Preventing disease transmission through the transfer of in-vivo-derived bovine embryos

A Review of Ureaplasma diversum: A Representative of the Mollicute Class Associated With Reproductive and Respiratory Disorders in Cattle

The Mollicutes class encompasses wall-less microbes with a reduced genome. They may infect plants, insects, humans, and animals including those on farms and in livestock. Ureaplasma diversum is a mollicute associated with decreased reproduction mainly in the conception rate in cattle, as well as weight loss and decreased quality in milk production. Therefore, U. diversum infection contributes to important economic losses, mainly in large cattle-producing countries such as the United States, China, Brazil, and India. The characteristics of Mollicutes, virulence, and pathogenic variations make it difficult to control their infections. Genomic analysis, prevalence studies, and immunomodulation assays help better understand the pathogenesis of bovine ureaplasma. Here we present the main features of transmission, virulence, immune response, and pathogenesis of U. diversum in bovines.

Emerging diseases in international trade in embryos

A significant change in cattle production and germplasm exchange has occurred over the past 50 years. The growth of artificial reproductive technologies and their broad implementation has become commonplace. The production and subsequent import and export of semen and embryos throughout the world has increased significantly. The embryo transfer industry has reached a new record of growth, with approximately 1.5 million transferrable bovine embryos collected and/or produced in 2018. Over 1 million of these embryos were produced invitro . The increased production of invitro -produced embryos leads to greater opportunities involving international trade. However, further research concerning emerging pathogens is imperative to ensure the efficacy and safety of the embryo transfer industry. Appropriate biosecurity protocols, including reliable testing methodology and effective embryo processing procedures, are key in preventing disease due to emerging and re-emerging pathogens that can be transmitted via embryo transfer.

Caprine arthritis encephalitis: an example of risk assessment for embryo trading

The risk of transmission of caprine arthritis encephalitis virus (CAEV) during embryo transfer has been demonstrated in vivo through the detection of CAEV proviral DNA in: (1) flushing media for embryo collection; (2) cells of the cumulus oophorus surrounding the oocytes, ovarian follicle, oviduct and uterine tissues; and (3) testis, epididymis, vas deferens and vesicular glands. Experimentally infected embryos without a zona pellucida (ZP), washed 10 times with Minimum Essential Media (MEM) and 5% Fetal Calf Serum (FCS) solution, were capable of transmitting CAEV. In vitro we demonstrated that granulosa, oviductal, epididymal and embryo cells are fully susceptible to CAEV infection and allow active replication. However, AI with in vitro-infected semen can result in the production, after ten washing, of CAEV-free embryos, and ten washing in vitro- or in vivo-infected embryos with an intact ZP, or ten washing oocytes with an intact ZP, resulted in the production of virus-free female gametes or embryos that can be used for IVF or embryo transfer. Therefore, we have demonstrated that: (1) that CAEV-free embryos can be produced by IVF using spermatozoa infected in vitro by CAEV; and (2) embryo transfer can be used under field conditions to produce CAEV-free kids from CAEV-infected biological mothers.

Shaping the norms that regulate international commerce of embryos

As various embryo technologies in livestock were developed and evolved to a state of usefulness over the past 40 years, scientists with a specific interest in infectious diseases sought to determine the epidemiologic consequences of movement, especially international movement, of increasing numbers of embryos. Many of the foundational studies in this area were reported in Theriogenology, beginning in the 1970s and especially throughout the 1980s and 1990s. Unquestionably, Theriogenology has been a widely used venue for dissemination of basic information on this subject, which ultimately led to the development of the now universally accepted techniques for certification of embryo health. Today it is well-recognized that movement in commerce of embryos, especially in vivo-derived embryos, is a very low-risk method for exchange of animal germ plasm. This paper chronicles the evolution of strategies for health certification of embryos. An overview is provided of the calculated efforts of practitioners, scientists, and regulators to organize, forge necessary partnerships, stimulate needed research, provide purposeful analysis of the results, and, through these processes, guarantee the universal acceptance of efficient protocols for certifying the health of embryos intended for movement in international commerce.

Relative risks and approaches to biosecurity in the use of embryo technologies in livestock

Embryo technologies have been integrated into production systems for a variety of livestock species. As relates to transmission of infectious diseases, our working hypothesis has been that use of embryo transfer for distribution of germ plasm within and between herds and flocks is likely safer than the movement of postnatal animals. Indeed, research and experience generally have been supportive of this hypothesis. However, the relative risks of transmitting infectious agents via embryo transfer vary among donor species. Further, different methods of producing embryos appear to present different risks. This paper provides a comparative overview of the risks of transmitting infectious diseases via transfer of both in vivo- and in vitro-derived embryos in common domesticated livestock species. Also discussed are universal approaches to biosecurity in embryo production and transfer.

