Habitual condom use across partner type and sexual position among younger gay and bisexual men: findings from New Zealand HIV behavioural surveillance 2006-2011.

OBJECTIVES: Our objectives were to investigate demographic and behavioural factors associated with condom use and to examine how habitual condom use was across partner types and sexual positions among younger men who have sex with men (YMSM), aged 16-29, surveyed in New Zealand. METHODS: We analysed the 2006-2011 national HIV behavioural surveillance data from YMSM who reported anal intercourse in four scenarios of partner type and sexual position: casual insertive, casual receptive, regular insertive and regular receptive. For each, respondents' condom use was classified as frequent (always/almost always) or otherwise, with associated factors identified with multivariate mixed-effect logistic regression. Habitual condom use across scenarios was examined using a latent variable technique that estimated the intraclass correlation coefficient (ICC). RESULTS: Frequent condom use was reported for 63.6% of 5153 scenarios reported from 2412 YMSM. Frequent use increased from boyfriend to fuckbuddy to casual partners. Infrequent use was associated with online recruitment, Pacific ethnicity, less education, HIV positivity, sex with women, having ≥20 sexual partners versus 1 and reporting insertive and receptive sexual positions. Frequent condom use was associated with having two to five sexual partners versus one and shorter regular partnerships. The ICC=0.865 indicated highly habitual patterns of use; habitual infrequent condom use was most prevalent with regular partners (53.3%) and habitual frequent condom use was most prevalent with casual partners (70.2%) and for either sexual position (50.5% and 49.1%). CONCLUSIONS: Habitual condom use among YMSM highlights the value of early, engaging and sustained condom promotion. Public health should provide better and more compelling condom education, training and promotion for YMSM.

Burden of illness and factors associated with duration of illness in clinical campylobacteriosis.

A population-based study investigated the burden of illness, including the duration of illness associated with laboratory-confirmed cases of campylobacteriosis in two health unit areas. Questionnaire data were collected for 250 cases. The median duration of illness was 8 days and 66% of cases reported symptoms of moderate severity or greater. A Cox proportional hazards model identified antimicrobial use factors associated with a significantly increased rate of symptom resolution (shorter duration of illness): macrolides for less than the recommended number of days, ciprofloxacin for at least 3 days, and antimicrobials not recommended for campylobacteriosis. The impact of antimicrobial use was consistent regardless of when, during the course of illness, the antimicrobial use began. The effectiveness of ciprofloxacin in these results may be due to the low prevalence of resistance to ciprofloxacin in isolates from this study. The effect of antimicrobials not recommended for campylobacteriosis should be further investigated.

The REFLECT statement: methods and processes of creating reporting guidelines for randomized controlled trials for livestock and food safety.

The conduct of randomized controlled trials in livestock with production, health, and food-safety outcomes presents unique challenges that may not be adequately reported in trial reports. The objective of this project was to modify the CONSORT (Consolidated Standards of Reporting Trials) statement to reflect the unique aspects of reporting these livestock trials. A two-day consensus meeting was held on November 18-19, 2008 in Chicago, Ill, United States of America, to achieve the objective. Prior to the meeting, a Web-based survey was conducted to identify issues for discussion. The 24 attendees were biostatisticians, epidemiologists, food-safety researchers, livestock production specialists, journal editors, assistant editors, and associate editors. Prior to the meeting, the attendees completed a Web-based survey indicating which CONSORT statement items may need to be modified to address unique issues for livestock trials. The consensus meeting resulted in the production of the REFLECT (Reporting Guidelines for Randomized Control Trials) statement for livestock and food safety (LFS) and 22-item checklist. Fourteen items were modified from the CONSORT checklist, and an additional sub-item was proposed to address challenge trials. The REFLECT statement proposes new terminology, more consistent with common usage in livestock production, to describe study subjects. Evidence was not always available to support modification to or inclusion of an item. The use of the REFLECT statement, which addresses issues unique to livestock trials, should improve the quality of reporting and design for trials reporting production, health, and food-safety outcomes.

The REFLECT statement: methods and processes of creating reporting guidelines for randomized controlled trials for livestock and food safety.

