Prevalence of bovine subclinical mastitis and isolation of its major causes in Bishoftu Town, Ethiopia

Antibiograms, multidrug resistance, and milk-related parameters of bacteria isolated from milk of dairy cattle in Phatthalung, Thailand

Background and Aim

Milk, a nutritious food, is widely consumed in human diets; however, contamination by micro-organisms can negatively impact its quality and consumer health. Contamination by micro-organisms affects the quality of milk, which can affect the quality of the milk production chain. This study aimed to determine the changes in milk composition and antibiotic susceptibility related to bacteria isolated from dairy cow milk.

Materials and Methods

Raw milk samples were collected from 72 dairy cows. All milk samples were subjected to the California Mastitis Test (CMT) for CMT score determination. We also investigated milk composition, bacterial culture (BC), and antibiotic susceptibility.

Results

About 47.22% and 30.56% of dairy cattle were positive for CMT + BC and automatic somatic cell count (ASCC) + BC, respectively. Fecal appearance and animal age were found to be risk factors for ASCC + BC positivity in dairy cattle. Bacteria were found in approximately 76% of milk samples, with the most common isolated species being α-hemolytic Streptococcus spp., coagulase-negative Staphylococcus spp., and Escherichia coli. Of these, 70% are resistant to at least one antibiotic. Variation in the multidrug resistance pattern was high in Klebsiella spp.

Conclusions

Fecal appearance and animal age are risk factors for ASCC + BC positivity in dairy cattle. This study identified antibiotic and multidrug resistance patterns, which require comprehensive studies and effective surveillance systems. Remarkably, the use of antibiotic therapy in dairy cattle should be monitored.

Prevalence of subclinical mastitis, associated risk factors and antimicrobial susceptibility pattern of bacteria isolated from milk of dairy cattle in Kajiado Central sub-county, Kenya

BACKGROUND

Literature is scarce on the occurrence of bovine mastitis and antimicrobial resistance among dairy animals kept by pastoralists in the Kenya.

OBJECTIVES

A cross-sectional study was carried out to investigate the prevalence and risk factors of subclinical mastitis (SCM) and evaluate the antibiotic sensitivity of bacteria isolated from dairy cattle kept by farmers in Kajiado Central sub-county, Kenya.

METHODS

A total of 202 lactating cows from 40 farms were sampled. Milk from the cows was screened for SCM using the California mastitis test, and the bacteria present in the milk samples were determined using standard bacteriological methods. The sensitivity of the isolated coagulase-negative staphylococci (CNS) and Staphylococcus aureus against antibiotics was tested using the Kirby-Bauer disk diffusion method.

RESULTS

The prevalence of SCM at quarter- and cow-level was 31.7% and 53%, respectively. The prevalence of SCM was significantly higher (p < 0.05) in exotic breeds of cattle and those kept under an extensive system of production. A total of 19 bacterial species were isolated with the majority being CNS (40.1%), S. aureus (15.8%) and Micrococcus spp. (10.4%). S. aureus isolates showed varied resistance to the tested antibiotics with the highest resistance being against ceftazidime (75%), amoxycillin (50%) and streptomycin (46.9%). Several S. aureus isolates were resistant to oxacillin (34.4%) and cefoxitin (12.5%). CNSs were more resistant against ceftazidime (79.1%), amoxycillin (34.6%) and oxacillin (32.1%). Majority (92%-100%) of the Staphylococcus spp. were highly sensitive to ciprofloxacin a fluoroquinolone and augmentin.

CONCLUSIONS

The high prevalence of SCM and bacteria resistant to antibiotics shows a need for animal health professionals and farmers to develop strategies for the management of mastitis and antibiotic resistance in dairy cows in the study area.

Characterisation of Milk Microbiota from Subclinical Mastitis and Apparently Healthy Dairy Cattle in Free State Province, South Africa

Bovine mastitis is an inflammation of the udder tissue of the mammary gland brought on by microbial infections or physical damage. It is characterised by physical, chemical, and biological changes in the udder and milk. While several different bacterial species have been identified as causative agents of mastitis, many subclinical mastitis (SCM) cases remain culture-negative. The aim of this study was to characterise milk microbiota from SCM and apparently healthy dairy cows (non-SCM) by 16S rRNA sequencing. Alpha-diversity metrics showed significant differences between SCM cows and non-SCM counterparts. The beta-diversity metrics in the principal coordinate analysis significantly clustered samples by type (PERMANOVA test, p < 0.05), while non-metric dimensional scaling did not (PERMANOVA test, p = 0.07). The overall analysis indicated a total of 95 phyla, 33 classes, 82 orders, 124 families, 202 genera, and 119 bacterial species. Four phyla, namely Actinobacteriota, Bacteroidota, Firmicutes, and Proteobacteria collectively accounted for more than 97% of all sequencing reads from SCM and non-SCM cow samples. The most abundant bacterial classes were Actinobacteria, Bacilli, Bacteroidia, Clostridia, and Gammaproteobacteria in non-SCM cow samples, whilst SCM cow samples were mainly composed of Actinobacteria, Alphaproteobacteria, Bacilli, Clostridia, and Gammaproteobacteria. Dominant bacterial species in non-SCM cow samples were Anthropi spp., Pseudomonas azotoformans, P. fragi, Acinetobacter guillouiae, Enterococcus italicus, Lactococcus lactis, whilst P. azotoformans, Mycobacterium bovis, P. fragi, Acinetobacter guillouiae, and P. koreensis were dominant in the SCM cow samples. The current study found differences in bacterial species between SCM and non-SCM cow milk; hence, the need for detailed epidemiological studies.

Prevalence of subclinical mastitis, its associated bacterial isolates and risk factors among cattle in Africa: a systematic review and meta-analysis

BACKGROUND

Subclinical mastitis (SCM) is one of the most economically important diseases affecting the dairy industry. The SCM does not cause visible changes in the udder or physical changes of the milk as compared to clinical mastitis, and a clear overview of the prevalence and risk factors in the different regions of Africa is still lacking. The objective of this study was to investigate the prevalence of SCM and assess the associated risk factors and dominant bacterial pathogens among cattle in Africa.

MATERIALS AND METHODS

We gathered and systematically reviewed literature concerning SCM, published in English from January 2010 through December 2020 in two databases (PubMed and Web of Science), and meta-analysis was conducted using the 'meta' and 'metafor' packages in the R statistical software.

RESULTS

A total of 258 studies were retrieved and at the end of the screening, 82 full-texts were eligible for inclusion in the meta-analysis. The prevalence of SCM was reported in 11 countries in five regions of Africa, and the random-effects model showed that the weighted pooled prevalence estimate (PPE) was 48.2% (95% CI: 43.6-52.8%). Heterogeneity was high and statistically significant as I2 (proportion of observed variation) was 98.1% (95% CI: 98.0-98.3%), τ2 (true between-study variance) was 0.0433 (95% CI: 0.0322-0.0611), and the Cochran Q statistic was 4362.8 (p < 0.0001). Subgroup and meta-regression analyses showed that East Africa had significantly (p = 0.0092) the highest PPE of SCM (67.7%, 95% CI: 55.7-78.7) followed by West Africa (50.5%, 95%CI: 31.4-69.5), and the lowest was in North Africa (40.3%, 95%: 32.2-48.6). Other significant moderators for SCM were age (p < 0.0001), breed (p = 0.0002), lactation stage (p = 0.019) and parity (p = 0.0008) of cattle. Staphylococcus species (prevalence 43.7%) were the most predominant pathogens, followed by Streptococcus (18.2%) and Escherichia species (9.5%).

CONCLUSION

The present study showed a high variation of SCM prevalence in various parts of Africa, although there is a need for more data in some regions. The reported prevalence is a clear sign of inappropriate management practices among cattle herds and an indicator of the threat that SCM poses to the dairy industry. The information about the predisposing factors may guide effective management and control strategies to reduce transmission of the disease.

