Severe Mastitis Research Articles

Mediation effect of peripheral blood inflammatory factors in the association between severity of nonlactating mastitis and glycemic abnormalities

Background: The association between severity of non-lactating mastitis and glycemic abnormalities was analyzed to investigate the mediating role of peripheral inflammatory factor levels in the association. Methods: A total of 337 cases were included in this study, including 195 cases in the control group and 142 cases in the case group. Multifactorial logistic regression was used to analyze the associations between the severity of NLM and glycemic abnormality and peripheral inflammatory factors, and a mediation model was used to explore the mediating roles of the levels of hs-CRP, WBC, and IL-6 in the associations between the two. Results: The inflammatory factors IL-6, WBC, and hs-CRP had mediating effects, with effect values of 0.009 (0.003-0.038), 0.006(0.001-0.047), and 0.007(0.001-0.051), and mediating effect percentages of 2.38%, 2.12%, and 2.24%, respectively. Conclusion: NLM severity and glycemic abnormalities were positively correlated with peripheral inflammatory factors, and peripheral inflammatory factors played a partial mediating role in the association.

Livestock-associated methicillin-resistant Staphylococcus aureus ST398 causing severe mastitis in a meat sheep herd in the United States.

Livestock-associated methicillin-resistant Staphylococcus aureus ST398 causing severe mastitis in a meat sheep herd in the United States.

Comparative prevalence assessment of subclinical mastitis in two crossbred dairy cow herds using the California mastitis test

The study was conducted on two herds of Jersey crossbred dairy cows. Samples were taken from two dairy farms to conduct the California Mastitis Test (CMT) during milking. A total of 115 animals were sampled, with 65 animals from Farm 1 and 60 animals from Farm 2. Milk samples were collected from all four quarters of each cow. The study analyzed a total of 460 quarters from the collected milk samples. Among these quarters, 132 quarters (28.69%) were found to be infected. The prevalence of mastitis was 45% in Herd 1 and 25% in Herd 2. The study found that only one quarter of the udder was more affected in both herds. The CMT score (likely a measure of mastitis severity) increased during late lactation. Infected cows had an average milk yield/day of 3.6 liters. Inflammatory (within or under the mammary gland) infections were more common in the first and second parity cows (cows that had given birth to one or two calves, respectively). This could be ascribed to the fact that dairy cows in their starting lactations are more vulnerable to the environmental pathogens because they might not have built up their immunity yet. Overall, this study provides insights into the prevalence, severity, and patterns of mastitis in Jersey crossbred dairy cows located at two different farms. The study highlights factors such as the stage of lactation, parity, and herd differences that can influence the occurrence and severity of mastitis in these animals.

Hot topic: Influenza A H5N1 virus exhibits a broad host range, including dairy cows

The widespread circulation of highly pathogenic avian influenza (HPAI) H5N1 clade 2.3.4.4b in wild birds in North America since late 2021 has resulted in multiple outbreaks in commercial and backyard poultry leading to major economic losses. Since the emergence of the virus in North America, multiple reassortment events have led to the emergence of many new variant genotypes that have been isolated from wild birds, with several viruses spilling over into poultry and other terrestrial and aquatic mammalian hosts. Notably, the most recent emerging HPAI H5N1 reassortant genotype B3.13 spilled over into dairy cattle (Bos taurus), resulting in unprecedented efficient transmission of the virus in this species, the first case of sustained transmission in a mammalian species. The transmission pathways involved in the spread of the virus from its first detection in Texas to several other states are complex. However, movement of subclinically infected cattle likely played a major role in virus spread. Infection in dairy cattle is characterized by the virus's tropism for milk-secreting cells in the mammary gland, leading to high viral load and shedding in milk. Replication of the virus in milk-secreting cells results in destruction of infected cells leading to severe viral mastitis, which is characterized by marked changes in milk quality (altered consistency and color) and pronounced decline in milk production by clinically affected animals. Here, we provide an overview of the HPAI H5N1 panzootic virus and discuss its host range and the current knowledge of its pathogenesis in the new bovine host.

