In utero infection of swine fetuses with infectious bovine rhinotracheitis virus (bovine herpesvirus-1)

The pathogenesis of infectious bovine rhinotracheitis (IBR) virus (bovine herpesvirus-1) was studied in porcine fetuses after in utero inoculation. Laparotomies were performed on 8 seronegative pregnant sows at 34 to 86 days of gestation, and all fetuses in 1 uterine horn of each sow were exposed to IBR virus via inoculation into the amniotic sacs. Fetuses in the other horn served as controls. Clinical signs of infection were not observed in the sows, except for 2 sows that aborted at postinoculation days (PID) 11 and 15. Fetuses of the remaining 6 sows were collected at slaughter on PID 15 to 28. Fetuses were examined for gross abnormalities, presence of IBR virus in tissues, and the formation of neutralizing antibodies to IBR virus. Of 33 inoculated fetuses from 6 sows, 10 were mummified, 11 were hemorrhagic and/or edematous, and 12 were alive. Necrotic lesions were observed on the skin and in the liver of dead and live fetuses. Virus was recovered from 29 of 33 inoculated fetuses. Infectious bovine rhinotracheitis virus was isolated from fetal skin, liver, lungs, kidney, spleen, stomach contents, brain, amniotic fluid, and placenta. Virus was isolated from 4 of 11 fetuses recovered from 1 aborting sow. Antibodies to IBR virus were not detected in sera from the sows. However, antibodies were detected in 6 of 15 fetuses inoculated at 63 to 86 days of gestation and collected at slaughter at 86 to 112 days of gestation. The youngest fetus with detectable IBR antibody was estimated to be 74 days of gestation by measuring crown-rump length of the fetus.     

Experimental placental transfer of foot-and-mouth disease virus in mice.

An attenuated type O foot-and-mouth disease (FMD) virus which was virulent for infant, but not for pregnant, mice proved to be superior to a virulent type C FMD virus in the development of a model system for the study of placental transfer of FMD in mice. When mice were inoculated at day 8 or 12 of gestation with type O FMD virus, the virus was detectable in the maternal pancreas for 3 days and in the placenta for 6 days. Viral levels in the fetus and the amniotic fluid were inconsistent and were apparently due to a spillover from the placental infection. The elimination of the virus from the placenta coincided with the expected production of maternal 7S antibody. Mice inoculated from days 0 to 12 of gestation did not have a significant increase in dead young by day 18 (the day of necropsy). Similarly inoculated mice, when permitted to go to term, produced and raised normal-size litters. Inoculation on day 15 of gestation resulted in an increased number of deaths due to morbidity of the dams. It was concluded that the placenta serves as an active site of infection for FMD virus in pregnant mice, but the fetus is relatively resistant to infection.     

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.

     

Pathogenesis of porcine reproductive and respiratory syndrome virus infection in mid-gestation sows and fetuses.

Two experiments were undertaken to evaluate whether porcine reproductive and respiratory syndrome (PRRS) virus was able to cross the placenta and infect midgestation fetuses following intranasal inoculation of sows and whether PRRS virus directly infected fetuses following in utero inoculation. In experiment 1, eight sows between 45 and 50 days of gestation were intranasally inoculated with PRRS virus (ATCC VR-2332), and four control sows were inoculated with uninfected cell culture lysate. Virus inoculated sows were viremic on postinoculation (PI) days 1, 3, 5, 7 and 9, shed virus in their feces and nasal secretions, and became leukopenic. Sixty-nine of 71 fetuses from principal sows euthanized on PI day 7, 14 or 21 were alive at necropsy and no virus was isolated from any of the fetuses. Two principal sows that farrowed 65 and 67 days PI delivered 25 live piglets and three stillborn fetuses. The PRRS virus was isolated from two live piglets in one litter. In experiment 2, laparotomies were performed on five sows between 40 and 45 days of gestation and fetuses were inoculated in utero with either PRRS virus alone, PRRS virus plus a swine serum containing PRRS antibodies, or uninfected cell culture lysate. Three sows were euthanized on PI day 4 and two sows on PI day 11. Viral replication occurred in fetuses inoculated with virus alone and was enhanced in fetuses inoculated with virus plus antibody. No virus was isolated from control fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Experimental infection of pregnant goats with swine fever virus

Thirteen pregnant goats were inoculated intravenously with the ALD strain of virulent swine fever (SF) virus on Days 64-84 of gestation. Dams showed transient and mild viremia, and produced high serum neutralizing (SN) antibody after inoculation. Six inoculated dams were reared until parturition occurred and bore six apparently normal, one apparently normal but dead, one mummified and three edematous kids. Neutralizing antibody was demonstrated in the pre-colostral sera obtained from all normal kids, but no SF virus was isolated from any of them. The other seven dams were killed on post-inoculation days (PID) 5-61, and fetuses, placenta and amnion were tested for the virus and SN antibody. All fetuses of five dams examined within PID 40 were positive for SF virus, but negative for SN antibody. SF virus was also isolated from one of three fetuses examined on PID 61. Conversely, the other two fetuses examined on PID 61 were negative for SF virus, but positive for SN antibody. Furthermore, SF virus was isolated from the placenta and amnion of all the dams.     

