首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 46 毫秒
1.
From the point of view of disease risk, the movement of livestock by embryo transfer is undoubtedly much safer for trading than the movement of live animals or semen. Nevertheless, strict governmental control by veterinary certification of health of embryos is still vital. In cattle, sheep and pigs, unlike laboratory species such as the mouse, infectious agents do not appear to pass through the zona pellucida (ZP) into the embryo proper. Some agents do, however, adhere firmly to the outer surface of the ZP, especially onto those of the pig. Disease risks associated with the inadvertent transmission of infectious agents when embryos are moved are, therefore, intimately connected with the nature and properties of the ZP. This article reviews current knowledge on the physical and adhesive properties of the ZP and discusses how risks associated with the possible presence of infection on its surface can be minimized. Further research is urgently needed so that realistic but safe veterinary certification of the health of embryos for international trade can be devised.  相似文献   

2.
The objective of this study was to investigate the susceptibility of in vivo- and in vitro-produced (IVP) porcine embryos to classical swine fever virus (CSFV). IVP zona pellucida (ZP)-intact porcine embryos (n = 721) were co-cultured with CSFV for 120 h. After washing according to the International Embryo Transfer Society guidelines (without trypsin) and transferring embryos to CSFV-susceptible porcine kidney cells (PK15 cell line), no virus was isolated. However, when 88 IVP ZP-intact porcine embryos were co-cultured with CSFV for only 48 h before being transferred to PK15 cells, virus was isolated in three of six replicates. Similarly, 603 in vivo-produced porcine embryos were co-cultured with CSFV for 120 h. Subsequently, CSFV was isolated in eight of 50 groups (16%) and the ability of these to form a blastocyst was significantly reduced when compared with the control group (68.2 +/- 19.9% vs 81.9 +/- 9.7%; p < or = 0.001). In contrast, the development of CSFV-exposed IVP porcine embryos was not affected when compared with control embryos (19.1 +/- 10.8% vs 18.9 +/- 10.6%; p > or = 0.05). After removal of the ZP of IVP embryos and subsequent co-culture with CSFV, the virus was isolated from all groups of embryos. These data suggest that virus replication had occurred in the embryonic cells. In conclusion, data indicate that in vivo- and in vitro-produced ZP-intact porcine embryos differ in their susceptibility to CSFV. Hatched or micro-manipulated embryos may increase the risk of transmission of CSFV by embryo transfer, which has to be confirmed by in vivo tests under isolation conditions.  相似文献   

3.
The current, generally accepted approach to formulating health requirements for the international movement of embryos is to base them on the health status of the male and female donor animals. The alternative approach of basing them on the health status of the embryos themselves has been blocked by the lack of scientific information about the potential of the early embryo to transmit agents of infectious disease. Consequently, most research into infectious disease transmission by embryos has had the objective of assessing the potential of the embryo to transmit infectious disease, at the stage of development at which it is transferred commercially, with the thought in mind that, for some diseases, it may be possible in the future to focus on the embryo rather than the donor when drawing up health requirements for import permits. Results from experiments involving the bovine leukemia virus, bluetongue virus, infectious bovine rhinotracheitis virus, foot and mouth disease virus and Brucella abortus are encouraging to the point where, with the exception of foot and mouth disease virus, they could and should be put to the test in field studies. Research on several other bovine pathogens is underway, but the studies are not sufficiently advanced for a judgement to be made on the potential of embryos to transmit them. There is evidence that the research done is starting to have a positive effect through the relaxation of some health requirements for the international movement of embryos.  相似文献   

4.
This review of the general epidemiological aspects of embryo transfer indicates that the transfer of embryos provides the opportunity to introduce genetic material into populations of livestock while greatly reducing the risk for transmission of infectious diseases. Studies of specific diseases of livestock confirm that many pathogens are likely to be excluded when embryos are transferred. Twenty years of commercial embryo transfer under field conditions in a variety of species has not resulted in a single documented transmission of an infectious disease agent. Strategies for insuring that embryos are free of pathogens include the use of donors that are specific pathogen-free, washing of embryos, the trypsin treatment of embryos, or a combination of these methods. Although researchers continue to develop new procedures for the treatment of embryos to provide an even greater margin of safety, it is clear that existing techniques for the handling and transfer of embryos can be used to limit the spread of infectious diseases.  相似文献   

