Brief Informational Sketches of Some Other Mastitis Pathogens

Kansas State University College of Veterinary Medicine
Mississippi State University College of Veterinary Medicine
Virginia-Maryland Regional College of Veterinary Medicine
Texas A & M University College of Veterinary Medicine.

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Mastitis Pathogen Information: Coliform Pathogens

Introduction: The coliform bacteria are a group of gram-negative opportunistic pathogens shed in the feces of healthy animals. This group includes Escherichia coli, Klebsiella species, and Enterobacter aerogenes.

Epidemiology / Clinical Particulars:

Coliform bacteria are found worldwide in the environment, especially in areas where cattle are housed instead of pastured or the weather is wet. Mastitis due to coliform bacteria is uncommon in pastured cattle. Coliform mastitis is most common in well-managed herds where contagious pathogens have been controlled and Somatic Cell Counts are low. The incidence of coliform mastitis has traditionally been thought to be highest in the dry period and early lactation. The use of gram-negative core antigen vaccines may have changed the incidence pattern somewhat; by providing protection against coliform infection in the dry period and early lactation, incidence rates have been decreased somewhat during these periods in herds that vaccinate. Older cows are at increased risk for coliform mastitis, as are cows with low levels of Selenium or Vitamin E, trauma to the teats, or concurrent disease such as parturient paresis or ketosis.

Coliform mastitis is rarely subclinical. The clinical syndrome may be peracute, acute, or chronic.

Clinical signs of peracute coliform mastitis are caused by the endotoxin produced by coliform bacteria. Clinical signs resulting from toxemia include fever, shivering, recumbency, diarrhea, depression, dehydration and cool extremities. Milk is abnormal, but on initial presentation udder swelling may not be significant. Some cows become bacteremic. Prognosis is poor. Cows with this syndrome are commonly hypocalcemic, and if the hypocalcemia is not addressed in therapy, cows that survive the toxic insult may nevertheless become “downers”. Cows that recover may become agalactic or have decreased production for the remainder of the lactation. Klebsiella in particular may cause an extended period of convalescence with anorexia and depression following the onset of mastitis.

Acute coliform mastitis is a typical mastitis syndrome, featuring inflammation of the mammary gland and abnormal milk, sometimes accompanied by mild systemic signs such as fever or anorexia.

Chronic coliform mastitis causes repeated episodes of mild clinical mastitis with abnormal milk and mild inflammation of the mammary gland.

Diagnosis: Milk culture using standard methods is an effective way of diagnosing coliform mastitis. However, it is not uncommon, particularly in subacute cases, for the cow's own immune system to have resolved the infection by the time a culture is taken, even though signs of inflammation remain. In these cases, though the clinical signs are a result of coliform infection, bacterial culture results will be negative.

Specifics of therapy and control:

Peracute coliform mastitis is a veterinary emergency. Therapy must be directed at treating the effects of endotoxin as well as eliminating the pathogen, and it must be kept in mind that prognosis is generally poor in severe cases, regardless of therapy. Points to be considered, in addition to choice of antimicrobial, include:

a) Fluid therapy is indicated to rehydrate the cow and counteract circulatory collapse due to endotoxic shock. Therapy may consist of high volume intravenous isotonic fluids or, if facilities are unavailable for such therapy, intravenous hypertonic saline and oral fluids may be used. It is important that fluids administered be of sufficient volume. If intravenous fluids are used, 10 to 20 Liters should be administered in the first few hours and a total of 40 to 60 liters should be given over the first 24 hours. Oral fluids given in conjunction with intravenous hypertonic saline solution should be 10 or more gallons (for a typical size Holstein), repeated if necessary.

b) Anti-inflammatory drugs from either the NSAID or steroid class are commonly used to counteract the effects of bacterial endotoxin. Research efforts have not yet revealed the optimal drug or dose for such use. Use of this class of drugs is currently recommended, however, as studies have not demonstrated decreased survival with their use and humane concerns would recommend them.

c) Cows with endotoxic mastitis are generally hypocalcemic and should be given calcium.

d) Frequent milkout or stripping has traditionally been recommended for coliform mastitis, but recent research (Roberson 1997) has suggested that it may not be beneficial.

Methods for controlling coliform mastitis focus on maintaining a clean, dry environment in which coliform numbers will be minimized. Coliform bacteria are also present in organic bedding materials such as sawdust and straw, and using sand as bedding instead will decrease cow exposure to coliform pathogens. Predipping and milking clean, dry teats are also important measures for reducing the incidence of coliform mastitis.

Core antigen vaccines have helped in the control of mastitis due to coliform bacteria. They provide protection against all gram-negative pathogens. Core antigen vaccines reduce the incidence of clinical mastitis, and the cases that do occur in vaccinated herds are generally later in lactation and reduced in severity.