Bovine leukosis virus, bovine viral diarrhea, and bovine neosporosis seroprevalence in specialized dairy herds in Antioquia-Colombia.

Enzootic bovine leukosis (EBL) is a chronic infectious disease caused by the bovine leukosis virus (BLV), a Deltaretrovirus. Bovine viral diarrhea (BVD) is an infectious disease caused by a pestivirus. Bovine neosporosis is caused by the obligate intracellular parasite Neospora caninum (Nc). These pathogens can have horizontal (postnatal) or vertical (transplacental) transmissions and affect the productive and reproductive performance of infected bovines. This work aimed to detect BLV, BVD, and Nc seroprevalence in specialized dairy cattle from the north, east, and Aburrá Valley regions of the Department of Antioquia, the highest in milk production regions in Antioquia. A total of 599 blood samples, obtained from 53 specialized dairy cattle herds, were evaluated by the ELISA test. The results revealed a seroprevalence of 41.13% for BLV (242/599), 28.48% (163/599) for Nc, and 22.7% (132/599) for BVD. Regarding the regional seroprevalence evaluation, BLV was found in 47.02% of the samples from the east, 36.87% from the north, and 46.02% from the Aburrá Valley. Nc was found in 31.03% of the samples from the east, 24.26% from the north, and 36.63% from Aburrá Valley. BVD was found in 21.62% of the samples from the east, 25.03% from the north region, and 10.39% of the samples from the Aburrá Valley. It is highlighted by these results that the north region, with the highest milk production in Antioquia, had the lowest BLV and Nc seroprevalences but the highest seroprevalence of BVD. BLV has increased in Antioquia in recent years, and as an immunosuppressive infection, opportunities for other pathogens are created by it. A significant statistical difference was found in the average prevalence of the pathogens according to the municipality, cattle breed, and region of origin of the sample. The seroprevalence of these pathogens in specialized dairy herds in Antioquia can be classified as medium-low. However, it is recommended that biosecurity practices should be maximized to avoid the spread of these pathogens due to the variability detected in the region, municipality, breed group, and herd age. The rapid and efficient diagnosis of these three pathogens through reliable methodologies will allow for the control of dissemination in dairy herds.

Antimicrobial Resistance and Distribution of Staphylococcus spp. Pulsotypes Isolated from Goat and Sheep Bulk Tank Milk in Southern Spain.

Bulk tank milk from 58 dairy goat and sheep flocks located in southern Spain was examined to determine the prevalence and distribution of Staphylococci. A total of 45 isolates were obtained and characterized to determine the species, antimicrobial resistance profile, and genetic similitude by pulse-field gel electrophoresis (PFGE) using SmaI. Staphylococcus aureus isolates were confirmed by polymerase chain reaction (PCR) analysis of nuc, and resistance to methicillin was determined by PCR analysis of mecA. A total of 10 different staphylococcal species were identified, 22.2% and 77.8% of which were coagulase positive and negative, respectively. Twenty-two (48.89%) isolates were resistant to at least one antimicrobial agent. Higher antimicrobial resistance values were obtained against tetracycline (28.9%) and penicillin (22.2%). Two isolates (S. aureus and Staphylococcus lentus) were resistant to cefoxitin; however, none of the 45 isolates harbored mecA. Thirty pulsotypes were detected by PFGE. Interestingly, some isolates of S. aureus, S. lentus, Staphylococcus simulans, and Staphylococcus caprae showed high genetic similarity (>80%). These data suggest that genetically similar staphylococcal isolates circulate among goat and sheep dairy herds, and their different resistance patterns could be influenced by the management systems used.

Comparison of rumen bacterial communities in dairy herds of different production.

