Pathogen-specific production losses in bovine mastitis

Reduction in long-term milk yields represents a notable share of the economic losses caused by bovine mastitis. Efficient, economic, and safe measures to prevent these losses require knowledge of the causal agent of the disease. The aim of this study was to investigate pathogen-specific impacts of mastitis on milk production of dairy cows. The materials consisted of milk and health recording data and microbiological diagnoses of mastitic quarter milk samples of 20,234 Finnish dairy cows during 2010, 2011, and 2012. The 6 most common udder pathogens were included in the study: Staphylococcus aureus, non-aureus staphylococci (NAS), Escherichia coli, Corynebacterium bovis, Streptococcus uberis, and Streptococcus dysgalactiae. We used a 2-level multilevel model to estimate curves for lactations with and without mastitis. The data on lactation periods to be compared were collected from the same cow. To enable comparison among lactations representing diverse parities, the estimated lactation curves were adjusted to describe the cow's third lactation. Mastitis caused by each pathogen resulted in milk production loss. The extent of the reduction depended on the pathogen, the timing of mastitis during lactation, and the type of mastitis (clinical vs. subclinical). The 2 most commonly detected pathogens were NAS and Staph. aureus. Escherichia coli clinical mastitis diagnosed before peak lactation caused the largest loss, 10.6% of the 305-d milk yield (3.5 kg/d). The corresponding loss for Staph. aureus mastitis was 7.1% (2.3 kg/d). In Staph. aureus mastitis diagnosed between 54 and 120 d in milk, the loss was 4.3% (1.4 kg/d). The loss was almost equal in both clinical and subclinical mastitis caused by Staph. aureus. Mastitis caused by Strep. uberis and Strep. dysgalactiae resulted in losses ranging from 3.7% (1.2 kg/d) to 6.6% (2.1 kg/d) depending on type and timing of mastitis. Clinical mastitis caused by the minor pathogens C. bovis and NAS also had a negative effect on milk production: 7.4% (2.4 kg/d) in C. bovis and 5.7% (1.8 kg/d) in NAS when both were diagnosed before peak lactation. In conclusion, minor pathogens should not be underestimated as a cause of milk yield reduction. On single dairy farms, control of E. coli mastitis would bring about a significant increase in milk production. Reducing Staph. aureus mastitis is the greatest challenge for the Finnish dairy sector.

Efficacy of 5-day parenteral versus intramammary benzylpenicillin for treatment of clinical mastitis caused by gram-positive bacteria susceptible to penicillin in vitro

The efficacy of parenteral (intramuscular) or intramammary (IMM) benzylpenicillin treatment for clinical mastitis caused by gram-positive bacteria susceptible to penicillin in vitro was investigated. Cows with clinical mastitis in 1 udder quarter were randomly placed into 2 treatment groups. The preliminary bacteriological diagnosis of intramammary infection (IMI) was based on on-farm culturing, and the bacteriological diagnoses were later confirmed by a quantitative PCR assay. Clinical mastitis caused by gram-positive bacteria susceptible to benzylpenicillin was treated with penicillin via either the parenteral route (20mg/kg) or IMM route (600mg) once per day for 5d. The outcome of the treatment was evaluated 3 to 4wk after the onset of the treatment. The affected quarter was examined to assess the clinical cure, and milk samples were collected from the affected quarter to determine the bacteriological cure and milk N-acetyl-β-d-glucosaminidase activity. The survival and the composite milk somatic cell counts of the treated cows were followed up for 6 and 3mo after treatment, respectively. A total of 140 cows with clinical mastitis were included in the study, 61 being treated with benzylpenicillin parenterally and 79 via the IMM route. From all quarters treated, 108 of 140 (77.1%) were cured clinically and 77 of 140 (55.0%) were cured bacteriologically. The route of treatment did not significantly affect the outcome of the treatment; 80.3% of the quarters with parenteral treatment and 74.7% of the quarters with IMM treatment showed a clinical cure, and 54.1 and 55.7% a bacteriological cure, respectively. The milk N-acetyl-β-d-glucosaminidase activity was significantly lower in the quarters with a clinical or bacteriological cure than in the quarters with no cure. The 6-mo survival and the proportion of cows with composite milk somatic cell counts <200,000/mL among the treated cows during the 3-mo follow-up period did not significantly differ between the treatment groups. In conclusion, the outcome of either parenteral or IMM benzylpenicillin treatment of clinical mastitis caused by penicillin-susceptible bacteria was similar.

Treatment for bovine Escherichia coli mastitis - an evidence-based approach

Bovine mastitis caused by Escherichia coli can range from being a subclinical infection of the mammary gland to a severe systemic disease. Cow-dependent factors such as lactation stage and age affect the severity of coliform mastitis. Evidence for the efficacy of antimicrobial treatment for E. coli mastitis is very limited. Antimicrobial resistance is generally not a limiting factor for treatment, but it should be monitored to detect changes in resistance profiles. The only antimicrobials for which there is some scientific evidence of beneficial effects in the treatment for E. coli mastitis are fluoroquinolones and cephalosporins. Both are critically important drugs, the use of which in animals destined for food should be limited to specific indications and should be based on bacteriological diagnosis. The suggested routine protocol in dairy herds could target the primary antimicrobial treatment for mastitis, specifically infections caused by gram-positive bacteria. In E. coli mastitis with mild to moderate clinical signs, a non-antimicrobial approach (anti-inflammatory treatment, frequent milking and fluid therapy) should be the first option. In cases of severe E. coli mastitis, parenteral administration of fluoroquinolones, or third- or fourth-generation cephalosporins, is recommended due to the risk of unlimited growth of bacteria in the mammary gland and ensuing bacteremia. Evidence for the efficacy of intramammary-administered antimicrobial treatment for E. coli mastitis is so limited that it cannot be recommended. Nonsteroidal anti-inflammatory drugs have documented the efficacy in the treatment for E. coli mastitis and are recommended for supportive treatment for clinical mastitis.

