Concurrent Hepatitis C and B Virus and Human Immunodeficiency Virus Infections Are Associated With Higher Mortality Risk Illustrating the Impact of Syndemics on Health Outcomes.

BACKGROUND: Hepatitis C virus (HCV), hepatitis B virus (HBV), and human immunodeficiency virus (HIV) infections are associated with significant mortality globally and in North America. However, data on impact of concurrent multiple infections on mortality risk are limited. We evaluated the effect of HCV, HBV, and HIV infections and coinfections and associated factors on all-cause mortality in British Columbia (BC), Canada. METHODS: The BC Hepatitis Testers Cohort includes ~1.7 million individuals tested for HCV or HIV, or reported as a case of HCV, HIV, or HBV from 1990 to 2015, linked to administrative databases. We followed people with HCV, HBV, or HIV monoinfection, coinfections, and triple infections from their negative status to date of death or December 31, 2016. Extended Cox proportional hazards regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for factors associated with all-cause mortality. RESULTS: Of 658 704 individuals tested for HCV, HBV, and HIV, there were 33 804 (5.13%) deaths. In multivariable Cox regression analysis, individuals with HCV/HBV/HIV (HR, 8.9; 95% CI, 8.2-9.7) infections had the highest risk of mortality followed by HCV/HIV (HR, 4.8; 95% CI, 4.4-5.1), HBV/HIV (HR, 4.1; 95% CI, 3.5-4.8), HCV/HBV (HR, 3.9; 95% CI, 3.7-4.2), HCV (HR, 2.6; 95% CI, 2.6-2.7), HBV (HR, 2.2; 95% CI, 2.0-2.3), and HIV (HR, 1.6; 95% CI, 1.5-1.7). Additional factors associated with mortality included injection drug use, problematic alcohol use, material deprivation, diabetes, chronic kidney disease, heart failure, and hypertension. CONCLUSIONS: Concurrent multiple infections are associated with high mortality risk. Substance use, comorbidities, and material disadvantage were significantly associated with mortality independent of coinfection. Preventive interventions, including harm reduction combined with coinfection treatments, can significantly reduce mortality.

Accuracy of Blood Transfusion Records in a Population-based Perinatal Data Registry.

BACKGROUND: Blood transfusion is frequently used as an indicator of severe maternal morbidity during pregnancy. However, few studies have examined its validity in population perinatal databases. METHODS: We linked a perinatal database from British Columbia, Canada, with the province's Central Transfusion Registry for 2004-2015 deliveries. Using the Central Transfusion Registry records for red blood cell transfusion as the gold standard, we calculated the sensitivity, specificity, positive predictive value, and negative predictive value of the perinatal database variable for red blood cell transfusion, overall and by transfusion risk factor status. We used multivariable logistic regression to examine whether outcome misclassification altered the odds ratios for different transfusion risk factors. RESULTS: Among 473,688 deliveries, 4,033 (8.5 per 1,000) had a red blood cell transfusion according to the Central Transfusion Registry. The sensitivity of the perinatal database transfusion variable was 72.3 [95% confidence interval (CI) = 72.2, 72.4]. Sensitivity differed according to the presence of many transfusion risk factors (e.g., 84.9% vs. 72.2% in deliveries with versus without uterine rupture). Odds ratios associated with some transfusion risk factors were exaggerated when the perinatal database transfusion variable was used to define the outcome instead of the Central Transfusion Registry variable, but 95% confidence intervals for these estimates overlapped. CONCLUSION: Blood transfusion was documented with reasonable sensitivity in this large population perinatal database. However, validity varied according to risk factor status. Our findings enable researchers to better account for outcome misclassification in studies of obstetrical transfusion risk factors.

The population level care cascade for hepatitis C in British Columbia, Canada as of 2018: Impact of direct acting antivirals.