BACKGROUND: The purpose of this study was to compare the rumen bacterial composition in high and low yielding dairy cows within and between two dairy herds. Eighty five Holstein dairy cows in mid-lactation (79-179 days in milk) were selected from two farms: Farm 12 (M305 = 12,300 kg; n = 47; 24 primiparous cows, 23 multiparous cows) and Farm 9 (M305 = 9700 kg; n = 38; 19 primiparous cows, 19 multiparous cows). Each study cow was sampled once using the stomach tube method and processed for 16S rRNA gene amplicon sequencing using the Ion Torrent (PGM) platform. RESULTS: Differences in bacterial communities between farms were greater (Adonis: R2 = 0.16; p < 0.001) than within farm. Five bacterial lineages, namely Prevotella (48-52%), unclassified Bacteroidales (10-12%), unclassified bacteria (5-8%), unclassified Succinivibrionaceae (1-7%) and unclassified Prevotellaceae (4-5%) were observed to differentiate the community clustering patterns among the two farms. A notable finding is the greater (p < 0.05) contribution of Succinivibrionaceae lineages in Farm 12 compared to Farm 9. Furthermore, in Farm 12, Succinivibrionaceae lineages were higher (p < 0.05) in the high yielding cows compared to the low yielding cows in both primiparous and multiparous groups. Prevotella, S24-7 and Succinivibrionaceae lineages were found in greater abundance on Farm 12 and were positively correlated with milk yield. CONCLUSIONS: Differences in rumen bacterial populations observed between the two farms can be attributed to dietary composition, particularly differences in forage type and proportion in the diets. A combination of corn silage and alfalfa silage may have contributed to the increased proportion of Proteobacteria in Farm 12. It was concluded that Farm 12 had a greater proportion of specialist bacteria that have the potential to enhance rumen fermentative digestion of feedstuffs to support higher milk yields.

Bovine mastitis: prevalence, risk factors and isolation of Staphylococcus aureus in dairy herds at Hawassa milk shed, South Ethiopia.

BACKGROUND: Mastitis is a disease of major economic importance in dairy industry worldwide. It is of particular concern in developing countries like Ethiopia, where milk and milk products are scarce. The objectives of the study were to estimate the prevalence of mastitis, identify the cow-and herd-level potential risk factors and isolate Staphylococcus aureus, one of etiological agents for contagious mastitis, from cows positive for mastitis. A total of 529 lactating cows selected randomly from 95 herds were screened by California mastitis test (CMT) for sub-clinical mastitis. Also 172 milk samples collected from CMT positive cows were cultured for isolation of S. aureus. RESULTS: Based on CMT result and clinical examination, the prevalence of mastitis at herd-level was 74.7% (95% CI: 64.5, 82.8). The corresponding cow-level prevalence was 62.6% (95% CI: 58.3, 66.7), of which 59.2 and 3.4% were sub-clinical and clinical mastitis cases, respectively. S. aureus was isolated from 51.2% of the milk samples cultured and 73.2% of the herds affected with mastitis. In the multivariable logistic regression model, the herd-level factors significantly associated (p < 0.05) with the presence of mastitis were herd size, bedding material, and milking mastitic cows last, while at cow-level, breed, parity, stage of lactation, udder and leg hygiene, and teat end shape were noted to have a significant effect on mastitis occurrence. CONCLUSION: The very high prevalence of mastitis, more importantly the sub-clinical one, in the herds examined revealed the huge potential economic loss the sector suffers. Perhaps this was attributed to lack of implementation of the routine mastitis prevention and control practices by all of the herd owners. The findings of this study warrants the need for strategic approach including dairy extension that focus on enhancing dairy farmers' awareness and practice of hygienic milking, regular screening for sub-clinical mastitis, dry cow therapy and culling of chronically infected cows.

Detection of Clostridium botulinum neurotoxin genes (A-F) in dairy farms from Northern Germany using PCR: A case-control study.

Classical botulism in cattle mainly occurs after ingestion of feed contaminated with preformed toxin. In 2001 a form of botulism ("visceral botulism") was postulated to occur after ingestion of Clostridium (C.) botulinum cells or spores, followed by colonization of the intestine, and local production of botulinum neurotoxin (BoNT) causing chronic generalized disease. To verify the potential role of C. botulinum in the described syndrome, a case-control study was conducted, including 139 farms. Fecal samples, rumen content, water and silage samples were collected on each farm. Real time BoNT gene PCR assays were conducted after enrichment in RCM (Reinforced Clostridial Medium) at 37 °C and conventional PCRs after enrichment in MCM (Modified Cooked Meat Medium) at 30 °C. Furthermore, a direct detection of BoNT genes without prior enrichment was attempted. BoNT A, B, C, D, E and F genes were detected in animal samples from 25 (17.99%), 3 (2.16%), 0 (0.0%), 2 (1.44%), 1 (0.72%), and 3 (2.16%) farms, respectively. Eleven feed samples were positive for BoNT A gene. By enrichment a significant increase in sensitivity was achieved. Therefore, this should be an essential part of any protocol. No significant differences regarding BoNT gene occurrence could be observed between Case and Control farms or chronically diseased and clinically healthy animals within the particular category. Thus, the postulated form of chronic botulism in cows could not be confirmed. This study supports the general opinion that C. botulinum can occasionally be found in the rumen and intestine of cows without causing disease.

