Case Herds Research Articles

Case-control study on associations of hemorrhagic bowel syndrome in swine with feed characteristics and intestinal pathogens

Haemorrhagic bowel syndrome (HBS) is one of the most common causes of death in fattening pigs worldwide. The objective of this descriptive study was to systematically assess predictors or causal components for the appearance of HBS using case farms (mortality rate caused by HBS ≥ 1.5%) in comparison with control farms (mortality rate caused by HBS ≤ 0.25%), focusing on feed ingredients, feed quality and size, and gastrointestinal pathogens. The inclusion of sugar beet as a feed component in liquid feeding systems was found to be associated (p = 0.03) with farms identified as HBS cases. Another predictive or causal factor found for liquid feeding systems, but only for those using meal, was particle size. A higher percentage of small particles (< 2 mm) in the meal was associated with a higher risk of being an HBS case farm (p = 0.02), while no relevant association was detected for the use of pellets. Sugar beet in the diet was also associated with the incidence of HBS.The microbial quality of the feed in dry feeding systems, specifically the number of total aerobes at the first and last outlet tubes, was associated with a higher incidence of HBS (p = 0.03). Faecal sample analysis showed a difference (p < 0.05) in the prevalence of B. pilosicoli in the herd category (case vs. control herd). In this descriptive study, five predictive or causal factors were identified for an HBS farm with a mortality rate due to HBS ≥ 1.5%. These included the number of aerobes in dry matter samples from the first and last feeders, the particle diameter of the meal used in liquid feeding systems and sugar beet as a component of liquid feeding rations, and the presence of B. pilosicoli as an infectious agent at animal level. Relevant associations reinforce the findings of the previously published Swiss study that HBS is a multifactorial syndrome involving different aspects of pig production and cannot be attributed to a single cause. Further studies are needed to develop evidenced based causal models for HBS in swine.

Risk factors for introduction of BVDV in the context of a mandatory control program in Dutch dairy herds.

Bovine Viral Diarrhea Virus (BVDV) is a common viral disease in cattle, causing economic losses in naive herds where the virus is introduced. In the Netherlands, a BVDV control program has been in place since 1998, evolving from voluntary to mandatory participation for dairy herds since April 2018. Participation in the BVDV control program is not mandatory for non-dairy farms. The aim of this study was to determine risk factors for new introduction of BVDV into certified BVDV-free herds in the context of a national BVDV control program in dairy herds. In this retrospective case-control study, survey data were collected from 149 dairy farms that lost their BVDV-free status (case herds) and 148 matched dairy farms that maintained their BVDV-free status (control herds) between 2018 and 2021. The survey captured information about potential risk factors and herd characteristics in the 2 years leading up to the loss of BVDV-free status (case herds, virus detection in at least one animal or when seroconversion was detected) or remaining BVDV-free (control herds). Descriptive statistics and logistic regression with a backward selection and elimination procedure were used to identify potential risk factors associated with losing BVDV-free status. Risk factors were quantified as an Odds Ratio (OR) with the associated 95% confidence interval (CI). The risk factor with the highest OR for losing BVDV-free status was purchasing cattle from herds without BVDV-free status (OR 1.25, CI 1.10-1.41), followed by the farmer having another profession that resulted in contact with other cattle (OR 1.25, CI 1.06-1.47), housing young calves and adult cows in the same barn (OR 1.22, CI 1.08-1.38), having a permanent employee on the farm (OR 1.17, CI 1.04-1.31), having a group calving pen (OR 1.16, CI 1.03-1.32), escaped cattle from other farms that mingled with own cattle (OR 1.16, CI 1.01-1.33), and nearest distance to a non-dairy farm (OR 1.15, CI 1.03-1.28). Although the BVDV status of most dairy herds can be checked in an open register, approximately half of the farmers indicated that they purchased cattle from BVDV-free herds while they were actually purchasing from non-BVDV-free farms. Farmers should be stimulated to actively check the true BVDV status of the herd from which cattle are purchased to further reduce the risk of introduction. In addition, indirect contact with cattle from other farms through either the farmer or other on-farm staff should be avoided. It is strongly advised to work in these situations with proper biosecurity measures such as changing boots and coveralls. The results can be used to improve BVDV control programs to further decrease the prevalence.

