Molecular epidemiology of recurrent clinical mastitis due to Streptococcus uberis: evidence of both an environmental source and recurring infection with the same strain.

This study was undertaken because clinicians and farmers have observed that a considerable number of cows diagnosed with Streptococcus uberis mastitis have recurrences of mastitis in the same or a different quarter. The study was an attempt to answer whether these recurring cases were due to treatment failure (in which case a search would have begun for a better treatment for Strep. uberis mastitis) or due to reinfection with a different strain of Strep. uberis. Using pulsed-field gel electrophoresis (PFGE), we determined that the majority of recurrences (20 of 27) were caused by a new strain of Strep. uberis, indicating that treatment of the initial infection had been successful. A small number of recurrences (5 of 27) were caused by the initial strain, indicating persistence. The remaining 2 recurrences occurred in a new quarter but with the initial strain of Strep. uberis, indicating either spread between quarters or reactivation of a previous subclinical infection. Analysis of the PFGE profiles failed to reveal any strain-specific propensity to persist, because strains causing recurrences occurred in most of the major clusters.

Premilking teat disinfection: is it worthwhile in pasture-grazed dairy herds?

A controlled trial was conducted in 5 pasture-grazed commercial dairy herds in Australia in 2012 to determine whether premilking teat disinfection and drying of teats reduces clinical mastitis incidence during early lactation by at least 50%. A 50% reduction was estimated to be the minimum required to justify additional costs of labor, disinfectants, and other resources if premilking teat disinfection was implemented in a 500-cow herd averaging 8 clinical cases per 100 cow-months. A secondary aim was to determine whether this premilking teat disinfection routine reduces incidence of new udder infections. Treatment was applied in each herd for approximately 60 d (range of 59.5 to 61 d), commencing in each herd soon after the start of the herd's main or only calving period. Within each herd, cows were allocated to either the treatment (premilking disinfection) or the control (no premilking disinfection) group based on their herd identity number. During the trial period, any cow having a new case of clinical mastitis or an individual cow cell count greater than 250,000 cells/mL of milk (when preceded by individual cow cell counts of 250,000 cells/mL of milk or below) was deemed to have had a new infection. Overall, neither clinical mastitis incidence nor new infection rate differed significantly between treatment and control groups. Over the whole study period, 98 of the 1,029 cows in the premilking disinfection group and 97 of the 1,025 cows in the control group had clinical mastitis. Total cow-days at risk of clinical mastitis were similar in each group. However, clinical incidence rates were markedly lower in treatment cows in one herd (herd 3; incidence rate ratio=0.34) and there was some evidence that new infection incidence rates were lower in treated cows in this herd (incidence rate ratio=0.42). Rainfall during the study period was below long-term district average in all 5 study herds. Cows' teats were less dirty than in previous, wetter years for the 4 herds where no significant clinical mastitis response was detected but some teat soiling was observed in herd 3 during the study period. Routine application of premilking teat disinfection in pasture-grazed herds is unlikely to produce a worthwhile (economic) reduction in the number of clinical mastitis cases when teats are relatively clean and dry and the clinical mastitis incidence is low. However, premilking disinfection might be worthwhile during periods when teats are heavily soiled and the incidence of clinical mastitis due to environmental pathogens is high.

The Value of 'Cow Signs' in the Assessment of the Quality of Nutrition on Dairy Farms.

The aim of this review is to provide dairy farm advisors, consultants, nutritionists, practitioners, and their dairy farmer clients with an additional toolkit that can be used in the assessment of the quality of their dairy cattle nutrition. Cow signs are behavioral, physiological, and management parameters that can be observed and measured. They are detected by examining and observing the cattle. Other physiological parameters such as fecal scoring, rumen fill, and body condition scoring are also included in 'cow signs'. The assessment should be both qualitative and quantitative; for example, is the cattle individual lame and what is the severity of lameness. The 'diagnosis' of a problem should be based on establishing a farm profile of 'cow signs' and other relevant information. Information gathered through assessment of cow signs should be used as an advisory tool to assist and improve decision making. Cow signs can be used as part of an investigation and or farm audit.

Identification of Streptococcus uberis multilocus sequence types highly associated with mastitis.

Multilocus sequence typing analysis of Streptococcus uberis has identified a cluster of isolates associated with clinical and subclinical mastitis and a cluster associated with cows with low somatic cell counts in their milk. Specific groups of genotypes (global clonal complex [GCC] sequence type 5s [ST5s] and GCC ST143s) were highly associated (P = 0.006) with clinical and subclinical mastitis and may represent a lineage of virulent isolates, whereas isolates belonging to GCC ST86 were associated with low-cell-count cows. This study has, for the first time, demonstrated the occurrence of identical sequence types (ST60 and ST184) between different continents (Australasia and Europe) and different countries (Australia and New Zealand). The standardized index of association and the empirical estimation of the rate of recombination showed substantial recombination within the S. uberis population in Australia, consistent with previous multilocus sequence type analyses.

