A new multiplexed magnetic capture-Droplet digital PCR tool for monitoring wildlife population health and pathogen surveillance

Anthropogenic stressors are exacerbating the emergence and spread of pathogens worldwide. In regions like the Arctic, where ecosystems are particularly susceptible, marked changes are predicted in regional diversity, intensity, and patterns of infectious diseases. To understand such rapidly changing host-pathogen dynamics and mitigate the impacts of novel pathogens, we need sensitive disease surveillance tools. We developed and validated a novel multiplexed, magnetic capture, and ddPCR tool for the surveillance of multiple pathogens in polar bears, a sentinel species that is considered susceptible to climate change and other stressors with a pan-Arctic distribution. Through sequence-specific magnetic capture, we concentrated five target template sequences from three zoonotic bacteria (Erysipelothrix rhusiopathiae, Francisella tularensis, and Mycobacterium tuberculosis complex) and two parasitic (Toxoplasma gondii and Trichinella spp.) pathogens from large quantities (<100 g) of host tissue. We then designed and validated two multiplexed probe-based ddPCR assays for the amplification and detection of the low-concentration target DNA. Validations used 48 polar bear tissues (muscle and liver). We detected 14, 1, 3, 4, and 22 tissue positives for E. rhusiopathiae, F. tularensis, M. tuberculosis complex, T. gondii, and Trichinella spp., respectively. These multiplexed assays offer a rapid, specific tool for quantifying and monitoring the changing geographical and host distributions of pathogens relevant to human and animal health.

An exploratory spatial contaminant assessment for polar bear (Ursus maritimus) liver, fat, and muscle from northern Canada

Since the industrial era, chemicals have been ubiquitous in worldwide ecosystems. Despite the discontinued release of highly toxic persistent organic pollutants (POPs) in the environment, the levels of some POPs are still being measured in the Canadian Arctic. These contaminants are of great concern due to their persistence, toxicity, and levels of bioaccumulation in food chains. Animals occupying top trophic positions in the Canadian Arctic, particularly polar bears, are exposed to these contaminants mainly through their diet. Our study investigated the levels of 30 metals (including total and methyl mercury) alkaline and alkaline earth metals, 15 polycyclic aromatic compounds and their alkyl congeners (PACs), 6 chlordanes (CHLs), and 20 polychlorinated biphenyls (PCBs), in 49 polar bears from the Canadian Arctic. Contaminant burden was measured in liver, muscle, and fat in bears of different sex, age, and locations. A principal component analysis did not distinguish differences between age and sex profiles for most contaminants. However, the concentrations measured and their distribution in the tissues confirm findings observed in past studies. This study highlights the importance of continual monitoring of polar bear health (e.g., newly detected PACs were measured within this study) and evaluating those impacts for the next generations of polar bears.

Genotyping-in-thousands by sequencing (GT-seq) of non-invasive fecal and degraded samples: a new panel to enable ongoing monitoring of Canadian polar bear populations

Genetic monitoring using noninvasive samples provides a complement or alternative to traditional population monitoring methods. However, next‐generation sequencing approaches to monitoring typically require high quality DNA and the use of noninvasive samples (e.g., scat) is often challenged by poor DNA quality and contamination by nontarget species. One promising solution is a highly multiplexed sequencing approach called genotyping‐in‐thousands by sequencing (GT‐seq), which can enable cost‐efficient genomics‐based monitoring for populations based on noninvasively collected samples. Here, we develop and validate a GT‐seq panel of 324 single nucleotide polymorphisms (SNPs) optimized for genotyping of polar bears based on DNA from noninvasively collected faecal samples. We demonstrate (1) successful GT‐seq genotyping of DNA from a range of sample sources, including successful genotyping (>50% loci) of 62.9% of noninvasively collected faecal samples determined to contain polar bear DNA; and (2) that we can reliably differentiate individuals, ascertain sex, assess relatedness, and resolve population structure of Canadian polar bear subpopulations based on a GT‐seq panel of 324 SNPs. Our GT‐seq data reveal spatial‐genetic patterns similar to previous polar bear studies but at lesser cost per sample and through use of noninvasively collected samples, indicating the potential of this approach for population monitoring. This GT‐seq panel provides the foundation for a noninvasive toolkit for polar bear monitoring and can contribute to community‐based programmes – a framework which may serve as a model for wildlife conservation and management for species worldwide.