A bulk milk tank study to detect evidence of spread of Schmallenberg virus infection in the south-west of Ireland in 2013.

BACKGROUND: Schmallenberg virus (SBV) was first detected in Germany in November 2011. Confirmation of infection in Ireland was reported on October 30(th) 2012. The results of a national serological survey carried out in early 2013 suggested that the first introduction of SBV into Ireland probably occurred in the south or southeast of Ireland in the spring or summer of 2012, with subsequent spread eastwards and northwards. It was unclear at that stage whether the virus had survived the winter period and would continue to spread in 2013. The purpose of this study was to monitor the spread of the virus in the mid-west region through the summer and autumn of 2013 using bulk tank milk from selected dairy herds. FINDINGS: Seventy two dairy farmers were recruited to participate in the bulk milk tank study. Each farmer agreed to collect a bulk tank milk sample on a weekly basis from early June. A total of 988 samples were received between June 5(th) and December 3(rd) 2013 and these were analysed using an indirect ELISA test. Of the initial set of 72 samples received between June 5(th) and July 16(th), nine were positive, one was inconclusive and 62 were negative. By the end of the study in early December 2013 only one new farm turned positive. This was the farm that had initially tested inconclusive. CONCLUSION: The study results suggest that the anticipated spread of SBV across Ireland from the south and south-east did not occur during 2013.

Seroepidemiology of bovine alphaherpesvirus 1 (BoAHV-1) in commercial and smallholder dairy herds in north Shewa, central highlands of Ethiopia.

Bovine alphaherpesvirus 1 (BoAHV-1) is the most important respiratory and reproductive disease-causing pathogen in dairy cattle. Despite BoAHV-1 has become widespread and a major challenge to the dairy industry, little is known about its epidemiology in dairy herds in Ethiopia. A cross-sectional study was conducted from November 2022 to May 2023 to determine the seroprevalence and potential risk factors associated with BoAHV-1 seropositivity in dairy herds in North Shewa, the central highlands of Ethiopia. A total of 511 blood samples were collected from randomly selected cattle herds (n = 142) and examined antibodies against BoAHV-1 using ELISA test. A retrospective survey was also done to gather information related to reproductive disorders. The overall seroprevalence of BoAHV-1 was 61.84% (95% CI: 57.53-65.97) at the animal level and 85.21% (95% CI: 78.28-90.21) at the herd level. Multivariable logistic analysis revealed that the risk of being BoAHV-1 seropositive was nine times higher in cows older than six years (OR = 9.16; 95% CI: 3.09-27.16; P = 0.000), five times higher (OR = 4.51; 95% CI: 1.23-16.53; P = 0.019) in cows with a history of abortion, three times higher (OR = 2.75; 95% CI: 1.72-4.22; P = 0.029) in cows with a history of retained fetal membrane, and three times higher (OR = 2.83; 1.86-9.31; P = 0.03) in animals with clinical signs of ocular and/or nasal discharge. This study demonstrates a significant circulating of BoAHV-1 in the dairy cattle population in study districts. Thus, a comprehensive approach that includes strict farm biosecurity and vaccination should be practiced for effective BoAHV-1 control and prevention and to promote the growing dairy industry in the central highlands of Ethiopia.

Escherichia coli and Salmonella enterica isolated from Egyptian dairy cattle herds: The prevalence and molecular characteristics.

