Regulatory and policy considerations for the implementation of gene drive-modified mosquitoes to prevent malaria transmission.

Gene drive-modified mosquitoes (GDMMs) are being developed as possible new tools to prevent transmission of malaria and other mosquito-borne diseases. To date no GDMMs have yet undergone field testing. This early stage is an opportune time for developers, supporters, and possible users to begin to consider the potential regulatory requirements for eventual implementation of these technologies in national or regional public health programs, especially as some of the practical implications of these requirements may take considerable planning, time and coordination to address. Several currently unresolved regulatory questions pertinent to the implementation of GDMMs are examined, including: how the product will be defined; what the registration/approval process will be for placing new GDMM products on the market; how the potential for transboundary movement of GDMMs can be addressed; and what role might be played by existing multinational bodies and agreements in authorization decisions. Regulation and policies applied for registration of other genetically modified organisms or other living mosquito products are assessed for relevance to the use case of GDMMs to prevent malaria in Africa. Multiple national authorities are likely to be involved in decision-making, according to existing laws in place within each country for certain product classes. Requirements under the Cartagena Protocol on Biodiversity will be considered relevant in most countries, as may existing regulatory frameworks for conventional pesticide, medical, and biocontrol products. Experience suggests that standard regulatory processes, evidence requirements, and liability laws differ from country to country. Regional mechanisms will be useful to address some of the important challenges.

Perspectives of African stakeholders on gene drives for malaria control and elimination: a multi-country survey.

BACKGROUND: Gene drive modified mosquitoes (GDMMs) have the potential to address Africa's persistent malaria problem, but are still in early stages of development and testing. Continuous engagement of African stakeholders is crucial for successful evaluation and implementation of these technologies. The aim of this multi-country study was, therefore, to explore the insights and recommendations of key stakeholders across Africa on the potential of GDMMs for malaria control and elimination in the continent. METHODS: A concurrent mixed-methods study design was used, involving a structured survey administered to 180 stakeholders in 25 countries in sub-Saharan Africa, followed by 18 in-depth discussions with selected groups and individuals. Stakeholders were drawn from academia, research and regulatory institutions, government ministries of health and environment, media and advocacy groups. Thematic content analysis was used to identify key topics from the in-depth discussions, and descriptive analysis was done to summarize information from the survey data. RESULTS: Despite high levels of awareness of GDMMs among the stakeholders (76.7%), there was a relatively low-level of understanding of their key attributes and potential for malaria control (28.3%). When more information about GDMMs was provided to the stakeholders, they readily discussed their insights and concerns, and offered several recommendations to ensure successful research and implementation of the technology. These included: (i) increasing relevant technical expertise within Africa, (ii) generating local evidence on safety, applicability, and effectiveness of GDMMs, and (iii) developing country-specific regulations for safe and effective governance of GDMMs. A majority of the respondents (92.9%) stated that they would support field trials or implementation of GDMMs in their respective countries. This study also identified significant misconceptions regarding the phase of GDMM testing in Africa, as several participants incorrectly asserted that GDMMs were already present in Africa, either within laboratories or released into the field. CONCLUSION: Incorporating views and recommendations of African stakeholders in the ongoing research and development of GDMMs is crucial for instilling stakeholder confidence on their potential application. These findings will enable improved planning for GDMMs in Africa as well as improved target product profiles for the technologies to maximize their potential for solving Africa's enduring malaria challenge.

Evaluation of a survey for acute care programme directors on the utilisation of point-of-care ultrasound.

