Herpesviral abortion in domestic animals

Narrative Review of the Safety of Using Pigs for Xenotransplantation: Characteristics and Diagnostic Methods of Vertical Transmissible Viruses

Amid the deepening imbalance in the supply and demand of allogeneic organs, xenotransplantation can be a practical alternative because it makes an unlimited supply of organs possible. However, to perform xenotransplantation on patients, the source animals to be used must be free from infectious agents. This requires the breeding of animals using assisted reproductive techniques, such as somatic cell nuclear transfer, embryo transfer, and cesarean section, without colostrum derived in designated pathogen-free (DPF) facilities. Most infectious agents can be removed from animals produced via these methods, but several viruses known to pass through the placenta are not easy to remove, even with these methods. Therefore, in this narrative review, we examine the characteristics of several viruses that are important to consider in xenotransplantation due to their ability to cross the placenta, and investigate how these viruses can be detected. This review is intended to help maintain DPF facilities by preventing animals infected with the virus from entering DPF facilities and to help select pigs suitable for xenotransplantation.

Characterization of placentome vascular perfusion in relation to pregnancy associated glycoproteins throughout gestation in pregnant beef heifers

During pregnancy, blood flow to the uterus changes to support fetal demand. Placentomes serve as vascular attachment sites on the placenta for exchange of gases, nutrients, and metabolic products. Non-invasive methods of ultrasonography and biomarkers have been described to assess placental health and fetal viability. Pregnancy associated glycoproteins (PAGs) are produced by the ruminant placenta and are detected in maternal circulation. In cattle, changes in circulating PAG concentrations are associated with embryonic and fetal outcomes. The objective of this study was to determine the association between placentome blood perfusion and circulating PAG concentrations as they relate to the health of the developing fetus. We hypothesized that placentome perfusion and PAG concentration will be positively correlated and associated with neonatal outcome. A prospective, observational study was designed using 26 pregnant, nulliparous, Angus heifers in which PAG concentration and placentome blood perfusion were assessed throughout gestation, with assessment of calving characteristics following parturition. Placentome blood perfusion was visualized at 30-day intervals via transrectal Doppler ultrasonography with power flow function. Ultrasound images were analyzed using ImageJ software to determine the percent area of perfusion and integrated pixel densities. Venous blood was collected and PAG concentrations were determined via serum PAG enzyme-linked immunoassay. Mean placentome blood perfusion increased as gestation advanced. PAG concentrations demonstrated the expected temporal trend, increasing with gestation length, and were positively linearly correlated with placentome perfusion (P < 0.0001). The relationship identified between circulating PAG concentration and placentome blood perfusion suggests the use of transrectal power flow Doppler ultrasonography as a noninvasive technique to determine placental blood flow morphometrics to assess conceptus wellbeing throughout pregnancy.

Pseudorabies virus inhibits progesterone-induced inactivation of TRPML1 to facilitate viral entry

Viral infection is a significant risk factor for fertility issues. Here, we demonstrated that infection by neurotropic alphaherpesviruses, such as pseudorabies virus (PRV), could impair female fertility by disrupting the hypothalamus-pituitary-ovary axis (HPOA), reducing progesterone (P4) levels, and consequently lowering pregnancy rates. Our study revealed that PRV exploited the transient receptor potential mucolipin 1 (TRPML1) and its lipid activator, phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2), to facilitate viral entry through lysosomal cholesterol and Ca2+. P4 antagonized this process by inducing lysosomal storage disorders and promoting the proteasomal degradation of TRPML1 via murine double minute 2 (MDM2)-mediated polyubiquitination. Overall, the study identifies a novel mechanism by which PRV hijacks the lysosomal pathway to evade P4-mediated antiviral defense and impair female fertility. This mechanism may be common among alphaherpesviruses and could contribute significantly to their impact on female reproductive health, providing new insights for the development of antiviral therapies.

Adverse weather during in utero development is linked to higher rates of later-life herpesvirus reactivation in adult European badgers, Meles meles

Maternal immune and/or metabolic conditions relating to stress or nutritional status can affect in utero development among offspring with subsequent implications for later-life responses to infections. We used free-ranging European badgers as a host-pathogen model to investigate how prenatal weather conditions affect later-life herpesvirus genital tract reactivation. We applied a sliding window analysis of weather conditions to 164 samples collected in 2018 from 95 individuals born between 2005-2016. We test if the monthly mean and variation in rainfall and temperature experienced by their mother during the 12 months of delayed implantation and gestation prior to parturition subsequently affected individual herpes reactivation rates among these offspring. We identified four influential prenatal seasonal weather windows that corresponded with previously identified critical climatic conditions affecting badger survival, fecundity and body condition. These all occurred during the pre-implantation rather than the post-implantation period. We conclude that environmental cues during the in utero period of delayed implantation may result in changes that affect an individual's developmental programming against infection or viral reactivation later in life. This illustrates how prenatal adversity caused by environmental factors, such as climate change, can impact wildlife health and population dynamics-an interaction largely overlooked in wildlife management and conservation programmes.

Research Relevant Background Lesions and Conditions: Ferrets, Dogs, Swine, Sheep, and Goats

Animal models provide a valuable tool and resource for biomedical researchers as they investigate biological processes, disease pathogenesis, novel therapies, and toxicologic studies. Interpretation of animal model data requires knowledge not only of the processes/diseases being studied but also awareness of spontaneous conditions and background lesions in the model that can influence or even confound the study results. Species, breed/stock, sex, age, anatomy, physiology, diseases (noninfectious and infectious), and neoplastic processes are model features that can impact the results as well as study interpretation. Here, we review these features in several common laboratory animal species, including ferret, dog (beagle), pig, sheep, and goats.

An Improved DNA Vaccine Against Bovine Herpesvirus-1 Using CD40L and a Chemical Adjuvant Induces Specific Cytotoxicity in Mice

Bovine herpesvirus-1 (BoHV-1) uses many mechanisms to elude the immune system; one of them is spreading intracellularly, even in the presence of specific antiviral antibodies. Cytotoxic T lymphocytes (CTLs) are necessary to eliminate the virus. The main preventive strategy is vaccination based on inactivated virus. These vaccines are poor inducers of cellular immune responses, and complicate serological diagnosis and determination of the real prevalence of infection. DNA vaccines are a good option because of the capacity of Differentiating Infected from Vaccinated Animals-(DIVA vaccine)-and may be the best way to induce cytotoxic responses. Although this type of vaccines leads to only weak "in vivo" expression and poor immune responses, incorporation of molecular and/or chemical adjuvants can improve the latter, both in magnitude and in direction. In this study, we have investigated the specific immune responses elicited in mice by DNA vaccines based on the BoHV-1 glycoprotein D (pCIgD) with and without two different adjuvants: a plasmid encoding for murine CD40L (pCD40L) or Montanide™ 1113101PR (101). Mice vaccinated with pCIgD⁺CD40L, pCIgD⁺101, and pCIgD⁺CD40L⁺101 developed significantly higher specific antibody titers against BoHV-1 than the pCIgD group (p < 0.01). The animals vaccinated with pCgD⁺pCD40L⁺101 raised significantly higher levels of IgG2a and IgG2b (p < 0.01 and p < 0.001, respectively) than mice vaccinated with pCIgD alone. On the contrary, when the activity of CTL against cells infected with BoHV-1 was measured, the vaccine pCgD⁺pCD40L⁺101 induced significantly higher levels of cytotoxicity activity (p < 0.001) than pCIgD alone. A significant increase in the CD4⁺ populations in the group receiving pCIgD⁺CD40L⁺101 in comparison with the pCIgD group was observed and, also, interferon gamma, interleukin (IL)-6, and IL-17A levels were higher. Considering the results obtained from this study for humoral and cellular responses in mice, the inclusion of pCD40L and 101 as adjuvants in a BoHV-1 DNA vaccine for cattle is highly recommendable.

