In the last 5 years, the well being of veterinarians has been prioritized and evaluated as a profession with significant mental health challenges (1–10). However, the veterinarians that practice swine veterinary medicine in the United States have not been evaluated as a subset of the profession. Additionally, a portion of the swine veterinarians' application and oversight of mass depopulation needed to be studied utilizing the non-participating swine veterinarians as a comparative cohort. Understanding the mental health baseline of swine veterinarians and the subsequent effect of mass depopulation can guide the veterinary profession for the future care of veterinarians in critical emergency situations.

The restriction of animal movement to slaughter started affecting U.S. swine producers in late March 2020 as packing plants started diagnosing COVID-19 in their worker populations (11). This unprecedented pork processing disruption can only be equated to the live animal movement restrictions experienced during previous disease eradication efforts related to foreign animal disease (FAD) (12). During FAD outbreaks, the animals that cannot be salvaged as food are strategically killed to relieve overcrowding or other deteriorating animal welfare situations. This process is called “Welfare Slaughter” (13), defined and quantified by Terry Whiting (14–16). The Canadian Food and Agriculture Emergency Response System (FAERS) defines this type of emergency as “an abnormal situation requiring prompt action beyond normal procedures to prevent injury or damage to people, plants, livestock, property or the environment (17). The American Veterinary Medical Association speaks to this issue within their guidelines on the depopulation of animals (18). Additionally, the American Association of Swine Veterinarians clarifies that depopulation is necessary for several situations, including market disruption that can negatively impact animal welfare (19–21).

Veterinarians are at the center of the emergency mass depopulation process, providing guidance and animal welfare oversight. The responsibility of euthanizing animals, under any circumstances, can create moral stress, often called the “caring-killing paradox,” as veterinarians struggle to balance their love for animals with the necessity to euthanize (22–24). Studies involving those whose work involves euthanizing animals have found that many of these individuals suffer from a form of post-traumatic stress disorder (PTSD) labeled perpetration-induced traumatic stress (PITS) (25, 26). PITS differs from PTSD because PTSD follows a life-threatening or terrifying experience. Alternately, PITS does not involve a direct threat to the individual; instead, it may threaten their ethical character; per se, their identity as a veterinarian who cares for animals yet must implement euthanasia or the death of that animal (16, 27, 28). This phenomenon, including its psychological and emotional impact, has pe rhaps been most studied in shelter animal caretakers (26, 29–31). Additionally, these adverse effects have been seen in farm caretakers conducting routine applications and farmers impacted by euthanizing animals during a foot and mouth disease outbreak (32–34). A study by Makita, focusing on the mental distress of field veterinarians in the 2010 foot and mouth disease outbreak in Japan, found similar negative effects (35).

Yet, veterinarians who applied mass depopulation methods during COVID-19 faced an unprecedented challenge, and it is unknown how the depopulation events may have impacted their psychological and emotional well being. Therefore, this study's goals were five-fold:

An anonymous online survey was created to evaluate swine veterinarians' experiences and perceptions regarding the COVID-19 depopulation event from April 2020 to June 2020. Researchers from Colorado State University and Merck Animal Health created and tested the survey and then piloted for appropriate branching and potentially ambiguous or missing response options. Results of the testing were incorporated into the final version of the survey. A link to the survey was distributed via an email invitation to all members of the American Association of Swine Veterinarians (AASV), and access was made available from December 2, 2020, to January 30, 2021. AASV has ~1,300 members worldwide, but the survey was limited to swine veterinarians currently practicing veterinary medicine in the United States. This sample included all U.S. swine veterinarians, regardless of whether they had been involved in the COVID-19 depopulation event. An incentive to complete the survey was included by informing potential participants that $25 would be contributed to the AASV Foundation for every completed questionnaire. In addition, two reminder emails were sent. The study was categorized as exempt by Colorado State University's Institutional Review Board, and the survey was administered via a Qualtrics survey link with branching logic used to display only questions relevant to each participant. The first question was a screening question to ensure respondents were currently practicing swine veterinary medicine.

Veterinarians who self-identified as not currently practicing swine veterinary medicine were eliminated from further analysis. The body of the survey consisted of demographics (i.e., age, race, ethnicity, sex, marital status, number of children), general employment questions (e.g., current position, type of practice), and several questions related to mental health. These included views about mental health, personal experiences, and reported involvement with healthy behaviors (e.g., volunteering, sleeping 8 h/night, socializing with friends).

