3种非猪瘟病毒单独或混合感染对猪瘟弱毒疫苗免疫效力的影响

将 2 0头 9月龄左右猪瘟、伪狂犬、猪繁殖与呼吸障碍综合征抗原、抗体阴性猪分成 6组 ,分别利用猪细小病毒(PPV)、猪伪狂犬病毒 (PRV)和猪繁殖与呼吸障碍综合征病毒 (PRRSV)单独或混合感染。 7d后连同对照猪 4头 ,免疫接种猪瘟兔化弱毒疫苗 (HCL V) ,13d后连同 4头阴性对照猪一起攻击猪瘟石门强毒。整个试验期间分别每天测温 ,观察临床症状 ,每周采集扁桃体和血样做各种病毒抗原及抗体检测。结果表明 ,非猪瘟病毒感染 7d后 ,所有各组猪均从体内检测到了相应感染的病原 ,表明 3种非猪瘟病毒感染成功。在攻击猪瘟石门强毒后 2周 ,感染了非猪瘟病毒后接种 HCL V疫苗的 4个免疫组 12头猪除 1头外 ,11头全为猪瘟病毒 (HCV)抗原检测阳性 ,且多呈强阳性 ;而单一 HCL V疫苗免疫组在猪瘟强毒攻击后检测不到 HCV;所有 HCL V疫苗免疫猪均存活 ,而非免疫对照组 4头猪全部在攻毒 16 d内死亡。     

Vaccination of Pigs Against Hog Cholera (Classical Swine Fever) With a Detergent Split Vaccine

Four pigs were inoculated subcutaneously with a detergent (triton X 100) split hog cholera virus in Freund’s incomplete adjuvant. Four other pigs were in the same way inoculated with a detergent split bovine viral diarrhoea virus, also in Freund’s incomplete adjuvant. In the experiment were used 3 control pigs. The vaccinations were repeated after 3 weeks. All pigs were challenged with highly virulent hog cholera virus (Tübingen) 12 weeks after primary inoculations. Signs of hog cholera were only noted in the control pigs.This introductory experiment was succeeded by a larger experiment with subcutaneous inoculations of: 10 pigs with detergent split hog cholera virus in Freund’s incomplete adjuvant, 10 pigs with detergent split hog cholera virus in a saponin (Quil A) solution, 10 pigs with detergent split bovine viral diarrhoea virus in Freund’s incomplete adjuvant, 10 pigs with detergent split bovine viral diarrhoea virus in the Quil A solution plus 5 control pigs. The vaccinations were repeated after 3 weeks, and finally all pigs were challenged 9 weeks later with the highly virulent hog cholera virus strain.With the exception of 1 animal which died accidentally, all animals survived in the groups inoculated with the Quil A vaccines and in the group inoculated with the detergent split hog cholera virus/oil adjuvant vaccine. In the group inoculated with the detergent split bovine viral diarrhoea virus/oil adjuvant vaccine, some of the pigs died of hog cholera.     

猪瘟病毒持续感染对母猪繁殖性能及仔猪猪瘟疫苗免疫效力的影响

利用来源于同一猪场的2头猪瘟病毒(HCV)持续感染的带毒母猪及所产35头仔猪(包括13头死胎)和6头阴性对照猪,观察母猪的胎儿发育成活状况、仔猪HCV带毒率及HCV垂直传播对仔猪猪瘟兔化弱毒疫苗(HCLV)免疫效力的干扰作用,同时进行水平传播试验和观察HCV持续感染对母猪繁殖功能的影响。结果表明：HCV持续感染对其中1头母猪的胎儿发育和成活有明显影响,而对另1头母猪的胎儿发育没有明显影响;HCV持续感染母猪可经过胎盘垂直传播病毒给仔猪,传播率达45％～86％;吃初乳和接种HCLV不能阻止带毒仔猪的死亡,9头带毒仔猪在45d内死亡4头;免疫HCLV不能使带毒仔猪产生免疫保护力。5头猪在强毒攻击后死亡4头;HCV垂直传播的带毒猪可发生水平传播,并引起3／4感染猪死亡;HCV持续感染可引起母猪生殖系统病理变化。导致繁殖障碍。     

Persistent hog cholera infection detected during virulence typing of 135 field isolates

During the hog cholera (HC) eradication program in the United States, 135 field isolates were characterized by inoculation into specific-pathogen-free pigs. This gave origin to the classification of 61 (45%) as high virulent, 37 (27%) as low virulent, 29 (22%) as avirulent or immunizing, and 8 (6%) as capable of causing persistent infection. The persistent infections caused by the eight isolates were of long durtion, lasting in one instance to 152 days. The persistently infected pigs remained relatively free of clinical signs of HC but had high concentrations of HC virus (HCV) in their blood. When 6 of these pigs were given a second inoculation (with the virulent Ames strain of HCV), 2 died while the health status of 4 remained unchanged.     