Case-control study to identify management practices associated with morbidity or mortality due to bovine anaplasmosis in Mississippi cow-calf herds

Bovine anaplasmosis (BA) is a costly disease affecting the U.S. beef cattle industry. Chlortetracycline (CTC) in feed or mineral supplements is often used to control clinical signs of BA. The objective of this study was to determine if manage­ment practices, such as feeding CTC, are associated with ill­ness or death from BA in Mississippi cow-calf herds. Case and control herds were solicited from veterinary practices across Mississippi. Cases were herds with clinical BA diagnosed by a veterinarian within the previous calendar year. Controls were herds under the care of the same practice with no clini­cal BA diagnosed in the previous year. Blinded interviewers conducted telephone surveys of case and control herd owners. Management and biosecurity factors were tested for associa­tion with herd status using a logistic regression generalized linear mixed model with veterinary practice as a random vari­able. Twenty-two case and 25 control herds from 6 veterinary practices across Mississippi were interviewed, representing 22 counties. The average herd size was 132 for case herds, and 136 for control herds. Twenty case herds and 13 control herds fed CTC medicated mineral or feed. Providing CTC was associated with case herd status (OR = 9.2, 95% C.I. = 1.7-50.7). The association observed between case herds and feeding CTC might be because: 1) herds that had experienced previous BA morbidity and mor­tality subsequently began feeding CTC, or 2) some individual cattle consume enough CTC to achieve clearance of the per­sistent carrier state, thereby increasing risk of reinfection and clinical BA.

Seroprevalence and herd-level associated factors of pathogenic Leptospira spp. circulating locally in dairy cattle in Uruguay

Leptospirosis is a zoonotic disease of worldwide importance. In Uruguay, it is endemic in cattle and primarily affects people with occupational exposure to livestock. The aim of this study was to determine the national seroprevalence and associated factors of local pathogen Leptospires in dairy cattle. A cross-sectional study was carried out. Herds were stratified by size (1–50, 51–250, and > 250 cattle), and up to 60 dairy cows per herd were randomly selected. A total of 4269 serum samples from 101 dairy herds were analyzed by microscopic agglutination test (MAT). A two-stage sampling design was used to estimate population seroprevalence of Leptospira spp. In order to determine the factors associated with the disease, herds with at least 1 seropositive animal were considered as case herds. Seroprevalence of Leptospira was 27.80% with a 95% CI [21.06, 34.54] at the animal level and 86.92% with a 95% CI [80.00, 93.75] at the herd level. The serology confirms the predominance of serogroups Sejroe and Pomona in our herd with the presence of incidental leptospires infection, in smaller proportion, but with a wide distribution at farm level. The population size and purchasing replacement of cows on dairy farms were associated with infection at farm level. The serologic studies confirmed that exposure to Leptospira spp. is endemic in our herds, and the spreading over dairy herds. Although the movement of purchased females and the size of the herd were associated with the disease, more studies should be conducted, to better understand the epidemiology of the disease and to highlight the possible risks to public health, especially in rural workers, farmers and veterinarians.

Estimating the Effect of a Bovine Viral Diarrhea Virus Control Program: An Empirical Study on the Performance of Dutch Dairy Herds.

