A current assessment of the role of porcine parvovirus as a cause of fetal porcine death.

One hundred one litters containing 1 or more dead porcine fetuses were collected at an Iowa abattoir during a 2-month interval and examined for evidence of viral infection. Each of 1,137 fetuses (302 dead, 835 alive) of these litters was tested for porcine parvovirus (PPV) antigens by direct immunofluorescence microscopy (FA) of fetal lung. Antigens of PPV were detected in the lungs of most of the fetuses of 11 of the litters. The 11 FA-positive litters contained 105 dead (100 FA-positive) and 14 live (12 FA-positive) fetuses. Infectious PPV was isolated from 10 of the 11 FA-positive litters and from 3 of the 90 FA-negative litters. No cytopathogenic agents other than PPV were isolated from any of the litters. Eleven of 101 (11%) litters examined and 100 of 302 (33%) dead fetuses examined were FA positive for viral antigen, indicating that PPV remains as a major cause of porcine fetal death.     

Efficacy of an inactivated virus vaccine for prevention of porcine parvovirus-induced reproductive failure.

Gilts vaccinated IM either once (4 gilts) or twice (2 gilts) with an acetylethyleneimine-inactivated porcine parvovirus (PPV) vaccine before they were bred were subsequently exposed intranasally and orally to virulent PPV at about the 40th day of gestation (from 37 to 43 days). At 2 weeks after vaccination, all had hemagglutination-inhibiting (HI) titers for PPV (from 20 to 80) which decreased by the time the immunity was challenged with virulent virus (from 10 to 40), but increased thereafter (from 160 to 1,280). Titers of singly and doubly vaccinated gilts were similar throughout the experiment. The gilts were killed at about the 84th day of gestation (from 80 to 87 days), and their litters were examined. Litters were comprised of 68 live fetuses and 1 dead fetus (7 to 14 fetuses/litter). Neither viral antigen, PPV, nor homologous HI antibody was found in any of the fetuses. In addition, 4 gilts were kept in contact with the vaccinated gilts and were treated similarly except for vaccination. These 4 gilts remained free of HI antibody until after they were exposed to virulent PPV during gestation. At the time the gilts were killed the titers were 1,280 to 2,560. Their litters were comprised of 11 live fetuses and 26 dead fetuses (8 to 11 fetuses/litter). Virus was isolated from fetuses of all litters. Viral antigen was found in 24 of the dead fetuses and 10 of the live fetuses. All infected live fetuses also had HI antibody for PPV. The 2 boars used to breed vaccinated and nonvaccinated gilts (usually each gilt was bred to each of the 2 boars), but not exposed to virulent PPV, remained free of HI antibody for PPV.     

An inactivated, oil-emulsion vaccine for the prevention of porcine parvovirus-induced reproductive failure

Pig fetuses inoculated at 45 days gestation with virulent porcine parvovirus (PPV) were harvested 10 days later. Virus was extracted, inactivated with binary ethylenimine and the antigen suspension emulsified with mineral oil adjuvant. One dose of this vaccine, or two doses with a 14 day interval, stimulated high and long lasting serum antibody titres in gilts. Vaccination caused no clinical reactions and lesions at injection sites were minor. Vaccination of seronegative gilts at 40 days gestation caused no adverse effects on fetuses. Six gilts which had been vaccinated five to nine weeks before mating were challenged intravenously with live, virulent PPV at 40 days gestation. At 98 days gestation 78 out of 84 (93 per cent) fetuses were alive and normal and no evidence of PPV infection was found in the six dead (mummified) fetuses. In four unvaccinated gilts similarly challenged with PPV at 40 days gestation only five out of 51 (10 per cent) fetuses survived to 98 days gestation and the virus was detected in 41 of the 46 dead (mummified) fetuses. This vaccine appears to be safe and effective for prevention of PPV-induced fetal loss in gilts.     

