Mycoplasma mastitis in dairy cattle

The most important characteristics of Mycoplasma mastitis on dairy farms are described, based on two case studies. Clinical symptoms, diagnostics, epidemiology, and a plan of action are presented. In the herds investigated, Mycoplasma mastitis was characterized by multiple affected quarters unresponsive to treatment with antibiotic and/or anti-inflammatory agents. Most striking were a sandy sediment, brown colouring, and rice-like structure of the milk of affected animals. Clinical symptoms differed in the two affected herds. Diagnosis was based on bacteriological investigation of samples of milk and synovial fluid taken from infected cows. Affected animals were culled immediately, and the herds were monitored by repeated testing of bulk milk samples. It was concluded that a consequence of the increasing size of cattle herds in the Netherlands is that subclinical/clinical Mycoplasma mastitis may be diagnosed more frequently than in the past. In the case of Mycoplasma mastitis, farmers and veterinary practitioners are advised to draw up a plan of action together, incorporating aspects such as diagnostics at cow level, direct culling of affected animals, hygiene during milking, including post-milking teat disinfection, and routine monitoring of bulk milk. Unpasteurized milk should not be given to calves.     

Production effects related to mastitis and mastitis economics in dairy cattle herds

Mastitis is the most prevalent production disease in dairy herds world-wide and is responsible for several production effects. Milk yield and composition can be affected by a more or less severe short-term depression and, in case of no cure, by a long-acting effect, and, sometimes, an overlapping effect to the next lactation. Summary values in the literature for losses of milk production were proposed at 375 kg for a clinical case (5% at the lactation level) and at 0.5 kg per 2-fold increase of crude SCC of a cow. Due to the withdrawal period after treatment, composition changes in milk can almost be neglected in economic calculations. Lethality rate for clinical mastitis is very low on the average, while anticipated culling occurs more frequently after clinical and subclinical mastitis (relative risk between 1.5 and 5.0). The economics of mastitis needs to be addressed at the farm level and, per se, depends on local and regional epidemiological, managerial and economic conditions. To assess the direct economic impact of mastitis, costs (i.e. extra resource use) and losses (i.e. reduced revenues) have to be aggregated. To support decision making for udder health control, it is necessary to use a marginal approach, based on the comparison of the losses avoided and the additional costs of modified plans, compared to the existing ones.     

Mycoplasmal mastitis in dairy herds.

Mycoplasmal bovine mastitis is potentially a highly contagious disease that can cause severe economic problems in affected herds. The purchase of replacement heifers and cows are frequently the origin of mycoplasmal mastitis outbreaks in previously Mycoplasma-free herds. Purchased cows and heifers should be quarantined and tested for mycoplasmal mastitis before admission to the regular herd. Detection of Mycoplasma-infected cows by culture of milk is straightforward, although there are problems of sensitivity for its detection in milk samples that are inherent to the nature of the disease and laboratory procedures. After detection of infected cows, the best way to protect the herd is to culture all cows in the herd, cows with clinical mastitis, and all heifers and cows after calving and before entering the milking herd. Control of mycoplasmal mastitis requires test and culling from the herd of Mycoplasma-positive cows if possible. When a large number of cows are infected, strict segregation with adequate management is an option; however, animals in this group should never re-enter the Mycoplama-free herd. The functioning of the milking equipment and milking procedures should be evaluated carefully and any flaws corrected. There is no treatment for mycoplasmal mastitis, and vaccination has not proven to be efficacious to prevent, decrease the incidence, or ameliorate the clinical signs of mycoplasmal mastitis. Waste milk should not be fed to calves without pasteurization. M bovis may cause several other pathologies in animals of different ages on a farm, including pneumonia, arthritis, and ear infections. The survival of mycoplasmas in different farm microenvironments needs to be further investigated for its impact on the epidemiology of the disease.     

Clinical Mycoplasma bovis mastitis in prepubertal heifers on 2 dairy herds

Findings of herd investigations of heifers with prepubertal mastitis are presented. Mycoplasma bovis was isolated from lacteal secretions and tissue samples of necropsied heifers; the same strain infected dams and herd mates. Vertical transmission is suggested in this first report of intramammary infections of M. bovis in peripubertal heifers.     

Aetiology of clinical mastitis in six Somerset dairy herds.

Clinical mastitis was monitored in six Somerset dairy herds for one year. The herds all had three-month geometric mean bulk milk somatic cell counts of less than 250,000 cells/ml. Escherichia coli was the predominant pathogen isolated on all the farms and in all months of the year. Environmental pathogens accounted for 61.4 per cent of all cases of clinical mastitis and for 79.3 per cent of the mastitis cases in which an aetiological agent was identified. The mean annual incidence was 41.6 cases per 100 cows (range 14 to 75). Affected cows suffered a mean of 1.5 cases and 16.4 per cent of quarters suffered at least one repeat case. Mastitis due to E. coli was more severe than mastitis due to other causes and it tended to be more severe in early lactation and during the housing period. Mastitis was significantly more severe (grades 2 and 3) in the herd with the lowest bulk milk somatic cell count and in the herd which was kept indoors throughout the year than in the other four herds. Mastitis was fatal in 2.2 per cent of cases and resulted in the death of 0.6 per cent of the lactating cows.     