A novel mark-recapture-recovery survey using genetic sampling for polar bears Ursus maritimus in Baffin Bay

Changes in sea-ice dynamics are affecting polar bears Ursus maritimus across their circumpolar range, which highlights the importance of periodic demographic assessments to inform management and conservation. We used genetic mark-recapture-recovery to derive estimates of abundance and survival for the Baffin Bay (BB) polar bear subpopulation—the first time this method has been used successfully for this species. Genetic data from tissue samples we collected via biopsy darting were combined with historical physical capture and harvest recovery data. The combined data set consisted of 1410 genetic samples (2011-2013), 914 physical captures (1993-1995, 1997), and 234 harvest returns of marked bears (1993-2013). The estimate of mean subpopulation abundance was 2826 (95% CI = 2284-3367) in 2012-2013. Estimates of annual survival (mean ± SE) were 0.90 ± 0.05 and 0.78 ± 0.06 for females and males age ≥2 yr, respectively. The proportion of total mortality of adult females and males that was attributed to legal harvest was 0.16 ± 0.05 and 0.26 ± 0.06, respectively. Remote sensing sea-ice data, telemetry data, and spatial distribution of onshore sampling indicated that polar bears were more likely to use offshore sea-ice habitat during the 1990s sampling period compared to the 2010s. Furthermore, in the 1990s, sampling of deep fjords and inland areas was limited, and no offshore sampling occurred in either time period, which precluded comparisons of abundance between the 1993-1997 and 2011-2013 study periods. Our findings demonstrate that genetic sampling can be a practical method for demographic assessment of polar bears over large spatial and temporal scales.

Transient benefits of climate change for a high-Arctic polar bear (Ursus maritimus) subpopulation

Kane Basin (KB) is one of the world's most northerly polar bear (Ursus maritimus) subpopulations, where bears have historically inhabited a mix of thick multiyear and annual sea ice year-round. Currently, KB is transitioning to a seasonally ice-free region because of climate change. This ecological shift has been hypothesized to benefit polar bears in the near-term due to thinner ice with increased biological production, although this has not been demonstrated empirically. We assess sea-ice changes in KB together with changes in polar bear movements, seasonal ranges, body condition, and reproductive metrics obtained from capture-recapture (physical and genetic) and satellite telemetry studies during two study periods (1993-1997 and 2012-2016). The annual cycle of sea-ice habitat in KB shifted from a year-round ice platform (~50% coverage in summer) in the 1990s to nearly complete melt-out in summer (<5% coverage) in the 2010s. The mean duration between sea-ice retreat and advance increased from 109 to 160 days (p = .004). Between the 1990s and 2010s, adult female (AF) seasonal ranges more than doubled in spring and summer and were significantly larger in all months. Body condition scores improved for all ages and both sexes. Mean litter sizes of cubs-of-the-year (C0s) and yearlings (C1s), and the number of C1s per AF, did not change between decades. The date of spring sea-ice retreat in the previous year was positively correlated with C1 litter size, suggesting smaller litters following years with earlier sea-ice breakup. Our study provides evidence for range expansion, improved body condition, and stable reproductive performance in the KB polar bear subpopulation. These changes, together with a likely increasing subpopulation abundance, may reflect the shift from thick, multiyear ice to thinner, seasonal ice with higher biological productivity. The duration of these benefits is unknown because, under unmitigated climate change, continued sea-ice loss is expected to eventually have negative demographic and ecological effects on all polar bears.

Language barriers in HRQOL assessment: development of a picture-based questionnaire (PictoQOL)

Background

Translations and adaptations of standardized HRQOL questionnaires (e.g., SF-8) are available for many large population groups. For smaller groups, like certain migrant communities, whose language use can differ from the respective population in their countries of origin, often no adequate adaptations are available. Nonverbal, picture-based questionnaires could address these challenges. The present study provides insights into the development of such a measure (PictoQOL) for HRQOL assessment.

Methods

We used a qualitative design. We conducted 6 focus group discussions with a total of 18 adults from different cultural backgrounds to identify suitable visual cues based on the the dimensions of the SF-8 and WHOQOL-BREF and to create drafts of visual representations for different items. Subsequently, we developed a draft of the questionnaire and further revised it according to findings from 45 cognitive interviews, based on a think aloud and verbal probing approach.

Results

Preferred visual representations and understanding of pictorial elements differed between participants from different cultural backgrounds. Simpler concepts were considered easier to understand than compounded concepts. Preferences in element style and composition were similar between the groups. In addition, using a recurring character was considered helpful for identification.