Incidence rate, risk factors, and bacterial causes of clinical mastitis on dairy farms in Hawassa City, southern Ethiopia

Mastitis is the most common disease of dairy cattle worldwide, causing economic losses due to reduced yield and poor quality of milk. It is of particular concern in Ethiopia, where effective prevention and control practices are lacking. The objective of the present prospective longitudinal study was to estimate the incidence rate of clinical mastitis (CM), identify the risk factors, isolate the bacterial agents, and determine the risk of recurrence. For this purpose, a total of 217 lactating cows were followed up every two weeks from calving to drying off or the end of the study period. Of these, 79 (36.41%) developed CM, of which 23% had recurrent infections in the same or a different quarter. The overall incidence rate of CM was 83.72 (95% CI: 63.2-98.2) cases per 100 cow-years at risk. In the multivariable Cox regression model, the risk of CM was found to be significantly higher in multiparous cows (HR = 1.96; p = 0.03), in cows with a history of mastitis (HR = 2.04; p = 0.030), in cows that had severely keratinized teat end condition (HR = 7.72; p < 0.001) and in cows kept in poorly cleaned barns (HR = 1.89; p = 0.007). The pathogenic bacteria isolated from mastitis-positive cows were Staphylococcus aureus (28.1%), E. coli (21.1%), Bacillus spp. (14%), Streptococcus spp. (14%), coagulase-negative staphylococci (12.3%), non aureus staphylococci (5.3%), Enterobacter spp. (3.5%), Klebsiella spp. (1.8%), Corynebacterium spp. (1.8%), and Proteus spp. (1.8%). The high incidence rate of CM in the present study shows that the disease spreads rapidly and can be responsible for a significant economic loss to milk producers in the study area. Therefore, raising awareness among dairy farmers, early detection and treatment of cases, post-milking teat disinfection, improvement of the hygienic status of cows and barns, use of dry cow therapy, and culling of chronic cases are recommended as viable measures to prevent and control clinical mastitis in the study area.

Quarter-wise proportion and beta-lactam resistance rate of bovine mastitis associated- Staphylococcus aureus among infectious episodes in Ethiopia: Systematic review and meta-Analysis

Background

Bovine mastitis, a condition with multifactorial etiology, imposes a significant economic burden on the dairy sector in Ethiopia, with Staphylococcus aureus (S. aureus) being one of the leading etiologic agents. The acquisition of a compiled source of information concerning S. aureus is imperative in order to enhance the control and prevention strategies, as well as to facilitate the successful implementation of the national action plan aimed at curbing antimicrobial resistance by the year 2025. Thus, the primary objective of this meta-analysis was to comprehensively summarize the estimates of the proportion and beta-lactam resistance profile of S. aureus in bovine mastitis in Ethiopia.

Methods

electronic bibliographic data such as PubMed, Web of Science, HINARI, Google Scholar, and other databases were used to search articles and quality assessment was performed using the AMSTAR-2. The pooled proportion, the rate of beta-lactam resistance, and a 95% confidence interval were calculated with a random effects model using STATA 17 statistical software. Funnel plots, and Eggers were used to assess publication bias.

Results

Twenty-six (26) cross-sectional studies were included in this meta-analysis. The overall pooled proportion of S.aureus was 35% (95% CI: 0.31 to 0.41). Considerable heterogeneity was observed in the included studies (I2 = 90.75%; P < 0.01). The subgroup analysis of the study region showed significant differences. The highest estimated regional pooled proportion of bovine mastitis-associated S.aureus was 40% in the Amhara and Tigray regions. Funnel plot and Eggers results showed no statistically significant publication bias (Eggers test: p = 0.5656) in estimating the proportion of S.aureus infections in association with bovine mastitis. A total of 14 articles were included to estimate beta-lactam antimicrobial resistance. The estimated pooled beta-lactam antimicrobial resistance rate of S.aureus was resistance to penicillin at 75%, followed by amoxicillin at 67%, ampicillin at 50% and cephalosporin at 57% were evaluated in the treatment of S. aureus. Therefore, the present meta-analysis has revealed that the prevalence of bovine-associated Staphylococcus aureus and its resistance to beta-lactam antibiotics are alarmingly high in the region of Ethiopia. This further emphasizes the vital necessity of implementing effective preventive measures to reduce the incidence and spread of this pathogen across the entire nation.

Isolation and Determination of Antibacterial Sensitivity Characteristics of Staphylococcus aureus from Lactating Cows in West Shewa Zone, Ethiopia

Staphylococcus (S.) aureus is one of the etiologies of bovine mastitis, hindering milk production and productivity in dairy farms. This study was aimed at assessing the distribution of bovine mastitis and the isolation rate of S. aureus in milked cows of West Shewa Zone. The clinical mastitis was diagnosed by physical methods including observation and palpation, whereas the subclinical mastitis was tested by the California mastitis test (CMT). All of the cows tested for mastitis were aseptically sampled (teat-milk) for bacteriology. The bacterium was primarily identified based on colony characterization, catalase, coagulase tests, and Gram stain reaction. Finally, MALDI-TOF Biotyper confirmed the species. The antibacterial sensitivity characteristics of the isolates to different antibacterial drugs were tested by the disk diffusion method. The drugs were selected based on the frequent usage in veterinary medicine in the study area. By using particular primers, the presence of the resistance (mecA and blaZ), and thermonuclease (nuc) genes were determined by polymerase chain reaction (PCR). The data were analyzed by R statistical software. The associations between the dependent variables (prevalence of mastitis and S. aureus) and the explanatory variables were analysed by chi-square (χ2) and logistic regression tests at a 95% confidence interval (CI). Accordingly, 258 lactating cows were examined, of which 97 (37.6%) were mastitis positive. Of these mastitis positive cows, 59 (60.8%) were subclinical and 38 (39.2%) were clinical. Among the 258 milk samples, 43 (16.7%) were positive for S. aureus. According to the results of the current investigation, subclinical mastitis was significantly more prevalent than clinical mastitis ( $p<0.05$ ). The disease was found varied with the lactation stage of the animal, milking with washed hand, udder washing before milking, and tick infestation of the teat. In comparison to animals from farms with lower number of lactating cows, the prevalence of the bacteria was significantly higher in animals managed in farms with large (OR = 12.58, 95% CI = 2.33–68.54, and $p<0.05$ ) and medium (OR = 12.58, 95% CI = 2.33–68.54, and $p<0.05$ ) population of lactating cows per herd. The isoation rate of the bacterium was also found significantly higher in tick-infested cows (OR = 27.69, 95% CI = 9.71–93.01, and $p<0.05$ ) than tick free cows. The antibiogram tests revealed that the isolates resisted penicillin G and tetracycline group drugs (oxytetracycline and tetracycline). Moreover, the nuc gene was confirmed to be present in all of the examined isolates. However, they were not found harboring blaZ and mecA genes. We concluded that S. aureus is sustaining as a main causative agent of bovine mastitis, and they were resistant to the frequently used antibiotics in public and veterinary medicines in the study areas. Therefore, research-based interventions need to be taken in action to combat the pathogen.

Bacterial Etiologies of Subclinical Mastitis in Cows Jos Metropolis, Nigeria

This study was conducted to investigate the prevalence of subclinical mastitis and its contagious and environmental bacterial causes in dairy cows in Jos Metro polis of Plateau State. A total of 208 milk samples were collected aseptically from 52 lactating cows and subjected to the California Mastitis Tests (CMT). Milk samples were transferred into peptone water broth for enrichment, followed with bacteriological assays and biochemical identification of bacteria. Using R Commander version 3.6.2, data such as: breed, age, parity, lactation, and management system of cows were collected, and analysed to determine their relationship with bovine subclinical mastitis. Out of 208 quarter milk samples collected from 52 cows, 35.09 % showed subclinical mastitis. While the Cross-breed cows had 15 % subclinical mastitis recorded, the White Fulani had 78.13 %. Cows of the age 3 to 5 years had the highest prevalence of mastitis, while cows with 4 to 6 calves showed the highest prevalence in the parity category. The early lactation stage of these cows showed the highest prevalence. The environmental bacteria isolated where E. coli, K. pneumoniae, K. oxytoca, C. freundii, K. aerogenes, and Proteus sp. with E. coli having the highest frequency of 40.86 %, followed by K. Pneumoniae with 17.79 %. The contagious bacteria isolated were S. aureus, S. agalactiae, and Corynebacterium sp. with S. aureus occurring most with 69.71 %. This study concluded that the prevalence of subclinical mastitis is high in cows in the study area. It was also discovered that the breed of cow, age of cow, parity number, stage of lactation and husbandry systems have an impact on subclinical mastitis. S. aureus with the highest frequency, indicated that contagious microbes have more effect on subclinical mastitis than environmental microbes.