The conduct of randomized controlled trials in livestock with production, health, and food-safety outcomes presents unique challenges that might not be adequately reported in trial reports. The objective of this project was to modify the CONSORT (Consolidated Standards of Reporting Trials) statement to reflect the unique aspects of reporting these livestock trials. A 2-day consensus meeting was held on November 18-19, 2008 in Chicago, IL, to achieve the objective. Before the meeting, a Web-based survey was conducted to identify issues for discussion. The 24 attendees were biostatisticians, epidemiologists, food-safety researchers, livestock production specialists, journal editors, assistant editors, and associate editors. Before the meeting, the attendees completed a Web-based survey indicating which CONSORT statement items would need to be modified to address unique issues for livestock trials. The consensus meeting resulted in the production of the REFLECT (Reporting Guidelines for Randomized Control Trials) statement for livestock and food safety and 22-item checklist. Fourteen items were modified from the CONSORT checklist, and an additional subitem was proposed to address challenge trials. The REFLECT statement proposes new terminology, more consistent with common usage in livestock production, to describe study subjects. Evidence was not always available to support modification to or inclusion of an item. The use of the REFLECT statement, which addresses issues unique to livestock trials, should improve the quality of reporting and design for trials reporting production, health, and food-safety outcomes.

Drinking water consumption patterns of residents in a Canadian community.

A cross-sectional survey using computer-assisted telephone interviewing was performed to assess the drinking water consumption patterns in a Canadian community, and to examine the associations between these patterns and various demographic characteristics. The median amount of water consumed daily was four 250 ml servings (1.01), although responses were highly variable (0 to 8.01). Bottled water consumption was common, and represented the primary source of drinking water for approximately 27% of respondents. Approximately 49% of households used water treatment devices to treat their tap water. The observed associations between some demographic characteristics and drinking water consumption patterns indicated potential differences in risk of exposure to waterborne hazards in the population. Our results lend support to the federal review of the bottled water regulations currently in progress in Canada. Additionally, they may lend support to a provincial/territorial government review of bottled water regulations, and both federal and provincial/territorial level reviews of the water treatment device industry. Further investigation of the use of alternative water sources and the perceptions of drinking water in Canada is also needed to better understand, and subsequently address, concerns among Canadians.

Patterns of crossfostering and piglet mortality on commercial U.S. and Canadian swine farms.

A data base of 300 farms using computerized records was used to examine the extent and timing of crossfostering being practiced in commercial herds in the Midwestern U.S. and Canada in 1994-1995. Crossfostering was used on 98% of farms. Across all farms, the mean percent of piglets crossfostered was 8.6%. Farms varied greatly in the age at which they moved piglets. The 20 farms that moved piglets the earliest after birth were classified as early-move farms and the 20 that moved the oldest piglets were classified as late-move farms. Early-move and late-move farms did not differ in herd size (P = 0.14), average parity of farrowed sows (P = 0.47) or age at weaning (P = 0.37). There were differences between early-move and late-move farms in percent of piglets fostered (P = 0.0001), pigs born alive/litter (P = 0.04), and pre-weaning mortality (P = 0.0005). A subset of late-move farms that were part of an integrated production group had unique production parameters that suggested inaccurate record-keeping.

The reproductive performance of sows after PRRS vaccination depends on stage of gestation.

In order to minimize the effects of porcine reproductive and respiratory syndrome (PRRS) on stillbirth, mummification, and neonatal mortality in swine herds, many producers have vaccinated their herds using a modified-live virus vaccine. The purpose of this study was to determine the association of the PRRS modified-live vaccine and reproductive performance by stage of gestation when the vaccine was administered. A total of 47 swine herds from Ontario and Manitoba, Canada, and from the mid-western USA were included in the study. Participating farms had vaccinated all of their sows at one point in time when they used the vaccine for the first time. The reproductive performance of sows that farrowed in the year prior to use of the vaccine was compared to that of sows vaccinated in each of five stages of gestation and in the gestation that followed the initial use of the vaccine. Sows vaccinated at any time during gestation had a reduced number of pigs born alive, a reduced number of pigs weaned per litter, and increased number of stillborn pigs and an increased number of mummified pigs compared to the sows that farrowed prior to use of the vaccine. The largest association was seen in sows that were vaccinated in the last four weeks of gestation. The largest losses were observed in those herds that were vaccinated concurrently with the initial PRRS herd outbreak. These results suggest that the modified-live vaccine should only be administered to non-gestating sows.

Associations between off-label feed additives and farm size, veterinary consultant use, and animal age.