Background: The pathogens Escherichia coli and Salmonella enterica that caused substantial health problems and financial losses were believed to have originated primarily from Egypt's dairy farms. Aim: The purpose of this study was to ascertain the occurrence of E. coli and S. enterica in three large dairy farms located in the Egyptian governorate of Sharkia. Furthermore, biochemical and serological characteristics of the isolated isolates were described. Further analysis revealed that several E. coli serovars had the genes stx1, stx2, eaeA, and hylA, while invA, stn, and hilA genes were found in several S. enterica serotypes using a multi-plex PCR. Methods: A total of 540 samples of fresh raw cow milk, water, feedstuffs, feces, (108 each), as well as swabs from feeders, milker hands and cattle crushes (36 each ), were gathered and analyzed. Results: The recovery of E. coli from various sampling sources was shown to have an overall prevalence of 62.2% (336/540) in the results. Fecal samples had isolated S. enterica, with a frequency of 0.74% (4/540). The existence of various groups of serovars, such as O26, O44, O55, O78 and O111 for E. coli and Salmonella enteritidis, Salmonella typhimurium and Salmonella inganda for S. enterica was revealed by serological identification of the two species. However, it was discovered that a number of E. coli serovars had much higher percentages of the eaeA and hylA genes as well as shiga-toxin types 1 and 2 (stx1 and stx2). The presence of the invA gene, a diagnostic marker for S. enterica was 100% across all serovars. Salmonella enteritidis possessed both the enterotoxin gene (stn) and the hyper-invasive locus gene (hilA). Salmonella typhimurium had the hilA gene, whereas S. inganda had the stn gene. Conclusion: Escherichia coli and S. enterica recovered in this study have significant genetic risk factors for high pathogenicity and virulence, posing a real threat to dairy population productivity and health, which could spread to the general public through milk.

Semi-Quantitative Biosecurity Assessment Framework Targeting Prevention of the Introduction and Establishment of Salmonella Dublin in Dairy Cattle Herds.

An increasing average herd size and complexity in farm structures call for a higher level of biosecurity. It can reduce the risk of introducing and establishing pathogens with multiple-pathway and indirect spread mechanisms, such as Salmonella Dublin, a pathogen with an increasing occurrence in dairy cattle farms across different countries and continents. Therefore, this study aimed to use existing knowledge to develop a framework with a supporting tool allowing for a time-efficient, yet comprehensive, assessment of biosecurity measures that can help prevent the introduction and establishment of S. Dublin in dairy herds. Based on the literature review, a seven-step biosecurity assessment framework was developed and evaluated in collaboration with biosecurity experts. The resulting framework includes a weighted semi-quantitative assessment method with a scoring guide in an electronic supporting tool for 12 biosecurity sections assessed through on-farm observations and farmer interviews. The framework and tool provide a novel approach to comprehensively assess the overall (mainly external) on-farm biosecurity level by a trained biosecurity assessor. They can be used for systematic data collection in epidemiological studies on risk factors for the introduction and establishment of S. Dublin in dairy farms. Preliminary interrater reliability testing indicated moderate reliability between assessors with varying biosecurity skills.

Phylogenetic analysis of the partial sequences of the env and tax BLV genes reveals the presence of genotypes 1 and 3 in dairy herds of Antioquia, Colombia.

Bovine leukemia virus (BLV) is a retrovirus that primarily infects dairy cows. Although few studies have also used the tax gene, phylogenetic studies of BLV use mostly the env gene. The aim of this work was to establish the circulating genotypes of BLV in specialized dairy cattle from Antioquia, Colombia. Twenty blood samples from Holstein Friesian cows were collected, and their DNA was isolated. A PCR was performed for a partial region of the env and tax genes. A phylogenetic analysis was carried out using the maximum likelihood and Bayesian methods for both genes. Nineteen sequences were identified as genotype 1 by env and tax genes. Only one sequence was clustered with genotype 3 and had the highest proportion of different nucleotide sites compared to other strains. Four amino acid substitutions in the 134 amino acid residue fragment of the Env protein were identified in the Colombian sequences, and three new amino acid substitutions were reported in the 296 amino acid residue fragment of the Tax protein. R43K (Z finger), A185T (Activation domain), and L105F changes were identified in the genotype 3 sample. This genotype has been reported in the United States, Japan, Korea, and Mexico, but so far, not in Colombia. The country has a high rate of imported live animals, semen, and embryos, especially from the United States. Although it is necessary to evaluate samples from other regions of the country, the current results indicate the presence of two BLV genotypes in specialized dairy herds.

Milk Quality and Safety in a One Health Perspective: Results of a Prevalence Study on Dairy Herds in Lombardy (Italy).