Additional mental health assessments included The Cantril Self-Anchoring Scale (36), which is comprised of one question that asks participants to place themselves on an 11-step ladder with the worst possible life represented by 0 and best possible life represented by 10. Gallup has used the Cantril Ladder to assess well being in over 150 countries. Scores are categorized into suffering (0–4), Struggling (5, 6), and Thriving (7–10, 37). Participants were also asked to complete The Physician well being Index (38) burnout scale, which is comprised of seven yes/no questions. Participants receive a score from 0–7 (1 point for each item answered “yes”), with scores ≥ 4 indicating a lower quality of life (QOL) and scores <2 reflecting higher QOL.

The Kessler Psychological Distress Scale (39) was used to assess psychological distress. The scale consists of 6 items in which respondents assign a score. The score ranges from 1 (none of the time) to 5 (all of the time) to determine the presence or absence of psychological distress. Significant psychological distress is determined by scores ≥13 (40).

The Brief Resilience Scale (BRS) (41) is a short scale used to measure the ability to bounce back from stress (42). The BRS is positively correlated with optimism, purpose in life, social support, and coping mechanisms. Conversely, it is negatively correlated with pessimism and negative interactions, behavioral disengagement, perceived stress, anxiety, depression, fatigue, and pain (41). The scale consists of six items to which participants are asked to indicate agreement level on a 5 point Likert scale (1 = strongly disagree, and 5 = strongly agree). Cronbach's alpha has been found to range from 0.80 to 0.92 (41).

Next, participants were asked their agreement level on a 5-point scale (1 = strongly disagree 5 = strongly agree) to 14 questions about job satisfaction. Although some of these questions have been asked in previous studies (9, 10), the created factors were unique to this study. Factor analysis was used to create three factors from these questions including intrinsic job factors (α = 0.83), environment (α = 0.66), and benefits/job factors (α = 0.74); explaining 38.8, 10.98, and 8.29% of the variance, respectively (total variance explained was 58.03%).

The next series of questions pertained to the COVID-19 depopulation effort. Participants were asked to indicate their involvement level with depopulation before COVID-19 and their involvement with the COVID-19 depopulation effort. Those who indicated they were involved in the COVID-19 depopulation effort were then asked a series of questions about their involvement, including the period of time involved, an approximate number of pigs depopulated, method(s) of depopulation utilized. Potential distress related to the COVID-19 depopulation was assessed with 13 items to which participants were asked to rate on a 5-point Likert scale from 1 = no distress at all to 5 = extreme stress. Factor analysis was used to construct two factors of COVID-19 depopulation distress that explained 48.5 and 12.36% variance, respectively. These factors were Ethics of care (α = 0.90) and Perceptions of others (α = 0.87).

Those veterinarians involved in the COVID-19 depopulation event were also given select questions from the Event Characteristics Questionnaire (ECQ). The ECQ (43) is designed to assess the impact of major events and consists of 38 items that assess nine categories. This study included four questions for five categories: challenge (amount of stress and anxiety associated with the event), emotional significance (emotional impact of the event); impact (the extent to which one's life has changed due to the event), change in world views (how much one's views have changed due to the event), and social status change (changes in one's social status).

Descriptive statistics were calculated for participant demographics, mental health assessments, and depopulation-related variables. Principal axis factor was used with principal component analysis for extraction and Oblimin with Kaiser Normalization rotation method. The number of factors for Job Satisfaction and COVID-19 depopulation distress were chosen because of the “leveling off” of eigen values on the scree plot. Multiple regression was used to explore predictors of well being, burnout, and psychological distress. Pearson correlation was used to assess the relationship between resiliency [as measured by the Brief Resilience Scale (BRS)] and well being, burnout, and psychological distress. One-way ANOVA was used to explore the relationship between involvement in the COVID-19 depopulation event and well being, burnout, and psychological distress. Lastly, one way ANOVA was used to explore the relationship between method of depopulation used (VSD+ or other methods) on well being, psychological distress, burnout, depopulation distress (ethics of care, perception of others), and ECQ factors (challenge, emotional significance, impact, change in world views, social status change). The significance level (α) was set at a conservative p = 0.01 due to the number of analyses, and all tests were two-tailed. Data were analyzed using SPSS (IBM, Armonk, NY, USA).