Pathogenetic studies of infection of the bovine fetus with bovine viral diarrhea virus. II. Ocular lesions.

Twenty-three susceptible pregnant heifers were inoculated with bovine viral diarrhea virus at 150 +/- 1 days of gestation. Seven additional heifers were inoculated between 65 and 115 days of gestation. Acute ocular lesions were seen in fetuses taken 17-21 days after inoculation of the dams at 150 days. By the fourth week, the acute lesions were beginning to resolve, and in newborn animals focal to total retinal atrophy was seen. The acute lesions were characterized by a mild to moderate retinitis that resulted in various degrees of destruction of the different layers, mononuclear cuffing of inner retinal vessels, proliferation of pigment epithelium, and choroiditis. Residually there was an absence of cellular elements in the atrophied areas of the retina, frequently a loss of layering and various numbers of pigment-containing cells. Moderately severe acute inflammation was seen in the retina of the fetus taken at 22 days after inoculation of its dam at 95 days. Ocular lesions did not occur in the other fetuses taken from heifers inoculated at earlier stages of gestation.     

Demonstration of infectious bovine rhinotracheitis virus antigen in paraffin sections

Nine pregnant heifers were inoculated intravenously with infectious bovine rhinotracheitis virus (IBRV) in the sixth month of pregnancy. Tissues were collected from the fetus of a heifer killed 13 days postinoculation (PI), from fetuses of 6 heifers that aborted 16-27 days PI, and from mummified fetuses of 2 heifers that aborted 53 and 85 days PI, respectively. Control tissues were obtained from the fetus of a non-inoculated heifer that was killed in the seventh month of gestation. Tissues were fixed in 10% formalin, embedded in paraffin, and examined for viral antigen by immunohistochemistry, using biotinylated second antibody and alkaline phosphatase-labeled avidin-biotin complex. Antigen was detected in at least 1 tissue from the fetus of each inoculated heifer. Positive tissues included lung, liver, spleen, kidney, adrenal, and placenta. In several fetuses, antigen was identified in tissues from which virus was not isolated in cell culture. This appeared to occur when tissues had only a few small foci of infection or when tissues were severely autolyzed. The observation of viral antigen in tissues from mummified fetuses indicates that this technique may be useful in diagnostic laboratories to detect IBRV infection in tissues that are not suitable for virus isolation or for examination by the cryostat tissue section-fluorescent antibody technique.     

Fetal and maternal immunologic manifestations of intrauterine adenovirus SV-20 infection

Rhesus monkey fetuses of either immune or nonimmune dams were inoculated in utero with Adenovirus SV-20 (AdSV-20), a virus capable of inducing fetal pneumonia, and studied immunologically at various intervals. AdSV-20 infection at 90–100 days gestational age resulted in absolute lymphopenia in a few fetuses, reduced numbers of peripheral blood lymphocytes (PBL) which formed rosettes with sheep erythrocytes (ERL) and reduced complement-receptor lymphocytes (CRL) in a majority, while Fc fragment-receptor lymphocytes (FcRL) were occasionally increased. There was a tendency for depression of ERL and CRL early in infection of 120–130-day fetuses, followed by stimulation of these populations and FcRL in later phases. Maternal immunity did not protect against these effects of AdSV-20 infection in fetuses. Immune and nonimmune dams were spared adverse clinical effects and had no changes in lymphoid cell populations following inoculation of their fetuses.Despite precocious production of circulating IgM, fetuses of nonimmune dams had little or no demonstrable anti-AdSV-20 serum neutralizing (SN) antibody, indicating that the ability to develop an effective immune response was suppressed or had not been acquired at the gestational ages studied. Nonimmune dams displayed little evidence of seroconversion following inoculation of their fetuses with AdSV-20, except in those dams whose fetuses died in utero, whereby there was a significant antibody response. SN antibody titers of immune dams were not boostered substantially subsequent to inoculation of their fetuses, and fetal SN titers were lower than maternal titers, suggesting absence of an active fetal antibody response in this group also. Direct inoculation of AdSV-20 into 90–130-day rhesus monkey fetuses provided a model system for immunologic study of fetal infection, probably involving complex fetal-maternal interactions, in a situation where the infected, viable fetus and its dam appeared to be microbiologically isolated from one another.     