Isolate and Molecular Identification of Bundle Forming Pilus Gene for Escherichia coli Caused Caw Mastitis

Mastitis is one of the disease infected Caws and effect of their milk product lead economic loss. The aim of this study isolated and molecular identification Bundle Forming Pilus Gene for Escherichia coli caused Caw mastitis. Samples were collected from Caws infected with Mastitis at different farm in Iraq, then applied for cultivation on the suitable media for isolated of E. coli. The E.coli isolates was confirmed by VITEK II automated microbial identification system method and identification by PCR method for expression of bundle forming pilus gene. The result was shown that (9 from 100) from mastitis cases give E. coli positive. All E.coli isolates were confirmed by VITEK method. All E.coli isolates were expressed of bundle forming pilus gene. Conclusion: E.coli caused severe mastitis in Caw and the severity of infection come from express of bundle forming pilus gene that increases the virulence of E.coli be more resistance to antibiotics and unsuitable conditions that may be lead to many serious diseases if dietary contaminated with mastitis E.coli .

Effects of Clinical Mastitis on Reproductive Performances in Dairy Cows

The study was undertaken to study the productive and reproductive performances in clinical mastitis (CM) affected and apparently, healthy dairy crossbred cows and to analyze the effects of mastitis considering age, lactation, and severity of mastitis on reproductive performances in crossbred cows. A survey using a questionnaire was done to record different parameters of the cows during the period November 2021 to March 2022. A total of 58 lactating cows included in this study were divided into two groups named mastitis (n=24) and controlled (n=34). Cows of the mastitis groups were divided into subgroups depending on the age, lactation number and severity of mastitis. Prolactin (PRL), progesterone (P4) and estrogen (E2) levels of cows at the time of AI were analyzed. The results showed that cows of the mastitis group had substantially (P<0.01) higher values for Days to first heat detection after parturition (96.16±6.20), Days to first insemination after parturition (105.00±6.64), Days open (140.58±7.40), and number of services per conception (2.33±0.11). The results also indicated that the greatest values were seen in the cows of Sub-group age >8 for Milking Yield (16.21±2.39 Lt), Days to first heat detection after parturition (109.29±13.57), Days to first insemination following parturition (122.14±15.87), and Days open (165.79±16.70), and in cows of Sub-group 7-8 had for the Days of incidence of mastitis following parturition (51.57±12.73). Considering the number of lactations, we observed the highest values of Milking Yield (16.69±2.20 Lt), Days to first heat detection after parturition (108.75±11.58), Days to first insemination following parturition (120.00±13.96), and Days open (160.63±15.20) in cows of Sub-group lactation number >3 and the highest Days of occurrence of mastitis after parturition in cows of Sub-group lactation number 3. Based on the degree of clinical mastitis, it was found that cows of the severe mastitis sub-group had the greatest Milking Yield (24.80±5.40 Liter) at a significant level (P<0.05). This result indicates an association of severe CM with a high yield of milk. Whereas, there was no significant (P>0.05) variation observed in different parameters in terms of reproductive performances in all sub-groups. In addition, significantly (P<0.01) higher prolactin levels (16.10 ±1.17 ng/ml) and low estrogen levels (13.86±0.57 pg/ml) were present in CM-affected cows. This study could help veterinarians in taking strategies to minimize and control the negative effect of clinical mastitis on the reproduction of dairy cows. J. of Sci. and Tech. Res. 5(1): 01-07, 2023

Understanding the dynamics of mastitis in milk yield: decoding onset and recovery patterns in response to mastitis occurrence

No recent study attempted to model daily milk losses before and after mastitis onset and the moment when it begins. Thus, we aimed to describe the impact of mastitis on milk production based on mastitis level and moment of occurrence. We used data from 11 dairy farms, and the data set consisted of 885,759 daily individual milk test records from 3,508 cows in different lactations, with an average milk yield from January 2017 to December 2022. We modeled the impact of mastitis severity [i.e., 1 (mild) and 2 (severe)] based on the drop and recovery of milk yield following 3 steps. First, we removed milk recorded on the day of diagnosis of mastitis from the data set and fitted a Wood's Curve for each cow and parity. Second, we returned the mastitis data to the data set and estimated the residual milk loss due to mastitis from 15 d before to 30 d after the mastitis event. Third, we used generalized additive mixed effect models to estimate the residual milk loss, including farm as a random effect. In addition to the random effect of the farm, we also included the predicted value of mastitis, the day effect before and after mastitis incidence, and the interaction between the predicted value of mastitis and days. On average, mastitis level 2 resulted in a more severe milk yield drop in all represented stages of lactation (80, 170, and 260 d in milk), suggesting a higher loss close to the lactation peak, approximately 130 kg more than mastitis level 1. Moreover, the occurrence of mastitis case level 1 during early phase of lactation (DIM 80) can cause an average milk loss of 158 L and a ML 2, an average loss of 288 L. The estimations suggest that milk drop occurs 14 to 4 d before mastitis onset and can last until 15 to 25 d from the diagnosis, which would be the necessary time for a cow to reestablish their predicted milk yield. Therefore, our study brings new perspectives to investigate milk yield drop and recovery due to mastitis infections and how much mastitis can deplete and impair milk production.