BACKGROUND: Population-level monitoring of hepatitis C virus (HCV) infected people across cascades of care identifies gaps in access and engagement in care and treatment. We characterized the population-level care cascade for HCV in British Columbia (BC), Canada before and after introduction of Direct Acting Antiviral (DAA) treatment. METHODS: BC Hepatitis Testers Cohort (BC-HTC) includes 1.7 million individuals tested for HCV, HIV, reported cases of hepatitis B, and active tuberculosis in BC from 1990 to 2018 linked to medical visits, hospitalizations, cancers, prescription drugs and mortality data. We defined six HCV care cascade stages: (a) antibody diagnosed; (b) RNA tested; (c) RNA positive; (d) genotyped; (e) initiated treatment; and (f) achieved sustained virologic response (SVR). RESULTS: We estimated 61 127 people were HCV antibody positive in BC in 2018 (undiagnosed: 7686, 13%; diagnosed: 53 441, 87%). Of those diagnosed, 83% (44 507) had HCV RNA testing, and of those RNA positive, 90% (28 716) were genotyped. Of those genotyped, 61% (17 441) received therapy, with 90% (15 672) reaching SVR. Individuals from older birth cohorts had lower progression to HCV RNA testing. While people who currently inject drugs had the highest proportional progression to RNA testing, this group had the lowest proportional treatment uptake. CONCLUSIONS: Although gaps in HCV RNA and genotype testing after antibody diagnosis exist, the largest gap in the care cascade is treatment initiation, despite introduction of DAA treatment and removal of treatment eligibility restrictions. Further interventions are required to ensure testing and treatment is equitably accessible in BC.

Effectiveness of Ledipasvir/Sofosbuvir and Sofosbuvir/Velpatasvir in People Who Inject Drugs and/or Those in Opioid Agonist Therapy.

We evaluated the effectiveness of ledipasvir/sofosbuvir (LDV/SOF) in treating hepatitis C virus (HCV) genotype 1 and SOF/velpatasvir (SOF/VEL) for all genotypes among people who inject drugs (PWID) and those not injecting drugs and who were on or off opioid agonist therapy (OAT). Study participants comprised a population-based cohort in British Columbia, Canada. The British Columbia Hepatitis Testers Cohort includes data on individuals tested for HCV from 1990 to 2016 that are integrated with medical visits, hospitalization, and prescription drug data. We classified study participants as off OAT/recent injection drug use (off-OAT/RIDU), off OAT/past IDU (off-OAT/PIDU), off OAT/no IDU (off-OAT/NIDU), on OAT/IDU (on-OAT/IDU), and on OAT/no IDU (on-OAT/NIDU). We assessed sustained virologic response (SVR) 10 weeks after HCV treatment among study groups treated with LDV/SOF or SOF/VEL until January 13, 2018. Analysis included 5,283 eligible participants: 390 off-OAT/RIDU, 598 off-OAT/PIDU, 3,515 off-OAT/NIDU, 609 on-OAT/IDU, and 171 on-OAT/NIDU. The majority were male patients (64%-74%) and aged ≥50 years (58%-85%). The SVRs for off-OAT/RIDU, off-OAT/PIDU, off-OAT/NIDU, on-OAT/IDU, and on-OAT/NIDU were 91% (355/390), 95% (570/598), 96% (3,360/3,515), 93% (567/609), and 95% (163/171), respectively. Among those with no SVR, 14 individuals died while on treatment or before SVR assessment, including 4 from illicit drug overdose. In the overall multivariable model, off-OAT/RIDU, on-OAT/IDU, male sex, cirrhosis, treatment duration <8 weeks, treatment duration 8 weeks, and treatment with SOF/VEL were associated with not achieving SVR. Conclusion: In this large real-world cohort, PWID and/or those on OAT achieved high SVRs, although slightly lower than people not injecting drugs. This finding also highlights the need for additional measures to prevent loss to follow-up and overdose-related deaths among PWID.

Impact of SSO-ASTRO margin guidelines on reoperation rates following breast-conserving surgery.

