Serosurvey for Influenza D Virus Exposure in Cattle, United States, 2014-2015.

Influenza D virus has been detected predominantly in cattle from several countries. In the United States, regional and state seropositive rates for influenza D have previously been reported, but little information exists to evaluate national seroprevalence. We performed a serosurveillance study with 1,992 bovine serum samples collected across the country in 2014 and 2015. We found a high overall seropositive rate of 77.5% nationally; regional rates varied from 47.7% to 84.6%. Samples from the Upper Midwest and Mountain West regions showed the highest seropositive rates. In addition, seropositive samples were found in 41 of the 42 states from which cattle originated, demonstrating that influenza D virus circulated widely in cattle during this period. The distribution of influenza D virus in cattle from the United States highlights the need for greater understanding about pathogenesis, epidemiology, and the implications for animal health.

Prevalence, antimicrobial resistance, and molecular characterization of Campylobacter spp. in bulk tank milk and milk filters from US dairies.

Campylobacter spp. are frequently isolated from dairy cows as commensal organisms. Sporadic Campylobacter infections in humans in the United States are generally attributed to poultry, but outbreaks are also commonly associated with dairy products, particularly unpasteurized or raw milk. Bulk tank milk samples and milk filters from US dairy operations were collected during the National Animal Health Monitoring System Dairy 2014 study and analyzed using real-time PCR and traditional culture techniques for the presence of thermophilic Campylobacter species. The weighted prevalence of operations from which we detected Campylobacter spp. in either bulk tank milk or milk filters was 24.9%. We detected Campylobacter spp. in a higher percentage of operations with 100-499 cows (42.8%) and 500 or more cows (47.5%) than in operations with 30-99 cows (6.5%). Campylobacter spp. were also more frequently detected in operations in the west than the east (45.9 and 22.6%, respectively). We isolated Campylobacter spp. from approximately half of PCR-positive samples, representing 12.5% (weighted prevalence) of operations. The majority (91.8%) of isolates were C. jejuni, but C. lari and C. coli were also isolated. We detected resistance to tetracycline in 68.4% of C. jejuni isolates, and resistance to ciprofloxacin and nalidixic acid in 13.2% of C. jejuni isolates. Based on pulsed-field gel electrophoresis, we found that dairy-associated C. jejuni were genotypically diverse, although clonal strains were isolated from different geographic regions. These results suggest that bulk tank milk can be contaminated with pathogenic Campylobacter spp., and that the consumption of unpasteurized or raw milk presents a potential human health risk.

Association between caudal fold tuberculin test responses and results of an ELISA for Mycobacterium avium subsp paratuberculosis and mycobacterial culture of feces in tuberculosis-free dairy herds.

OBJECTIVE--To evaluate associations between Mycobacterium avium subsp paratuberculosis (MAP) and caudal fold tuberculin (CFT) test results in cattle. DESIGN--Longitudinal and cross-sectional evaluations. ANIMALS--1 California (approx 3,600 cows) and 3 Colorado (approx 640, 1,190, and 1,480 cows) dairy herds considered free of Mycobacterium bovis infection. PROCEDURES--In the California herd, the association between CFT response and MAP status was determined with ELISA and mycobacterial culture of feces within 1 year before and after CFT testing. The association between CFT and MAP status in all herds was modeled with mixed-effects logistic regression. RESULTS--In the California herd, significantly higher odds of being classified as suspect by CFT were found for cows with results of MAP ELISA negative before and positive after CFT testing (OR, 5.6) and cows positive before and after CFT testing (OR, 8.1). Higher odds were found for cows positive for mycobacterial culture of feces before and negative for culture after CFT testing (OR, 4.6) and cows negative for mycobacterial culture of feces before and positive for culture after CFT testing (OR, 13.2). All herds had higher odds of being classified as suspect by CFT testing for cows with positive results for ELISA (OR, 2.9) or mycobacterial culture of feces (OR, 5.0), compared with cows with negative results of the same tests. CONCLUSIONS AND CLINICAL RELEVANCE--A strong association was found between positive MAP test results and being classified as a suspect by CFT testing. Within-herd MAP prevalence may affect specificity of CFT testing for tuberculosis in cattle.

