Experimental Study Of Bama Miniature Pig Infected By Classical Swine Fever Virus

Bama miniature pig is same with domestic pigs in the taxonomy, belonging to the Mammaliaclass, Artiodactyla, Suidae, pig genus. Bama miniature pig is small, easy to operate. What is moreimportant is that its hereditary is stable. It is more suitable to be the experimental animal model.Classical swine fever （CSF） is an acute, infectious disease caused by classical swine fever virus（CSFV）. Its morbidity and mortality rate nearly achieve10⁰%.CSF is the major infectious disease.Every county all takes strict precautions against it. CSF is also one of the A category infectiousdisease included in OIE. Currently, larger domestic pigs are only animals widely used in vaccineevaluation and pathogencity study of classical swine fever virus （CSFV）. But domestic pigs arelarger in body size, and it is not easy to control in genetics. Besides, domestic pigs mignt carry awide variety of pathogens. In recent years classical swine fever virus is complicated in our country,piglets always carry maternal antibodies. All of this leads to the poor results in repeatability.Therefore, looking for the animal infection model of classical swine fever virus will providequalified experimental animal for swine fever research and its vaccine evaluation.This test artificially inoculated bama miniature pigs with standard virulent Shimen strain ofclassical swine fever virus. Through clinical symptom observation, temperature monitoring,histopathologic analysis, detection of virus replication, lymphocyte proliferation analysis andrecording of T lymphocyte subsets change in peripheral blood, we evaluated sensitivity of Bamaminiature pigs against CSFV. At2DPI-3DPI, all infected groups showed clinical signs, includingfever, sleepiness, loss of appetite, stiff gait, conjunctival flushing, fecal disappear, diarrhea. Thehighest temperature could reach40.76°C. Clinical scoring criteria in6DPI infection of classicalswine fever virus infection group reached the typical virulent state. Now the clinical score is morethan6points. Blood viral load determined by RT-PCR, virus existed in all groups besides thecontrol group in3DPI. At this time the blood viral load is10³.8copies/μL. The blood viral loadreached the highest point in14DPI,10⁶.3copies/μL. Virus in the tissues was determined, lymphnode, spleen, tonsils and lung tissues were generally higher than other tissues, respectively10⁶.73,10⁶.16,10⁶.57,10⁶.50copies/μL. In proliferation experiment, stimulating with the same dose of con A,the proliferation of peripheral blood lymphocyte of Bama miniature pig of infection group wasreduced by different degrees. The lowest stimulation index was0.25, but the control group was1.51; Results of T lymphocyte subsets analysis showed that as early as3DPI all infected groupsgreatly reduced. In3DPI CD4⁺T lymphocytes reduced to1/10^of original number, CD3⁺and CD8⁺T lymphocytes were reduced to1/4of original number. Eye view of pathological change showedthat all infected group showed typical pathological changes, such as pinpoint haemorrhaging in thekidney, hemorrhage of lymph nodes and tonsil, necrosis in the tonsils, splenic infarcts,hemorrhage of pulmonary and bladder endometriosis. Histopathological changes showed that lymph nodes and spleen of group A/B/C were all hyperemia in different levels; lymphocytes werenecrosis; liver and kidney were bleeding and always saw perivascular leukocyte aggregationcaused by inflammatory lymphocytes infiltration.Using different infectious dose groups and infection cohabitation group, this experimentfound that miniature pig infected with104-106TCID50classical swine fever virus may have typicalclinical symptoms, body temperature, pathological changes and immune cell changes. We ensuredthat Bama miniature pig is more susceptible than ordinary domestic pigs on classical swine fevervirus. This experiment constructed Bama miniature pig animal model infected by classical swinefever virus. This provided an ideal experimental animal for pathogenic mechanism, vaccineevaluation and preventing research of classical swine fever virus.