Prevalence of Bovine Mastitis and Its Associated Risk Factors among Dairy Cows in Ethiopia during 2005–2022: A Systematic Review and Meta-Analysis

Bovine mastitis remains a major prevalent disease in cattle and places a significant economic burden on the global dairy industry. The goal of this systematic review and meta-analysis was to examine the overall prevalence of mastitis and its associated risk factors among dairy cows. Scientific articles written in English were recovered from PubMed, ScienceDirect, Web of Science, Google Scholar, Cochrane Library, and other sources from Google Engine and University Library Databases. “Prevalence,” “bovine mastitis,” “clinical mastitis,” “subclinical mastitis,” “associated factors,” “dairy cows,” and “Ethiopia” were search terms used for this study. For critical appraisal, PRISMA 2009 was applied. Heterogeneity and publication bias were evaluated using Cochran's Q, inverse variance (I²), and funnel plot asymmetry tests. A random-effects model was used to calculate the pooled burden of mastitis and its associated factors among dairy cows, along with the parallel odds ratio (OR) and 95% confidence interval (CI). A total of 6438 dairy cows were included in the 17 eligible studies for this meta-analysis. The overall pooled prevalence of mastitis among dairy cows in Ethiopia was 43.60% (95% CI: 34.71, 52.49), of which 12.59% (95% CI: 7.18, 18.00) and 32.21% (95% CI: 24.68, 39.74) were clinical and subclinical cases, respectively. Of the regions, the highest and lowest pooled prevalence estimates of mastitis among dairy cows were 49.90% (95% CI: 31.77, 68.03) and 25.09% (95% CI: 3.86, 46.32) in the Oromia and Amhara regions, respectively. The highest pooled prevalence estimate in the study period was recorded between 2017 and 2022, with a pooled prevalence estimate of 46.83% (95% CI: 35.68, 57.97), followed by the study period from 2005 to 2016, with a pooled prevalence estimate of 39.97% (95% CI: 25.50, 54.44). Gram-positive bacteria (84.70%) were the most prevalent mastitis-causing agents compared with Gram-negative bacteria (15.30%). Breed (AOR: 2.17, 95% CI: 1.44, 2.90), lactation stage (AOR: 1.59, 95% CI: 1.04, 2.15), parity (AOR: 3.31, 95% CI: 1.69, 4.94), history of mastitis (AOR: 3.56, 95% CI: 2.40, 4.71), floor type (AOR: 1.59, 95% CI: −0.16, 3.34), and teat injury (AOR: 6.98, 95% CI: 0.33, 13.64) were factors significantly associated with mastitis among dairy cows in Ethiopia. Early diagnosis and proper medication, as well as implementing appropriate prevention and control measures, are necessary for the management of mastitis in dairy cows.

Phenotypic and Molecular Characterization of Bovine Mastitis Milk Origin Bacteria and Linkage of Intramammary Infection With Milk Quality

Mastitis is a multi-etiological complex disease of dairy cows and negatively affects the quality and quantity of milk. Milk is a nutritious food for human being; milk quality is negatively affected by intramammary infection of dairy cows. A total of 300 milk samples were collected from mastitis dairy cows irrespective of parity and stage of lactation, 235 (78.33%) samples were culturally positive and yielded 1,100 bacterial isolates. Staphylococcus aureus was found to be the prime etiological agent involved in the mastitis of dairy cows, followed by Escherichia coli and other environmental pathogens. On the molecular characterization of isolates obtained from the milk culture, various toxic genes such as nuc, seb, hla, stx1, stx2, hly, and Sagl were found on different isolated bacteria. Milk somatic cell counts (SCC) were found to be directly related to the severity of mastitis. On drawing the SCC correlation with milk components, it was found that SCC had a significant negative correlation with fat, lactose, solid not fat (SNF), and ash. It was concluded that mastitis-affected milk contains numerous pathogenic bacteria, toxins, and reduced milk quality, which is unfit for human consumption.

Bacterial profile of bovine mastitis in Ethiopia: a systematic review and meta-analysis

Background

Bovine mastitis is the commonest episode of infection in the dairy industry, which often occurs after damage of epithelial cells lining the teat duct. It is ranked as the second most important cause of milk production loss directly and a devastating disease with a higher incidence leading to the culling of dairy cows. Thus, this systematic review and meta-analysis is aimed to quantitatively estimate the current status of mastitis in general and bacterial mastitis particular in Ethiopia.

Methods

A literature search was carried from major databases and indexing services including PubMed, Google Scholar, Science Direct. Also, local institution repositories were searched to retrieve unpublished MSc and PhD theses. All studies were included addressing the prevalence of mastitis and bacterial isolates conducted in Ethiopia. Microsoft Excel was used to extract data and was imported to R Studio for the analyses. The random-effects model at a 95% confidence level was used for pooled estimates of outcomes. The degree of heterogeneity was computed by Higgins's I² statistics. Publication bias was checked by using the funnel plots of standard error augmented by Begg's and Egger's tests.

Results

A total of 46 studies with 15,780 cows were included in this study. All studies have collected 18,478 suspected samples for bacterial isolation. While pooled prevalence estimate of mastitis was 47.6%, the bacterial isolates pooled prevalence was 33.1%. The bacterial mastitis was 6.5% in cows infected by clinical patients and was 28.3% subclinical patients. The common isolates were Staph aureus, Strep species, Staph epidermis, Escherchia coli, Corynebacterium bovis, Coagulase Negative Staphylococcus and Klebsiella species. A univariate meta-regression analysis evidenced that the type of mastitis and management system was a possible source of heterogeneity (P-value = 0.001).

Conclusion

The pooled prevalence of bacterial mastitis in Ethiopian dairy cattle was high. The analysis showed bacterial pathogens like Staphylococcus aureus, Staph epidermis, Strep species and Coagulase Negative Staphylococcus are majorly accounted for bovine mastitis in Ethiopia. Therefore, the highly prevalent and commonly isolated pathogens cause contagious mastitis which require immediate attention by dairy producers to put under control by devising robust mastitis prevention and control interventions.

The Indicators of Clinical and Subclinical Mastitis in Equine Milk

Simple Summary

Mastitis, the inflammation of the mammary gland, is a major problem in a mare’s perinatal period, negatively affecting both the health of the mare and newborn foal and the quality of milk produced on dairy equine farms. The detection of mastitis is therefore one of the important goals in the equine breeding and dairy industry. This study aimed to determine the somatic cell count (SCC), the percentage of the immune cells, the electrical conductivity (ECM), and bacteriological index (BII) in milk collected from mares with (CM) and without (NCM) clinical symptoms of mastitis. The increase in examined indicators is suspected to be a subclinical mastitis indicator, therefore the study aimed to separate two subgroups, mares with (SM) and without (NSM) subclinical symptoms of mastitis. In milk from NCM mares the values of SCC, immune cells, and ECM increased immediately after birth and weaning, whereas during the rest of the lactation period their values were at a low level. Similarly, in milk from CM mares, the values of examined indicators were high and comparable to the weaning time. An increase in the level of examined indicators may become an early indication of subclinical mastitis.