BACKGROUND: Re-operation rates following breast-conserving surgery (BCS) for early invasive breast cancer are highly variable, largely due to uncertainty regarding adequate margins. The 2014 SSO-ASTRO guidelines recommended "no ink on tumor" as adequate margins. We evaluated the effect of guideline implementation on re-operation following BCS at our regional cancer center. METHODS: Retrospective chart review was performed on records for patients with early invasive breast carcinoma undergoing BCS between February 2011 and May 2017. Time period, pathologic margin status, patient and tumor characteristics were assessed for their impact on re-operation rates. RESULTS: Overall re-operation rate decreased following the guidelines release (OR 0.28, 95% C.I. 0.15-0.51, p = <0.0001), with an unadjusted decrease of 3.89%. Re-operations on both close (OR 0.17, 95% C.I. 0.07-0.40, p = <0.0001) and widely negative (OR 0.20, 95% C.I. 0.05-0.77, p = 0.02) margins decreased in the post-guidelines time period. CONCLUSION: SSO-ASTRO margins guideline release was associated with decreased re-operation. Furthermore, re-operations rates decreased in patients with pathologically negative margins, the target population the guidelines were meant to address.

Interprovincial variation in pre-pregnancy body mass index and gestational weight gain and their impact on neonatal birth weight with respect to small and large for gestational age.

OBJECTIVES: To explore provincial variation in both excess and inadequate pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) and their impact on small- and large-for-gestational-age (SGA, LGA) infants. METHODS: Four provinces with a perinatal database capturing the required exposures participated: British Columbia (BC), Ontario (ON), Nova Scotia (NS), and Newfoundland and Labrador (NL). In multiple, concurrent retrospective studies, we included women ≥ 19 years, who gave birth from 22+0 to 42+6 weeks' gestation, to a live singleton from April 2013-March 2014. From adjusted odds ratios, we calculated population attributable fractions (PAF) of SGA and LGA for BMI and GWG. RESULTS: The proportion of overweight and obese women increased from western to eastern Canada. In BC, ON, NS, and NL, the proportions of women who were overweight were 21.1%, 24.0%, 23.7%, and 25.4%, while obesity proportions were 14.2%, 18.1%, 24.2%, and 29.8%, respectively. Excess GWG affected 53.9%, 49.9%, 57.6%, and 65.6% of women, respectively. Excess GWG contributed to 29.5-42.5% of LGA, compared with the PAFs for overweight (6.8-12.0%) and obesity (13.2-20.6%). Inadequate GWG's contribution to SGA (4.8-12.3%) was higher than underweight BMI's (2.9-6.2%). CONCLUSION: In this interprovincial study, high and increasing proportions of women from west to east had excess pre-pregnancy BMI, and between half to two thirds had excess GWG. The contributions of GWG outside of recommendations to SGA and LGA were greater than that of low or high BMI. GWG is a potentially modifiable determinant of SGA and LGA across Canada.

Hepatitis C virus reinfection after successful treatment with direct-acting antiviral therapy in a large population-based cohort.