Comparison of calf weaning weight and associated economic variables between beef cows with and without serum antibodies against or isolation from feces of Mycobacterium avium subsp paratuberculosis.

OBJECTIVE: To compare calf weaning weight and associated economic variables for beef cows with serum antibodies against Mycobacterium avium subsp paratuberculosis (MAP) or from which MAP was isolated from feces with those for cows that were seronegative for antibodies against or culture negative for MAP. DESIGN: Retrospective study. ANIMALS: 4,842 beef cows from 3 herds enrolled in the USDA National Johne's Disease Demonstration Herd Project. PROCEDURES: Individual cow ELISA and culture results were obtained from the project database. During each parity evaluated for each cow, the 205-day adjusted weaning weight (AWW) of its calf was calculated. The AWW was compared between test-positive and test-negative cows by use of multilevel mixed-effect models. The median value for feeder calves from 2007 to 2011 was used to estimate the economic losses associated with MAP test-positive cows. RESULTS: The AWW of calves from cows with strongly positive ELISA results was 21.48 kg (47.26 lb) less than that of calves from cows with negative ELISA results. The AWW of calves from cows classified as heavy or moderate MAP shedders was 58.51 kg (128.72 lb) and 40.81 kg (89.78 lb) less, respectively, than that of calves from MAP culture-negative cows. Associated economic losses were estimated as $57.49/calf for cows with strongly positive ELISA results and $156.60/calf and $109.23/calf for cows classified as heavy and moderate MAP shedders, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Calves from cows with MAP-positive test results had significantly lower AWWs than did calves from cows with MAP-negative test results, which translated into economic losses for MAP-infected beef herds.

Herd-level risk factors associated with fecal shedding of Shiga toxin-encoding bacteria on dairy farms in Minnesota, USA.

This study aimed to identify herd-level risk factors associated with fecal shedding of Shiga toxin-encoding bacteria (STB) on dairy cattle farms in Minnesota, USA. After adjustment for farm size, risk factors included: use of total mixed ration (TMR) for lactating dairy cows [odds ratio (OR) = 3.0; 95% confidence interval (CI): 1.8 to 5.1], no use of monensin for weaned calves (OR = 4.8, 95% CI: 2.5, 9.3), and no use of decoquinate for preweaned calves (OR = 2.2, 95% CI: 1.4, 3.6). Fecal shedding of STB was more common in small herds (< 100 cows, OR = 3.6, 95% CI: 2.1, 6.2) than in large herds (≥ 100 cows). Herd management factors related to cattle feeding practices were associated with fecal shedding of STB.

Facteurs de risque au niveau du troupeau associés à l'excrétion fécale des bactéries encodant la toxine de Shiga dans les fermes laitières du Minnesota, États-Unis. Cette étude avait pour but d'identifier les facteurs de risque au niveau du troupeau associés à l'excrétion fécale de bactéries encodant la shiga-toxine dans les fermes de bovins laitiers au Minnesota, États-Unis. Après un ajustement pour la taille de la ferme, les facteurs de risque incluaient : l'utilisation de la ration mixte totale (RMT) pour les vaches laitières en lactation [rapport de cotes (RC) = 3,0; intervalle de confiance (IC) de 95 % : de 1,8 à 5,1], pas d'utilisation de monensin pour les veaux sevrés (RC = 4,8, IC de 95 % : 2,5, 9,3) et pas d'utilisation de décoquinate pour les veaux présevrés (RC = 2,2, IC de 95 % : 1,4, 3,6). L'excrétion fécale de la bactérie encodant la shiga-toxine était plus commune dans les petits troupeaux (< 100 vaches, RC = 3,6, IC de 95 % : 2,1, 6,2) que dans les grands troupeaux (≥ 100 vaches). Des facteurs de gestion du troupeau se rapportant aux pratiques d'alimentation du bétail ont été associés à l'excrétion fécale de la bactérie encodant la shiga-toxine.(Traduit par Isabelle Vallières).

Perceptions of veterinarians in bovine practice and producers with beef cow-calf operations enrolled in the US Voluntary Bovine Johne's Disease Control Program concerning economic losses associated with Johne's disease.