Effects of Mustelid gammaherpesvirus 1 (MusGHV-1) Reactivation in European Badger (Meles meles) Genital Tracts on Reproductive Fitness

Reactivation of latent Gammaherpesvirus in the genital tract can lead to reproductive failure in domestic animals. Nevertheless, this pathophysiology has not received formal study in wild mammals. High prevalence of Mustelid gammaherpesvirus 1 (MusGHV-1) DNA detected in the genital tracts of European badgers (Meles meles) implies that this common pathogen may be a sexual transmitted infection. Here we used PCR to test MusGHV-1 DNA prevalence in genital swabs collected from 144 wild badgers in Ireland (71 males, 73 females) to investigate impacts on male fertility indicators (sperm abundance and testes weight) and female fecundity (current reproductive output). MusGHV-1 reactivation had a negative effect on female reproduction, but not on male fertility; however males had a higher risk of MusGHV-1 reactivation than females, especially during the late-winter mating season, and genital MusGHV-1 reactivation differed between age classes, where 3-5 year old adults had significantly lower reactivation rates than younger or older ones. Negative results in foetal tissues from MusGHV-1 positive mothers indicated that cross-placental transmission was unlikely. This study has broader implications for how wide-spread gammaherpesvirus infections could affect reproductive performance in wild Carnivora species.

Fetal lesions of EHV-1 in equine

EHV-1 infection is responsible for huge economic losses in equines due to abortion and neonatal mortality. In this study, we describe 4 cases of abortion and neonatal deaths from pregnant mares and a she-donkey from different localities in Egypt during the period from May 2015 to October 2017. Attempts were made to isolate and identify EHV-1, in addition to compare the different pathological lesions in various tissues of the necropsied cases. EHV-1 was successfully isolated from two aborted fetuses and one dead neonatal foal from mares, beside one aborted fetus from a she-donkey. The positive cases showed cytopathic effect on embryonated chicken eggs scattered on chorioallantoic membrane. Moreover, PCR was applied for the pock lesions and revealed positive results for EHV-1. Interstitial pneumonia, bronchopneumonia and necrosis of hepatic, myocardial, microcotyledonary tissues besides disseminated thrombi were the main encountered lesions. Intranuclear inclusion bodies were demonstrated in brain, liver, placenta and pulmonary tissues. Here, we describe EHV-1 induced brain lesions represented by degenerated neurons, vascular endotheliosis with intranuclear inclusion bodies in the aborted she-donkey fetus. Lesions were more sever in the aborted fetuses from mares than the one from the she-donkey. EHV-1 antigen was detected by immunohistochemistry staining.

Histopathologic Findings Following Experimental Equine Herpesvirus 1 Infection of Horses

Histopathological differences in horses infected with equine herpesvirus type 1 (EHV-1) of differing neuropathogenic potential [wild-type (Ab4), polymerase mutant (Ab4 N752), EHV-1/4 gD mutant (Ab4 gD4)] were evaluated to examine the impact of viral factors on clinical disease, tissue tropism and pathology. Three of 8 Ab4 infected horses developed Equine Herpesvirus Myeloencephalopathy (EHM) requiring euthanasia of 2 horses on day 9 post-infection. None of the other horses showed neurologic signs and all remaining animals were sacrificed 10 weeks post-infection. EHM horses had lymphohistiocytic vasculitis and lymphocytic infiltrates in the lungs, spinal cord, endometrium and eyes. EHV-1 antigen was detected within the eyes and spinal cord. In 3/6 of the remaining Ab4 infected horses, 4/9 Ab4 N752 infected horses, and 8/8 Ab4 gD4 infected horses, choroiditis was observed. All males had interstitial lymphoplasmacytic and/or histiocytic orchitis and EHV-1 antigen was detected. In conclusion, only animals sacrificed due to EHM developed overt vasculitis in the CNS and the eye. Mild choroiditis persisted in many animals and appeared to be more common in Ab4 gD4 infected animals. Finally, we report infiltrates and changes in the reproductive organs of all males associated with EHV-1 antigen. While the exact significance of these changes is unclear, these findings raise concern for long-term effects on reproduction and prolonged shedding of virus through semen.

Abortigenic but Not Neurotropic Equine Herpes Virus 1 Modulates the Interferon Antiviral Defense

Equine herpesvirus 1 (EHV1) is considered as a major pathogen of Equidae, causing symptoms from mild respiratory disease to late-term abortion and neurological disorders. Different EHV1 strains circulating in the field have been characterized to be of abortigenic or neurovirulent phenotype. Both variants replicate in a plaque-wise manner in the epithelium of the upper respiratory tract (URT), where the abortigenic strains induce more prominent viral plaques, compared to the neurovirulent strains. Considering the differences in replication at the URT, we hypothesized that abortigenic strains may show an increased ability to modulate the type I IFN secretion/signaling pathway, compared to strains that display the neurovirulent phenotype. Here, we analyze IFN levels induced by abortigenic and neurovirulent EHV1 using primary respiratory epithelial cells (EREC) and respiratory mucosa ex vivo explants. Similar levels of IFNα (~70 U/ml) were detected in explants inoculated with both types of EHV1 strains from 48 to 72 hpi. Second, EREC and mucosa explants were treated with recombinant equine IFNα (rEqIFNα) or Ruxolitinib (Rux), an IFN signaling inhibitor, prior to and during inoculation with abortigenic or neurovirulent EHV1. Replication of both EHV1 variants was suppressed by rEqIFNα. Further, addition of Rux increased replication in a concentration-dependent manner, indicating an IFN-susceptibility for both variants. However, in two out of three horses, at a physiological concentration of 100 U/ml of rEqIFNα, an increase in abortigenic EHV1 replication was observed compared to 10 U/ml of rEqIFNα, which was not observed for the neurovirulent strains. Moreover, in the presence of Rux, the plaque size of the abortigenic variants remained unaltered, whereas the typically smaller viral plaques induced by the neurovirulent variants became larger. Overall, our results demonstrate the importance of IFNα in the control of EHV1 replication in the URT for both abortigenic and neurovirulent variants. In addition, our findings support the speculation that abortigenic variants of EHV1 may have developed anti-IFN mechanisms that appear to be absent or less pronounced in neurovirulent EHV1 strains.