BACKGROUND & AIMS: Direct-acting antiviral therapies (DAA) are an important tool for hepatitis C virus (HCV) elimination. However, reinfection among people who inject drugs (PWID) may hamper elimination targets. Therefore, we estimated HCV reinfection rates among DAA-treated individuals, including PWID. METHODS: We analyzed data from the British Columbia Hepatitis Testers Cohort which included ∼1.7 million individuals screened for HCV in British Columbia, Canada. We followed HCV-infected individuals treated with DAAs who achieved a sustained virologic response (SVR) and had ≥1 subsequent HCV RNA measurement to April 22nd, 2018. Reinfection was defined as a positive RNA measurement after SVR. PWID were identified using a validated algorithm and classified based on recent (<3 years) or former (≥3 years before SVR) use. Crude reinfection rates per 100 person-years (PYs) were calculated. Poisson regression was used to model adjusted incidence rate ratios (IRRs) and 95% CIs. RESULTS: Of 4,114 individuals who met the inclusion criteria, most were male (n = 2,692, 65%), born before 1965 (n = 3,411, 83%) and were either recent (n = 875, 21%) or former PWID (n = 1,793, 44%). Opioid-agonist therapy (OAT) was received by 19% of PWID. We identified 40 reinfections during 2,767 PYs. Reinfection rates were higher among recent (3.1/100 PYs; IRR 6.7; 95% CI 1.9-23.5) and former PWID (1.4/100 PYs; IRR 3.7; 95% CI 1.1-12.9) than non-PWID (0.3/100 PYs). Among recent PWID, reinfection rates were higher among individuals born after 1975 (10.2/100 PYs) and those co-infected with HIV (5.7/100 PYs). Only one PWID receiving daily OAT developed reinfection. CONCLUSIONS: Population-level reinfection rates remain elevated after DAA therapy among PWID because of ongoing exposure risk. Engagement of PWID in harm-reduction and support services is needed to prevent reinfections. LAY SUMMARY: Direct-acting antivirals are an effective tool for the treatment of hepatitis C virus, enabling the elimination of the virus. However, some patients who have been successfully treated with direct-acting antivirals are at risk of reinfection. Our findings showed that the risk of reinfection was highest among people with recent injection drug use. Among people who inject drugs, daily use of opioid-agonist therapy was associated with a lower risk of reinfection.

Differing profiles of people diagnosed with acute and chronic hepatitis B virus infection in British Columbia, Canada.

AIM: To describe the characteristics of people diagnosed with acute and chronic hepatitis B virus (HBV) infection in British Columbia (BC). METHODS: We used data from the BC Hepatitis Testers Cohort (BC-HTC), which includes all individuals tested for hepatitis C virus (HCV) or human immunodeficiency virus (HIV) or those diagnosed with HBV or active tuberculosis in BC since 1990. These data were integrated with prescription drug, medical visit, hospitalization and mortality data. HBV cases were classified as acute or chronic according to provincial guidelines. We compared characteristics of individuals by HBV infection group (acute, chronic and negative). Factors associated with acute or chronic HBV infection were assessed with multinomial logistic regression models in comparison to the HBV negative group. RESULTS: 46498 of the 1058056 eligible BC-HTC participants were diagnosed with HBV infection. 4.3% of HBV positive individuals were diagnosed with acute HBV infections while 95.7% had chronic infections. Problematic alcohol use, injection drug use, and HIV or HCV co-infection were more common among individuals diagnosed with acute HBV compared to those with chronic infections and HBV negative individuals. In multivariable multinomial logistic regression models, we observed significant associations between acute or chronic HBV diagnosis and being male, age at HBV diagnosis or birth cohort, South and East Asian ethnicity, HCV or HIV infection, and injection drug use. The odds of acute HBV decreased with increasing age among people who inject drugs, while the opposite was true for chronic HBV. Persons with acute HBV were predominantly White (78%) while those with chronic HBV were mostly East Asian (60%). Relative to Whites, East Asians had 12 times greater odds of being diagnosed with chronic HBV infection. These odds increased with increasing socioeconomic deprivation. CONCLUSION: Differences in the profiles of people diagnosed with acute and chronic HBV infection necessitate differentiated screening, prevention, care and treatment programs.

Identifying injection drug use and estimating population size of people who inject drugs using healthcare administrative datasets.