Costs of clinical mastitis with special reference to premature culling

Bovine mastitis is an economic and a welfare problem on dairy farms. The objective of this study was to estimate the costs of clinical mastitis (CM), having a special focus on the cost variation related to culling decisions. A dynamic optimization model was developed to determine an optimal replacement time of a mastitic cow and to estimate the costs of CM, taking into account the risk of premature culling and the uncertainty in CM prevalence. Six lactations were analyzed at monthly periods for Ayrshire and Holstein-Friesian breeds. The estimates reflect Finnish production conditions where mastitis is treated only by veterinarians. Biological parameters of the model were adapted from the literature and the Finnish dairy herd health recording system. Field data were used to produce the risk parameters of culling due to mastitis on commercial dairy farms. The model recommended treating the cows with CM and keeping them in most cases until their fifth lactation. A cheaper (-20%) heifer transferred the optimum to the previous lactation and a more expensive (+20%) heifer to the following lactation. Conditional on optimal replacements, the average cost of CM of an Ayrshire (Holstein-Friesian costs in parentheses) cow was €485 (€458), varying from €209 (€112) to €1,006 (€946). The costs were at the highest when the occurrence of CM was at a top yield phase. In the scenario where the risk of culling due to mastitis was included in the model, the average cost of CM was €596 (€623). Disposing of a young cow at the end of her first lactation month caused the highest costs. The costs converted to figures per cow-year were €121 (€147) with optimal cullings and €155 (€191) in the current Finnish conditions. Thus, the increase in the costs of CM due to premature cullings was 28% (30%.) The main cost sources were long-term production losses regardless of the culling decisions. Premature culling formed 20% (23%) of the total costs. To decrease the costs of CM, more emphasis should be given to hidden costs, especially the high cost of premature culling should be underlined.

Invited review: udder health of dairy cows in automatic milking

Automatic milking (AM) is increasing in modern dairy farming, and over 8,000 farms worldwide currently use this technology. Automatic milking system is designed to replace conventional milking managed by a milker in a milking parlor or in tie stalls. Cows are generally milked more frequently in AM than in conventional milking, and milking is quarter-based instead of udder-based. Despite improvements in the milking process and often building of a new barn before the introduction of AM, udder health of the cows has not improved; on the contrary, problems may appear following conversion from conventional milking to AM. This review focuses on udder health of dairy cows in AM, and we discuss several aspects of cow and milking management in AM associated with udder health. Finally, adequate management methods in AM are suggested. According to several studies comparing udder health between automatic and conventional milking or comparing udder health before and after the introduction of automatic milking in the same herds, udder health has deteriorated during the first year or more after the introduction of AM. Automatic detection of subclinical and clinical mastitis and cleaning the teats before milking are challenges of AM. Failures in mastitis detection and milking hygiene pose a risk for udder health. These risk factors can partly be controlled by management actions taken by the farmer, but AM also needs further technical development. To maintain good udder health in AM, it is imperative that the barn is properly designed to keep the cows clean and the cow traffic flowing. Milking frequency must be maintained for every cow according to its stage of lactation and milk production. Careful observation of the cows and knowledge of how to use all data gathered from the system are also important. "Automatic" does not mean that the role of a competent herdsman is in any way diminished.

Treatment of mastitis during lactation

Treatment of mastitis should be based on bacteriological diagnosis and take national and international guidelines on prudent use of antimicrobials into account. In acute mastitis, where bacteriological diagnosis is not available, treatment should be initiated based on herd data and personal experience. Rapid bacteriological diagnosis would facilitate the proper selection of the antimicrobial. Treating subclinical mastitis with antimicrobials during lactation is seldom economical, because of high treatment costs and generally poor efficacy. All mastitis treatment should be evidence-based, i.e., the efficacy of each product and treatment length should be demonstrated by scientific studies. Use of on-farm written protocols for mastitis treatment promotes a judicious use of antimicrobials and reduces the use of antimicrobials.

Virulence genes of bovine Staphylococcus aureus from persistent and nonpersistent intramammary infections with different clinical characteristics

AIMS

To screen putative virulence genes in Staphylococcus aureus causing persistent and nonpersistent bovine intramammary infections (IMI) with different clinical characteristics. To examine, whether a possible relationship exists between genetic profile and infection persistence, clinical signs of infection, clonal type determined by pulsed-field gel electrophoresis (PFGE), and antimicrobial resistance.

METHODS AND RESULTS

One-hundred and sixty-one S. aureus isolates derived from bovine IMI, consisting of 17 different PFGE types, were screened by conventional and multiplex-polymerase chain reaction (PCR) for 24 virulence genes for haemolysins (hla-hlg), leukocidins (lukED, lukM), exfoliative toxins (eta, etb), enterotoxins (sea-seo, seu), toxic-shock syndrome toxin (tst), and genes encoding penicillin (blaZ) and methicillin resistance (mecA). The majority of S. aureus isolated at the onset of mastitis carried haemolysin genes (76.7-97.4%), lukED (96.6%), and at least one gene for pyrogenic toxin superantigen (PTSAg) (69.0%). Strains carrying PTSAg-encoding genes were more common among predominant PFGE types and in persistent IMI. Strains concomitantly possessing sed, sej, and blaZ, putatively plasmid-encoded, were typically found in connection with persistent IMI.