Mastitis is one of the major diseases of dairy cows that affects milk quality and quantity and increases the potential risk for the presence of antimicrobial residues (AR) in milk, which could lead to the development of antimicrobial resistance (AMR) among human pathogens. Even if the presence of AR in milk and milk products is low in many countries, the threat is not negligible and cannot be ignored. These problems may be investigated by applying a One Health approach, and this prevalence study aimed to estimate the risks for human health related to milk production applied to dairy herds in Lombardy. Three hundred thirty-one bulk tank milk samples were randomly collected and analyzed by CombiFoss 7 and MilkoScan 7 (milk quality, bacteria, and somatic cell count), an HPLC system coupled to a Q-Exactive Orbitrap (AR), and qPCR (contagious pathogens). The data were analyzed by a generalized linear model. The results showed a relatively high prevalence of contagious pathogens (S. aureus 28.1%; Str. agalactiae 7.3%; M. bovis 3%), which primarily affect milk nutritional components decreasing mainly milk fat content (range 1%-2.5%), but did not show them to be associated to an increase of the risk of antimicrobial residues. These latter ones were recovered only in 7/331 samples at concentrations far below official MLRs. The results support currently active surveillance programs' efficacy in reducing AR risks, which may be further improved by prioritizing them based on geographical area characteristics.

Bovine Viral Diarrhea Virus within and herd prevalence on pasture-based dairy systems, in southern Chile dairy farms.

Bovine Viral Diarrhea (BVD) is a ubiquitous endemic disease in most bovine populations that causes a negative economic impact on cattle production systems. However, true herd and individual prevalence in Chile have not been estimated based on statistical and epidemiological considerations and uncertainty regarding the infection's extension at animal and herd levels. In addition, the risk factors that can influence how the infection has spread among the cattle premises have not been assessed yet. Therefore, the study aimed to estimate true herd and animal prevalence of active BVDV infection in pasture-based dairy herds and to evaluate risk factors potentially associated with the status of herds and the within-herd prevalence, using a Bayesian approach. A cross-sectional study was performed over a random stratified (proportional to herd size) sample of one-hundred and fifty dairy herds selected in Chile's two leading dairy regions (Region de Los Ríos and Region de Los Lagos). We obtained 12.311 blood samples from lactating cows, but 4.998 randomly selected samples were processed due to budget constraints. For estimating BVDV Herd Prevalence (HP), a herd was considered infected if at least one positive animal to Ag-ELISA was found. In addition, a survey was completed on each farm, aiming to collect information to assess the influence of some variables over the state of the herds; both estimations were obtained using a Bayesian approach. True herd prevalence and true individual prevalence of BVDV active infection were estimated at 77 % and 3.5 % respectively, no significant differences were found between characteristics like herd size, location, vaccination, etc. Open herds and herds that mix herd categories are more likely to have higher BVDV prevalence.

Dairy calf and replacement heifer mortality on a single intensively managed dairy farm in Jordan: A 3-year-long study (2016-2018).

Background: Pre-weaning dairy calf and replacement heifer mortality represents significant economic loss, limits genetic improvement and growth of the herd, and indicates poor management and animal welfare status on the farm. Aim: Currently, the rates and causes of the dairy calf and replacement heifer mortality in Jordan are not known. Therefore, the objective of this study was to determine the incidence rates and causes of mortality of pre-weaning calves and replacement heifers in Jordan. In addition, the age and seasonal distribution of mortality are determined in the study. Methods: Data extracted from the farm management record software over 3 years (January 2016-December 2018) were used in this study. Calf-specific data included the day and month of birth and sex. Health-related data included age at death, necropsy findings, laboratory findings if available, and the presumptive diagnosis. Descriptive analysis was performed to determine the 3-year overall mortality rate as well as the yearly mortality rate in pre-weaning calves and replacement heifers using excel spreadsheets of Microsoft Word 10. Results: Only female calves (n = 724) born alive during the study period were used in the analysis. The overall calf mortality rate was 8.9% with a yearly rate ranging between 5.9% and 12%. The majority of deaths occurred in calves less than 50 days of age with an average age of 17 days. There was a seasonal pattern for calf mortality with the majority of deaths occurring during the colder months of the year (December, January, February, and March). The highest number of pre-weaning calves died because of enterotoxemia (39%) and pneumonia (30%). Other causes of calf mortality were abomasal ulcer (8%), enteritis (6%), septicemic salmonellosis (5%), meningitis (4%), rumen drinkers (3%), aspiration pneumonia (3%), septic arthritis (1%), and omphalitis (1%). The overall 3-year heifer mortality rate was 4%. The average age of dead heifers was 8 months (range 3-23 months). The highest number of heifers died because of neurologic disease (37%) and enterotoxemia (33%). Other causes of heifer mortality were abomasal ulcer (11%), enteric salmonellosis (7%), chronic rumen tympany (7%), and chronic pneumonia (4%). Conclusion: Data presented in this study are essential to construct and implement effective preventative health programs and improve farm management practices to reduce calf and heifer losses.

