A note on effectiveness of dry cow therapy in New Zealand dairy herds

Two dry-cow therapy products were evaluated in seven factory-supply dairy herds in the Waikato area. A product containing neomycin sulphate and the benzathine salt of penicillin (Neopen D.C. White; Smith-Biolab) was used in five herds, and one containing benzathine cloxacillin (Orbenin, Beecham) was used in two herds. Non-treated control cows were included in each herd. Both products were effective in eliminating intramammary infections with Staphylococcus aureus, Streptococcus uberis, and Streptococcus agalactiae. Efficacy of dry-cow therapy against S. aureus was 83.8% and 85.2% respectively. Spontaneous cure rate among controls was 30.8% for S. aureus during the dry period. Spontaneous cure rate for Str. uberis was 50%, while dry-cow therapy eliminated 100% and 77.8%, respectively, for the two products. Dry-cow therapy with either product eliminated more than 90% of Str. agalactiae infections while spontaneous cure rate was only 28.6%. These results further support the effectiveness of dry-cow therapy in reducing the level of subclinical mastitis in dairy herds by shortening the duration of intramammary infections.     

Epidemiology of Streptococcus uberis intramammary infections in a dairy herd.

From 1987 to 1991, almost 36,000 quarter samples of mammary secretion representing 1790 lactations of 510 dairy cows from a research herd were collected for bacteriological examination. The percentage of cows infected with Streptococcus uberis ranged from 12 to 16% of cows/year. S. uberis was isolated from 14.2% of lactations over the 5-year period. The prevalence of S. uberis intramammary infection (IMI) was significantly higher in cows with > or = 4 lactations than in cows with 3 or fewer lactations. Regardless of lactation number, the prevalence of S. uberis was highest before parturition, during early lactation and near drying off. The prevalence of S. uberis infected quarters ranged from 1.3 to 2.3% of quarters/year; the prevalence rate for the 5-year period was 2% of quarters. The quarter prevalence of S. uberis was lowest in cows with < or = 3 lactations, increased significantly with lactation number and was highest in cows with > or = 6 lactations. The percentage of quarters infected with S. uberis varied significantly by year. The majority (95%) of S. uberis IMI were subclinical. The ratio of subclinical IMI to clinical IMI was lowest during early lactation, and increased with days in milk, and with lactation age except for cows in their 5th and 6th lactations. Results of this epidemiological investigation suggest that opportunities exist where suitable control measures could be applied to reduce the impact of S. uberis infections in the dairy herd.     

Interleukin-1β infusion in bovine mammary glands prior to challenge with <Emphasis Type="Italic">Streptococcus uberis</Emphasis> reduces bacterial growth but causes sterile mastitis

Dairy cows are especially vulnerable to intramammary infection by the bacterial pathogen Streptococcus uberis in the dry period. Use of immunotherapeutic agents at drying off could increase cellular defences in the gland and prevent establishment of new S. uberis infections. This study investigated the potential of infusing recombinant bovine interleukin-1 beta (rbIL-1beta) in the mammary glands as a prophylactic agent against subsequent intramammary challenge with S. uberis in the early dry period. Immediately after the last milking at commencement of the dry period, one cow from each of 10 monozygous twinsets was infused with 10 microg of rbIL-1beta in two quarters and the other twin was infused with the carrier agent, sterile phosphate buffered saline. Twenty-four hours later, the quarters were infused with 10(3) colony-forming units (CFU) of S. uberis. Bacteriology, somatic cell count (SCC), concentrations of specific cytokines and antibody responses were monitored in mammary gland secretions and sera for the next 21 days. Infusion of rbIL-1beta into mammary glands at commencement of the dry period was associated with less new S. uberis intramammary infections, as determined by the number of quarters with bacterial growth. However, high SCC in quarters following infusion of rbIL-1beta masked the full beneficial effect of this procedure.     