Vaccination Against Porcine Parvovirus Infection

Of 13 gilts 7 were vaccinated twice at an interval of 3 weeks with an inactivated vaccine against porcine parvovirus (PPV) infection, while the 6 nonvaccinated gilts served as controls. Starting after the 1st vaccination the gilts were bred and, after about 40 days of gestation, challenged intravenously with virulent PPV. The vaccinated gilts produced an antibody respons after the 1st and 2nd vaccination compatible with a primary and a secondary immune response, respectively. The nonvaccinated gilts remained low-titered or PPV antibody negative until after challenge. The gilts were killed after about 90 days of gestation, and their litters were examined. All of 53 fetuses from the vaccinated gilts were alive, and infection with PPV could not be demonstrated. Conversely, 50 of 65 fetuses from the non-vaccinated gilts were infected with PPV, and 43 were dead.In a field study comprising 2 herds, PPV seronegative or lowtitered gilts were vaccinated before mating. There were no obvious signs of reproductive disorders in the 2 herds during the vaccination trials, and the reproductive performance of vaccinated gilts did not differ significantly from that of non-vaccinated gilts.     

甘肃省四种母猪繁殖障碍性疫病抗体血清学检测

运用乳胶凝集试验(LAT)和ELISA方法对酒泉、张掖、金昌、武威、兰州、临夏、白银、定西、天水和平凉10个市州38个规模化和农村个体养猪场送检的619份血样和血清进行了PPV、PR、PRRS和JE免疫抗体检测,3年度平均阳性率PPV为80.83%、PR为60.70%、PRRS为43.39%、JE为47.57%,免疫抗体平均阳性率以PPV最高,PRRS和JE免疫抗体平均阳性率偏低。对8市州24个猪场采送的132份血清进行的PPV、PR、PRRS和JE感染抗体检测表明,PPV感染抗体平均阳性率为18.57%、PR感染抗体平均阳性率为15.28%、PRRS感染抗体平均阳性率为23.28%J、E感染抗体平均阳性率为24.14%。     

Pathogenicity of a skin isolate of porcine parvovirus in swine fetuses

The pathogenic properties of a skin isolate of porcine parvovirus (PPV), designated Kresse isolate, were compared with NADL-8 isolate, a prototype isolate of PPV, by in utero inoculation of mid-term and late-term gestation swine fetuses. Fetuses from pregnant sows of mid-gestation were inoculated with either NADL-8 or Kresse virus. Both isolates were highly pathogenic to mid-gestation fetuses. In contrast, dramatic differences in pathogenicity between these 2 isolates were observed in fetuses inoculated late in gestation. Such fetuses from each of 4 sows were inoculated with NADL-8 or Kresse virus isolate and sacrificed at 10, 18, 21, or 23 days postinoculation (PI). NADL-8-inoculated fetuses were grossly normal. The pathogenic effects of Kresse isolate were evident by gross pathology in fetuses collected at 18, 21, and 23 days PI, but not at 10 days PI. Hemagglutination (HA) and fluorescent antibody (FA) methods were used to identify virus in various tissues of late-gestation fetuses collected at 10 and 21 days PI. At 10 days PI, HA antigens were detected only in livers of NADL-8-inoculated fetuses, but in all tissues examined of Kresse-inoculated fetuses, including the brain. PPV specific fluorescence was demonstrated in tissues of fetuses inoculated with NADL-8 and Kresse virus. The major difference was that virus antigen was found in the brains of fetuses inoculated with Kresse virus, but not in NADL-8 infected fetuses. At 21 days PI, HA antigen was not detected in any of the tissues of fetuses inoculated with NADL-8 virus, with PPV specific fluorescence by FA being found only in the kidney. However, fetuses inoculated with Kresse virus displayed HA antigen in liver and PPV-specific fluorescence in all tissues tested including the brain. Both isolates induced similar antibody responses, 1:128 to 1:256 at 10 days and 1:512 to 1:1024 at 21 days PI. In addition, immunoglobulin G (IgG) deposits were demonstrated in kidneys and skin of fetuses inoculated with Kresse virus and IgM in brain, but not in tissues from fetuses inoculated with NADL-8 virus.     