BACKGROUND: Large linked healthcare administrative datasets could be used to monitor programs providing prevention and treatment services to people who inject drugs (PWID). However, diagnostic codes in administrative datasets do not differentiate non-injection from injection drug use (IDU). We validated algorithms based on diagnostic codes and prescription records representing IDU in administrative datasets against interview-based IDU data. METHODS: The British Columbia Hepatitis Testers Cohort (BC-HTC) includes ∼1.7 million individuals tested for HCV/HIV or reported HBV/HCV/HIV/tuberculosis cases in BC from 1990 to 2015, linked to administrative datasets including physician visit, hospitalization and prescription drug records. IDU, assessed through interviews as part of enhanced surveillance at the time of HIV or HCV/HBV diagnosis from a subset of cases included in the BC-HTC (n = 6559), was used as the gold standard. ICD-9/ICD-10 codes for IDU and injecting-related infections (IRI) were grouped with records of opioid substitution therapy (OST) into multiple IDU algorithms in administrative datasets. We assessed the performance of IDU algorithms through calculation of sensitivity, specificity, positive predictive, and negative predictive values. RESULTS: Sensitivity was highest (90-94%), and specificity was lowest (42-73%) for algorithms based either on IDU or IRI and drug misuse codes. Algorithms requiring both drug misuse and IRI had lower sensitivity (57-60%) and higher specificity (90-92%). An optimal sensitivity and specificity combination was found with two medical visits or a single hospitalization for injectable drugs with (83%/82%) and without OST (78%/83%), respectively. Based on algorithms that included two medical visits, a single hospitalization or OST records, there were 41,358 (1.2% of 11-65 years individuals in BC) recent PWID in BC based on health encounters during 3- year period (2013-2015). CONCLUSION: Algorithms for identifying PWID using diagnostic codes in linked administrative data could be used for tracking the progress of programing aimed at PWID. With population-based datasets, this tool can be used to inform much needed estimates of PWID population size.

Syndemic Characterization of HCV, HBV, and HIV Co-infections in a Large Population Based Cohort Study.

BACKGROUND: Limited data are available on HBV, HCV, and HIV co-infections and triple infection. We characterized co-occurrence of HIV, HBV, and HCV infections at the population level in British Columbia (BC) to identify patterns of predisposing factors unique to co-infection subgroups. METHODS: We analyzed data from the BC Hepatitis Testers Cohort, which includes all individuals tested for HCV or HIV in BC between 1992 and 2013, or included in provincial public health registries of HIV, HCV, HBV, and active tuberculosis. Individuals were classified as negative, mono-, and co-infection groups based on HIV, HBV, and HCV status. We evaluated associations between risk factors (injection drug use, sexual orientation etc.) and co-infection groups using multivariate multinomial logistic regression. FINDINGS: Of a total of 1,376,989 individuals included in the analysis, 1,276,290 were negative and 100,699 were positive for HIV, HBV, and/or HCV. Most cases (91,399, 90.8%) were mono-infected, while 3991 (4.0%) had HBV/HCV, 670 HBV/HIV (0.7%), 3459 HCV/HIV (3.4%), and 1180 HBV/HCV/HIV (1.2%) co-infection. Risk factor and demographic distribution varied across co-infection categories. MSM classification was associated with higher odds of all HIV co-infection groups, particularly HBV/HIV (OR 6.8; 95% CI: 5.6, 8.27), while injection drug use was most strongly associated with triple infection (OR 64.19; 95% CI: 55.11, 74.77) and HIV/HCV (OR 23.23; 95% CI: 21.32, 25.31). INTERPRETATION: Syndemics of substance use, sexual practices, mental illness, socioeconomic marginalization, and co-infections differ among population groups, highlighting avenues for optimal composition and context for health services to meet each population's unique needs. FUNDING: BC Centre for Disease Control and Canadian Institutes of Health Research.

Measuring the Operative Treatment Effect in End-Stage Ankle Arthritis: Are We Asking the Right Questions? A COFAS Multicenter Study.

BACKGROUND: Foot and ankle surgeons are increasingly relying on patient-reported outcome measures (PROMs) such as the Ankle Osteoarthritis Scale (AOS) to evaluate treatment options. The objectives of this retrospective cohort study were 2-fold: (1) to examine the AOS instrument using psychometric analysis and (2) to revise the questions on the AOS to improve the effect of questions on the score and remove redundancies. METHODS: Pre- and postoperative patient scores were obtained from AOS questionnaires in the COFAS Prospective Ankle Reconstruction Database, a cohort of patients operatively treated for end-stage ankle arthritis. A split-sample approach was used to evaluate the AOS and to propose a revised instrument. RESULTS: A total of 380 patients who had been treated with total ankle replacement or ankle arthrodesis were prospectively followed to the 2-year postoperative time point. Correlation analysis demonstrated that a number of questions on the AOS were highly correlated with other similar questions, frequently incomplete, or showed little variation between respondents. Eight of the original AOS questions were retained in the newly proposed Ankle Arthritis Score (AAS) [3 from the AOS Pain subscale and 5 from the AOS Disability subscale]. Principal components analysis (PCA) showed that these questions equally clustered into 2 domains in AAS: Basic Activity and Advanced Activity. CONCLUSIONS: The AAS is shorter and has improved psychometric properties as compared to the AOS. Further investigation is required to better characterize the clinical utility of this proposed new patient-reported outcome score. LEVEL OF EVIDENCE: Level III, retrospective cohort study.