Comparative immunohistopathology in pigs infected with highly virulent or less virulent strains of hog cholera virus

Eight pigs were inoculated subcutaneously with a highly virulent hog cholera virus (HCV) strain ALD. The infected pigs developed severe illness and became moribund on postinoculation day (PID) 7 or PID 10. Histologic lesions were characterized by severe generalized vasculitis, necrosis of lymphocytes, and encephalitis. HCV antigen was detected in crypt tonsilar epithelial cells, macrophages, and reticular endothelial cells of lymphoid tissues. Antigen localization corresponded well with histologic lesions. Five pigs were inoculated with less virulent HCV Kanagawa/74 strain and were euthanatized on PID 30. All five infected pigs recovered from the illness but became stunted. They also had a slight follicular depletion of lymphocytes, histiocytic hyperplasia, and hematopoiesis in the spleen. Less virulent HCV antigen was observed in the tonsils, kidneys, pancreas, adrenal glands, and lungs. Although antigen localization was less associated with histologic lesions, immunoreactivity was stronger than that in the pigs infected with the ALD strain of HCV. An almost complete loss of B lymphocytes was recognized in pigs infected with the ALD strain and was correlated with follicular necrosis in lymphoid tissues. Loss of B lymphocytes was not prominent in the pigs infected with Kanagawa/74 strain. The number of CD4+ and CD8+ T lymphocytes was significantly higher than that in the noninfected control pigs.     

Is feeding of green silage in areas with hog cholera in wild boar a danger for domestic swine herds? Experimental study]

In an experimental study we tested the survival of hog cholera virus (HCV) contained in pieces of muscular tissue and organs from experimentally infected swine after incubation in silage. In big (diameter greater than 20 cm) muscular pieces HCV survived even in excellent mineral acid silage (pH 3.8-4.0) after a storage of 5 months. On the other hand in smaller parts (musculature tissue, organs less than 20 cm diameter) we never found virulent HCV after 3 months of incubation. Independent of the size of the tested organs we did not find any virulent HCV in silage with pH 5.2 after 3 months. The results of our investigations show, that the feeding of green silage in areas with hog cholera among wild boar is a potential risk for the domestic swine population. In conclusion we propose to feed green silage to unvaccinated pigs in such areas only after a storage of 9 month.     

Thermal inactivation of hog cholera virus in ham.

Experiments were conducted to determine the temperatures required to inactivate hog cholera virus (HCV) in fresh ham after 1 minute and in cured and processed (canned) ham after 90 minutes. A momentary or "flash" temperature of 71 C for 1 minute caused inactivation of the virus in 15 of 15 cubes (2 cm3) of ham. Hog cholera virus was destroyed in 21 of 21 canned hams (weighing 0.91 kg each) when an internal temperature of 65 C was sustained for 90 minutes. Pigs were found to be more sensitive than tissue culture cells for detecting viable HCV in heat-processed fresh hams. Virus was isolated by tissue culture technique only from those hams exposed to temperatures below 61 C. The relative concentration of HCV in unheated cured hams of experimentally infected pigs varied over a wide range; these pigs were inoculated with the virulent Ames strain and were killed on postinfection day 6 or 7.     

Characterization of porcine and some ruminant pestiviruses by cross-neutralization

Serologic relationships between 11 pestivirus strains that originated from pigs and five that originated from cattle or sheep were studied by cross-neutralization. Experiments were performed with pig and sheep sera raised against the strains. The results were analysed by a computerized taxonomic procedure. The 16 viruses were classified into four distinct serologic groups. All hog cholera virus (HCV) strains were classified in one group; the other three groups consisted of strains that can infect pigs, but that are identified as bovine viral diarrhoea virus (BVDV) or border disease virus (BDV), or showed a closer relationship to BVDV and BDV than to HCV.     

Development and properties of a cell culture produced vaccine for hog cholera based on the Chinese strain

The Chinese strain of hog cholera virus (HCV) was adapted to suspension cultures of the established swine kidney cell line SK6. The strain designated "Cedipest", is produced on the basis of a seedlot system. The masterseed virus was identified in vitro and in vivo, and was found free from extraneous pig pathogenic viruses by repeated animal inoculation followed by appropriate serological tests. A distinct and reproducible relationship was ascertained between infectivity in vitro and protection. Pigs inoculated with 400-600 TCID50 of the Cedipest strain proved fully protected against challenge with greater than 100 pig LD50 of a virulent strain of HCV at 7 days and at 6 month post vaccination.     