Trueperella Pyogenes-Strain Diversity and Occurrence in Dairy Herds.

Trueperella (T.) pyogenes is a mastitis-causing pathogen formerly known to cause severe clinical mastitis (CM), especially during the summer, leading to milk losses and low recovery rates. Unfortunately, its transmission behavior within herds is unclear. The diversity and occurrence of T. pyogenes were monitored to gain an initial insight into the infection transmission behavior of T. pyogenes in dairy herds and to lay a foundation for following targeted investigations. CM milk samples were collected from German herds, and one Swedish farm was sampled for isolates from subclinical mastitis. All in all, 151 T. pyogenes isolates from 16 herds were isolated, identified by MALDI TOF analysis and typed with RAPD PCR. Of these, 17 isolates originated from subclinical mastitis cases. We found that T. pyogenes mastitis occurred year-round, and clinical mastitis cases were caused by multiple strains (31 affected animals/28 strains). Instances of multiple cows being infected with the same T. pyogenes strain were rare and typically only involved a small number of animals at a time. However, if several quarters of a cow were affected, it was likely the same strain. Unlike clinical infections, subclinical T. pyogenes infections, in one investigated farm, harbored a dominant strain. Additionally, we found that T. pyogenes infections tended to persist and stay within a herd for a minimum of 7 months in the same or different cows.

Lycopene promoted M2 macrophage polarization via inhibition of NOTCH1-PI3K-mTOR-NF-κB-JMJD3-IRF4 pathway in response to Escherichia coli infection in J744A.1 cells.

Escherichia coli (E. coli) can induce severe clinical bovine mastitis, which is to blame for large losses experienced by dairy farms. Macrophage polarization into various states is in response to pathogen infections. Lycopene, a naturally occurring hydrocarbon carotenoid, relieved inflammation by controlling M1/M2 status of macrophages. Thus, we wanted to explore the effect of lycopene on polarization states of macrophages in E. coli-induced mastitis. Macrophages were cultivated with lycopene for 24, before E. coli inoculation for 6h. Lycopene (0.5μmol/L) significantly enhanced cell viabilities and significantly reduced lactic dehydrogenase (LDH) levels in macrophages, whereas 2 and 3μmol/L lycopene significantly enhanced LDH activities. Lycopene treatment significantly reduced the increase in LDH release, iNOS, CD86, TNF-α, IL-1β and phosphatase and tensin homolog (PTEN) expressions in E. coli group. 0.5μmol/L lycopene significantly increased E. coli-induced downregulation of CD206, arginase I (ARG1), indoleamine 2,3-dioxygenase (IDO), chitinase 3-like 3 (YM1), PI3K, AKT, p-AKT, mammalian target of rapamycin (mTOR), p-mTOR, jumonji domain-containing protein-3 (JMJD3) and interferon regulatory factor 4 (IRF4) levels. Moreover, Ginkgolic acid C17:1 (a specific PTEN inhibitor), 740YPDGFR (a specific PI3K activator), SC79 (a specific AKT activator) or CHPG sodium salt (a specific NF-κB activator) significantly decreased CD206, AGR1, IDO and YM1 expressions in lycopene and E. coli-treated macrophages. Therefore, lycopene increased M2 macrophages via inhibiting NOTCH1-PI3K-mTOR-NF-κB-JMJD3-IRF4 pathway in response to E. coli infection in macrophages. These results contribute to revealing the pathogenesis of E. coli-caused bovine mastitis, providing the new angle of the prevention and management of mastitis.