CONCLUSIONS

Our results suggest that certain genetic elements are over-representative in S. aureus isolates especially from persistent bovine mastitis. This phenomenon seems to be in connection with clonal type and is often concomitant with penicillin resistance.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study to investigate associations between a large number of bacterial factors and outcome of S. aureus mastitis. The finding that widespread clonal types of S. aureus causing bovine mastitis of low treatment response may harbour characteristic genes could be improved for strain-specific diagnostic purposes.

Bovine Intramammary Infections Caused by Coagulase-Negative Staphylococci May Persist Throughout Lactation According to Amplified Fragment Length Polymorphism-Based Analysis

Persistence of coagulase-negative staphylococci (CNS) in intramammary infections during lactation was studied in a research dairy herd of University of Helsinki. Milk samples from 328 udder quarters of 82 dairy cows (30 primiparous, 52 multiparous) were collected 2 wk before calving, at calving, and every 4 wk thereafter until the end of lactation or until the cow left the herd. The CNS isolated from the milk samples were analyzed with the API Staph ID 32 (bioMérieux, Marcy l'Etoile, France) test (API) and genotyped using amplified fragment length polymorphism (AFLP) analysis. The AFLP patterns were used for similarity analysis between CNS isolates and for species identification. For the latter, AFLP patterns of CNS isolates and staphylococcal type strains were used as operational taxonomic units in numerical analysis. In addition, the somatic cell count (SCC) of the milk samples was measured during lactation. A CNS infection was considered persistent when isolates originating from the same quarter had identical AFLP patterns on at least 3 consecutive samplings. In total, 63 CNS infections were detected during lactation in 30 and 33 quarters in the first and later lactations, respectively. Twenty-nine of these infections persisted and 34 were transient. Most of the persistent infections lasted until the end of lactation. In 57 quarters, CNS infection was detected before calving, at calving, or both, but only half of these quarters were infected by CNS during subsequent lactation. The geometric mean of SCC in quarters during persistent CNS infection was 657,600 cells/mL, and the mean of SCC in quarters with transient CNS infection was 619,100 cells/mL. The median of SCC in quarters during persistent CNS infection was 355,400 cells/mL, and the median of SCC in quarters with transient CNS infection was 133,500 cells/mL. According to both the API test and AFLP results, Staphylococcus chromogenes and Staphylococcus simulans were the CNS species isolated most often. Identification results for API and AFLP corresponded in 71.9% of the isolates.

Association of bovine respiratory disease with clinical status and acute phase proteins in calves

Eighty-four calves with respiratory disease from 18 herds in different parts of Finland were chosen for a study evaluating the capacity of different respiratory pathogens to cause changes in different acute phase protein concentrations, white blood cell (WBC) count and clinical signs. The selected acute phase proteins were fibrinogen, haptoglobin, serum amyloid-A, lipopolysaccharide binding protein and alpha1-acid glycoprotein. From each calf, a paired blood sample was obtained for serological studies of bovine parainfluenza virus-3, bovine respiratory syncytial virus, bovine coronavirus, bovine adenovirus-3 and bovine adenovirus-7. Tracheobronchial lavage was performed to detect bacteria and mycoplasma. Isolation of Pasteurella multocida was associated with increased concentrations of all tested acute phase proteins. For other pathogens, no significant relationships were observed. No association was present between viral or bacterial findings and WBC count.

Transgenic cows that produce recombinant human lactoferrin in milk are not protected from experimental Escherichia coli intramammary infection

This is the first study describing an experimental mastitis model using transgenic cows expressing recombinant human lactoferrin (rhLf) in their milk. The aim of the study was to investigate the concentrations in milk and protective effects of bovine and recombinant human lactoferrin in experimental Escherichia coli mastitis. Experimental intramammary infection was induced in one udder quarter of seven first-lactating rhLf-transgenic cows and six normal cows, using an E. coli strain isolated from cows with clinical mastitis and known to be susceptible to Lf in vitro. Clinical signs were recorded during the experimental period, concentrations of human and bovine Lf and indicators of inflammation and bacterial counts were determined for milk, and concentrations of acute-phase proteins and tumor necrosis factor alpha were determined for sera and milk. Serum cortisol and blood hematological and biochemical parameters were also determined. Expression levels of rhLf in the milk of transgenic cows remained constant throughout the experiment (mean, 2.9 mg/ml). The high Lf concentrations in the milk of transgenic cows did not protect them from intramammary infection. All cows became infected and developed clinical mastitis. The rhLf-transgenic cows showed milder systemic signs and lower serum cortisol and haptoglobin concentrations than did controls. This may be explained by lipopolysaccharide-neutralizing and immunomodulatory effects of the high Lf concentrations in their milk. However, Lf does not seem to be a very efficient protein for genetic engineering to enhance the mastitis resistance of dairy cows.