Efficacy of extended pirlimycin therapy for treatment of experimentally induced Streptococcus uberis intramammary infections in lactating dairy cattle

Streptococcus uberis is an important cause of mastitis in dairy cows throughout the world, particularly during the dry period, around the time of calving, and during early lactation. Strategies for controlling S. uberis mastitis have not received adequate research attention and are therefore poorly defined and inadequate. Objectives of the present study were to evaluate the efficacy of extended therapy regimens with pirlimycin for treatment of experimentally induced S. uberis intramammary infections in lactating dairy cows during early lactation and to evaluate the usefulness of the S. uberis experimental infection model for evaluating antimicrobial efficacy in dairy cows. The efficacy of extended pirlimycin intramammary therapy regimens was investigated in 103 mammary glands of 68 dairy cows that became infected following experimental challenge with S. uberis during early lactation. Cows infected with S. uberis in one or both experimentally challenged mammary glands were randomly allocated to three groups, representing three different treatment regimens with pirlimycin, including 2-day (n = 21 cows, 31 mammary quarters), 5-day (n = 21 cows, 32 quarters), and 8-day (n = 26 cows, 40 quarters). For all groups, pirlimycin was administered at a rate of 50 mg of pirlimycin hydrochloride via intramammary infusion. A cure was defined as an experimentally infected mammary gland that was treated with pirlimycin and was bacteriologically negative for the presence of S. uberis at 7, 14, 21, and 28 days after treatment. Experimental S. uberis intramammary infections were eliminated in 58.1% of the infected quarters treated with the pirlimycin 2-day regimen, 68.8% for the 5-day regimen, and 80.0% for the 8-day regimen. Significant differences (P <.05) in efficacy were observed between the 2-day and 8-day treatment regimens. The number of somatic cells in milk decreased significantly following therapy in quarters for which treatment was successful in eliminating S. uberis. However, there was no evidence to suggest that extended therapy with pirlimycin resulted in a greater reduction in somatic cell counts in milk than the 2-day treatment. The S. uberis experimental infection model was a rapid and effective means of evaluating antimicrobial efficacy during early lactation at a time when mammary glands are highly susceptible to S. uberis intramammary infection.     

Treatment of persistent intramammary infections with Streptococcus uberis in dairy cows

A survey was conducted of the prevalence of environmental pathogens, especially Streptococcus uberis, as causes of clinical mastitis in dairy cows. The response of intramammary infections with S uberis to conventional treatment was monitored by taking milk samples for bacteriology and somatic cell counting seven, 14 and 21 days after the treatment. The results showed that 51 per cent of the infections failed to respond, and the odds of cases failing to respond was significantly increased when the individual quarter somatic cell count seven days after the treatment was greater than 201,000 cells/ml. Ninety-six per cent of the suspected S uberis isolates identified by culture were confirmed as S uberis by using the api 20 Strep system. Restriction endonuclease fingerprinting was used to type the strains of S uberis isolated from 75 milk samples from 32 cows. Analysis showed that 96 per cent of the cases of S uberis that failed to respond to conventional treatment were persistent infections with one strain rather than reinfections with different strains. The persistent cases of S uberis were treated further with an extended course of intramammary preparations containing either procaine penicillin with dihydrostreptomycin or cefquinome. There was no significant difference between the cure rates achieved by the two preparations, and 55 per cent of the cases that had failed to respond to conventional treatment responded to the additional treatment.     

Identification of aesculin-hydrolyzing streptococci, lactococci, aerococci and enterococci from subclinical intramammary infections in dairy cows

Aesculin-hydrolyzing, catalase-negative, gram-positive cocci isolated from subclinical intramammary infections in dairy cows were identified to species level using growth characteristics and biochemical activity. The results indicated that the aesculin-hydrolyzing cocci associated with this type of infection are a very heterogenic group. S. uberis strains, including inulin- or beta-glucuronidase-negative isolates, accounted for only about one-third of the collection, and Enterococcus faecalis strains for one-fifth. Other species of some importance included (in descending order of isolation frequency) Aerococcus viridans, Streptococcus pluranimalium, Lactococcus garvieae, Streptococcus bovis and Streptococcus gallolyticus.     

Host-response patterns of intramammary infections in dairy cows

Many different bacterial species have the ability to cause an infection of the bovine mammary gland and the host response to these infections is what we recognize as mastitis. In this review we evaluate the pathogen specific response to the three main bacterial species causing bovine mastitis: Escherichia coli, Streptococcus uberis and Staphylococcus aureus. In this paper we will review the bacterial growth patterns, host immune response and clinical response that results from the intramammary infections. Clear differences in bacterial growth pattern are shown between bacterial species. The dominant pattern in E. coli infections is a short duration high bacteria count infection, in S. aureus this is more commonly a persistent infection with relative low bacteria counts and in S. uberis a long duration high bacteria count infection is often observed. The host immune response differs significantly depending on the invading bacterial species. The underlying reasons for the differences and the resulting host response are described. Finally we discuss the clinical response pattern for each of the three bacterial species. The largest contrast is between E. coli and S. aureus where a larger proportion of E. coli infections cause potentially severe clinical symptoms, whereas the majority of S. aureus infections go clinically unnoticed. The relevance of fully understanding the bovine host response to intramammary infection is discussed, some major gaps in our knowledge are highlighted and directions for future research are indicated.     