This study was designed to better understand the mental health needs related to well being, quality of life (QOL), psychological distress, burnout, and resilience of all U.S. swine veterinarians, both those who applied mass depopulation methods during COVID-19 and those who did not. Additionally, we assessed the coping methods utilized by swine veterinarians for improved well being. We have used these results to create recommendations for intervention strategies and supportive services to assist veterinarians in future mass depopulation events.

Numerous studies have documented the increased risk of anxiety, depression, and suicidal thoughts and lower levels of positive mental well being among veterinarians in the United States (44–46), the United Kingdom (47–49), and Australia (50, 51). A recent study by Perret (6) found that Canadian veterinarians had higher levels of perceived stress, burnout, depression, anxiety, compassion fatigue, and suicidal ideation than the general population. Burnout, a psychological syndrome comprised of emotional exhaustion, depersonalization, and a sense of reduced personal accomplishment (52), was also noted as a significant area of concern in a recent study of U.S. veterinary house officers (53). Both compassion fatigue and burnout result from external and internal stressors commonly found in veterinary medicine (4).

The Merck Animal Health Veterinary Wellbeing Studies (9, 10) found that veterinarians have lower well being than the general population but did not find an overall difference in serious psychological distress. However, upon deeper analysis, they found that young and female veterinarians were more likely to suffer from serious psychological distress and lower well being levels than older and male veterinarians. Additionally, they found that food animal veterinarians had higher levels of well being than other types of veterinarians and the general public. Similarly, the current study found that the majority of swine veterinarians report high levels of well being. Utilizing The Candril Ladder Index, we found that 87% of participants scored in the thriving category, 13% in the struggling category, and no one in the lowest (suffering) category.

Additionally, only 3% of participants reported significant psychological distress as measured by The Kessler 6 Psychological Distress Scale. Similar scores for well being and psychological distress among large animal veterinarians were reported by Volk (9, 10). When assessing burnout in the current study, the mean score of all participants was 2.32, comparable to a score of 2.4 for swine veterinarians in the Merk study (10). This translates into 29% of participants reporting at least moderate levels of burnout. It is important to note that there was a significant relationship between participants' involvement in the COVID-19 depopulation effort and the method of depopulation utilized on reported levels of burnout.

Numerous factors are related to high stress and negative mental health among veterinarians. It has been suggested that some personality traits might increase the risk of anxiety, depression, and burnout among veterinarians. These traits include perfectionism, neuroticism, and a preference to work with animals rather than people (54). External factors that can impact mental health include both work and personal issues. Work factors include hours worked, client expectations, relationships with colleagues, complaints, and litigation risks (55). Personal factors include personal finances, career concerns, and difficult life circumstances (49, 56, 57). In the current study, we found that higher endorsement of intrinsic job factors (e.g., “I am enjoying the work that I do,” “I often learn something new at work”) predicted higher levels of well being.

Because healthy lifestyle behaviors can positively impact mental health, in addition to questions about psychological support services, participants were asked to report their engagement in healthy behaviors. Most participants reported engaging in various self-care habits, with the most common ones including spending time with family, hiking, walking, or similar activity, socializing with friends, and spending time on a hobby. The percent of participants who reported engaging in these activities was higher than that reported by Volk (9). When assessing the impact of these healthy lifestyle behaviors, we found that sleeping at least 8 h a night positively affected burnout and psychological distress. Other behaviors that were found to mitigate psychological distress include socializing with friends and spending time with family.

One serious consequence of negative mental health that has garnered increased attention is suicide. It has been noted that veterinarians and veterinary technicians are at increased risk for suicide, suicide attempts, and suicidal ideation (57, 58). Furthermore, a 2014 survey of U.S. veterinarians found that female veterinarians consider suicide more often than males; but both male and female veterinarians consider suicide more often than the general population (45). Female veterinarians in clinical roles are 3.4 times more likely to die by suicide than the general population (59). Other studies have echoed these results, finding that female veterinarians have a higher prevalence of risk factors for suicide and higher suicide rates than male veterinarians or the general population (46, 47, 54, 60, 61). In Volk (10), 10% of swine veterinarians indicated they had thought about suicide; a similar percentage (10%) of respondents reported suicide ideation in the current study.