More and more European countries have implemented a bovine viral diarrhea virus (BVDV) control program. The economic effects of such programs have been evaluated in simulations, but empirical studies are lacking, especially in the final stage of the program. We investigated the economic (gross margin) and production effects (milk yield, somatic cell count, and calving interval) of the herds obtaining BVDV-free certification based on longitudinal annual accounting and herd performance data from Dutch dairy herds between 2014 and 2019, the final stages of the Dutch national BVDV-free program. This study was designed as a case-control study: two types of case herds were defined for two analyses. The case herds in the first analysis are herds where the BVDV status changed from “BVDV not free” to “BVDV free” during the study period. The not-free status refers to a herd that participated in the BVDV-free program but had not yet obtained the BVDV-free certification. In the second analysis, the case herds started participating in the Dutch BVDV-free program during the study period and obtained the BVDV-free certification. Control herds in both analyses were BVDV-free during the entire study period. Potential bias between the covariates of the two herd groups was reduced by matching case and control herds using the propensity score matching method. To compare the differences between case and control herds before and after BVDV-free certification, we used the time-varying Difference-in-Differences estimation (DID) methodology. The results indicate that there was no significant change in milk yield, somatic cell count, calving interval, and gross margin upon BVDV-free certification. There are several possible explanations for the non-significant effects observed in our study, such as the final stage of the BVDV control program, not knowing the true BVDV infection situation in case herds and not knowing if control measures were implemented in case herds prior to participating in the BVDV-free program. In our study, the effects of BVDV-free certification might have been underestimated, given that the Dutch BVDV control program became mandatory during the study period, and some of the case herds might have never experienced any BVDV infection. The results of this study suggest that in the final stage of the BVDV control program, the program may no longer have a clear benefit to the herd performance of participating dairy herds. When designing national programs to eradicate BVDV, it is therefore important to include incentives for such farms to motivate them to join the program.

Bovine Brucellosis in Gauteng, South Africa: Seroprevalence amongst Cattle Handlers and Variables Associated with Seropositive Cattle Herds, 2014-2016.

In South Africa, the prevalence of cattle handler exposure to Brucella on cattle farms is unknown and risk factors and cattle symptoms associated with infected cattle herds are unavailable. To address this gap, a case-control study of cattle herds was conducted in Gauteng province and farm workers and veterinary officials were tested for exposure to Brucella. Seroprevalence amongst farm workers exposed to case herds ranged from 4.0% (BrucellaCapt®) to 16.7% (IgG ELISA®), compared to those exposed to control herds, where seroprevalence ranged from 1.9% (BrucellaCapt®) to 5.7% (IgG ELISA®). Seroprevalence amongst veterinary officials was significantly greater compared to farm workers exposed to case herds for the outcome RBT+ IgM- IgG+ (OR = 11.1, 95% CI: 2.5–49.9, p = 0.002) and RBT- IgM- IgG+ (OR = 6.3, 95% CI: 2.3–17.3, p < 0.001). Risk factors associated with being an infected herd were: being a government-sponsored farm vs. private farm (OR 4.0; 95% CI: 1.4–11.3; p = 0.009), beef vs. dairy herd (OR 7.9; 95% CI: 1.4–44.9; p = 0.020), open vs. closed herd (OR 3.3; 95% CI: 1.1–10.4; p = 0.038) and the presence of antelope on the farm (OR 29.4; 95% CI: 4.0–218.2; p = 0.001). Abortions (OR = 5.1; 95% CI: 2.0–13.3; p < 0.001), weak calves in the herd (OR = 8.0; 95% CI: 2.6–24.4; p < 0.001), reduction in number of calves born (OR = 9.0; 95% CI: 2.1–43.6; p < 0.001), reduction in conception rate (OR = 3.9; 95% CI: 0.8–18.3; p = 0.046), hygromas in cattle (p = 0.011) and farmers reporting brucellosis-like symptoms in their farm workers or in him/herself (OR = 3.4; 95% CI: 1.3–8.7; p = 0.006) were more likely to be associated with Brucella infected herds than control herds. This evidence can be used in strategic planning to protect both human and herd health.

Possible causes of aberrations in adverse grouping behavior of dairy cows: A field study

In the Dutch national surveillance system, an increasing number of reports were received in the summer of 2017 from farmers about unusual behavior of their cows. The cows were grouping during the day in summer in one part of the barn and did not move for several hours, which, according to the farmers, led to reduced food and water intake and lying time and resulted in decreased milk production and increased risk of lameness. Many farmers perceived magnetic fields from, for instance, high-voltage lines, automated milking systems, or solar panels as possible causes for the behavior of their cows. Our aim for the study was to study potential factors such as magnetic fields and other factors such as barn climate and insect burden for adverse grouping behavior of dairy cows in the barn. For each case herd, 2 control herds were selected in the same postal area code. A case was a herd in which cattle grouped at least on 7 occasions in a month for several hours. In a control herd, the cows were in the barn during the same time period as in the matching case herd but did not show adverse grouping behavior. A questionnaire was administered by telephone in 31 case herds and 62 control herds. The questionnaire gathered information on behavior of the cows and potential risk factors. In addition, data on the distance of the herd to high-voltage lines was obtained. From a total of 74 variables, all variables with a P-value ≤0.10 were included in full multivariable logistic regression model. Backward selection was carried out at P ≤ 0.10. The grouping behavior of the cows started in most herds in June, was seen only during the day, and lasted mostly 6 to 8 h, with cows often grouped in the northern part of the barn. Identified risk factors appeared to be recently constructed barns, measured stray voltage in barns, and presence of fans in barns. Given the cross-sectional design of the case-control study, causality for these risk factors leading to adverse behavior of the cows could not be proven. Dissemination of the results to farmers hopefully results in measures that can prevent the unusual grouping behavior of cows.