Revision of prolapsed feeding gastrostomy with a modified Janeway 'gastric tube'

After creation of open or percutaneous endoscopic gastrostomy, gastric prolapse and leak of gastric contents may cause serious skin rash and infection which are often difficult to treat. We present four patients in whom these problems were solved with gastrostomy revision by a modified Janeway 'gastric tube' technique. The patients were aged 7 months and 7, 10 and 16 years at the time of the revision. The underlying conditions were hypoxic encephalopathy with epilepsy, infantile spasm and epilepsy with arthrogryposis, dystonic tetraplegy, and total colon aganglionosis. All patients had gastrostomy prolapse with peristomal skin rash and cellulitis. Prior to modified Janeway revision, the four patients had undergone a total of 16 failed attempts to cure the prolapse. At the operation, the previous gastrostomy was detached and closed. A longitudinal gastric tube of 6 cm was created along the greater curvature with a GIA stapler and brought through the abdominal wall leaving 3-5 cm of free intra-abdominal gastric tube. A balloon catheter was left for 6 weeks, and replaced with a long Mickey tube according to patient's or caretaker's preference. There were no surgical complications. Hospitalisation after revision was median 6 (range 4-11) days. Six weeks after the revision, prolapse, leak and peristomal infections were cured in all patients, and feeding through the gastrostomy presented no problems. One patient underwent minor excision of excess stomal mucosa. Two patients opted for Mickey tube, two for a feeding catheter. A median of 9 (6-16) months after the revision, all patients have a functioning gastrostomy without prolapse or leak. Modified Janeway 'gastric tube' revision is feasible and, within short to medium term follow-up, controls efficiently gastrostomy prolapse and leak.

Visual Detection of Technical Success and Effectiveness of Teat Cleaning in Two Automatic Milking Systems

Technical success and effectiveness of teat cleaning and the management factors associated with them were evaluated in 9 automatic milking herds. In total, 616 teats cleaned with a cleaning cup and 716 teats cleaned with rotating brushes were included. Technical success and the effectiveness of teat cleaning, including the location and nature of the dirt, were evaluated visually. On average, 79.9% of teat cleanings with a cleaning cup, and 85.0% of those cleaned with brushes succeeded technically; that is, the teat was correctly positioned in the cleaning device throughout the whole cleaning process. The difference between use of teat cups and brushes was significant. However, because technical success of teat cleaning is strongly dependent on herd characteristics, these results should be interpreted with caution. Factors associated with the technical success of teat cleaning with a cleaning cup were herd, days in milk, behavior of the cow, teat color, and teat location. For rotating brushes, behavior of the cow, teat location, udder and teat structure, and days in milk were associated with technical success. Excessive udder hair and technical failure of the automatic milking machine also caused a few technically unsuccessful teat cleanings with a cleaning cup. Teats with technically successful teat cleanings were evaluated for the effectiveness of teat cleaning. From originally dirty teats, the cleaning cup had a significant advantage over the brushes in the percentage of teats that became clean or almost clean during the cleaning process (79.8 vs. 72.9%). Teat orifices were least effectively cleaned compared with the teat barrel and apex. Bedding material (peat, sawdust, or straw) on the teat was cleaned almost completely. Factors associated with the effectiveness of teat cleaning were teat cleanliness before cleaning, herd, teat cleaning method, and teat condition. The variation among herds indicates the likelihood that herd management factors can be adjusted to improve milking hygiene. There is also a need to improve the precision and effectiveness of the teat cleaning mechanisms of automatic milking systems.

Feeding-unrelated factors influencing the plasma leptin level in ruminants

The triglyceride content of lipid depots associated with the current feeding level is the primary determinant of leptin gene expression and the circulating leptin level. In laboratory rodents and primates the plasma leptin is influenced also by the age, gender and physiological status (puberty, pregnancy, lactation, postpartum period), and by the health condition such as sepsis due to Gram-negative (GN) bacteria. Some pathologic conditions with intensive cytokine release evoke an increase in plasma leptin, which is thought to depress the subsequent feed intake. However, the effect of these secondary factors may be species-dependent, with still unknown clinical relevance in ruminants. In our ovine and bovine models plasma leptin increased after castration and dexamethasone treatment, decreased after experimental administration of synthetic androgens in castrated rams, but remained unchanged throughout the ovarian cycle and after ovariectomy. The circulating leptin level increased temporarily during synthetic progestin (fluorogestone) treatment in ewes, but similar changes were not seen in progesterone-supplemented ewes and norgestomet-treated cows. In a second trial on dairy cows we wanted to study whether elevated plasma leptin levels are induced by experimental endotoxin mastitis, or by natural outbreak of GN mastitis and puerperal metritis. Experimental endotoxin mastitis resulted in some-hour elevation in cortisol and insulin, with a simultaneous decrease in IGF-I and thyroid hormones. In the first 14 days of lactation GN mastitis induced the same endocrine alterations as the experimental endotoxin challenge, but in natural cases these changes varied within a wider range, and were more protracted and robust. Cows with puerperal metritis had more obvious catabolic changes in the early weeks of lactation, than their healthy counterparts. However, both mastitis and puerperal metritis failed to increase the circulating leptin level, showing that in cows the plasma leptin is not responsible for the anorexia associated with these inflammatory diseases.

Bacterial genotype affects the manifestation and persistence of bovine Staphylococcus aureus intramammary infection

Two-hundred seventeen Staphylococcus aureus isolates from 116 dairy cows with intramammary infections were analyzed by pulsed-field gel electrophoresis to study the association between symptom severity, persistence of infection, and bacterial genotype. Among five main genotypes infecting 90% of the cows, one was associated with severe clinical symptoms but reduced persistence.

