Ultrasonography of the reproductive tract and early pregnancy in red deer

Thirty-five farmed red deer hinds two years of age or older were observed during mating in April and May and the dates of oestrus and, or, matings were recorded. From immediately before the breeding season and at approximately weekly intervals from the start of mating until all deer were 42 days pregnant, rectal ultrasonographic scans were taken using a 5 MHz linear transducer while deer were held standing in a restraining device. Scans were recorded on video. The vagina and cervix were visible with the lumen appearing as a continuous or intermittent white line, respectively. The non-pregnant uterus was observed in most cases and was immediately anterior to the bladder. Structures resembling ovaries were seen only occasionally. By seven days gestation a 5 mm vesicle could be observed in a few deer, and by day 14, oedema of uterine horns was apparent in some cases. A comma-shaped fetal mass 6 mm long, fetal membranes and placentomes could be observed on day 24. The heart beat was observed on day 28 when the fetus was 10 mm long. Limb buds were observed on day 31 and by day 37 the head with nose and eyes was distinguishable. Fetal movements were first observed on day 42. The accuracy of pregnancy detection before day 20 was 35 per cent, between 21 and 30 days gestation 71 per cent and from 31 to 42 days 98 per cent.     

Pathologic changes in ferrets exposed to pseudorabies virus.

Ferrets experimentally infected by various routes with pseudorabies virus were examined for gross and microscopic lesions. Nonsuppurative meningoencephalomyelitis, as well as visceral lesions, occurred. The incubation period seemed related to the viral dose and to the distance between the inoculation site and the central nervous system. The distribution of the lesions in the central nervous system appeared to be closely related to the peripheral nerve pathways from the inoculation sites. Other findings indicated that the lymphohematogenous route could have a role in the dissemination of the virus in infected ferrets.     

膜分离法纯化浓缩猪伪狂犬病疫苗毒的效果

本研究使用不同孔径的陶瓷(有机)膜过滤器,对不合格的猪伪狂犬病毒细胞收获液(病毒含量≤104TCID50/mL)滤除杂蛋白、超滤浓缩、除菌处理得到纯化浓缩的猪伪狂犬病疫苗病毒液;然后对纯化浓缩的猪伪狂犬病疫苗病毒液分别进行杂蛋白去除率检验与无菌检验、病毒含量测定、安全检验、效力检验;将检验合格的纯化浓缩的猪伪狂犬病疫苗病毒液添加保护剂冻干,并对纯化浓缩的猪伪狂犬病冻干活疫苗进行以上各项检验,以及进行免疫猪体内抗体消长变化的检测。结果表明:纯化的猪伪狂犬病疫苗杂蛋白去除率平均达到68.3%以上,病毒含量≥105TCID50/mL,效力检验合格;免疫猪体内抗猪伪狂犬病毒抗体增长幅度比同时期未纯化的常规疫苗显著,其中免疫至84 d时中和抗体效价平均高达40.35稀释倍数左右,比常规疫苗中和抗体效价平均高出14.22稀释倍数。此项研究为畜禽疫苗的纯化提供一定的参考。     

Characterization of effects of zearalenone in swine during early pregnancy

Mature gilts (n = 16) were hand mated and randomly assigned to 1 of 4 groups of 4 gilts each. Treated gilts had 108 mg of purified zearalenone added to their diet on postmating days (PMD) 2 to 6, 7 to 10, or 11 to 15. Control gilts were given the same diet without added zearalenone. On PMD 6, 10, and 15, control gilts had venous cannulas placed in the jugular vein, and blood samples were taken at 20-minute intervals for 4 hours before feeding and 4 hours after feeding. Samples were collected from treated gilts on the last day that zearalenone was consumed. Samples were analyzed for follicle stimulating hormone, luteinizing hormone (LH), and prolactin. Single blood samples were taken by venipuncture on PMD 8, 12, 16, 20, 24, and 28 and at euthanasia and were analyzed for serum concentration of progesterone and estradiol-17 beta. All gilts were euthanatized 30 to 32 days after mating, and fetal development was assessed. Three gilts that were given zearalenone on PMD 7 to 10 were not pregnant and had regressing corpora lutea on the ovaries at euthanasia. All other treated and control gilts were pregnant. Serum samples from treated gilts on PMD 10 and 15 had lower mean prolactin concentrations than did those from controls. The number of LH spikes were fewer (P less than 0.05) in gilts that were given zearalenone on PMD 15 compared with those in controls on PMD 15. Serum progesterone concentrations indicated that corpora lutea regressed between PMD 20 and 28 in nonpregnant gilts.(ABSTRACT TRUNCATED AT 250 WORDS)     