Total mastectomy in severe necrotic mastitis in a pet goat complicated by a post‐operative generalised emphysema

AbstractA total mastectomy was the treatment of choice in a 10‐year‐old pet doe Pika with a history of severe necrotic mastitis secondary to a precocious udder. Following an elliptical skin incision, the mammary tissue was bluntly excised. Because of a large surgical defect, severe skin tension was needed to close the wound completely. A passive drain was placed in the surgical site to remove excess fluid, and the animal received antibiotic and anti‐inflammatory treatment. On the fifth day after the surgery, the drain was removed and palpation revealed an extensive subcutaneous emphysema at the surgical site as well as the back and neck of the animal. The antibiotic treatment was prolonged, and the animal kept for observation. After 3 weeks, the wound had healed completely, and the doe was discharged.

Bacillus velezensis iturins inhibit the hemolytic activity of Staphylococcus aureus

Bovine mastitis caused by S. aureus has a major economic impact on the dairy sector. With the crucial need for new therapies, anti-virulence strategies have gained attention as alternatives to antibiotics. Here we aimed to identify novel compounds that inhibit the production/activity of hemolysins, a virulence factor of S. aureus associated with mastitis severity. We screened Bacillus strains obtained from diverse sources for compounds showing anti-hemolytic activity. Our results demonstrate that lipopeptides produced by Bacillus spp. completely prevented the hemolytic activity of S. aureus at certain concentrations. Following purification, both iturins, fengycins, and surfactins were able to reduce hemolysis caused by S. aureus, with iturins showing the highest anti-hemolytic activity (up to 76% reduction). The lipopeptides showed an effect at the post-translational level. Molecular docking simulations demonstrated that these compounds can bind to hemolysin, possibly interfering with enzyme action. Lastly, molecular dynamics analysis indicated general stability of important residues for hemolysin activity as well as the presence of hydrogen bonds between iturins and these residues, with longevous interactions. Our data reveals, for the first time, an anti-hemolytic activity of lipopeptides and highlights the potential application of iturins as an anti-virulence therapy to control bovine mastitis caused by S. aureus.

Biomarker and proteome analysis of milk from dairy cows with clinical mastitis: Determining the effect of different bacterial pathogens on the response to infection

Antimicrobial usage (AMU) could be reduced by differentiating the causative bacteria in cases of clinical mastitis (CM) as either Gram-positive or Gram-negative bacteria or identifying whether the case is culture-negative (no growth, NG) mastitis. Immunoassays for biomarker analysis and a Tandem Mass Tag (TMT) proteomic investigation were employed to identify differences between samples of milk from cows with CM caused by different bacteria. A total of 94 milk samples were collected from cows diagnosed with CM across seven farms in Scotland, categorized by severity as mild (score 1), moderate (score 2), or severe (score 3). Bovine haptoglobin (Hp), milk amyloid A (MAA), C-reactive protein (CRP), lactoferrin (LF), α-lactalbumin (LA) and cathelicidin (CATHL) were significantly higher in milk from cows with CM, regardless of culture results, than in milk from healthy cows (all P-values <0.001). Milk cathelicidin (CATHL) was evaluated using a novel ELISA technique that utilises an antibody to a peptide sequence of SSEANLYRLLELD (aa49–61) common to CATHL 1–7 isoforms. A classification tree was fitted on the six biomarkers to predict Gram-positive bacteria within mastitis severity scores 1 or 2, revealing that compared to the rest of the samples, Gram-positive samples were associated with CRP < 9.5 μg/ml and LF ≥ 325 μg/ml and MAA < 16 μg/ml. Sensitivity of the tree model was 64%, the specificity was 91%, and the overall misclassification rate was 18%. The area under the ROC curve for this tree model was 0.836 (95% bootstrap confidence interval: 0.742; 0.917). TMT proteomic analysis revealed little difference between the groups in protein abundance when the three groups (Gram-positive, Gram-negative and no growth) were compared, however when each group was compared against the entirety of the remaining samples, 28 differentially abundant protein were identified including β-lactoglobulin and ribonuclease. Whilst further research is required to draw together and refine a suitable biomarker panel and diagnostic algorithm for differentiating Gram- positive/negative and NG CM, these results have highlighted a potential panel and diagnostic decision tree. Host-derived milk biomarkers offer significant potential to refine and reduce AMU and circumvent the many challenges associated with microbiological culture, both within the lab and on the farm, while providing the added benefit of reducing turnaround time from 14 to 16 h of microbiological culture to just 15 min with a lateral flow device (LFD).

