The udders of does are infected by organisms similar to those that cause mastitis in cows. Nonaureus staphylococci (previously termed coagulase-negative staphylococci) are generally the most prevalent in does and can cause persistent infections that result in increased somatic cell counts (SCCs) and low-grade mastitis with some recurring clinical episodes. The level of infection and incidence of mastitis due to Staphylococcus aureus tends to be low (< 5%) but can result in persistent infections that do not generally respond to treatment.
Streptococcal intramammary infections can occur in both subclinical and clinical cases but are usually much less frequent than in cattle. Streptococcus agalactiae is not a common mastitis pathogen in does.
Mycoplasma infections, primarily Mycoplasma mycoides (large-colony type) and Mycoplasma putrefaciens, sometimes cause serious outbreaks of mastitis in goats. M putrefaciens also causes septicemia, polyarthritis, pneumonia, and encephalitis, together with serious disease and mortality in suckling kids. Mycoplasma capricolum has also been reported to cause severe mastitis in goats and infection in kids. Does usually recover in approximately 4 weeks.
As with cows, gram-negative organisms cause intermittent infections that may be severe but are usually self-limiting. Trueperella (formerly Arcanobacterium) pyogenes sometimes produces multiple nodular abscesses.
Does can also exhibit clinical signs of mastitis from caprine arthritis and encephalitis and ovine progressive pneumonia secondary to systemic infection. Agalactia is common, as is a hardening of the udder from fibrosis.
Programs for diagnosis, control, and treatment of bacterial mastitis in does are similar to those in cows. However, monitoring subclinical mastitis with SCCs in does is difficult because of poor discrimination between infected and noninfected animals, especially in the later stages of lactation. This is partially because a of a higher proportion of epithelial cells in caprine milk than in bovine milk. As lactation progresses, shedding of epithelial cells into milk increases; thus, SCCs > 1,000,000 cells/mL are common in uninfected does in late lactation.
Pearls & Pitfalls
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Proper milking procedures and good environmental sanitation are needed to decrease the prevalence and spread of infection. Chronically infected does should be culled, as should does with M mycoides infections and those that do not recover from M putrefaciens or M capricolum infections.