The INTERGROWTH-21st gestational weight gain standard and interpregnancy weight increase: A population-based study of successive pregnancies.

OBJECTIVE: To link the INTERGROWTH-21st gestational weight gain standard with the risks of excess maternal postpartum weight retention, approximated by women's weight change between successive pregnancies. METHODS: A population-based retrospective cohort study of 58,534 women delivering successive pregnancies in British Columbia, Canada (2000-2015) was conducted. Pregnancy weight gain (kg) in the index pregnancy was converted into a gestational age-standardized z-score using the INTERGROWTH-21st standard. Excess interpregnancy weight gain was defined as weight increases of 5 kg, 10 kg, or obesity (≥30 kg/m2 ) at the next pregnancy. Weight gain z-scores and excess interpregnancy weight change were associated using logistic regression. RESULTS: For all definitions of excess interpregnancy weight gain, risks remained low and stable below a weight gain z-score of 0 (50th percentile) but rose sharply with increasing z-scores above zero. Compared with women gaining -1 to 0 SD (16th to 50th percentiles), women gaining > 0 to +1 SD (51st to 84th percentiles) were 55% to 84% more likely to retain excess weight between pregnancies. Risks were three- to sixfold higher in women gaining >+1 SD. CONCLUSIONS: A large range of the INTERGROWTH-21st percentiles were associated with increased risks of excess interpregnancy weight gain. The standard may normalize high weight gains of women at increased risk of excess weight retention.

BAYESIAN ANALYSIS TO EVALUATE TESTS FOR THE DETECTION OF MYCOBACTERIUM BOVIS INFECTION IN FREE-RANGING WILD BISON (BISON BISON ATHABASCAE) IN THE ABSENCE OF A GOLD STANDARD.

We estimated the sensitivity and specificity of the caudal-fold skin test (CFT), the fluorescent polarization assay (FPA), and the rapid lateral-flow test (RT) for the detection of Mycobacterium bovis in free-ranging wild wood bison (Bison bison athabascae), in the absence of a gold standard, by using Bayesian analysis, and then used those estimates to forecast the performance of a pairwise combination of tests in parallel. In 1998-99, 212 wood bison from Wood Buffalo National Park (Canada) were tested for M. bovis infection using CFT and two serologic tests (FPA and RT). The sensitivity and specificity of each test were estimated using a three-test, one-population, Bayesian model allowing for conditional dependence between FPA and RT. The sensitivity and specificity of the combination of CFT and each serologic test in parallel were calculated assuming conditional independence. The test performance estimates were influenced by the prior values chosen. However, the rank of tests and combinations of tests based on those estimates remained constant. The CFT was the most sensitive test and the FPA was the least sensitive, whereas RT was the most specific test and CFT was the least specific. In conclusion, given the fact that gold standards for the detection of M. bovis are imperfect and difficult to obtain in the field, Bayesian analysis holds promise as a tool to rank tests and combinations of tests based on their performance. Combining a skin test with an animal-side serologic test, such as RT, increases sensitivity in the detection of M. bovis and is a good approach to enhance disease eradication or control in wild bison.

Agreement between the caudal fold test and serological tests for the detection of Mycobacterium bovis infection in bison.