Role of mastitis in on-farm deaths of Finnish dairy cows

According to our recent necropsy-based study, mastitis is the most common underlying diagnosis of on-farm deaths in Finnish dairy cows. However, it remained unanswered to what extent mastitis has contributed to death of all necropsied cows. In the present study, based on histopathology we detected one third of the necropsied dairy cows having active inflammatory udder lesions (n = 110). The role of mastitis varied and was interpreted by causes of death (underlying, intermediate, immediate, other significant). Mastitis was most commonly either the underlying (28%) or both immediate and underlying cause of death (48%), and only seldom the immediate (4%) or intermediate (4%) cause of death. Mastitis occurred either as the only cause leading to death (mastitis only, MO, 39%), or with many other contributing diseases (multiple diseases, MD, 61%) which were interacting with mastitis and together leading to death. Between these groups (MO vs. MD), time of mastitis occurrence during lactation, producer-reported duration of illness, clinical signs, and medication differed, as well the histopathological severity of mastitis. The cases, where mastitis was the only initial insult, occurred evenly throughout the entire lactation, but the cases with many interacting diseases clustered in early lactation. In multiple diseases -cases mastitis occurred concurrently with metritis (31%), aspiration pneumonia (24%), acute trauma/dystocia (15%), or with other diseases, such as ketosis, hepatic lipidosis, rumenitis, and abomasal diseases. For a pathologist, the gross mastitis diagnosis was most challenging at the beginning of the lactation, especially if inflammation was mild to moderate, suggesting the value of histopathological examination being highest at that time. Also, producers reported mastitis signs less frequently if cow had many simultaneously occurring diseases. Therefore, even if clinical signs of other diseases are present, the udder should be considered a potential cause of illness, and it should be examined, especially in dry and transition period cows.

The Tale of Staphylococcus aureus Isolated from Mastitis Infections: The Effect of Antimicrobials and Bacterial Relatedness

Staphylococcus aureus is a common causative agent of mastitis in dairy cattle, posing a substantial threat to animal health and resulting in significant economic losses. Preventive measures are usually in place to control the spread of the organism between animals and around the dairy environment; however, mastitis outbreaks can still be recurrent. During this investigation, a total of 30 S. aureus isolates were obtained from six deceased cows, all diagnosed with chronic mastitis during an outbreak in West Texas. The aim of this study was to evaluate the response of the S. aureus isolates causing severe mastitis infections to iodine treatments and their antibiotic susceptibility, planktonic growth, and biofilm formation. Udder skin was inoculated with S. aureus and subjected to various iodine concentrations of 0.25%, 0.38%, 0.50%, 0.75%, and 1.00%, with exposure times of 15 s, 10 s, and 60 s. The same concentrations were tested on S. aureus’s biofilm formation. The results of the antimicrobial susceptibility test indicate that the exposure time did not influence the treatment. Lower iodine concentrations were compared with 1.00%, as the standard treatment used by the dairy for teat disinfection, and statistical difference (p &lt; 0.001) was evident in the 0.00% iodine treatment compared to the other iodine concentrations. Moreover, a significant difference (p &lt; 0.001) emerged when comparing the 0.25% and 0.38% iodine concentrations with 1.00%. No difference (p &gt; 0.161) was detected between 0.50%, 0.75%, and 1.00%. These results suggest that, under the conditions investigated, iodine can be lowered to around 50% of the currently used dose without negatively impacting microbial control. On the other hand, S. aureus strains were susceptible to the tested antibiotics, demonstrating that antimicrobial resistance does not always play a role in the persistent mastitis infections caused by S. aureus. Further microbial phenotypic typing conducted on S. aureus strains indicated a possible common source of the infections, demonstrating the potential of there being resident S. aureus strains at this dairy farm.

Predicting an increased risk of severe clinical mastitis and economic loss using a threshold value of bovine leukemia virus proviral load.