PURPOSE: Point-of-care ultrasound (POCUS) is ultrasound brought to the patient's bedside and performed in 'real time' by the healthcare provider. The utility of POCUS to facilitate management of the acutely ill patient has been demonstrated for multiple pathologies. However, the integration of ultrasonography and echocardiography training into residency curriculum varies across the acute care specialties. STUDY DESIGN: After an institutional review board approval, anaesthesiology, emergency medicine, family medicine, internal medicine, paediatrics and general surgery programme directors (PDs) were surveyed. The survey consisted of 11 questions evaluating the primary bedside assessment tool for common acute care situations, POCUS topics that the PDs were comfortable practising and topics that the PDs felt were useful for their specialty. Barriers to POCUS use, certification and documentation were also surveyed. RESULTS: Overall, 270 PD surveys were completed. The preferred primary assessment tool for common acute care situations varied with specialty; emergency medicine PDs consistently responded that POCUS was the diagnostic modality of choice (p<0.0001). The majority of the PDs reported lack of educational opportunities as the primary barrier to learning POCUS (64%). Most PDs indicated that POCUS examinations should be documented (95.7%), and 39% reported that departmental certification would be sufficient. CONCLUSIONS: This study is the first to evaluate differences in the preferred initial bedside assessment tool between the acute care specialties. Although POCUS is a superior tool for evaluating acute pathologies, disconnect between education and utilisation remains. This study highlights the need to incorporate POCUS into the acute care specialty curriculum.

Biomarker profiling for risk of future heart failure (HFpEF) development.

BACKGROUND: The purpose of this study was to investigate the utility of BNP, hsTroponin-I, interleukin-6, sST2, and galectin-3 in predicting the future development of new onset heart failure with preserved ejection fraction (HFpEF) in asymptomatic patients at-risk for HF. METHODS: This is a retrospective analysis of the longitudinal STOP-HF study of thirty patients who developed HFpEF matched to a cohort that did not develop HFpEF (n = 60) over a similar time period. Biomarker candidates were quantified at two time points prior to initial HFpEF diagnosis. RESULTS: HsTroponin-I and BNP at baseline and follow-up were statistically significant predictors of future new onset HFpEF, as was galectin-3 at follow-up and concentration change over time. Interleukin-6 and sST2 were not predictive of future development of new onset HFpEF in this study. Unadjusted biomarker combinations of hsTroponin-I, BNP, and galectin-3 could significantly predict future HFpEF using both baseline (AUC 0.82 [0.73,0.92]) and follow-up data (AUC 0.86 [0.79,0.94]). A relative-risk matrix was developed to categorize the relative-risk of new onset of HFpEF based on biomarker threshold levels. CONCLUSION: We provided evidence for the utility of BNP, hsTroponin-I, and Galectin-3 in the prediction of future HFpEF in asymptomatic event-free populations with cardiovascular disease risk factors.

Comparison of longitudinal change in sST2 vs BNP to predict major adverse cardiovascular events in asymptomatic patients in the community.

Biomarker-based preventative and monitoring strategies are increasingly used for risk stratification in cardiovascular (CV) disease. The aim of this study was to investigate the utility of longitudinal change in B-type natriuretic peptide (BNP) and sST2 concentrations for predicting incident major adverse CV events (MACE) (heart failure, myocardial infarction, arrhythmia, stroke/transient ischaemic attack and CV death) in asymptomatic community-based patients with risk factors but without prevalent MACE at enrolment. The study population consisted of 282 patients selected from the longitudinal STOP-HF study of asymptomatic patients with risk factors for development of MACE. Fifty-two of these patients developed a MACE. The study was run in two phases comprising of an initial investigative cohort (n = 195), and a subsequent 2:1 (No MACE: MACE) propensity matched verification cohort (n = 87). BNP and sST2 were quantified in all patients at two time points a median of 2.5 years apart. Results highlighted that longitudinal change in sST2 was a statistically significant predictor of incident MACE, (AUC 0.60). A one-unit increment in sST2 change from baseline to follow up corresponded to approximately 7.99% increase in the rate of one or more incident MACE, independent of the baseline or follow-up concentration. In contrast, longitudinal change value of BNP was not associated with MACE. In conclusion, longitudinal change in sST2 but not BNP was associated with incident MACE in asymptomatic, initially event-free patients in the community. Further work is required to evaluate the clinical utility of change in sST2 in risk prediction and event monitoring in this setting.

