Epidemiological Investigation Of Jiangsu Province And Prophylactic And Treatment Of PMWS

Porcine circovirus (PCV) is one kind of smallest viruses we have known by now, which has two gene types, PCV1 and PCV2. PCV1 can be detected in most PK15 cells and it doesn't cause cytopathic effect (CPE). PCV2 has been implicated as the etiological agent of some diseases such as post weaning multisystemic wasting syndrome (PMWS), porcine dermatitis nephropathy syndrome (PDNS), reproductive failure and porcine respiratory disease complex (PRDC) etc. The wide spread of these diseases imposed serious threats on pig industry and caused huge loss in many nations and regions in the world, what is the worse is that the infection of PCV2 can depress the pig's immune system and lead to the second infection of other pathogens.Porcine circovirus type 2 (PCV2) has been identified as a necessary component of PMWS. While infection with PCV2 does not consistently induce PMWS, coinfection with other viral pathogens like porcine parvovirus or porcine reproductive and respiratory syndrome virus, or immune stimulation by vaccination has been used to induce disease in experiment and is very likely a phenomenon in the field. Typically, morbidity rates canreach 5% to 30% in affected herds, and the mortality among the piglets varies between 20% and 100%.186 tissue samples(spleen;lung;lymph node), which were collected from 15 different pig farms in 9 prefectures of Jiangsu Region from January 2006 to May 2007, were detected for porcine circovirus type 2(PCV2)by PCR.The results were as follows. 9 prefectures were positive for PCV2. Average PCV2 positive rates of samples and pig farms were 63.44%(118/186) and 100%(15/15), The results showed that the infection of PCV 2 existed widely in swine farms of Jiangsu province.The prophylactic effect of farm self-developed tissue inactive vaccine against PMWS was evaluated in the present trial for there is no commercial vaccine available. Twenty sows in the trial group were inoculated with the tissue inactive vaccine 20 days before parturition. The piglets of the immunized group and control group were under the same produce practices and medication besides two times vaccine inoculation in 21 and 42 days age respectively. The information of morbidity and mortality because of expression of PMWS and production parameters of piglets in both groups were collected and analyzed. As a result, the level of maternal PCV-2 specific antibodies of the piglets is higher than that of the control group. The morbidity rate and mortality rate of the 255 piglets in the control group during growth period was 23.14% and 9.41%, while it was 11.53% and 6.04% the inactive vaccine immunized group respectively. The average daily body weight gain during growth period of piglets of control group and immunized group were 435g and 497g respectively. The result the present trial indicates that farm self-developed tissue inactive vaccine acts positive in the prevention of expression of PMWS. It is important to emphasized that usable of self-developed tissue inactive vaccine is strict limited to pigs inside the farm itself, because the diseases may vary among different farms and the potential bio-safety problems of the self-developed vaccine.The effect of Serum containing good levels of porcine circovirus type 2 (PCV-2) antibodies on the prevention and treatment of PMWS were tested in the present trial. Serum contain good levels of PCV-2 antibodies was made by multi-inoculated finishing pigs with farm self-developed tissue inactive vaccine and commercial vaccines such as parvovirus vaccine and porcine reproductive and respiratory syndrome vaccine. In the prevention test, piglets in the treated group were injected high-immunized serum three times at 21,35 and 49 days of age and the dosage was 5ml,8ml and 10ml respectively. The piglets of the treated group and control group were under the same produce practices and medication. By the end of growth period, the morbidity rate and mortality rate of the piglets in the control group during growth period was 24.61% and 10.99%, while it was respectively 12.64% and 6.60% in the treated group. In the treatment test, thirty-one piglets with the expression of PMWS were divided into two groups; the piglets in the control group were administrated with antibiotics while piglets in the treated group were administrated with antibiotics and high-immunized serum. As a result, the morbidity rate of the control is 36.17% while it is 30.43% of the treated group. So usage of serum contain good levels of PCV-2 antibodies may be of good value in preventing clinical expression of PMWS, but in the treatment of affected piglets the effect may be not so distinct.