Research on viral agents associated with feline reproductive problems reveals a high association with feline panleukopenia virus

Although reproductive failures (RF) such as abortion, stillbirth and neonatal mortality in cats are still under researched, it is known that many RF are caused by viral agents. This research surveyed the viral agent prevalence in queens with RF. Queens were excluded from the study if their RF was caused by issues other than infection, such as genetic, traumatic, hormonal or nutritional problems, or if they had a history of RF. Blood samples from 26 pregnant females with RF were collected for complete blood counts (BCC), renal/hepatic biochemistry and glycaemic analysis. Ultrasonography was performed to evaluate gestational age and foetal viability. When possible, placentas, humours and foetal tissues were collected. Blood samples were tested by PCR and qPCR for feline leukaemia virus (FeLV), feline immunodeficiency virus (FIV), feline alphaherpesvirus 1 (FeHV-1) and carnivore protoparvovirus 1 (CPPV-1). All maternal samples were negative for FeLV, FIV and FeHV-1 and positive for CPPV-1. In addition, foetuses from one queen and three females were positive for CPPV-1 by qPCR and for feline panleukopenia virus (FPV) through DNA sequencing. The BCC and biochemistry results revealed significant neutrophilia, lymphopenia, monocytosis, and liver enzymes. These results provide the first description of an FPV agent causing only RF-related clinical signs in queens.

Bovine herpesvirus-1 in three major milk sheds of Ethiopia: Serostatus and association with reproductive disorders in dairy cattle

Bovine herpesvirus-1 (BHV-1) causes infectious bovine rhinotracheitis (IBR), and infectious pustular vulvovaginitis (IPV) in cows and infectious pustular balanopostitis (IPB) in bulls worldwide. Infection of seronegative cattle with BHV-1 leads to abortion, retention of fetal membranes, increased service per conception, metritis and oophoritis. As part of an ongoing study on infectious causes of reproductive disorders in Ethiopia, this investigation aims at assessing the role of BHV-1 in the disorders and the risk factors affecting its seroprevalence. A cross-sectional study was conducted on a total of 1379 randomly selected dairy cattle from 149 herds. These dairy cattle were sampled from milks sheds of central (n = 555), western (n = 195) and southern (n = 629) Ethiopia. Blocking enzyme-linked immunosorbent assay (B-ELISA) was applied to detect antibodies specific to BHV-1. Additionally, a semi-structured questionnaire was administered and farm records were assessed to capture potential risk factors associated with BHV-1 seropositivity. Univariable and multivariable random-effects logistic regression analyses were used to assess potential risk factors associated with BHV-1 serostatus. Model fitness and reliability were assessed using the Hosmer and Lemeshow method and the receiver operating curve (ROC) respectively. An overall herd level BHV-1 seroprevalence of 81.8% (95% confidence interval (CI): 74.7-87.7%) and individual animal level seroprevalence of 41.0% (95% CI: 38.4-43.7%) were found. In a random-effects multivariable logistic regression model, the seroprevalence of BHV-1 exposure was higher in dairy cattle from breeding (Odds ratio [OR] = 1.3; p = 0.036) than in commercial (OR = 0.9; p = 0.137) and small-holder farms. Geographically, the prevalence was higher in western (OR = 1.4; p < 0.001) and southern Ethiopia (OR = 1.2; p < 0.001) than in central regions. BHV-1 seropositive cows had higher (p < 0.05) odds of clinical reproductive disorders including abortion, retained fetal membranes, stillbirth, birth of weak calf and metritis compared to seronegative cows. Thus, it is suggested that BHV-1 should be considered as differential diagnosis among improved dairy cattle herds with reproductive disorders in Ethiopia.

Isolation of Equine Herpesvirus–2 from the Lung of an Aborted Fetus

This study describes the isolation of equine herpesvirus–2 (EHV-2) from the lung of an aborted equine fetus in Argentina. The isolated virus was confirmed as EHV-2 by indirect immunofluorescence using a rabbit anti–EHV-2 polyclonal antiserum and by virus-neutralization test using an equine polyclonal antibody against EHV-2. Restriction endonuclease DNA fingerprinting with BamHI also confirmed the identity of the virus as EHV-2. Furthermore, viral nucleic acid was detected by polymerase chain reaction from the original lung sample and from the DNA obtained from cells infected with the virus isolate. This work constitutes the first reported isolation of EHV-2 from an aborted equine fetus. The presence of EHV-2 in the lung of the aborted fetus would indicate that this virus is capable of crossing the placental barrier. However, no cause–effect relationship was established between the EHV-2 isolate and the abortion.

Inhibitors of nucleotidyltransferase superfamily enzymes suppress herpes simplex virus replication

Herpesviruses are large double-stranded DNA viruses that cause serious human diseases. Herpesvirus DNA replication depends on multiple processes typically catalyzed by nucleotidyltransferase superfamily (NTS) enzymes. Therefore, we investigated whether inhibitors of NTS enzymes would suppress replication of herpes simplex virus 1 (HSV-1) and HSV-2. Eight of 42 NTS inhibitors suppressed HSV-1 and/or HSV-2 replication by >10-fold at 5 μM, with suppression at 50 μM reaching ∼1 million-fold. Five compounds in two chemical families inhibited HSV replication in Vero and human foreskin fibroblast cells as well as the approved drug acyclovir did. The compounds had 50% effective concentration values as low as 0.22 μM with negligible cytotoxicity in the assays employed. The inhibitors suppressed accumulation of viral genomes and infectious particles and blocked events in the viral replication cycle before and during viral DNA replication. Acyclovir-resistant mutants of HSV-1 and HSV-2 remained highly sensitive to the NTS inhibitors. Five of six NTS inhibitors of the HSVs also blocked replication of another herpesvirus pathogen, human cytomegalovirus. Therefore, NTS enzyme inhibitors are promising candidates for new herpesvirus treatments that may have broad efficacy against members of the herpesvirus family.

Epidemiology and reproductive outcomes of EHV-1 abortion epizootics in unvaccinated Thoroughbred mares in South Africa

REASONS FOR PERFORMING STUDY

Equine herpesvirus 1 (EHV-1) is one of the most common causes of infectious abortion in mares. Analysing the demography of outbreaks and detailing subsequent reproductive performance of affected mares will assist in the management of future (threatened) epizootics.

OBJECTIVES

To examine the epidemiology and reproductive outcomes of 2 EHV-1 abortion epizootics with very different patterns of morbidity.

STUDY DESIGN

Epidemiological and reproductive data were analysed retrospectively following abortion epizootics associated with EHV-1, but initiated via different routes, among unvaccinated mares on 2 Thoroughbred farms in South Africa.

METHODS

Aborting mares were assigned to either the EHV-1 abortion cohort via positive immunostaining (Farms 1 and 2) or quantitative PCR (Farm 2) on tissue samples, or to the non-EHV abortion cohort.