Shingrix: The New Adjuvanted Recombinant Herpes Zoster Vaccine.

OBJECTIVES: To review the immunogenicity, efficacy, and safety of the herpes zoster subunit vaccine (HZ/su) for use in adult patients for the prevention of shingles. DATA SOURCES: A literature search through PubMed was conducted (June 2008 to October 2017) using the terms shingles vaccine and varicella zoster virus. References from retrieved articles and the prescribing information were also reviewed for any additional material. STUDY SELECTION/DATA EXTRACTION: The literature search was limited to human studies published in English. Randomized controlled, multicenter trials were reviewed and included to evaluate the safety and efficacy of HZ/su. Literature on the epidemiology and pathology of herpes zoster virus infections and recommendations from the Advisory Committee on Immunization Practices (ACIP) were also reviewed. DATA SYNTHESIS: HZ/su is a new adjuvanted recombinant vaccine approved by the Food and Drug Administration for the prevention of herpes zoster in adults 50 years of age and older. HZ/su significantly reduced the risk of developing herpes zoster by more than 90% as compared with placebo and displayed a comparable adverse effect profile. The most common local adverse events were injection site pain, redness, and swelling, and the most common systemic adverse events were myalgia, fatigue, and headache. The ACIP recommends the routine use of HZ/su as the preferred vaccine for the prevention of herpes zoster in immunocompetent adults 50 years of age and older. CONCLUSIONS: Based on published immunogenicity, efficacy, and safety data, as well as the recent recommendations by the ACIP, HZ/su should be included on both hospital and community pharmacy formularies and recommended to all immunocompetent patients older than 50 years to prevent herpes zoster.

Simian Varicella Virus Is Present in Macrophages, Dendritic Cells, and T Cells in Lymph Nodes of Rhesus Macaques after Experimental Reactivation.

UNLABELLED: Like varicella-zoster virus (VZV), simian varicella virus (SVV) reactivates to produce zoster. In the present study, 5 rhesus macaques were inoculated intrabronchially with SVV, and 5 months later, 4 monkeys were immunosuppressed; 1 monkey was not immunosuppressed but was subjected to the stress of transportation. In 4 monkeys, a zoster rash developed 7 to 12 weeks after immunosuppression, and a rash also developed in the monkey that was not immunosuppressed. Analysis at 24 to 48 h after zoster revealed SVV antigen in the lung alveolar wall, in ganglionic neurons and nonneuronal cells, and in skin and in lymph nodes. In skin, SVV was found primarily in sweat glands. In lymph nodes, the SVV antigen colocalized mostly with macrophages, dendritic cells, and, to a lesser extent, T cells. The presence of SVV in lymph nodes, as verified by quantitative PCR detection of SVV DNA, might reflect the sequestration of virus by macrophages and dendritic cells in lymph nodes or the presentation of viral antigens to T cells to initiate an immune response against SVV, or both. IMPORTANCE: VZV causes varicella (chickenpox), becomes latent in ganglia, and reactivates to produce zoster and multiple other serious neurological disorders. SVV in nonhuman primates has proved to be a useful model in which the pathogenesis of the virus parallels the pathogenesis of VZV in humans. Here, we show that SVV antigens are present in sweat glands in skin and in macrophages and dendritic cells in lymph nodes after SVV reactivation in monkeys, raising the possibility that macrophages and dendritic cells in lymph nodes serve as antigen-presenting cells to activate T cell responses against SVV after reactivation.

Influence of diabetes on natriuretic peptide thresholds in screening for Stage B heart failure.

