Many strains of E. coli, Klebsiella, and Enterobacter can cause udder infection in dairy cows. Although some cases are severe, and occasionally fatal, most cases are self-limiting and would be resolved without therapy. Chronic coliform infections also occur; these may be subclinical but typically elicit recurrent clinical episodes. Therapy of acute coliform infections should be directed at removal of and neutralization of the effects of endotoxin. In cases of endotoxic shock, electrolyte and fluid therapy are indicated. Selection of antibacterial drugs is made difficult by the variable susceptibility of the organisms and by the inavailability of effective drugs approved for use in dairy cows. The coliform-infection rate is not reduced by conventional mastitis-control schemes that employ germicidal teat dips and antibiotic therapy of dry cows. Germicidal teat dips are generally ineffective because coliform bacteria can reach the teat end at any time between milkings when the germicidal activity is gone. A teat dip providing a barrier film over the teat orifice between milkings has given promising results in reducing coliform infection in lactating cows. Bedding materials appear to be a major reservoir of coliform bacteria. Sawdust bedding can support high populations of coliform bacteria, especially Klebsiella. Treatment of sawdust with slaked lime can reduce coliform populations in sawdust bedding, but its effect on infection has not been determined. Other methods of control of coliform mastitis believed effective are the following: Careful premilking hygiene, including sparing use of water and careful drying of teats and udder before applying the milking machine. Maintenance of clean conditions for dry and calving cows; sawdust should be avoided as bedding for springing and newly calved cows.
Recognition of Mycoplasma-induced mastitis is on the increase. Although Mycoplasma bovis is identified as the causative agent in more than 50 per cent of the mastitis cases, seven other Mycoplasma species have also been isolated. The mycoplasmas are commonly found in the microflora of the respiratory and urogenital tracts of normal cattle, where precipitating factors can initiate their role as pathogens. Most udder infections are spread from cow to cow by physical contact and are precipitated through deficiencies in procedures in milking, equipment maintenance, sanitation, and udder infusion. Generally, the reaction in the udder is severe and persistent, and recovered animals remain shedders and potential carriers. Extensive therapy with antibiotics has not proven effective in altering the course of the disease. Control procedures in epizootics of mycoplasmal mastitis are based either on elimination of the infected animals by culling or through the co-existence on the dairy of known carrier animals segregated and milked separately from the uninfected animals. Adequate sanitation, proper udder infusion, and good milking principles are requisites to preventing mycoplasmal infections.
Streptococcus agalactiae is a contagious pathogen that causes bovine mastitis worldwide, resulting in considerable economic losses. In this study, we isolated 42 S. agalactiae strains in 379 milk samples from cows with subclinical mastitis on 15 dairy farms in 12 Chinese provinces. Analysis based on capsular typing and multilocus sequence typing, combined with patterns of virulence gene scanning and antimicrobial resistance, identified the lineages and populations of the isolates. We grouped the 42 isolates into 7 sequence types belonging to 6 clonal complexes, mainly CC103 (31/42 isolates; 73.8%). We identified an ST-23 strain named Sa 129 for the first time on Chinese dairy farms—this strain is usually associated with human isolates. Capsular types Ia and II were predominant in capsular typing. The prevalence of virulence profile 1 (bibA, cfb, cspA, cylE, fbsA, fbsB, hylB, and pavA) was 64.3%, and represented the main trend in China. With respect to antimicrobial resistance, most isolates were susceptible to β-lactams, rifamycin, glycopeptides, and oxazolidone; resistance to several antimicrobial agents, including lincomycin, clindamycin, and doxycycline, varied in 4 different regions. Our research provides a profile for the molecular epidemiology, multilocus sequence typing, antimicrobial resistance, and virulence gene clustering of S. agalactiae, and may be beneficial for the clinical monitoring, prevention, and control of mastitis in dairy cattle.
Uveitis (inflammation of the iris, ciliary body, or choroid) is a potentially blinding condition with a significant economic impact on the horse industry. Variable symptoms are described, as well as a considerable range of structural and functional sequelae. Known causes of initial episodes include bacterial, viral, traumatic, and parasitic insults, with recurrence by immunologic mechanisms. Treatment strategies and management recommendations that may reduce the incidence or severity of episodes are discussed.
This study was performed to determine the normal seasonal aerobic and an-aerobic corneoconjunctival bacterial flora in cats. Thirty eyes of 15 clinically normal client-owned Persian cats were evaluated. All cats lived in a similar indoor/outdoor home environment being fed the same diet for the entire year. The cats did not receive any medications and were found to be clinically healthy 1 week prior to each microbial sampling. The cats were not exposed to other cats during the study period. Microbial samples were collected at the same time of day on the first day of the second month of each of the four seasons. During sample collection, a sterile swab was rolled over the corneoconjunctival surface avoiding contact with surrounding skin or hair. Immediately after sample collection, microbiologic aerobic and anaerobic cultures were initiated. Gram-positive bacteria were the most prevalent isolates. The most commonly isolated bacterial organisms across all seasons were Staphylococcus epidermidis (41/95; 43.2%), β-hemolytic streptococcus (18/95; 18.9%), Staphylococcus aureus (17/95; 17.9%), and Escherichia coli (11/95; 11.5%). Twenty-five cultures of a total of 120 (20.8%) were negative. One negative culture was collected in the summer, while 21 cultures were negative in fall and winter. Gram-positive bacteria were the predominant micro-organisms of the normal ocular surface of healthy cats in all seasons in this study. This result is in agreement with previous publications.