Abstract

The somatic cell count in milk (SCC) and electrical conductivity of milk (ECM) are indicators of the health status of the mammary gland. Among somatic cells, mainly polymorphonuclear neutrophils (PMN), macrophages (MAC), and lymphocytes (LYM) are rated. This study aimed to determine the SCC, PMN, MAC, LYM, ECM, and bacteriological index (BII) in milk collected from mares with (CM) and without (NCM) clinical symptoms of mastitis concerning mares with (SM) and without (NSM) subclinical mastitis. Milk samples were collected from 27 mares divided into NCM (n = 12) and CM (n = 15) groups. In samples, SCC quantification, cytological examinations, ECM measurement, and bacteriological examination were performed. In NCM mares, the values of SCC, PMN, MAC, LYM, and ECM were higher in initial than in consecutive examined days after birth until weaning. After weaning the proportion of SCC, PMN, MAC, LYM, ECM, and BII increased and did not differ with the average values in CM mares. These equine milk indicators may reflect an early symptom of subclinical mastitis and in the future may be used in the early detection of mastitis or as a tool of assessment of the health status of the mammary gland in the dairy equine farm.

Cumulative Effect of Subclinical Mastitis on Immunological and Biochemical Parameters in Cow Milk

Mastitis is a complex and multifactorial disease that leads to chemical, physical, and bacteriological changes in milk, which is associated with great economic losses. This study was carried out on lactating cows to investigate the effect of subclinical mastitis (SCM) on milk production through the estimation of immunological and biochemical characteristics of milk. Therefore, a total of 200 apparently-healthy lactating cows were randomly selected from different areas in Baghdad and Maysan provinces in Iraq from April to July 2021, and 100 ml of fresh milk was directly collected from each cow. Milk samples were examined by the California mastitis test (CMT), and IgG concentration in milk was estimated by the ELISA method. Moreover, the changes in biochemical parameters and enzymatic parameters were analyzed to determine the prevalence of SCM. Based on the results of the CMT test, the prevalence of SCM was 41.5% with a significant increase in a mild degree of severity (61.45%). IgG antibodies increased significantly in positive cows (4.92± 0.21 µg/ml). Significant prevalence of infection was observed among cows ≥5 years old compared to those <5 years, crossbred ones compared to natives, and those with lower milk production without udder/milk abnormalities, compared to cows with normal milk production. However, a significant difference was observed between the two regions under investigation (i.e., Baghdad and Maysan provinces of Iraq). Results of biochemical and enzymatic parameters showed significant increases in the concentration of Cl, FFA, and Na, and a reduction in LAC and TP, though not in Ca and K. The pH of mastitis milk was significantly higher. Although no significant difference was observed in the values of ALT and LDH, AST was increased in mastitis milk. In conclusion, this study is one of the first reports on the estimated concentration of IgG in mastitis milk samples in Iraq. Increases in the concentration of SSCs and IgG in milk can apply to the detection of intra-mammary infections.

Effects of hydrolyzable tannin extract obtained from sweet chestnut wood (Castanea sativa Mill.) against bacteria causing subclinical mastitis in Thai Friesian dairy cows

Background and Aim:

Hydrolyzable tannins are an important group of secondary plant metabolites, which are known for antimicrobial activity. This study aimed to assess the efficiency with which a hydrolyzable tannin extract from sweet chestnut wood (Castanea sativa Mill.) could inhibit mastitis-causing bacteria in vitro.

Materials and Methods:

The negative control used was sterile water, and the positive controls were penicillin and gentamicin. The treatments included five concentrations of hydrolyzable tannins (63, 190, 313, 630, and 940 mg/mL). In cows with subclinical mastitis, the bacteria causing the disease were isolated and identified. Then, the antibacterial activity of the hydrolyzable tannin extract was assessed by the disk diffusion method, by determining the minimum inhibitory concentration (MIC) and by determining the minimum bactericidal concentration (MBC).

Results:

Penicillin inhibited (p<0.01) the growth of Staphylococcus aureus, Streptococcus uberis, and Pseudomonas aeruginosa but could not inhibit (p>0.05) the growth of Streptococcus agalactiae, Escherichia coli, and Klebsiella pneumoniae. However, gentamicin and hydrolyzable tannins could inhibit (p<0.01) all isolated bacteria. Increasing the concentration of hydrolyzable tannin extract resulted in a quadratic increase in the inhibition zone diameter of S. aureus and S. agalactiae and a linear increase in the inhibition zone diameter of E. coli, K. pneumoniae, and P. aeruginosa. In addition, 630 and 940 mg/mL of hydrolyzable tannin extract showed the highest antibacterial activity against S. agalactiae and E. coli (p<0.01), while 940 mg/mL concentration had the highest antibacterial activity against K. pneumoniae (p<0.01). The MIC and MBC of the extract were 27.3-190 mg/mL and 58.8-235 mg/mL, respectively, with the MBC: MIC ratio being 2:1.

Conclusion:

The antimicrobial activity of the hydrolyzable tannin extract against subclinical mastitis bacteria was comparable to the antibiotics (positive controls) at concentrations over 630 mg/mL. Although these in vitro findings are promising, further research is needed to determine whether hydrolyzable tannins could be used to control or prevent subclinical mastitis in dairy cows.

Prevalence of Mastitis Pathogens and Antimicrobial Susceptibility of Isolates From Cattle and Buffaloes in Northwest of Pakistan

Mastitis is the most prevalent disease of dairy animals, imparting huge economic losses to the dairy industry. There is always a dire need to monitor the prevalence of mastitis, its bacteriology, and evaluation of antimicrobial susceptibilities for mastitis control and prevention. Therefore, the objectives of this study were to investigate: (i) the prevalence of mastitis in cattle and buffaloes; (ii) identification of bacteria associated with mastitis; (iii) antimicrobial susceptibility of bacterial isolates. Milk samples (n = 1,566) from cattle (n = 1,096) and buffaloes (n = 470) were processed for detection of mastitis using the California mastitis test in the year 2018-19. A total of 633 mastitic milk samples were further processed for bacteriology and antimicrobial susceptibility testing by the disc diffusion method. Overall, the prevalence of clinical and subclinical mastitis was 17 and 57% in both species. Clinical mastitis was higher in cattle (20%) compared to buffaloes (11%), whereas subclinical was higher in buffaloes (66%) than cattle (53%). Besides, month-wise prevalence was higher in hot and humid months in both species. Staphylococci spp. (34%) were the most predominant bacterial isolates from mastitic milk, followed by Escherichia coli (19.4%), Streptococci spp. (9%), and Klebsiella spp. (8%). Most of the bacteria were susceptible to gentamicin (92%) and enrofloxacin (88%), when a panel of 16 different antimicrobials was tested. Nevertheless, most of the isolates were resistant to sulphamethoxazole (99%), lincomycin (98%), oxytetracycline (89%), ampicillin (86%), and doxycycline (85%). This study concludes a high prevalence of mastitis caused by Staphylococcal spp. in cattle and buffaloes belonging to the northwest of Pakistan, and gentamicin and enrofloxacin might be appropriate antimicrobial agents in the treatment of bovine mastitis.

Successful treatment of recurrent subclinical mastitis in cows caused by enrofloxacin resistant bacteria by means of the sequential intramammary infusion of enrofloxacin HCl-2H2O and ceftiofur HCl: a clinical trial

Background

Recurrent subclinical mastitis (RScM) due to resistant bacteria has low clinical and bacteriological cure rates, often requiring the culling of cows. The sequential intra-mammary administration of enrofloxacin hydrochloride-dihydrate (enro-C) followed by ceftiofur HCl may be useful for treating these cases.

Objectives

This study assessed the bacteriological and clinical cure-efficacies of the sequentially intramammary administration of enro-C, followed by ceftiofur HCl to treat RScM in Holstein/Friesian cows.