Actinobacillus pleuropneumoniae Eradication with Enrofloxacin May Lead to Dissemination and Long-Term Persistence of Quinolone Resistant Escherichia coli in Pig Herds.

Norway has a favourable situation with regard to health status and antimicrobial usage in the pig production sector. However, one of the major disease-causing agents in the commercial pig population is Actinobacillus pleuropneumoniae (APP). In some herds, APP eradication has been performed by using enrofloxacin in combination with a partial herd depopulation. The aim of this study was to investigate the long-term effects of a single treatment event with enrofloxacin on the occurrence of quinolone resistant Escherichia coli (QREC). The study was designed as a retrospective case/control study, where the herds were selected based on treatment history. Faecal samples were taken from sows, gilts, fattening pigs and weaners for all herds where available. A semi-quantitative culturing method was used to identify the relative quantity of QREC in the faecal samples. A significant difference in overall occurrence and relative quantity of QREC was identified between the case and control herds, as well as between each animal age group within the case/control groups. The results indicate that a single treatment event with enrofloxacin significantly increased the occurrence of QREC in the herd, even years after treatment and with no subsequent exposure to quinolones.

Herd-level risk factors for chronic pleurisy in finishing pigs: a case-control study

BackgroundChronic pleurisy is a common finding in slaughtered pigs in post-mortem meat inspection. The prevalence of pleurisy has been increasing during the last decade also in Finland. The aim of this prospective case-control study was to search for environmental, infectious and management-related herd-level risk factors for pleurisy in the slaughterhouse. Altogether 46 Finnish pig herds, including 25 control (low pleurisy prevalence in meat inspection) and 21 case (high pleurisy) herds, were enrolled in the study and visited during the tenth week of the rearing period of finishing pigs. Herd personnel were asked about basic herd information, management and environmental factors. Selected pigs were examined clinically, environmental parameters were measured and 15 blood samples per herd were taken during herd visits. Antibodies against Actinobacillus pleuropneumonia serotype 2 (APP2) and ApxIV toxin and swine influenza virus were measured. After the slaughter of study pigs, meat inspection results of the batch were gathered from slaughterhouses. Multivariate logistic regression model was built to identify possible risk factors for a herd to be a case herd (i.e. having high pleurisy values).ResultsFinishing herd type and herd size were observed to act as risk factors. None of clinical signs of pigs, management-related factors or environmental measurements were associated with herd status.ConclusionsAs previously known, in endemic and subclinical infections such as APP, herd factors are important, but detailed risk factors seem to be difficult to identify.

Искусственный интеллект на службе государства: аргументы «за» и «против»

The purpose of the article is to identify the advantages of introducing artificial intelligence into life and potential threats to its use using the example of leading countries in this field - the USA, China and the UK. Research methods such as case herds and comparative studies have been chosen as the main ones. With their help, the use of artificial intelligence technologies in the field of politics and public administration, domestic and foreign policy and ensuring national security was analyzed. The goals of using artificial intelligence technologies in the power and management sphere of different countries are indicated. The scope of artificial intelligence technologies application is considered. The role of the National Strategy for the Development of Artificial Intelligence in Russia, adopted in 2019, was noted. Arguments are formulated "for" and "against" the use of artificial intelligence. It is stated that at present artificial intelligence has become an integral element of state and social development. Over time, it will only gain momentum and once again become a topic for discussions of scientists, politicians and public figures, as artificial intelligence technology gradually become part of the life of society.