5.
Transfer and low temperature storage of embryos are now proven techniques for a number of mammalian species. These techniques are useful in control of disease and in saving genotypes from infected animals. The place of embryos in the epidemiology of disease depends upon whether the causative organism can gain entry to the oocyte before or at fertilisation and on whether the young embryo can be invaded by organisms in the uterine environment. There is little evidence that important live-stock diseases are transmitted via gametes. The zona pellucida surrounding the embryo is an effective barrier against a number of important disease organisms; in some cases the embryo is susceptible once it has hatched from the zona pellucida. It is important therefore in considering the use of embryos in disease control, to ensure that virus is not attached to the surface of the zona pellucida from where it can infect the recipient and/or the embryo after hatching. Washing procedures have been devised together with the use of enzymes and antisera to remove virus from the surface of embryos. Some viruses enter pores and sperm tracks in the zona and removal of these may present a problem. African swine fever virus has been shown to resist removal by treatment with enzymes. There are no guidelines as to the likely interaction between a certain virus and embryos. Therefore each virus of interest must be tested to determine whether it can be transmitted via washed embryos. Nevertheless there are numerous instances of the use of embryo transfer to eradicate a specific disease or to save valuable genetic material from infected animals without transmitting disease.  相似文献   

6.
Infection with bovine herpesvirus‐1 (BHV‐1), also called infectious bovine rhinotracheitis/infectious pustular vulvovaginitis virus, is associated with a variety of respiratory, neurological and infertility health problems causing worldwide economic losses and trading restrictions to the livestock industry. Although there is a considerable amount of information about the risk of BHV‐1 transmission through contaminated semen used for artificial insemination, there is no available evidence to indicate whether the resulting embryos, when used for embryo transfer (ET), can lead to the transmission of BHV‐1 to recipients and offspring. For this study, cryopreserved bull semen contaminated with BHV‐1 was used for artificial insemination (AI) of seronegative, superovulated heifers (N = 43). Embryos were collected post‐mortem at 7 days post‐insemination and were washed according to the International Embryo Transfer Society (IETS) guidelines. BHV‐1 was detected in all samples of follicular fluid, oviductal epithelial cells, endometrium and corpora lutea tissues and a proportion of unwashed (52 of 120, 43%) and washed oocytes and embryos (7 of 113, 6%) collected from embryo donors. Of the 396 collected, unfertilized oocytes and embryos, only 29 (7%) were of ET quality. Most of the embryos and oocytes were degenerated (N = 224, 57%) or unfertilized (N = 143, 36%). The 13 heifers, which each received a single morula‐stage washed embryo, maintained seronegative status, but only two (15%) became pregnant and delivered BHV‐1‐free calves. In conclusion, results suggest that embryos fertilized with BHV‐1‐contaminated semen may not result in disease transmission to embryo recipients or their offspring when embryos are processed according to IETS and the World Organization for Animal Health (OIE) guidelines. However, due to the transmission of BHV‐1 via AI to embryo donors and the apparent adverse effect of BHV‐1 on the quality of the embryos, it is unlikely that the procedure can be justified for a commercial application.  相似文献   

7.
The objective of the present study was to assess whether bovine herpesvirus 4 (BHV-4) is able to infect in vitro-produced bovine embryos. A green recombinant BHV-4 (BHV-4EGFPTK), obtained by insertion of an EGFP gene into the TK locus of BHV-4, was used. The presence of this marker protein made it possible easily to detect infected cells under physiological conditions, without harmful manipulation of the cells or the addition of exogenous substrates, so that the spread of the virus could be followed in real time. Zona pellucida intact (ZP-I) and zona pellucida open (ZP-O) blastocytes were exposed to 106 TCID50 viral particles and infection was monitored by fluorescent microscopy for 48 h. Expression of EGFP and degeneration of embryonic cells was observed in three of the 18 ZP-O embryos, but in none of the ZP-I embryos. It was concluded from this preliminary study that BHV-4 has only a low ability to infect in vitro-produced bovine embryos, depending on the absence of ZP, the amount of virus present and the stage of embryonic development. However, embryonic stem cells could be transduced by BHV-4EGFPTK just after differentiation, as shown by expression of EGFP.  相似文献   

8.
The association of Leptospira borgpetersenii serovar hardjo type hardjobovis with bovine embryos produced by in vitro fertilization was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Morula stage embryos with an intact zona pellucida (ZP) were exposed to this spirochete for 24 h in culture medium, washed by the standard washing procedure as recommended by the International Embryo Transfer Society, and then examined. SEM showed typical helicoid leptospires on the surface and in the pores of the ZP. TEM showed cross and longitudinal sections of leptospires in the matrix and channels of the ZP, in the perivitelline and intercellular spaces, on the vitellus and in the embryonic cells. Some of the embryos that were penetrated showed damage to the membranes and the cytoplasm. The ineffectiveness of the washing procedure, for the removal of hardjobovis from exposed embryos may be of importance to the industry.  相似文献   