Methods

This trial was conducted in a herd with a high prevalence of RScM, and 20 Holstein/Friesian cows were included: 45% suffering subclinical mastitis and 38.9% of the mammary quarters affected. Twenty-nine bacterial isolates in vitro resistant to enro-C were obtained (coagulase-negative Staphylococcus spp, 55.2%; Staphylococcus aureus, 27.6%; Escherichia coli, 6.9%; Streptococcus uberis, 6.9%; Corynebacterium bovis, 3.4%). Polymerase chain reaction-isolated the following genes linked to enro-C resistance: chromosomal (gyrA) and plasmid (aac(6')-lb-cr). The treatments were as follows: twice-daily intramammary infusions of enro-C (300 mg/10 mL) for 5 days. Cows clinically considered treatment failures were also treated with intramammary ceftiofur (125 mg/10 mL, twice daily for 5 days. The clinical and bacteriological cure rates were carried out when completing each treatment phase and at 14 and 21 days, aided by a California mastitis test, somatic cell count, and failure to identify the initially causative bacteria.

Results

Enro-C achieved 65% clinical and bacteriological cure rates, and 100% cure rates were obtained after the rescue treatment with ceftiofur HCl.

Conclusions

Outstanding clinical and bacteriological cure rates in cows affected by RScM were achieved with the consecutive intramammary infusions of enro-C, followed by ceftiofur HCl.

Prevalence of Staphylococcus aureus, Methicillin-Resistant Staphylococcus aureus and Potential Risk Factors in Selected Dairy Farms at the Interface of Animal and Human in Bishoftu, Ethiopia

Background

Staphylococcus aureus (S. aureus) has been reported as the most commonly isolated highly contagious pathogen from human, animals and animal products. Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a significant pathogen with zoonotic potential that could have devastating consequence for the health and well-being of animals and human.

Methods

A cross-sectional study was conducted from July 2020 to January 2021. A total of 233 samples from cow milk, udder swabs and milkers' hand swabs were collected for culture and identification based on the standard protocol. Antimicrobial susceptibility tests were performed for all isolates by using Kirby Bauer's disk diffusion test. MRSA was detected by cefoxitin disk diffusion test.

Results

S. aureus was isolated from 50 (21.46%) of 233 samples and the prevalence of MRSA was 4%. The highest prevalence was found in cow milk 36 (25.53%) followed by hand swabs 10 (19.23%) and udder swabs 4 (10%). S. aureus prevalence was 58.33%, 30.0%, 21.43%, 17.92%, 15.79% in farm D, C, E, A, B respectively. A large percentage (58.33% and 30%) were from farm D and C. S. aureus isolation rate showed statistically significant association with farm types (p = 0.011) and with previous mastitis exposure (p = 0.001). High level of resistance was observed to penicillin (94%) and ampicillin (92%), but low level resistance to gentamicin (0%), amikacin (0%), ceftriaxone (0%), chloramphenicol (4%), ciprofloxacin and cefoxitin (4%). The overall prevalence of multidrug resistance (MDR) was 10.42%.

Conclusion

Prevalence of S. aureus in milk showed statistically significant association with respect to previous mastitis exposure and farm types (p = 0.011). High level of resistant to penicillin and ampicillin was observed. Therefore, effective mastitis control programs, best veterinary practice among all farms and use of antibiotics in the farm should be strictly controlled.

Prevalence of bovine mastitis and main risk factors in Tunisia

Tunisian milk chain is in danger with a dramatical reduction of milk production over the last years. Improving the quality of milk seems mandatory to improve farmers' income, but for the moment, there is only scarce data on milk quality management in Tunisia. In this context, the aims of our study were first to describe the prevalence of bovine mastitis in 267 cows from 71 representative small dairy farms in the North (43.7%) and Center (56.3%) regions of Tunisia, using mastitis detection by California Mastitis Test (CMT) on milk quarter and clinical signs, and second, to assess possible risk factors for mastitis from animal, environment, and breeding management. In parallel, cow and bulk milk somatic cell count (SCC) were analyzed. Our results demonstrated that 60.3% of cows showed mastitis as determined by CMT and clinical examinations. Increased stage of lactation, parity, udder depth, and type of milking were significantly (P < 0.05) associated with increased odds of mastitis prevalence. The mean of individual cow SCC (ISCC) and bulk milk SCC (BMSCC) was very high (1083 × 10³ cells/mL and 698 × 10³ cells/mL, respectively), all ranks and stages of lactations combined. These high values confirm the infectious origin of mastitis that we found caused mainly by Staphylococcus aureus and coagulase-negative Staphylococci. In conclusion, control of the identified risks factors and improved biosecurity measures must be encouraged to restore udder health and milk quality and thus productivity and durability of Tunisian milk chain.

Subclinical mastitis in dairy cows in major milk-producing areas of Sri Lanka: Prevalence, associated risk factors, and effects on reproduction

Compared with clinical mastitis, the subclinical form of mastitis (SCM) is more common and thought to cause more economic losses to the dairy industry. The current study aimed to investigate the prevalence, risk factors of SCM, and effects on reproduction of dairy cows in major milk-producing areas of Sri Lanka. A total of 1,357 cows of selected farms in 3 regions were examined in the study. California Mastitis Test was conducted for individual cows, and a score of 2 or more for any quarter without any clinical symptoms and abnormalities in milk was considered as positive for SCM. Samples from infected animals were collected and subjected to bacteriological analysis. A pretested questionnaire was used to collect data on individual cows and herds. Risk factors associated with SCM were analyzed using binary logistic regression in generalized linear mixed models. The effect of SCM on calving to conception interval and days from calving to artificial insemination were analyzed by survival analysis using Cox's proportional hazards regression and Kaplan-Meier survival function estimates, respectively. A Poisson regression model was run to determine the effect of SCM on number of artificial inseminations per conception. The prevalence of SCM was 57.5, 11.8, and 45.5% in the regions A, B, and C, respectively. The most common pathogen was Staphylococcus aureus, with 87.1, 56.5, and 92.3% in the regions A, B, and C, respectively. Logistic regression analysis showed that parity, farming system, milking area, region, and herd significantly affect the prevalence of SCM. Subclinical mastitis during the pre-breeding period was associated with 14% increase in the chance of having a greater number of artificial inseminations per conception. Likewise, median days from calving to artificial insemination was longer in cows with SCM compared with normal cows (79 and 64 d, respectively). Therefore, SCM affected the inseminated proportion of studied cows. However, SCM was not associated with the calving to conception interval. The results revealed that the cow factors and milk hygiene play a significant role in the prevalence of SCM.

Application of culture, PCR, and PacBio sequencing for determination of microbial composition of milk from subclinical mastitis dairy cows of smallholder farms

Mastitis is a cow disease usually signalized by irritation, swelling, and soreness of the udder. It is characterized by physical, chemical, and biological changes in the udder and milk. The aim of this study was to detect and characterize pathogens causing subclinical mastitis (SCM) from the milk of dairy cows of small-scale farmers through culture and molecular techniques. Milk was collected from 32 cows belonging to 8 small-scale farmers around Harrismith District, South Africa. The results showed that screening of SCM by California mastitis test and somatic cell counts (SCC) was 21.87 and 25%, respectively. Culture methods revealed the presence of Staphylococcus aureus at 93% followed by Streptococci spp. and Escherichia coli at 36.4 and 13.3%, respectively. The PCR could only detect E. coli, while single-molecule real-time sequencing showed a total of 2 phyla, 5 families, 7 genera, and 131 species. Clostridiaceae was the most abundant family, while Romboutsia was the most abundant genus followed by Turicibacter spp. The present study has documented the occurrence of SCM causing pathogens in milk collected from cows of small-scale farmers in Harrismith, indicating that SCM may be present at higher levels than expected.