CONTEXT: Natriuretic peptide (NP) has been shown to be an effective screening tool to identify patients with Stage B heart failure and to have clinical value in preventing heart failure progression. The impact of associated metabolic confounders on the screening utility of NP needs clarification. OBJECTIVE: To assess the impact of diabetes mellitus (DM) on NP screening for asymptomatic Stage B heart failure. MATERIALS AND METHODS: The study population consisted of 1368 asymptomatic patients with cardiovascular risk factors recruited from general practice as part of the STOP-HF trial. B-type NP (BNP) was quantified at point-of-care. RESULTS: BNP was found to be as accurate for detecting Stage B heart failure in DM patients compared to non-DM patients (AUC 0.75 [0.71,0.78] and 0.77 [0.72,0.82], respectively). However, different BNP thresholds are required to achieve the same level of diagnostic sensitivity in DM compared with non-DM patients. To achieve 80% sensitivity a difference of 5-ng/L lower is required for patients with DM. CONCLUSION: Although a significantly different BNP threshold is detected for patients with DM, the BNP concentration difference is small and unlikely to warrant a clinically different diagnostic threshold.

Inhibition of phosphorylated-STAT1 nuclear translocation and antiviral protein expression in human brain vascular adventitial fibroblasts infected with varicella-zoster virus.

In varicella-zoster virus (VZV)-infected primary human brain vascular adventitial fibroblasts (BRAFs), levels of beta interferon (IFN-ß,) STAT1, and STAT2 transcripts as well as STAT1 and STAT2 protein were decreased. IFN-α transcript levels were increased but not secreted IFN-α protein levels. Compared to IFN-α-treated control results, in VZV-infected BRAFs, phosphorylated STAT1 did not translocate to the nucleus, resulting in impaired downstream expression of interferon-inducible antiviral Mx1. Overall, VZV interference with the type I interferon pathway may promote virus persistence in cerebral arteries.

T cells increase before zoster and PD-1 expression increases at the time of zoster in immunosuppressed nonhuman primates latently infected with simian varicella virus.

Like varicella zoster virus in humans, simian varicella virus (SVV) becomes latent in ganglionic neurons along the entire neuraxis and reactivates in immunosuppressed monkeys. Five rhesus macaques were inoculated with SVV; 142 days later (latency), four monkeys were immunosuppressed, and T cells were analyzed for naïve, memory, and effector phenotypes and expression of programmed death receptor-1 (PD-1; T cell exhaustion). All T cell subsets decreased during immunosuppression and except for CD8 effectors, peaked 2 weeks before zoster. Compared to before immunosuppression, PD-1 expression increased at reactivation. Increased T cells before zoster is likely due to virus reactivation.

Robust pro-inflammatory and lesser anti-inflammatory immune responses during primary simian varicella virus infection and reactivation in rhesus macaques.

Simian varicella virus (SVV) infection of non-human primates models human varicella zoster virus (VZV) infection. Assessment of cell signaling immune responses in monkeys after primary SVV infection, after immunosuppression and during reactivation revealed strong pro-inflammatory responses and lesser anti-inflammatory components during varicella and reactivation. Pro-inflammatory mediators elevated during varicella included interferon-gamma (IFN-γ), interleukin (IL)-6, monocyte chemoattractant protein (MCP-1), interferon inducible T-cell α chemoattractant protein (I-TAC), interferon processing protein (IP-10), and anti-inflammatory interleukin-1 Receptor antagonist (IL-1Ra). After immunosuppression and at reactivation, levels of pro-inflammatory mediators MCP-1, eotaxin, IL-6, IL-8, MIF, RANTES (regulated-on-activation normal T-cell expressed and secreted), and HGF (hepatocyte growth factor) were elevated, as was the anti-inflammatory mediator IL-1Ra. Characterization of cytokine, chemokine and growth factor responses during different stages of varicella virus infection will facilitate immunotherapeutic and vaccine strategies.

Taking stock: Is gene drive research delivering on its principles?