Data from the United States National Swine Survey collected by the National Animal Health Monitoring System were used to describe the use of feed additives in swine feeds. Data were collected from 710 farms. The concentration of feed additives expressed in grams per ton of complete feed was described by stage of production, and the use of feed additives above the labeled treatment levels (i.e. off-label) was identified. Of the 3328 feeds, about 79% contained feed additives used in the labeled manner. For all classes of pigs, the prevalence of labeled feed additive use was greater than 75%. Penicillin was used according to its label most often, followed by apramycin, bacitracin, tetracyclines, lincomycin, and tylosin. Carbadox had the highest prevalence of off-label use. Of the 699 feeds that included feed additives in an off-label manner, about 57% included additives at greater than the recommended concentrations or were fed to an incorrect class of pig. About 56% of the feeds had off-label combinations of additives. Small farms were more likely to use rations with no feed additives than intermediate or large farms (P < 0.001). Of those farms using feed additives, the odds of a small farm using all feed additives in the labeled manner was 7.7 times that of an intermediate or large farm (P < 0.0001). After controlling for herd size, producers who used a veterinary consultant were 2.1 times more likely to use feeds with feed additives (P < 0.0001).

Evaluation of lansoprazole (an H+/K+-ATPase inhibitor) and azithromycin (an antibiotic) for control of gastric ulceration in swine during periods of feed deprivation.

Helicobacter-like organisms as well as fermentative bacteria have been implicated in gastric ulcer production in swine. Irregular feeding schedules are also considered a major risk factor. A research trial was conducted to determine whether medication with an acid secretion inhibitor (lansoprazole), either alone or in combination with an antibiotic (azithromycin), would protect pigs from gastric ulceration if the animals were subjected to a 48 h period of fasting. In a 2 x 3 factorial design, 48 pigs were fasted, while an equal number were fed ad libitum. Within these 2 study groups, pigs were randomly assigned to 1 of 3 treatments: control, 30 mg lansoprazole s.i.d. for 7 d, or lansoprazole (30 mg s.i.d. for 7 d) and azithromycin (500 mg s.i.d. for 3 d). Overall, fasted pigs were 1.9 times more likely to develop erosive or ulcerative lesions of the pars esophagea (chi2 = 9.89, P < 0.002). Treatment with an acid secretion inhibitor alone or in combination with an antibiotic did not protect pigs from developing gastric lesions. Helicobacter-like organisms were not detected in any of the stomachs. Possibly, the lansoprazole dose of 30 mg given once per day was insufficient to prevent pH levels from becoming low enough to cause damage to epithelial tissue. Alternatively other substances such as bile acids may have caused the ulcerative lesions, even though stomach acid production was suppressed.

Types and doses of injectable medications given to periparturient sows.

OBJECTIVE: To determine types and doses of injectable medications given to periparturient sows and reasons for administering those medications, and to compare medication practices among farms of different sizes. DESIGN: Survey. SAMPLE POPULATION: 301 farms; 231,016 periparturient sows. PROCEDURE: A survey was used to obtain information regarding medications given to sows during the farrowing period. State and federal veterinary medical officers completed surveys during their final interview with producers who had participated in the National Animal Health Monitoring System's (NAHMS) Swine 95 study. Data were summarized and treatment regimens compared among farms of different sizes. RESULTS: More than a third of the sows received medications during the farrowing period. The most common reasons for administering medications were routine preventive treatment and treatment of dystocia, uterine discharge, and poor appetite. The most commonly used medications for treatment of sick sows were oxytocin, procaine penicillin G, and B vitamins. A high percentage of medications were either not indicated for the specific condition or used at greater or less than the approved dose. In general, treatment rates and medications used did not differ among farms of different sizes. CONCLUSIONS AND CLINICAL RELEVANCE: Better treatment protocols are needed to provide more appropriate treatment of sick sows.

Effects of extensive crossfostering on performance of pigs on a farm.

OBJECTIVE: To compare mortality and growth rates of pigs subjected to continuous or limited crossfostering. DESIGN: Prospective study. ANIMALS: 80 liters containing 879 pigs. PROCEDURE: In half of the litters, crossfostering was limited to the first 2 days of life. In the other litters, pigs were crossfostered throughout the lactation period to maintain uniform body weights within litters. RESULTS: Restricting crossfostering to the first 2 days of life resulted in a 20% increase in body weight at weaning, compared with crossfostering throughout the nursing period. Mortality rates did not differ between the limited and continuous crossfostering groups. CLINICAL IMPLICATIONS: The emphasis placed on reducing variation of body weights within litters is unwarranted and veterinarians should advise limiting crossfostering to the first 2 days of life. Excessive crossfostering late in the nursing period may be identified by low within-litter SD of mean body weight.