The impact of naturally-occurring,trans-placental bluetongue virus serotype-8 infection on reproductive performance in sheep

Infection with bluetongue virus serotype (BTV)-8 occurred in ruminants in 2006 in Central-Western Europe. The trans-placental passage of this virus has been demonstrated in naturally- and experimentally-infected cattle and in experimentally-infected sheep. Trans-placental transmission is potentially important in the ‘over-wintering’ of this virus and its subsequent impact on reproductive performance. This epidemiological study was carried out on a sheep flock in Belgium that had experienced a severe outbreak of BTV-8 infection, and where the seroprevalence had increased from 1.3% to 88% between January and November 2007. In total, 476 lambs and 26 aborted fetuses from 300 ewes, lambing at four distinct time periods, were investigated between November 2007 and May 2008.The following evidence suggested that BTV-8 infection occurred in utero: (1) positive PCR results from splenic tissue from aborted fetuses (n = 4); (2) fetal malformations suggestive of BTV infection (n = 10); (3) positive PCR results from red blood cells in-lambs (n = 7), and (4) the presence of antibody at birth in viable lambs prior to the intake of colostrum (n = 9). The evidence provided by this investigation strongly suggests that trans-placental BTV-8 infection occurs in naturally-infected sheep and the impact of infection on the reproductive performance of such a naïve flock was considerable, with up to 25% of ewes aborting and with flock fertility reduced by 50%. The contribution of in utero-infected lambs to the over-wintering of BTV appears limited.     

Real-time PCR to detect and analyze virulent PPV loads in artificially challenged sows and their fetuses

To establish a real-time polymerase chain reaction with SYBR^® Green for detection and quantification of porcine parvovirus (PPV) in porcine tissues, two primers specific for the non-structural protein 1 gene were designed. The detection limit of this assay was 3–23 gene copies/reaction, equivalent to 0.001 TCID₅₀/ml. The assay was linear over a 10⁶ dilution range of template concentrations. Other porcine pathogens involved in reproductive disorders (porcine circovirus 2, porcine reproductive and respiratory virus, pseudorabies virus, classical swine fever virus) were negative by this assay. This assay could detect PPV titres at least 10⁵ smaller than the hemagglutination assay. To better understand the pathogenesis of PPV, the levels of viral DNA in various tissues of artificially challenged sows and their fetuses were quantified with this method. The virus was found mainly in the heart, lung, spleen, kidney, and endometrium of sows, and mainly in the heart, spleen, lung, and testis of fetuses. This study provides a new tool for the study of PPV infection and distribution in sows and their fetuses.     

Bovine Fetal Inoculations with Calf Rotavirus

The serological and histopathological responses of bovine fetuses to in utero inoculation with virulent and attenuated strains of the calf rotavirus (reovirus-like agent of neonatal calf diarrhea) are described. Thirteen bovine fetuses, 63 to 190 days of gestation, were inoculated in utero with attenuated (three fetuses) or field strain virus (nine fetuses) or both (one fetus).

Serum-neutralizing antibody titers ranging from 1:16 to > 1:256 were detected in six of eight fetuses tested, demonstrating the ability of the bovine fetus to respond immunologically to this agent. The youngest fetus in the series was inoculated at 63 days of gestation and developed a titer of 128 in 64 days. This represents the earliest stage of gestation at which a bovine fetus has been inoculated with a bovine virus and found to produce antibody to it. Serum neutralizing titers in six of the eight dams tested increased significantly following the inoculations of their fetuses in utero.

Histological changes associated with viral replication and antigenic stimulation of the lymphoreticular system were observed. Pneumonic lesions consisting of both local and diffuse lymphoreticular proliferation were present in five of the nine fetuses that were alive at slaughter. Gliosis and perivascular cuffing were noted in the brains of two of these fetuses and meningitis was seen in one. No evidence of teratogenic change was found.