The objective of this study was to estimate agreement between the caudal fold test (CFT) and different serological tests for the detection of Mycobacterium bovis infection in bison by using prevalence-adjusted bias-adjusted kappa (PABAK). A total of 212 of wild wood bison from Wood Buffalo National Park were tested with the CFT as well as several serological tests: fluorescent polarization assay (FPA), multiantigen print immunoassay (MAPIA), rapid lateral-flow test (RT) and dual path platform test (DPP). For RT, 3 variations were conducted using 30µl of serum (RT 30), 20µl of serum (RT 20) and 20µl of serum considering only a strong reaction as positive (RT 20 ST). The McNemar's χ(2) test was conducted to assess whether the proportion of positive test results to 2 different tests differed. Two measures of agreement between pair of tests were estimated: the Cohen's kappa statistic and PABAK. The apparent prevalence of tuberculosis in the sampled animals varied depending on the diagnostic test from 6.1% (FPA and DPP) to 47.2% (CFT). The prevalence estimated by CFT differed from the prevalence estimated by the other tests, whereas the prevalence estimated by FPA, MAPIA, RT 20 ST and DPP were not significantly different. The kappa and PABAK estimates calculated between CFT and the rest of the tests suggested poor to slight agreement between tests (k and PABAK<0.25 in all cases). The PABAK estimates for the pairwise combinations among serological tests were numerically greater than the kappa estimates (and significantly greater when FPA was compared to the rest of serological tests), and suggested substantial to almost perfect agreement (PABAK>0.75 in all cases). The disagreement between the skin and serological tests for the detection of M. bovis infection could be partly because the tests measure different immunological responses (cell-mediated vs. humoral) that are predominant at different stages of the infection, and partly due to inaccuracy of the tests. Further research is needed to evaluate the accuracy of diagnostic tests in order to establish a reliable case definition, combining different tests, to be used in the surveillance and control of tuberculosis in free-ranging bison populations.

Aggressive behavior in two different group-housing systems for pregnant sows.

The study housed 120 pregnant sows from Day 29 of pregnancy to 1 week before parturition either in groups of 10 with trickle feeding (TRICKLE) or in groups of 20 with an unprotected electronic sow feeding (FITMIX). The study recorded aggressive interaction on 11 nonconsecutive days. Frequency of aggressive interactions was higher in FITMIX (p < .05); yet, intense physical contact was unusual in both systems (3% of the total interactions). Conflicts in FITMIX centered largely on the feeder (83% vs. 23% for FITMIX and TRICKLE, respectively [p < .05]); in TRICKLE, they occurred mainly in the resting area (13% vs. 48% for FITMIX and TRICKLE, respectively [p < .05]). Forty-six percent of the FITMIX sows (mostly gilts and subordinates) needed assistance to adapt to the feeding system. Eventually, 8.3% of the FITMIX sows failed to adapt and had to be removed. In conclusion, although aggressive interactions were mainly of low intensity, sequential feeding appeared to make FITMIX a more competitive feeding system.

Feeder use patterns in group-housed pregnant sows fed with an unprotected electronic sow feeder (Fitmix).

Previous studies on feeder use in group-housed pregnant sows focused on dynamic groups and protected electronic sow feeders (ESF). This study observed 60 pregnant sows, 1st to 8th parity--housed from Day 29 of pregnancy to 1 week before parturition in stable groups of 20 animals, 1 Fitmix feeder per group. Data from 25 nonconsecutive 24-hr feeding cycles showed sows making several visits to the feeder. Literature on conventional ESF indicated shorter daily feeder occupation. Daily feeder occupation per sow decreased over time (p < .001). The study observed maximum feeder activity in the hours following the start of each feeding cycle. During the experiment, there was a relatively stable, quickly established, and maintained feeder order (W > 0.80, p < .001). This highly correlated with dominance rank (r(s) = 0.80, p < .001). High-ranking sows fed earlier and made as many--but longer--visits as low-ranking sows; thus, they occupied the feeder more time every day (p < .01). Although optimization of the feeder efficiency may take several weeks, Fitmix seems an efficient feeding system for medium-size, stable groups of sows.