To establish a threshold value of bovine leukemia virus (BLV) proviral load (PVL) to identify increased risk of severe clinical mastitis, and to examine the prognosis and economic loss of clinical mastitis based on the newly established PVL cut-off value. 97 lactating Holstein cows with clinical mastitis. Blood and milk samples were collected aseptically from each cow. Youden index was used for receiver-operating characteristic curve analysis with the severity rate of clinical mastitis as the dependent variable and PVL as an independent variable. PVL cut-off value was used as a criterion to compare the severity rate of clinical mastitis, percentage of cows with and without systemic treatments, number of treatments, cost of treatment, and prognosis. PVL cut-off value was 17.8 copies/10 ng DNA for the dependent variable MILD vs SEVERE. The severity rate of clinical mastitis, percentage of cows given systemic treatments, and technical fees for medical treatment were significantly higher in the group above the PVL cut-off value than in the group below the PVL cut-off value and the negative group. Number of treatments was significantly higher in the group above the cut-off value than in the group below the cut-off value. There was no significant difference in prognosis after mastitis among the 3 groups. These results suggested that PVL cut-off value of 17.8 copies/10 ng DNA was a useful threshold for increased economic losses in BLV-infected cows; it may also serve as a new standard value for the detection and culling of BLV-infected cows in Japan.

Treatment of clinically severe bovine mastitis - a scoping review.

Mastitis is a major health problem for bovines and can be categorized as non-severe or severe, based on clinical symptoms. A severe case of clinical mastitis is usually defined by the cow being affected systemically. It is important to consider how to handle severe cases because these cases can be fatal and cause high production losses. However, there are generally few detailed treatment guidelines. By conducting a scoping review on the topic, we aimed to synthesize the information that is available on treatment and outcomes, as reported from clinical trials and observational studies. This was facilitated by following the PRISMA-guidelines with a stepwise systematic screening of scientific literature on the subject, retrieved via Pubmed and Web of Science, using pre-defined selection criteria. The results yielded a total of 14 reports of treatment and outcomes in cases of naturally occurring severe clinical mastitis. Cross-trial comparison was difficult due to the different exclusion criteria and outcome definitions. Many studies focused on cases caused by gram-negative bacteria treated with intensive antibiotic protocols, often containing antibiotics that are categorized as critical for human health. Few focused on severe cases caused by gram-positive bacteria or on the relative use of non-antibiotic treatment. In general, only a small number of statistically significant differences were found in trials comparing different treatment protocols, with no obvious trends across trials. Our findings emphasize the need for more research into the treatment efficacy of antibiotic and non-antibiotic options for clinically severe mastitis. Furthermore, consideration of how trial conditions relate to the practical circumstances in a field setting could improve the applicability of reported results. This could help to provide practitioners with the information needed to make evidence-based treatment decisions in cases of clinically severe mastitis.

Welfare evaluation of dairy cows reared in the East of Algeria.

The aim of the study was to evaluate the welfare status of dairy cows raised in local conditions through health criteria. Important health problems have been identified as well as their effect on the milk yield. One hundred seven farms in eastern Algeria were visited. Data on health, productivity, and management practices were collected. Clinical examination of 1210 dairy cows was conducted to assess health scores. The relationship between herd health and milk yield was investigated using multiple linear regression models. The average milk yield per cow was 16.1 kg/day, and the average prevalence of thin cows (body condition score ≤ 2) was 35.1%. The cow dirtiness was a sign of poor facility hygiene, with 24.3% of cows had dirty udders, 44.5% had dirty flanks/upper legs, and 59.6% had dirty hind legs. The mean prevalence of clinical lameness (locomotion score ≥ 3) and severe lameness (locomotion score ≥ 4) were 24.7% and 8.7%, respectively. The prevalence of hocks, knees, and neck injuries (score > 1) with wound and/or swelling ranged from 0 to 46.2%, 0 to 71.4%, and 0 to 14.3%, respectively. The clinical examination showed a percentage of cows with mastitis of 15.4%, diarrhea of 6.9%, cough of 3.2%, nasal discharge of 7.5%, and ocular discharge of 1.8%. Thus, the milk yield had associated with severe lameness, mastitis, thinness, and dystocia. In conclusion, the welfare indicators in this study reflect the serious health problems in dairy farming which influence the expression of the cow genetic potential.