     

Persistence of porcine parvovirus in swine infected in utero and followed through maturity

The potential of porcine parvovirus (PPV) to persistently infect swine exposed in utero was studied. Forty eight 80- to 95-day-old fetuses from 5 PPV seropositive sows were inoculated intramusculary with a virulent strain of PPV or with cell culture medium (controls). Blood samples were collected at birth prior to nursing and at monthly intervals thereafter and tested for antibodies to PPV. Virus-inoculated and control pigs were euthanized at either 1 week before birth (-1), at birth (0) and at weeks 2, 4, 6, 8, 10, 22, and 28 after birth. Presence of viral DNA and antigen was evaluated using slot blot DNA hybridization and indirect FA techniques, respectively. All inoculated fetuses (n = 26) and 7 control fetuses (n = 22) seroconverted in utero, and these pigs maintained antibody titers greater than log10 2 for the period of testing (0-38 weeks after birth). After passive antibody titers had reached subdetectable levels in control animals, animals remained seronegative through an additional 14 weeks of testing in spite of close contact with infected pigs. Virus antigen was not detected in any tissues examined from pigs euthanized at term. In contrast, PPV DNA was detected consistently from pigs at birth from various tissues, and from the lung of one pig at 6 weeks of age and from the lymph nodes of one pig euthanized at 28 weeks of age. The results indicate that pigs infected with PPV in utero may be persistently infected, however the likelihood of shedding to contact animals is minimal.     

Leptospirosis outbreak in a piggery in southern alberta

Fourteen abortions, stillbirths and neonatal deaths occurred over an interval of one month in crated sows in a farrow-to-finish swine operation. Leptospira interrogans serovar pomona (kennewicki by DNA analysis) was demonstrated by culture and fluorescent antibody test to be present in sows, piglets, boars, feeders, drinking water and skunks on the premises.

Antibody was found in all clinically affected sows, at serum dilutions ranging from 1/800 to 1/25,600, and in all breeding boars at titers from 1/50 to 1/1600. Pomona antibody was present in 118 sow sera collected nine months before the outbreak, at a prevalence of 21.3%. Parvovirus infection in fetuses was intercurrent with the leptospirosis epizootic, despite vaccination for the former. Environmental contamination, feedback through skunks via drinking water, and dissemination through the piggery are discussed.

     

Detection of challenge virus in fetal tissues by nested PCR as a test of the potency of a porcine parvovirus vaccine

To estimate the potency of a porcine parvovirus (PPV) vaccine, three vaccinated and three non-vaccinated pregnant gilts were infected with PPV and the distribution of the virus was studied in the tissues of their 51 fetuses. Virus detection was attempted using haemagglutination (HA) and immunofluorescence (IF) assays, as well as by standard (single) and nested polymerase chain reactions (PCR). None of the detection methods yielded positive results when used to test for the presence of virus in suspensions of organs from the fetuses from the vaccinated gilts. However, the virus was detected in the fetuses from non-vaccinated gilts as follows: HA was positive in 14 cases out of 23 (60.8%), IF in 16/23 (69.5%), standard PCR in 12/20 (60%), and the nested PCR in 19/23 (82.6%). Although the correlation among the results of various methods of virus detection was rather close (r<0.83), the sensitivity of the nested PCR was the highest, both when testing dilutions of PPV and when analysing the fetal organs. The nested PCR therefore provides a reliable approach for studies of virus distribution in fetal organs, with special reference to potency tests on vaccines.     

Serological investigation of granulocytic Ehrlichia infection in sheep in Norway

Serum samples of 749 sheep from 75 sheep flocks in Norway, i.e. 361 lambs (6 to 7 months old) and 388 adults (>1.5 year), were analysed for antibodies to Ehrlichia equi. Ten animals from each flock were examined. Seropositive animals were found along the coast of southern Norway from Vestfold to Sør-Trøndelag (as far north as 63°38''N). Seropositive sheep were not found in southeast, east or northern Norway. Thirty-two flocks were seropositive, although tick-borne fever had only been diagnosed earlier in half of these. In 78% of the seropositive flocks, more than 80% of the sheep were seropositive. A total of 35.7 % and 36.3 % of lambs and adults were found seropositive, respectively. However, the overall seroprevalence among animals that had been grazing on Ixodes pastures were 0.80 for the lambs and 0.84 for the adults. Mean antibody titres (± SD) (log₁₀) in seropositive lambs and adults were 2.59 (± 0.449) and 2.70 (± 0.481), respectively. No significant differences in either seroprevalence or mean antibody titre between sheep of different ages were obtained in this study. Based on antibodies 94% of sheep flocks on Ixodes pastures were infected with a granulocytic Ehrlichia infection. The association between seropositive flocks and Ixodes infested pasture shows a very high degree of agreement (p < 0.00001). The present study indicates that granulocytic Ehrlichia infection in sheep is underdiagnosed in Norway.     

