the cause of brucellosis, what are the causes of brucellosis

the cause of brucellosis, what are the causes of brucellosis

  • 2021-10-19 12:51:15
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  1. brucellosis Examination, brucellosis Diagnosis
  2. brucellosis Nursing-Nursing Precautions-Diet Taboo

Causes of Brucellosis

1. Causes of disease

Brucella is an inactive, tiny, gram-negative coccus multiforme, without capsules, flagella, spores and natural plasmids. According to the classification scheme announced by the Brucella Special Committee in 1985, Brucella can be divided into six biological species and 19 biotypes, namely sheep species (Br.melitensis) (biotypes 1 to 3), and cattle species. Species (Bruce abortus, Br.abortus) (biotypes 1-7, 9), pig breeds (Br.suis) (biotypes 1-5), and sheep epididymal species (Br.ovis) (biotypes 1) , Gerbil species (Br.neotomae) (biotype 1), dog species (Br.canis) (biotype 1). The reason why there are many biotypes of this bacteria may be due to the fact that the same biotype can reproduce in different kinds of hosts, and thus a variety of genetic mutations have occurred. For example, in a mixed grazing area, cattle 1, cattle 3, cattle 7, and cattle 9 have been isolated from sheep. Niu 1 and Niu 6 have been isolated from pigs. This bacterial classification has the greatest significance for the clinical and epidemic disease species, sheep, cattle, and pigs. The other three species only infect humans by dog ​​species, while sheep epididymal species and gerbil species are rare to infect humans. From a clinical point of view, cattle breeds have the weakest pathogenicity among the six biological species, with mild or even asymptomatic symptoms after infection, often sporadic; sheep breeds have the strongest pathogenicity, with heavier symptoms after infection, which can cause Outbreak. The pathogenicity of the various strains is also different, the attenuated strains and the various strains of the cattle breed are weak, while the virulent strains of the sheep and pig breeds are strong. From an epidemiological perspective, classification is more important. Such as tracing the source of infection, epidemiological investigation, etc. There are mainly three types of sheep, cattle, and pigs found in China. Sheep breeds are the main prevalence, followed by cattle breeds. Pig breeds are only popular in a few areas. For dog breed infections, it has been discovered in recent years that dog breed infections have also occurred in many areas of China, and the infection rate can reach 7. 5%, the population infection rate is also higher, but relevant information needs to be further confirmed. The growth of this bacteria has higher nutritional requirements. However, even under good culture conditions, the growth is still slow, so it can be judged as negative if it is cultured for at least 4 weeks and still grows aseptically. This bacteria is an aerobic bacteria, but when the pig breed grows, especially the first generation culture, it needs 5%-10% carbon dioxide. Brucella has strong vitality in the natural environment and can be spread through many ways. Because the bacteria exists in aborted fetuses, afterbirths, amniotic fluid, vaginal secretions of aborted female animals and semen of male animals, it is mostly through contact with the discharge of abortion It is spread by breast milk or mating, so people who have a lot of contact with sick livestock and people in pastoral areas are more susceptible to the disease. The bacteria can survive in the secretions and excrements of sick animals and in the organs of the animals for about 4 months, in milk for 18 months, and on the fur for 4 months. However, it is more sensitive to the commonly used physical and chemical disinfection methods. Generally, the commonly used disinfectants can quickly kill them, and the 3% chlorinated lime clarified liquid can kill them in a few minutes. According to this characteristic of the army, suitable disinfectants can be selected to disinfect and prevent the epidemic area. In addition, Brucella is sensitive to heat, moist and heat at 60℃ for 10-20 minutes or exposed to sunlight for 10-20 minutes. There are common antigens among all kinds of this bacteria, so an effective vaccine has a preventive effect on all kinds. Under the action of antibiotics, the bacteria can become L-type, which can exist in the body for a long time and can be reversed to the normal type. This may be related to recurrence. Therefore, when antibiotics are used to treat the disease, the choice is to avoid drug resistance. Combination medication.

2. Pathogenesis

There is a lot of research, but it has not been fully elucidated so far. The material basis of the virulence factor of this bacteria is LPS, outer membrane protein (OMP) and certain virulence-related factors (such as catalase, urease, Cu/Zn superoxide dismutase, etc.). It has been proved that the virulence of S-type bacteria is significantly higher than that of R-type bacteria, which is due to the lack of LPS of S-type bacteria in the cell wall of R-type bacteria. The bacteria can be transmitted through digestion and respiratory tract, but it is mainly infected by contact. It is generally believed that after Brucella invades the human body through the skin and mucous membranes, it mainly invades the local lymph nodes through the lymphatic vessels to grow and multiply and is swallowed by macrophages. The lymphatic barrier enters the blood circulation. In the blood circulation, Brucella continues to grow, multiply, die, and release endotoxins, causing bacteremia and toxemia. Endotoxin plays an important role in the occurrence of acute symptoms. 1 mg of endotoxin can raise the body temperature to 40.5°C and cause severe bacteremia and toxemia systemic symptoms. At this time, if the immune function of the human body is normal, the bacteria can be eliminated and healed by the combined action of T cells, macrophages and specific antibodies. If the specific immune function cannot eliminate the bacteria, especially the S-type bacteria, the bacteria can enter the organs and tissues with the blood, especially the macrophages, to form infection foci or migratory foci. The bacteria in the lesion can enter the blood circulation many times to form recurrence and various allergic manifestations, resulting in repeated illnesses and aggravation

. In the chronic phase, bacteria are mainly confined to various organs and tissues, causing damage to local organs and tissues. In addition, it is possible that the bacteria have been eliminated, but the allergy caused by the bacteria can also cause local lesions when the body is still present. Brucella is mainly parasitic in cells, and antibacterial drugs are not easy to enter and play a bactericidal effect. This may be one of the reasons why brucellosis is difficult to cure. The pathological changes of this disease are extremely extensive, and almost all organs and tissues can be invaded. Among them, mononuclear phagocyte system, bone joint system, nervous system, etc. are common and most common. Diffuse cell proliferation is common in the acute phase, and granulomas composed of epithelial cells, macrophages, plasma cells and lymphocytes may appear in the chronic phase. This granuloma is similar to the lesion of human sarcoidosis, non-caseous necrosis, which is a typical lesion of this disease. Others, such as the cardiovascular system, motor system, reproductive system, nervous system, etc., often have lesions of varying severity.

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