Subclinical Mastitis in Selected Bovine Dairy Herds in North Upper Egypt: Assessment of Prevalence, Causative Bacterial Pathogens, Antimicrobial Resistance and Virulence-Associated Genes

Mastitis is a significant disease affecting dairy cattle farms in Egypt. The current study aimed to investigate the prevalence and major bacterial pathogens causing subclinical mastitis (SCM) in three bovine dairy herds, with a history of SCM, at three Governorates in North Upper Egypt. The antimicrobial resistance profiles and specific virulence-associated genes causing bovine SCM were investigated. One thousand sixty-quarter milk samples (QMS) were collected aseptically from 270 apparently healthy cows in three farms and examined. The total prevalence of SCM was 46% and 44.8% based on California Mastitis Test (CMT) and Somatic Cell Count (SCC), respectively. Bacteriological examination of CMT positive quarters revealed that the prevalence of bacterial isolation in subclinically mastitic quarters was 90.4% (26 and 64.3% had single and mixed isolates, respectively). The most frequent bacterial isolates were E. coli (49.8%), Staphylococcus aureus (44.9%), streptococci (44.1%) and non-aureus staphylococci (NAS) (37.1%). Antimicrobial susceptibility testing of isolates revealed a high degree of resistance to the most commonly used antimicrobial compound in human and veterinary medicine. Implementation of PCR revealed the presence of mecA and blaZ genes in 60% and 46.7% of S. aureus isolates and in 26.7% and 53.3% of NAS, respectively. Meanwhile 73.3% of streptococci isolates harbored aph(3’)-IIIa gene conferring resistance to aminoglycosides and cfb gene. All E. coli isolates harbored tetA gene conferring resistance to tetracycline and sul1 gene conferring resistance to sulfonamides. The fimH and tsh genes were found in 80% and 60%, respectively. A significant association between the phenotypes and genotypes of AMR in different bacteria was recorded. The presence of a high prevalence of SCM in dairy animals impacts milk production and milk quality. The coexistence of pathogenic bacteria in milk is alarming, threatens human health and has a public health significance. Herd health improvement interventions are required to protect human health and society.

Prevalence of Mastitis and Antibiotic Resistance of Bacterial Isolates from CMT Positive Milk Samples Obtained from Dairy Cows, Camels, and Goats in Two Pastoral Districts in Southern Ethiopia

Simple Summary

A study was carried out from August 2017 to February 2018 on lactating dairy cows, one-humped dromedary camels, and goats to determine mastitis in the Bule Hora and Dugda Dawa districts of in Southern Ethiopia. Milk samples from 564 udder quarters and udder halves from 171 animals consisting of 60 dairy cows, 51 camels, and 60 goats were tested for mastitis. Sixty-four positive udder milk samples were cultured, and bacterial mastitis pathogens were isolated and identified. The antibiotic resistance of bacterial isolates from milk with mastitis was tested against nine antimicrobials commonly used in the study area. Cow-level prevalence of mastitis in dairy cows, camels, and goats was 33.3%, 26.3%, and 25%, respectively. The quarter-level prevalence of mastitis in cows, camels and goats was 17.6%, 14.5%, and 20%, respectively. In cattle, the prevalence was significantly higher in Dugda Dawa than in Bule Hora. Major bacterial isolates were coagulase-negative Staphylococcus species (39.1%), S. aureus (17.2%), S. hyicus (14.1%), and S. intermedius and Escherichia coli (9.4% each). In camels, udder abnormality and mastitis were significantly higher in late lactation than in early lactation. Mastitis tends to increase with parity in camels. E. coli isolates were highly resistant to spectinomycin, vancomycin, and doxycycline, whereas most S. aureus isolates were multidrug-resistant. Most of the rural and periurban communities in this area consume raw milk, which indicates a high risk of infection with multidrug-resistant bacteria. We recommend community-focused training programs to improve community awareness of the risk of raw milk consumption and the need to boil milk.

Abstract

A study was carried out from August 2017 to February 2018 on lactating dairy cows, one-humped dromedary camels, and goats to determine mastitis in the Bule Hora and Dugda Dawa districts of in Southern Ethiopia. Milk samples from 564 udder quarters and udder halves from 171 animals consisting of 60 dairy cows, 51 camels, and 60 goats were tested for mastitis. Sixty-four positive udder milk samples were cultured, and bacterial mastitis pathogens were isolated and identified. The antibiotic resistance of bacterial isolates from milk with mastitis was tested against nine antimicrobials commonly used in the study area. Cow- and quarter-level prevalence of mastitis in dairy cows, camels, and goats was 33.3%, 26.3%, and 25% and 17.6%, 14.5%, and 20%, respectively. In cattle, the prevalence was significantly higher in Dugda Dawa than in Bule Hora. Major bacterial isolates were coagulase-negative Staphylococcus species (39.1%), S. aureus (17.2%), S. hyicus (14.1%), and S. intermedius and Escherichia coli (9.4% each). In camels, udder abnormality and mastitis were significantly higher in late lactation than in early lactation. Mastitis tends to increase with parity in camels. E. coli isolates were highly resistant to spectinomycin, vancomycin, and doxycycline, whereas most S. aureus isolates were multidrug-resistant. Most of the rural and periurban communities in this area consume raw milk, which indicates a high risk of infection with multidrug-resistant bacteria. We recommend a community-focused training program to improve community awareness of the need to boil milk and the risk of raw milk consumption.

Identification and antimicrobial susceptibility of methicillin-resistant Staphylococcus aureus-associated subclinical mastitis isolated from dairy cows in Bogor, Indonesia

Background and Aim:

Subclinical mastitis is an udder infection devoid of clinical symptoms, and Staphylococcus aureus is one of the bacteria causing this disease. This study aimed to identify and determine the prevalence and antibiotic susceptibility of methicillin-resistant S. aureus (MRSA)-associated subclinical mastitis isolated from dairy cows in Bogor, Indonesia.

Materials and Methods:

S. aureus was isolated from subclinical mastitis milk specimens. All strains were confirmed by polymerase chain reaction-based detection of staphylococcal nuc, and MRSA was confirmed by the presence of mecA. Antibiotic susceptibility was determined using the disk diffusion method.

Results:

From 86 milk samples, 49 isolates (57%) were confirmed as S. aureus. All S. aureus isolates were susceptible to tetracycline, gentamicin, chloramphenicol, erythromycin, and trimethoprim/sulfamethoxazole. Nine isolates were identified as MRSA (10.5%).

Conclusion:

In this study, we reported MRSA-associated subclinical mastitis in Bogor, Indonesia.

Global and countrywide prevalence of subclinical and clinical mastitis in dairy cattle and buffaloes by systematic review and meta-analysis

In the present study, subclinical mastitis (SCM) and clinical mastitis (CM) prevalence for various countries in the World were calculated by using online and offline databases. The SCM and CM prevalence studies reported during 1967-2019 were collected, reviewed, and a meta-analysis was done in R-Software. A total of 222 and 150 studies from the World and 103 and 37 studies from India on SCM and CM, respectively were included. The pooled prevalence of SCM and CM were 42% [Confidence Interval (CI) 38-45%, Prediction Interval (PI) 10-83%] and 15% [CI 12-19%, PI 1-81%] in the World respectively, 45% [CI 40-49%, PI 11-84%] and 18% [CI 14-23%, PI 3-60%] in India respectively. Continent-wise analysis indicated a higher prevalence of SCM in North America and CM in Europe and among the countries, a higher SCM prevalence in Uganda and CM in the United Kingdom was observed. Further, species-wise indicated a higher SCM and CM prevalence in buffaloes of the World than the cattle. Based on method-wise, SCM and CM prevalence were high in somatic cell count and clinical examination, respectively in the World. The SCM prevalence was higher than CM and indicated the importance of SCM in dairy cattle. This might result in low milk productivity in dairying and may set off losses to dairy farmers. Hence, there is an urgent need to reduce the SCM and CM prevalence by implementing scientific dairy management, good feeding practices, and timely therapeutic interventions for increasing the benefits from dairying to the farmers in the World.