Modeling Paratuberculosis Transmission in a Small Dairy Herd Typical of Slovenia Suggests That Different Models Should Be Used to Study Disease Spread in Herds of Different Sizes.

This study aimed to investigate the possible dynamics of paratuberculosis or Johne's disease in a typical Slovenian dairy herd of about 17 cows. Paratuberculosis is a worldwide endemic disease of cattle caused by Mycobacterium avium subsp. paratuberculosis (MAP) and is associated with significant economic losses. We developed a stochastic compartmental model with two pathways of disease progression, infections of adult cows and infections of young animals through horizontal and vertical transmission, and transmission through animal movements. The average proportions of subclinically and clinically infected cows were 4% and 0.47%, respectively. The prevalence within the herd, which included latently infected animals, averaged 7.13% and ranged from 0% to 70.59%. Under the given circumstances, the results showed a relatively high rate of spontaneous elimination (0.22 per herd per year) of the disease and a high rate of reinfection (0.18 per herd per year) facilitated by active animal trade. To our knowledge, this stochastic compartmental model is the first to be developed specifically to represent a small dairy herd and could apply to other countries with a similar structure of dairy farms. The results suggest that different models should be used to study MAP spread in herds of various sizes.

Brucellosis in dairy herds: Farm characteristics and practices in relation to likely adoption of three potential private-public partnership (PPP) vaccination control strategies in West and Central Africa.

Brucellosis is regarded as one of the highest burden zoonotic diseases to persist in many regions globally. While sustained vaccination against B. abortus in an endemic setting can markedly reduce the prevalence of large ruminant and human brucellosis and benefit local livelihoods, the implementation of effective and sustainable control programmes has often failed in the worst affected areas. In a cross-sectional study of 728 peri-urban dairy farmers in nine areas of six West and Central African countries, levels of commercialization and farm characteristics were examined alongside B. abortus seroprevalence estimates to hypothesize the most appropriate model for brucellosis vaccination delivery in each country. Demographic and economic data were collated and used to describe the farming systems currently in place. Furthermore, these data were utilized in a likelihood assessment to generate a quantitative score to hypothesize which of three private-public partnership (PPP) vaccine delivery models, that is 1) transformative, 2) transactional or 3) collaborative, would be most appropriate in each setting. The study sites had substantial differences in their levels of dairy commercialization and the farming practices employed; the heterogeneity across the study sites was evident in the conclusions of which models would be appropriate for vaccination delivery. While Lomé (Togo) had a strong indication for a transformative PPP model, Burkina Faso had strong indication for the collaborative PPP model. Of the remaining study sites, the scores were less dominant for any one model with Cameroon and Ivory Coast sites only just scoring highest on the transformative model and Senegal and Mali sites only just scoring highest on the collaborative model. Interestingly, none of the countries included in the study scored highest on the transactional model which currently is the most commonplace delivery model in the majority of sub-Saharan African countries.

Bayesian estimation of prevalence of Johne's disease in dairy herds in Southern Italy.

Johne's disease (JD) is a chronic granulomatous disease caused by Mycobacterium avium subsp. paratuberculosis (MAP) causing important losses on dairy farms. In Italy, voluntary programs to control MAP infection in dairy cattle are implemented in the Northern part of the country, where several studies have been carried out. Conversely, the disease status has not been fully investigated in the Southern regions. The aims of this study were to (i) determine the herd-level true prevalence (HTP) and (ii) the conditional within herd animal-level prevalence (CWHP) of JD in selected dairy cattle herds in Southern Italy. Serum samples were taken from 27 farms and analysed using a commercial ELISA test. A Bayesian model was fitted to the data. The estimated posterior mean of HPT was 0.46 (89 % CI 0.25-0.67), while the mean CWHP was 0.03 (89 % CI: 0.012-0.045). The results presented in this study call for designing and implementing an effective JD control program at national level.