Gene drive technology has been recognized for its potential to provide durable and cost-effective solutions for previously intractable problems in public health, conservation, and agriculture. In recognition of the rapid advances in this field, in 2016 the U.S. National Academies of Sciences, Engineering, and Medicine issued a report making several recommendations aimed at researchers, funders, and policymakers for the safe and responsible research and development of gene drive technology. Subsequently, in 2017 sixteen global organizations self-identifying as sponsors and supporters of gene drive research became public signatories committed to the 'Principles for Gene Drive Research' which were inspired by the report's recommendations. Herein we reflect on the progress of gene drive research in relation to the ethical principles laid out and committed to by the signatories to the Principles. Our analysis indicates high levels of alignment with the Principles in the field of gene drive research. The manuscript also discusses the Gene Drive Research Forum, which had its genesis in the publication of the Principles. Discussions between participants at the latest meeting of the Forum point to the work that lies ahead for gene drive research in line with the Principles. Going forward the gene drive research community can productively focus on: i) safety and efficacy criteria for open release, ii) risk assessment frameworks and methods, iii) more downstream technical, regulatory and policy considerations for field evaluations and implementation, iv) continued transparency and developing mechanisms of accountability, and v) strengthening capacity in locales of potential release and expected drive spread.

Tacaribe virus causes fatal infection of an ostensible reservoir host, the Jamaican fruit bat.

Tacaribe virus (TCRV) was first isolated from 11 Artibeus species bats captured in Trinidad in the 1950s during a rabies virus surveillance program. Despite significant effort, no evidence of infection of other mammals, mostly rodents, was found, suggesting that no other vertebrates harbored TCRV. For this reason, it was hypothesized that TCRV was naturally hosted by artibeus bats. This is in stark contrast to other arenaviruses with known hosts, all of which are rodents. To examine this hypothesis, we conducted experimental infections of Jamaican fruit bats (Artibeus jamaicensis) to determine whether they could be persistently infected without substantial pathology. We subcutaneously or intranasally infected bats with TCRV strain TRVL-11573, the only remaining strain of TCRV, and found that low-dose (10(4) 50% tissue culture infective dose [TCID(50)]) inoculations resulted in asymptomatic and apathogenic infection and virus clearance, while high-dose (10(6) TCID(50)) inoculations caused substantial morbidity and mortality as early as 10 days postinfection. Uninoculated cage mates failed to seroconvert, and viral RNA was not detected in their tissues, suggesting that transmission did not occur. Together, these data suggest that A. jamaicensis bats may not be a reservoir host for TCRV.

The Promise and Challenge of Genetic Biocontrol Approaches for Malaria Elimination.

Malaria remains an ongoing public health challenge, with over 600,000 deaths in 2021, of which approximately 96% occurred in Africa. Despite concerted efforts, the goal of global malaria elimination has stalled in recent years. This has resulted in widespread calls for new control methods. Genetic biocontrol approaches, including those focused on gene-drive-modified mosquitoes (GDMMs), aim to prevent malaria transmission by either reducing the population size of malaria-transmitting mosquitoes or making the mosquitoes less competent to transmit the malaria parasite. The development of both strategies has advanced considerably in recent years, with successful field trials of several biocontrol methods employing live mosquito products and demonstration of the efficacy of GDMMs in insectary-based studies. Live mosquito biocontrol products aim to achieve area-wide control with characteristics that differ substantially from current insecticide-based vector control methods, resulting in some different considerations for approval and implementation. The successful field application of current biocontrol technologies against other pests provides evidence for the promise of these approaches and insights into the development pathway for new malaria control agents. The status of technical development as well as current thinking on the implementation requirements for genetic biocontrol approaches are reviewed, and remaining challenges for public health application in malaria prevention are discussed.

Requirements for market entry of gene drive-modified mosquitoes for control of vector-borne diseases: analogies to other biologic and biotechnology products.