Conclusions

In the development of the PictoQOL, decisions concerning style and composition of pictorial elements were culture-independent. In contrast, preferences of visual representations of abstract concepts were strongly dependent on cultural aspects, confirming the need of a participatory approach to develop the measure. The PictoQOL is likely to be comprehensible cross-culturally without further need of adaptation.

Key messages

To ensure cross-cultural comprehensibility development of a picture-based questionnaire, a participatory approach to development is necessary. The PictoQOL is suitable to measure health-related quality of life in understudied, culturally diverse populations.

Interrelated ecological impacts of climate change on an apex predator

Climate change has broad ecological implications for species that rely on sensitive habitats. For some top predators, loss of habitat is expected to lead to cascading behavioral, nutritional, and reproductive changes that ultimately accelerate population declines. In the case of the polar bear (Ursus maritimus), declining Arctic sea ice reduces access to prey and lengthens seasonal fasting periods. We used a novel combination of physical capture, biopsy darting, and visual aerial observation data to project reproductive performance for polar bears by linking sea ice loss to changes in habitat use, body condition (i.e., fatness), and cub production. Satellite telemetry data from 43 (1991-1997) and 38 (2009-2015) adult female polar bears in the Baffin Bay subpopulation showed that bears now spend an additional 30 d on land (90 d in total) in the 2000s compared to the 1990s, a change closely correlated with changes in spring sea ice breakup and fall sea ice formation. Body condition declined for all sex, age, and reproductive classes and was positively correlated with sea ice availability in the current and previous year. Furthermore, cub litter size was positively correlated with maternal condition and spring breakup date (i.e., later breakup leading to larger litters), and negatively correlated with the duration of the ice-free period (i.e., longer ice-free periods leading to smaller litters). Based on these relationships, we projected reproductive performance three polar bear generations into the future (approximately 35 yr). Results indicate that two-cub litters, previously the norm, could largely disappear from Baffin Bay as sea ice loss continues. Our findings demonstrate how concurrent analysis of multiple data types collected over long periods from polar bears can provide a mechanistic understanding of the ecological implications of climate change. This information is needed for long-term conservation planning, which includes quantitative harvest risk assessments that incorporate estimated or assumed trends in future environmental carrying capacity.

Canadian polar bear population structure using genome-wide markers

Predicting the consequences of environmental changes, including human-mediated climate change on species, requires that we quantify range-wide patterns of genetic diversity and identify the ecological, environmental, and historical factors that have contributed to it. Here, we generate baseline data on polar bear population structure across most Canadian subpopulations (n = 358) using 13,488 genome-wide single nucleotide polymorphisms (SNPs) identified with double-digest restriction site-associated DNA sequencing (ddRAD). Our ddRAD dataset showed three genetic clusters in the sampled Canadian range, congruent with previous studies based on microsatellites across the same regions; however, due to a lack of sampling in Norwegian Bay, we were unable to confirm the existence of a unique cluster in that subpopulation. These data on the genetic structure of polar bears using SNPs provide a detailed baseline against which future shifts in population structure can be assessed, and opportunities to develop new noninvasive tools for monitoring polar bears across their range.

The use of hair as a proxy for total and methylmercury burdens in polar bear muscle tissue

Polar bears (Ursus maritimus) are an ecologically important species in the Arctic, whose health, and that of the people whose livelihoods depend on them, are increasingly affected by climate change and the bioaccumulation of contaminants such as mercury (Hg). Although methylmercury (MeHg) is the toxic form of Hg that biomagnifies up food webs, risk assessment studies typically only report on total Hg (THg) concentrations because it is cheaper to quantify. Furthermore, hair is commonly analysed for THg in polar bear as well as human risk assessment studies because it is relatively non-invasive to collect, yet we know little of how THg and MeHg concentrations differ between hair and muscle tissues. In this study, we quantified THg and MeHg concentrations in hair and muscle from 44 polar bears (24 sub-adults: 9 females, 15 males; 18 adults: 5 females, 13 males, and 2 males of unknown age group), harvested in 2015 and 2016 from four subpopulations in Nunavut, Canada (Davis Strait, n = 3; Gulf of Boothia, n = 8; Baffin Bay, n = 15; Foxe Basin, n = 18). We found only moderately positive correlations (0.4 ≤ r ≤ 0.5) between THg concentrations in hair and THg and MeHg concentrations in muscle. Further, 75% and 88% of THg was MeHg in hair and muscle, respectively. High concentrations of THg in hair - 71% of the samples were above the suggested neurochemical no observed effect level for polar bears - suggest some of the bears may be adversely affected by Hg-related health effects. Despite this, all MeHg concentrations in muscle (0.1 to 0.4 mg/kg (wet weight, ww)) were below the consumption maximum Hg concentration of 0.5 mg/kg (ww) set by Canadian health authorities.