Pathogenic Leptospira spp. Seroprevalence and Herd-Level Risk Factors Associated with Chilean Dairy Cattle.

Leptospirosis is a ubiquitous distributed zoonotic infectious disease present in wild and domestic animals. This study aimed to estimate within-herd and herd-level seroprevalence against pathogenic Leptospira spp. in dairy cows from southern Chile and identify risk factors associated with the herd-level status. We used a multi-stage strategy combined with a stratified sample strategy for randomly sampling 147 herds and 4876 lactating cows. We considered as infected a herd with at least one positive reactor to MAT. In addition, an epidemiological survey was applied to the herd's owners and a logistic regression (LR) model was constructed to analyze it. The overall within-herd prevalence was 5.9% (95% CI 4.9-6.8), the overall herd-level prevalence was 42.2% (95% CI 9.2-47.9), and there was variation in both between different herd sizes. L. borgpetersenii serovars Hardjo and Tarassovi and L. interrogans serovar Pomona were the more frequent serovars in non-vaccinated herds. A factor that decreases the risk of a farm being infected was Leptospira vaccine usage (OR = 0.04; 95% CI = 0.02-0.11), and variables that increase risk were using bulls for mating (OR = 3.43; 95% CI = 1.1-10.1) and continuous calving distribution (OR = 3.4; 95% CI = 1.3-8.8). The study's results will contribute to unravelling the infection burden in the main dairy area of the country and designing control strategies.

Longitudinal Prevalence of Antibodies to Endemic Pathogens in Bulk Tank Milk Samples From Dairy Herds Engaged or Not in Contract Heifer Rearing.

Since the abolition of EU milk production quotas in 2015, Europe's dairy industries have undergone a period of rapid expansion with possible resultant increased inter-herd transmission of endemic pathogens. The aims of this study were (1) to establish the post-2015 prevalence of antibodies to selected endemic infectious diseases and (2) to determine if prevalences differed between herds where heifers were reared at home and those where heifers were sent out for contract-rearing. Three bulk tank milk (BTM) samples were collected annually between May and August of 2018-20 inclusively from 120 Irish dairy herds. Additionally, herd vaccination status was collected by questionnaire. Milk samples were tested using commercially available ELISAs for eight pathogens: bovine viral diarrhea virus (BVDV), bovine herpesvirus 1 (BoHv-1), bovine respiratory syncytial virus (BRSV), Mycoplasma bovis, Mycobacterium avium subspecies paratuberculosis (MAP), Salmonella Dublin (S. Dublin), Leptospira Hardjo (L. Hardjo), and Neospora caninum (N. caninum). The true prevalence of each pathogen was calculated using a Rogan-Gladen estimator. The true prevalences (95% CI) of BTM antibodies in unvaccinated herds across the 3 years were as follows (i) BVDV: 57, 86, and 73% (95% CI: 40.7-65.9, 74-94, and 58-85) (n = 56, 56, and 48), (ii) BoHv-1: 47, 49, and 19% (95% CI: 26.3-69.7, 25-75, and 1-56) (n = 21, 20, and 11), (iii) L. Hardjo: 34, 59, and 73% (95% CI: 12.5-63, 33-82, and 33-99) (n = 15, 21, and 10), (iv) S. Dublin 32, 57, and 11% (95% CI: 12.21-68.1, 30.2-90.1, and 0) (n = 19, 22, and 13), (v) BRSV: 100% (95% CI: 99.5-100, 100, and 100) (n = 120, 109, and 91), (vi) MAP: 0% (95% CI: 0, 0, and 0) (n = 120, 109, and 91) (vii) N. caninum 0% (95% CI: 0, 0, and 0) (n = 120, 109, and 91) and (viii) M. bovis (ELISA) 53, 0.42, and 30% (95% CI: 3.95-6.84, 0, and 21-41) (n = 120, 109, and 91). M. bovis was detected by PCR in 0, 1, and 0% of herds in 2018, 2019, and 2020, respectively. This study showed that expanding Irish dairy herds are endemically infected with several of the studied pathogens. No differences in herd prevalence of infectious agents were observed between farms with different heifer rearing strategies (contract-rearing vs. traditional rearing).

Machine learning algorithms, bull genetic information, and imbalanced datasets used in abortion incidence prediction models for Iranian Holstein dairy cattle.