猪伪狂犬病病毒的分离与鉴定

猪伪狂犬病是由疱疹病毒科的猪疱疹病毒1型病毒引起的一种急性传染病，多数动物均可感染，猪是本病的主要宿主和带毒者。本病主要以成年妊娠母猪流产、死产、木乃伊胎、新生仔猪急性死亡及3周龄以内的仔猪表现神经症状为主要特征。近年来我国也相继有本病发生的报道。1997年10月黑龙江省牡丹江地区某养猪场从外地引进种母猪，回来后直接放入后备猪舍与其他后备母猪混养，5日后同舍母猪出现厌食、发热、精神沉郁，有的呕吐、咳嗽。     

Latent infection and subsequent reactivation of pseudorabies virus in swine exposed to pseudorabies virus while nursing immune dams

The ability of pseudorabies virus (PRV) to infect and establish latency in pigs with passively acquired (maternal) antibody for PRV was tested by exposing such pigs to the virus and subsequently attempting to reactivate latent virus by administering large doses of dexamethasone. Pigs of each of 4 litters that had nursed gilts with relatively high (512, gilts 1 and 2), moderate (32, gilt 3), and no (less than 2, gilt 4) serum titers of virus-neutralizing (VN) antibodies for PRV were allotted to 3 treatment groups (A, B, C) when they were 2 weeks old. Group-A pigs were separated from littermates and dam and thereafter kept in isolation; group-B pigs were experimentally exposed oronasally to PRV and 1 hour later returned to their dam; group-C pigs were kept with their dam and potentially exposed to PRV by contact with littermates of group B. Sera obtained from pigs at selected intervals until they were 17 weeks old were tested for VN activity and for precipitating activity for radiolabeled viral proteins. All group-A pigs remained clinically normal throughout the experiment. Depending on the initial amount of passively acquired antibody, little or no serum VN or precipitating activity remained by the time these pigs were 17 weeks old. Group-B and -C pigs, with relatively high amounts of passively acquired antibody when exposed to PRV, also remained clinically normal. However, most became latently infected as subsequently evidenced by either dexamethasone-induced or noninduced virus reactivation. Noninduced reactivation may have been initiated by weaning the pigs when they were about 8 weeks old.(ABSTRACT TRUNCATED AT 250 WORDS)     

Shedding patterns in swine of virulent and attenuated pseudorabies virus

Shedding patterns of 2 virulent (P-2208 and KC-152-D) and 1 attenuated (BUK) strains of pseudorabies virus (PRV) were determined in groups of intranasally inoculated feeder pigs. Clinical signs observed following inoculation with the P-2208 and KC-152-D strains included increase in rectal temperatures up to 42.2 C, anorexia, severe respiratory disturbance, and fatal CNS signs in 2 cases. Clinical signs in pigs inoculated with 7.2 X 10(7) median tissue culture infective dose (TCID50) of the BUK strain were limited to depression and a rise in rectal temperatures to 40.5 C for 3 to 4 days. Evaluation of the efficacy of the virus isolation method used showed that the presence on swabs of only 12.5 TCID50 of the P-2208 strain or 8.4 TCID50 of the BUK strain resulted in a 50% chance of virus recovery. Intranasal inoculations with 500 TCID50 of the P-2208 or KC-152-D strain did not result in synchronous infection of the whole group. Intranasal inoculations with 5,000 TCID50 of the KC-152-D strain or 50,000 TCID50 of the P-2208 strain resulted in continuous virus shedding in all pigs between postinoculation days (PID) 4 and 13 (KC-152-D strain) or 14 (P-2208 strain). Some of the pigs in these 2 groups further shed the P-2208 or KC-152-D strain in a continuous or discontinuous pattern up to PID 19 (P-2208 strain) or 20 (KC-152-D strain). The time of onset or the level of virus neutralizing antibody production in individual pigs was not found to have an influence on their shedding patterns.(ABSTRACT TRUNCATED AT 250 WORDS)     

Detection of latent pseudorabies virus in swine using in situ hybridization

We have examined methods for detection of pseudorabies virus (PRV) latency in three groups of swine; naturally infected animals obtained from a field case; animals which have been experimentally infected with Becker or Iowa strains of PRV; and single reactors (single seropositive animals within PRV-free herds). In situ hybridization was shown to be more sensitive than explanation/co-cultivation for the detection of latent virus. Nervous tissues, in particular the trigeminal ganglia, were found to be the most reliable source for detecting latent PRV. The presence of latent PRV was not detected in lymphoid tissues examined.     