Streptococcus suis in Swedish grower pigs: occurrence, serotypes, and antimicrobial susceptibility

BackgroundStreptococcus suis is a major cause of meningitis, arthritis, and pneumonia in pigs worldwide, and an emerging pathogen in humans. In Sweden, S. suis has previously received little attention but has in recent years become increasingly recognized as affecting the pig production. The aim of the present study was to investigate the occurrence, serotypes and antimicrobial susceptibility of S. suis in Swedish grower pigs from herds with and without reported S. suis associated disease, as well as possible associations between S. suis associated disease and selected environmental and production factors. Swab samples were taken from the tonsils of clinically healthy 8–13-week-old grower pigs from ten case herds and ten control herds. Isolates were cultured, identified using MALDI–TOF MS, and serotyped using latex agglutination. The antimicrobial susceptibility of 188 isolates was tested using broth microdilution. Production data was gathered and environmental parameters were measured on the farms.ResultsStreptococcus suis was isolated from 95% of the sampled pigs in both the case and the control herds. Serotypes 3, 4, 5, 7, 9, 10, 11, 15, 16, and 17–34 were detected, although a majority of the isolates (81.5%) were non-typeable. There was less diversity among the serotypes isolated from the case herds than among those from the control herds; four and nine different serotypes, respectively. Isolates resistant to penicillin (3.8%) were reported for the first time in Sweden. Tetracycline resistance was common (88.4%). No association was noted between the production and the environmental factors investigated, and the carriership of S. suis.ConclusionsThe carriership of S. suis was found to be higher in clinically healthy Swedish pigs than previously estimated, and for the first time, the presence of Swedish isolates resistant to penicillin was reported. Many of the most commonly disease-associated serotypes, e.g. serotypes 2, 9, 3, and 7, were detected in healthy grower pigs although further studies are needed to investigate the virulence of these isolates.

Epidemiological study of neosporosis in Uruguayan dairy herds

Neosporosis is one of the leading causes of abortion in cattle worldwide, posing a great economic burden on cattle producers. The aim of this study was to determine the national seroprevalence and putative risk factors of Neospora caninum (N. caninum) in dairy cattle in Uruguay. A cross-sectional study was carried out. Herds were stratified by size (1-50, 51–250, and >250 cattle) and up to 60 dairy cows per herd were randomly selected. Four thousand two hundred twenty-three serum samples from 102 dairy herds were analyzed by indirect ELISA test, under the manufacturer's recommendations. In addition, the herdsman was surveyed and a population study was carried out. The in degree data, geographical coordinates, and seroprevalence of bovine viral diarrhea, enzootic bovine leukemia and infectious bovine rhinotracheitis were available for each herd. A sampling design was used to estimate population seroprevalence of N. caninum. In order to determine the factors associated with the disease, herds with an intra-herd seroprevalence over 20% were considered as case herds. Seroprevalence of N. caninum was 22.3% (95% CI: 18.7-25.9 %) and 96.0% (95% CI: 92.1-99.8%) at the animal and herd level, respectively. The number of dogs on the dairy farms were associated with infection levels (OR: 1.43, 95% CI: 1.02 to 2.03). It was concluded that N. caninum is endemic in the country, and is spreading over dairy herds. Although this study showed evidence that the number of dogs were associated with high levels of infection, more studies should be conducted, to better understand the epidemiology of the disease and thus develop efficient control measures.

Herd-level factors associated with detection of calves persistently infected with bovine viral diarrhoea virus (BVDV) in Irish cattle herds with negative herd status (NHS) during 2017