Coagulation changes in African swine fever virus infection

Pigs were infected with highly virulent (Tengani '62), with moderately virulent (DR '79) African swine fever (ASF) virus, or with virulent hog cholera (HC) virus. Changes in platelet counts, selected coagulation assays and concentrations of factor VIII-related antigen (VIIIR:Ag) were monitored. Permeability of aortic endothelium was studied after the injection of Evan's blue dye on various days after infection with DR '79 ASF virus. Virulent ASF virus caused prolongation of the activated partial thromboplastin time (APTT), 1-stage prothrombin time, and thrombin clotting time as early as postinoculation day (PID) 4. These changes became progressively more severe until death. Both virulent HC and DR'79 viruses induced an increase APPT and thrombin clotting time at PID 3 to 4, only occasionally did the prothrombin time increased significantly (P less than 0.01). The APPT began to decrease on PID 7 and 8, but only DR'79-infected pigs lived long enough to regain a normal APTT. Infection by ASF viruses caused acute thrombocytopenia after PID 6 and platelet counts of HC virus-infected pigs decreased progressively from the onset of fever to levels of 1 to 2 X 10(5)/mm3 at PID 6 to 7. All ASF virus-infected pigs had an increase in VIIIR:Ag beginning at PID 3, with maximum increases at PID 6 to 7. Hog cholera virus infection did not cause consistent changes in levels of VIIIR:Ag. Pigs infected with DR'79 virus did not have increased vascular permeability to Evan's blue dye during infection; however, there was markedly decreased staining of the aorta after pigs became thrombocytopenic.     

Tween 80: a marker for differentiation of hog cholera and bovine viral diarrhea viruses.

Markers for differentiating hog cholera and bovine viral diarrhea viruses were studied using Tween 80, chloroform, trichlorotrifluoroethane and tri (n-butyl) phosphate. Attenuated A and virulent Ames strains of hog cholera virus were employed. Moreover, the NADL PK-15 cell culture adopted strain and low cell culture passaged Purdue strain of bovine viral diarrhea virus were used. These viruses were reacted with 2,500 micrograms/ml of Tween 80 for one hour at 37 degrees C. When attenuated A and virulent Ames strains of hog cholera virus with titers greater than 10(6) and 10(5) plaque forming units respectively, were reacted with Tween 80 the titer of each strains was reduced by approximately 10(4) plaque forming units of virus. When either strain of bovine viral diarrhea virus was reacted with Tween 80, virus was not detected.     

猪瘟病毒低毒力毒株FJFQ株的分离鉴定

从福建某猪场分离到 1 株病毒,其在PK 15细胞上的毒价为 106.5 TCID50/mL,该病毒能被猪瘟病毒高免血清所中和(效价为1∶8)。通过 RT -PCR 扩增出猪瘟病毒约250 bp的E2蛋白主要抗原编码区序列,其与几株已发表毒株序列的核苷酸及氨基酸同源性分别为79.9%~87.9%,77.7%~86.6%,与Alfort 株同属于基因二群。经本动物传3代均不表现明显的临床症状。用猪瘟兔化弱毒疫苗免疫后以此分离毒作强攻进行免疫保护相关实验,结果免疫组猪在攻毒前及攻毒后扁桃体 HCFA检测均为阴性,对照组猪扁桃体HCFA于攻毒后1周开始出现阳性结果,且一直持续到试验结束。用分离株免疫本动物后再攻石门毒, 2 头试验猪中 1 头死亡,1头出现临床症状。初步说明,所分离的病毒为猪瘟病毒(命名为CSFV- FJFQ株),可能是一株低毒力毒株,且其免疫原性不好。     

The Effects of in utero Viral Infection on Embryonic, Fetal, and Neonatal Survival: A Comparison of SMEDI (Porcine Picorna) Viruses with Hog Cholera Vaccinal Virus

SMEDI and hog cholera viruses were shown to have marked effects upon the survival of the embryo (from conception to 30 days of gestation), the fetus (from 30 days of gestation until birth), and the neonatal pig (from birth until five days after birth). Embryonic infection was characterized by death and absorption of the embryo and in some instances the return to estrus after an irregular estrous cycle. Embryonic infection also may have been responsible for the development of some abnormal pigs. Fetal infection caused death with mummification of one or more fetuses and occasionally all fetuses in the uterus. Infection established in early gestation produced effects on the fetus which apparently persisted until after birth and varied from a persistent viremia (as in hog cholera infection) to an undefined lack of resistance in the newborn (as in SMEDI virus infection). Hog cholera vaccinal virus was the more virulent of the two virus types and reacted somewhat like rubella virus, in that infection apparently could be established in the fetus even in middle trimester of pregnancy, and possibly later. SMEDI viruses, in contrast, were less virulent and were most pathogenic when the dam was infected during the first 30 days of pregnancy. Immunity against either virus could be established in the nonpregnant gilt and was most effective in preventing intrauterine infections with that virus. However, with as many as 10 enteroviruses (five are known to cause intrauterine infection) it was believed that maintaining a closed breeding herd and introducing new stock into contact with the breeding herd at least 30 days before breeding time might be a safer means of control.     