Prevalence and risk factors for multidrug-resistant Escherichia coli isolated from subclinical mastitis in the western Chitwan region of Nepal

Subclinical mastitis (SCM) represents a significant burden and challenge to modern dairy management. Multidrug-resistant Escherichia coli (MDR E. coli) in milk poses a public health threat to humans especially via the consumption of unpasteurized dairy products. This study aimed to determine the occurrence of MDR E. coli in cows and buffalo in the households of the western part of the Chitwan district of Nepal. A total of 243 lactating cows and buffalo were included in this study. Milk samples (n = 972) were screened using the California Mastitis Test (CMT). The E. coli was isolated from milk samples that were positive for CMT using standard bacteriological protocols. A semi-structured questionnaire was administered to farmers to identify the risk factors associated with the occurrence of SCM in cows and buffalo. Of the 243 dairy animals screened, 42.8% (n = 104/243) showed positive CMT results. However, of the 972 quarters sampled, only 19.3% (n = 188/972) were positive for SCM. The prevalence of E. coli in these animals was found to be 16.5% in animals (n = 40/243). However, E. coli was isolated from only 5% (n = 49/972) of the quarters. Of the 49 E. coli isolated, the resistance to ceftriaxone (38.8%, n = 19/49) and ciprofloxacin (37.7%, n = 17/49) were the most prevalent. Animals with a history of mastitis were 3.57 times more likely to have SCM than other animals. Similarly, lactating animals with previous teat abrasions were 3.22 times more likely to develop SCM than animals without teat injuries. As expected, cleaning the barn once in 2 to 3 d was associated with an increased occurrence of SCM in lactating cows. This study reports the occurrence of MDR E. coli in SCM, which poses a public health threat. Creating awareness of milk pasteurization, and food safety practices are necessary among the farmers.

Isolation and Identification of Major Pathogenic Bacteria from Clinical Mastitic Cows in Asella Town, Ethiopia

Mastitis is a multietiological and complex disease causing inflammation of the parenchyma of mammary glands and is a problem in many dairy cows. The objective of this study was to isolate and identify the pathogenic bacteria that cause bovine clinical mastitis. A cross-sectional study was undertaken between November 2018 to April 2019 on a small scale and government dairy farms in Asella town. Cow's udder and teats were physically examined to detect clinical mastitis. A total of 83 milk samples were collected from 46 cows that show clinical sign of mastitis from a total of 12 farms. Isolation and identification of major bacterial species were carried out by culturing different media and using primary and secondary biochemical tests. Out of the 83 samples collected and examined, all (100%) were positive for the cultural isolation of bacterial species. The bacteria were identified to genus and species level. Among the 83 isolates, 32 (38.6%), 24 (28.9%), and 6 (7.2%) were Staphylococcus aureus, Staphylococcus intermedius, and Staphylococcus hyicus, respectively. Other bacteria like Escherichia coli 12 (14.5%) and Streptococcus species 2 (2.4%) were also isolated. Bacillus species 2 (2.4%), Proteus species 2 (2.4%), and 3 (3.6%) of them were mixed bacterial infections. The present study revealed that both contagious and environmental bacterial pathogens were responsible for the occurrence of clinical mastitis. Proper milking practices and farm husbandry practices and future detailed studies up to the species level and on antibiotic profiles of the pathogens are needed.

Influence of pre and postpartum alpha-tocopherol supplementation on milk yield, milk quality, and udder health of Jersey crossbred cows at tropical lower Gangetic region

Background and Aim:

Alpha-tocopherol supplementation influences milk yield, milk quality, and udder health of dairy cows, which needs to be investigated for Jersey crossbred cows at hot-humid climate. Therefore, the present study was framed with an objective to study the effect of pre and postpartum Alpha-tocopherol supplementation on milk yield, milk quality, and udder health status of Jersey crossbred cows at tropical climate.

Materials and Methods:

For this study, 19 similar parity, body condition score, and production level dairy animals were separated randomly into three groups, namely, Control, T1 and T2. Control group (no supplementation) was compared with two treatment groups, namely, T1 and T2. Supplementation of Alpha-tocopherol was done in concentrate fed to the animals (at 1 g/cow/day) 30 days prepartum to 30 days postpartum in T1 and 30 days prepartum to 60 days postpartum in T2 groups. Observations were taken for different parameters up to 5 months of lactation.

Results:

Statistically analyzed data revealed that overall significantly (p<0.01) more milk production was found in T2, followed by T1 than the control group. Overall significantly (p<0.01) lower somatic cell counts and modified California mastitis tests were recorded in T2, followed by T1 than the control group. Overall significantly (p<0.01), better milk quality in terms of methylene blue reduction test was found in T2, followed by T1 than control groups. Differences in the milk composition of all three groups were non-significant (p>0.05).

Conclusion:

Supplementation of Alpha-tocopherol during prepartum to initial lactation period may enhance milk yield, milk quality, and udder health status of Jersey crossbred cows at the tropical lower Gangetic region.

Prevalence, Etiology, and Risk Factors of Mastitis in Dairy Cattle in Embu and Kajiado Counties, Kenya

Bovine mastitis continues to be a leading cause of heavy economic losses in the dairy industry and a public health hazard globally. This cross-sectional study investigated the prevalence, etiologies of clinical and subclinical mastitis, and associated predisposing factors in Embu and Kajiado counties in Kenya. A semistructured questionnaire was administered to 154 smallholder dairy farmers to collect data on management practices, animal factors, and disease history. A total of 395 dairy cows were initially screened for subclinical mastitis using the California mastitis test (CMT), and milk samples were aseptically collected. Both CMT positive and CMT negative samples were analyzed using conventional bacteriological isolation and identification procedures. In the present study, the overall prevalence of mastitis based on CMT and clinical examination was 80% (316/395), out of which 6.8% (27/395) was clinical mastitis, while 73.1% (289/395) was subclinical mastitis. Based on culture, the overall prevalence of clinical and subclinical mastitis was 51.6% (815/1580), 74.4% (294/395), and 76.6% (118/154) at the quarter, cow, and farm level, respectively. From the 1574 milk samples analyzed by cultured, 1016 bacteria were yielded. The predominant bacteria were coagulase-negative Staphylococcus (CNS), 42.8% (435/1016), and in decreasing order, Streptococcus species, 22.2% (226/1016), Staphylococcus aureus, 15.7% (160/1016), and Pseudomonas aeruginosa, 5.1% (52/1016), and the least was Enterobacter species, 0.7% (7/1016), while 23.7% of the sample yielded no bacterial growth. Risk factor analysis revealed that milking mastitic cows last (p=0.002), using a clean udder drying towel for each cow (p=0.033) and previous history of mastitis (p=0.046) were significantly associated with presence of mastitis. The current study has shown a relatively high prevalence of subclinical mastitis with CNS as predominant bacteria. Therefore, control measures are urgently warranted. Management factors such as milking mastitic cows last, using a clean towel for udder drying for each cow, and culling mastitic cows should be considered and included in the Kenyan mastitis control programs.

The Relationship between S. aureus and Branched-Chain Amino Acids Content in Composite Cow Milk

The early diagnosis of mastitis is an essential factor for the prompt detection of the animal for further actions. In fact, if not culled, infected cows must be segregated from the milking herd and milked last, or milked with separate milking units. Besides microbiological analysis, the somatic cell count (SCC) commonly used as predictor of intramammary infection, frequently lead to a misclassification of milk samples. To overcome these limitations, more specific biomarkers are continuously evaluated. The total amino acid content increases significantly in mastitic milk compared to normal milk. S. aureus requires branched-chain amino acids (BCAAs-isoleucine, leucine, and valine) for protein synthesis, branched-chain fatty acids synthesis, and environmental adaptation by responding to their availability via transcriptional regulators. The increase of BCAAs in composite milk has been postulated to be linked to mammary infection by S. aureus. The aim of this work is to demonstrate, by a direct ion-pairing reversed-phase method, based on the use of the evaporative light-scattering detector (IP-RP-HPLC-ELSD), applied to 65 composite cow milk samples, a correlation between the concentration of isoleucine and leucine, and S. aureus load. The correlation coefficient, r, was found to be 0.102 for SCC (p = 0.096), 0.622 for isoleucine (p < 0.0001), 0.586 for leucine (p < 0.0001), 0.013 for valine (p = 0.381), and 0.07 for tyrosine (p = 0.034), standing for a positive correlation between S. aureus and isoleucine and leucine concentration. The link between the content of BCAAs, isoleucine and leucine, and udder infection by S. aureus demonstrated with our study has an important clinical value for the rapid diagnosis of S. aureus mastitis in cows.