A compulsory national BVD eradication programme commenced in Ireland in 2013. Since then considerable progress has been made, with the animal-level prevalence of calves born persistently infected (PI) falling from 0.67 % in 2013 to 0.06 % in 2018. The herd-level prevalence fell from 11.3 % in 2013 to 1.1 % in 2018. In the Irish programme, herds in which all animals have a known negative status and which have not contained any PI animals for 12 months or more are assigned a negative herd status (NHS). While considerable progress towards eradication has been made, PI calves have been identified in a small proportion of herds that had previously been assigned NHS. Given this context, a case-control study was conducted to investigate potential risk factors associated with loss of NHS in 2017. 546 herds which had NHS on 1 January 2017 and lost that status during 2017 (case herds) were matched with 2191 herds (control herds) that retained their NHS status throughout 2017. Previous history of BVD infection, herd size, herd expansion, the purchase of cattle including potential Trojan cattle and the density of BVD infection within 10 km of the herd emerged as significant factors in a multivariable logistic regression model. This work adds to the evidence base in support of the BVD eradication programme, particularly establishing why BVD re-emerged in herds which had been free of BVD for at least the previous 12 months prior to the identification of a BVD positive calf. This information will be especially important in the context of identifying herds which may be more likely to contain BVD positive animals once the programme moves to herd-based serology status for trading purposes in the post-eradication phase.

A descriptive study of on-farm biosecurity and management practices during the incursion of porcine epidemic diarrhea into Canadian swine herds, 2014.

Porcine epidemic diarrhea virus (PEDV) emerged into Canada in January 2014, primarily affecting sow herds. Subsequent epidemiological analyses suggested contaminated feed was the most likely transmission pathway. The primary objective of this study was to describe general biosecurity and management practices implemented in PEDV-positive sow herds and matched control herds at the time the virus emerged. The secondary objective was to determine if any of these general biosecurity and farm management practices were important in explaining PEDV infection status from January 22, 2014 to March 1, 2014. A case herd was defined as a swine herd with clinical signs and a positive test result for PEDV. A questionnaire was used to a gather 30-day history of herd management practices, animal movements on/off site, feed management practices, semen deliveries and biosecurity practices for case (n = 8) and control (n = 12) herds, primarily located in Ontario. Data was analyzed using descriptive statistics and random forests (RFs). Case herds were larger in size than control herds. Case herds had more animal movements and non-staff movements onto the site. Also, case herds had higher quantities of pigs delivered, feed deliveries and semen deliveries on-site. The biosecurity practices of case herds were considered more rigorous based on herd management, feed deliveries, transportation and truck driver practices than control herds. The RF model found that the most important variables for predicting herd status were related to herd size and feed management variables. Nonetheless, predictive accuracy of the final RF model was 72%.

Risk factors for the infection with Brachyspira hyodysenteriae in pig herds

Swine dysentery (SD), caused by infection with Brachyspira hyodysenteriae, is a serious disease in pig production worldwide. Quantitative risk factors triggering the occurrence of infection are unknown. The present case-control study aimed at identifying major risk factors related to presence of B. hyodysenteriae in pig herds. Twenty case herds and 60 randomly selected control herds with a minimum herd size of ‘10 sows/ 80 fattening pigs’ were examined by means of a questionnaire-based interview and a herd examination. Herds with previous eradication of SD were excluded. Logistic regression models revealed that the ‘positive/suspicious SD status of source herds’, the regular application of treatment, purchasing more than 4 batches/ year, contact to foxes, diagnostics performed during last 12 months, liquid feeding systems, rats on farm, and >250 fatting places were associated with higher chances of a herd to be infected. On the contrary, having different sources of grower pigs within one batch, the presence of raptor birds and the presence of martens in the region were associated with fewer chances of being infected. The final multivariable logistic regression model identified purchasing more than 4 batches/ year (OR = 7.5, 95 % CI 1.8–54.3) and contact to foxes (OR = 5.9; 97.5 % CI 1.2–34.6) as the two main risk factors in our study. ‘More than 4 batches/ year’ implies continuous herd management supporting persistence of B. hyodysenteriae in an infected herd, but also increased number of purchases each increasing the risk of B. hyodysenteriae introduction by carrier pigs or transport vehicles. Foxes might be infected with B. hyodysenteriae by feeding on positive piglets and rodents. Besides, ‘contact to foxes’ might represent a lack in biosecurity. In conclusion, the risk factors detected underline the importance of biosecurity in SD prevention and control.