9.
  相似文献   

10.
The in vitro effect of bovine viral diarrhea virus (BVDV) on the survival of day 7 to day 7.5 bovine embryos collected from superovulated donors was studied. Fifty-four experimental embryos with the zona pellucida (ZP) intact, damaged or removed were exposed to 1×104 TCD50/ml of the NADL cytopathic strain of BVDC at 37°C for 24 hrs and compared to 36 control embryos that were cultured for 24 hr. Seven embryos with the ZP-removed were similarly exposed for 48 hrs and compared to five control embryos. The overall survival rate was 68% for embryos exposed to BVDV for 24 hrs and 77% for embryos not exposed (P>0.05). Extended exposure of the embryos with the ZP removed to virus for 48 hrs did not affect their survival rate compared to controls. Damage to the ZP by cracking or total removal of the ZP by micromanipulation or acidic Tyrode's solution had no effect on subsequent embryonic survival in the presence of BVDV. It was concluded that exposure to BVDV in vitro is not cytopathic for morula and blastocyst stage bovine embryos over a 48 hr period, even when they are not protected by the ZP.  相似文献   

11.
The standard washing and trypsin treatment procedures to remove viruses adhering to the zona pellucida (ZP) were evaluated. Mouse embryos at the early blastocyst stage were exposed to Sendai virus, and then washed or treated with trypsin. Even after washing or trypsin treatment, Sendai virus was detected in the twelfth and final wash. The virus was still shown to adhere to the ZP by immunofluorescence assay. The embryos developed into expanded blastocysts following 24 hours of in vitro culture. Viral antigen was clearly demonstrated in the cells forming the expanded blastocysts, indicating that viral replication occurred in these cells. The present results suggest that the standard washing or trypsin treatment are not sufficient to remove Sendai virus adhering to the ZP of mouse embryos.  相似文献   

12.
During pregnancy infections can entail disorders in many different ways. Damage through direct transmission of pathogens to the fetus occurs in the first place. The organisms are transmitted transovarially, diaplacentally, via endometrium, before or after implantation, via amnion or by the semen when ascending through the infectious environment. Embryo transfer is a new way of transmission. The respective infective microorganisms either directly colonize in the embryo with the well known consequences (fetotrope pathogens) or they colonize the placenta thus indirectly leading to damages to the embryo (placentotrope pathogens). During the process various overlappings are possible. A second large group of disorders in pregnancy is caused by effects of infections of the mother without pathogens being transmitted to the embryo or the placenta. These diseases are postinfectious allergies, immune complex diseases, damages through microbial toxins or mediators and various other forms of infectious processes found with the mother. The third group of disorders in pregnancy is the result of complications caused by vaccinations of the mother during or shortly before pregnancy: postvaccinal allergies, diseases through vaccinal germs and different other postvaccinal damages or stress because of vaccination.  相似文献   

13.
The aim of this study was to evaluate three different cloning strategies in the domestic cat (Felis silvestris) and to use the most efficient to generate wild felid embryos by interspecific cloning (iSCNT) using Bengal (a hybrid formed by the cross of Felis silvestris and Prionailurus bengalensis) and tiger (Panthera tigris) donor cells. In experiment 1, zona‐free (ZP‐free) cloning resulted in higher fusion and expanded blastocyst rates with respect to zona included cloning techniques that involved fusion or injection of the donor cell. In experiment 2, ZP‐free iSCNT and embryo aggregation (2X) were assessed. Division velocity and blastocyst rates were increased by embryo aggregation in the three species. Despite fewer tiger embryos than Bengal and cat embryos reached the blastocyst stage, Tiger 2X group increased the percentage of blastocysts with respect to Tiger 1X group (3.2% vs 12.1%, respectively). Moreover, blastocyst cell number was almost duplicated in aggregated embryos with respect to non‐aggregated ones within Bengal and tiger groups (278.3 ± 61.9 vs 516.8 ± 103.6 for Bengal 1X and Bengal 2X groups, respectively; 41 vs 220 ± 60 for Tiger 1X and Tiger 2X groups, respectively). OCT4 analysis also revealed that tiger blastocysts had higher proportion of OCT4‐positive cells with respect to Bengal blastocysts and cat intracytoplasmic sperm injection blastocysts. In conclusion, ZP‐free cloning has improved the quality of cat embryos with respect to the other cloning techniques evaluated and was successfully applied in iSCNT complemented with embryo aggregation.  相似文献   

14.
Artificial insemination (AI) is one of the most widely used assisted reproductive technologies in swine. To maintain a healthy semen trade, it is crucial that diligence be given to managing and minimizing the chance of extended semen playing an epidemiological role in the transmission of infectious disease. In swine, pathogens of primary importance, which may be transmitted through semen include Aujeszky's disease, brucellosis, chlamydophilosis, porcine circovirus type 2, classical swine fever, Japanese encephalitis, leptospirosis, parvovirus, porcine reproductive and respiratory syndrome, rubulavirus, foot-and-mouth disease and swine vesicular disease. This paper will summarise the current state of knowledge pertaining to these pathogens in relation to swine AI.  相似文献   