pGh9:ISS1 transpositional mutations in Streptococcus uberis UT888 causes reduced bacterial adherence to and internalization into bovine mammary epithelial cells

Streptococcus uberis is an important mastitis pathogen that affects dairy cows worldwide. In spite of the economic impact caused by the high prevalence of S. uberis intramammary infections (IMI) in many well-managed dairy herds, pathogenic strategies and associated virulence factors of S. uberis are not well understood. It has been shown that S. uberis attaches to and internalizes into mammary epithelial cells and can survive inside cells for extended periods of time. We hypothesize that early attachment to and internalization into mammary epithelial cells is a critical step for the establishment of intramammary infection. The aim of this study is to identify and characterize chromosomally encoded virulence factors of S. uberis that allow early bacterial attachment to and internalization into mammary epithelial cells. A common approach used to identify virulence factors is by generating random insertion mutants that are defective in adherence to and internalization into mammary epithelial cells using pGh9:ISS1 mutagenesis system. A random insertion mutant library of S. uberis strain UT888 was created using a thermo-sensitive plasmid pGh9:ISS1 carrying ISS1 insertion sequence. Integration of the insertion sequence into the chromosome of these mutant clones was confirmed by PCR and Southern blot. Southern blot analysis of mutant clones also showed that insertional integration was random. Of 1000 random chromosomal insertion mutants of S. uberis strain UT888 screened, 32 had significantly reduced ability to adhere to and internalize into mammary epithelial cells. Chromosomal mapping of insertion sequence integration sites in some of these defective mutants showed integration into penicillin binding protein 2A (pbp2A), sensor histidine kinase, tetR family regulatory protein, phosphoribosylaminoimidazole carboxylase catalytic subunit (purE), lactose phosphotransferase, phosphoribosylamine glycine ligase (purD), and other genes involved in metabolic activities. These proteins may have a significant role in early bacterial colonization of the mammary gland during infection.     

Simultaneous intramammary and intranasal inoculation of lactating cows with bovine herpesvirus 4 induce subclinical mastitis

In this study, we examined whether an experimental bovine herpesvirus 4 (BHV4) infection can induce bovine mastitis, or can enhance bovine mastitis induced by Streptococcus uberis (S. uberis). Four lactating cows were inoculated intramammarily and intranasally with BHV4, and four lactating control cows were mock-inoculated. After 14 days, two of four cows from each group were inoculated intramammarily with S. uberis. No clinical signs were recorded in cows inoculated only with BHV4, and their milk samples showed no abnormal morphology, despite the fact that BHV4 replicated in inoculated quarters. Somatic cell count increased significantly in milk from three of six BHV4-inoculated quarters, compared to the non-inoculated quarters of the same cows (within-cow) and the quarters of mock-inoculated cows (control group) on days 8, 9 and 11 post-inoculation (pi). BHV4 was isolated from nasal swabs between days 2 and 9 pi. Clinical mastitis was observed in all four cows intramammarily inoculated with S. uberis. A preceding BHV4 infection did not exacerbate the clinical mastitis induced by S. uberis. S. uberis infections appeared to trigger BHV4 replication. From one quarter of each of two cows inoculated with BHV4 and S. uberis, BHV4 was isolated, and not from quarters inoculated with BHV4 only. In conclusion, BHV4 did not induce bovine clinical mastitis after simultaneous intranasal and intramammary inoculation. However, the BHV4 infection did induce subclinical mastitis in 50% of the cows and the quarters.     

