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MASTITIS by Terry C. Gerros, DVM,MS,DACVIM

By definition, mastitis is an inflammatory condition of the mammary gland, based on the changes in the physical characteristics of the udder or milk. Mastitis, usually caused by a bacteria or virus, is a common reason for culling a doe. Several factors which may increase in incidence of mastitis include failure to keep bedding clean, bruising from nursing kids, and trauma to the udder or teats.

The most economically important organism associated with caprine mastitis is the bacteria Staphylococcus aureus. Other bacterial causes include Escherichia coli, Actinomyces pyogenes, and Corynebacterium pseudotuberculosis. Caprine Arthritis Encephalitis Virus (CAEV) has been implicated in a condition known as Hard Udder.

Early signs of mastitis include decrease in milk production, lameness, or identified through kids appearing hungry or increase loss of kids. The udder is usually misshapen and may be either swollen (indicating acute infection) or withered (indicating chronic infection). In acute mastitis you may notice a hot, reddened, swollen udder which is painful to the touch. Chronically affected udders may be firm or withered without evidence of pain. Abscess formation may be evident. The doe may show signs of generalized illness: depression, fever or loss of appetite. Gangrene mastitis should be suspect if the udder is cold, edematous and the milk is watery or bloody.

Diagnosis is based upon the clinical signs as described, bacterial culture results of the milk and somatic cell count (SCC). Interpretation of SCC should be made with care. In the dairy cow, the SCC is directly correlated to the severity of the mastitis. Somatic cell counts are higher in goats then cattle because of the normally higher cytoplasmic particles and epithelial cells present in the milk.

Staphyloccocus Aureus Mastitis

Several syndromes are associated with this bacteria: Subclinical, acute, chronic and gangrenous. In the subclinical form here are no clinical signs of disease other then increased SCC in the milk and identification by culture found during herd surveys. With the acute syndrome, you would expect to see a hot, swollen udder which is painful to the touch. The doe may systematically ill (fever, depression, off feed). Chronic staph infections are characterized by decreased production, a firm udder and abscess formation. Gangrenous (blue bag) mastitis is most commonly found in does which lack adequate antitoxins against one of the toxins produced by this organism. It is the toxin that is responsible for the tissue destruction of the mammary gland. Early in the course of the disease the doe is often off feed, feverish and lame. The skin of the udder becomes cool to touch, is swollen and reddened. This is followed by bluish discoloration of the udder which develops a watery or bloody discharge. Gas may be detected when milking out the doe. Death generally ensues within 24 hours. If the doe survives the acute phase, a clear line demarcating healthy skin from diseased tissue develops, the sloughing of that portion of the affected udder. Treatment involves supportive care with intravenous fluids, nonsteroidal anti-inflamatory drugs, and antibiotics. Udder amputation is recommended.

Staph mastitis is difficult if not impossible to clear up because the organism forms microabscesses. It is sometimes difficult to identify because of intermittent shedding, thus one negative culture does not mean absence of infection. Transmission occurs during milking, thus affected does should be milked last or culled. If the doe is treated, only after multiple cultures and low SCC should you consider resolution off the problem.

Hard Udder (CAE)

Because of the way the virus affects the mammary gland, this condition is more commonly seen about the time of kidding. In the acute form, the udder is firm, but exhibits no edemal or milk production. There is no heat, redness or systemic illness seen with this syndrome. The diagnosis is based upon histologic changes, ruling out other causes, ruling out udder edema and teat obstruction and either CAE titers or virus isolation. There is no treatment or cure for this condition and the does should be culled.

Approach/Prevention of Bacterial mastitis:

Antibiotic use should be based on identification of the causative agent, which is identified by culture. Antibiotic residue is a concern for public health and may affect the decision to treat the animal. Labeled withdrawal times are listed for cattle and extrapolating to goats suggest that withdrawal times be doubled for the doe. Both injectable antibiotics and intramammary infusions should be considered. Whether the animal is treated or culled is based upon economic factors, emotional ties and pedigree of the animal.

Teat dipping reduces the incidence of mastitis. Products which have been tested include 0.5% iodine (betadine) and 0.5% chlorhexidine.

You should avoid prolong storage of these products and avoid letting them freeze as they affect the products ability to kill bacteria.

Prolonged storage results in evaporation, increasing the concentration of the solution which may end up being irritating to the teats. Storage also increases the chances of product degradation. Pseudomonas spp. and Serratia spp. are two bacteria which can grow in the products listed.

Thus it is imperative that the products not be contaminated with organic material (i.e. feces). Ideally, use of hand pumps and aerosols are the most sanitary way to apply teat dips.

Culling the individual has some definite advantages and should be considered. The advantages include:

  • Decrease exposure of the other does.
  • Increase selection pressure for genetic resistance
  • Eliminates labor costs of treatment. It is estimated that greater the 50% of mammary gland infections persist through the dry period into the next lactation. Treatment during this period improves the cure rate. Most cattle "dry cow" preperations are suitable for use in dairy goats.

Prevention of Mastitis:
Simply put, the following guidelines are recommended:

  • Select for improved udder attachment.
  • Improve sanitation
  • Use proper milk procedures
  • Dry period treatment.

If you suspect your doe has mastitis, you should contact your local veterinarian to help identify the organism and formulate a treatment plan.