Network analyses using case-control data to describe and characterize the initial 2014 incursion of porcine epidemic diarrhea (PED) in Canadian swine herds

The overall objective of this study was to describe the contact structure and animal movement patterns of porcine epidemic diarrhea (PED) case herds and matched control herds during the initial incursion of PEDV in Canada, and to evaluate possible mechanisms of spread during this period. Possible mechanisms of spread included transmission through a common-source, herd-to-herd transmission, and transmission due to low biosecurity. Three hypotheses were evaluated by assessing: 1) whether feed supplier, semen supplier and/or animal transportation company networks contained a higher proportion of case herds compared to randomly permuted networks, 2) whether the proportion of case herds in the giant weak component differed from randomly permuted networks, and 3) whether external herd biosecurity, defined as the number of mean contacts with other herds in a one-mode network, was different between case and control herds. The study period for recruiting case and control herds was from January 22, 2014 to March 1, 2014, and a 30-day history of each participating site was collected using a questionnaire. The study included swine herds located in central and eastern Canadian provinces. Multiple two-mode networks with swine herds and service suppliers were constructed. This included feed suppliers, animal movement, animal transportation companies, semen suppliers and a complete network with all service providers.The complete network consisted of 145 nodes. There were a total of 765 edges in the complete network and majority were between feed suppliers and primary herds 29.8% (228/765). The proportion of case herds in the largest feed supplier network was higher than what was expected using randomly permuted networks, suggesting that the likely mechanism of spread during this phase was a common-source through the feed network. A single feed supplier (FS1) had the highest out-degree and outgoing contact chain indicating its importance in disease spread throughout the feed and complete networks. Network descriptive measures, as well as the results of the hypotheses testing indicate little significance in the roles of animal movement, animal transportation companies, and semen suppliers during the initial phase of the 2014 Canadian PED outbreak.

A retrospective epidemiological analysis of shared risk factors for bovine trichomoniasis and bovine genital campylobacteriosis in La Pampa province (Argentina)

The venereal diseases bovine trichomoniasis (BT) and bovine genital campylobacteriosis (BGC) cause economic losses in endemic areas like La Pampa province in Argentina, where beef cattle are usually managed extensively. The eradication of both diseases is a priority in Argentine. The aim of this case-control study was to identify shared and specific risk factors of both diseases from the data obtained from the Provincial Program for the Control and Eradication of BT and BGC in La Pampa (PCE). The study population included 5777 breeding beef herds tested for BT and BGC in 2013. The study comprised 3481 herds that were surveyed in situ by official PCE veterinarians, distributed as follows: 3159 negative herds (with no BT or BGC positive bulls), 121 BT case herds (with at least a BT positive bull), 170 BGC case herds (with at least a BGC positive bull) and 31 BT and BGC co-infected case herds (with at least a positive bull for each disease). Three multivariable analyses were performed in order to identify the risk factors using a logistic regression model. Results showed that the risk factors shared by both diseases were the number of bulls (OR for BT = 1.03, 95% CI: 1.02–1.04, p < 0.001; OR for BGC = 1.02, 95% CI: 1.01–1.03, p < 0.001; OR for BT and BGC co-infection = 1.02, 95% CI: 1.01–1.04, p = 0.003) and the presence in the previous year of each disease (OR for BT = 18.69, 95% CI: 11.82–29.57, p < 0.001; OR for BGC = 4.65, 95% CI: 3.18–6.81, p < 0.001; OR for BT and BGC co-infection = 39.18, 95% CI: 16.72–91.80, p < 0.001). Disease-specific risk factors were continuous breeding season for BT (OR = 1.59, 95% CI: 1.04–2.47, p = 0.034), and inadequate condition of the fences for BGC (OR = 1.51, 95% CI: 1.06–2.15, p = 0.022). An integrated approach to venereal disease management needs to consider the risk characteristics identified in this study. This could lead to reduce both diseases and improve the efficiency of BT and BGC control activities in La Pampa.

Trends and Predictors of Large Tuberculosis Episodes in Cattle Herds in Ireland.