The ability to predict abortion incidence, especially in regions with high abortion rates (e.g., Iran), helps improve reproductive performance and, thereby, dairy farm profitability. The objective of this study was to predict pregnancy loss in Iranian dairy herds. For this purpose, the cow history records and bull genetic information available at 6 large commercial dairy farms with cows calved between 2005 and 2014 were extracted from an on-farm record-keeping software. Using WEKA, 12 commonly used machine learning (ML) algorithms were applied to the dataset. The algorithms belonged to 5 classifier groups which were Bayes, meta, functions, rules, and trees. The original dataset including herd-cow factors was randomly divided into 2 subsets: a training dataset and a test one (at a ratio of 60:40). The original dataset was combined with the bull genetic information to create a full dataset. The average abortion rate was 15.4 %, which represented an imbalanced dataset. Therefore, 2 down- and up-sampling techniques were additionally implemented on the original dataset (more specifically on the training one) to create 2 balanced datasets. This ultimately yielded 4 datasets; original, full, down-sampling, and up-sampling. Different algorithms and models were evaluated based on F-measure and area under the curve (AUC). Based on the results obtained, ML algorithms exhibited a high performance in predicting abortion when applied to the balanced dataset. However, their performance varied from 32.3 % (poor) to 69.2 % (medium upward) when applied to the imbalanced original dataset. In addition to the imbalance in the original dataset, the reason for these poor results were attributed to the high proportion of unknown risk factors underlying abortion incidence. Even when including the bull genetic information, it did not lead to any significant improvements in the prediction model. From among the datasets used, the Bayes algorithms outperformed the others in predicting pregnancy losses while rules had the worst performance. Furthermore, while the Bayes algorithms were not affected by the type of dataset (balanced or imbalanced), substantial increases in F-measure and AUC were observed for rules, trees, and functions with balanced datasets. Overall, the balanced models outperformed the others, with the down-sampling method exhibiting the highest performance. Despite the fact that the prediction models used in this study did not perform as expected, it was shown that they can be beneficially used to predict and reduce pregnancy losses, despite their moderate accuracy, especially when used for herds with high abortion rates and low reproductive performances.

Brucellosis in dairy herds: A public health concern in the milk supply chains of West and Central Africa.

Ten herd-level cross-sectional studies were conducted in peri-urban dairy production areas of seven West and Central African countries (Burkina Faso, Burundi, Cameroon, Mali, Niger, Senegal and Togo). The objectives were to estimate herd level Brucella spp. seroprevalence and identify risk factors for seropositivity. In each of the ten study areas, herds (between 52 and 142 per area, total = 965) were selected probabilistically and a structured questionnaire was administered to gather information on their structure and management. A bulk milk sample from each herd was tested by indirect ELISA for Brucella spp. For each area, herd seroprevalence estimates were obtained after adjusting for the assumed performance of the diagnostic test. Herd level risk factors for Brucella spp. seropositivity were identified by means of stratified logistic regression, with each peri-urban zone as a stratum. Area-specific models were also explored. Estimated herd seroprevalences were: Lomé (Togo) 62.0% (95% CI:55.0-69.0), Bamako (Mali) 32.5% (95% CI:28.0-37.0), Bujumbura (Burundi) 14.7% (95%CI:9.4-20.8), Bamenda (Cameroon) 12.6% (95% CI:7.6-21.9), Ouagadougou (Burkina Faso) 3.0% (95% CI:1.0-9.1), Ngaoundere (Cameroon) 2.3% (95% CI:1.0-7.0), Thies (Senegal) 1.3% (95% CI:0.1, 5.3), Niamey (Niger) 1.2% (95% CI:0.08-5.3), Dakar (Senegal) 0.2% (95% CI:0.01-1.7) and Niakhar (Senegal) <0.04%. Logistic regression modelling revealed transhumant herds to be at lower risk of infection (adjusted OR: 0.25, 95% CI: 0.13 - 0.5) and in one of the areas (Bamenda), regular purchase of new animals was found to be strongly associated with Brucella spp. seropositivity (adjusted OR = 5.3, 95% CI: 1.4-25.9). Our findings confirm that Brucella spp. circulates among dairy cattle supplying milk to urban consumers in West and Central Africa, posing a serious public health concern. Control programs are urgently needed in areas such as Lomé or Bamako, where more than 30% of the herds show evidence of infection.