This study compares the perceptions of producers and veterinarians on the economic impacts of Mycobacterium avium subspecies paratuberculosis (MAP) infection in cow-calf herds. Questionnaires were mailed to beef producers through the Designated Johne's Coordinators and to veterinarians belonging to a nationwide professional organization. Important components of losses associated with MAP infected cows were used to estimate total loss per infected cow-year using an iterative approach based on collected survey data. Veterinarians were more likely to perceive a lower calving percentage in MAP infected cows compared to producers (P=0.02). Income lost due to the presence of Johne's disease (JD) in an infected cattle herd was perceived to be higher by veterinarians (P<0.01). Compared to veterinarians without JD certification, seedstock producers were more likely to perceive genetic losses due to culling cows positive for MAP (P<0.01). There were mixed opinions regarding the magnitude of lowered weaning weight in calves from infected cows and perceived differences in risk of other diseases or conditions in infected cows. An annual loss of $235 (95% CR: $89-$457) for each infected animal was estimated based on information from the producer survey. The analogous estimate using information inputs from veterinarians was $250 ($82-$486). Mean annual loss due to JD in a 100 cow herd with a 7% true prevalence was $1644 ($625-$3250) based on information provided by producers. Similarly, mean annual loss based on information collected from veterinarians was $1747 ($575-$3375).

Evaluation of an alternative method of herd classification for infection with paratuberculosis in cattle herds in the United States.

OBJECTIVE: To develop a better system for classification of herd infection status for paratuberculosis (Johne's disease [JD]) in US cattle herds on the basis of the risk of potential transmission of Mycobacterium avium subsp paratubeculosis. SAMPLE: Simulated data for herd size and within-herd prevalence; sensitivity and specificity for test methods obtained from consensus-based estimates. PROCEDURES: Interrelationships among variables influencing interpretation and classification of herd infection status for JD were evaluated by use of simulated data for various herd sizes, true within-herd prevalences, and sampling and testing methods. The probability of finding ≥ 1 infected animal in herds was estimated for various testing methods and sample sizes by use of hypergeometric random sampling. RESULTS: 2 main components were required for the new herd JD classification system: the probability of detection of infection determined on the basis of test results from a sample of animals and the maximum detected number of animals with positive test results. Tables were constructed of the estimated probability of detection of infection, and the maximum number of cattle with positive test results or fecal pools with positive culture results with 95% confidence for classification of herd JD infection status were plotted. Herd risk for JD was categorized on the basis of 95% confidence that the true within-herd prevalence was ≤ 15%, ≤ 10%, ≤ 5%, or ≤ 2%. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of the findings indicated that a scientifically rigorous and transparent herd classification system for JD in cattle is feasible.

Cattle-level risk factors associated with fecal shedding of Shiga toxin-encoding bacteria on dairy farms, Minnesota, USA.

The objective of this study was to identify individual cattle-level risk factors associated with fecal shedding of Shiga toxin-encoding bacteria (STB), a surrogate for Shiga toxin-producing E. coli (STEC), on 28 organic and conventional dairy farms. It was found that small organic herds (fewer than 100 cows) were associated with higher odds of Shiga toxin-encoding bacteria (STB) shedding from 2 (all cattle and all cows) of 3 cattle models, followed by small conventional herds, compared with large conventional herds. Preweaned calves [odds ratio (OR) = 2.6, 95% confidence interval (CI): 1.2, 5.7] had higher odds of shedding STB compared with adult cows. Calves more than 28 days of age (OR = 2.0, 95%CI: 1.0, 4.4) were more likely to shed STB than calves less than 28 days of age. This information may be helpful for identifying potential control strategies such as targeted vaccination or management practices.

Antimicrobial susceptibility of Shiga toxin-producing Escherichia coli isolated from organic dairy farms, conventional dairy farms, and county fairs in Minnesota.