Sanitary control in bovine embryo transfer How far should we go? A review

Embryo transfer is a globally executed technique which, when properly done, has both economic and sanitary advantages. International guidelines are available to prevent infection of the embryo with pathogens, both originating from the donor animals as from the environment. This manuscript describes the bacteria, viruses, protozoa, fungi and prions that are of major concern in the context of embryo transfer in cattle. In addition, the actual scientific knowledge on these pathogens is evaluated in terms of the current international and national guidelines and legislation.

Biosecurity and the various types of embryos transferred

The aim of the present paper was to review some features related to the risk analysis of three types of embryos to be transferred, namely the in vivo derived, the in vitro produced and the cloned ones. For in vivo-collected embryos, a considerable number of experiments and scientific investigations have been performed and hundreds of thousands of embryos are transferred annually with no contamination of associated diseases. Provided that the code of practice such as that published by the International Embryo Transfer Society is strictly followed by the embryo transfer practitioners, the statement made some 17 years ago saying that the in vivo-derived embryo transfer was the safest way of exchanging genes remains entirely true, thanks to the professionalism of the embryo transfer industry. For the in vitro-produced embryos, some particular rules have to be followed because of specific risks for some pathogens to strongly adhere to the zona pellucida of such embryos. There are some means to monitor and control those effects, and the transfer of in vitro-produced embryos can also be a very safe way to exchange genes around the world. The third type of embryos, the cloned ones, is a quite different category and the risk analysis to be soundly made still needs a lot of investigations so as to characterize the potential risks if there are, in terms not only of disease transmission but also in terms of public health, zoonotic risks as well as those related to quality and safety of food. The problem in this regard, is more directly addressed for offspring of clones than to the cloned embryos themselves. Published data on this issue are increasing in numbers so that progress in that area is expected in the few years to come.

Seroconversion of calves following intravenous injection with embryos exposed to bovine viral diarrhea virus (BVDV) in vitro

Two recent studies demonstrated that a high-affinity isolate of BVDV (SD-1), remained associated with a small percentage of in vivo-derived bovine embryos following artificial exposure to the virus and either washing or trypsin treatment. Further, the embryo-associated virus was infective in an in vitro environment. Therefore, the objective of this study was to determine if the quantity of a high-affinity isolate of BVDV associated with single-washed or trypsin-treated embryos could cause infection in vivo. Twenty zona-pellucida-intact morulae and blastocysts (MB) were collected on day 7 from superovulated cows. After collection, all MB were washed according to International Embryo Transfer Society (IETS) standards, and all but 4 MB (negative controls) were exposed for 2 h to 10(5)-10(6) cell culture infective doses (50% endpoint) per milliliter (CCID(50)/mL) of viral strain SD-1. Following exposure, according to IETS standards, one half of the MB were washed and one half were trypsin treated. All MB were then individually sonicated, and sonicate fluids were injected intravenously into calves on day 0. Blood was drawn to monitor for viremia and(or) seroconversion. Seroconversion of calves injected with sonicate fluids from washed and trypsin-treated embryos occurred 38% and 13% of the time, respectively. Therefore, the quantity of a high-affinity isolate of BVDV associated with single-washed or trypsin-treated embryos was infective in vivo.

Biosecurity and biocontainment in alpaca operations

Biosecurity on South American camelid operations involves both external and internal measures to prevent the introduction and spread of disease. External biosecurity involves practices and techniques directed at the prevention of entry of new diseases into a group of animals. Internal biosecurity or biocontainment, involves practices and techniques that are directed at the prevention or spread of disease within an existing group of animals. External biosecurity is particularly important in North America camelid operations due to the extensive movement of animals for breeding or show purposes. Internal biosecurity typically involves this the prevention and treatment of failure of passive transfer, maintenance of proper nutrition and housing, and the implementation of an appropriate vaccination program for endemic or relevant diseases. Attention to appropriate cleaning and disinfection procedures related to housing, feeding, and treatment equipment is important for the maintenance of both internal and external biosecurity practices. This paper discusses various risk factors associated with the control of infectious disease in the context of external and internal biosecurity measures in camelids operations.