Evaluation of the dynamic predictors of fluid responsiveness in dogs receiving goal-directed fluid therapy

Objectives

Goal-directed fluid therapy (GDFT) based on pulse pressure variation (PPV) was used in anaesthetized dogs undergoing abdominal surgeries. The aims were 1) to evaluate the success rate of the PPV ≥13% in detecting fluid responsiveness [delta stroke volume (ΔSV) ≥10%]; 2) to assess the correlation between PPV, systolic pressure variation (SPV), Plethysmograph Variability Index (PVI) and central venous pressure (CVP) and 3) to establish the threshold value for the PVI that would predict a PPV value of ≥13% and indirectly discriminate responders from nonresponders to fluid therapy.

Neospora caninum and complex vertebral malformation as possible causes of bovine fetal mummification

Bovine neosporosis, caused by Neospora caninum is a leading cause of abortion in cattle. We postulated that neosporosis could lead to fetal death and mummification. Fifteen mummified fetuses were tested by polymerase chain reaction (PCR) for the mutation in the bovine SLC35A3 gene that causes complex vertebral malformation (CVM) and the pNC-5 gene which identifies N. caninum infection. DNA was extracted from the mummified fetuses and the sex of the mummies was determined by PCR. The CVM mutation was not detected in the mummified fetuses, but 4 fetuses were positive for N. caninum infection. The ages of the mummies with N. caninum infection were 100, 113, 123, and 131 days. Twelve of the 15 mummified fetuses were male. To our knowledge, this is the first detection of N. caninum as a possible cause of bovine fetal mummification.     

Parvovirus Antibodies in Vaccinated Gilts in Field Conditions – Results with HI and ELISA tests

This study was conducted to determine the antibody response for porcine parvovirus (PPV) of 39 gilts in field conditions after vaccination. Gilts from four herds endemically infected with PPV were injected twice with a commercial vaccine of inactivated PPV and Erysipelothrix rhusiopathiae. The PPV antibodies were analysed both with haemagglutination inhibition (HI) and enzyme-linked immunosorbent assay (ELISA) in order to study the agreement between these methods. The possible association between high-antibody titres and reproductive failure (repeat breeding, culling for infertility, < or = 6 piglets born alive) was also investigated. In these study herds, endemically infected by PPV, most gilts (84.6%) had not seroconverted by the age of 6 months. On-field vaccination resulted in a consistent increase of humoral immunity not exceeding the antibody level of 1 : 512 in the majority of gilts in all herds examined. The agreement between ELISA and HI tests was moderate (Spearman's rho = 0.87, kappa = 0.63). The seroconversion over the level >1:512 by mid-pregnancy was not associated with reproductive failure.     

Serologic, virologic, and histopathologic observations of encephalomyocarditis virus infection in mummified and stillborn pigs

Stillborn and mummified swine fetuses from swine farms experiencing reproductive problems were investigated for evidence of infection with encephalomyocarditis (EMC) virus by fetal serology, virus isolation, and histopathologic examination. Fetal sera or thoracic fluids of 478 abnormal fetuses collected during January through December 1987 were tested for the presence of antibody specific to EMC virus. Of 478 samples tested, 175 (36.6%) had EMC virus serum neutralizing antibody titers of 1:64 or greater. The samples positive for EMC virus antibody were obtained from 38 swine farms located in 9 states in the United States. In addition to serologic observations, tissue samples of some abnormal fetuses were examined for the presence of virus and histopathologic lesions. The EMC virus was isolated in 1 case from the fetuses of an aborted litter. The isolate was serologically identical to a reference EMC virus. Nonsuppurative encephalitis and myocarditis were observed in the fetal samples collected from 2 different herds. Thoracic fluid of 1 stillborn pig with lesions was positive for EMC virus antibody at a titer of 1:512. We suggest that a widespread reproductive problem recently experienced in several major swine-producing areas of the United States may have been caused by EMC virus infection.     