This study compared the antimicrobial susceptibility of Shiga toxin-producing Escherichia coli (STEC) isolates from organic dairy farms, conventional dairy farms, and Minnesota county fairs. A total of 83 STEC isolates (43 O157 and 40 non-O157 STEC) were tested for antimicrobial susceptibility as determined by the automated broth microdilution method. Resistance to tetracycline was identified in 19 (23%) isolates and to sulphadimethoxine in 40 (48%) isolates. Half of the STEC isolates were resistant to at least one antimicrobial agent. Resistance to at least one antimicrobial agent was observed in 18 (62%) isolates from conventional farms and in 11 (48%) isolates from organic farms. Resistance to at least one antimicrobial agent was more frequent in isolates from calves (77%) than from cows (39%). Multidrug resistant patterns were more common in non-O157 STEC than O157 STEC. This study provides data to document the degree of STEC antimicrobial resistance from dairy cattle sources in Minnesota. The use of antimicrobial agents on farms, and other environmental influences, may affect resistance patterns in isolates from cattle sources. Systematic surveillance of STEC from cattle could potentially detect emergence of antimicrobial resistance that may be spread to humans through the food chain.

Prevalence of shiga toxin-encoding bacteria and shiga toxin-producing Escherichia coli isolates from dairy farms and county fairs.

Shiga toxin-encoding bacteria (STB) and shiga toxin-producing Escherichia coli (STEC) were detected and isolated from dairy cattle and their farm environment and from manure piles at Minnesota (MN) county fairs from 2001 to 2002. A total of 2,540 samples were collected from 28 dairy cattle farms (8 organic and 20 conventional), 17 calf pens (5 organic and 12 conventional), and 12 county fairs. STB were detected from 71 (3.2%) of 2208 fecal samples with 20 (71.4%) of 28 dairy farms having at least one positive animal sample. In samples collected from conventional farms, 41 (2.3%) of 1750 fecal samples were STB-positive and 13 (65%) of 20 farms had at least one positive animal. Thirty (6.6%) of 458 fecal samples from organic farms were STB-positive and 7 (87.5%) of 8 farms had at least one positive animal. STB was detected from 31 (17.4%) of 178 samples and 7 (58.3%) out of 12 manure piles at county fairs. A total of 43 STEC isolates were recovered and belonged to 26 different serotypes (19 O and 18 H types). Among STEC, 60.5% possessed only stx1, 30.2% stx2, and 9.3% both stx1 and stx2. The genes eae and hlyA were detected in more than 50% of the STEC isolates. STB can be found on most dairy cattle farms including organic and conventional herds and county fairs. The presence of these potentially pathogenic bacteria in county fairs may pose a risk to the public who have contact with cattle or their environment.

Evaluation of antimicrobial susceptibility patterns in Campylobacter spp isolated from dairy cattle and farms managed organically and conventionally in the midwestern and northeastern United States.

OBJECTIVE: To describe antimicrobial susceptibility patterns in Campylobacter spp isolated from dairy cattle and farms managed organically and conventionally in the midwestern and northeastern United States. DESIGN: Longitudinal study. SAMPLE POPULATION: 128 farms. PROCEDURE: Samples and data were collected every 2 months from August 2000 to October 2001. Fecal samples were collected from calves and cows. Milk samples were obtained from the bulk tank and milk line filters. Environmental samples were obtained from a water source, feed bunks of lactating cows, and cattle housing areas. Campylobacter identification and antimicrobial susceptibility testing were performed at a central laboratory by use of microbroth dilution with 2 customized antimicrobial susceptibility panels. RESULTS: 460 and 1,570 Campylobacter isolates were obtained from organic and conventional dairy farms, respectively. Most isolates from both farm types were susceptible to most antimicrobial agents tested, and antimicrobial susceptibility of conventional dairy isolates was decreased, compared with organic dairy isolates. Low proportions of isolates resistant to ampicillin (< 10%) and moderate proportions resistant (30% to 60%) to kanamycin, sulfamethoxazole, and tetracycline were observed on both farm types. The proportion of isolates resistant to tetracycline was higher for conventional than organic farms. CONCLUSIONS AND CLINICAL RELEVANCE: Campylobacter isolates from dairy cattle and farms managed organically and conventionally had similar patterns of antimicrobial resistance; the proportion of resistant isolates was higher for conventional than organic farms.

Genetic mechanisms contributing to reduced tetracycline susceptibility of Campylobacter isolated from organic and conventional dairy farms in the midwestern and northeastern United States.