Persistence of bovine tuberculosis (bTB) in cattle is an important feature of Mycobacterium bovis infection, presenting either as herd recurrence or local persistence. One risk factor associated with the risk of recurrent episodes is the severity of a previous bTB episode (severity reflecting the number of bTB reactors identified during the episode). In this study, we have sought to identify predictors that can distinguish between small (less severe) and large (more severe) bTB episodes, and to describe nationally the severity of bTB episodes over time. The study included descriptive statistics of the proportion of episodes by severity from 2004 to 2015 and a case-control study. The case-control study population included all herds with at least one episode beginning in 2014 or 2015, with at least two full herd tests during the episode and a minimum herd-size of 60 animals. Case herds included study herds with at least 13 reactors whereas control herds had between 2 to 4 (inclusive) reactors during the first 2 tests of the episode. A logistic regression model was developed to identify risk factors associated with a large episode. Although there has been a general trend towards less severe herd bTB episodes in Ireland over time (2004–2015), the proportion of large episodes has remained relatively consistent. From the case-control study, the main predictors of a large episode were the year the episode started, increasing herd-size, previous exposure to bTB, increasing bTB incidence in the local area, an animal with a bTB lesion and a bTB episode in an associated herd. Herds that introduced more animals were more likely to have a smaller bTB episode, reflecting the reduced risk of within-herd transmission when an episode was due to an introduced infected bTB animal. Some of the risk factors identified in this study such as reactors in previous bTB episodes, herds with an associated herd undergoing a bTB episode, herds in high incidence areas etc. may help to target future policy measures to specific herds or animals for additional surveillance measures. This information has important policy implications.

Case-control study to determine herd-level risk factors for bovine respiratory disease in nursing beef calves on cow-calf operations.

OBJECTIVE To determine herd-level risk factors for bovine respiratory disease (BRD) in nursing beef calves. DESIGN Matched case-control study. SAMPLE 84 cow-calf operations in Nebraska, North Dakota, and South Dakota. PROCEDURES Case herds were herds that treated at least 5% of the calf crop for BRD prior to weaning. Control herds were herds that treated < 0.5% of the calf crop for BRD prior to weaning. Each case herd was matched with 2 control herds on the basis of veterinary practice and enrollment year. Herd owners or managers were interviewed by telephone, and characteristics and practices associated with case status were determined by multivariable conditional logistic regression. RESULTS 30 case herds and 54 control herds were evaluated. Increasing herd size, frequent pasture movement for intensive grass management (intensive grazing), and use of estrus-synchronization programs were significantly associated with herd status. The odds of being a case herd for herds with 150 to 499 cows was 7.9 times and that for herds with ≥ 500 cows was 12 times, compared with the odds of being a case herd for herds with < 150 cows. The odds of being a case herd for herds that used intensive grazing was 3.3 times that for herds that did not use intensive grazing. The odds of being a case herd for herds that used an estrus-synchronization program was 4.5 times that for herds that did not use an estrus-synchronization program. CONCLUSIONS AND CLINICAL RELEVANCE Management practices can be associated with an increase in the BRD incidence in nursing beef calves. Modification of management practices may decrease BRD incidence in nursing calves for herds in which it is a problem.

Risk factors associated with Mycobacterium avium subsp. paratuberculosis herd status in Québec dairy herds

Paratuberculosis is a chronic and contagious enteric disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Control of paratuberculosis is justified given the associated economic losses and the potential role of MAP in Crohn’s disease in humans. Management practices that limit exposure of susceptible animals to MAP are more effective at reducing disease prevalence than testing and culling infected cows. The objective of this retrospective case-control study was to study the association between management practices and MAP status in dairy herds in Québec, Canada. A total of 26 case herds (MAP had been isolated from at least 1 environmental sample in each herd) and 91 control herds (no clinical cases of paratuberculosis and negative on 2 consecutive yearly environmental samplings) were selected among herds enrolled in the Québec Voluntary Paratuberculosis Control Program. A risk assessment questionnaire, completed at enrolment, was available for the selected herds. Culture of MAP was achieved using liquid media and the BACTEC 960 detection system. Multivariable logistic regression was used to evaluate the association between selected risk factors and MAP herd status. Herd size (OR = 1.17; 95% CI: 1.02-1.33) and proportion of cows purchased per year in the last 5 years (OR = 5.44; 95% CI: 1.23-23.98) were significantly associated with a positive MAP herd status.The management risk factors identified in the present study are in accord with previous studies. Management practices aiming to prevent the introduction of new animals into the herd and to reduce the contact of newborn calves with adult animals or their feces are key elements to minimize MAP introduction and transmission into a herd. These elements should be prioritized in control programs.