Prevalence of morphologic defects in spermatozoa from beef bulls.

OBJECTIVE: To determine the overall prevalence of morphologic defects in spermatozoa from beef bulls and to determine whether prevalence varies with the age of the bull. DESIGN: Cross-sectional observational study. ANIMALS: 2,497 beef bulls that were evaluated for breeding soundness in 1994 by 29 practicing veterinarians in a 5-state geographic region. PROCEDURE: Slides of spermatozoa from each bull were made and submitted by practicing veterinarians for morphologic evaluation. One hundred spermatozoa per slide were examined, and each was classified as having 1 of 9 morphologic defects or as normal. RESULTS: 63% of bulls evaluated were 10 to 12 months old, and 20% were 13 to 18 months old. A mean of 70.6% of spermatozoa was classified as normal. Most common defects were proximal droplets (8.4%), distal midpiece reflexes (6.7%), separated heads (5.5%), and distal droplets (3.8%). Other defects were seen < 2% of the time. Bulls 10 to 12 months of age had a higher prevalence of proximal and distal droplet defects than older bulls. CLINICAL IMPLICATIONS: Practitioners conducting breeding soundness evaluations in beef bulls must be aware of common spermatozoal defects. Bulls that are evaluated at a young age will have more defects than older bulls and should be reevaluated, particularly for those defects for which prevalence decreases with age.

Effect of booster vaccination with a multivalent clostridial bacterin-toxoid on sudden death syndrome mortality rate among feedlot cattle.

OBJECTIVE: To determine whether booster vaccination with a multivalent clostridial bacterin-toxoid would affect the sudden death syndrome (SDS) mortality rate among feedlot cattle. DESIGN: Field trial. ANIMALS: 83, 115 cattle at a Nebraska feedlot. PROCEDURE: Cattle arriving at the feedlot underwent routine processing according to established protocol. All cattle received a sequentially numbered ear tag and a 2-ml dose of a multivalent bacterin-toxoid designed to protect cattle against Clostridium chauvoei, C speticum, C novyi, C sordellii, and C perfringens types C and D. Approximately 90 days prior to slaughter, growth promotants were implanted in all cattle, and cattle were allocated to a treatment or control group on the basis of the last digits of their ear tag numbers. Cattle in the treatment group received a second 2-ml dose of clostridial bacterintoxoid; control cattle did not. RESULTS: Significant differences between groups in regard to crude, feeding pen, or SDS mortality rates were not detected. Sudden death syndrome mortality rate across both groups was 0.24%. If the SDS mortality rate in midwestern feedlot cattle was reduced > or = 40% by booster vaccination with a multivalent clostridial bacterin-toxoid, this experiment included enough animals to have a 90% probability of detecting that difference. CLINICAL IMPLICATIONS: Booster vaccination with a multivalent clostridial bacterin-toxoid does not affect SDS mortality rate among feedlot cattle.

The use of omeprazole to alleviate stomach ulcers in swine during periods of feed withdrawal.

Controlled trials were conducted to determine if treatment with the benzimidazole compound, omeprazole, would prevent gastric ulceration associated with feed withdrawal. Pigs were fed ad libitum, fasted for 24 h, or fasted for 48 h, and within each of these 3 groups the effect of no medication (controls), of 20 mg or 40 mg of omeprazole was evaluated on the pH of gastric fluid and the presence or absence of lesions in the pars esophagea. Medication with 40 mg of omeprazole resulted in significantly higher gastric pH 24 h after treatment compared with untreated pigs or pigs medicated with 20 mg of omeprazole. Fasting for 24 h or for 48 h, resulted in more pigs developing ulcers (15 of 25) than pigs allowed free access to feed (1 out of 10) (P = 0.01). The results of this trial suggest that omeprazole was effective in preventing some, but not all, of the tissue damage in the pars esophagea related to feed withdrawal. In addition to hydrochloric acid, possibly other components, such as bile acids in the fluid gastric contents, are important in causing epithelial injury.

A Delphi exercise used to identify potential causes of variation in litter size of Ontario swine.

