Metabolic signature of Mycobacterium avium subsp. paratuberculosis infected and infectious dairy cattle by integrating nuclear magnetic resonance analysis and blood indices.

The early diagnosis of Mycobacterium avium subsp. paratuberculosis (MAP) is one of the current challenges of farmers and veterinarians. This work aimed to investigate the changes in metabolic levels associated with natural MAP infection in infected and infectious dairy cattle. The study included sera from 23 infectious/seropositive, 10 infected but non-infectious/seronegative, and 26 negative Holstein Fresian cattle. The samples were selected from a collection of samples gathered during a prospective study. The samples were analyzed by quantitative nuclear magnetic resonance (NMR) spectroscopy and routine blood chemistry. The blood indices and the 1H NMR data were concatenated by low-level data fusion, resulting in a unique global fingerprint. Afterwards, the merged dataset was statistically analyzed by the least absolute shrinkage and selection operator (LASSO), which is a shrinkage and selection method for supervised learning. Finally, pathways analysis was performed to get more insights on the possible dysregulated metabolic pathways. The LASSO model achieved, in a 10 time repeated 5-fold cross-validation, an overall accuracy of 91.5% with high values of sensitivity and specificity in classifying correctly the negative, infected, and infectious animals. The pathway analysis revealed MAP-infected cattle have increased tyrosine metabolism and enhanced phenylalanine, tyrosine and tryptophan biosynthesis. The enhanced synthesis and degradation of ketone bodies was observed both in infected and infectious cattle. In conclusion, fusing data from multiple sources has proved to be useful in exploring the altered metabolic pathways in MAP infection and potentially diagnosing negative animals within paratuberculosis-infected herds.

A Longitudinal Case Study on Dissemination of ST398 Methicillin-Resistant Staphylococcus aureus Within a Dairy Cow Herd.

The study was conducted to describe the dynamics of ST398 methicillin-resistant Staphylococcus aureus (MRSA) on a dairy herd in northeastern Italy. MRSA was first identified in this herd of 120 cows in 2016, after which the herd was sampled once every 3 months for 1 year (April 2016-May 2017). Samples collected included nasal swabs and milk samples from cows and nasal swabs from farmworkers. In addition, pen fencing and teat milk liners were swabbed and air samples from cow pens and the milking parlor were collected. All samples were tested for MRSA using a selective medium; positive isolates were confirmed by mecA PCR. A representative set of MRSA isolates was genotyped using spa typing and multilocus sequence typing. Overall, 34 (mean 23%, range 16-30%) milking cows were found harboring MRSA in the mammary gland and only 6 recovered from infection or colonization. The mean incidence rate was 14% (range 8-20%), mean cure rate was 23% (range 13-43%), and estimated basic reproduction number (R0) was 1.08. The average of positive quarters found was 35.1% and most of the positive quarters (82.4%) developed subclinical mastitis. The mean duration of MRSA colonization in quarters during the study was 247 days, but quarters affected by subclinical mastitis harbored MRSA for a longer time than healthy ones (285 days vs. 131 days). After the second sampling, the farmer segregated MRSA-positive cows from the uninfected cows and milked them last. Despite segregation, 25 newly infected or colonized cows were detected. MRSA isolates from cows, environment, and two farmworkers belonged to the same sequence type (ST398) and spa type (t034). This study highlights the ability of ST398 MRSA to cause a persistent infection of the mammary gland and to survive in the farm environment.

Association between passive immunity and health status of dairy calves under 30 days of age.

Calves are highly susceptible to disease and mortality occurrence within the first month of life. Even if failed transfer of passive immunity (FTPI) is commonly recognized as a main factor affecting calf health and survival, conflicting results are reported in literature about the association between passive immunity (PI) and calf health, especially regarding enteric diseases. Therefore, a prospective cohort study was conducted on 78 calves of three Italian dairy farms during winters of years 2014-2016, with the specific aim of evaluating the association between PI and health status of calves within 30 days of age under field conditions. Blood samples were collected between 1 and 5 days of age from each calf included in the study, and disease and mortality occurrence was monitored throughout the first month of life. Additionally, fecal samples were collected from calves with scours before treatment. Blood serum samples were tested by an electrophoretic method for the assessment of immunoglobulin (Ig) concentration, whereas fecal samples were submitted to ELISA test for positivity to Escherichia coli K99, rotavirus, coronavirus, and Cryptosporidium spp. Only enteric diseases occurred in calves of this study. Calves that suffered from diarrhea or died within the first month of life had lower serum Ig concentrations than those that remained healthy or survived (P < .05). Even if not significantly (P = .127), lower serum Ig concentrations were observed in sick calves that had been treated with antibiotics compared to those that had not been treated. The odds of disease and mortality occurrence were 24 (95% CI = 3-231) and 11 (95% CI = 1-111) times higher, respectively, for calves with FTPI (serum Ig concentration <10.0 g/L) than for those with an adequate PI transfer (P <  .05). Calves with adequate PI transfer had also a 6-day delay in the age at first disease onset compared to those with FTPI (P < .01). Even if estimated on a small number of calves, those with FTPI had higher risks of enteric infections by rotavirus (odds ratio = 12; 95% CI = 1-137) and Cryptosporidium spp. (odds ratio = 9; 95% CI = 1-72) (P < .05). In this study, the PI level influenced the occurrence of enteric diseases and mortality in calves under one month of age, confirming the importance of a proper colostrum provision to calf health and, consequently, to the reduction of antimicrobial use in dairy farming. However, further investigations are needed, particularly focusing on the relationship between PI and specific enteropathogen infections in calves.