| Pseudorabies virus and porcine circovirus type 2 can infect a pig and result immune suppression. The more serious disease and major economic losses in swine are caused as for the mixed infection with PRV and PCV2. However the pathogenic mechanism of the mixed infection with PRV and PCV2 are unclear. Study of prevention and control of PRV and PCV2 can provide the theoretical support for purification of PRV in pig farms. In this study, four experiment goups were divided (the first group of pigs were only infected with PRV; the second group of pigs were only infected with PCV2; the third group of pigs were infected with PRV and PCV2 at the same time; and the fouth group of pigs were only infected nothing for control) to study the pathogenic mechanism of mixed infection of PRV and PCV2 with virus isolation methods, quantitative PCR, detection of physiological, biochemical index in blood and antibody of the infected pigs, then the technology of comprehensive prevention and control PR were designed and carried out in 72 pig farms in YunNan provice.1. Clinical pathology of piglets infected with PRV/PCV2 and PRV and PCV2PRV and PCV2 are important contagion in pigs. PRV can cause reproductive and respiratory disease of pigs, while PCV2 causes porcine postweaning multisystemic syndrome, reproductive problems, dermatitis and nephropathy syndrome and other diseases. To study the pathology of piglets infected with PRV/PCV2 and PRV and PCV2, the clinical symptoms and pathological changes of the infected pigs with indicated virus were observed. The results showed that the coinfected group with PRV/PCV2 displayed more serious pathological symptoms than one virus infected group with PRV or PCV2. The PRV infected group showed fever, nerve symptoms, itching and diarrhea. The PCV2 infected group showed fever, dyspnea, marasmus and anaemia.The coinfected group showed fever, marasmus, vomit, neurological failure and death. The results of microscopic observation indicated that the heart, liver, spleen, lung, kidney, lymph nodes of groin and cerebellum had obvious pathologic changes from day 3 to 35 days after infection. The clinical pathology of the coinfected groupa showed more serious lesion than those of the PRV or PCV2 infected groups, and the PRV infected group was also more serious lesion than that of PCV2 infected group. There were no any pathological changes in control group.2. Study on the dynamics of viral load in pigs infected with virusAt day 3,7,14,21 and 35 after infection, two pigs in each groups were randomly killed, and the heart, liver, spleen, lungs, kidneys and inguinal lymph nodes, cerebellum, blood, fecal swabs and nasal swabs of pigs were collected to detected the viral load by QPCR. The results showed that the viral load of the coinfected group were higher than those of the group only infeced with PRV or PCV2 infected group, and the viral load of PRV infected group was hgher than that of PCV2 infected group, he tissue of the highest viral load was lung, following inguinal lymph nodes, liver, spleen, kidneys, heart, and cerebellum. The viral load of the PRV infected group reached highest titer at day 7 after infection, and PCV2 group was day 14. The higher viral load it had, the worse clinical symptoms were. The viral load of the coinfection was highest and piglets had serious damage in organs and then died. The virus in blood, anal swabs, nasal swabs reached the highest level at 7-14d after coinfection and only infected PRV group, The viral of blood in the only infected PCV2 group was the highest, and appeared the earliest, while the viral load was lowest titer during the infected late stage.3. Study on the effection of the immunity inhibition in piglet with PRV and PCV2 coinfectionThe ELISA was applied to detect IL-4, IL-6, IL-10 and IFN-y level and antibody titer in blood of piglets infected with PRV or PCV2. The complements of C3 C4, IgG, red blood cells, hemoglobin, white blood cells, lymphocytes, neutrophils and platelets number was determined and analyzed. The statistical analysis showed that:the IL-4 level in mixed infection had little change compared to two single infection group in the first 0-3d, and did not play immune function in early days, but it present a rapid increased trend in 7-14d, and go beyond the 2 single infection group; IL-6 present a rapid decreased trend in the first 0-3d, less than single PRV infection, it can be seen that in the early stages of infection humoral and cellular immune response involved in inflammation from mixed infection piglets. The complement of C3 in mixed infection presented an increased trend in the first 0-3d, and reached a higher level than two single infection groups, but it decresed in 7-21d and reached a lower level compared to two single infection group; The complement of C4 presented an increased trend, but the level was significantly lower than those of the two single infection. The immunoglobulin of IgG in coinfection in 0-3d decreased and reached a lower level than that of control group, but higher than those of two single infection group, indicating the immune systems of coinfection group had been suppressed in the early infection. The red blood cells, hemoglobin, neutrophil numbers in mixed infection were higher than those of two single infection group; the white blood cells and lymphocytes were lower than those of two single infection. The results showed that the immune suppression caused by coinfection was more serious, and the loss of immune function caused the death of whole group.4 Study of PR technology in PRV and PCV2 mixed infectionYunnan PR appears at a high level in recent years, although the detection and purification of the disease have good effection to some extent, the PRV and PCV2 mixed infection caused swine again onset, and severe reproductive failure in swine, pigs respiratory symptoms emerged. To optimize PR prevention and control technology, the three PRV, PCV2 infection-positive pig farms were selected.The test of moderate size selection of, three kinds of purification scheme of PRV and PCV2 were designed based on the above studies:The piglets of A field was detected in the infeced antibody positive pigs with PRV and PCV2 and were inoculated with swine pseudorabies vaccine; The piglets of B field was detected in the infeced antibody positive pigs with PRV and were inoculated with PRV gene deletion vaccine; The piglets of C field was detected in the infeced antibody positive pigs with PRV and PCV2 and were inoculated with PRV and PCV gene deletion vaccine; Meanwhile, the purification performance of three methods were analyzed. The results showed that three purification methods could control swine pseudorabies, C field purify two kinds of viruses, and two kinds of vaccine inoculation showed the best circumstances purifying effect. On this basis, a pseudorabies purification technical procedure were developed in this study, and carried out in 72 scale pig farms and a demonstration country in Yunnan Province from 2012 to 2015, and detected 7516 samples infection antibodies and 8696 samples immune antibodies by ELISA. The results showed that:the infection rates of wild PRV were 24.42%,5.47%,2.78%,2.69% in 2012,2013,2014,2015, resectively; wherein the infection rates in boars were 18.25%,12.36%,8.33%,3.15%, resectively; The infection rates in sows were 24.73%,4.80%,2.48%,2.65%, resectively; immune antibody positive rates in pigs were 69.03%,81.86%,85.99%,86.40%, resectively, the wild virus infection rate were 0% in 14 pig farms. The results showed that, after 4 years of purification, infection rate of swine pseudorabies virus present a gradually decreasing trend, immunization antibody positive rate increased year by year, indicating that pseudorabies purification technology and operating procedures have utility in most parts of Yunnan Province and can be widely applied. |
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