Comparison of phenotypic and genotypic detection of penicillin G resistance of Staphylococcus aureus isolated from bovine intramammary infection

Resistance of Staphylococcus aureus to penicillin G is common among isolates from bovine mastitis. We determined phenotypic resistance to penicillin G for 151 S. aureus isolates derived from dairy cows with intramammary infection by two methods. The methods were determination of minimum inhibitory concentration (MIC) by a standard agar dilution technique and direct testing of beta-lactamase production using a chromogenic cephalosporin, nitrocefin. The results from these tests were compared with the presence of the beta-lactamase (blaZ) gene in the isolates, which was detected by polymerase chain reaction (PCR). Testing beta-lactamase production with nitrocefin was more predictive for the presence of the blaZ gene than the agar dilution method and the results of the former agreed highly with the presence of the blaZ gene in the isolates. In contrast, the resistance breakpoint generally used in the agar dilution method may be too high for prediction of penicillin resistance in S. aureus isolates with borderline MICs. Using this method, 40% of the isolates possessing the blaZ gene were classified as susceptible; however, majority of these isolates produced beta-lactamase when tested with nitrocefin.

The efficacy of bovine lactoferrin in the treatment of cows with experimentally induced Escherichia coli mastitis

The effect of bovine lactoferrin (Lf) was studied in experimental Escherichia coli mastitis, using enrofloxacin as a comparator. Mastitis was induced in six clinically healthy primiparous dairy cows by infusing 1500 colony-forming units of E. coli into a single udder quarter. The challenge was repeated into a contralateral quarter of the same cows 3 weeks later. At the first challenge, three cows were treated with 1.5 g of bovine lactoferrin intramammarily three times (12, 20 and 36 h postchallenge, PC), and the other three cows received 5 mg/kg of enrofloxacin (Baytril) parenterally (12, 36 and 60 h PC). Flunixin meglumine (2.2 mg/kg) was administered to all cows twice at 24-h intervals. During the second challenge, the treatments for the two groups were reversed. Intramammary challenge with E. coli produced clinical mastitis in all cows, but the severity of the disease varied markedly. No statistically significant differences between treatment groups were observed in clinical signs such as rectal temperature, rumen motility and general attitude. Milk somatic cell count, daily milk yield and bacterial counts in cows treated with Lf and those receiving enrofloxacin also did not differ significantly. However, a trend for a more rapid elimination of bacteria was seen in the cows treated with enrofloxacin. Milk NAGase activity also decreased significantly faster in the group treated with enrofloxacin. The concentration of lipopolysaccharide in milk compared with the number of bacteria was significantly lower in Lf than in enrofloxacin-treated cows (20 h PC).

ITIH4 (inter-alpha-trypsin inhibitor heavy chain 4) is a new acute-phase protein isolated from cattle during experimental infection

We have isolated from calf serum a protein with an apparent M(r) of 120,000. The protein was detected by using antibodies against major acute-phase protein in pigs with acute inflammation. The amino acid sequence of an internal fragment revealed that this protein is the bovine counterpart of ITIH4, the heavy chain 4 of the inter-alpha-trypsin inhibitor family. The response of this protein in the sera was determined for animals during experimental bacterial and viral infections. In the bacterial model, animals were inoculated with a mixture of Actinomyces pyogenes, Fusobacterium necrophorum, and Peptostreptococcus indolicus to induce an acute-phase reaction. All animals developed moderate to severe clinical mastitis and exhibited remarkable increases in ITIH4 concentration in serum (from 3 to 12 times the initial values, peaking at 48 to 72 h after infection) that correlated with the severity of the disease. Animals with experimental infections with bovine respiratory syncytial virus (BRSV) also showed increases in ITIH4 concentration (from two- to fivefold), which peaked at around 7 to 8 days after inoculation. Generally, no response was seen after a second infection of the same animals with the virus. Because of the significant induction of the protein in the animals in the mastitis and BRSV infection models, we can conclude that ITIH4 is a new positive acute-phase protein in cattle.

Bovine Mastitis in Finland 2001—Prevalence, Distribution of Bacteria, and Antimicrobial Resistance

A nationwide survey was conducted in Finland to estimate prevalence of bovine mastitis, distribution of mastitis pathogens, and in vitro antimicrobial susceptibility of different mastitis pathogens. In total, 12,661 quarter milk samples were collected from 3282 dairy cows at 216 farms. These were randomly selected from a database covering all Finnish dairy farms. Quarter milk samples collected by the dairy advisors were submitted for somatic cell counting, bacteriological examination, and testing for antimicrobial susceptibility. If the milk SCC of a cow or of a quarter exceeded 300,000/mL, the cow was defined as having mastitis. The results were compared with those of a previous survey done in 1995. The prevalence of mastitis continued to decrease from 38% in 1995 to 31% in 2001. Compared with the study from 1995, the number of quarters with bacterial growth in 2001 increased significantly from 21.0 to 33.5%. This mainly resulted from increased prevalence of Corynebacterium bovis. Coagulase-negative staphylococci remained the most common bacterial group, comprising almost one-half of the pathogens isolated, whereas the relative number of Staphylococcus aureus isolations decreased from the time of the previous study. According to in vitro antimicrobial susceptibility testing, the enterococci demonstrated the highest level of resistance. Compared with the other Nordic countries, penicillin resistance among the staphylococci was still at a relatively high level in Finland (52.1 and 32.0% for Staphylococcus aureus and coagulase-negative staphylococci, respectively). Streptococci isolated from mastitis were very susceptible to beta-lactam antibiotics, as also found in the previous survey in 1995.