Concentrations of legacy and new contaminants are related to metabolite profiles in Hudson Bay polar bears

There are very few metabolomics assessments based on field accumulated, uncontrolled contaminant exposures in wildlife, particularly in the Arctic. In the present study, targeted metabolomics and contaminant data were analyzed together to assess potential influences of contaminant exposure on the hepatic metabolome of male polar bears (n = 29) from the southern and western Hudson Bay (SHB and WHB respectively), Canada. The 29 metabolites identified as important in the differentiation of the two subpopulations after partial least squares discriminant analysis (PLS-DA) included phosphatidylcholines (PCs), acylcarnitines (ACs; involved in β-oxidation of fatty acids), and the fatty acid (FA) arachidonic acid (ARA). Perfluorinated alkyl substances, polybrominated diphenyl ethers, dichlorodiphenyldichloroethylene (p,p'-DDE) and some highly chlorinated ortho-polychlorinated biphenyl congeners were greater in the SHB bears and were consistently inversely correlated with discriminating ACs and PCs between the subpopulations. The concentrations of discriminatory, legacy organochlorine pesticides along with one tetrachlorobiphenyl were greater in the WHB and were directly correlated with the VIP-identified ACs and PCs. ARA, glycerophospholipid and several amino acid metabolic pathways were identified as different between subpopulations and/or were impacted. ARA is an important, conditionally essential, dietary n-6 FA and is also part of the inflammation response, and elevated concentrations in the SHB could be related to differences in chronic contaminant exposure and/or differences in diet and/or season, among a number of possible explanations. Dietary tracers (stable isotopes of carbon and nitrogen) were correlated with some discriminatory metabolites, supporting the hypothesis that dietary variation was also an important factor in the differentiation of the subpopulations. The results suggest linkages between contaminant exposure in Hudson Bay polar bears and elements of the hepatic metabolome, particularly those related to lipid metabolism.

Persistent organic pollutants and penile bone mineral density in East Greenland and Canadian polar bears (Ursus maritimus) during 1996-2015

Persistent organic pollutants (POPs) are long-range transported to the Arctic via atmospheric and oceanic currents, where they biomagnify to high concentrations in the tissues of apex predators such as polar bears (Ursus maritimus). A major concern of POP exposure is their physiological effects on vital organ-tissues posing a threat to the health and survival of polar bears. Here we examined the relationship between selected POPs and baculum bone mineral density (BMD) in the East Greenland and seven Canadian subpopulations of polar bears. BMD was examined in 471 bacula collected between years 1996-2015 while POP concentrations in adipose tissue were determined in 67-192 of these individuals collected from 1999 to -2015. A geographical comparison showed that baculum BMD was significantly lowest in polar bears from East Greenland (EG) when compared to Gulf of Boothia (GB), Southern Hudson (SH) and Western Hudson (WH) Bay subpopulations (all p < 0.05). The calculation of a T-score osteoporosis index for the EG subpopulation using WH bears as a reference group gave a T-score of -1.44 which indicate risk of osteopenia. Concentrations of ΣPCB₇₄ (polychlorinated biphenyls), ΣDDT₃ (dichlorodiphenyltrichloroethanes), p,p'-DDE (dichlorodiphenyldichloroethylene), ΣHCH₃ (hexachlorohexane) and α-HCH was significantly highest in EG bears while ΣPBDE (polybrominated diphenyl ethers), BDE-47 and BDE-153 was significantly highest in SH bears (all p < 0.04). Statistical analyses of individual baculum BMD vs. POP concentrations showed that BMD was positively correlated with ΣPCB₇₄, CB-153, HCB (hexachlorobenzene), ΣHCH, β-HCH, ClBz (chlorobenzene), ΣPBDE and BDE-153 (all p < 0.03). In conclusion, baculum density was significantly lowest in East Greenland polar bears despite the positive statistical correlations of BMD vs. POPs. Other important factors such as nutritional status, body mass and body condition was not available for the statistical modelling. Since on-going environmental changes are known to affect these, future studies need to incorporate nutritional, endocrine and genetic parameters to further understand how POP exposure may disrupt bone homeostasis and affect baculum BMD across polar bear subpopulations.