Experimental inoculation of Neospora caninum in pregnant water buffalo

The aim of this study was to characterize the pathogenesis of Neospora caninum in experimentally inoculated pregnant water buffalo (Bubalus bubalis). Twelve Mediterranean female water buffaloes ranging in age from 4 to 14 years old and seronegative to N. caninum by indirect fluorescent antibody test (IFAT) were involved. Ten females were intravenously inoculated with 10(8) tachyzoites of NC-1 strain at 70 (n=3) or 90 (n=7) days of pregnancy (dp). Two control animals were inoculated with placebo at 70 and 90 dp, respectively. Serum samples were obtained weekly following inoculation to the end of the experiment. Three animals inoculated at 70 dp were slaughtered at 28 days post inoculation (dpi), three animals inoculated at 90 dp were slaughtered at 28 dpi and the remaining four animals inoculated at 90 dp were slaughtered at 42 dpi. Fetal fluids from cavities and tissue samples were recovered for IFAT and histopathology, immunohistochemistry and PCR, respectively. Genomic DNA from fetal tissues was used for parasite DNA detection and microsatellite genotyping in order to confirm the NC-1 specific-infection. Dams developed specific antibodies one week after the inoculation and serological titers did not decrease significantly to the end of the experiment. No abortions were recorded during the experimental time; however, one fetus from a dam inoculated at 70 dp was not viable at necropsy. Specific antibodies were detected in only two fetuses from dams inoculated at 90 dp that were slaughtered at 42 dpi. No macroscopic changes in the placentas and organs of viable fetuses were observed. Nonsuppurative placentitis was a common microscopic observation in Neospora-inoculated specimens. Microscopic fetal lesions included nonsuppurative peribronchiolar interstitial pneumonia, epicarditis and myocarditis, interstitial nephritis, myositis and periportal hepatitis. Positive IHC results were obtained in two fetuses from dams inoculated at 70 dp and slaughtered at 28 dpi. N. caninum DNA was detected in placentas and fetuses from all inoculated animals. The pattern of amplified microsatellites from placental and fetal tissues resembled the NC-1 strain. Water buffaloes, like cattle, are susceptible to experimental inoculation with N. caninum at early pregnancy.     

Infection of bovine fetuses at 120 days' gestation with virulent and avirulent strains of bluetongue virus serotype 11.

Bluetongue virus infection in sheep and cattle during fetal development causes neuropathology. Two strains of bluetongue virus serotype 11 designated as UC-2 and UC-8 have different virulence patterns in newborn mice. These viruses have distinctly different electropherotype patterns on polyacrylamide gel electrophoresis indicating a genetic difference in these two viruses of the same serotype. Four bovine fetuses each were inoculated intramuscularly with either UC-2 or UC-8, and one fetus was inoculated with placebo. The inoculation was made intramuscularly through the uterine wall at 120 days' gestation, and the bovine fetuses were recovered by cesarean section 12 or 20 days after inoculation. Fetal blood was collected for virus isolation and serology. Virus was reisolated from brain, blood, lung and liver. Both strains, UC-2 and UC-8, cause severe lesions in the 120 day fetuses. The encephalomalacic lesions occurred earlier and were more severe in fetuses inoculated with UC-8 as compared to those inoculated with UC-2. The subtle differences observed in the fetuses inoculated with the two different strains suggest that there is a difference in pathogenic potential of the two viruses. These differences do not appear to be completely dependent upon the host species.     

Pathology of Campylobacter jejuni abortion in sheep

Campylobacter jejuni was inoculated intravenously into pregnant ewes on gestation days 114 and 123 to reproduce ovine abortion. All ewes aborted 7-12 days post-inoculation. High numbers of C. jejuni were isolated from ewe tissues (caruncle, bile, cecal feces), fetal tissues, and placenta. C. jejuni colonies were identified in caruncles and placenta by light microscopy and immunoperoxidase techniques. Histologically, inoculated ewes had a severe purulent endometritis with vasculitis. Placentas from inoculated ewes and field cases showed necrosis and purulent inflammation; however, placentas from inoculated ewes had large numbers of bacterial colonies compared to few bacteria found in field cases. Histologically, only one fetus from the inoculated ewes showed lesions (purulent bronchopneumonia), whereas all fetuses from field cases had a distinct bronchopneumonia, and one fetus showed multifocal hepatic necrosis. These results suggest that C. jejuni (serotypes Penner 1 and Lior 2) is an important abortifacient organism for sheep.     