Molecular characterization of the antimicrobial resistance of Riemerella anatipestifer isolated from ducks

Streptococcus uberis is a major environmental mastitis-causing pathogen. The infections are predominantly subclinical and are frequently undetected and untreated for extended periods of time. More information about the pathogenesis of S. uberis mastitis would be useful. To our knowledge, no experimental studies into the mastitis pathogenesis caused by S. uberis have been described in lactating goats. The aim of this study was to reproduce an experimentally induced S. uberis subclinical mastitis in lactating goats aimed to evaluate the inflammatory response, dynamics of infection and the pathological findings within the first hours of intramammary inoculation with S. uberis. Six Saanen goats in mid-lactation were inoculated with 1.7 × 10(8)cfu of S. uberis. Bacterial growth peaked in milk from challenged right mammary halves (RMH) at 4h PI. Shedding of viable bacteria showed a marked decrease at 20 h PI. Mean somatic cell counts in milk from the RMH peaked at 20 h PI. Inoculation with S. uberis was followed by a decrease in the mean total number of leukocytes. Signs and systemic symptoms were not evoked by intramammary inoculation. S. uberis could be isolated in tissue from all RMH. Histological examination of specimens of the RMH and lymph nodes of the goats showed an increased inflammatory response throughout the experiment. The histological findings correlated with the immunohistochemical detection of S. uberis in RMH. In conclusion, the experimental inoculation of S. uberis in lactating goats is capable of eliciting an inflammatory response and causing pathological changes, resulting in a subclinical mastitis. This investigation shows that goat might to represent a valuable model for the study of the mastitis pathogenesis caused by S. uberis.     

The prophylactic effect of a dry-cow antibiotic against Streptococcus uberis

The prophylactic use of a dry-cow antibiotic for reducing the incidence of mastitis due to Streptococcus uberis was studied in four seasonally calving dairy herds involving 378 cows. The treatment was a long-acting dry-cow antibiotic preparation administered immediately after the last milking of lactation. New intramammary infections were identified by comparing the bacteriological status of quarters at drying off with that after calving, or through manual udder palpation during the dry period. The administration of dry-cow antibiotic to uninfected quarters at drying off reduced the overall incidence of new infections with Streptococcus uberis from 12.3% for untreated quarters to 1.2% of quarters (p<0.01). The reduction was significant (p<0.01) for both dry-period and post-calving infections. The susceptibility of uninfected quarters to new infection by Streptococcus uberis appeared to be unrelated to the infection status of a cow at drying off. Clinical infections during the dry period were most prevalent (97%) in quarters identified as having open teat canals. Fewer open teat canals (p<0.05) were observed among antibiotic treated quarters over the first 4 weeks of the dry period. Treated quarters had a lower (p<0.05) incidence of new clinical infection during the ensuing lactation and lower somatic cell counts. This did not affect production levels of milk, milk fat or protein. The results clearly indicated a prophylactic benefit for the dry cow antibiotic treatment against new Streptococcus uberis infections during the dry period.     

Streptococcus uberis: A Permanent Barrier to the Control of Bovine Mastitis?

The prevalence of bovine mastitis has been reduced over the past 25 years due to the implementation of a five-point control plan aimed at reducing exposure, duration and transmission of intramammary infections by bacteria. This has markedly reduced the incidence of bovine mastitis caused by bacteria which show a contagious route of transmission, but has had little effect on the incidence of mastitis due to bacteria which infect the gland from an environmental reservoir. Streptococcus uberis is one such bacterium which is responsible for a significant proportion of clinical mastitis worldwide.The inadequacies of the current methods of mastitis control have led to the search for additional measures, particularly vaccines to prevent intramammary infection by this bacterium. Such an approach requires detailed knowledge of the pathogenesis of intramammary infection. Our understanding of this area has grown in recent years but a lack of information still hampers disease control. Both live vaccines and, recently, crude sub-unit vaccines have shown promise against bovine mastitis due to S. uberis. Vaccines against mastitis must, however, be able to control infection without the participation of a marked inflammatory response. This review provides an overview of the recent advances which have been made in our understanding of host-pathogen interactions which promote infection and disease and highlights areas for strategic research aimed at controlling this bacterial infection.     

Comparative efficacy of dry-cow treatment regimens against Staphylococcus aureus

Four dry-cow treatment regimens were evaluated against Staphylococcus aureus intramammary infections: 1) high persistency product at drying off and low persistency product 1 to 3 days prepartum; 2) high persistency product at drying off; 3) low persistency product 1 to 3 days prepartum; 4) untreated controls. Treatment 1 was no more efficacious (64.4%) than Treatment 2 (61.3%). Both treatments were significantly different from spontaneous recovery observed in Treatment 4 (41.2%), but not significantly different from Treatment 3 (46.9%). Dry-cow therapy reduced new S. aureus intramammary infections during the dry period by half. Prepartum treatment eliminated more than 90% of new Streptococcus uberis infections.     