Etiology of severe mastitis in French dairy herds

Severe clinical mastitis is not so frequent in dairy cows, but it can have a significant economic impact due to its high mortality rate and adverse effects on milk production. Surveys about the cause of mastitis typically provide overall findings without connecting them to a specific medical condition. There are few studies on the specific etiology of severe mastitis. Only etiological results obtained during field studies are available in France, and the number of mastitic milk samples analyzed is always low. In recent years, veterinary clinics have improved their ability to identify bacteria causing bovine mastitis using a widely used method. This in-clinic milk culture made it possible to better understand the etiology of mastitis according to the symptoms observed. Regarding clinical mastitis, veterinarians treat severe cases differently than less severe ones. Based on data from nineteen veterinary clinics in France and over 2000 severe mastitis cases, the current study revealed that Enterobacteriaceae, particularly Escherichia coli, is the most common cause, isolated on average from 53.9% of milk samples. This information is highly reliable for practitioners to quickly and effectively treat the condition, because early and targeted treatment is crucial to avoid the complication of endotoxic shock.

Streptococcus ruminantium-associated sheep mastitis outbreak detected in Italy is distinct from bovine isolates

Streptococcus ruminantium is the causative agent of several bovine and ovine diseases, however reports are uncommon and application of whole genome sequencing to identify is rare. We report for the first time, a severe ovine mastitis outbreak caused by S. ruminantium in Italy, 2022. S. ruminantium was isolated from 12 adult lactating ewes with diffuse nodules in the mammary parenchyma and predominantly serous and clotted milk. All outbreak isolates, along with five additional historical Italian isolates (between 2011 and 2017), were genomically characterised and then analysed in the context of all publicly available S. ruminantium genomes. Antimicrobial susceptibility testing was performed to determine the MICs of 16 antibiotics. The results showed that all isolates were susceptible to all antimicrobials tested except kanamycin. Single Nucleotide Variant analysis confirmed this as a clonal outbreak across 10 sheep (≤ 15 SNVs), while the two others were colonised by more distantly related clones (≤ 53 pairwise SNVs), indicating the presence of multiple infecting lineages. The five historical S. ruminantium isolates were comprised of genetically-distant singletons (between 1259 and 5430 pairwise SNVs to 2022 outbreak isolates). Ovine isolates were found to be genetically distinct to bovine isolates, forming monophyletic groups. Bovine isolates were similarly made up of singleton clones in all but two isolates. Taken together, our genomic analysis using all globally available genomes is consistent with general opportunistic pathogenesis of S. ruminantium. We encourage future genomic surveillance efforts to facilitate outbreak detection, as well as improve our understanding of this poorly-understood, multi-host, zoonotic pathogen.

Intramammary calcitriol treatment of mastitis alters profile of milk somatic cells and indicators of redox activity in milk.

The objective of this experiment was to determine the effect of intramammary calcitriol treatment on indicators of inflammation during an intramammary bacterial infection. Lactating Holstein cows were challenged with intramammary Streptococcus uberis. At the onset of mild or moderate mastitis, cows were randomly assigned to receive 10µg of intramammary calcitriol (CAL, n = 7) or placebo control (CON; n = 6) after every milking for 5 days. Data were analyzed by ANOVA with mixed models using the MIXED procedure of SAS with significance declared at P ≤ 0.05. Milk somatic cells, mastitis severity scores, rectal temperatures, and milk bacterial counts did not differ between treatments. Calcitriol decreased the percentage of CD11b+CD14- cells in milk compared with CON (CON = 81 vs. CAL = 61 ± 5%). Antioxidant potential and concentrations of 15-F2t- isoprostanes in milk of infected quarters also were lower in CAL compared with CON. Transcripts for the 25-hydroxyvitamin D 24-hydroxylase and inducible nitric oxide synthase were greater in milk somatic cells of CAL compared with CON, but those for β-defensin 7, metallothionein 1A and 2A, thioredoxin and thioredoxin reductase did not differ between treatments. Although clinical signs of severity did not differ, CAL influenced the composition of milk somatic cells and redox activity in milk of infected quarters.