RESULTS

During their respective epizootics, EHV-1 abortions affected 9/30 (30.0%) and 18/316 (5.7%) of the pregnant mares on Farms 1 and 2, respectively; there were also 25 (7.9%) non-EHV abortions on Farm 2. Epizootic differences included: durations (Farm 1 = 135 days; Farm 2 = 34 days), intervals between first and subsequent abortions (Farm 1 = 39 days; Farm 2 = 2 days) and intervals to confirmation of EHV-1 (Farm 1 = 40 days; Farm 2 = 2 days). The median (range) age of EHV-1 abortion mares (8.0; 5-18 years) in both epizootics was similar but significantly younger (P = 0.004) than the 25 non-EHV-1 abortion mares (11.0; 4-24 years) on Farm 2. Gestation stage (median; range) of EHV-1 (291.5; 277-313) and non-EHV-1 (211.9; 61-339 days) abortions were significantly different (P = 0.001). The post abortion complications and subsequent reproductive outcomes had no significant association with EHV-1 abortion.

CONCLUSIONS

The marked difference in morbidity between the 2 epizootics may be associated with routes of introduction or intervention strategy dictated by availability of molecular diagnostic techniques. Unexpectedly, EHV-1 was not more commonly associated with post abortion complications.

The effect of consignment to broodmare sales on physiological stress measured by faecal glucocorticoid metabolites in pregnant Thoroughbred mares

BACKGROUND

Validation of a method for the minimally-invasive measurement of physiological stress will help understanding of risk factors that may contribute to stress-associated events including recrudescence of Equid herpesvirus (EHV), which is anecdotally associated with sales consignment of pregnant Thoroughbred mares. In this study we compared two similar groups of late-gestation Thoroughbred broodmares on the same farm: a consigned Sales group (N = 8) and a non-consigned Control group (N = 6). The Sales mares were separated from their paddock companions and grouped prior to their preparation for, transport to, and return from the sales venue. Both groups were monitored by sampling at regular intervals from 5 days prior to until 14 days after the sales date (D0) to measure physiological stress in terms of changes in faecal glucocorticoid metabolite (FGM) concentrations, and for event-related viral recrudescence via daily body temperature measurements and periodic nasal swabs for PCR analysis for EHV-1 and -4 DNA.

RESULTS

In both groups, FGM levels increased post-sales before returning to pre-sales levels. Specifically, FGM concentrations in the Sales mares were significantly higher on D + 3 and D + 10 than on D-4 and D-3 (F = 12.03, P < 0.0001, Post hoc: P = 0.0003-0.0008) and in the Control group FGM concentrations were higher on D + 10 than D-4 (F = 5.52, P = 0.004, Post hoc: P = 0.005). Interestingly, mean FGM levels in Control mares were significantly higher at 4 of the 5 sampling points (t = 5.64-2.25, p = 0.0001-0.044). Only one (Sales) mare showed PCR evidence of EHV-1 shedding.

CONCLUSIONS

Using FGM to measure physiological stress was supported by the increases observed in all mares after Sales consignment, including those not consigned to the sale. Monitoring FGM levels therefore represents an appropriate, minimally-invasive method for future studies to assess the contribution of physiological stress to EHV recrudescence in horses transported to sales or equestrian events.

Systemic infection induced by intranasal inoculation of Bovine herpesvirus 1.1 in pregnant and non-pregnant rabbits

Bovine herpesvirus (BoHV) type 1.1 (BoHV-1.1) causes repeated outbreaks of upper respiratory disease and abortion in cattle. The systemic effects of BoHV-1.1 in rabbits, using intranasal inoculation are reported. Female rabbits were divided into four groups and inoculated with the virus 10 days before mating, and at 15 or 22 days of pregnancy. Studies of the clinical signs, antibody production, virus isolation, and DNA detection as well as histological and immunohistochemical studies were carried out on lungs, kidneys, spleen, placentas, uteri and foetal tissues. All virus-inoculated animals developed respiratory clinical signs and a humoral response. BoHV-1.1 was isolated from nasal swabs and plasma rich in leukocytes, and viral DNA was detected in blood, dead foetuses and placentas. Histopathological lesions were found in the respiratory tract and some placentas and foetuses were immunohistochemically positive. Intranasal inoculation might be useful to study the systemic effects of BoHV-1.1 infection in the rabbit model.

Bovine herpesvirus 1 abortion: current prevalence in the United Kingdom and evidence of hematogenous spread within the fetus in natural cases

While Bovine herpesvirus 1 (BoHV-1) has been known as a cause of bovine abortion for nearly 50 years, information is limited on the current prevalence of BoHV-1 abortion in the United Kingdom, or about the mode of virus dissemination to cause infection of the fetus. The present study aimed to investigate these issues by surveying the prevalence of BoHV-1 in abortion cases in the United Kingdom, and comparing diagnostic methods to determine which are most efficient in BoHV-1-induced abortion. Where BoHV-1 DNA was detected, viral load was compared in fetal tissues, using real-time polymerase chain reaction (PCR), supported by histopathology and immunohistochemistry (IHC) to investigate virus dissemination in bovine abortions. A total of 400 U.K. bovine abortion cases were studied; PCR detected BoHV-1 nucleic acids in 10 cases, suggestive histopathological lesions were observed in 8, and positive IHC staining was observed in 9. In routine diagnosis, BoHV-1 was identified in 2 of these cases, highlighting the utility of using molecular diagnostic tests such as real-time PCR to achieve high sensitivity in potentially autolyzed tissues. The study of different fetal samples showed the highest viral load in the liver, along with severe multifocal necrotic hepatitis, suggesting either a clear tropism of the virus for this organ or that it is the first location to be reached in the fetus. Presence of viral antigen in endothelial cells of the placenta, brain, or heart suggest a hematogenous spread of virus from placenta to the liver, through the umbilical vein, and then to the rest of the organs via fetal blood vessels.

A serologic study of canine herpes virus-1 infection in the Norwegian adult dog population

Canine herpes virus-1 (CHV1) causes a fatal hemorrhagic disease in neonatal puppies and is associated with reproductive problems in female dogs. This serologic study was conducted to assess the seroprevalence of CHV1 infection in Norway. Blood samples were collected from clinically healthy dogs (n = 436) one yr of age and older of both genders, supplied by four small animal clinics (A, B, C and D) in different parts of the country. The immunoperoxidase monolayer assay was used for testing of CHV1 antibodies. Serum titers were recorded as the reciprocal value of the highest dilution producing specific cell staining. Titers equal to or above 80 were considered positive for exposure to CHV1. In total, 80.0% of the dogs had titers ≥80 and were classified as positive. Mean age for seronegative dogs was 4.7 yrs (95% CI 4.1-5.4) and for seropositive dogs 5.0 yrs (95% CI 4.7-5.4). Of the dogs, 32.8% displayed a weakly positive titer of 80, whereas 41.5 and 5.7% fell into the moderately (titer 160 and 320) and strongly (titer ≥640) positive categories, respectively. No association was demonstrated when comparing CHV1 antibody titers to gender or reproductive parameters like previous matings, pregnancies, births or number of puppies born. Age, visit in foreign countries and clinic explained together 78% of the variation in antibody titer categories. The percentage of positive samples differed significantly between the four clinics (A 98%, B 58.5%, C 74.6%, D 89.5%). A reasonable explanation for this finding has not been established. No information about an ongoing outbreak of CHV1 infection was available. In conclusion, this study strongly indicates that CHV1 infection is endemic in the dog population of Norway. There are significant differences in seroprevalence between geographic regions in the country.