A new approach for the diagnosis of hog cholera

Pestiviruses were isolated from seven cases of suspect hog cholera. Using peroxidase conjugates of monoclonal antibodies (Mabs) six isolates were identified as hog cholera viruses (HCV), while one isolate was of ruminant origin, possibly bovine viral diarrhea virus. In parallel attempts were made to develop an ELISA for the detection of HCV-specific antibodies in pig sera. The Mab HCTC26 coated to polystyrol plates efficiently captured the major viral glycoprotein gp53 from crude antigen suspensions prepared from infected cells. The immobilized gp53 served as diagnostic antigen. Five pigs experimentally infected with the HCV strain Glentorf were sequentially bled and the development of antibodies was monitored by neutralization tests and the ELISA. Results showed that both tests detected antibodies simultaneously after infection. Titres measured by ELISA were slightly higher than those registered by neutralization.     

重庆市甘规模化猪场猪瘟的诊断

重庆某猪场4头濒死仔猪病理变化疑以猪瘟，病科脾、淋巴结用兔体交互免疫试验检测也为猪瘟阳性。采用中国兽药监察所的猪瘟单抗纯化的强、弱毒抗原酶联免疫吸附试验（ELISA）对该场的母猪及仔猪进行了血清流行病学调查，9.69%（19/196）的母猪及16.83%（33/188）的仔猪血清中即为猪瘟强毒（野毒）抗体阳性，又为猪瘟兔化弱毒抗体阳性。试验结果显示，猪瘟是该场母猪繁殖障碍及仔猪死亡的原因之一。     

Effects of challenge with a virulent genotype II strain of porcine reproductive and respiratory syndrome virus on piglets vaccinated with an attenuated genotype I strain vaccine

Porcine reproductive and respiratory syndrome virus (PRRSV) is endemic in most parts of Asia, where genotype I and II strains of diverse virulence may coexist. This study evaluated the outcome of infection with a highly virulent Asian genotype II PRRSV isolate in piglets vaccinated with a genotype I vaccine. Twenty-one 3-week-old piglets were divided in three groups: Pigs in group V (n=8) were vaccinated with an attenuated genotype I commercial PRRSV vaccine, while pigs in group U (n=8) and a control group (group C; n=5) were unvaccinated; 6 weeks later, pigs in groups V and U were challenged intranasally with a highly virulent strain of genotype II PRRSV (1×10(5) 50% tissue culture infectious doses/mL), while pigs in group C received a placebo. Over a period of 21 days after challenge, vaccinated pigs had significantly lower mortality (0/8 versus 2/8), fewer days of fever, a lower frequency of catarrhal bronchopneumonia, higher weight gains (13.4 versus 6.6 kg) and lower levels of viraemia compared to unvaccinated challenged pigs. Immunisation with a genotype I attenuated PRRSV vaccine provided partial protection against challenge with a highly virulent genotype II strain.     

Transiency of the different cholesterolaemic responses to dietary cellulose and psyllium in pigs and two strains of hamsters

The time course of the cholesterolaemic effects of dietary cellulose and psyllium was studied in two strains of hamsters and in pigs. In the first experiment, the ShHan:AURA strain from Harlan was used. Hamsters were first fed a cholesterol‐enriched (0.1%, w/w) semipurified diet containing 3% cellulose for a period of 2 weeks. Then, one group (n = 14) continued on the cellulose diet and another group (n = 14) was transferred to the psyllium diet. After 1.5 weeks on the diets, the psyllium‐fed hamsters showed a steep decrease in plasma cholesterol levels whereas the cellulose group maintained high cholesterol levels. Then, however, the cellulose‐fed hamsters showed a gradual decrease in plasma cholesterol levels and after 9.5 weeks on the diets, they had plasma cholesterol levels comparable to the hamsters fed psyllium. In the second study, the Lake View strain from Charles River was used. Two groups of hamsters (n = 14 per group) were fed a cholesterol‐enriched (0.1%, w/w) semipurified diet containing either 3% cellulose or 3% psyllium. The psyllium‐fed group had significantly lower plasma cholesterol concentrations than the cellulose group after 2, 4, and 6 weeks on the diets. After 8 weeks on the diets, however, the cholesterol levels in the cellulose group had decreased to levels similar to those in the psyllium group. In the third experiment, pigs were fed a cholesterol‐enriched (0.5%, w/w) semipurified diet containing either 5% cellulose or psyllium. After 1 and 2 weeks on the diets, the cellulose‐fed pigs had elevated plasma cholesterol concentrations, whereas the psyllium‐fed pigs maintained low cholesterol levels. After 3 weeks on the diets, the cholesterol concentrations in the cellulose‐fed pigs had decreased to the same level as in the psyllium‐fed pigs. There was no significant effect of cellulose and psyllium on liver cholesterol in the three studies, but psyllium tended to increase the faecal excretion of bile acids. Thus, the present studies showed a cholesterol lowering effect of dietary psyllium compared with cellulose in hamsters and pigs, but this effect was transient.     