Range contraction and increasing isolation of a polar bear subpopulation in an era of sea-ice loss

Climate change is expected to result in range shifts and habitat fragmentation for many species. In the Arctic, loss of sea ice will reduce barriers to dispersal or eliminate movement corridors, resulting in increased connectivity or geographic isolation with sweeping implications for conservation. We used satellite telemetry, data from individually marked animals (research and harvest), and microsatellite genetic data to examine changes in geographic range, emigration, and interpopulation connectivity of the Baffin Bay (BB) polar bear (Ursus maritimus) subpopulation over a 25-year period of sea-ice loss. Satellite telemetry collected from n = 43 (1991-1995) and 38 (2009-2015) adult females revealed a significant contraction in subpopulation range size (95% bivariate normal kernel range) in most months and seasons, with the most marked reduction being a 70% decline in summer from 716,000 km2 (SE 58,000) to 211,000 km2 (SE 23,000) (p < .001). Between the 1990s and 2000s, there was a significant shift northward during the on-ice seasons (2.6° shift in winter median latitude, 1.1° shift in spring median latitude) and a significant range contraction in the ice-free summers. Bears in the 2000s were less likely to leave BB, with significant reductions in the numbers of bears moving into Davis Strait (DS) in winter and Lancaster Sound (LS) in summer. Harvest recoveries suggested both short and long-term fidelity to BB remained high over both periods (83-99% of marked bears remained in BB). Genetic analyses using eight polymorphic microsatellites confirmed a previously documented differentiation between BB, DS, and LS; yet weakly differentiated BB from Kane Basin (KB) for the first time. Our results provide the first multiple lines of evidence for an increasingly geographically and functionally isolated subpopulation of polar bears in the context of long-term sea-ice loss. This may be indicative of future patterns for other polar bear subpopulations under climate change.

Legacy and new halogenated persistent organic pollutants in polar bears from a contamination hotspot in the Arctic, Hudson Bay Canada

A large and complex suite of 295 legacy and new halogenated persistent organic pollutants (POPs) were investigated in fat or liver tissue samples of polar bears collected in 2013-2014 from Southern (SHB) and Western (WHB) subpopulations of the Canadian Arctic contaminants hotspot of Hudson Bay. A total of 210 POPs were detected and/or quantifiable with some frequency in all fat or liver samples. POP profile and concentration differences were investigated both within (e.g. age and sex) and between the two subpopulations. Two time-point comparisons were made relative to POPs reported for Hudson Bay polar bears harvested in 2007-2008. ΣPolychlorinated biphenyl (PCB) concentrations at both time points were the most concentrated of the POP groups, and were spatially uniform with no detectable influence of sex or age, as were concentrations of the dominant congener CB153. ΣChlordanes (ΣCHLs, 74-79% oxychlordane) and the Σperfluoroalkyl substances (ΣPFASs, ≈60% perfluorooctane sulfonate (PFOS)) had the second greatest POP group concentrations in SHB and WHB respectively, with ΣPFASs and ΣCHLs being significantly influenced by age and/or sex. ΣCHLs were spatially uniform but ΣPFASs were greater in the SHB bears, as were e.g. some flame retardants, due to e.g. local contamination and/or changes in bear behavior and diet. Endosulfans and hexabromocyclododecane were detectable in samples from 2007-2008 but not from 2013-2014, which is consistent with their global POP regulations. ΣPolychlorinated naphthalenes (ΣPCNs) were consistently detected at relatively high concentrations compared to other arctic wildlife, however these concentrations were low relative to legacy POPs. ΣShort-chain chlorinated paraffins (ΣSCCPs) were major contributors to the overall POPs burden with concentrations comparable to other legacy POPs, though there was no significant difference between or within subpopulations for PCNs or SCCPs. Except for octachlorostyrene, POPs concentrations were generally lower in female and male bears from SHB in 2013-2014 relative to 2007-2008, however those of WHB males were greater over the same timeframe for almost all POPs.