Molecular data of UL24 homolog gene (ORF37) from Brazilian isolates of equine herpesvirus type 1

Equine herpesvirus type 1 (EHV-1) is associated with abortions, respiratory distress, and neurological disturbances in horses. The ORF37 of EHV-1 encodes a protein homolog to UL24 gene product of human herpesvirus that has been associated with neurovirulence. In the present work, ORF37 PCR fragments derived from two Brazilian EHV-1 isolates, a German isolate and an American reference strain were sequenced and characterized by molecular phylogenetic analysis. This genomic region is highly conserved an allowed to infer genetic distances between EHV-1 strains and other animal herpesvirus.

Symptomless intrauterine transmission of bovine herpesvirus 4 to bovine fetuses

Blood samples of 31 healthy calves and their dams taken immediately after calving before colostrum uptake, and at days 11, 23 and 8 weeks, spleens of seven stillborn calves were analysed in order to determine the source and time of bovine herpesvirus type 4 infection. All the calves were born as seronegatives, while all cattle were seropositives. Viral DNA were amplified by a nested PCR assay from 54.8% of peripheral blood leukocyte samples of newborn calves taken before colostrum uptake, and from all cattle and from their colostrums. Real time PCR detected higher virus level in peripheral blood leukocytes in adult cattle, then in their newborn calves. Bovine semen cells (spermatozoa and leukocyte fractions), spleens of stillborn calves also carried viral genomes. Our results prove, that bovine fetuses can be infected in utero by BoHV-4, but are born as seronegatives. After human examples this is the first report in veterinary virology on intrauterine transmission of a herpesvirus without acute consequences. This phenomenon could explain the low antigenicity of BoHV-4 proteins and lack of neutralizating antibodies. BoHV-4, a gammaherpesvirus, could serve as an animal model for studying inapparent herpesviral infections of human fetuses.

Effects of equine herpesvirus-9 infection in pregnant mice and hamsters

The pathogenicity of equine herpesvirus (EHV)-9, a new neurotropic equine herpesvirus isolated from gazelles, was assessed in pregnant rodents (mice and hamsters) following intranasal inoculation. The pregnant female mice and hamsters were inoculated with EHV-9 in the early or late trimesters. The inoculated animals exhibited mild to severe neurological signs and gave birth to dead or undersized fetuses. All three mice and four hamsters inoculated in the first trimester had varying degrees of placental abnormality, characterized by markedly dilated maternal blood sinusoids, atrophy of the trophoblast cells and necrosis of the middle layer of the trophoblast. There was also endometrial blood vessel congestion and necrosis and disorganization of the fetal capillaries in the mice and hamsters inoculated in the last trimester. EHV-9 antigen was detected in the brain of dams and the lungs of the fetuses and in the middle of the trophoblast layer of the placenta in hamsters inoculated in the first trimester. The placental lesions were milder in mice than in the hamsters. The mice and hamsters inoculated in the last trimester had more prominent lesions than the animals inoculated in the first trimester. These results suggest that EHV-9 can cause the death of the fetus or abortion and that these events may be secondary to placental vascular compromise.

Ultrasonographically documented early pregnancy loss in an Asian elephant (Elephas maximus)

Early embryonic resorption or fetal loss is known to occur occasionally in captive elephants; however, this has mostly been reported anecdotally. The present study documents the case of a 24-year-old, multiparous Asian elephant cow that suffered embryonic death and resorption at around 18 weeks of gestation. From ovulation onwards, this female was sonographically examined 58 times. Blood was collected twice weekly for progestagen determination via enzyme immunoassay. On Day 42 after ovulation, a small quantity of fluid was detected in the uterine horn, which typically indicates the presence of a developing conceptus. Repeated inspections followed what appeared to be a normal pregnancy until Day 116. However, on Day 124, signs of embryonic life were absent. Progestagen concentrations started declining two weeks later, reaching baseline levels one month after embryonic death. Retrospectively, ultrasound examination revealed several abnormalities in the uterine horn. Besides an existing leiomyoma, multiple small cystic structures had formed in the endometrium at the implantation site and later in the placenta. These pathological findings were considered as possible contributors to the early pregnancy failure. PCR for endotheliotropic elephant herpes virus (EEHV) (which had occurred previously in the herd) as well as serology for other infectious organisms known to cause abortion in domestic animals did not yield any positive results. Although no definitive reason was found for this pregnancy to abort, this ultrasonographically and endocrinologically documented study of an early pregnancy loss provides important insights into the resorption process in Asian elephants.

Serological evidence of canine herpesvirus-1 in dogs of Kerman city, south-east of Iran

Canine herpes virus-1 (CHV-1) is an alphaherpesvirus, which causes foetal and neonatal death as well as fertility problems in dogs. The virus is presumed to be enzootic in dogs all over the world, but no information was found about the seroprevalence of CHV-1 from middle-east countries. Therefore, this study was aimed to determine the seroprevalence of CHV-1 among dogs in Kerman (south-east of Iran). Blood samples were taken from 47 privately owned and 35 kennelled dogs, respectively. The entire sampled dogs were apparently healthy. Indirect immunofluorescence antibody (IFA) assay was used to detect antibodies against CHV-1 in all sera. The overall CHV-1 seroprevalence was estimated 20.7%, which was 22.9% and 19.1% for kennelled and owned dogs, respectively. Sex, parity and raising status (owned or kennels) did not differ significantly between seropositive and seronegative dogs. However, the infection rate was significantly higher in dogs older than 3 in comparison with younger groups (15.9% vs. 4.8%, P ≤ 0.05). In conclusion, this study revealed that CHV-1 could be considered endemic in Iran, and more epidemiological researches are needed to identify the geographical distribution of diseases in Iran.

Effects of bovine Herpesvirus Type 5 on development of in vitro-produced bovine embryos

Bovine (Bos indicus) herpesviruses have been associated with reproductive disease. Type 1, the most studied species, is best known for its reproductive and respiratory effects. Type 5 (BoHV-5) has been detected in bull semen and aborted fetuses but not in oocytes and embryos. This study consisted of three experiments that evaluated (1) BoHV-5-infected oocytes matured in medium with fetal bovine serum (BoHV-FBS) or polyvinyl alcohol (BoHV-PVA) and fertilized by noninfected sperm; (2) noninfected oocytes fertilized by BoHV-5-infected sperm; and (3) infection of presumptive zygotes by BoHV-5. Each treatment involved nine drops of 15 to 20 oocytes. Infection with BoHV-5 was detected by polymerase chain reaction and in situ hybridization assay, and fertilization capacity and embryonic development were assessed using in vitro culture. Experimentally induced infection was obtained in all experiments, and vertical transmission of BoHV-5 by gametes was confirmed. The cleavage rate was reduced (P=0.0201) in BoHV-FBS (80.4+/-8.9%; mean+/-SD) compared with that of noninfected oocytes (89.9+/-6.5%); neither differed from BoHV-PVA (87.3+/-7.1%), and the resulting embryo production rate was not significantly different among groups. Rates of cleavage (87.5+/-7.5% vs. 92.2+/-5.5%, control vs. infected) and development of embryos (41.7+/-9.9% vs. 44.3+/-7.7% to morula/blastocyst/expanded blastocyst [M/B/EB] and 39.6+/-10.3% vs. 40.8+/-9.2% to blastocyst/expanded blastocyst/hatching blastocyst [B/EB/HB] stages) were not compromised by infected sperm (P=0.1462, P=0.5402, and P=0.8074, respectively). However, presumptive zygotes directly infected 1 d after fertilization produced a lower number (P=0.0140 to M/B/EB and P=0.002 to B/EB/HB stages) of in vitro-produced embryos (31.6+/-4.6 vs. 25.0+/-5.5 and 31.6+/-4.6 vs. 20.2+/-5.4; control vs. infected). In conclusion, BoHV-5 infected gametes and was transmissible to the embryo during in vitro development. As zygotes infected 1 d after fertilization had compromised development, BoHV-5 has the potential to be a pathogen with economic consequences.