Fetal protection against bovine viral diarrhea virus types 1 and 2 after the use of a modified-live virus vaccine

The objective of this study was to demonstrate the efficacy of a modified-live virus (MLV) vaccine in protecting fetuses from infection with type 1 or type 2 Bovine viral diarrhea virus (BVDV) when pregnant heifers were challenged at approximately 170 d of gestation with noncytopathic field isolates. The 83 pregnant heifers had been bred naturally 4 wk after vaccination. Fetuses were collected 60 d after BVDV type 2 challenge, and newborn calves were collected before colostrum intake after BVDV type 1 challenge. Protection was determined by measuring the serum neutralizing (SN) antibody response in the fetus or calf and by virus isolation from thymus, lung, spleen, and kidney tissue samples. There was a measurable SN antibody response to BVDV in all the fetuses and calves of the control heifers, which had received a placebo vaccine. However, only 4 of 22 calves and 7 of the 28 fetuses of the MLV-vaccinated heifers demonstrated SN antibody after BVDV challenge. Type 1 BVDV was isolated from tissue samples of 5 of the 12 calves of control heifers and none of 22 calves of the MLV-vaccinated heifers challenged with type 1 BVDV. Type 2 BVDV was isolated from tissue samples of 17 of the 18 fetuses of the control heifers and 2 of the 28 fetuses of the MLV-vaccinated heifers challenged with type 2 BVDV. The results of this study demonstrate that the MLV vaccine reduces the fetal infection rate by at least 82% for BVDV type 1 and by 75% for BVDV type 2 when heifers are exposed to highly fetotrophic BVDV at 170 d of gestation.     

Comparison of fluorescent antibody tests for tuberculosis and paratuberculosis with antigens coupled to insoluble spheres or taken up by macrophages

Sera of 106 cattle from farms with histories of Mycobacterium johnei infection and sera from 15 human tuberculous patients as well as a number of control sera were examined by means of two different fluorescent antibody tests (FAT) for the occurrence of antibodies against M. johnei and M. tuberculosis respectively. The antigens used were PPD johnin and PPD tuberculin. In the macrophage uptake FAT (MU/FAT) mouse macrophages after phagocytosis of the tuberculins served as the matrix; in the tests performed using the defined antigen substrate spheres (DASS) system, Sepharose beads activated by CNBr were used for the matrix. A good correlation was found between the results of the DASS/FAT and those of the MU/FAT, which is known to be a sensitive and specific test in the diagnosis of Johne's disease in cattle. It is suggested that the FAT, with utilization of the DASS system, might have good prospects for routine examination for antibodies against species of Mycobacterium.     

High Porcine Parvovirus Antibodies in Sow Herds: Prevalence and Associated Factors

Porcine parvovirus (PPV) is widespread among swine. Our objective was to determine the prevalence of loosely housed sow herds in Finland with at least one animal with high (infection level) PPV antibodies and to gather basic knowledge about vaccination practices. In addition, selected factors associated with high antibody levels found in sows were examined. Altogether, 247 animals were sampled in 21 randomly chosen loosely housed sow herds. Samples were analysed with the haemagglutination inhibition (HI) test. PPV proved to be common; in 17 farms (81%) at least one animal had a high titre (>1 : 512), and 44% of all animals sampled had a high titre. The vaccination programmes had many shortcomings. In the generalised estimation equations (GEE) population-averaged model developed, the factors found to have a significant (p < or = 0.05) effect on HI titres were herd size, parity of two or greater and storage of the vaccine vial after use. Non-returning rate, re-breeding interval and litter size did not differ between herds with no high HI titres (n = 4) and those with at least one high HI titre (n = 17).