Use of multiplexed tandem PCR to estimate the prevalence and intensity of Theileria orientalis infections in cattle.

This study employed a semi-quantitative, multiplexed tandem PCR (MT-PCR) to assess the prevalence and infection intensity of four genotypes (buffeli, chitose, ikeda and type 5) of Theileria orientalis in cattle in Australia. Genomic DNA samples from blood samples (n=448) collected from 27 to 32 dairy cows from each of 15 dairy herds with a history of recent theileriosis outbreaks (Group 1), and from blood samples available from 24 cows with or without oriental theileriosis (Group 2) were tested using MT-PCR. Results revealed that all four genotypes were present in Group 1 cattle; genotype buffeli had the highest prevalence (80.5%), followed by genotypes ikeda (71.4%), chitose (38.6%) and type 5 (20.3%). Genotype ikeda had the highest average infection intensity in the cattle (relating to 55,277 DNA copies), followed by buffeli, chitose and type 5 (6354-51,648 copies). For Group 2, results indicated that genotype ikeda had a significantly higher average intensity of infection than buffeli in symptomatic cattle (P<0.001), and symptomatic cattle had a higher intensity of ikeda than asymptomatic cattle (P=0.004). Future studies should assess the utility of the present MT-PCR assay as a diagnostic and epidemiological tool in other parts of Australasia and the world.

Oriental theileriosis in dairy cows causes a significant milk production loss.

BACKGROUND: Oriental theileriosis is a tick-borne, protozoan disease of cattle caused by members of the Theileria orientalis-complex. Recent outbreaks of this disease in eastern Australia have caused major concerns to the dairy and beef farming communities, but there are no published studies of the economic impact of this disease. On a farm in Victoria, Australia, we assessed whether oriental theileriosis has an impact on milk production and reproductive performance in dairy cows. METHODS: Blood samples collected from all 662 cows on the farm were tested using an established molecular test. For individual cows, milk production and reproductive performance data were collected. A clinical assessment of individual cows was performed. Based on clinical findings and molecular test results, the following groups of cows were classified: group 1, with cardinal clinical signs of oriental theileriosis and molecular test-positive for T. orientalis; group 2, with mild or suspected signs of theileriosis and test-positive; group 3, with no clinical signs and test-positive; and group 4, with no clinical signs and test-negative. Milk production and reproductive performance data for groups 1, 2 and 3 were each compared with those for group 4 using linear and logistic regression analyses, respectively. RESULTS: At 100 days of lactation, group 1 cows produced significantly less milk (288 l; P = 0.001), milk fat (16.8 kg; P < 0.001) and milk protein (12.6 kg; P < 0.001) compared with group 4. At this lactation point, group 2 also produced significantly less milk fat (13.6 kg; P = 0.002) and milk protein (8.6 kg; P = 0.005) than group 4. At 305 days of lactation, group 1 cows produced significantly less milk (624 l; P = 0.004), milk fat (42.9 kg; P < 0.001) and milk protein (26.0 kg; P < 0.001) compared with group 4 cows. Group 2 cows also produced significantly less milk fat (21.2 kg; P = 0.033) at this lactation point. No statistically significant difference in reproductive performance was found upon pairwise comparisons of groups 1-3 with group 4 cows. CONCLUSIONS: The present findings demonstrate that clinical oriental theileriosis can cause significant milk production losses in dairy cattle.

The effects on claw health of supplement feeding grazing dairy cows on feed pads.

The effects of feeding and management systems on the health and welfare of grazing dairy cows were investigated by comparing the claw health of cows fed grain during milking and pasture silage in the paddock (Control), with cows fed a grain-based partial mixed ration (PMR) on a concrete feed pad. Cows were assessed on three occasions during lactation: (1) early lactation (20-81 days in milk [DIM]) before allocation to feeding treatments; (2) mid-lactation (97-158 DIM) immediately following an intensive feeding experiment, and (3) late lactation (173-243 DIM) several months after return to initial management groups. At the final examination, claw puncture resistance was measured. The results showed that for the most prevalent lesions (white line disease, paintbrush haemorrhage and traumatic bruising), there was no effect of feeding system or amount of supplement on the presence of the moderate to severe forms in early lactation, but cows were more likely to have a particular lesion at the second assessment if it was present in early lactation. Puncture resistance of the claw was not related to presence of a lesion for any of the most prevalent lesion types. It was concluded for this herd that for most indicators of claw health, there was no overall effect of different feeding systems (supplement fed during milking or on a feed pad) or amount of supplement.