Infectivity of bovine viral diarrhea virus associated with in vivo-derived bovine embryos

Early research indicated that bovine viral diarrhea virus (BVDV) would not adhere to zona pellucida-intact (ZP-I), in vivo-derived bovine embryos. However, in a recent study, viral association of BVDV and in vivo-derived embryos was demonstrated. These findings raised questions regarding the infectivity of the embryo-associated virus. The objectives of this study were to evaluate the infectivity of BVDV associated with in vivo-derived bovine embryos through utilization of primary cultures of uterine tubal cells (UTC) as an in vitro model of the uterine environment and to determine if washing procedures, including trypsin treatment, were adequate to remove virus from in vivo-derived embryos. One hundred and nine ZP-I morulae and blastocysts (MB) and 77 non-fertile and degenerated (NFD) ova were collected on day 7 from 34, BVDV-negative, superovulated cows. After collection, all MB and NFD ova were washed according to International Embryo Transfer Society (IETS) standards and exposed for 2h to approximately 10(6) cell culture infective doses (50% endpoint) per milliliter of viral strain SD-1. Following exposure, some groups of <10 MB or NFD ova were washed in accordance with IETS standards. In addition, an equivalent number of MB and NFD ova were subjected to IETS standards for trypsin treatment. Subsequently, NFD ova were immediately sonicated and sonicate fluids were assayed for presence of virus, while individual and groups of MB were placed in microdrops containing primary cultures of UTCs and incubated. After 3 days, embryos, media, and UTCs were harvested from each microdrop and assayed for BVDV. Virus was detected in the sonicate fluids of 56 and 43% of the groups of NFD ova that were washed and trypsin-treated, respectively. After 3 days of microdrop culture, virus was not detected in media or sonicate fluids from any individual or groups of MB, regardless of treatment. However, virus was detected in a proportion of UTC that were co-cultured with washed groups of MB (30%), washed individual MB (9%) and trypsin treated individual MB (9%), but no virus was detected in the UTC associated with groups of trypsin-treated embryos. In conclusion, virus associated with developing embryos was infective for permissive cells. Further, the quantity of virus associated with a proportion of individual embryos (both washed and trypsin treated) was sufficient to infect the UTC. In light of these results, an attempt should be made to determine if the quantity of a high-affinity isolate of BVDV associated with an individual embryo would infect recipients via the intrauterine route.

Identified and unidentified challenges for reproductive biotechnologies regarding infectious diseases in animal and public health

The aim of the present paper is to review the known and theoretical risks for in vivo derived and in vitro produced embryos as well as for nuclear transferred or transgenic embryos in terms of animal diseases or diseases of public health consequence. For in vivo derived embryos, a considerable number of experiments and scientific investigations have resulted in recommended guidelines and procedures that ensure a high level of safety. The effectiveness of these measures has been validated by field experience with the safe transfer of several million embryos over the past three decades. In vitro produced embryos have several characteristics that differentiate them from the former, in particular a structure of the zona pellucida that results in a more frequent possible association of pathogens with the embryo. However, the guidelines prescribed by the IETS, the international standard setting body (OIE) and existing national regulatory frameworks are in place to minimize the risk of disease transmission. No specific public health risks have been identified to date with respect to in vivo or in vitro derived embryos. In regard to nuclear transferred and transgenic embryos, theoretical risks have been identified in relation to the potential effects on some intrinsic viruses such as endogenous retroviruses but very little targeted experimental work has been carried out on infectious diseases that could have adverse consequences on animal or human health. Although there has been no report of such adverse consequences associated with the limited number of animals produced to date by such reproductive technologies, a precautionary approach is warranted given the potential negative impacts and it would be prudent to restrict at this stage, the international movement of such "manipulated" embryos.

Epidemiologic concerns relative to in vivo and in vitro production of livestock embryos

Evidence indicates low potential for transmission of pathogens with in vivo-derived embryos of cattle when appropriate precautions are taken. In apparent contrast, results of research with in vivo-derived embryos of small ruminants and swine and with in vitro-derived embryos of cattle suggest a greater tendency for their association with pathogens after artificial exposure. However, regardless of donor species, investigations involving collection of embryos from artificially or naturally infected animals and assessment of health of recipients and offspring after transfer of these embryos have indicated low potential for transmitting disease. In this paper, results of embryo-pathogen research are summarized, emphasizing potential for spread of pathogens under natural circumstances. Also, safe embryo handling practices and their application to multiple species are discussed.