Bovine ischaemic teat necrosis (ITN) is an emerging disease of unknown aetiology affecting mostly dairy cows in the early stages of first lactation and a substantial welfare concern frequently leading to premature culling and economic losses. Specific diagnostic criteria are lacking. The aims of this study were to develop an appropriate ITN grading system, describe the histopathological changes and investigate the potential aetiological role of several pathogens in 47 cows with 73 ITN lesions from 28 farms. ITN lesions were allocated to one of three broad macroscopic categories: presence of a non-proliferative lesion on the teat (type 1); proliferative teat lesion with crusting (type 2); severe purulent to eosinophilic, ulcerative and necrotising dermatitis and sloughing or total absence of the teat (type 3). Lesions were mostly observed on the medial aspect of the teat but there was no anatomical predisposition as to which teats were more frequently affected. In approximately 50% of the ITN teats reviewed, the lesions were continuous with the skin of the udder and 34.2% of cases had sloughed or partially sloughed teats. The main histological findings were: focally extensive severe purulent to eosinophilic, ulcerative and necrotizing dermatitis; serocellular crust formation; and epidermal hyperplasia with dyskeratosis. Some lesions also had leucocytoclastic to eosinophilic vasculitis and thrombosis with ischaemic necrosis. Macroscopic and histological analyses confirmed the suspected ischaemic nature of the lesions but the specific aetiopathogenesis was elusive with a wide range of bacteria present, probably as opportunistic infections. However, Treponema spp and Orthopox virus were excluded as major aetiological agents. This study establishes a foundation for further investigations of the pathogenesis of bovine ITN and a basis for consistency in diagnosis and classification of the stage of disease. The findings are also key to further understanding disease progression and prognosis.
Skin biopsy for histologic, immunofluorescent, parasitologic, and bacteriologic examination is a common procedure, but for maximum effectiveness the clinician must realize the importance of precautions to select the correct stage of lesion of different diseases; avoiding creating artifacts during removal and fixation; and give full details of history, clinical diagnosis, and differential diagnoses on the laboratory request sheet. Pathology reports describing the subtleties of histologic changes are difficult to write, particularly if the lesions are not specific. Overly long histologic reports without a definitive diagnosis may frustrate a clinician who is unfamiliar with the significance of histologic lesions. For these reasons, clinician and pathologist must develop a rapport and empathy for the other's difficulties and adequately communicate to allow each to make a maximum contribution toward the final diagnosis. Histopathologic examination of skin lesions may not produce a specific diagnosis but is frequently useful in the elimination of other suspected diagnoses.
Mastitis control is a continuing process that should be applied to all herds without relaxation. Programs likely to achieve widespread adoption must emphasize control of all pathogens rather than eradication of specific pathogens. Although none of the methods available at this time provide complete protection, the devastating losses from mastitis can be minimized with current technology in the vast majority of dairy herds. A control method similar to the Five-Point Program of Mastitis Control just discussed has the greatest utility. The program is not dependent upon examination by specialists, can be applied to any herd, is effective against common pathogens, results in a profit of $3 to $5 for each dollar invested, reduces clinical mastitis, and is flexible to permit refinement as additional knowledge becomes available. Failure of the Five-Point Plan of Mastitis Control in a small number of herds that seemingly are well managed is often due to failure of the farmer to apply the methods properly. In some instances, the farmer may perceive that he is following the full control program when, in reality, he is following only a part of the program. Overlapping and complementary components are of greatest value. Control methods that aim at a particular organism are highly dependent upon advisory personnel and supporting laboratories and have little chance of reaching a majority of dairy herds. Not only will the conscientious application of the Five-Point Program of Mastitis Control return 300 to 500 per cent on investment, but the quality of milk ultimately reaching the consuming public will be improved and the dairy farmer will, in effect, be helping to protect his present and future market. Herds with a high level of infection obviously stand to realize greater increase in profits from initiating a mastitis control program. This is because herds with a low level are already reaping the benefits. Nevertheless, implementing or continuing an effective mastitis control program is a wise and prudent decision for all dairy farmers.
The environment provided for dairy cows should be designed and maintained so that cow comfort and sanitation are maximized and disease exposure is minimized. Too often, housing facilities are designed for the dairyman rather than for the cow. This factor can result in reduced cow comfort, which, in turn, leads to reduced performance. As stated previously, the environment should be designed to "keep them clean, dry, and comfortable."