Sperm distribution in the reproductive tract of sows after intrauterine insemination

The purpose of the present study was to compare the number of spermatozoa obtained from different parts of the oviducts and the uterine horns of sows after intrauterine insemination (IUI) and conventional artificial insemination (AI), 24 h after insemination. Twelve crossbred (Landrace x Yorkshire) multiparous sows were used in the experiment. The sows were examined for standing oestrus using a back pressure test and were examined every 4 h after standing oestrus by real-time B-mode ultrasonography to estimate the time of ovulation. The sows were allocated to two groups, group I sows (n = 6) were inseminated by a conventional AI technique with 3 x 10(9) motile spermatozoa in 100 ml of extended semen, and group II sows (n = 6) were inseminated by an IUI technique using 1 x 10(9) motile spermatozoa in 50 ml of extended semen. A single dose of AI or IUI was given using the same boar, 8-10 h before the expected time of ovulation during the second oestrus after weaning. Twenty four hours after insemination, the sows were ovario-hysterectomized. The oviducts and the uterine horns were removed and divided into seven parts, the cranial, middle and caudal uterine horns, the utero-tubal junction (UTJ), the cranial and caudal isthmus, and the ampulla. All parts of the reproductive tract were flushed and the spermatozoa were counted using a haemocytometer. The results revealed that the spermatozoa were found in both the oviducts and the uterine horns in all animals. The number of flushed spermatozoa in the UTJ of groups I and II, was 142,500 and 131,167 (p > 0.05), and in the caudal isthmus was 1411 and 1280 (p > 0.05), respectively. The proportion of spermatozoa in different parts of the reproductive tract in relation to the total number of spermatozoa within the tract was not significantly different between groups I and II (p > 0.05). It could be concluded that IUI, with a three-time reduction in the number of spermatozoa used resulted in the same number of spermatozoa to be deposited in the sperm reservoir around ovulation time.     

Spread of pseudorabies virus among breeding swine in quarantined herds.

In theory, pseudorabies virus (PRV) may be eliminated from any size of breeding herd by phased test and removal if replacement gilts are not infected with PRV, culling decisions are partially based on PRV status, and the cull rate is higher than the incidence rate of PRV. Annual cull rates are commonly at least 50%, but little information exists on the incidence of PRV within enzootically infected swine herds. The purpose of this study was to develop a method by which spread of PRV could be detected among breeding swine within enzootically infected herds and to determine the incidence of PRV infection in these herds. Data were collected from 17 herds that were quarantined for PRV and ranged in size from 120 to 1,100 sows. At each herd, within the first 5 days of introduction, a group of approximately 30 replacement gilts was identified, vaccinated with a glycoprotein X-deleted PRV vaccine, and blood sample was collected. The owner of 1 herd had a nonvaccinated breeding herd and elected to leave incoming gilts nonvaccinated. After vaccination, blood samples were collected every 1 to 2 months for an average of 13.6 months. Serum samples from vaccinated gilts were tested for antiglycoprotein X antibodies by a specific differential ELISA. Samples from nonvaccinated gilts were evaluated by serum neutralization test. Product-limit method was used to estimate the probability of not becoming infected with PRV. Spread was detected in 7 of 8 herds that had more than 400 sows and in 2 of 9 herds that had less than 400 sows.(ABSTRACT TRUNCATED AT 250 WORDS)     

A skin test for pseudorabies virus infection in swine.

Heat-inactivated pseudorabies virus caused cutaneous delayed-type hypersensitive reactions when injected intradermally on the dorsolateral aspect of the thorax and tips of the ears of pigs previously exposed to the homologous virus. The reaction induced by subcutaneous injection in the lower eyelid was more easily administered and evaluated. Nonexposed control pigs did not react to the antigen and exposed and control pigs did not react when injected with a cell control antigen prepared in a similar manner. A positive response was detectable as early as seven days after exposure, reached near maximal levels by 28 days, and remained at similar levels for at least 90 days.     