Quarter milk somatic cell count in infected dairy cows: a meta-analysis

The aim of this paper was to evaluate the effects associated with intramammary infection (IMI) by a bacterium or a group of bacteria (Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, coliforms, Staphylococci other than S. aureus, and Corynebacterium bovis) on the somatic cell count (SCC) in quarter milk of dairy cows. Papers selected for analysis had to provide SCC values associated with the natural infection in quarters by different bacteria. Sampling for measurement of SCC and determination of the infection had to be done on the same day. Only papers published in English or in French after 1971 were considered. Twenty-one papers fulfilled the selection criteria. The animals sampled, the measurement techniques for SCC and the bacteriological identification, as well as the definition of the infection, all differed widely among the selected studies. The meta-analysis method was used to estimate both the mean SCC (arithmetic and geometric) value and the average increase on SCC of each type of infection. The geometric mean SCC in bacteriologically negative quarters was 68 000 c/mL. In case of IMI, the retained SCC was 357 000, 857 000, 547 000, 1 024 000, 1 151 000, 138 000 and 105 000 c/mL in quarters infected by Staphylococcus aureus, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, coliforms, staphylococci other than S. aureus and Corynebacterium bovis, respectively. The variation factors that could influence these SCC values and the bacteriological results are discussed.     

Fomites and reservoirs of Staphylococcus aureus causing intramammary infections as determined by phage typing: the effect of milking time hygiene practices

We studied the association of milkers' hands and milking unit liners as fomites, and teat skin as a reservoir, with S. aureus intramammary infections (IMI). Samples were collected from 40 commercial herds and S. aureus isolates were phage typed. Only 10 of 257 isolates were not typable. Of the milk samples, 8.4% had typable S. aureus; 4.5% and 9.2% of the skin and liner swabbings had typable S. aureus. Twenty-three different phage types were identified, 1 type was found in nearly 75% of the herds. Herds in which milking unit backflush was used were less likely to have the same phage type on the liners and the teat skin, and on the liners and milk samples, than herds that did not backflush. A greater percentage of liners had S. aureus of the same type as those causing S. aureus IMI, than skin swabbing solutions with the same type as that associated with IMI. Herds which did not use post-milking teat asepsis (teat dip) did not have a greater percentage of S. aureus isolates on the teat skin, nor were the S. aureus test skin isolates more likely to be of the same type as those causing intramammary infection. Results would suggest that the liner appears to be a significant fomite, that backflushing reduces its significance, and that teat skin is a less significant reservoir for S. aureus intramammary infection.     

Pathogen group specific risk factors at herd, heifer and quarter levels for intramammary infections in early lactating dairy heifers

Risk factors for intramammary infections caused by coagulase-negative staphylococci, contagious major pathogens and environmental major pathogens in early lactating heifers were evaluated at the herd, heifer and quarter levels. In total, 764 quarters of 191 dairy heifers in 20 randomly selected farms in Flanders (Belgium) were sampled. Quarter milk samples were collected between 1 and 4 days in milk and between 5 and 8 days in milk for bacteriological culture. Data were analyzed using multivariable, multilevel logistic regression analysis. Higher average herd milk somatic cell count (>200,000 cells/mL), not having an effective fly control strategy, contact with lactating cows prior to calving and moderate to severe udder edema prior to calving increased the odds of intramammary infections caused by contagious major pathogens. Poor heifer hygiene and lack of mineral/vitamin supplementation prior to calving were risk factors for intramammary infection caused by environmental major pathogens. Teat apex colonization with coagulase-negative staphylococci prior to calving seemed to protect quarters against intramammary infections caused by major pathogens. Poor heifer hygiene before calving, a non-clipped udder and not practicing of teat dipping prior to calving increased the odds of intramammary infection with coagulase-negative staphylococci. Although management is important in the prevention and control of intramammary infections in early lactating heifers, most variation in the prevalence of intramammary infections resided at the heifer and quarter levels, indicating that the susceptibility for intramammary infections around calving is mainly determined by heifer and quarter characteristics.     