Campylobacter is one of the most common causes of gastroenteritis and can be acquired through contact with farm animals or the consumption of raw milk. Because of concerns over the role of food-producing animals in the dissemination of antimicrobial resistance to humans, we evaluated the prevalence of antimicrobial resistance in Campylobacter isolates from dairy farms and the genetic mechanism conferring the observed resistance. Evaluation of antimicrobial resistance was completed on 912 isolates from conventional and 304 isolates from organic dairy farms to eight drugs (azithromycin, chloramphenicol, ciprofloxacin, clindamycin, erythromycin, gentamicin, nalidixic acid, and tetracycline) with microbroth dilution. Resistance to seven of eight drugs was very low and did not differ by farm type. However, tetracycline resistance was common in Campylobacter isolated from both organic and conventional dairy farms, with 48 and 58% of isolates affected, respectively. By multiplex PCR, we determined that tetracycline resistance was highly associated with the carriage of tetO in Campylobacter isolates (X2 = 124, P < 0.01, kappa = 0.86).

Prevalence and characterization of Escherichia coli O157 isolates from Minnesota dairy farms and county fairs.

Samples were collected from 26 organic and conventional farms and 12 county fairs in Minnesota during 2001 and 2002 to identify the presence of Escherichia coli O157. Immunomagnetic separation was used for isolation of E. coli O157. Isolates were further characterized by the presence of virulence marker genes (stx1, stx2, eaeA, E-hly, katP, etpD, and espP), antimicrobial susceptibility profiles, and genotypes. During 2001, E. coli O157 was isolated from 16 (5.2%) of 305 fecal samples and from 7 (36.8%) of 19 farms. During 2002, E. coli O157 was isolated from 6 (4.5%) of 132 fecal samples from weaned calves at 4 (23.5%) of 17 farms. During 2001 and 2002, cattle manure samples were collected from 12 county fairs, and E. coli O157 was isolated from 19 (11%) of 178 samples and 9 (75%) of 12 county fairs. Among 40 E. coli O157 isolates, 17 isolates (43%) had both the stx1 and stx2 genes, and 21 strains (53%) had the stx2 gene only. Thirteen percent of O157 isolates were resistant to tetracycline, and 25% were resistant to sulfadimethoxine. Heterogeneity of E. coli O157 strains was demonstrated by the presence of 22 different pulsed-field gel electrophoresis (PFGE) patterns. Four PFGE patterns matched those of isolates previously found in humans. The presence of E. coli O157 at county fairs suggests the potential for transmission to the public, who may have contact with cattle or their environment.

Prevalence of Salmonella spp on conventional and organic dairy farms.

OBJECTIVE: To describe the occurrence of fecal shedding, persistence of shedding over time, and serogroup classification of Salmonella spp on a large number of dairy farms of various sizes. DESIGN: Longitudinal study. SAMPLE POPULATION: 22,417 fecal samples from cattle and 4,570 samples from the farm environment on 110 organic and conventional dairy farms in Minnesota, Wisconsin, Michigan, and NewYork. PROCEDURE: 5 visits were made to each farm at 2-month intervals from August 2000 to October 2001. Fecal samples from healthy cows, calves, and other targeted cattle groups and samples from bulk tank milk, milk line filters, water, feed sources, and pen floors were collected at each visit. Bacterial culture was performed at 1 laboratory. RESULTS: Salmonella spp were isolated from 4.8% of fecal samples and 5.9% of environmental samples; 92.7% of farms had at least 1 Salmonella-positive sample. The 75th percentile for median within-herd prevalence of Salmonella spp in cattle for 5 sampling visits to a given farm was 2.0% and for maximum within-herd prevalence of Salmonella spp was 13.6%. Farms with a median within-herd prevalence of Salmonella spp of > or = 2.0% accounted for 76.3% of Salmonella-positive samples. There was no significant difference in the prevalence of Salmonella spp between conventional and organic farms. Seasonal differences in Salmonella shedding were observed. More farms had at least 1 serogroup B isolate than any other serogroup, whereas serogroup E1 was the most common among all Salmonella-positive samples. More than 1 serogroup was isolated on 76.4% of Salmonella-positive farms. CONCLUSIONS AND CLINICAL RELEVANCE: Salmonella spp were isolated from > 90% of dairy farms; however, 25% of farms accounted for > 75% of Salmonella-positive samples. This information is critical for the direction of intervention strategies to decrease the prevalence of Salmonella spp on dairy farms.