Appropriate housing and husbandry practices for laboratory Xenopus are key to maintaining good welfare standards and generating reliable experimental results. Although we lack empirical evidence for many housing and husbandry practices, Xenopus have been used as a laboratory species for decades. As a result, best practices have evolved over time as researchers and staff at frog facilities have built up experience on what helps to keep frogs in the best condition. Different Xenopus species have different care needs; this chapter covers housing and husbandry protocols for Xenopus laevis and Xenopus tropicalis. These are the current protocols of the European Xenopus Resource Centre (EXRC) in Portsmouth, United Kingdom. The EXRC provides services supporting researchers using Xenopus in research, including guidance on housing, husbandry, breeding and colony management, and maintaining healthy frogs to enable collection of reliable data. Here, we describe how to setup and seed a new recirculating system, surface sterilization of embryos, and identification of individual frogs. We also outline best practices for each life stage, including indicators of good health and normal behavior and signs of distress or poor health and protocols for handling disease outbreaks.
Use of animals in biomedical research is still considered essential by many in academia, industry and regulatory authorities. Therefore, it is important that legal, governance and welfare procedures are in place to ensure that only necessary procedures using animals are carried out and that this occurs within a framework with animal welfare at its core. Animal research in the United Kingdom is conducted under the Animals (Scientific Procedures) Act 1986 and animal research in the United Kingdom has long been seen as a flag bearer for high quality-high welfare research. An example of the leading role taken in supporting animal welfare in research was establishment of the National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs) to support reducing the scale and impact of animal research. Here, we provide an overview of governance and licensing procedures of animal research in the United Kingdom, coupled with explanations of how excellent welfare underpins high quality research, and examine the development of new approach methodologies.
The study of snake venom toxicity and evaluation of the neutralisation ability of antivenoms and novel therapeutic agents for envenoming has largely relied on animal tests, especially the analysis of the lethal activity of venoms and its neutralisation. In addition, other animal-based assays are used to assess pathology-specific effects of venoms. Despite their demonstrated value, these assays have several limitations. They involve acute stress and pain in animals, and their validity, vis-à-vis the characteristics of human snakebite envenoming, is limited owing to the nature of the assays. Therefore, urgent innovations are required in this field. Ensuring the implementation of the 3Rs (Replacement, Reduction, and Refinement) is essential when animal studies are required. These include: (a) refinement of the tests (e.g., use of analgesia, reduction of assay duration, and refining of humane endpoints); (b) reduction in the number of animals used by more thorough in vitro assessment of antivenoms prior to in vivo assays, and improved statistical analyses and group sizing; and, most importantly, and (c) replacement of in vivo rodent tests with validated in vitro approaches, such as immunoassays, enzymatic and cell-based assays, the use of invertebrate models, and the implementation of New Approach Methodologies (NAMs), i.e., novel in vitro or in silico techniques that model complex pathophysiological processes of envenoming. A roadmap involving researchers, manufacturers, quality control groups, regulators, and funding agencies is proposed, with the aim of driving significant changes in this field.
An assessment of potential developmental and reproductive toxicity (DART) is generally required to support clinical trials and marketing of pharmaceuticals. Although typically performed in rodents and rabbits, nonhuman primates (NHPs) are often used when they are the only pharmacologically relevant species. Regulatory guidances allow for weight of evidence (WoE) risk assessment for DART such that mature NHPs may not be needed to confirm expected or low risk of adverse pregnancy outcome. As such, there are numerous examples of WoE strategies to inform risk of adverse pregnancy outcome, but fewer to assess risk to male and/or female fertility, although emerging data indicate mature NHPs have limited impact on fertility risk assessment in product labels. Mature NHP data are most impactful to fill safety gaps when there are no relevant data from other species, limited information to establish WoE, and/or limited human data is available to characterize risk. In this review, we propose a detailed decision tree and examples to inform risk of adverse pregnancy outcome or male/female fertility impact by emphasizing and prioritizing WoE supplemented by experimental data where necessary, including use of NHPs as a last resort. Additional refinements to NHP use are also summarized.