15.
Strongyloides and other soil‐transmitted helminths represent a severely under‐recognized zoonotic public health risk, especially in North American cities. They are present throughout North America, including in urban areas, causing morbidity and mortality in human and non‐human animals. Epidemiological “masking” of strongyloidiasis due to overlapping symptoms with other systemic diseases, including allergies, and diagnostic limitations complicate our understanding of the epidemiological extent of this disease, and auto‐infection allows long‐term persistence of individual infections. Zoonotic transmission and environmental transmission are critical components in the epidemiology of strongyloidiasis, and other diseases caused by soil‐transmitted helminths. In this review, we bring together medical, veterinary and environmental expertise in a “One Health” context, to document and analyse this under‐recognized risk. We also present implementable opportunities for action with respect to diagnostics, treatment, community engagement and land management to mitigate the impact and transmission of strongyloidiasis and other diseases caused by soil‐transmitted helminths.  相似文献   

16.
There seems to be two main types of pathogens that cause diseases in swine: those that are mainly introduced through direct pig contacts, and those that are often, and in some situations mainly introduced by indirect transmission means. In this review, the mange mite (Sarcoptes scabiei), toxigenic Pasteurella multocida and Brachyspira hyodysenteriae will be used as examples of the first type, and foot and mouth disease virus, Mycoplasma hyopneumoniae and porcine reproductive and respiratory syndrome (PRRS) virus as examples of the second. It is now clear from various epidemiological studies as well as experimental and field data that aerosol transmission of some swine pathogens plays an important role in their epidemiology. As previous biosecurity programs did not take this factor into consideration, it can at least partially explain why many of these programs suffered frequent failures and why air filtration is now becoming increasingly popular in North America. Identifying and quantifying transmission means should be a priority for every important infectious disease for which it has not been done.  相似文献   

17.
Preimplantation bovine embryos were exposed in vitro to Brucella abortus to determine if the bacteria would adhere to zona pellucida (ZP)-intact embryos or adhere to or infect ZP-free embryos. Brucella abortus was not isolated from ZP-intact or ZP-free groups of embryos after 10 sequential antibiotic-free washings. Brucella abortus was isolated from all groups containing ZP-defective embryos after the exposure period and washing. Detrimental effects on healthy in vitro development of embryos were not observed.  相似文献   

18.
Contents This paper describes the risk of transmission and possible consequences of viral diseases in pigs (as CSFV, PRRSV and SVD), transmitted via AI and embryo transfer. Transmission via A1 is, however, more unlikely for CSF and SVD than for PRRS. The likelihood of disease transmission is greater with the introduction of a boar into a herd than through the use of fresh or frozen semen. The probability that an infection with CSF or SVD virus starts within an AI centre is very small, because of the high hygienic measurements and quarantine period, although the viruses can be transmitted if these centra are located within a protection zone. Therefore, during an outbreak, it should be recommended to stop semen distribution within this zone.  相似文献   

19.
Zoonotic diseases impact both wild and domestic animal populations and can be transmitted to humans through close contact with animal species. Reservoir species acting as vectors are major traffickers of disease. Rodents contribute to the transmission of Coxiella burnetii although little is known about its prevalence in wild animal populations. DNA was extracted from genital swabs collected from woodland jumping mice, deer mice, Southern red‐backed voles, Eastern chipmunks, North American red squirrels, as well as Southern and Northern flying squirrels collected from Algonquin Park, Canada. The presence of C. burnetii was determined through real‐time PCR. All species sampled had some prevalence of infection, except Eastern chipmunks, indicating wild rodents in Algonquin Park are reservoirs for C. burnetii. Emerging zoonotic diseases are linked to increasing globalization. Contact amongst individuals increases as crowding, habitat loss and fragmentation increase within wild spaces. Parks often act as a last refuge for wildlife but may also be an important transmission zone of wildlife disease to humans. Investigations that attempt to discover wild reservoir species of zoonotic disease are critically important to understanding the risk of pathogen exchange between wild and human populations.  相似文献   

20.
非洲猪瘟是一种急性传染病,不仅发病率较高,死亡率也高,已被列为法定报告动物疾病,是我国重点防控的动物疫病之一。非洲猪瘟的危害性较强,一旦出现会大面积扩散,病情控制的难度较大,会带来难以估量的损失。在养猪中,做好非洲猪瘟的预防工作,充分认识非洲猪瘟的危害性,保障养殖业的发展和消费者的健康。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号