Penile density and globally used chemicals in Canadian and Greenland polar bears

Industrially produced chemicals have been a major environmental concern across our entire Globe since the onset of rapid industrial development around the early 1900. Many of the substances being used are known to be endocrine disrupting chemicals (EDCs) and are also known to be long-range dispersed and to biomagnify to very high concentrations in the tissues of Arctic apex predators such as polar bears (Ursus maritimus). A major concern relating to EDCs is their effects on vital organ-tissues such as bone and it is possible that EDCs represent a more serious challenge to the species' survival than the more conventionally proposed prey reductions linked to climate change. We therefore analyzed penile bone mineral density (BMD) as a key phenotype for reproductive success in 279 polar bear samples born 1990-2000 representing eight polar bear subpopulations. Since EDC concentrations were not available from the same specimens, we compared BMD with published literature information on EDC concentrations. Latitudinal and longitudinal BMD and EDC gradients were clearly observed, with Western Hudson bears having the highest BMD and lowest EDCs, and North East Greenland polar bears carrying the lowest BMD and highest EDCs. A BMD vs. polychlorinated biphenyls (PCB) regression analysis showed that BMD decreased as a function of the eight subpopulations' PCB concentrations and this relationship was close to being significant (p=0.10, R(2)=0.39). Risk quotient (RQ) estimation demonstrated that PCBs could be in a range that may lead to disruption of normal reproduction and development. It is therefore likely that EDCs directly affect development and bone density in polar bears. Canadian bears had in general the best health and the North East Greenland subpopulation being at the highest risk of having negative health effects. While reductions in BMD is in general unhealthy, reductions in penile BMD could lead to increased risk of species extinction because of mating and subsequent fertilization failure as a result of weak penile bones and risk of fractures. Based on this, future studies should assess how polar bear subpopulations respond upon EDC exposure since information and understanding about their circumpolar reproductive health is vital for future conservation.

Negative bias in fast emotion discrimination in borderline personality disorder

BACKGROUND

The ability to decode emotional information from facial expressions is crucial for successful social interaction. Borderline personality disorder (BPD) is characterized by serious problems in interpersonal relationships and emotional functioning. Empirical research on facial emotion recognition in BPD has been sparsely published and results are inconsistent. To specify emotion recognition deficits in BPD more closely, the present study implemented two emotion recognition tasks differing in response format.

METHOD

Nineteen patients with BPD and 19 healthy subjects were asked to evaluate the emotional content of visually presented stimuli (emotional and neutral faces). The first task, the Fear Anger Neutral (FAN) Test, required a rapid discrimination between negative or neutral facial expressions whereas in the second task, the Emotion Recognition (ER) Test, a precise decision regarding default emotions (sadness, happiness, anger, fear and neutral) had to be achieved without a time limit.

RESULTS

In comparison to healthy subjects, BPD patients showed a deficit in emotion recognition only in the fast discrimination of negative and neutral facial expressions (FAN Test). Consistent with earlier findings, patients demonstrated a negative bias in the evaluation of neutral facial expressions. When processing time was unlimited (ER Test), BPD patients performed as well as healthy subjects in the recognition of specific emotions. In addition, an association between performance in the fast discrimination task (FAN Test) and post-traumatic stress disorder (PTSD) co-morbidity was indicated.

CONCLUSIONS

Our data suggest a selective deficit of BPD patients in rapid and direct discrimination of negative and neutral emotional expressions that may underlie difficulties in social interactions.

Risk factors for antimicrobial resistance among fecal Escherichia coli from residents on forty-three swine farms

Fecal Escherichia coli (n = 555) were isolated from 115 residents on 43 farrow-to-finish swine farms to determine the prevalence of antimicrobial resistance and associated risk factors. Susceptibility to 21 antimicrobials was determined and the overall prevalence of antimicrobial resistance was 25.8%. Pair-wise difference in prevalences of resistance to individual antimicrobials was significant between isolates from residents on farms that fed medicated swine rations compared to those that did not (p = 0.013). Cross-resistance among antimicrobials of same class and multidrug-resistance were observed. Logistic regression models revealed the following risk factors positively associated with antimicrobial resistance: use of antimicrobials in pigs on farms; number of hours per week that farmers spent in their pig barns; handling of sick pigs; and intake of antimicrobials by farm residents. This study indicates that occupational exposure of farmers to resistant bacteria and use of antimicrobials in pig farming may constitute a source of resistance in humans, although the human health impacts of such resistance is unknown. The consumption of antimicrobials by farmers appeared to constitute a significant risk for resistance development. Fecal E. coli from farm residents may act as a reservoir of resistance genes for animal and/or human pathogens.