Equine gammaherpesviruses: pathogenesis, epidemiology and diagnosis

Equine gammaherpesviruses (γEHV) have been widely studied over the past 45 years and many isolates have been characterised. Despite this, the diagnosis of γEHV infection remains difficult to establish as its clinical manifestations lack specificity, ranging from mild respiratory signs in a small number of animals to outbreaks in large groups of young horses. This review focuses on the epidemiology, pathogenesis, clinical manifestations and diagnosis of equine herpesvirus (EHV)-2 and -5 infections, as well as on the genetic variation of these viruses. Study of these variations has resulted in hypotheses relating to viral re-infection and re-activation. Interestingly, the viruses were found to contain genetic sequences identical to those of eukaryotic cells which are considered central to the development of viral latency through interfering with host immune and inflammatory responses. Future molecular biological studies will further elucidate the virulence mechanisms of these equine pathogens.

Cervid herpesvirus 2 experimentally reactivated in reindeer can produce generalized viremia and abortion

Cervid herpesvirus 2 (CvHV2) has never been isolated from reindeer in Norway, but serological data and investigations by PCR indicate that the virus is endemic in the country, with horizontal and vertical transmission, systemic spread, and latency in the trigeminal ganglion. In this study two seropositive reindeer, one of which was pregnant, were administered dexamethasone, to reactivate CvHV2 latent infection. One control animal received sterile water. All animals including the control reactivated, as shown by amplification of CvHV2 DNA from nasal swabs. The pregnant animal showed lesions in the lip mucosa 10 days after the first dexamethasone injection and CvHV2 was visualized by electron microscopy and isolated from those lesions, as well as from nasal and vaginal swabs. On day 13 she aborted and CvHV2 was isolated from both the aborted calf and the mother. CvHV2 was isolated from the other animal administered dexamethasone. Despite amplification of viral DNA in the control animal, it was never possible to isolate the virus. Molecular characterization of the new isolates confirmed these to be CvHV2, and similar to the previous known strain Salla82. Present results represent the first isolation of CvHV2 in Norway and reconfirm that this virus can cause systemic infections in reindeer even after reactivation episodes, and infect the fetus in utero despite a prompt immune response. While it is not possible to atribute the abortion to CvHV2 alone, present data together with previous reports of vertical transmission of CvHV2 and neonatal death, point to an abortogenic potential, which should be further investigated.

Alphaherpesvirus infections in semidomesticated reindeer: a cross-sectional serological study

Alphaherpesviruses infect a wide range of animal species and cause diseases. Cervid herpesvirus 2 (CvHV-2) was originally isolated from reindeer in Finland but the impact of CvHV-2 infections on reindeer remains unclear. CvHV-2 infection could be partly responsible for calf losses as there are indications that it is associated with abortions and neonatal diseases. Previous serosurveys of reindeer (Rangifer tarandus tarandus) have shown that an alphaherpesvirus is circulating among reindeer in Norway. The aim of the present study was to determine the prevalence of CvHV-2 infection among reindeer in various herding districts in Finnmark, the largest reindeer area in Norway, and to identify factors associated with becoming infected with CvHV-2. A total of 3062 serum samples were tested using an ELISA and a sub-set of samples was further tested using a seroneutralization test. The ELISA revealed that 49% of samples were positive. Extrapolation of the results to the total population (111,350 animals; 66% of the Finnmark reindeer population) showed that the seroprevalence in the population was 48%. Seroprevalence varied from 7.6% to 90.7% between districts and was affected by age, weight and population density. ELISA-positive samples neutralized CvHV-2 at serum dilutions greater than those required for neutralization of bovine herpesvirus type 1. It is concluded that CvHV-2 is endemic throughout the reindeer herding districts of northern Norway.

Cervid herpesvirus 2 causes respiratory and fetal infections in semidomesticated reindeer

Members of the viral subfamily Alphaherpesvirinae establish latency from which they can be reactivated. Bovine herpesvirus 1 causes infectious bovine rhinotracheitis and infectious pustular vulvovaginitis in cattle, as well as abortion and weak calves. Serological evidence of alphaherpesvirus infection has been reported for wild and semidomesticated reindeer (Rangifer tarandus tarandus) in Norway. To address the possibility that reindeer alphaherpesvirus (cervid herpesvirus 2 [CvHV-2]) infection might affect the respiratory system and in part explain the relatively high mortality of reindeer calves during their first year, tissue samples were obtained from reindeer and reindeer fetuses at slaughterhouses in Finnmark County, Norway. A nested pan-alphaherpesvirus PCR amplification targeting the highly conserved UL27 gene (encoding glycoprotein B) was used. Sequencing of amplicons revealed the presence of CvHV-2 DNA. The detection of CvHV-2 DNA in trigeminal ganglia (27 of 143 samples), nasal swabs (5 of 75 samples), and fetal tissues (12 of 48 samples) indicates that CvHV-2 infection is endemic in this reindeer population. Moreover, the virus is transmitted horizontally by the respiratory route, establishing latency in the trigeminal ganglion, and vertically to the fetus through the placenta. Further studies should focus on the reproductive impact of CvHV-2 infection in reindeer.

Infectious causes of embryonic and fetal mortality

The purpose of this review is to summarize bacterial, fungal, protozoan, and viral causes of reproductive dysgenesis in cattle, sheep, goats, pigs, horses, dogs, and cats. The clinical presentations of disease due to reproductive pathogens are emphasized, with a focus on assisting development of complete lists of causes that result in abortion and infertility in these species. Clinicians are encouraged to assess clinical presentation, create complete lists of differential diagnoses, obtain appropriate diagnostic samples, maximize diagnostic laboratory support, and avoid zoonotic infections resulting from reproductive pathogens of animals. The foundation of an accurate diagnosis of reproductive loss due to infectious pathogens facilitates the prudent use of immunization and biosecurity to minimize reproductive losses.