Epidemiological investigation of subclinical bovine mastitis in Algeria and molecular characterization of biofilm-forming Staphylococcus aureus

Thirty dairy farms were selected for this study; the first objective of our study was to investigate the prevalence of subclinical bovine mastitis (SCM) in Eastern Algeria, from 600 lactating cows, and to identify potential risk factors associated with the occurrence of bovine mastitis and bacteria isolation using logistic regression. The second objective was to evaluate biofilm formation capacity and detect biofilm-associated genes of S. aureus, isolated from SCM cases. Molecular typing was investigated by spa typing. The prevalence of mastitis at cow and quarter level was 37.66% (226/600) and 27.17% (555/2042), respectively. Stage of lactation, cow breed, milk production, and the study area were factors associated with SCM. In addition, the most frequent pathogens isolated from mastitic milk were coagulase-negative staphylococci (CNS), E. coli, and S. aureus. The study area was highly associated with SCM caused by S. aureus; cows from Setif province were 18 times more affected with SCM caused by S. aureus compared to cows from Batna province (OR = 18.6, 95%CI 2.038-171.2), but were less affected with SCM caused by CNS isolates (OR = 0.17, 95%CI 0.033-0.868). Moreover, cows with milk production less than 10 L per day increased (p < 0.05) the prevalence of mastitis caused by E. coli. All the S. aureus isolates had biofilm-forming ability, and 41.66% of isolates were positive for adhesion genes (icaA, icaD, fbnA, and clfA). This study, therefore, warrants the need for improving sanitary measures and strict hygienic measures, and presents the first insight into biofilm-forming ability of S. aureus strains causing mastitis in dairy herds in Algeria, which will help in tracking the evolution of epidemic strains responsible for causing bovine mastitis.

Bacteriological quality and safety of ready-to-consume milk and naturally fermented milk in Borana pastoral area, southern Ethiopia

Milk and milk products play an important role in the diet of pastoralists in Ethiopia. However, only few studies have been conducted on the microbial contamination of milk and milk products in pastoral areas. Therefore, the objective of the present study was to assess the hygiene and safety of ready-to-consume milk and traditionally produced fermented milk products (yogurt) in Borana. A total of 203 raw milk and milk product samples collected from different points along the milk production and handling chains were tested for Escherichia coli, E. coli O157:H7, and Staphylococcus aureus. E. coli was detected in 51.7% of the analyzed samples with a mean count of 2.5 logCFU/ml. The study revealed that 10.8% and 2.5% of the milk and dairy product samples harbor S. aureus and E. coli O157:H7, respectively. Detection of E. coli O157:H7 in ready-to-consume milk has potential health implications for consumers in an area where raw milk consumption is common. To our knowledge, this is the first report of the isolation of E. coli O157:H7 from milk in pastoral systems in Ethiopia.

Short communication: Characterization of enterotoxin-producing Staphylococcus aureus isolated from mastitic cows

Staphylococcus aureus is not only a common cause of bovine mastitis, but also an agent of food poisoning in humans. In an attempt to determine whether staphylococci causing bovine mastitis could also cause food poisoning, 60 isolates of presumed S. aureus were isolated in the period between March and August 2017 from 3,384 routine, composite, quarter milk samples of individual cows raised on 12 dairy farms in central Italy. Seventeen out of 60 isolates were confirmed as S. aureus after coagulase, thermonuclease, and biochemical tests. These isolates were analyzed by PCR for the presence of the nuc, sea, seb, sec, sed, and see genes. The positive isolates were nuc, 100% (17); sea, 35.29% (6); seb, 5.88% (1); sec, 5.88% (1); sed, 29.41% (5); and see, 47.06% (8). The isolates were also tested with 2 enzyme immunoassay diagnostic kits, one for the screening detection of the production of staphylococcal enterotoxins (SEA, SEB, SEC, SED, SEE) and one for the detection of specific enterotoxin produced by each isolate. Seven out of 17 (41.18%) were enterotoxin producers: 7 produced SEA (41.18%), 1 SEB (5.88%), 1 SEC (5.88%), 5 SED (29.41%), and 6 SEE (35.29%). To further characterize the isolates, they were analyzed by the Kirby Bauer test for susceptibility to 13 antimicrobials (ampicillin, ciprofloxacin, kanamycin, tetracycline, gentamicin, methicillin, nalidixic acid, erythromycin, amoxicillin/clavulanic acid, streptomycin, vancomycin, neomycin, and enrofloxacin), and we detected resistance to ampicillin (52.94%), nalidixic acid (70.59%), erythromycin (5.88%), and amoxicillin/clavulanic acid (17.65%). The isolates were sensitive to the main classes of antimicrobials used for the treatment of bovine subclinical mastitis. The presence of enterotoxin-producing isolates of S. aureus in bovine milk means that a temperature abuse or a breakdown in the thermal treatment of the milk could present a food safety risk, particularly if all enterotoxigenic isolates could potentially produce SEA in milk.

Bacteriological survey of bulk tank milk from dairy farms in Montero, Santa Cruz, Bolivia

Background and Aim:

Recently, bacterial surveys for mastitis-causing pathogens in bulk tank milk (BTM) have been conducted in several countries worldwide. However, no such surveys have been reported from Bolivia. Therefore, the present study aimed to estimate the prevalence of mastitis pathogens in BTM from dairy farms in Montero, Santa Cruz, Bolivia.

Materials and Methods:

Between July 2016 and August 2017, a total of 43 BTM samples were collected from 3264 cows to determine bulk tank somatic cell counts (BTSCC) and identify mastitis-causing bacteria. BTSCC was classified as follows: <100×10³, 100-500×10³, 500-1000×10³, and >1000×10³ cells/mL.

Results:

Mastitis-causing pathogens identified by agar medium cultures included Bacillus spp., coagulase-negative staphylococci (CNS), coliforms, Staphylococcus aureus (SA), streptococci, and other species. The proportions of BTSCC of <100×10³, 200-500×10³, 500-1000×10³, and >1000×10³ cells/ml were 0%, 37%, 51%, and 12%, respectively. The proportions of coliforms, streptococci, CNS, Bacillus spp., SA, and others detected in BTM were 33%, 30%, 16%, 7%, 2%, and 16%, respectively.

Conclusion:

Although the herd prevalence of contagious mastitis-causing pathogens, such as SA, in BTM was low, increased BTSCC were identified in Montero, Santa Cruz, Bolivia.

Analysis of milk-derived isolates of E. coli indicating drug resistance in central Ethiopia

Mastitis is one of the most important diseases in dairy cows throughout the world and is responsible for significant economic losses to the dairy industry. This study was performed to characterize the genetic basis of drug resistance in Escherichia coli isolated from cases of clinical and sub-clinical bovine mastitis. A total of 224 California mastitis test (CMT)-positive milk samples were collected from December 2015 to April 2016 to characterize the phenotypic and genetic basis of antimicrobial resistance in E. coli isolated from raw milk from dairy farms found in Burayu, Sebeta, and Holeta areas of Ethiopia. The prevalence of E. coli was 7.1% (16) and both phenotypic and molecular techniques were used to identify E. coli antimicrobial susceptibility trait. The most commonly observed phenotypic resistance was against ampicillin (68.7%), sulphamethazole-trimethoprim (50%), and streptomycin (25%). Multidrug resistance phenotypes were found in 11 of 16 (68.7%) of E. coli isolates. Tetracycline (tet (A)) and chloramphenicol (cml (A)) genes were the most predominant encoding resistance genes identified (50%) each, followed by gentamycin resistance encoding gene (aac (3)-IV) (37.5%). Overall, 11 (68.7%) of the isolates had multidrug resistance genes responsible to two or more classes of antibiotics. The most common pattern detected was cml (A) and tet (A) together 37.5% followed by aac (3)-IV and tet (A) 25%. The current study indicated that raw milk could be regarded as critical source of antibiotic-resistant pathogenic E. coli.