One unique factor of veterinary medicine is euthanasia. Euthanasia has been defined as a moral stressor, qualitatively different from other types of workplace stressors (24). Several studies have documented the negative effects of euthanasia on veterinary professionals (62–64). Involvement with euthanasia has been shown to result in compassion fatigue, stress-related somatic complaints, work-family conflict, and lower levels of job satisfaction (31, 63–65).

The term “caring–killing paradox,” first coined by Arluke (65), describes the moral challenge of understanding the necessity of euthanasia, but at the same time, having compassion and feelings toward animals. Holding both moral views simultaneously can be challenging at best. Accepting the need to euthanize does not remove the negative feelings many feel toward killing animals. This internal conflict can cause identity-threatening challenges and adversely affects job satisfaction, employee turnover rates, and physical and mental health (63, 66, 67). Further, the negative impact of euthanasia appears greater when those involved are attached to the animals (31, 66). Public perception and the stigma associated with euthanasia can exacerbate these challenges (67). One study exploring the negative emotional impacts of euthanasia within animal shelter employees found a positive effect in following best practices (63).

Depopulation is a unique form of euthanasia typically conducted due to disease (68). Several studies have shown that veterinarians, farmers, producers, and others involved in killing many animals suffer distress and have increased risks of mental health problems (16, 69, 70). Whiting and Marion (16) noted that the reasoning and rationale behind the decision to depopulate are often not sufficient to prevent mental health challenges.

For some people, the stress associated with performing euthanasia or depopulation can cause perpetration-induced traumatic stress (PITS), a type of Post Traumatic Stress Disorder (PTSD) (26, 29). PITS was first identified in American veterans of the Vietnam war, where it was discovered that those who killed humans, or believed their actions resulted in human death, were significantly more likely to experience PTSD than those who had not directly participated in human killing but had witnessed it (25). The mental stress and negative mental health outcome related to the actual perpetration of lethal violence has been confirmed in war and a wide array of settings, including euthanasia and slaughter (26, 71–74). PITS can create anxiety, panic, depression, and a sense of disintegration and dissociation (25). The diagnostic symptoms of PTSD include a significant impact in daily life from one or more intrusion symptoms (e.g., nightmares) linked to the traumatic event, constant avoidance of anything related to the traumatic event, significant changes in mood or cognition associated with the traumatic event, and significant reactivity and alertness.

The current study found a significant relationship between depopulation involvement and burnout, with higher levels of burnout reported by those involved in the depopulation effort. Previous studies have noted the negative psychological impact of participating in depopulation efforts, including a recent analysis by Vroegindewey (75), who reported that 50% of respondents reported immediate behavioral health issues and 32% reported still having symptoms six months after deployment. Furthermore, the depopulation method had a significant impact on burnout and depopulation distress in the form of Ethics of Care and Perception of Others. The distress associated with Ethics of Care concerns the impact on all those involved: the animals as well as the clients, producers, and all those participating in the depopulation event. The decision to depopulate was based on necessity, but as noted earlier, understanding the rationale does not always mitigate the negative emotional effect. The caring-killing paradox is clearly present in these difficult decisions. The distress from the perception of others involves the criticism from the public, friends, family, and colleagues. The anguish of being forced to make difficult depopulation choices was often compounded by a lack of understanding by those not involved. Creating better public messaging to help mitigate this negative compounding effect will be critical in future depopulation efforts.

This research used a survey to garner 134 responses from the AASV membership within the United States to identify the emotional impact of the depopulation crisis during the 2020 COVID-19 events. The survey considered AASV veterinarians involved with depopulation events and those not involved in depopulation events. Survey analysis indicated that the scale and scope of swine veterinary respondents' behavioral health issues are significant, and the findings indicate that further study and actions to improve mental health outcomes associated with depopulation are warranted.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by Colorado State University. The patients/participants provided their written informed consent to participate in this study.

AB and LK were involved with all elements of this study including study design, data analysis and manuscript preparation. All authors contributed to the article and approved the submitted version.

The study was funded by a gift from Merck Animal Health. The funding source did not have involvement beyond the primary authors' active participation.

AB was employed by the company Merck Animal Health. The remaining author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.