Detection of equine herpesviruses in aborted foetuses by consensus PCR

The major role of EHV-1 in equine abortion is widely reported in the literature but the contribution of EHV-2, EHV-3, EHV-4 or EHV-5 remains less well documented. The objective of this study is to evaluate the contribution of these five different EHVs to equine abortion in a variety of biological tissues using a consensus polymerase chain reaction (PCR). The test was validated for specificity and sensitivity in horses before screening specimens from 407 foetuses, stillbirths and premature foals collected over a 2.5-year interval. Positive results obtained with this assay were compared to other EHV type-specific PCR or by sequencing. EHV-1 was identified as the major cause of abortion in French mares (59/407 cases). However, there was evidence to suggest some variation in the potential of EHV-1 strains to induce abortion. Indeed, DNA samples from EHV-2 (in three cases) and EHV-5 (in one case) inferred a role of these viruses in abortion. The presence of viral DNA from EHV-3 or EHV-4 strains was not detected in the specimens studied. The data obtained suggest that the consensus herpesvirus PCR is an efficient screening tool. In association with a specific PCR, the test provides a rapid identification of the type of herpesvirus involved in abortion and is useful for routine diagnostic tests as it allows the identification of herpesviruses other than the EHV-1 strain.

Detection of bovine herpesvirus 4 in aborted bovine placentas

Diagnostic studies on aborted placentas of cattle usually do not determine any reason for abortions. In this paper, five bovine herpesviruses (BoHVs) and some bacteriological agents were investigated by several methods in 33 aborted bovine placentas. Inclusion bodies, PCR and in situ DNA hybridization proved the presence of BoHV-4 DNA in six (18.18%) tested placentas. Positive DNA hybridization signal localized BoHV-4 DNA to placental epithelial cells macrophages and lymphocytes. By destroying epithelial cells and provoking local immune response BoHV-4 infection may inhibit physiological functions of the placenta during gestation. This finding is a further sign that BoHV-4 plays an active role in reproductive disorders of cattle.

Neonatal mortality in puppies due to bacteremia by Streptococcus dysgalactiae subsp. dysgalactiae

We report a case of bacteremia in puppies caused by Streptococcus dysgalactiae subsp. dysgalactiae. Identification was achieved by phenotypic and molecular genetic methods. This is the first report of the recovery of S. dysgalactiae subsp. dysgalactiae from dogs.

Equine herpesviruses 1 (EHV-1) and 4 (EHV-4) – epidemiology, disease and immunoprophylaxis: A brief review

This review concentrates on the epidemiology, latency and pathogenesis of, and the approaches taken to control infection of horses by equine herpesvirus types 1 (EHV-1) and 4 (EHV-4). Although both viruses may cause febrile rhinopneumonitis, EHV-1 is the main cause of abortions, paresis and neonatal foal deaths. The lesion central to these three conditions is necrotising vasculitis and thrombosis resulting from lytic infection of endothelial cells lining blood capillaries. The initiation of infection in these lesions is likely to be by reactivated EHV-1 from latently infected leukocytes. However, host factors responsible for reactivation remain poorly understood. While vaccine development against these important viruses of equines involving classical and modern approaches has been ongoing for over five decades, progress, compared to other alpha herpesviruses of veterinary importance affecting cattle and pigs, has been slow. However recent data with a live temperature sensitive EHV-1 vaccine show promise.

Do calcium-mediated cellular signalling pathways, prostaglandin E2 (PGE2), estrogen or progesterone receptor antagonists, or bacterial endotoxins affect bovine placental function in vitro?

The major objective of this experiment was to determine whether the bovine placenta could be stimulated to secrete progesterone, since the bovine placenta secretes little progesterone when the corpus luteum is functional. Secondly, we wanted to determine whether reported abortifacients or progesterone or estrogen receptor antagonists affected bovine placental prostaglandin secretion. The ovine placenta secretes half of the circulating progesterone at day 90 of pregnancy and PGE2 appears to regulate ovine placental progesterone secretion. Calcium has been reported to regulate placental progesterone secretion in cattle. Diced 186-245-day placental slice explants from six Brahman and six Angus cows were incubated in vitro at 39.5 degrees C under 95% air: 5% CO2 at pH 7.2 in 5 ml of M-199 for 1 h in the absence of treatments and for 4 and 8 h in the presence of treatments. Treatments were: vehicle; R24571; compound 48/80; IP3; PGE2; CaCl2; cyclosporin A; lipopolysaccharide (endotoxin) from Salmonella abortus equi., enteriditis, and typhimurium; monensin; ionomycin; arachidonic acid; mimosine; palmitic acid; progesterone, androstenedione; estradiol-17beta; A23187; RU-486; or MER-25. Jugular and uterine venous plasma and culture media were analyzed for progesterone, PGE2 and PGF2alpha by radioimmunoassay (RIA). Plasma hormone data were analyzed by a One-Way Analysis of Variance (ANOVA). Hormone data in culture media were analyzed for breed and treatment effects by a Factorial Design (2 breeds, 2-range of days, 21 treatments) for ANOVA (2 x 2 x 21). Since hormone data secreted by placental tissue in vitro did not differ (P > or = 0.05) by breed or range of days of pregnancy, data were pooled and analyzed by a One-Way ANOVA. Concentrations of PGE2 in uterine venous blood were two-fold greater (P < or = 0.05) in Angus than Brahman cows. PGE2 and PGF2alpha in vehicle controls increased from 4 to 8h (P < or = 0.05), but not progesterone (P > or = 0.05) Progesterone in culture media treated with RU-486 increased (P < or = 0.05) at 4 and 8 h compared to vehicle controls and was not affected by other treatments (P > or = 0.05). Concentrations of PGE2 in media at 4 and 8 h were lower (P < or = 0.05) when compared to controls except treatment with PGE2 at 4 and 8h and RU-486 at 8h (P > or = 0.05). PGF2alpha was increased (P < or = 0.05) by RU-486 at 8h and no other treatment affected PGF2alpha at 4 or 8 h (P < or = 0.05). In conclusion, modulators of cellular calcium signalling pathways given alone do not affect bovine placental progesterone secretion at the days studied and progesterone receptor-mediated events appear to suppress placental progesterone, PGF2alpha, and PGE2 secretion in cattle. In addition, PGE2 does not appear to regulate bovine placental progesterone secretion when the corpus luteum is functional and bacterial endotoxin does not appear to affect bovine placental secretion of PGF2alpha or PGE2.

Intrapreputial infection of young bulls with bovine herpesvirus type 1.2 (BHV-1.2): acute balanoposthitis, latent infection and detection of viral DNA in regional neural and non-neural tissues 50 days after experimental reactivation

Venereal infection of bulls with bovine herpesvirus type 1.2 (BHV-1.2) may result in acute balanoposthitis followed by the establishment of latent infection, presumably in dorsal root nerve ganglia. We herein report the characterization of the acute and latent infection of young bulls with a Brazilian BHV-1.2 isolate and the investigation of neural and non-neural sites in which viral DNA persists during latent infection, i.e. 110 days after inoculation and 50 days after experimental reactivation. Intrapreputial inoculation of BHV-1.2 isolate SV-56/90 (10(6.5)pfu per animal) resulted in severe balanoposthitis, characterized by redness of the penis and preputial mucosa, coalescent vesicles and fibrinous exsudate in all four infected bulls. Virus shedding was detected in preputial secretions and semen up to days 14 and 13 pi, respectively. Dexamethasone administration at day 60 pi led to reactivation of the infection in all animals, resulting in virus shedding in preputial secretions and/or in semen. At day 50 post-reactivation (pr), the animals were euthanized and regional tissues were collected for PCR and virus isolation. Viral DNA was consistently detected in the dorsal root ganglia of nerves genito-femoral (4/4) and obturator (4/4); frequently in the pudendal (3/4), sciatic (3/4) and rectal caudal nerve ganglia (2/3). In addition, viral DNA was detected in the pelvic sympathetic plexus of one bull and in regional lymph nodes (deep inguinal (2/4); sacral (1/4); medial iliac (1/4)) of two bulls. No infectious virus could be recovered from homogenates of DNA positive tissues, indicating the absence of actively replicating virus. These results demonstrate that BHV-1.2 DNA may persist in several sacral nerve ganglia and in regional lymph nodes as well during latent infection, i.e. 50 days after experimental reactivation. These findings may help in understanding the pathogenesis of acute and latent genital infection by BHV-1.2.