Gene drive-modified mosquitoes (GDMMs) are proposed as new tools for control and elimination of malaria and other mosquito-borne diseases, and promising results have been observed from testing conducted in containment. Although still at an early stage of development, it is important to begin now to consider approval procedures and market entry strategies for the eventual implementation of GDMMs in the context of disease control programs, as these could impact future research plans. It is expected that, as for other types of new products, those seeking to bring GDMMs to market will be required to provide sufficient information to allow the regulator(s) to determine whether the product is safe and effective for its proposed use. There already has been much emphasis on developing requirements for the biosafety components of the "safe and effective" benchmark, largely concerned with their regulation as genetically modified organisms. Other potential approval requirements have received little attention, however. Although GDMMs are expected to be implemented primarily in the context of public health programs, any regulatory analogies to other public health products, such as pharmaceuticals, vaccines, or chemical pesticides, must take into account the characteristics of live mosquito products. Typical manufacturing standards related to product identity, potency or quality will need to be adapted to GDMMs. Valuable lessons can be drawn from the regulatory approval processes for other whole organism and genetically modified (GM) organism products. Supply chain requirements, such as scale of production, location and design of production facilities, and methods of distribution and delivery, will be dependent upon the characteristics of the particular GDMM product, the conditions of use, and the region to be served. Plans for fulfilling supply chain needs can build upon experience in the development of other live insect products for use in public health and agriculture. Implementation of GDMMs would benefit from additional research on enabling technologies for long-term storage of mosquito life stages, efficient mass production, and area-wide delivery of GDMMs. Early consideration of these practical requirements for market entry will help to mitigate downstream delays in the development of these promising new technologies.

Adults with Trisomy 21 Have Differential Antibody Responses to Influenza A.

Down syndrome is caused by an extra copy of chromosome 21. In the past two decades, the life expectancy of individuals with Down syndrome has significantly increased from early 20s to early 60s, creating a population of individuals of which little is known about how well they are protected against infectious disease. The goal of this work is to better understand if adults with Down syndrome are well protected against influenza following vaccination. We obtained plasma samples from 18 adults (average age = 31yo) with Down syndrome and 17 age/gender-matched disomic individuals, all vaccinated against influenza. Antibody concentration to influenza A was measured using ELISA and antibody titers were measured using a hemagglutinin inhibition assay. Statistical analysis was performed using Stata Statistical Software. Adults with Down syndrome had a significantly increased concentration of antibodies to a mixture of influenza A viral proteins; however, they had a significantly decreased titer to the Influenza A/Hong Kong compared to disomic controls. These findings suggest that more vigorous studies of B- and T-cell function in adults with Down syndrome with respect to influenza vaccination are warranted, and that this population may benefit from a high-dose influenza vaccine.

A report from the Irish women in cardiology survey, exploring Europe's largest gender gap in cardiology.

Aims: In Ireland, 8% of public cardiology consultants are female; this is the lowest proportion in Europe. We sought to understand perceptions amongst Irish trainees and consultants regarding aspects of working in cardiology in order to identify areas that can be targeted to improve gender equality. Methods and Results: In September 2021, the Irish Cardiac Society distributed a questionnaire to trainees and consultants in the Republic and Northern Ireland. Ethical approval was obtained from the University College Dublin, Ireland. There were 94 respondents (50% male, 50% consultants) which equates to ∼30% of all trainees and consultants in all Ireland. Although females were more likely to be single, overall, they had additional child-care responsibilities compared with male counterparts. Despite 53% of the respondents preferring to work less than full time, 64% reported a perceived lack of support from their departments. Males were significantly more likely to go into procedural/high radiation sub-specialities. Bullying was reported by 53% of females. Almost 80% of females experienced sexism and 30% reported being overlooked for professional advancement based on their sex. Females also rated their career prospects lower than males. Key challenges for women were: sexism, maternity leave/child-care responsibilities, cardiology as a 'boys club' and lack of flexible training. There was interest from both males and females in a mentorship programme and support for women in leadership positions. Conclusion: Discrimination including sexism, bullying, and equal opportunity for professional advancement are key aspects that need to be addressed to improve gender balance in cardiology within Ireland and Northern Ireland.

