Cao Bairong Assistant Veterinarian
Abstract: Based on the introduction of five common clinical pathogens of pigs and their harms, the study explored the clinical detection methods of these pig disease pathogens in order to provide reference and reference for related work and researchers.
Keywords: swine disease pathogen; hazard; clinical diagnosis method
1 Physiological characteristics and hazards of common clinical pig disease pathogens
1.1 swine fever virus and its hazards
Swine fever disease, also known as pig cholera disease, is a type of pig fierce transfection disease that seriously endangers the development of the pig farming industry. It is listed as a first-class infectious disease in pig in my country. The pathogen that causes the disease is swine fever virus (CSFV), and the genetic material is a single strand of positive-strand RNA virus. Its virus is spherical and has a capsule structure. The genus of Swine Fever Virus is the genus of the Flaviviridae family. Through epidemiological investigations and gene sequence analysis, the main genomic type 2 swine fever virus is currently prevalent in my country. The epidemic characteristics have undergone major changes, and its clinical symptoms are difficult to distinguish from other pig diseases. The most important thing is that this type of swine fever virus is the main source of infection in large-scale pig farms, which will cause reproductive disorders in sows and immune tolerance of piglets born.
1.2Pig Circovirus and its hazards
Pig Circovirus (PCV) was discovered in 1974 and is a new virus belonging to the genus Circovirus of the Circovirus family. The genetic material of the pig circovirus is single-stranded circular DNA. Its particle shape is icosahedral symmetric and has an encapsular structure. It is the smallest animal virus known at present. The clinical symptoms of pig circovirus are called multisystem failure syndrome (PMWS) in weaned piglets. With the development of scientific research, people's research on PCV has gradually deepened. According to the viral gene sequence and pathogenicity and virulence, PCV can be divided into two serotypes: PCV-1 and PCV-2 [1]. At present, scholars from all over the world have unanimously confirmed that the similarity of PCV gene sequences of the same serotype can reach more than 90%. PCV-2 is the main pathogen of PMWS, that is, PCV-2 is pathogenic, while PCV-1 is not pathogenic. Studies have shown that the PCV-2 virus can spread horizontally and vertically. PCV-2 infection can damage the body's immune cells, resulting in low immunity [2]. Moreover, PCV-2 virus often causes mixed infections and secondary diseases with other pig pathogens, causing large-scale outbreaks and pandemics, such as swine fever virus, blue ear disease poison, pig pseudorabies poison, etc.
1.3Pig Blue Ear Disease Toxicity and Its Hazards
Pig Blue Ear Disease, also known as pig reproductive and respiratory syndrome (PRRS), is the most serious type of pig diseases. Pig blue ear disease was discovered in the southern United States in 1987, and its pathogen PRRSV was first isolated by Chinese scholar Guo Baoqing in 1996. The main clinical symptoms of blue ear disease in pigs are caused by reproductive disorders in adult sows and respiratory lesions in piglets. The PRRSV virus is spherical and is wrapped in a capsule outside. The genetic material is a single strand of RNA. According to the differences in genomic sequences, PRRSV virus can be divided into two genotypes, namely the North American strain and the European strain. At present, my country's diseased pig herds have coexisting American and European types, which has caused huge impacts and losses to the pig breeding industry.
1.4Pig infectious gastroenteritis virus and its hazards
Pig infectious gastroenteritis (TGE) is a highly contact-based infectious disease mainly caused by pig infectious gastroenteritis virus (TGEV). TGE first broke out in the United States in 1945 and was infected in mainland my country in 1956. TGEV virus particles are varied, have a capsular structure, and the genetic material is a single strand of positive strand RNA, which belongs to the Coronavirus family and the Coronavirus genus. Pigs are the main susceptible animals of TGEV, and the mortality rate after infection can reach 100%. The emergence and rapid spread of PRCV pose a huge threat to the development of the pig farming industry.