Incidence and types of clinical mastitis in dairy herds with high and low somatic cell counts

Eighteen dairy herds were studied, 12 with a 12-month Dairy Herd Improvement Association herd mean somatic cell count (SCC) less than or equal to 150,000 cells/ml (low SCC) and 6 with a 12-month mean SCC greater than 700,000 cells/ml (high SCC). At the outset of the study, quarter samples for bacteriologic culture were collected (in duplicate) from all quarters of all lactating cows (whole herd culture). Subsequently, quarter milk samples for culture from all cows with clinical mastitis were collected for a period of 6 months. In the herds with low SCC, results of whole herd culture revealed low prevalence of intramammary infection attributable to all major pathogens (less than 4% of all quarters). Prevalence of infection with Streptococcus agalactiae (22.2% of all quarters) and Staphylococcus aureus (6.6% of all quarters) was significantly (P less than 0.05) higher in the herds with high SCC. Mean incidence of clinical mastitis in the herds with low SCC was 4.23 infections/100 cows/month (range, 0.42 to 10.25 infections). In the herds with high SCC, mean incidence was 2.91 infections/100 cows/month (range, 1.33 to 3.92 infections). In the herds with low SCC, infection type, as mean percentage of total clinically infected quarters sampled for culture/herd, was 0.0%, 2.2%, 12.3%, 43.5%, and 28.6% for Str agalactiae, S aureus, streptococci other than Str agalactiae, coliforms, and organisms not isolated, respectively. Respective percentages for the herds with high SCC were 41.5%, 18.3%, 12.6%, 8.0%, and 8.8%. During the study period (from April through January), incidence of clinical mastitis and clinical mastitis caused by coliform bacteria were highest in July and August for herds with low SCC.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dynamics of leukocytes and cytokines during experimentally induced Streptococcus uberis mastitis

Streptococcus uberis causes a significant proportion of clinical and subclinical intramammary infections (IMI) in lactating and non-lactating dairy cows. In spite of this, its pathogenesis is incompletely understood. A study was conducted to determine leukocyte and cytokine dynamics during experimentally induced S. uberis mastitis. Five Jersey and five Holstein cows were challenged via intramammary inoculation of S. uberis into two uninfected mammary glands. Sixteen of 20 challenged mammary glands developed clinical mastitis with peak clinical signs observed at 144 h. The number of S. uberis in milk increased (P<0.05) 48 h after challenge, in spite of an increase in milk somatic cells that began at 18 h (P<0.001) and remained elevated throughout the study. Increased tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-8 (IL-8) in milk were detected 66 h after challenge (P<0.05). Peak TNF-alpha and IL-8 concentrations occurred 120 h after challenge and preceded peak clinical signs. Experimental S. uberis IMI induced local production of TNF-alpha, IL-1beta and IL-8, which may play a role in the pathogenesis of S. uberis mastitis. Other mediators may be involved in initial leukocyte recruitment to the mammary gland, since increases in milk somatic cells occurred earlier than cytokine production.     

Epidemiological study of non-contagious intramammary infections in nine commercial dairy herds following a Staphylococcus aureus control programme

Changes in prevalence in intramammary infection, by pathogen type, in herds applying a stringent contagious mastitis control programme was studied. Enrollment of 1651 lactating cows and collection of milk samples was made in this ancillary study to a cohort study of the dynamics of mastitis prevalence after adoption of a strict contagious mastitis control programme that targeted the elimination of mastitis caused by Staphylococcus aureus. Nine commercial dairies in Italy were used. Aseptic collection of milk samples from all lactating cows was performed at the time of enrollment, from all cows within 7-14 days of entering the lactating herd after the date of enrollment, and from all lactating cows at 2, 4, 7, 10 and 14 months after the date of enrollment. Prevalence of intramammary infection by pathogen type was determined from culture of milk samples. Application of the strict contagious mastitis programme did not lead to an increased risk of non-contagious mastitis. The risk of coliform, environmental streptococcal and coagulase-negative staphylococcal intramammary infections decreased after adoption of the programme. The data reported herein indicate that the overall risk for any intramammary infections decreases with adoption of a strict contagious mastitis programme, and that such a programme therefore does not necessarily lead to an increase in environmental mastitis.     

Relationships between teat-end bacteria and intramammary infections

Teat-end populations of staphylococci and streptococci were studied on teat apices of an experimental herd. Individual cows were found to have higher numbers of some of these microorganisms than other cows and certain teats had consistently higher populations than other teats in the same individual. A positive relationship was found between the numbers of staphylococci on teat-ends and presence of intramammary infections of the quarters. High teat-end bacterial numbers were present prior to the laboratory recognition of intramammary infections.