Antibacterial effect of bovine lactoferrin against udder pathogens

The antibacterial effect of lactoferrin (Lf) was tested on isolates of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and coagulase-negative staphylococci (CNS) as well as on Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae), originally isolated from bovine mastitis. Concentrations of Lf used were 0.67 mg/ml, 1.67 mg/ml, and 2.67 mg/ml. Growth of udder pathogens was monitored by turbidometry either in broth culture or in whey prepared from normal milk. We focused on 3 different growth variables: lag time, slope, and maximum absorbance of bacterial growth curves. Growth inhibition was seen in the broth but hardly at all in whey. The isolates of E. coli and CNS did not grow sufficiently well in whey to draw any conclusions. The most effective inhibitory activity of Lf was seen against E. coli and P. aeruginosa. All 5 E. coli isolates had similar growth patterns. Inhibition of growth by Lf was concentration-dependent. The concentration of 0.67 mg/ml in broth and whey was generally too low for a significant inhibitory effect.

Efficacy of targeted 5-day combined parenteral and intramammary treatment of clinical mastitis caused by penicillin-susceptible or penicillin-resistant Staphylococcus aureus

Combined parenteral and intramammary treatment of mastitis caused by Staphylococcus aureus was compared to parenteral treatment only. Cows with clinical mastitis (166 mastitic quarters) caused by S. aureus treated by veterinarians of the Ambulatory Clinic of the Faculty of Veterinary Medicine during routine farm calls were included. Treatment was based on in vitro susceptibility testing of the bacterial isolate. Procaine penicillin G (86 cases due to beta-lactamase negative strains) or amoxycillin-clavulanic acid (24 cases due to beta-lactamase positive strains) was administered parenterally and intramammarily for 5 days. Efficacy of treatments was assessed 2 and 4 weeks later by physical examination, bacteriological culture, determination of CMT, somatic cell count and NAGase activity in milk. Quarters with growth of S. aureus in at least one post-treatment sample were classified as non-cured. As controls we used 41 clinical mastitis cases caused by penicillin-susceptible S. aureus isolates treated with procaine penicillin G parenterally for 5 days and 15 cases due to penicillin-resistant isolates treated with spiramycin parenterally for 5 days from the same practice area. Bacteriological cure rate after the combination treatment was 75.6% for quarters infected with penicillin-susceptible S. aureus isolates, and 29.2% for quarters infected with penicillin-resistant isolates. Cure rate for quarters treated only parenterally with procaine penicillin G was 56.1% and that for quarters treated with spiramycin 33.3%. The difference in cure rates between mastitis due to penicillin-susceptible and penicillin-resistant S. aureus was highly significant. Combined treatment was superior over systemic treatment only in the beta-lactamase negative group.

Lactoferrin and citrate concentrations at drying-off and during early mammary involution of dairy cows

Quarter milk samples were taken from 48 clinically healthy, pregnant Finnish Ayrshire and Friesian dairy cows at the last milking before drying-off, and 2 and 6 days later to determine the lactoferrin and citrate concentrations in the udder secretion. The mean lactoferrin concentration in the milk increased from 5.29 mg ml(-1) on the last day of drying-off process to 8.09 and 11.26 mg ml(-1), 2 and 6 days later, respectively. Citrate concentration decreased from 1.85 mg ml(-1) to 1.54 and 1.09 mg ml(-1), respectively. Median molar ratio (citrate to native-Lf) decreased from 153 to 86 and further to 44. Lf and citrate concentrations in milk varied greatly among cows. Sampling time had a statistically significant effect on lactoferrin and citrate concentrations in milk while the breed and the parity of the cows had no effect on either of these variables.

In Vitro Antimicrobial Susceptibility of Escherichia coli Isolates from Clinical Bovine Mastitis in Finland and Israel

Minimal inhibition concentration (MIC) values of 100 Finnish and 100 Israeli Escherichia coli isolated from clinical bovine mastitis were determined for ampicillin, cephalexin, ceftazidime, dihydrostreptomycin, gentamicin, tetracycline, trimethoprim-sulfadiazine, and ciprofloxacin by an agar dilution method. The in vitro antimicrobial susceptibility of the E. coli isolates was high; only 27% showed resistance to one or more tested antimicrobial agents. Fifteen percent of the Israeli isolates and 14% of the Finnish isolates were resistant to tetracycline, 3 and 16% to cephalexin, 10 and 7% to ampicillin, 13 and 9% to dihydrostreptomycin, and 4 and 2% to trimethoprim-sulfadiazine. No gentamicin-, ceftazidime-, or ciprofloxacin-resistant isolates were detected. Eleven percent of all the isolates were resistant to two or more antimicrobial agents. Tetracycline was most often associated with multiresistant patterns. Most of the multiresistant isolates had very high MIC values, whereas most of those that were resistant to only one tested antibiotic had MIC values close to the susceptibility breakpoint. Antimicrobial resistance appeared to pose no problem in E. coli isolated from mastitic milk of both countries. This is probably due to the controlled use of antimicrobial agents in the treatment of dairy herds. Some differences were present in the resistance patterns, which may reflect the different use of antimicrobial agents in these two countries.