Forty-eight people, considered to the swine experts, were asked to collaborate in a Delphi exercise to identify the factors which they believed affect litter size in Ontario swine. The panel included 16 animal scientists, 16 pork producers, and 16 veterinarians in swine practice. The ten factors with the highest ratings were parity of the sow, mycotoxins in the feed, infections with porcine parvovirus or Leptospira spp., breeding gilts on their second versus first observed estrus, the timing of breeding with respect to the onset of estrus, purebred versus crossbred sows, boar overuse (bred by a boar that was mated more than six times per week), pen versus hand mating, age of gilt when first bred, and body condition of the sow at the time of conception. The experts did not agree about the effect on litter size of the sow's previous lactation, factors ensuring adequate nutrient intake during lactation, health of the sow and the boar, breed of a purebred sow, or the ease of mating the sow.Key items in the use of the Delphi technique to arrive at a consensus are discussed.

An investigation of the etiology of a mild diarrhea observed in a group of grower/finisher pigs.

An investigation into a mild diarrhea in a group of grower/finisher pigs was carried out in order to determine the etiology. A tiamulin injection and a carbadox-medicated ration were given to pens of pigs in a 2 x 2 factorial experimental design. Pens of pigs were assessed a score, based on the consistency of the feces in the pen, each week. The clinical investigation looked for the intestinal pathogens Brachyspira pilosicoli, B. hyodysenteriae, Lawsonia intracellularis, Salmonella spp., Yersinia spp., transmissible gastroenteritis virus, and rotavirus. Despite a rigorous investigation, the diarrhea was not attributed to any pathogen. A mild colitis was noted among pigs necropsied while affected with diarrhea. Improved diagnostic tools may allow a more effective response to an outbreak of mild disease, while at the same time reducing the amount of antimicrobials used in swine production.

The effect of birth weight and age at tail docking and ear notching on the behavioral and physiological responses of piglets.

Selection for high prolificacy has resulted in litters comprising a large number of low-birth-weight (LBW) piglets. Given their presence in over 75% of litters and increased mortality rate, it is clear that a greater understanding of LBW piglet management is required for both animal welfare and productivity. In this study, we compared the effects of tail docking and ear notching LBW and average-birth-weight (ABW) piglets at 1 or 3 d of age on suckling, behavior, passive transfer of immunoglobulins, and growth. Six piglets per litter from 20 litters (n = 120 piglets) were used in a 2 × 2 complete block design. Piglets were weighed at birth and designated as LBW (0.6 to 1.0 kg) or ABW (≥ 1.2 kg) and "processed" (tail docked and ear notched) at either 1 or 3 d of age. Vocalizations were recorded during the procedures. The acute behavioral responses were observed for 10 min after the procedure. Piglets were observed for 6 h after birth and after the procedure to determine their presence at nursing bouts. On d 5, blood samples were collected to determine concentrations of serum immunoglobulins (IgA and IgG) and IGF-I. Piglet weights were recorded at birth and on d 5, 14, and 21. During the procedures, LBW piglets produced fewer (P = 0.03) calls than ABW piglets. Piglets from either birth weight category produced a similar number (calls/s; P = 0.29) of high-frequency calls (≥ 1,000 Hz), which are indicative of pain and distress, although the average frequency (Hz) of these calls was greatest (P = 0.05) for ABW piglets processed on d 3. Immediately following the procedures, LBW piglets spent more (P = 0.005) time dog-sitting and less (P = 0.005) time lying than ABW piglets. When observed with the sow, LBW males spent more (P = 0.001) time alone and had the lowest (P = 0.007) attendance at nursing bouts compared with LBW females and all ABW piglets. Concentrations of serum IgA (P = 0.06) and IgG (P = 0.04) and plasma IGF-I (P = 0.003) were lower for LBW than ABW piglets regardless of age of processing although the magnitude of these differences was likely not of biological significance. Average-birth-weight piglets may be less reactive to the acute effects of the procedures on d 1 than on d 3. Given the decreased likelihood of a LBW piglet surviving to weaning (P = 0.001), delaying processing until 3 d of age for LBW piglets may eliminate unnecessary procedures.

Clustering of and risk factors for the porcine high fever disease in a region of Vietnam.