Studies of Mycoplasma mastitis in cattle. 6. Testing of Mycoplasma isolated from milk for udder pathogenicity

Strains of M. bovis, A. laidlawii, A. axanthum, and one unidentified strain of the family of mycoplasmataceae as well as altered secretion obtained from cows with mastitis were intracisternally applied in experiments and proved to be pathogenic to cattle udder. The results are likely to suggest the importance of mycoplasma isolated from the milk of mastitis cows to the aetiology of enzootic mastitis in three large dairy cattle stocks. Intravenous application of M. bovis and A. laidlawii caused neither mastitis nor mycoplasma secretion in the milk.     

Studies of Mycoplasma mastitis in cattle. 5. Studies of udder pathogenicity of Mycoplasma and Acholeplasma strains of different origins

Isolated acholeplasma laidlawii strains exhibited highly differentiated behaviours regarding their udder pathogenicity. Twelve of 16 tested strains were pathogenic to udder. Symptoms of acute udder inflammation were caused by all ten A. laidlawii strains isolated from differentiated material of calf, but by only two of six strains isolated from differentiated material of cattle. Intracisternal instillation of both strains from milk and one strain each from udder skin or cervical mucus caused merely temporary disorders of secretion. Ultrasonic extracts of A. laidlawii strains, some of them additionally heated, were intracisternally applied, as well. Udder irritation was caused only by those acholeplasma strains which were udder-patha was assumed to be attributable to a toxin of the polysaccharide type. Pathogenicity to udder was recorded also from one M. alkalescens strain isolated from a nose swab taken of cattle as well as from two A. granularum strains isolated from calf lungs.     

Preliminary studies on the prevalence of Mycoplasma bovis mastitis in dairy in cattle in Australia

A highly sensitive and specific PCR (MB-PCR) was used in preliminary studies to detect M. bovis in milk samples to investigate its association with high somatic cell count (SCC), an indicator of subclinical mastitis and one of the factors in down grading the quality of milk. A total of 186 and 167 herds were tested with 43% and 62% of herds positive for M. bovis in Victoria and North Queensland, respectively. The quarter milks from 52 cows with persistently high SCC were tested by MB-PCR and culture to investigate the association of M. bovis with major mastitis pathogens (MMP). M. Bovis was detected in 77% of cows of which 19% alone had M. bovis without any other bacteria, 17% had M. bovis in combination with major mastitis pathogens and 40% had M. bovis in combination with non-major mastitis pathogens. We believe that M. bovis is widespread in dairy cattle and has the potential to produce disease alone or to predispose the udder to disease caused by major mastitis and environmental pathogens. These studies have revealed a hitherto unrecognised high prevalence of M. bovis in dairy cattle in North Queensland and Victoria in Australia. These initial studies also give a clear association between M. bovis and elevated somatic cell counts.     

A survey of mastitis in selected ontario dairy herds

A mastitis survey involving 74 Ontario dairy herds was conducted. The prevalence of infection at the quarter level was found to be 4.1% with Streptococcus agalactiae, 4.5% with other streptococcal species and 8.0% with Staphylococcus aureus. Regardless of the infection status, the geometric mean somatic cell count was found to increase with age of the cow but no increase was observed with increasing stage of lactation. The percentage of cows from which a bacterial pathogen was isolated increased with age but not with stage of lactation.     

Iodine toxicosis in six herds of dairy cattle

Daily iodine intake estimated to range from greater than 68 to 600 mg/animal/day was associated with signs referable to iodine intoxication in adult cows in 6 herds of dairy cattle. Signs were reversed by lowering supplemental intake to less than 12 mg/animal/day. Results of biochemical tests other than those for serum and milk iodine were not diagnostic. Serum iodine concentrations were 2.6 to 6.9 times the mean iodine concentration found in 12 control cows, each receiving 12 mg of iodine/day. Milk iodine concentrations were 3.6 to 13.6 times milk iodine concentrations in the control cows.     

A case-control study of Nocardia mastitis in Ontario dairy herds

A case-control study was conducted to identify milking hygiene and udder therapy factors associated with a diagnosis of Nocardia mastitis in dairy herds from which milk samples are submitted to the Ontario Ministry of Agriculture and Food, Veterinary Laboratory Services, Guelph laboratory. The data were collected by telephone interview from 31 case and 31 control herds.

After analytical control for confounders, blanket dry cow therapy and a dry cow antibiotic product were associated with a diagnosis of Nocardia mastitis in a herd, whereas another dry cow antibiotic product had a sparing effect.

In comparison to mastitis pathogens susceptible to dry cow antibiotic therapy, Nocardia species were isolated infrequently from milk specimens submitted to the Guelph mastitis laboratory.