Investigating transmission of SARS-CoV-2 using novel face mask sampling: a protocol for an observational prospective study of index cases and their contacts in a congregate setting.

INTRODUCTION: This study aims to measure how transmission of SARS-CoV-2 occurs in communities and to identify conditions that lend to increased transmission focusing on congregate situations. We will measure SARS-CoV-2 in exhaled breath of asymptomatic and symptomatic persons using face mask sampling-a non-invasive method for SARS-CoV-2 detection in exhaled air. We aim to detect transmission clusters and identify risk factors for SARS-CoV-2 transmission in presymptomatic, asymptomatic and symptomatic individuals. METHODS AND ANALYSIS: In this observational prospective study with daily follow-up, index cases and their respective contacts are identified at each participating institution. Contact definitions are based on Centers for Disease Control and Prevention and local health department guidelines. Participants will wear masks with polyvinyl alcohol test strips adhered to the inside for 2 hours daily. The strips are applied to all masks used over at least 7 days. In addition, self-administered nasal swabs and (optional) finger prick blood samples are performed by participants. Samples are tested by standard PCR protocols and by novel antigen tests. ETHICS AND DISSEMINATION: This study was approved by the Colorado Multiple Institutional Review Board and the WHO Ethics Review Committee. From the data generated, we will analyse transmission clusters and risk factors for transmission of SARS-CoV-2 in congregate settings. The kinetics of asymptomatic transmission and the evaluation of non-invasive tools for detection of transmissibility are of crucial importance for the development of more targeted control interventions-and ultimately to assist with keeping congregate settings open that are essential for our social fabric. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov (#NCT05145803).

Evaluation of medetomidine-ketamine-butorphanol anesthesia with atipamezole-naltrexone antagonism in captive male guanacos (Lama guanicoe).

Seven captive adult male guanacos (Lama guanicoe) weighing 112.0 +/- 10.9 kg (mean +/- standard deviation) were anesthetized with a combination of medetomidine (90.0 +/- 8.8 microg/kg), ketamine (2.7 +/- 0.3 mg/kg), and butorphanol (0.3 +/- 0.03 mg/kg) administered intramuscularly to evaluate its anesthetic and cardiopulmonary effects. Inductions were smooth and rapid, with a mean time to initial effect of 3 +/- 1.5 min and a mean time to recumbency of 5.1 +/- 3.1 min. Anesthesia was predictable, smooth, and characterized by excellent muscle relaxation. Spontaneous ventilation was maintained throughout anesthesia in all animals. Marked bradycardia ranging from 24 to 52 beats/min was noted across all time points for all individuals. Median heart rates decreased during the procedures, but median heart rate, temperature, respiratory rate, and end-tidal carbon dioxide values over the 20 min monitoring period were not significantly different. Mean arterial partial pressure of oxygen (PaO2) on initial sampling was 65.9 +/- 14.8 mm Hg, with six of seven animals exhibiting hypoxemia (PaO2 <80 mm Hg). After oxygen supplementation for 20 min, mean PaO2 values showed statistically significant increases to a mean value of 127.7 +/- 32.4 mm Hg (P = 0.0014). Mean arterial partial pressure of carbon dioxide (PaCO2) showed a significant increase over the monitoring period (P = 0.0004), and mild hypoventilation (PaCO2 >45 mm Hg) was noted in four animals. Mean total duration of procedure time was 23.3 +/- 3.3 min. All guanacos received 0.45 +/- 0.04 mg/kg atipamezole and 2.7 +/- 0.25 mg/kg naltrexone administered intramuscularly for anesthetic antagonism. Recoveries were smooth and uncomplicated. Mean time to sternal recumbency after antagonist administration was 7.7 +/- 4.5 min, and time to successful standing was 12.9 +/- 5.0 min, with all animals standing on first attempt.