Effect of intramammary Escherichia coli endotoxin in early- vs. late-lactating dairy cows

We investigated the differences in the effect of intramammarily infused endotoxin for cows in early (EL) and late (LL) lactation. In this crossover study, nine cows were challenged twice with 100 microg of intramammarily infused Escherichia coli 0111:B4 LPS, each cow serving its own control. Systemic and local signs were recorded throughout the experiment to assess the severity of each cow's response. Daily milk yield and indicators of inflammation in blood and milk were also recorded. The response was significantly more severe in the EL period. Before the challenge, milk yield and serum free fatty acid concentration were higher and serum urea concentration lower in EL compared with LL cows. No significant differences were present in other parameters. After the challenge, milk SCC and leukocyte function, measured as chemiluminescence, increased, more markedly in EL. Blood neutrophil content varied from neutropenia to neutrophilia. Simultaneously with neutropenia, the function of neutrophils increased in LL but decreased in EL. Serum cortisol peaked 4 h after challenge in both groups. In conclusion, endotoxin challenge resulted in more severe response in EL. During that time cows also had impaired neutrophil function postchallenge.

Efficacy of intramammary treatment with procaine penicillin G vs. procaine penicillin G plus neomycin in bovine clinical mastitis caused by penicillin-susceptible, gram-positive bacteria--a double blind field study

The efficacy of intramammary treatments containing procaine penicillin G alone (treatment A) or a combination of procaine penicillin G and neomycin (treatment B) was compared in treating clinical bovine mastitis caused by gram-positive bacteria susceptible in vitro to penicillin G. Both treatments were supplemented with a single intramuscular injection of procaine penicillin G on the first day of treatment. The study was carried out using a double blind design on commercial dairy farms in Southern Finland. A total of 56 quarters were treated with treatment A and 61 with treatment B. The cure rates for both treatments were equal, which suggests that the use of the penicillin G-aminoglycoside combination does not increase the efficacy of the treatment over that achieved by using penicillin G alone in bovine clinical mastitis caused by penicillin-susceptible, gram-positive bacteria.

Efficacy and pharmacokinetics of enrofloxacin and flunixin meglumine for treatment of cows with experimentally induced Escherichia coli mastitis

The efficacy of flunixin alone and together with enrofloxacin in treatment of experimental Escherichia coli mastitis was compared using six cows. The cross-over study design was used. Pharmacokinetics of flunixin and enrofloxacin were also studied in these diseased cows. The response of each cow was similar after the first and second challenge and the individual reaction seemed to explain the severity of clinical signs. The most important predictive factor for outcome of E. coli mastitis was a heavy drop in milk yield. Treatment with enrofloxacin and flunixin enhanced elimination of bacteria, but the difference from those receiving flunixin alone was not significant. Two cows, which had received no antimicrobial treatment (Group 1), were killed on day 4 postchallenge. One cow was killed after the first and the other after the second challenge. Cows receiving combination therapy produced 0.9 L more milk per day during the study period than cows which had only received flunixin (P < 0.05). Based on our findings, antimicrobial treatment might be beneficial in the treatment of high-yielding cows in early lactation. The absorption of enrofloxacin was delayed after subcutaneous administration, the mean apparent elimination half-life being about 23 h, whereas after i.v. administration elimination t(1/2) was only 1.5 h. The majority of the antimicrobial activity in milk originated from the active metabolite, ciprofloxacin, which could be measured throughout the 120-h follow-up period after the last subcutaneous administration. No differences were present in the pharmacokinetic parameters of flunixin between treatment groups: mean elimination half-life was 5.7-6.2 h, volume of distribution 0.43-0.49 L/kg and clearance 0.13-0.14 L h/kg. No flunixin or merely traces were detected in milk: one of the three cows had a concentration of 0.019 mg/L 8 h after administration.

New strategies to prevent mastitis

Bovine mastitis remains as the disease causing the biggest economic losses to the dairy industry, despite the intensive research and prevention measures at herd level carried out for decades. Antibiotics are widely used to combat mastitis, but focus should be shifted from treatment to more economical and efficient prevention. The bacteriological aetiology of mastitis has changed from contagious to environmental pathogens, which has reduced the efficacy of the traditional mastitis control strategies. Considerable progress in the understanding of epidemiology, immunology, diagnostics and pathogenesis of mastitis has been made. The modern molecular biological methods offer good possibilities for the research of the epidemiological and virulence aspects of bacteria, which may help in building-up specific mastitis control strategies for dairy herds. Studies on the host response and relationship between somatic cell count and susceptibility to mastitis offer tools for genetic improvement of dairy cows. Biotechnological approaches for mastitis prevention are in the developmental stage, but many problems are associated, e.g. with vaccination of dairy cows against mastitis. Different methods of immunomodulation for the prevention of mastitis have shown promise in experimental trials, but the evidence is not yet enough to support commercial applications. Improving nutrition, housing and environment of dairy cattle are still crucial in the prevention of mastitis, especially during the most susceptible period after parturition. New milking techniques including robotic milking may provide better possibility for proper milking and improved udder health. Mastitis control should be part of the herd health programme in the dairy herds. In this paper, results from recent research and proposals for new prevention strategies in the field of mastitis are reviewed.

Disposition kinetics of lactoferrin in milk after intramammary administration

Disposition kinetics of lactoferrin (Lf) purified from cheese whey was studied in the milk of Finnish Ayrshire cows after intramammary administration of 1 g of Lf into one udder quarter. Intramammary administration of 1 g of Lf increased Lf concentration in milk for several hours. Mean elimination half-life of Lf was 2.2 h and a mean maximum concentration of 6.3 g/L was reached between 1 and 4 h. After 8 h of administration, Lf concentrations in milk decreased to almost the same level as before the infusion. Forty-eight hours postinfusion, the mean Lf concentration was again higher than in the milk samples taken before the infusion of Lf, being on average 1.5 g/L. Lactoferrin caused some local tissue irritation in the udder quarter. Severity of the irritation reactions varied between cows. The udder quarters of primiparous cows reacted faster than those of multiparous cows, but irritation reactions decreased more rapidly in the older cows than in primiparous cows. The cows had no general signs such as fever or anorexia. The somatic cell count returned to baseline level 4 days after the administration.