Porcine high fever disease (PHFD) emerged in 2006 in China and spread to Vietnam. Little work has been carried out to investigate PHFD risk factors and space-time dynamics. To fill this gap, we investigated probable cases of PHFD at household level as the outcome. A study area, approximately 100 sq. km, was selected from a province of southern Vietnam that had reported the outbreak of PHFD in 2008. A survey was conducted in the study area to collect information about swine health problems during 2008. The questionnaire included three sections: general information, clinical signs of disease in pigs and production factors believed to be risk factors. Cases were defined at the household level and included interpretation of clinical signs in series. Logistic regression with a random intercept at the hamlet level was used to assess risk factors for PHFD at the household level. Spatial clustering was investigated using the D-function and a Cuzick-Edward's test. Spatial clusters were evaluated using a spatial relative risk surface and the spatial scan statistic using a Bernoulli model. Space-time clustering was explored using a space-time K-function and Knox's test. Space-time clusters were evaluated using a space-time permutation model in SaTScan. Of 955 households with questionnaire data, 33.4% were classified as cases. The statistical significance of space and space-time clustering differed between methods employed. The risk factors associated with occurrence of cases were higher numbers of sows and finishing pigs (log 2 transformed), receiving pigs from an external source and the interaction between using 'water green crop' (WGC) as pig feed and owning ducks with or without direct contact with pigs. The interaction between the presence of ducks and feeding WGC to pigs suggested the involvement of pathogens that might be present in water (environment) and could further replicate in or on ducks.

Evaluation of the risk factors for shedding Salmonella with or without antimicrobial resistance in swine using multinomial regression method.

A multinomial logistic regression method was used to investigate the risk factors for antimicrobial resistance (AMR) in Salmonella isolated from faecal samples collected on 80 Ontario swine farms in Canada. The samples were classified into three groups including Salmonella-negative samples (S-), Salmonella-positive samples without AMR (S+AMR-) and Salmonella-positive samples with AMR (S+AMR+). The samples collected directly from pigs had a greater chance to be positive for Salmonella with AMR compared to those samples collected from the pen floor. The odds of culturing Salmonella with or without AMR was higher if pelleted feed was used compared with mash or liquid feed (P < 0.001). The faecal samples collected on farrow-to-finish farms had a significant lower chance of testing positive for Salmonella with multidrug resistance than the samples from grow-finisher farms (P = 0.004). The chance of culturing Salmonella without AMR on farms with a continuous system was higher than on farms with an all-in/all-out system (P = 0.009). However, there was no significant association between the flow system and recovery of Salmonella with AMR. The larger farms were more likely to be in S+AMR+ group than in S- group (P < 0.001) whereas herd size did not appear as a risk factor for being in S+AMR- group compared with S- group. These findings indicate that although on-farm antimicrobial use is one component of resistance, there might be other farm management factors that also affect the development of emerging resistant bacterial foodborne pathogens on swine farms. Finding different risk factors for shedding Salmonella with or without antimicrobial resistance would help to take the appropriate approach to each group if a control programme were to be implemented or an intervention applied.

Prevalence of Yersinia enterocolitica shedding and bioserotype distribution in Ontario finisher pig herds in 2001, 2002, and 2004.

We investigated characteristics of Yersinia enterocolitica infection in Ontario finisher pig herds. Our specific objectives were to estimate or test: prevalence of Y. enterocolitica shedding in finisher pigs, bioserotype distribution, agreement between the herd-level tests based on sampling pig and pooled fecal samples, whether bioserotypes cluster by farms, and whether Y. enterocolitica-positive herds cluster spatially. In total, 3747 fecal samples were collected from 100 farms over the years 2001, 2002, and 2004 (250 total herd visits). Fecal samples were tested by culture and positive isolates were biotyped and serotyped. Apparent pig-level prevalence of Y. enterocolitica was 1.8%, 3.2%, and 12.5% in 2001, 2002, and 2004, respectively. Estimated true pig-level prevalence of Y. enterocolitica was 5.1%, 9.1%, and 35.1% in 2001, 2002, and 2004, respectively. Herd-level prevalence was 16.3%, 17.9%, and 37.5% in 2001, 2002, and 2004, respectively. In all years, the most common bioserotype was 4, O:3, followed by bioserotype 2, O:5,27. Kappa between herd-level status based on pig and pooled samples ranged between 0.51 and 0.68 for biotype 1A and bioserotype 4, O:3, respectively. For 4, O:3, a significant bias in discordant pairs was detected, indicating that pig samples were more sensitive than pooled samples in declaring a herd as positive. Farms tended to be repeatedly positive with the same bioserotype, but positive study farms did not cluster spatially (suggesting lack of between herd transmission and lack of a common geographic risk factor).