Comparison of methods for the diagnosis of equine herpesvirus type 1 infection

The objective of the investigations was to study the occurrence of the equine herpesvirus type 1 (EHV-1) infection in aborted equine fetuses and in newborn foals and to compare the sensitivity of virus isolation, immunohistochemistry and histology in 101 cases and of fetal serology in 68 cases in the diagnosis of the infection. Out of the 93 aborted equine fetuses and 8 weak foals, 15 (14.9%) (14 fetuses and 1 foal) proved to be EHV-1 infected by immunohistochemical and 13 (12.9%) by virological investigation. Characteristic microscopic changes were seen in several organs in all cases, while intranuclear inclusion bodies could be found only in 25 (35.2%) of the 71 virus-positive tissue samples. Four (5.9%) cases proved to be positive by fetal serological investigation, but none of these cases showed any EHV-1 specific lesions and in none of these cases could the virus be detected by virus isolation or by immunohistochemistry. According to the results, fetal serology does not seem to be a useful test in virus-positive cases, while the immunohistochemical method seems to be a reliable and a slightly more sensitive method than virus isolation in the diagnosis of EHV-1 infection.

Detection and isolation of equine herpesviruses 1 and 4 from horses in Normandy: an autopsy study of tissue distribution in relation to vaccination status

Equine herpesviruses type 1 and 4 (EHV-1 and EHV-4) are ubiquitous in the equine population. One of their main properties is their ability to establish life-long latent infections in their hosts even in those with natural or vaccine-induced immunity. However, effect of vaccination status on prevalence and tissue tropism was not established. In this study, EHV-1 and EHV-4 were detected by polymerase chain reaction and by classical virus isolation from neural, epithelial and lymphoid tissues collected from unvaccinated (33) or vaccinated (23) horses. The percentage of EHV-1- and EHV-4-positive horses between vaccinates and unvaccinates was similar. Both viruses were detected in all tissues of both groups; in particular, lymph nodes draining the respiratory tract, nasal epithelium and nervous ganglia [i.e. trigeminal ganglia (TG)], which represent the main positive sites for EHV-1 and EHV-4. In vaccinated animals, the nervous ganglia (i.e. TG) were less frequently positive than in unvaccinated animals. Detection of positive TG was strongly correlated to the presence of EHV-1 in nasal epithelium.

Equid herpesvirus 1 is neurotropic in mice, but latency from which infectious virus can be reactivated does not occur

Equid herpesvirus 1 (EHV-1) is the most common cause of virus-induced abortion in horses. After primary infection the virus becomes latent predominantly in the respiratory tract lymph nodes and the genome can also be detected in the peripheral nervous system. The role of mouse as a feasible model for the establishment of latency and reactivation of EHV-1 was investigated. Intracerebral and intranasal infections of 3- and 17-day-old mice were made and virus replication was confirmed by virus isolation and detected by indirect immunofluorescence (IIF) in brain. For reactivation studies, the mice were killed 8 weeks post infection and tissues were collected for cocultivation. In mice from both age groups, infectious virus was not detected by cocultivation. Following attempts to reactivate virus in vivo with corticosteroids, the viral antigen was detected at low levels by IIF and the expression of the gB gene by reverse transcription polymerase chain reaction (RT-PCR) in brain, trigeminal ganglia, olfactory lobe, lung and spleen. Virus was also detected by IIF following incubation of tissue explants in the growth medium containing pokeweed mitogen (PWM). These results show the limitations of the mouse model for investigating EHV-1 latency and highlights the issue of 'ineffective reactivation' of virus.

Intravitreal injection of the attenuated pseudorabies virus PRV Bartha results in infection of the hamster suprachiasmatic nucleus only by retrograde transsynaptic transport via autonomic circuits

Intravitreal injection of the attenuated strain of pseudorabies virus (PRV Bartha) results in transneuronal spread of virus to a restricted set of central nuclei in the rat and mouse. We examined the pattern of central infection in the golden hamster after intravitreal inoculation with a recombinant strain of PRV Bartha constructed to express enhanced green fluorescent protein (PRV 152). Neurons in a subset of retinorecipient nuclei [i.e., suprachiasmatic nucleus (SCN), intergeniculate leaflet, olivary pretectal nucleus (OPN), and lateral terminal nucleus] and autonomic nuclei [i.e., paraventricular hypothalamic nucleus and Edinger-Westphal nucleus (EW)] are labeled by late stages of infection. Infection of the EW precedes infection in retinorecipient structures, raising the possibility that the SCN becomes infected by retrograde transsynaptic infection via autonomic (i.e., EW) circuits. We tested this hypothesis in two ways: (1) by removing the infected eye 24 hr after PRV 152 inoculation, well before viral infection first appears in the SCN; and (2) by examining central infection after intravitreal PRV 152 injection in animals with ablation of the EW. The pattern and time course of central infection were unchanged after enucleation, whereas EW ablation before intravitreal inoculation eliminated viral infection in the SCN. The results of EW lesions along with known connections between EW, OPN, and SCN indicate that intravitreal injection of PRV Bartha produces a retrograde infection of the autonomic innervation of the eye, which subsequently labels a restricted set of retinorecipient nuclei via retrograde trans-synaptic infection. These results, taken together with other genetic data, indicate that the mutations in PRV Bartha render the virus incapable of anterograde transport. PRV Bartha is thus a retrograde transsynaptic marker in the CNS.

A study of the pathogenesis of equid herpesvirus-1 (EHV-1) abortion by DNA in-situ hybridization

The polymerase chain reaction and DNA in-situ hybridization were used to study sections of uterine tissue collected from mares near the time of abortion due to equid herpesvirus-1 (EHV-1) infection. These techniques revealed viral nucleic acids in endothelial cells of endometrial arterioles, in accordance with previously published immunohistological data. In addition, however, they revealed nucleic acids in cellular debris within endometrial glands and diffusing across the placenta at sites of microcotyledonary infarction. Perivascular leucocytes were generally negative for viral DNA, despite marked perivascular cuffing. These data provided further support for the central role of the vascular endothelial cell in the pathogenesis of EHV-1 abortion and demonstrated direct transplacental spread of nucleic acids at sites of microcotyledonary infarction and across the endometrial glands in the vicinity of vascular lesions.