Virulence factors of Escherichia coli isolated from bovine clinical mastitis

Escherichia coli isolates from bovine mastitis were examined for a selection of virulence factors. The strains originated from Finland and Israel, which have differences in the proportion of mastitis caused by E. coli, clinical pictures of coliform mastitis, environmental conditions and herd management. The genes of nine virulence factors were detected by polymerase chain reaction. Presence of K1 and K5 capsules was assessed by use of specific bacteriophages. Serum resistance was tested by a turbidimetric assay. Out of 160 Finnish isolates, 37% had traT, 14% cnf2, 8% cnf1, 11% aer, 9% f17, 8% sfa, 7% pap, 1% afa8D and 1% afa8E. Out of 113 Israeli isolates, 41% had traT, 4% aer, 3% cnf2, 1% cnf1, 1% sfa and 1% f17. Some of the genes were distributed among two major pathotype groups, with either f17 family or sfa, pap and cnf1 as major determinants. Genes for F17a, CS31A, Afa7D and Afa7E were not detected. Altogether 49% of Finnish and 42% of Israeli isolates had at least one virulence gene, but genes other than traT were present in only 24% of Finnish and 5% of Israeli isolates. Serum resistance was more common among Finnish (94/160) than Israeli isolates (19/113). K1 and K5 capsules were not detected.

Characterization of hemolytic activity of Staphylococcus aureus strains isolated from bovine mastitic milk

Beta (beta) and delta (delta)-hemolysin of Staphylococcus aureus strains were cultured in vitro in milk lactoserum (whey) prepared from both healthy and mastitis bovine milk. Production of beta- and delta-hemolysins were detected in 12 out of 50 strains studied. The association between N-acetyl-beta-D-glucosaminidase (NAGase) activity, plasmin activity (PL) and trypsin inhibitory capacity (TIC), known as inflammatory indicators for mastitis, and hemolytic activity were also studied. Mastitic milk decreased directly the lytic effect of both beta-and delta-hemolysins of S. aureus on hemolytical blood agar plates. S. aureus in healthy milk samples produced more beta-hemolysin (3 times) and delta-hemolysin (2 times) when compared to S. aureus supernatants in milk from infected quarters. Furthermore, beta- and delta-hemolysis correlated negatively with TIC and NAGase and PL activities. Addition of reduced glutathione (GSH) or beta-mercaptoethanol into the artificial medium enhanced hemolysins activity.

Pharmacokinetics of sulphadoxine and trimethoprim and tissue irritation caused by two sulphadoxine-trimethoprim containing products after subcutaneous administration in pre-ruminant calves

The pharmacokinetics of sulphadoxine-trimethoprim was studied in 6 pre-ruminant calves using two different products. Product A, which contained 200 mg sulphadoxine and 40 mg trimethoprim per mL, was administered intravenously or subcutaneously at a dosage of 25 mg sulphadoxine and 5 mg trimethoprim.kg-1 bodyweight. Product B, containing 62.5 mg sulphadoxine and 12.5 mg trimethoprim per mL plus lidocaine (1 mg.mL-1), was given subcutaneously at the same dosage. After intravenous administration of product A the mean time of half-life of elimination phase (t1/2) for sulphadoxine was 12.9 h, steady-state volume of distribution (Vd(ss)) was 0.44 L.kg-1 and clearance was 0.024 L.kg-1.h-1. Respective values for trimethoprim were 1.9 h, 2.0 L.kg-1 and 0.9 L.kg-1.h-1. After subcutaneous administration, the bioavailability of sulphadoxine was 96% and 98% and the time to reach a maximum concentration was 6.3 and 8.0 h for products A and B, respectively. The Cmax for trimethoprim was higher for product A (0.49 microgram.mL-1) than for product B (0.32 microgram.mL-1) (p = 0.014). Slow absorption from the injection site appeared to delay the elimination of trimethoprim after subcutaneous administration when compared to that after intravenous administration: apparent elimination t1/2 for trimethoprim after intravenous administration of product A was 1.9 h compared to 3.9 h and 3.6 h after subcutaneous administration of products A and B, respectively. The difference between intravenous and subcutaneous administrations was statistically significant (p < 0.05). Also the mean residence time was significantly shorter (p < 0.05) after intravenous administration (2.4 h) than that after subcutaneous administration of product A (6.9 h) and B (7.1 h). The bioavailability of trimethoprim was lower than that of sulphadoxine: 76% and 74% for products A and B, respectively. All 6 calves showed pain after subcutaneous administration of product A and the injection sites were warm and showed soft oedematous reactions 5-8 cm in diameter. Three of the calves also showed some pain after subcutaneous administration of product B; the local reactions were less severe. A marked increase was seen in creatine kinase activity after subcutaneous administration of both products. Product A caused a more pronounced increase but the difference was not statistically significant. We suggest 30 mg.kg-1 at 24-h intervals or alternatively 15 mg.kg-1 at 12-h intervals as the minimum dosage of sulphadoxine-trimethoprim combination for pre-ruminant calves. Extravascular routes of administration should be avoided due to marked tissue irritation at the injection site.