Porcine fetuses with pulmonary hypoplasia resulting from experimental swine influenza virus infection

Porcine fetuses between 51 and 57 days of gestation were inoculated intraallantoically with swine influenza virus and examined 3, 7, 13, 28 and 58 days after inoculation. At 3 and 7 days, severe epithelial necrosis was seen in most bronchial buds and there was moderate epithelial necrosis in more fully differentiated major bronchi. As a result of the epithelial injury, bronchial buds did not develop further and the surrounding mesoderm failed to differentiate. By 28 days, the lungs of inoculated fetuses were about one-half the size of the normal control lungs. Microscopically, the lungs of the inoculated fetuses were composed of major bronchi surrounded by multiple islands of cartilage, medium to large arteries and a few small, incompletely developed lobules. Influenza virus was isolated most consistently and in greatest quantity from the lung, trachea and chorion of inoculated fetuses. Influenza viral antigen was shown in the epithelium of bronchial buds, bronchi and the trachea by direct fluorescent antibody staining. Hemagglutination inhibiting antibodies to influenza virus were first found in the serum of an inoculated fetus at 13 days and in the sera of all inoculated fetuses at 28 and 58 days.     

Placental transfer of specific antibodies during ovine congenital toxoplasmosis

The passage of non-Toxoplasma antibodies from dam to fetus through damaged placenta was studied in sheep inoculated with Toxoplasma gondii. Six ewes were inoculated with chicken globulins and Leptospira bacterins 2 months before oral inoculation with Toxoplasma gondii oocysts. Ewes were euthanatized between 42 and 62 days after T gondii inoculation. Antibody titers against chicken globulins, Leptospira spp, Haemonchus contortus, Sarcocystis spp, and T gondii were measured in the maternal and fetal sera. All ewes became infected with T gondii and had grossly visible necrotic foci in the placentas, and T gondii antibodies were found in the fetuses and the ewes. Appreciable amounts of antibodies to Haemonchus contortus, Sarcocystis sp, Leptospira spp, and chicken globulins did not cross the placental barrier. Seemingly, serologic examination of the fetus was reliable for the diagnosis of ovine congential toxoplasmosis.     

Toxoplasma gondii cysts in placentas of experimentally infected sheep

To determine the presence of tissue cysts in ovine placentas, 6 ewes were inoculated orally with 10,000 Toxoplasma gondii oocysts at 60 days of gestation. The ewes were euthanatized and necropsied 21, 52, 56, 57, 57, and 62 days after T gondii inoculation, and placental cotyledons from each ewe were collected and homogenized. To distinguish between the presence of tachyzoites that are killed by acid pepsin solution and bradyzoites (from cysts) unaffected by this solution, a portion of each homogenate was inoculated into mice and another portion was inoculated into mice after digestion in acid pepsin solution. Toxoplasma gondii was isolated in 26 of 34 (76.4%) of mice inoculated with nondigested placentas of all 6 ewes and in 16 of 34 (47%) mice inoculated with digested placenta of 5 of 6 ewes. Seemingly, cysts do occur in placental tissue, but the digestion method was inferior, compared with the nondigestion method for recovery of T gondii from placenta.     

Studies on the response of ewes to live chlamydiae adapted to chicken embryos or tissue culture.

Ewes infected before gestation with chicken embryo or tissue culture adapted chlamydial strain B-577 were challenge inoculated with the homologous strain at four to 18 weeks of gestation. The ewes responsed with group specific complement fixing antibody titers of 1:8 to 1:256 by the second week after initial infection. A secondary antibody response in the surviving challenge inoculated ewes occurred at the time of lambing and reached titers of 1:32 to 1:256 by the second week after parturition. Group specific complement fixing antibodies did not appear to play a significant role in resistance to chlamydial infection. Ewes infected with the chicken embryo adapted strain B-577 excreted chlamydiae in their feces 60 days after inoculation. However, chlamydiae were not recovered from feces of ewes infected with the tissue culture adapted strain B-577. Placentas of ewes challenge inoculated by the intravenous route were consistently infected. Chlamydiae were recovered from placentas, some fetuses and lambs. In two instances when challenge inoculation was given by the intramuscular route, infection was detected only by the direct fluorescent antibody method.     

