested PCR method for each generation,and the infection of Toxoplasma gondii was detected by each method.The PCR results showed that Toxoplasma was not detected from the tissues and organs of the mice,and the cysts of the Toxoplasma gondii or other stages of the worms were not found in the tissue sections.This may be due to the loss of reinfection capacity of the Toxoplasma gondii carried by the frozen chicken products marketed.This study investigated the infection of Toxoplasma gondii in large-scale farmed chickens and free-range chickens in more than 20 counties in eight prefecture-level cities in Shandong Province,and evaluated the safety risks of foods through mouse infection experiments.The results showed that Toxoplasma infection was common in the tested chickens,and the infection rate of the free-range chickens was significantly higher than that of the large-scale chickens.This indicates that the culture method has certain influence on the infection of Toxoplasma gondii.In addition,cryopreservation may reduce the ability of Toxoplasma to infect muscle tissue.