Factors associated with circulation of pseudorabies virus within swine herds

Data were collected from 104 Minnesota swine farms quarantined for pseudorabies virus (PRV) infection. Each herd was serologically evaluated for the presence of antibodies to PRV in finishing pigs. Herd management practices, swine housing design, and disease profiles were described for each farm. Multiple logistic regression analysis was used to determine which factors were associated with circulation of PRV in the finishing pigs of farrow-to-finish farms. Sixty-seven (64%) of the herds had no serologic evidence of PRV circulation in the finishing section, whereas 37 herds (36%) contained at least one PRV seropositive finishing pig. The odds of a given finishing herd being seropositive for PRV were 2.85 times higher if the finishing pigs were housed in confinement (P = 0.01), 2 times higher if Actinobacillus (Haemophilus) pleuropneumoniae was a clinical problem in the herd (P = 0.03), 1.36 times less for each year that passed since the herd quarantine was issued (P = 0.01), 1.74 times higher if clinical signs of PRV were reported (P = 0.04), and 1.52 times higher if animal protein was included in at least one of the rations (P = 0.08).     

Vaccination of swine with thymidine kinase-deficient mutants of pseudorabies virus

A mutant of pseudorabies virus (PRV) deficient in thymidine kinase (TK-) activity was isolated and characterized. The mutant grew well in cell culture and did not revert to the thymidine kinase-positive phenotype. The PRV-TK- was not virulent when inoculated intranasally into 3-to 4-week-old pigs and could not be reactivated from the ganglia of these pigs by explantation and cocultivation with susceptible cells several weeks after virus inoculation. Pigs that had been exposed to PRV-TK- were immune to challenge exposure with a virulent strain of PRV. Furthermore, the challenge virus was not recovered from the ganglia of most of these pigs, indicating that colonization of the ganglia by a super-infecting virulent PRV strain was considerably reduced by vaccination.     

Study of the potential involvement of pseudorabies virus in swine respiratory disease.

In order to investigate the potential involvement of pseudorabies virus (PRV) in swine respiratory disease, nine week old pigs were intranasally inoculated with the PRV strain 4892. Two doses of infection were used: 10(4.5) median tissue culture infectious doses (TCID50)/pig and 10(3.5) TCID50/pig, with ten pigs per group. In the group of pigs inoculated with 10(4.5) TCID50, seven out of ten pigs died within six days after inoculation. The mortality rate in the group of pigs inoculated with the lower dose was only two out of ten and, there were several pigs in this group that showed signs of respiratory distress besides some mild nervous signs. Pseudorabies virus was isolated from various tissues collected postmortem, including alveolar macrophages. Virus localization in tissues was also detected by in situ hybridization. The histopathological examination of the respiratory tract tissues revealed a pathological process that was progressing from mild pneumonia to severe suppurative bronchopneumonia. The isolation of virus from alveolar macrophages provides support to the hypothesis that replication of PRV during the course of infection produces an impairment of the defense mechanisms in the respiratory tract.     

猪伪狂犬病病毒的分离鉴定与防制

从福清海口某猪场病猪淋巴结分离到1株病毒。该病毒接种Balb/c小鼠出现神经症状,死亡率为100%;接种Vero细胞出现拉网病变;PRV阳性血清能特异性中和该分离毒。以上结果证实该病毒为猪伪狂犬病毒。确诊后采取隔离、消毒及注射疫苗等措施,取得了一定的效果。     

Factors affecting the risk of infection with pseudorabies virus in Illinois swine herds

A case-control study of pseudorabies virus (PRV) infection in Illinois swine herds was conducted to identity risk factors associated with PRV infection. Factors identified as being associated with increased risk of PRV infection included percentage of herd in total confinement (adjusted OR (aOR)=19.7, 95% confidence interval (CI): 3.3–117.2) and having two or more PRV positive herds in the township (aOR=3.2, 95% CI: 1.0–10.2). A protective factor identified in the study included using one's own vehicle to transport pigs to market rather than hiring truckers (aOR=0.2, 95% CI: 0.07–0.6). A protective factor for producers who used their own vehicle for transporting pigs was cleaning the truck after off-site trips (aOR=0.09, 95% CI: 0.03–0.2). Management factors which can be most easily altered by producers who wish to prevent PRV infection in their herd include purchasing one's own vehicle for transport of pigs, and cleaning out this vehicle carefully after off-site visits. Total confinement herds and herds in areas where PRV is endemic appear to be at higher risk of becoming infected with PRV, and managers should be especially aware of herd security measures.