Bovine virus diarrhoea-mucosal disease virus: pathogenicity for the fetal calf following maternal infection

Fifteen pregnant, bovine virus diarrhoea-mucosal disease (BVD-MD) antibody-free Jersey heifers were infected experimentally with a mixture of 10 cytopathic strains of BVD-MD virus isolated from cattle in Britain. Each cow was inoculated intramuscularly on gestation day 100 with a high or a low dose of virus grown in primary calf testis tissue cultures. None of the cows showed clinical signs of illness following exposure, but all had seroconverted within six weeks. Six fetuses, including one set of twins, died in utero following infection. Of these five were aborted between days 136 and 154; the sixth one was mummified and still retained at day 300. The remaining 10 fetuses survived to term, but all showed evidence of intrauterine growth retardation with or without gross malformation and/or dysmyelination of the central nervous system. Three were clinically affected with congenital nervous disease. Of the 10 liveborn fetuses, two had specific serum antibodies to BVD-MD. Non-cytopathic BVD-MD virus was recovered from all of the remaining eight. When non-immune cows become infected with BVD-MD virus in mid gestation: transplacental infection of the fetus will probably result; apart from the risk of fetal death, with or without abortion, there is a high probability of fetal mal-development which may not always be clinically obvious; the immunological competence of the fetus may be impaired; congenital infection is likely in a substantial proportion of liveborn calves. About one in 16 bovine fetuses in British herds are estimated to be at risk from BVD-MD virus infection.     

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.     

Lymphocyte blastogenesis in bluetongue virus or Mycobacterium bovis-inoculated bovine fetuses

Bovine fetuses were inoculated with Mycobacterium bovis, bluetongue virus or placebo at approximately 125 days of gestation, and blastogenic responses of peripheral blood lymphocytes and lymph node cells were determined at various time intervals after inoculation. Lymphocytes from all fetuses were stimulated by phytohemagglutinin, concanavalin A, and pokeweed mitogen, and peripheral blood lymphocytes gave consistently greater stimulation indices than did prescapular lymph node cells. Bluetongue virus infection did not consistently suppress mitogen induced lymphocyte blastogenesis. Lymphocytes taken from fetuses at 20 or 50 days after Mycobacterium bovis inoculation were not stimulated by purified protein derivative (PPD), whereas lymphocytes taken from adult cattle at similar intervals after Mycobacterium bovis inoculation were stimulated by PPD. Although lymphocytes from bovine fetuses may be stimulated by mitogens, antigen specific blastogenesis to a known inducer of cellular immunity was not detected by 175 days of gestation.     

Experimental placental transfer of Akabane virus in the hamster

Transplacental infection of hamster fetuses was produced by inoculation of pregnant hamsters with 10(6.3) plaque-forming units (PFU) of Akabane virus by either the intraperitoneal or the subcutaneous route. Virus with titers as high as 10(7.5) PFU/g of tissue was detected first in the placenta and later in the fetus. Virus could also be readily isolated from blood, lung, spleen, and liver of both pregnant and nonpregnant hamsters, but it reached higher titers and persisted longer in the placenta and fetus. Young dying at birth had Akabane virus titers as high as 10(7.3) PFU/g of brain tissue. Litter size was reduced by inoculation of the pregnant hamster at gestational day 11 or earlier, and survival of the newborn to 1 week of age was decreased by inoculation at gestational day 9 or later.     

Experimental transplacental transmission of canine herpesvirus in pregnant bitches during the second trimester of gestation

The effects of canine herpesvirus (CHV) on fetuses were studied after IV inoculation of pregnant bitches in the 2nd trimester of gestation. Cesarean sections were performed on 2 bitches that were inoculated with CHV on the estimated 30th day of gestation. Bitch M-1 had 2 mummified fetuses and bitch M-2 had 4 mummified and 2 dead fetuses and 3 live-born pups. Infection by CHV was confirmed histopathologically by the presence of focal areas of necrosis associated with intranuclear inclusion bodies in heart muscle sections of 1 dead fetus; CHV was not recovered from other organs. Abortion occurred between the 2nd and 3rd week after inoculation of another pregnant bitch inoculated with CHV on the estimated 30th day of gestation. Two bitches inoculated with CHV on the estimated 40th day of gestation gave birth prematurely to 10 pups. The detection of characteristic herpesviral lesions in various organs and the reisolation of CHV from the liver, spleen, kidneys, and lungs of premature pups indicated CHV infection. Transplacental infection of fetal pups by CHV resulted in their death and subsequent mummification. It appears that abortion and premature birth also may occur in pregnant bitches infected during the 2nd trimester of gestation.