Influence of vaccination route on the efficacy of Aujeszky's disease deletion-mutant vaccine.

In order to compare the effect of the route of immunization on the efficacy of a modified live Aujeszky's disease (AD) vaccine, which had deletions in both thymidine kinase (TK-) and glycoprotein gIII genes (gpIII-), 20 six-week-old pigs were vaccinated by either the intramuscular (IM) (n = 10) or subcutaneous (SC) (n = 10) route. All the animals, including five non-vaccinated control animals, were challenged with virulent AD virus 22 days after vaccination. Four of five non-vaccinated animals died within 12 days after challenge. Although none of vaccinated animals died, three of animals in the SC group exhibited clinical signs, and average daily gains in the SC group were depressed. The animals in the IM group were not found to shed challenge virus, but those in the SC group shed the virus up to 9 days. Virus neutralizing antibody titers in the vaccinated animals were low or non-detectable by 21 days after vaccination. A glycoprotein gII (gpII) screening ELISA detected gpII antibody in all animals in the IM group. While, only 30% of animals in the SC group were positive by the same test. The results of this study indicate that TK-, gpIII modified live AD virus vaccine is effective against challenge with virulent AD virus; however, vaccination by the SC route reduced vaccine efficacy in comparison with IM route.     

Efficacy of a live attenuated vaccine in classical swine fever virus postnatally persistently infected pigs

Classical swine fever (CSF) causes major losses in pig farming, with various degrees of disease severity. Efficient live attenuated vaccines against classical swine fever virus (CSFV) are used routinely in endemic countries. However, despite intensive vaccination programs in these areas for more than 20 years, CSF has not been eradicated. Molecular epidemiology studies in these regions suggests that the virus circulating in the field has evolved under the positive selection pressure exerted by the immune response to the vaccine, leading to new attenuated viral variants. Recent work by our group demonstrated that a high proportion of persistently infected piglets can be generated by early postnatal infection with low and moderately virulent CSFV strains. Here, we studied the immune response to a hog cholera lapinised virus vaccine (HCLV), C-strain, in six-week-old persistently infected pigs following post-natal infection. CSFV-negative pigs were vaccinated as controls. The humoral and interferon gamma responses as well as the CSFV RNA loads were monitored for 21 days post-vaccination. No vaccine viral RNA was detected in the serum samples and tonsils from CSFV postnatally persistently infected pigs for 21 days post-vaccination. Furthermore, no E2-specific antibody response or neutralising antibody titres were shown in CSFV persistently infected vaccinated animals. Likewise, no of IFN-gamma producing cell response against CSFV or PHA was observed. To our knowledge, this is the first report demonstrating the absence of a response to vaccination in CSFV persistently infected pigs.     

Natural infection of pigs with bovine viral diarrhea virus and its differential diagnosis from hog cholera.

Natural infection of pigs with bovine viral diarrhea virus (BVDV) through contact with infected cattle has caused problems in diagnosing hog cholera (HC). Low cross-reacting serum antibody titers against HC caused by BVDV infection were found in clinically normal pigs as well as those suspected of having HC. Bovine viral diarrhea virus was isolated from specimen tissues and initially identified as HC virus (HCV), using the fluorescent antibody cell culture technique. Additional cell cultures, as well as pig and calf trials, were necessary to identify it as BVDV. The isolate caused clinical signs of illness in the calves, whereas the pigs remained healthy. Bovine viral diarrhea virus may be detected in tissue sections or isolated in cell cultures and confirmed as HCV, using the HC fluorescent antibody conjugate. Laboratories performing the neutralization test for HC should use discretion when interpreting HC titers unless BVD titers are determined on the same serums.