1.5 vesicular stomatitis virus and its hazards
vesicular stomatitis (VSV) was first discovered in the eastern United States in 1801. The genetic material of vesicular stomatitis virus is a single negative strand RNA, which proliferates extremely rapidly and is listed as a legally reported animal disease by International Bureau of Ecological Epidemics (OIE). blister stomatitis can infect multiple parts of animals, and blisters and ulcers will appear at the infected areas. The clinical symptoms are very similar to foot-and-mouth disease.Moreover, blister stomatitis can also infect humans by infected animals, causing human diseases, so it is listed as a Class II infectious disease in my country. From the perspective of epidemics, droplet transmission, mosquito bites, etc. are the main transmission channels of blister stomatitis, and the disease mostly breaks out seasonally, with the frequent period from summer to late autumn. After being infected with VSV, people will experience symptoms similar to acute colds. In people with weak resistance, symptoms of viral encephalitis may also occur. If not treated in time, it will cause triggering infection or even death.
2 clinical detection and diagnostic methods discuss the isolation and culture of pathogens
2.1
This method is currently a commonly used clinical pathogen detection method and has high accuracy. Pig disease pathogens generally include viruses, bacteria and mycoplasma. The tissue supernatant or serum inoculation of corresponding sensitive cells for culture. The specific steps are shown in Figure 1. However, the isolation and culture methods of pathogenic bacteria also have their shortcomings. First, it takes a long time; secondly, some bacterial culture conditions are harsh, and it is difficult for ordinary laboratories to meet the corresponding culture requirements; thirdly, accurate judgment and testing cannot be carried out independently, and other testing methods are needed to assist, and missed detection and missed detection may occur, delaying the prevention and control time of epidemic prevention and control; fourthly, it is difficult to adapt to the current complex and changing epidemic forms, and at the same time, multiple pathogens are tested.
Figure 1 Analysis and culture steps for viral pathogens of pig diseases
2.2 Polymerase chain reaction method
This method has strong specificity, high sensitivity, easy operation, time and effort, and is widely used in the diagnosis of epidemics. This method is a method of synthesizing specific DNA fragments through enzymatic reactions in vitro. Multiplex PCR is developed based on conventional PCR technology. It is efficient and purposeful, and can achieve simultaneous detection of multiple pathogenic microorganisms, providing more, more accurate and faster diagnostic information for clinical testing. However, this technology cannot completely get rid of the problem of false positive .
2.3 ELISA method
Currently, the application technology of this method is relatively mature, has high sensitivity, and is widely used in the detection of epidemics. The principle is usually to immobilize the antigen in a solid phase carrier, and then add a primary detection antibody to form a complex form of an antigen antibody. However, this method cannot distinguish between natural infection or antibodies produced by vaccination, and is prone to misidentification.
2.4 Loop mediated isothermal amplification
Loop mediated isothermal amplification reaction is a new gene diagnosis technology and is one of the detection technologies with higher sensitivity. Loop-mediated isothermal amplification does not require special instruments in clinical use, and the operation is very simple. However, a major disadvantage of this technology is that the false positive problem is relatively serious, and this method cannot meet the current requirements of mixed disease monitoring.
2.5 Gene chip technology
Gene chip technology, also known as DNA chip technology, has the advantages of high throughput, high sensitivity, accuracy, and speed and simplicity. However, if the chip's signal has a range, it will bring relative errors and be expensive.
3 Conclusion
my country is a major pig breeding country, and its pig output rate ranks first in the world. However, in recent years, the trend of swine disease infection to mixed infection and secondary infection of multiple types of pathogens has not only greatly affected and restricted the development of my country's pig breeding industry, but also posed a huge threat to human health. Research on its hazards and detection methods not only has strong clinical practical value for the detection of pig disease pathogens, but also helps promote social public health security and promote stable and sustainable development of human health.
References
[1] Yin Zhen, Liu Jinghua. Animal Virology [M]. 2nd Edition. Beijing: Science Press, 1997.
[2] Zhou Jiyong, Chen Qingxin, Ye Juxiu et al. Serological analysis of pig circovirus type 2 infection [J]. Chinese Veterinary Medicine, 2004, 24(1): 1-3.
10
000
